Ram Concept

RAM Concept  Release 5.0 August 2012

RAM International 2744 Loker Avenue West Carlsbad, CA 92010 Telephone: (760) 431-3610 Toll Free: (800) 726-7789 Fax: (760) 431-5214

DAA037480-1/0001

DISCLAIMER The software and related documentation, including this documentation, are protected by both United States copyright law and international treaty provisions. Any unauthorized copying or reproduction is strictly prohibited and subject to civil and criminal penalties. Please refer to the License Agreement for authorization to make a backup copy of the software. You may not sell this software or documentation or give copies of them away to anyone else. Except as expressly warranted in the License Agreement, RAM International disclaims all warranties, expressed or implied, including but not limited to implied warranties of merchantability and fitness for a particular purpose, with respect to the software, the accompanying written materials, and any accompanying hardware. All results should be verified to the user's satisfaction. The contents of these written materials may include technical inaccuracies or typographical errors and may be revised without prior notice.

Copyright attribution: © 2012, Bentley Systems, Incorporated. All rights reserved. Trademark attribution: RAM Concept and RAM Structural System are either registered or unregistered trademarks or service marks of Bentley Systems, Incorporated or one of its direct or indirect wholly-owned subsidiaries. Other brands and product names are trademarks of their respective owners.

DAA037480-1/0001

RAM Concept Table of Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 1.2 1.3 1.4 1.5 1.6

Comparing with “traditional” methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 RAM Concept options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Strip Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Structural systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Learning RAM Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Technical support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Looking at the Workspace 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

About the workspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Creating and opening files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Saving a file . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 About templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Expanding tool buttons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Rearranging toolbars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Using the right mouse button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Undoing changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Understanding Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 Modeling with objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2 Managing layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4 Using Plans and Perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1 4.2 4.3 4.4 4.5 4.6

Using plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Creating new plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Viewing perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Creating new perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Controlling views . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Setting up the grid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5 Drawing and Editing Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.1 Precision drawing with snaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.2 Drawing objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.3 Entering coordinate points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.4 Using relative coordinates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.5 Selecting objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.6 Deselecting objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.7 Filtering selected objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.8 Cutting, copying, and pasting objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.9 Copying and pasting objects by layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.10 Editing polygon objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.11 Moving, rotating, stretching, and mirroring objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5.12 Using the Utility tool to move and stretch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.13 Manipulating the model as a whole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.14 Editing object properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 5.15 Setting default properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5.16 Adding reference lines, dimensions, and text notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

6 Viewing Objects in Text Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.1 Customizing tables

7 Choosing Units

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7.1 About units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7.2 Selecting units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 7.3 Specifying report as zero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 RAM Concept

i

8 Choosing Sign Convention

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8.1 Selecting sign convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 8.2 About plot sign convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9 Specifying Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 9.1 9.2 9.3 9.4

Viewing the available materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Material properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Adding and deleting materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 About post-tensioning systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

10 Specifying Loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 10.1 10.2 10.3 10.4 10.5 10.6 10.7 10.8 10.9

About default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Viewing the loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Loading properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 About loading types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Available loading types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Changing Loading Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Changing Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Adding and deleting loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 About load pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

11 Specifying Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.8

About default load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Viewing the load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Rebuilding load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Adding and deleting load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Load combination properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 About group load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 About alternate envelope factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Summary of load combination types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

12 Selecting Design Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 12.1 12.2 12.3 12.4

Using rule set designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Rule set design properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Types of active rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Adding and deleting rule set designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

13 Using a CAD Drawing

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

13.1 Importing, verifying and viewing a drawing

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

14 Importing a Database from the RAM Structural System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 14.1 14.2 14.3 14.4 14.5 14.6 14.7

What can be imported from the RAM Structural System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Controlling which concrete members are imported . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 About load importation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 Importing a database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 Reimporting a database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 Limitations, Defaults and Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 Tight integration with the RAM Structural System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

15 Data Transfer from STAAD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 15.1 STAAD Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 15.2 RAM Concept Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

16 Data Transfer from ISM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 16.1 What is ISM? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 16.2 ISM Sync Tools Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 16.3 Import and Export Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

17 Defining the Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 17.1 Using the Mesh Input Layer ii

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

RAM Concept

17.2 About columns and walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 17.3 Column properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 17.4 Drawing columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 17.5 Wall properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 17.6 Drawing walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 17.7 About point and line supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 17.8 Point support properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 17.9 Drawing point supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 17.10 Line support properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 17.11 Drawing line supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 17.12 About springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 17.13 Point spring properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 17.14 Drawing point springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 17.15 Line spring properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 17.16 Drawing line springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 17.17 Area spring properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 17.18 Drawing area springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 17.19 About floor areas and members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 17.20 Slab area properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 17.21 Drawing slab areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 17.22 About beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 17.23 Beam properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 17.24 Drawing beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 17.25 Slab opening properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 17.26 Drawing slab openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 17.27 Checking the structure definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

18 Generating the Mesh

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

18.1 Generating the mesh automatically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 18.2 Selectively refining the mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

19 Manually Drawing the Finite Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 19.1 Using the Element layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 19.2 About column elements and wall elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 19.3 Column element properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 19.4 Drawing column elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 19.5 Wall element properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 19.6 Drawing wall elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 19.7 About point and line supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 19.8 Point support properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 19.9 Drawing point supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 19.10 Line support properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 19.11 Drawing line supports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 19.12 About springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 19.13 Point spring properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 19.14 Drawing point springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 19.15 Line spring properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 19.16 Drawing line springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 19.17 Area spring properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 19.18 Drawing area springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 19.19 About floor areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 19.20 Slab element properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 19.21 Drawing the slab elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 19.22 A few final words . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

20 Drawing Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 20.1 20.2 20.3 20.4 20.5 20.6

About self-weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 About superposition of loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Point load properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Drawing point loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Line load properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Drawing line loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

RAM Concept

iii

20.7 Area load properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 20.8 Drawing area loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 20.9 Copying loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

21 Creating Pattern Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 21.1 Deciding how many load patterns to use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 21.2 Drawing load patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 21.3 Load pattern filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

22 Defining Design Strips

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

22.1 Definition of a design strip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 22.2 Design strip terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 22.3 Understanding how a design strip works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 22.4 The design strip process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 22.5 Span segment properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 22.6 Creating span segments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 22.7 Creating span segment strips (design strips) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 22.8 Defining span segment widths and strip widths manually . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 22.9 Cross Section Trimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 22.10 Improving the mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 22.11 Additional design strip information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 22.12 Irregular column layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 22.13 Miscellaneous tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 22.14 A final word on design strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

23 Defining Design Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 23.1 23.2 23.3 23.4 23.5

Using design sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Design section properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Drawing design sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 About ignore depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 A final word on design sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

24 Defining Punching Shear Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 24.1 24.2 24.3 24.4

About punching shear checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Punching shear check properties and options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 Drawing punching shear checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 A final word on punching shear checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

25 Drawing Reinforcement Bars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 25.1 Reinforcement bar definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 25.2 Reinforcement properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 25.3 About drawing reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 25.4 Drawing concentrated reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 25.5 Drawing distributed reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 25.6 Concentrated and distributed reinforcement drawing examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 25.7 Other reinforcement plan tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 25.8 Layout and Detailing Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 25.9 Reinforcement Text Formatting: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 25.10 About SSR callouts and SSR rails: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

26 Defining Tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 26.1 Tendon definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 26.2 Tendon Parameters Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 26.3 Tendon properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 26.4 About creating tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 26.5 Drawing banded tendon polylines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137 26.6 Drawing distributed tendon quadrilaterals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 26.7 Defining profiles for banded tendon polylines and distributed tendon quadrilaterals . . . . . . . . . . . . . . . . . . . . 138 26.8 Other tendon parameter plan objects and tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 26.9 Tendon parameter drawing examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 26.10 Tendon parameter drawing and text formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 iv

RAM Concept

26.11 26.12 26.13 26.14 26.15 26.16 26.17

About drawing individual tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Drawing single tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141 Drawing multiple tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 Editing tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 About jacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 Jack properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 Drawing the jacks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

27 Using Live Load Reduction 27.1 27.2 27.3 27.4 27.5 27.6 27.7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147

About Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Live Load Reduction Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Setting the Live Load Reduction Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Live Loading Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 Live Load Reduction Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 Specifying Live Load Reduction Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 Implementation of Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

28 Calculating Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 28.1 28.2 28.3 28.4 28.5 28.6 28.7

Calculating the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 About analysis errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Recalculating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Calculating load history deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Calculating vibration analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Reviewing the calc log . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153 Decreasing calculation time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

29 Viewing the Results 29.1 29.2 29.3 29.4 29.5

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

Type of results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Viewing frequently used results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 Viewing other results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Section distribution plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Miscellaneous results information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

30 Plotting Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 30.1 Setting the plotted results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 30.2 Slab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 30.3 Reaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 30.4 Strip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 30.5 Section Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 30.6 Section Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 30.7 Punching Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 30.8 Vibration Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 30.9 Plot Animation Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 30.10 Difference Plot Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

31 Using the Auditor 31.1 31.2 31.3 31.4 31.5 31.6 31.7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

How the Auditor can assist the design process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 About the three design steps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 About the information displayed by the Auditor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Using the Auditor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174 Using the Auditor for guidance on post-tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 About the information displayed by the Punching Check Auditor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 Using the Punching Check Auditor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

32 Using the Report Viewer 32.1 32.2 32.3 32.4

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Using the Report Viewer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Saving Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Opening Previously Saved Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 Printing Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

RAM Concept

v

33 Using the Estimate 33.1 33.2 33.3 33.4

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Viewing the estimate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 What the estimate calculates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 Editing the unit costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179 About unit costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

34 Printing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 34.1 34.2 34.3 34.4 34.5 34.6 34.7 34.8

Basic printing instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 General printing options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 Select and Configure Printer options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 Determining the fit of plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 Printing the desired perspective viewpoint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 Previewing the print job . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Printing optimizations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Changing the report contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184

35 Exporting Plans and Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 35.1 Exporting a plan 35.2 Exporting a table

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187

36 Exporting a Database to the RAM Structural System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 36.1 About the export of reactions 36.2 About the export of geometry

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

37 Using Strip Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 37.1 Starting Strip Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 37.2 Specifying general parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 37.3 Entering span data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193 37.4 Entering support data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 37.5 Adding drop caps and drop panels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 37.6 Entering the loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 37.7 Specifying the post-tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 37.8 Specifying reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 37.9 Completing Strip Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 37.10 Generating the mesh and calculating results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 37.11 Loading and saving Strip Wizard settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197

38 General Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 38.1 38.2 38.3 38.4

Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Restraint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

39 Frequently Asked Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 39.1 Capabilities and Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 39.2 Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 39.3 Plans and perspectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204 39.4 Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 39.5 Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 39.6 Sign Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 39.7 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 39.8 Tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 39.9 Loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 39.10 Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 39.11 Design Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 39.12 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211 39.13 Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

40 Errors and Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 40.1 Meshing

vi

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

RAM Concept

40.2 40.3 40.4 40.5

Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 Tendons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 Load History Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

41 Simple RC Slab Tutorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 41.1 41.2 41.3 41.4 41.5 41.6

Defining the structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 Drawing the loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Defining the design strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226 Drawing punching shear checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 Calculate and view the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228 Drawing reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236

42 PT Flat Plate Tutorial: ACI 318-08 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 42.1 42.2 42.3 42.4 42.5 42.6 42.7

Import the CAD drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Define the structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Define the loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242 Define the post-tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 Create the design strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Regenerate the mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 Calculate and view the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

43 PT Flat Plate Tutorial: AS3600-2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259 43.1 43.2 43.3 43.4 43.5 43.6 43.7


44 PT Flat Plate Tutorial: BS8110 / TR43 44.1 44.2 44.3 44.4 44.5 44.6 44.7

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279


45 PT Flat Plate Tutorial: EC2 / TR43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299 45.1 45.2 45.3 45.4 45.5 45.6 45.7


46 PT Flat Plate Tutorial: IS 456 : 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319 46.1 46.2 46.3 46.4 46.5 46.6 46.7


47 PT Flat Plate Tutorial: CSA A23.3-04 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 47.1 Import the CAD drawing

RAM Concept

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

vii

47.2 47.3 47.4 47.5 47.6 47.7

Define the structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 Define the loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 Define the post-tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 Create the design strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349 Regenerate the mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352 Calculate and view the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

48 Mat Foundation Tutorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 48.1 48.2 48.3 48.4 48.5 48.6

Import the CAD drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 Define the structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359 Define the loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 Create the design strips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 Regenerate the mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Calculate and view the results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368

49 Strip Wizard Tutorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 49.1 Start Strip Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 49.2 Set the general parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 49.3 Enter the span data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 49.4 Create the supports below . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 49.5 Add drop caps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 49.6 Specify the loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 49.7 Define the post-tensioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 49.8 Specify the reinforcement parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 49.9 Complete the Strip Wizard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 372 49.10 Proceed with RAM Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 49.11 Comparison with PT Flat Plate Tutorial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 49.12 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373

50 Analysis Notes 50.1 50.2 50.3 50.4 50.5 50.6 50.7 50.8 50.9

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375

Review of plate behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 Finite element analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 Orthotropic behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 Deep beam considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 Wall behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385 Post-tensioning loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 386 Self-equilibrium analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387 Design strip and design section forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 Result categories in RAM Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391

51 Section Design Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 51.1 General Design Approach

52 Live Load Reduction Notes

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407

52.1 Live Load Reduction for Loadings, Load Combinations and Rule Sets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 52.2 Tributary Area Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 52.3 Influence Area Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 408 52.4 ASCE-7 2002 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 52.5 ASCE-7 2010 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 52.6 IBC 2003 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 52.7 IBC 2006 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 52.8 IBC 2009 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 52.9 UBC 1997 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 52.10 AS/NZS 1170.1-2002 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 52.11 BS 6399-1:1996 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412 52.12 IS 875 (Part 2) - 1987 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 52.13 Eurocode 1-2002 (UK Annex) Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 52.14 National Building Code of Canada 2005 Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 52.15 Mat Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413 52.16 Special Member Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414

viii

RAM Concept

53 Reinforcement Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 53.1 53.2 53.3 53.4 53.5 53.6

Span detailing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415 Development lengths / anchorage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 417 How RAM Concept lays out program reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421 How Concept details user and program reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422 How Concept treats transverse reinforcement and individual transverse bars . . . . . . . . . . . . . . . . . . . . . . . . . . 423 Example 1: reinforcement results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423

54 ACI 318-99 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 54.1 54.2 54.3 54.4 54.5 54.6

ACI 318-99 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 ACI 318-99 default load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 427 ACI318-99 / ASCE-7 / IBC 2003 live load factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 ACI 318-99 material behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431 ACI 318-99 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433 ACI 318-99 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 435

55 ACI 318-02 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443 55.1 55.2 55.3 55.4 55.5 55.6


56 ACI 318-05 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 463 56.1 56.2 56.3 56.4 56.5 56.6


57 ACI 318-08 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 483 57.1 57.2 57.3 57.4 57.5 57.6


58 ACI 318-11 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 58.1 58.2 58.3 58.4 58.5 58.6

ACI 318-11 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 ACI 318-11 default load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 503 ACI318-11 / ASCE-7 / live load factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 ACI 318-11 material behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 510 ACI 318-11 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 511 ACI 318-11 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514

59 AS 3600-2001 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 59.1 59.2 59.3 59.4 59.5 59.6

AS 3600-2001 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 AS 3600-2001 default load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523 AS3600 / AS/NZS 1170.1 live load factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527 AS 3600-2001 material behaviours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527 AS 3600-2001 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 528 AS 3600-2001 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 531

60 AS 3600-2009 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 60.1 AS 3600-2009 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 60.2 AS 3600-2009 default load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 539 60.3 AS3600 / AS/NZS 1170.1 live load factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543

RAM Concept

ix

60.4 AS 3600-2009 material behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543 60.5 AS 3600-2009 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544 60.6 AS 3600-2009 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 547

61 BS 8110: 1997 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 61.1 61.2 61.3 61.4 61.5 61.6

BS 8110 / TR 43 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 BS 8110 / TR 43 Default Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555 BS 8110 / BS 6399-1 live load factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558 BS 8110/TR43 material behaviours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 558 BS 8110 / TR 43 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 561 BS8110 / TR43 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565

62 IS 456 : 2000 / IS 1343 : 1980 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 62.1 62.2 62.3 62.4 62.5 62.6 62.7

IS 456 / IS 1343 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 IS 456 Default Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 577 IS 875 (Part 2) live load factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580 IS 456 material behaviours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 IS 456 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584 IS 456 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 588 IS 1343 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 592

63 EN 1992-1-1:2004 (Eurocode 2) With TR43 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 63.1 63.2 63.3 63.4 63.5 63.6

EC2 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 EC2 Default Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598 Eurocode 1 Part 1-1 (UK National Annex) Live Load Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 EC2 Material behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605 EC2 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607 EC2 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 613

64 CSA A23.3-04 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 64.1 64.2 64.3 64.4 64.5 64.6

CSA A23.3-04 default loadings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 CSA A23.3-04 default load combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623 CSA A23.3-04/NBC 2005 live load factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628 CSA A23.3-04 material behaviors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 628 CSA A23.3-04 code rule selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 629 CSA A23.3-04 code implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 633

65 Load History Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641 65.1 65.2 65.3 65.4 65.5 65.6 65.7

About RAM Concept’s load history deflection calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 641 The load history deflection calculation process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 642 Load history calculations on the cross section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 643 Element stiffness adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 644 Why are load history deflection results different from Long Term Deflection results plotted for the strip? 645 Advice on drawing cross sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645 A final word of caution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 645

66 Punching Shear Design Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647 66.1 Punching shear overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647 66.2 How does RAM Concept handle punching shear? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 647 66.3 Using Concept's results to specify stud shear reinforcement (SSR) systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 66.4 Column connection type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 66.5 ACI 318/CSA A23.3 Punching Shear Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651 66.6 AS 3600-2001 Punching Shear Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 656 66.7 EN 1992-2004 Punching Shear Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 659 66.8 Sign convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 663 66.9 Advice on the selection of punching check properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 664 66.10 Miscellaneous information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665 66.11 Some final words of advice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 665

x

RAM Concept

67 Vibration Analysis Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667 67.1 67.2 67.3 67.4

Dynamic Characteristics of Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 667 Resonant Footfall Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 668 Impulsive Footfall Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671 Evaluating Vibration Performance and Interpreting Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 671

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RAM Concept

Chapter 1

1 Introduction RAM Concept is an analysis and design program that uses the finite element method for elevated concrete floor systems, or mat foundations. The floors or mats can be post-tensioned concrete (PT), reinforced concrete (RC), or hybrid (a mixture of PT and RC). Concept is extremely powerful and allows you to design an entire floor in one model, or design individual strips or beams. In this context, the term “design” means that: • The user defines the following: structural geometry, loads, load combinations, and post-tensioning layout (if applicable). • Concept calculates (for any number of load combinations): the required amount of reinforcement for flexure and one-way shear according to relevant code requirements; the stud shear reinforcement (SSR) for punching shear, stresses for flexure, and deflections. A model consists of anything from a single simply supported beam or slab to an entire floor. All models are three-dimensional (even those developed with Strip Wizard). Concept does not generally use strip methods other than to replicate the intent of concrete code rules, and with the Strip Wizard interface.

Note: The Equivalent Frame method is not used.

1.1 Comparing with “traditional” methods Historically, the vast majority of concrete floors have been analyzed by approximating a region of a slab as a frame (or design strip), and then analyzing the frame/strip using variations of conventional frame or moment distribution analysis techniques. There are two limitations to this approach. First, in irregular structures, the approximation of the real structure into a frame model could be grossly inaccurate and designing with the analysis results might not even satisfy equilibrium requirements in the real structure. The second limitation is that even in regular structures with regular loadings, the frame analysis approximates the slab/column interaction and provides no information regarding the distribution of forces across the design strip. RAM Concept enables you to design post-tensioned and reinforced concrete slabs by using a finite element model of the entire slab. Concept can predict the elastic behavior of a slab much more accurately than frame models. In addition, the finite element method guarantees that the analysis satisfies all equilibrium requirements, regardless of a structure’s irregularities.

RAM Concept

1.2 RAM Concept options RAM Concept is available in the core configuration which is suitable for the analysis and design of reinforced concrete mat foundations (rafts) of any size and shape as well as reinforced concrete floor systems of any size and shape. Increase RAM Concept’s analysis and design capabilities by adding the Post-tension option: • RAM Concept PT option (post-tensioned option) Analysis and design of post-tensioned floors or mats in conjunction with reinforced concrete.

1.3 Strip Wizard Strip Wizard uses text input to generate a model. This allows the designer to perform quick preliminary design in 2-D, or final design of straightforward structures. Strips generated by Strip Wizard are three-dimensional, but boundary conditions are automatically introduced which effectively model 2-D behavior. All models use the finite element method. You can use Strip Wizard to design a beam or one-way slab without many mouse clicks. It can provide an initial design of tendons and profiles, negating the need for the designer to start with a guess.

1.4 Structural systems You can use RAM Concept for models that contain any combination of the following: • one-way slab systems • two-way slab systems • beams • girders • “wide shallow” beams (that behave similarly to slabs) • ribs (joists) • waffles (two-way rib systems) • mats (rafts) • openings There may be steps and changes in thickness and elevations for all of these items. 1

Chapter 1 Concept is not effective, or you cannot use it directly, for the following: • deep beams using the strut and tie method • I-shaped sections • ramps • concrete sections with internal voids or cells In most cases, you could model ramps with a large number of steps. The authors do not recommend that you do this for evaluating post-tensioning behavior, as it is not particularly relevant.

modeling and many of the tools. The descriptions are not exhaustive, and you should reference the actual tool description in the appropriate chapter for further information. This should prove useful for real projects. It is recommended that you redo the tutorials. The completed tutorial files are available from the program directory, so you don’t have to start from scratch. For example, you could open the ACI 318-02 PT Tutorial, delete the design strips, and then start with the design strips input.

1.5.2 Critical Chapters

1.5 Learning RAM Concept The RAM Concept design process could be considered to comprise 5 stages:

We consider that you should at least read the following chapters, together with the tips in this chapter before starting your first design. • Chapter 1, “Introduction”. • Chapter 2, “Looking at the Workspace”. • Chapter 3, “Understanding Layers”.

• Defining the concrete form (**)

• Chapter 4, “Using Plans and Perspectives”

• Drawing loads (*)

• Chapter 5, “Drawing and Editing Objects”

• Defining design strips (*****)

Note: Chapter 5 describes snapping. Nearly all meshing

• Defining tendons (if used) (***)

problems are due to the user’s failure to use snapping properly.

• Interpreting results (****) The (**) rating is meant to indicate relative degree of difficulty, or relative time you would expect to spend on the stage. You should not use Concept for final design without a sufficient grounding in concrete design, or adequate understanding of the program. The manual contains a large amount of information.Ideally, you should read it all, but this may not be practical. We recommend that you do the tutorials and read critical chapters.

• Chapter 17, “Defining the Structure” • Chapter 22, “Defining Design Strips”. • Chapter 38, “General Tips” • Chapter 39, “Frequently Asked Questions” • Chapter 40, “Errors and Warnings” • Chapter 65, “Load History Deflections”. • The appropriate code chapter. See the section below: “Know your building code”.

1.5.3 Know your building code 1.5.1 Tutorials We recommend that you start by doing the tutorials: • Chapter 41, “Simple RC Slab Tutorial”. • One of the following PT Tutorial Chapters: 42, 43, 44,45 46, or 46.

Note: Even if you do not have access to the PT version, it is advisable to do one of these tutorials as a thicker RC slab. • For Mat (Raft Users): Chapter 48, “Mat Foundation Tutorial”. The tutorials introduce you to the “philosophy” of the program. They quickly give you experience in some basic

2

RAM Concept does not replace the code. It implements some, but not all, of the code. Using the program does not absolve you of knowing your building code. You should review the appropriate code chapter: • Chapter 58, “ACI 318-11 Design” • Chapter 60, “AS 3600-2009 Design” • Chapter 61, “BS 8110: 1997 Design” • Chapter 62, “IS 456 : 2000 / IS 1343 : 1980 Design” • Chapter 63, “EN 1992-1-1:2004 (Eurocode 2) With TR43 Design ” • Chapter 64, “CSA A23.3-04 Design”

RAM Concept

Chapter 1 These chapters discuss the following code specific issues: • default loadings • default load combinations • live load reduction • assumptions on material behavior • rule selection • rule implementation

1.5.4 Upgrading Old Files Recommendations for Old Files

We do not recommend that you upgrade old files that contain models that have been fully designed or are nearing final design. We recommend that you upgrade files that contain partially designed slabs.

In particular, you should review what rules are used and how the authors interpret and implement the rules.

1.6 Technical support Rules not considered

Specifically, Concept does not consider the following: • ACI 318-99, ACI 318-02, ACI 318-05, ACI 318-08, ACI 318-11: Rule 13.5.3 • AS3600-2001/2009 Rules 9.1.2 (detailing bars for 25% of the negative moment) and 9.1.3

Bentley Systems want you to get the maximum benefit from your purchase of RAM Concept. If you have any questions that are not answered in this manual, please contact us. For customer support, please contact:

• BS8110: 1997 Rule 3.7.3.1 www.bentley.com/serviceticketmanager

RAM Concept

3

Chapter 1

4

RAM Concept

Chapter 2

2 Looking at the Workspace This chapter provides a basic orientation to the RAM Concept interface.

To start a new file:

1 Start RAM Concept and choose File > New. 2 Specify options in the New File dialog box and then click

OK.

2.1 About the workspace

To start a new file from a template:

1 Start RAM Concept, and choose File > New.

When you create a new file, RAM Concept generates layers, plans and perspectives for you to begin design. As you open windows in the workspace, RAM Concept activates the relevant toolbars. Workspace with a plan open:

2 Click Copy File in the New File dialog. 3 Select the file or template you want to copy.

2.2.2 Opening an existing file Use File > Open to open an existing RAM Concept file. For quick access, Concept keeps track of the last ten files you opened and lists them at the bottom of the File menu. To open a file:

1 Choose File > Open. 2 Select the RAM Concept file you want to open.

Note: See “Upgrading Old Files” on page 3 for discussion on using files from an earlier version.

Figure 2-1 A.Standard toolbar for general operations. B. Menu Bar contains the set of menus for the program. Includes the File, Edit, Criteria, Layers, Tools, Process, Report, View, Window, and Help menus. C. Action Tools for manipulating the current view. D. Snap toolbar for setting coordinate snaps for the active plan. E. General Tools for editing the active plan window. F. Layer Specific Tools for editing the active plan window. G. Report Contents Window for viewing, opening, and reordering report sections. H. The active window. I. Status Bar for program status information. J. Command Prompt for displaying tool relative instructions and the current cursor location in plan coordinates.

2.3 Saving a file Save your files often. When you save, you ensure that the file is stored on your computer even in the event of a power failure or system crash. To save and name a file for the first time:

1 Choose File > Save As (since the file has not yet been

saved, you could also choose File > Save). 2 Select the folder in which to save the file.

2.2 Creating and opening files

3 Type a name for your file and click Save. Concept adds

the filename extension .cpt if not provided. When you start RAM Concept, you can create a new file or open an existing file. You can also create a new file based on a template.

2.2.1 Starting a new file When creating a new file, you make basic decisions about your model in the New File dialog, which appears when you choose File > New. You specify the type of slab, code and units to use. You can copy an existing Concept file or template by clicking Copy File on the New File dialog.

RAM Concept

To save any open file:

1 Choose File > Save (if you have not yet saved the file,

and the Save As dialog box appears, follow the previous steps for saving for the first time). To save a file as a template:

1 Choose File > Save Template. 2 Click Continue on the warning message box. 3 Type a name for the template and click Save. Concept

adds the filename extension .cpttmp (if not provided) and saves the file without the objects.

5

Chapter 2

2.3.1 Saving a copy of a file with a new name or location

2.5 Expanding tool buttons

Use the Save As command to create a copy of a file and change its name or location. The original file and the copy are completely separate and any work you do on one file does not affect the other.

Some tool button icons have a small triangle in the lower right corner ( ). This indicates that there are other similar tools available for this button. Press down on the left mouse button for one second over the tool button to reveal a popup menu. Select a tool from the menu. The selected tool becomes the new tool for that button.

2.3.2 Reverting to a backup copy Expanding tool button with pop-up:

For version control, Concept creates a copy of your last save every time you save your file to allow you to go back to an older version if necessary. Concept creates the file with the filename extension .cpt.bak1. If you need to revert to an older version of a file, use the backup copy created by Concept.

2.3.3 Restoring an auto-save file As a safety net, Concept automatically saves a copy of your working file in the same folder as the original and with the filename extension .autosave. Concept updates the autosave file approximately every 2 minutes if you have made changes to your original file. Once you save your file, Concept deletes the auto-save file since your saved version is up to date. We recommend that you save often to prevent loss of work. If a computer malfunction or loss of power occurs while you are using Concept, when you restart Concept it detects the last auto-save file and open it automatically. If you open a second copy of Concept while one is running, the second copy may detect the auto-save file of the first and open it. In this case, just close the auto-save file and continue.

Figure 2-2 Pressing down on the left mouse button for one second over the Selection tool reveals a pop-up menu.

2.6 Rearranging toolbars 2.4 About templates A template file contains everything a normal file includes (such as specification settings, plans, etc.) but has no objects. You can create a template from any RAM Concept file by choosing File > Save Template. Concept saves a copy of your file without any objects and with the .cpttmp filename extension. For details on how to save a template, see “To save a file as a template:” on page 5. Copy an existing template file by choosing File > New and clicking Copy File to create a new file based on the template. For more information on starting a new file from a template, see “Starting a new file” on page 5.

6

You can move the toolbars in RAM Concept to suit your particular work habits. To move a tool bar, click on the handle of the toolbar and drag the toolbar to its new location. The toolbar handle is two lines on the right edge of horizontal toolbars or at the top edge of vertical toolbars. The toolbars snap to the edges of the application window or can remain floating in the workspace.

2.7 Using the right mouse button RAM Concept provides some of the commands available from the menus or toolbars in a special context-sensitive pop-up menu that appears when you click the right mouse button. The contents of the menu vary depending on where you click, what window is active, and whether there is a current selection.

RAM Concept

Chapter 2

2.8 Undoing changes

taken. To redo a command that has been undone, choose Edit > Redo.

RAM Concept provides multiple levels of undo to correct mistakes or reverse actions you have taken. Concept limits the amount of memory used to record undo information. Concept is therefore able to undo more small operations (deleting 10 objects) than large operations (deleting 1000 objects). Choose Edit > Undo to reverse the last action

Note: The Undo command cannot reverse the Generate

RAM Concept

Mesh and Calc All commands. All changes you have made are committed once you perform one of these operations.

7

Chapter 2

8

RAM Concept

Chapter 3

3 Understanding Layers In RAM Concept, objects (such as walls, columns, slab areas, springs, loads, tendons, design strips, etc.) make up the structural model. Since there are so many objects involved in modeling a structure, Concept uses layers to organize these objects.

Drawing Import Layer

A layer is a collection of related objects and each object in Concept resides on one and only one layer. You can handle all of the objects on a single layer as a group or individually.

Mesh Input Layer

3.1 Modeling with objects

This layer contains all the imported CAD drawing information. Concept automatically stores any imported drawings on this layer.

This layer contains the objects that define the geometry of the structure. Concept uses these objects to generate corresponding finite element objects on the Element Layer. Layer-Specific Objects: Column, Wall, Slab Area, Slab Opening, Beam, Point Support, Line Support, Point Spring, Line Spring, Area Spring. Element Layer

Since objects make up the structural model, they are more than a combination of points and lines. Each object is an individual entity with properties. Column object properties, for example, include concrete mix, height, width, depth, and more. You draw some objects on plans, and RAM Concept creates some objects automatically when you generate the finite element mesh or run an analysis calculation. If you have wall, column, and slab area objects on the Mesh Input layer, Concept creates corresponding wall element, column element, and slab element objects on the Element layer when you generate the finite element mesh. If you want to create or edit objects on a layer, use the plans on that layer. When you draw columns on the Standard Plan of the Mesh Input layer, you are creating objects on the Mesh Input layer. These objects belong to the layer and not the plan. They are editable by any plan on the Mesh Input layer, but not by plans on any other layer. Each object is an individual entity so you can manipulate it both separately and together with other objects on the same layer.

This layer contains the finite element objects. These objects can be generated by Concept based on the information on the Mesh Input Layer, or can be created by hand. Layer-Specific Objects: Column Element, Wall Element, Slab Element, Point Support, Line Support, Point Spring, Line Spring, Area Spring. Loading Layers (Self-dead, Balance, Hyperstatic, Temporary Construction (at Stressing), Other Dead, Live (Reducible), Live (Unreducible), Live (Storage), Live (Roof) and User-defined)

These layers contain all the information that defines the loads on the structure. In Concept, a loading is a set of loads applied as a group, such as the live loads. The loading layers also contain the loading analysis results. Concept provides the self-dead, balance, and hyperstatic loading layers by default and you cannot delete them. You can define an unlimited number of loadings and Concept creates a corresponding layer for each. Layer-Specific Objects: Point Loads, Line Loads, Area Loads.

Note: You cannot edit the load objects on the Self-Dead 3.2 Managing layers

Loading Layer, Balance Loading Layer, and Hyperstatic Loading Layer. Pattern Layer

RAM Concept performs most of the layer management automatically. Almost all of the layers you need to design a structure are already in place when you start a new file. Concept adds appropriate layers when you create new Loadings, Load Combinations, and Rule Set Designs.

This layer contains the load patterns for the structure.

Note: You can create and edit a separate group of Line

This layer contains the design strips, design sections and punching checks for the structure.

Objects, Dimension Objects, and Text Note Objects on every layer.

RAM Concept

Layer-Specific Objects: Load Patterns. Design Strip Layer

Layer-Specific Objects: Span Segments, Span Boundaries, Strip Boundaries, Design Sections, Punching Checks.

9

Chapter 3 Tendon Parameters Layers (Latitude and Longitude)

Design Status Layer

These layers contain high level post-tensioning objects. Although there are two tendon layers, Latitude and Longitude, there is no requirement to use both layers. You can draw tendon parameters on the tendon parameters layers in whatever manner you wish.

This layer contains the summary of all the design results. The summary information is automatically created by Concept when you Calc All. You cannot create, edit, or delete the objects on this layer but you can view them.

Layer-Specific Objects: Banded Tendon Polyline, Distributed Tendon Quadrilateral, Tendon Void, Profile Polyline.

3.2.1 Determining which plans contain objects

Manual Tendon Layers (Latitude and Longitude)

These layers contain the layout of post-tensioning tendons and jacks for the structure. Although there are two tendon layers, Latitude and Longitude, there is no requirement to use both layers. You can draw tendons on the tendon layers in whatever manner you wish. Layer-Specific Objects: Tendon, Jack. Load Combination Layers (All Dead, Dead and Balance, Initial Service, Service, Sustained Service, Factored and Userdefined)

Some layer icons next to a layer name in the contents window have a dot on the top “sheet”. This indicates that there is at least one object resident on that layer. In other words, the dot means there exists at least one object that belongs to that layer.This is different to any visible objects on one of the layers’ plans, which may or may not belong to that layer.

Note: There may be a lag time (such as 10 seconds) for this to happen after the first item on the layer is drawn.

Note: This feature is added in response to the frustration

These layers contain the load combination analysis results.

of having to search every layer in support files to see if they contained any items.

Note: The load combinations listed are for ACI318. Other

Note: Dots do not typically appear on Load Combination

codes use some different terminology.

layers as these layers have no items drawn on them. This does NOT mean the load combo is not used in the design.

Rule Set Design Layers (Code Minimum, User Minimum, Initial Service, Service, Sustained Service, Strength, Ductility)

These layers contain the rule set design analysis and design results.

Note: The rule set designs listed are for ACI318, other codesuse some different terminology. Load History Deflection Layers

These layers contain the results of the load history analyses. Additional Mass Loading Layer

This layer contains loads that are converted to mass for the vibration analysis. Layer-Specific Objects: Point Loads, Line Loads, Area Loads. Vibration Analysis Layer

This layer contains vibration related analysis results. Layer-Specific Objects: Excitation Areas.

10

Figure 3-1 Layer icons indicating that there are objects on the following layers: Mesh Input, Element, Design Strip, Reinforcement

RAM Concept

Chapter 4

4 Using Plans and Perspectives Plan windows are used to create, view, and edit objects in two dimensions while perspective windows provide a three dimensional view of those objects.

4.1 Using plans A plan is a view of the geometric model and results. You can view any object on any plan. You can only create and edit an object on a plan belonging to the object’s layer. For example, an other dead load can only be edited on a plan belonging to the Other Dead Loading layer. Objects are drawn and edited with tools located in LayerSpecific toolbars, and the Tools menu. The available tools are dependent on which plan is the active window in the workspace. Once you draw an object on a plan, the object belongs to that plan’s layer.

Note: For information on drawing and editing objects, see the following chapter.

4.2 Creating new plans

appear larger than far objects of the same size. The Parallel Projection ( ) and Perspective Projection ( ) toggles control which way the image is rendered. One, and only one, of these toggles is always set.

4.3.2 Selecting the modeling The Wire Frame Modeling ( ) and Solid Modeling ( ) toggles control how the image is rendered. The wire frame is made of only the edges of the visible objects whereas the solid model shows the visible objects’ surfaces. The solid model is more realistic, however the wire frame image is often useful since it allows you to see through the model. One, and only one, of these toggles is always set.

4.3.3 Rotating the model Use the Rotate about x- and y-axes tool (

) and the

Rotate about z-axis tool ( ) to rotate the model about the screen’s x-, y-, and z-axes. To rotate the model:

1 Select the Rotate about x- and y-axes tool (

Create new plans when you need additional ones to those provided by default. To create a new plan:

Rotate about z-axis tool (

) or the

).

2 Click once on the perspective window to begin and move

the cursor until you position the model as desired. 3 Click on the perspective again to set the view.

1 Choose Layers > New Plan. 2 Enter a name for the plan. (Concept automatically

prepends the layer name and appends the word “Plan”).

4.4 Creating new perspectives

3 Select the layer on which you want the plan and click OK.

Create new perspectives when you need additional ones to those provided by default.

4.3 Viewing perspectives Perspectives provide a three dimensional view of the model. You can view the model from any angle by rotating the perspective about the x-, y-, and z-axes. The model can be viewed in parallel projection or perspective projection and can be modeled as a solid or wire structure.

4.3.1 Setting the projection You can render the model in either parallel or perspective projection. In parallel projection, lines that are parallel in the original model are also drawn parallel in the three dimensional image. In perspective projection, near objects

RAM Concept

To create a new perspective:

1 Choose Layers > New Perspective. 2 Enter a name for the perspective. (RAM Concept

automatically prepends the layer name and appends the word “Perspective”). 3 Select the layer on which you want the plan and click OK.

4.5 Controlling views You can manipulate the plan and perspective windows to show the desired view or information. Zooming and

11

Chapter 4 panning allow you to change what portion of the model you are viewing. RAM Concept usually regenerates the view automatically. It is sometimes necessary, however, to use

2 Click once on the plan to begin panning, click again when

the Redraw command ( screen.

4.5.3 View History

) to update the image on the

Plans and perspectives represent unique views of the model. You control which object types are visible and their colors, font, and line type for each plan and perspective.

4.5.1 Zooming to magnify or diminish Use zooming to magnify or diminish the plan or perspective view. If you have a mouse with a wheel button, roll the wheel to zoom in and out at the cursor location. Zoom In (

) and Zoom Rectangle (

) magnify the

view. Zoom Out ( ) diminishes the view. You can set the view to encompass the entire model by using Zoom Extent (

).

To magnify or diminish the view with the mouse wheel button:

1 Place the cursor on a location over the active plan or

perspective window. This is the zoom center point.

the view is in the desired position.

The View Previous ( ) and View Next ( implement a history of your views.

) tools

The view history operates much like the forward and backward buttons in a web browser. Each zoom or pan action is added to the view history. The View Previous (

) button steps back through previous views and the

View Next button ( ) steps forward through the views. The buttons are disabled if there are no views in that direction. If you step back to a previous view and perform a zoom or pan action, the new view will replace the entire next view history. The View History is implemented for plans and perspectives. Each plan or perspective’s view history is maintained separately. Switching from one plan or perspective to another does not affect the view history for either plan.

2 Fence the area you want to magnify.

All zoom, extent, pan, and rotation view changes are recorded in the view history. Some consecutive view changes of the same type are compressed into one view history item to prevent the history from getting cluttered with many similar views. For example, consecutive Zoom In actions -- whether by the Zoom In tool or by mouse wheel movements -- add only one new view to the history.

4.5.2 Panning to reposition

4.5.4 Regenerating

Panning allows you to reposition the view in the plan or perspective window. If you have a mouse with a wheel button, press down on the wheel over the view and pan.

Regenerating the view is necessary when anything occurs that invalidates the current view. When you generate the mesh, analyze the model or change the settings, the open windows may need updating. In most cases, RAM Concept automatically regenerates for you. If you find that the view

2 Roll the mouse wheel button away from you to zoom in,

and toward you to zoom out. To magnify a specific area in the view:

1 Select the Zoom Rectangle tool (

).

You can use the Pan tool ( ) to move the view as well. In addition, plans have scroll bars along the bottom and right side of the window that you can use to reposition the view.

is not up to date, click Redraw ( in the active window.

) to regenerate the view

To reposition the view with the mouse wheel button:

1 Press down on the mouse wheel button over the active

plan or perspective window. 2 Pan the view into position and release the wheel button.

4.5.5 Setting the visible objects Use the Visible Objects dialog box to set which objects types are visible on a plan or perspective. Plans and

To reposition the view with a tool:

1 Select the Pan tool (

12

).

RAM Concept

Chapter 4 perspectives can show objects from any layer, but you can only edit objects on a plan from the object’s layer.

or perspective, the window initially uses the default scheme.

Figure 4-1 Visible Objects dialog box (Mesh Input tab) Figure 4-2 Appearance dialog To show or hide objects on a plan or perspective:

1 Make the plan or perspective the active window. 2 Choose View > Visible Objects (

).

3 Click on the tab for the object’s layer.

To set the appearance scheme for a plan or perspective:

1 Make the plan or perspective the active window. 2 Choose View > Appearance (

).

3 Select the scheme from the list of schemes on the left side

The plan or perspective’s layer is the one initially selected.

of the Appearance dialog and click OK.

4 Check boxes to show objects and uncheck to hide

Note: You can also right click to see a popup menu that

objects, then click OK.

Note: You can also right click to see a popup menu that includes the Visible Objects command.

includes the Appearance command. To create a new appearance scheme:

1 Choose View > Appearance (

).

2 Click New below the list of schemes in the Appearance

4.5.6 Changing colors, font, and line type

dialog.

Each plan and perspective has an associated appearance scheme that dictates the colors, font, and line type used for the objects shown. When a plan or perspective is the active window, you can select and modify its appearance scheme using the Appearance dialog. If you change the settings of an appearance scheme, it affects all the plans and perspectives that use that scheme. You can create as many appearance schemes as you need to customize the look of your plans and perspectives. When you create a new plan

3 Type a name for the new scheme and select the base

scheme. The settings from the base scheme initialize the new scheme. To delete an appearance scheme:


).

2 Select the scheme you want to delete from the list of

schemes in the Appearance dialog. 3 Click Delete below the list of schemes to delete the

highlighted scheme. To set a new default scheme:


).

2 Select the scheme you want to make the new default

scheme from the list of schemes in the Appearance dialog. 3 Click Set As Default below the list of schemes to make

the highlighted scheme the new default scheme. RAM Concept uses this scheme to initialize newly created plans and perspectives.

RAM Concept

13

Chapter 4 You can select the color of every drawn object type for each appearance scheme. You can also set the background, grid and highlight colors. If an object type has no color

2 Select the appearance scheme (if a plan or perspective is

selected ( ), RAM Concept uses the color setting for the object’s layer. For example, you can set the Tendon object color to no selection, and then set the Latitude Tendon layer to red and Longitude Tendon layer color to blue. RAM Concept uses the foreground color in the case that you have selected neither the object type color nor the layer default color.

3 Enter the font scale and click OK.

Note: A font scale of zero causes the font to stay a constant size regardless of the plan scale. A non-zero value scales the font to be the same relative size as you zoom in and out.

4.6 Setting up the grid

To change the colors in an appearance scheme:


the active window, the selection is already the scheme set for that window).

).

2 Select the appearance scheme (if a plan or perspective is

the active window, the selection is already the scheme set for that window). 3 Select the item from the drop-down list (if changing

plotting colors skip this step).

A grid can be set up to help you draw objects accurately by providing snap points at a designated spacing. The Plan Grid Setup dialog allows you to make the grid visible and to change the spacing, origin, and rotation angle of the grid. You can change the grid setting for the active plan window or all plan windows at once.

4 Click on the color selection box for the item and choose

a color. Lines of drawn objects can be set to solid, dashed, or dotted. Reference lines have Line Type and Line Width properties that are independent of the appearance scheme setting. The transparency of all Strip Plots in both 2-D and 3-D are controlled via the Transp. % control in the Appearance Settings dialog. This setting is used to modify the transparency already set in the default strip plot colors defined.

4.5.7 Changing font size You can change the font size in two ways. In the appearance schemes, you can select the font size for all text other then text notes. With the font buttons, you can temporarily change the font size.

To make the grid visible for a plan:

1 Make the plan the active window. 2 Choose View > Grid.

To temporarily change the font size:

1 Click Enlarge Fonts (

Figure 4-3 Plan grid dialog box

) or Shrink Fonts (

).

3 Check Show Grid and click OK.

Note: The temporary font size change only affects the

Note: If you want the grid to be visible on all plans then

active window and RAM Concept discards the change when the window is closed.


check Set for all Plans. includes the Grid.

4.5.8 Changing font scale

To change the grid settings for a plan:

You can select the font scale so that the font size either changes or stays unchanged as you zoom in and out on a plan.

2 Choose View > Grid. 3 Enter values in the Plan Grid Setup dialog box and click

OK.

To set the font scale:


1 Make the plan the active window.

).

Note: If you want the grid settings to apply to all plan windows then check Set for all Plans.

14

RAM Concept

Chapter 4

RAM Concept

15

Chapter 4

16

RAM Concept

Chapter 5

5 Drawing and Editing Objects Drawing objects is the cornerstone of using RAM Concept. There are many tools available to make this as straightforward as possible. To create or edit objects on a layer, use the plans on that layer. You draw and edit objects on plans using the tools from the Layer-Specific toolbar.

In general, the snap extension setting causes the other snap calculations to behave as if the line segments displayed extended to be infinitely long lines. The specific changes to the other snap settings are: • Intersection: intersections between infinite lines (defined by visible line segments) are snappable points. • Point: no effect. • End Point: no effect.

5.1 Precision drawing with snaps RAM Concept provides drawing tools and settings to help you work precisely. Snap tools allow you to snap the cursor to precise points on objects or locations on the screen. Using snaps is a quick way to specify an exact location on an object without drawing construction lines or knowing the exact coordinate. Whenever you move your cursor over an object, RAM Concept identifies snap points based on what snaps are active. To turn on a snap, click on its button. Click on the button again to turn off the snap. Snap to Intersection ( ) snaps to the intersection of any two lines including polygon vertices. Snap to Point ( ) snaps to any defined point such as the center of a column, end point of a line, or vertex of a polygon. Snap to End Point ( ) snaps to the end points of lines (including vertices of polygons). Snap to Mid Point (

) snaps to the mid points of lines.

Snap Nearest Snapable Point ( ) snaps to the point on a drawn object nearest to the cursor. Snap Orthogonal ( ) snaps orthogonally in the direction of the grid’s local x- or y-axis. This need not be parallel with the global x- and y-axes. Snap to Perpendicular ( from the last click to a line. Snap to Center ( columns. Snap to Grid (

• Nearest: nearby infinite lines (defined by visible line segments) are snappable. • Orthogonal: no effect. • Perpendicular: perpendicular point on infinite lines (defined by visible line segments) are snappable. • Center: no effect. • Grid: no effect.

5.2 Drawing objects To draw objects on a plan, first select a drawing tool by clicking on it or choosing it from the Tools menu. The selected tool will be the active drawing tool for the plan until you select a new tool. Follow the command prompts for points to enter (see Figure 2-1 on page 5). For example, with a Mesh Input layer plan open, and the Column tool selected, the command prompt will read “Enter column center point:”. If you are drawing with a tool and wish to cancel what you have drawn, click the right mouse button, or press the Esc key. If you need to reposition or magnify the view while you are drawing and do not want to cancel the work you are doing, use the mouse wheel button to pan or zoom. See “Controlling views” on page 11 for more information on how to use the mouse wheel button.

) snaps perpendicularly

) snaps the center of polygons and

) snaps to the grid.

Snap Extension ( ) does not create a snapping mode by itself, but it affects the behavior of some of the other snap settings. RAM Concept

• Mid Point: no effect.

5.3 Entering coordinate points Each point on a plan is a location represented by coordinates. Many tools require you to locate one or more points on a plan. With a tool selected, you can enter points by clicking at a location on the plan, entering the coordinates in the command line, entering the relative coordinates in the command line, or by using snaps.

17

Chapter 5 To enter coordinates:

To deselect an object or group of objects from a selection:

1 With the appropriate tool selected, type the x- and y-

1 Choose the Selection tool (

coordinates separated by a comma (e.g. 10, 5).

2 Hold down the Shift key as you fence the objects in the

) or the Utility tool (

).

selection you want to deselect. This deselects the selected objects within and crossing the rectangular area, and selects any objects in the rectangular area not previously selected.

5.4 Using relative coordinates

To deselect only a single object from a selection:

Relative coordinates locate a point on a plan by referencing it to the last point entered. They can be very useful for moving and copying objects a set distance. To enter relative coordinates:



).

2 Hold down the Shift key as you double click on the object

in the selection you wish to deselect. When you are deselecting, RAM Concept interprets a very small rectangle as a double click.

1 With the appropriate tool selected, type the letter “r”

followed by the x- and y-coordinates separated by a comma (e.g. r10, 5).

5.7 Filtering selected objects You can deselect objects from the current selection set by

5.5 Selecting objects Before you can edit objects on a plan, you must select them. Use the Selection tool ( ) or the Utility tool ( ) to select objects on a plan. You select visible objects by fencing the area in which they are located. For example, if you have a slab opening (on the Mesh Input layer) in the middle of a slab, fencing the opening selects both the opening and the slab area because the rectangle crosses the slab area and surrounds the opening. If you want to select just the opening, double click on it. You can select any single object by double clicking on it. To add objects to the current selection, hold the Shift key down as you select. To select an object or group of objects:



).

2 Click at opposite corners of a rectangle. This selects

objects within and crossing the rectangular selection area. (Hold down the Shift key on the first click to add objects to the current selection.)

5.8 Cutting, copying, and pasting objects To cut or copy objects, first select the objects then choose the appropriate command from the Edit menu. RAM Concept places objects that you cut or copy on the Windows clipboard. The coordinate locations of objects pasted from the clipboard are the same as the coordinate location from where you copied or cut them. RAM Concept makes the pasted objects the current selection, so you can reposition them after you paste. To cut objects:

1 Select the object or group of objects you want to cut.

To select only a single object:


choosing the Selection Filter tool ( ). This tool will invoke a dialog that lists all of the currently selected objects grouped by object type. All of the objects of a particular type can be removed from the selection set by unselecting the objects in the list.


).

2 Choose Edit > Cut (or right-click and choose Cut from

the popup menu that appears).

2 Double click on the object you wish to select (Hold down

the Shift key as you click to add the object to the current selection). When you are selecting, RAM Concept interprets a very small rectangle as a double click.

To copy objects:

1 Select the object or group of objects you want to copy. 2 Choose Edit > Copy (or right-click and choose Copy

from the popup menu that appears).

5.6 Deselecting objects

To paste objects from the clipboard:

1 Choose Edit > Paste (or right-click and choose Paste from

You can deselect objects from the current selection by holding the Shift key while you select objects to remove from the selection. 18

the popup menu that appears). You can also copy and move, rotate, stretch or mirror an object in one step by pressing the Shift key while you use RAM Concept

Chapter 5 the Move tool (

), Stretch tool (

), Rotate tool (

)

or Mirror tool ( ). See “Moving, rotating, stretching, and mirroring objects” on page 19 for more information.

5.9 Copying and pasting objects by layer The "layer" clipboard mode simplifies the process of copying data from multiple layers of one Concept file to another Concept file. Clipboard data is built up from multiple objects on different layers. Each object added to the clipboard data is tagged with its source layer. When the layer clipboard data is pasted into a plan, only data that originated from the same layer as the destination plan will be pasted into the plan. To append objects to the layer clipboard:

1 Select the object or group of objects you want to copy. 2 Choose Edit > Append (or right-click and choose Append

from the popup menu that appears). 3 Repeat for each layer.

When objects are appended from a layer, they completely replace the objects for that layer. Other layers are not affected.

2 Select the Add Node tool (

).

3 Click on any edge of a polygonal object.

Nodes must be added to an edge of a polygonal object. It is possible to enter the new node coordinates, but it will be ignored if the new location is not exactly on an edge. It is better to add the node at an approximate location, then stretch the node to the final position. The exact location can be specfied as coordinates or by snapping with the Stretch tool. To delete a node from a polygonal object:

1 Select the object or group of objects to edit. 2 Select the Delete Node tool (

).

3 Click on any node of a polygonal object.

A node cannot be deleted if it would create a misshapened polygon (less than 3 points, or all points colinear). Some polygonal objects may define a varying property, e.g. the force constant of an Area Spring. The varying property is defined by seed values of the first 3 nodes of the polygon. Therefore, the first 3 nodes cannot be colinear when the varying property is defined. Adding or deleting nodes does not change the value of the varying property. However, the start of the polygon may have to be shifted to a new node, so that the first 3 nodes are not colinear. The seed values will be adjusted accordingly for the new locations.

To paste objects from the layer clipboard:

1 Choose Edit > Paste (or right-click and choose Paste from

the popup menu that appears).

5.11 Moving, rotating, stretching, and mirroring objects

2 Repeat for each layer.

When the clipboard contains layer data, the Paste menu item is only enabled when the clipboard contains data for the current plan's layer. The contents of the layer data cannot be viewed directly, but the enabled Paste menu item is an indication that the clipboard contains data from the current layer. The layer clipboard data is stored in the system clipboard selection. This means that the layer clipboard data is cleared any time another Copy operation is performed, by Concept or by any other application on the system. The selection is also lost if the system is shut down or restarted.

An object or group of objects must be selected before using the Move tool (

), Stretch tool (

), Rotate tool (

)

or Mirror tool ( ) (See “Selecting objects”). If you hold down the Shift key on the first click of a move, rotate, or mirror, the operation will be performed on a copy of the selection rather then the selection itself. To move a selection:

1 Select the object or group of objects to move. 2 Choose the Move tool (

).

3 Enter the point from which to move (hold down the Shift

5.10 Editing polygon objects

key as you click to move a copy of the selection). 4 Click on the point to where you want the object, or group

Nodes can be add or removed from polygonal objects with the Add Node (

) and the Delete Node tools (

To add a node to a polygonal object:

1 Select the object or group of objects to edit.

RAM Concept

).

of objects, to move. To stretch the selection:

1 Select the object or group of objects to stretch. 2 Choose the Stretch tool (

).

19

Chapter 5 3 Snap to the point you want to stretch on the selection

4 Click on the point to where you want the object, or group

(limited to highlighted control points).

of objects, to stretch.

4 Click on the point to where you want the object, or group

of objects, to stretch.

5.13 Manipulating the model as a whole

To rotate a selection:

1 Select the object or group of objects to rotate. 2 Choose the Rotate tool (

).

The Move Model tool (

3 Enter the rotation center point (hold down the Shift key

as you click to rotate a copy of the selection). 4 Enter the rotation start angle or a point to create a line to

rotate. 5 Click on the new end point of the rotation line or enter an

end angle.

Rotate Model tool (

), Mirror Model tool (

), and

) work just like the Move tool

( ), Mirror tool ( ), and Rotate tool ( ) except they affect the whole model (all layers). You can also scale the entire model with the Scale Model tool (

).

To move the entire model:

To mirror the selection:

1 Choose the Move Model tool (

1 Select the object or group of objects to mirror.

2 Enter the start point.

2 Choose the Mirror tool (

3 Enter the move point.

).

3 Enter the two points that create the line across which you

would like to mirror the selected object(s). (Hold down the Shift key as you click to mirror a copy of the selection.)

).

To rotate the entire model:

1 Choose the Rotate Model tool (

).

2 Enter the rotation center point (hold down the Shift key

as you click to rotate a copy of the model). 3 Enter the rotation start angle or a point to create a line to

5.12 Using the Utility tool to move and stretch

rotate. 4 Click on the new end point of the rotation line or enter an

end angle. The Utility tool ( ) is a multi-purpose tool used for selecting, moving, and stretching objects. See “Selecting objects” on page 18 for information on how to select objects with the Utility tool. Once you have selected an object or group of objects, you can move or stretch a grip point by snapping to it on the selection.

To mirror the entire model:

1 Choose the Mirror Model tool (

2 Enter the two points that create the line across which you

would like to mirror the model (hold down the Shift key as you click to mirror a copy of the model).

To move an object by one of its grips:

To scale the entire model:

1 Choose the Utility tool (

1 Choose the Scale Model tool (

).

).

).

2 Select an object or group of objects.

2 Enter a scale center point.

3 Snap to a grip point and position the cursor in the top half

3 In the Scale Model dialog box, enter the relative scale

of the snap area until you see the move cross cursor ( ) then click. (Hold down the Shift key as you click to move a copy of the selection.) 4 Click on the point to where you want the object, or group

of objects, to move. To stretch an object by one of its grips:

1 Choose the Utility tool (

).

2 Select an object or group of objects. 3 Snap to a grip point and position the cursor in the bottom

half of the snap area until you see the stretch cursor ( then click.

20

)

factors and click OK.

5.14 Editing object properties The properties of an object define its individual characteristics. For example, the properties of a Line object include the Line Type and Line Width. Some objects’ properties can be edited together as a group. Specifically, you can always modify objects of the same type together, and you can often modify objects of different types but with similar properties together. For example, you can edit

RAM Concept

Chapter 5 the Concrete Mix and Height properties of Column and Wall objects together.

5.16 Adding reference lines, dimensions, and text notes

To change the properties of an object or group of objects:

1 Select the object or group of objects. 2 Choose Edit > Selection Properties, or right-click and

choose Selection Properties. 3 Specify the property values in the Properties dialog and

click OK.

5.15 Setting default properties

The Line tool (

), Dimension tool (

( ) are all used to add information to plans. These objects are not part of the structural model and RAM Concept does not consider them when generating the mesh or calculating results. As for all objects, the lines, dimensions and text objects belong to the layer on which they are drawn. To draw a line:

1 Choose the Line tool (

It is useful to set the default properties of object drawing tools so that when you use the tool the drawn object has the desired properties. This is valuable when many objects will have the same properties. To set the default properties for an object drawing tool:

1 Double click on the drawing tool or with the tool

selected, choose Tools > Current Tool Properties. 2 Specify default property values in the Properties dialog

and click OK. When you now use the tool, it will draw objects with the specified default properties.

), and Text tool

).

2 Click at the line start point (or enter the coordinates in the

command line). 3 Click at the line end point (or enter the coordinates in the

command line). To draw a dimension line:

1 Choose the Dimension tool (

).

2 Click at the start point. 3 Click at the end point. 4 Click at the offset point where the dimension line will be

located.

Note: Changing the default properties of an object

To draw text:

drawing tool does not change the properties of such objects already drawn.

1 Choose the Text tool (

).

2 Click at a point (or enter the coordinates in the command

line). 3 Right click and choose Selection Properties. 4 Enter the text and its properties.

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Chapter 5

22

RAM Concept

Chapter 6

6 Viewing Objects in Text Tables A text table shows all the objects of a particular type on a specific layer. Tables provide a customizable textual view of each objects’ properties. You can access text tables from the Tables folder of any layer. To open a text table:

1 Go to the Tables folder of the object type’s layer. 2 Open the appropriate text table from the folder.

For example, the text table for Walls Below on the Mesh Input layer can be opened by choosing Layers > Mesh Input > Tables > Walls Below.

6.1.1 Choosing which rows and columns to show Customize the table columns and rows by clicking on the Customize button above the table. In the Customize dialog box, you can select which rows and columns are visible in the table. Check the columns you want to see and uncheck the columns you want hidden. To make a table column visible or hidden:

1 Click on the Customize button above the table. 2 In the Customize dialog box, to make a column visible,

check the checkbox. To hide the column, uncheck the checkbox. 3 Click OK.

6.1.2 Sizing table columns You can resize columns by changing the width of the column header. To resize the width of the column:

1 Place your cursor on the line between two columns on the

table header and press down on the left mouse button. 2 Drag the table header to its new width and release the left Figure 6-1 Mesh Input: Walls Below Table

mouse button. The table will print as seen on screen so the column widths you set will appear the same way on paper.

6.1 Customizing tables 6.1.3 Sorting table rows You can choose which columns and rows are visible in the table, and the column widths. You can also sort the rows based on a particular column’s values in ascending or descending order.

RAM Concept

To sort the table rows according to the values in a column, click on the column header once for ascending order. Click on the column header again to sort in the descending order.

23

Chapter 6

24

RAM Concept

Chapter 7

7 Choosing Units RAM Concept allows you to work with three unit systems: US, SI and MKS. Some designers refer to the US units system as “US customary units”, and others call it “Imperial”. SI and MKS are metric unit systems, with MKS using mass rather than weight. It is up to you which system you use but local practice should dictate your choice.

2 Do one of the following:

• Select each unit by accessing the appropriate drop down box. • Select a unit system by clicking on US, SI, or MKS at the top of the window.

Note: There is often a long list of choices for the units. Scroll down the drop down menu to view the options.

The choice of actual units is more subjective. For example, after choosing the US system, one designer might use the default area load units of pounds per square feet, and another might change the selection to kips per square feet.

7.1 About units Internally, RAM Concept performs all calculations with the SI unit system. It converts all property values into an equivalent SI unit prior to calculation. Once complete, it converts the values back into the selected units for reporting. It is possible to mix unit systems (e.g. pounds and meters) but this is not advisable.

7.2 Selecting units A new file has default units that you can change at any time.

7.2.1 Selecting the default units The default units depend on how you created the file. When you use a template or an existing file, the default units are those of the source. When you create a file using the New command, you only have a choice of default units for ACI 318 (US or SI). For all other codes, the default units are SI.

7.2.2 Changing the units You can change either the unit system or individual units. To change the units:

1 Choose Criteria > Units.

Figure 7-1 Units Window

7.3 Specifying report as zero RAM Concept allows you to filter out trivial results with the Report as Zero option. For example, column reactions have components for Fr, Fs, Fz, Mr and Ms. Some of these values, such as Fr and Fs, may be very small and hence not important. Filtering small values from plan plots can make the results easier to read.

Note: Using this feature could result in human error, as you might later assume zeroed values are exactly equal to zero. You specify Report as Zero in the Units window.

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25

Chapter 7 To specify Report as Zero:

1 Choose Criteria > Units.

2 Enter one or more Report as Zero values.

Note: You can also turn off plotted values such as Fr and Fs with the plot menu. See “Setting the plotted results” on page 165.

26

RAM Concept

Chapter 8

8 Choosing Sign Convention RAM Concept allows you to choose the sign convention for loads, analysis and reactions. RAM Concept uses the Cartesian coordinate system with the following sign convention for axes:

Fy In the positive y-direction (see coordinate axes). Fz In the negative z-direction (see coordinate axes). Mx (moment about the X-axis) Per right-hand-rule. My (moment about the Y-axis) Per right-hand-rule. Mz (moment about the Z-axis) Per right-hand-rule.

You cannot change the sign of the coordinates’ axes.

Positive analysis

Sign convention dictates how you input parameters and how RAM Concept displays results. For example, the sign convention of an applied load dictates whether the input value is positive or negative. Note that changing a sign setting does not change the real value of any previously specified data. For example if a +10 kips downward load was specified when RAM Concept had a downward-positive load sign convention and then the load sign convention was changed to upwardpositive, the load value would now be reported as -10 kip, but the load would still be a 10 kip downward load. Similarly, a change in sign convention does not affect the true value of results. When you add loads after a change in sign convention, you must observe the new sign convention.

8.1 Selecting sign convention A new file has a default sign convention that you can change at any time.

8.1.1 Default sign convention The default sign convention depends on how you created the file. If you use a template or an existing file then the default sign convention is that of the source.

Figure 8-2 Top row, left to right: Vertical Element Shear, Element Bending, Element Axial, Vertical Deflection. Bottom row, left to right: Horizontal Shear, Twist, Lateral Deflection, Angular Deflection.

Vertical element shear Positive z-shear on the positive x- and y-faces. Element bending Tension bottom face. Element axial Tension. Vertical deflection In negative z-direction (down). Horizontal shear Positive y-shear on Positive x-face (equivalent to Positive x-shear on Positive y-face). Twist Positive x-axis moment on positive x-face (equivalent to negative y-axis moment on positive y-face). Lateral deflection Positive in x- and y-axes directions. Angular deflection Per right-hand-rule about x- and yaxes. Positive reactions

When you create a file (not from a template), the sign convention is as follows:

Figure 8-3 Left to right: Fx, Fy, Fz, Coordinate Axis, Mx, My, Mz.

Positive loads

Fx In the positive x-direction (see coordinate axes). Fy In the positive y-direction (see coordinate axes). Fz In the positive z-direction (see coordinate axes).

Figure 8-1 Left to right: Fx, Fy, Fz, Mx, My.

Mx (moment about the x-axis) Per right-hand-rule.

Fx In the positive x-direction (see coordinate axes).

My (moment about the y-axis) Per right-hand-rule.

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27

Chapter 8 Mz (moment about the z-axis) Per right-hand-rule.

8.2 About plot sign convention

Note: The only difference in defaults between Positive Loads and Positive Reactions is Fz. This is because point loads are usually down if positive, and vertical reactions are usually up if positive.

8.1.2 Changing the sign convention You can change the sign convention for any loads or results, but only one at a time. To change the sign convention:

1 Choose Criteria > Signs. 2 Change each positive sign by clicking the appropriate

With the exception of vertical deflection, line plots show positive results plotted above the axis line. This ensures that plots do not appear upside down. For axis lines that are parallel to the y-axis (and hence have no “above the axis line” direction), line plots show positive results to the left of the axis line.

Note: Line plots show positive vertical deflection below the axis line. Perspectives are plotted with positive results in the global z-direction (what is considered positive is dependent upon the sign convention of the Value Plotted). For example, a perspective of deflection shows positive deflection up.

graphic. The direction changes. You cannot change the sign of the coordinates’ axes.

Figure 8-4 Signs Window

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RAM Concept

Chapter 9

9 Specifying Material Properties RAM Concept uses materials as part of the input and the results. You specify concrete mixes and post-tensioning systems as part of the input and Concept reports reinforcement bar requirements as part of the results. You can use the materials provided or create your own. For example, you might want to redesign the floor with the actual tested strength of the concrete poured on site. In this case, you would create a new concrete mix defined with that strength. You can delete any of the materials that you find are unnecessary.

9.1 Viewing the available materials The Materials window shows the names and properties of concrete mixes, PT systems and reinforcing bars. To view the materials:

1 Choose Criteria > Materials.

9.2 Material properties The following is a list of Material properties:

9.2.1 Concrete Mix Mix Name The label used to identify a concrete mix. The mix name is not necessarily the concrete strength. Each column, wall, slab and beam has a concrete mix property. Density The concrete mass density used to calculate various stiffness properties for Concrete. Density for Loads The concrete mass density used to calculate self weight. f’ci The characteristic cylinder strength of the concrete mix at the time of applying prestress (also known as initial strength). f’c The characteristic cylinder strength of the concrete mix.

Note: f’ci and f’c are used for all codes except BS8110. fcui The characteristic cube strength of the concrete mix at the time of applying prestress (also known as initial strength). fcu The characteristic cube strength of the concrete mix.

Note: fcui and fcu are only used for BS8110 and IS456. Poisson’s Ratio The negative of the ratio of lateral strains to axial strains for an axially loaded material. This is usually 0.2 for concrete. Ec Calc The method used to calculate Young’s Modulus (for both initial characteristic strength and characteristic strength). This can be according to the active code rules or a specified value. User Eci The user defined Young’s Modulus used for initial cross section analysis. User Ec The user defined Young’s Modulus used for global analysis, service cross section analysis and strength design.

9.2.2 PT Systems

Figure 9-1 The Materials window.

System Name The label used to identify a PT system. It usually describes the system, such as strand size and bonding. Type Whether the system has unbonded or bonded strand.

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29

Chapter 9 Aps The cross sectional area of one strand. Since strand is usually comprised of seven wires then the area is more complicated than Πd2/4. Eps The Young’s Modulus of the strand at zero strain. fse The assumed effective stress in the strand after all losses. Using jacks overrides this assumption. See “About jacks” on page 144 for further information. fpy The yield stress of the strand. fpu The ultimate stress of the strand. Duct Width The width or diameter of bonded tendon duct. Max Strands Per Duct The maximum number of strands in a bonded tendon (use 1 for unbonded tendons). Minimum Radius The minimum vertical radius that allows satisfactory placement of tendons in the field. You should consult with a local PT supplier. A value of zero disables radius checking for this PT system. Jacking Stress / Anchor Friction / Wobble Friction / Angular Friction / Seating Distance / Long-Term Losses Friction loss calculations use these properties. They have no effect unless tendon jacks are used. See “Jack properties” on page 144 of Chapter 26, “Defining Tendons” for further information.

9.2.4 SSR Systems SSR System Name The label used to identify a SSR (stud shear reinforcement) system. It usually describes the system, such as stud size. Stud Area Cross sectional area of the stud stem that is used in strength calculations Head Area The area of the stud head, generally about 10 times the stem area. Concept uses this to calculate the head diameter for clear spacing calculations. Min Head Spacing The minimum clear spacing between stud heads along the length of a rail. The design will not succeed if this value is too large. Specified Stud Spacing The desired stud spacing for the SSR design. If set to “none”, Concept automatically designs the stud spacing. Fy The yield stress of the SSR reinforcement. Stud Spacing Rounding Increment Specifies an increment to which all stud designs are rounded down. For example, specifying a larger number forces a larger number of designs to have the same spacing, creating the potential for “grouping” of designs at different columns.

9.2.3 Reinforcing Bars

Min Studs Per Rail Specifies the minimum number of studs that Concept designs on any rail. This can be useful in a number of situations. For example, if one face of a column has a small overhang for which the designer does not want SSR reinforcement, this minimum stud number can be increased to prevent the design of rails on that face.

Bar Name The label used to identify a reinforcing bar. It usually refers to the bar’s diameter.

System Type The type of system to use in the SSR design.

As Cross sectional area of the bar. Es The Young’s Modulus of the bar. Fy The yield stress of the bar. Coating The coating type of the bar (epoxy coating) Straight Ld/Db The development length of straight bars, calculated either by “Code” or a user specified multiple of bar diameter.

9.3 Adding and deleting materials You can add materials to define properties of concrete mixes, PT systems and reinforcing bars. You can delete materials as long as at least one material of each type remains. To add materials:

90 Hook Ld/Db The development length of 90 degree hook bars, calculated either by “Code” or a user specified multiple of bar diameter.


180 Hook Ld/Db The development length of straight bars, calculated either by “Code” or a user specified multiple of bar diameter.

3 In the dialog box that appears, enter a name for the new

2 Click Add Concrete Mix, or Add PT System, or Add

Reinforcing Bar, or Add SSR System. material and click OK. A new row appears at the bottom of the appropriate table. 4 Enter the property value for each cell in the new row.

30

RAM Concept

Chapter 9


• Unbonded systems: greased strand encased in plastic sheathing.

2 Click Delete Concrete Mix, Delete PT System, or Delete

• Bonded systems: bare strand within grouted ducts.

To delete materials:

Reinforcing Bar, or Delete SSR System. A dialog box appears with a list of the available materials. 3 Choose the material to delete and click OK.

Strands are typically comprised of seven wires spirally wound. There are two dominant strand sizes used in building construction: • 0.5 inch diameter (12.7 mm) • 0.6 inch diameter (15.2 mm)

9.4 About post-tensioning systems

For further discussion on post-tensioning systems, see Chapter 26, “Defining Tendons”.

There are two types of systems considered in RAM Concept.

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Chapter 9

32

RAM Concept

Chapter 10

10 Specifying Loadings A loading is a set of point, line and area loads applied as a group. You define loading properties in the loadings window. You draw the actual loads on the loading plans. Loadings can be added (e.g. seismic, snow, soil and wind). Loadings can be deleted (other than those of a special type, as described in “About loading types” below). RAM Concept can perform pattern (or skip) loading and you define the factors that control this process in the loading window.

Live (Parking) Loading Live (Roof) Loading Different sets of live loads. See “About loading types” on page 34 for further description. Snow Loading The snow loads on the structure. Service Wind North Loading The set of wind loads in the north-south direction (for mat defaults only). Service Wind East Loading The set of wind loads in the east-west direction (for mat defaults only). Ultimate Seismic North Loading The set of seismic loads in the north-south direction (for mat defaults only).

10.1 About default loadings RAM Concept provides default loadings for self-weight, post-tensioning and gravity loads. For mat files, Concept provides additional default loadings for wind and seismic. Self-Dead Loading This is the self-weight of the concrete. All other dead loading is superimposed. Balance Loading Post-tensioning tendons and anchors apply internal loads to the concrete structure. We call this set of loads the Balance Loading because you normally design the post-tensioning to balance or offset the other loadings applied to the slab.

Ultimate Seismic East Loading The set of seismic loads in the east-west direction (for mat defaults only).

10.2 Viewing the loadings The Loading window lists the different loadings and their type and pattern factors. To view the Loadings:

1 Choose Criteria > Loadings. 2 If there are many loadings, scroll down to view them all.

Hyperstatic Loading The hyperstatic loading is a theoretical loading that considers the restraining effect of the supports on the structure as it tries to deform due to the application of post-tensioning. Many people use the term “secondary” in place of “hyperstatic”. The loading is not necessarily secondary in nature. Concept calculates the effects of the hyperstatic loading for all objects (elements, springs, supports, design sections, design strip segments and punching checks) as described in “Post-tensioning loadings” on page 386. Temporary Construction (At Stressing) Loading This set of superimposed loads applies before stressing of post-tensioning tendons. This loading is rarely used, and you need not consider it for RC structures. Other Dead Loading This set of superimposed dead loads applies to PT structures after stressing of posttensioning tendons. It is simply the superimposed dead loads for RC structures. Live (Reducible) Loading Live (Unreducible) Loading

Figure 10-1 Loadings Window

10.3 Loading properties Loadings have the following properties: Loading Name The label used to identify the loading. Loading Type See “About loading types” on page 34 for more information.

Live (Storage) Loading

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33

Chapter 10 Analysis The type of analysis, which can be Normal, Hyperstatic or Lateral SE.

Dead Loadings of this type contain permanent dead loads other than those from the self-weight type.

A Hyperstatic analysis is used for only the Hyperstatic Loading described in “About default loadings” on page 33.

Live (Reducible) Loadings of this type contain typical floor live loads that are reducible. See Chapter 52, “Live Load Reduction Notes” for detailed information regarding how each live load reduction code handles loadings of this type.

For information on Lateral SE, see “Self-equilibrium analysis” on page 387 of Chapter 50, “Analysis Notes”. On-Pattern Factor The factor that applies to loads that are located within the loading pattern when performing pattern-loading calculations. See “About load pattern” on page 36 for more information. Off-Pattern Factor The factor that applies to loads that are not located within the loading pattern when performing pattern-loading calculations.

Note: Concept ignores the pattern factors if both factors are the same value. Setting both factors to 2.0 is identical to setting both factors to 1.0

10.4 About loading types Every loading in RAM Concept has a loading type. Concept uses loading type to generate the appropriate load combinations from the defined set of loadings, and to apply appropriate live load reductions. See “Rebuilding load combinations” on page 39 for information on how Concept generates load combinations.

10.5 Available loading types The available loading types are: Self-Weight The structure’s concrete self-weight loads are always generated with this loading type. There is always one and only one loading of this type. Balance As described in “About default loadings” on page 33. There is always one and only one loading of this type. Hyperstatic As described in “About default loadings” on page 33. There is always one and only one loading of this type. Stressing Dead Loadings of this type contain superimposed loads applied before stressing of posttensioning tendons. This loading type is rarely used and is generally not considered for other loading conditions. You need not consider it for RC structures.

34

Live (Unreducible) Loadings of this type contain typical floor live loads that are not reducible (typically assembly loadings - see “About assembly loads” on page 35). Live (Storage) Loadings of this type contain typical floor live loads that are reducible using special storage loading reduction rules. Live (Parking) Loadings of this type contain typical loads for parking garages or car parks. Live (Roof) Loadings of this type contain typical roof live loads - except snow - that are reducible. RAM Concept never reduces these loads (the RAM Structural System may reduce these loads). Snow Loadings of this type contain typical snow loads. They generally do not consider drift or exceptional circmstances, and they may be characteristic or design loads. See the specific code chapters for further details. Other Loadings of this type contain loads of an unspecified nature. RAM Concept never considers these loadings except in manually created or edited load combinations (or load combinations created in previous files). All loading from FLOOR versions 2.3 and before, and RAM Concept versions 1.3 and before (except self-dead, balance and hyperstatic) are given this type; it is often useful to change the loading types of these loadings from earlier program versions. Service Wind Loadings of these types contain wind loads at service force levels. Service Wind Loading N is assumed to correspond to Ultimate Wind Loading N (if it exists). Ultimate Wind Loadings of these types contain wind loads at ultimate force levels. Ultimate Wind Loading N is assumed to correspond to Service Wind Loading N (if it exists). Service Seismic Loadings of these types contain seismic loads at service force levels. Service Seismic Loading N is assumed to correspond to Ultimate Seismic Loading N (if it exists). Ultimate Seismic Loadings of these types contain seismic loads at ultimate force levels. Ultimate Seismic Loading N is assumed to correspond to Service Seismic Loading N (if it exists).

RAM Concept

Chapter 10 Most of these loading types are also available in a “transfer” variation. See “About Transfer Loading Types” on page 35 for more information.

Note: All loading types except self-weight, balance and

10.6 Changing Loading Types The type of any loading (except Self-Dead, Balance and Hyperstatic) may be changed in the Loadings window.

hyperstatic may be used for more than one loading. To change a loading type:

10.5.1 About assembly loads Assembly loadings deserve special consideration Assembly loads It is recommended that, in order to get the appropriate factors, you assembly loads on a Live (Unreducible) layer. Refer to the live load reduction section listed below for detailed information regarding how a specific code handles loadings of this type: • “ACI318-99 / ASCE-7 / IBC 2003 live load factors” on page 431

1 Choose Criteria > Loadings. 2 Click the loading type of the loading name.

A drop down menu appears. 3 Select the new loading type.

10.7 Changing Analysis The analysis of any loading (except Self-Dead, Balance and Hyperstatic) may be changed in the Loadings window.

• “ACI318-02 / ASCE-7 / IBC 2003 live load factors” on page 449

To change an analysis:

• “AS3600 / AS/NZS 1170.1 live load factors” on page 527

2 Click the analysis of the loading name.

• “BS 8110 / BS 6399-1 live load factors” on page 558 • “IS 875 (Part 2) - 1987 Live Load Reduction” on page 413 • “National Building Code of Canada 2005 Live Load Reduction” on page 413

10.5.2 About Transfer Loading Types Almost all of the loading types previously discussed are available with a “transfer” variation. The transfer variations represent loads transferred from the structure above onto the level under consideration (via columns or walls). A few loading types are not available with a transfer variation, or have a somewhat different meaning with a transfer variation. These are: Self-Weight There is no transfer variation of this loading type. Balance The transfer variation of this loading type is for loads generated by the tendons in the structure above the level under consideration. Unlike the non-transfer balance type: multiple loadings of this type may exist; the loadings do not contain loads generated from the tendons; and the loadings of this type are user-editable. Loadings of this type are considered in the calculation of hyperstatic effects. Hyperstatic There is no transfer variation of this loading type. Stressing Dead There is no transfer variation of this loading type. RAM Concept

1 Choose Criteria > Loadings.

A drop down menu appears. 3 Select the new analysis.

10.8 Adding and deleting loadings At times, you may wish to add loadings such as seismic or snow. Conversely, you may choose to delete loadings such as Temporary Construction (At Stressing) Loading. To add a loading:

1 Choose Criteria > Loadings. 2 Click Add Loading. 3 Enter a name for the new Loading in the Add Loading

dialog box and click OK. The new loading appears in a row at the bottom of the table. 4 Enter the Loading Type and Analysis for the new loading. 5 Enter the On-Pattern Factor and Off-Pattern Factor for

the new loading. To delete a loading:

1 Choose Criteria > Loadings. 2 Click Delete Loading.

A dialog box appears with a list of the current loadings. 3 Choose the loading to delete and click OK.

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Chapter 10

10.9 About load pattern In structural engineering, pattern loading refers to a load arrangement that ignores or reduces loads on selected spans for the purpose of maximizing moments, shears or reactions. In 2D analysis, it is not difficult to create an algorithm that determines the important patterns, but this is extremely difficult for a 3D program, especially for irregular column layouts and panels. To handle pattern loading, RAM Concept uses the concept of load patterns.

Note: Some refer to pattern loading as skip loading. 10.9.1 How load patterns work A load pattern creates a (invisible) pattern loading that contains only filtered loads for each standard loading. The On-Pattern and Off-Pattern factors control the filtering. The inclusion and exclusion of loads within the pattern area defines the pattern loading. Concept multiplies loads inside the pattern area by the on-pattern factor and multiplies loads outside the pattern area by the off-pattern factor. The actual pattern area is dependent upon the finite element mesh. See Chapter 21, “Creating Pattern Loading”, for further explanation. On-Pattern areas (shaded) for 6-panel slab:

Figure 10-3 Load Pattern for maximum negative moment (about Y-Y) at first interior column.

For the figures above, if the live load is 100 psf, the onpattern factor is 0.8 and the off-pattern factor is 0.1 then two pattern loadings are created with a load of 80 psf on the hatched areas and a load of 10 psf on the remainder of the slab. Concept uses the load patterns for a loading - along with the full loading - to determine the design force envelopes for design strip segments, design sections and punching checks.

10.9.2 When to use load pattern Whether you use pattern loading is a matter of which code you are using and your engineering judgment. Some codes allow you to ignore pattern loading for certain types of structures and magnitudes of live loading. Common sense should lead you to logical load patterns that produce very close to the maximum moments, shears and reactions. In most circumstances, you only pattern the live loading. There could be circumstances where you pattern other loadings.

Figure 10-2 Load Pattern for maximum positive moment (about Y-Y) in end span

For patterned loads, the on-pattern factor often has a value of 0.75 and the off-pattern factor often has a value of zero. For non-patterned loads, both factors should be 1.0. In special circumstances, the on-pattern factor can exceed a value of 1.0. When in doubt, all on-pattern and off-pattern factors should be 1.0. This results in no pattern loading. See Chapter 21, “Creating Pattern Loading”, for further discussion.

10.9.3 How load pattern can approximate moving loads You can approximate moving loads by using load patterns.

36

RAM Concept

Chapter 10 To approximate moving loads:

1 Specify an on-pattern factor of 10 and an off-pattern

factor of zero. 2 Specify load factors (in the load combinations window)

for the “moving” loading of one-tenth their actual values. 3 Define the movement using the load patterns.

RAM Concept

4 Draw the load once in each pattern.

Note: Concept still analyses a load combination with all the loads present that is included in the envelope. This is the reason for scaling the on-pattern, off-pattern and load factors - it diminishes the effect of the “all the loads” load combination.

37

Chapter 10

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RAM Concept

Chapter 11

11 Specifying Load Combinations A load combination is a factored linear combination of loadings. Strictly speaking, we should call it “loading combination”, but we have adopted the commonly used terminology.

2 If there are many load combinations, scroll down to view

them all.

11.1 About default load combinations Codes generally specify which loadings you need to consider in the design of a structure and how you should combine these loadings. RAM Concept’s default load combinations depend on how you created the file. When you use a template or an existing file then the default load combinations are those of the source. When you create a file using the New command the default load combinations depend on the code selected. These load combinations are usually appropriate for the selected code, but there may be times when you need to modify the load factors and add loadings. The default load combinations for each code are described in detail in the relevant chapter: • Chapter 54, “ACI 318-99 Design”

Figure 11-1 Load Combination Window

• Chapter 55, “ACI 318-02 Design” • Chapter 56, “ACI 318-05 Design” • Chapter 57, “ACI 318-08 Design” • Chapter 58, “ACI 318-11 Design” • Chapter 59, “AS 3600-2001 Design” • Chapter 60, “AS 3600-2009 Design” • Chapter 61, “BS 8110: 1997 Design” • Chapter 62, “IS 456 : 2000 / IS 1343 : 1980 Design” • Chapter 63, “EN 1992-1-1:2004 (Eurocode 2) With TR43 Design ”

11.3 Rebuilding load combinations At times, you may wish to rebuild an existing load combination that includes a new or revised loading. For example, if a loading’s type changes, it affects the load factors and live load reduction process. You can account for these changes by using the rebuild command. RAM Concept will not automatically update load factors when a loading's loading type changes. RAM Concept only sets the load factors when rebuilding load combinations.

• Chapter 64, “CSA A23.3-04 Design” To rebuild load combinations:

1 Choose Criteria > Rebuild Load Combos

11.2 Viewing the load combinations The Load Combinations window lists the different load combinations and their design criteria and load factors.

Another dialog box appears that requires you to specify if the load combinations are for an elevated slab or mat foundation. 2 Select elevated slab or mat foundation 3 Select Rebuild

To view the Load Combinations:

1 Choose Criteria > Load Combinations.

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Chapter 11

11.4 Adding and deleting load combinations At times, you may wish to add load combinations such as seismic plus dead or snow plus dead. Conversely, you might choose to delete load combinations such as Temporary Construction (At Stressing) LC. To add a load combination:

1 Choose Criteria > Load Combinations. 2 Click Add Load Combination. 3 In the dialog box that appears, enter a name for the new

load combination and click OK. Another dialog box appears that requires you to specify the plans that you want RAM Concept to create (Slab Stress, Slab Deflection and Slab Force). These plans appear in the new load combination’s folder.

Analysis Type The choices are: • Linear: this is the standard type. • Zero-Tension: these load combinations do NOT have alternate load factors and never consider pattern loading. Active Rule Sets These control which rule sets are used for design calculations. Up to six active rule sets can be associated with each load combination. See Chapter 12, “Selecting Design Rules” for further explanation. Load Factor The factor applied to a particular loading in the load combination. Alternate Envelope Factor You should only use these if you fully understand the principle involved. Do not set these factors to zero without understanding their use. If you are unsure then set them to equal the corresponding load factors. See “About alternate envelope factors” on page 41.

4 Choose the plans that you want created and click OK.

The new load combination appears at the bottom of the window.

11.6 About group load combinations

5 Select the active rule sets. 6 Enter the load factors and the alternative load factors for

each loading in the load combination. To delete a loading:

1 Choose Criteria > Load Combinations. 2 Click Delete Load Combination.

A dialog box appears with a list of the current load combinations. 3 Choose the load combination to delete and click OK.

11.5 Load combination properties Load Combination Name The label used to identify the load combination. Combo Type The choices are: • Single: this is the standard type.

A group load combination has load factors for every nonlateral loading and for one single lateral loading type. Effectively, a group load combination's results are the envelope of all the results from N invisible single load combinations, where N is the number of loadings for the given lateral loading type. A linear group load combination has a standard and alternate load factor for every non-lateral loading, and a standard and alternate load factor for the selected lateral loading type. It never has zero tension iterations. A zero-tension group load combination has a single load factor for every non-lateral loading, and a single load factor for the selected lateral loading type. It has zero-tension iterations as necessary for invisible (internal) component load combo, and will be the envelope of all of the component load combos combined. It never considers pattern loading. Figure 11-2 is intended to explain the ramifications of load combination type selection.

• Lateral Group: this is used for a floor that is part of the lateral force resisting system [especially mat foundations (rafts)].

Note: The primary purpose of Load Combination types is to reduce the number of lateral load combinations. A secondary purpose is to provide easy enveloping for results such as soil bearing pressure.

40

RAM Concept

Chapter 11 combination, RAM Concept provides a much simpler solution - Alternate Envelope Factors (AEF).

Load Combination TYPE

Point Load

Area Load

Single

Lateral Group

- All loadings are listed - Each loading has load factors - Linear Load Combinations have an Alternate Envelope Factor - Zero-Tension Load Combinations do NOT have Alternate Envelope Factors

- All non-lateral loadings are listed - One, and only one, key loading type can be used (per load combination). - All N loadings within the Key Loading Type are used to generate N load combinations. Figure 11-2 Ramifications of Load Combination Type

Refer to “Summary of load combination types” on page 42 for more information.

Figure 11-3 This beam supports dead loads (not shown) and live loads (shown). The live loading reduces the positive span moment. By using an AEF less than the corresponding load factor, you create a load combination with a reduced live loading. Note that the AEF affects the entire live loading, not just the live load on the cantilever.

Conceptually, Concept considers alternate envelope factors by analyzing the load combination 2L times (where L is the number of loadings) - once for every permutation of load factors and alternate envelope factors for all of the loadings. Concept then envelopes the design strip forces, design section forces and punching shear reactions for all of the load combination analyses. Concept uses these force envelopes later for design purposes. You can also plot the force envelopes or view them in tables. Concept fully considers any pattern loading effects while considering the load factors. Note that the general analysis forces that are not used as design forces by Concept - such as standard slab bending moments and deflections - are only stored for the load combination considering the standard load factors. As stated above, you should only use alternate envelope factors if you fully understand the principle involved. Do not set them to zero without understanding their use. If you are unsure then set them to equal the corresponding load factors.

11.7.1 Example of Alternate Load Factors

11.7 About alternate envelope factors

Figure 11-4 shows the suggested way to use the factors for a strength design of the ACI318-05 Factored LC.

There can be situations where the application of a loading has an unconservative effect on the results. For example • a retaining wall loading that applies compression to a floor. • a cantilever live loading that reduces the internal span moment. In such circumstances, it is desirable to analyze the structure both with and without the full loading. While you could do this by creating an additional load

RAM Concept

Figure 11-4 Factored LC load factors and alternate envelope factors.

41

Chapter 11

11.8 Summary of load combination types

Example 11-1 ACI 318-05 Elevated floor file with lateral loadings added

The effects of using different load combination types and analysis types are summarized in Table 11-1.

To simplify the example, four loadings have been deleted from the standard file.

Linear Single

• Standard and Alternate load factors for every loading • No zero-tension iterations • Considers pattern loading

Group

• Standard and Alternate load factors for every non-lateral loading • Standard and Alternate load factors for the selected lateral loading type • No zero-tension iterations • Considers pattern loading • No results for point springs, line springs, point supports, line supports, walls. • No “Standard” results for any quantity • See Figure 11-2 for more information.

Zero-tension • Standard load factor for every loading • Zero-tension iterations as necessary • Ignores pattern loading • Standard load factor for every non-lateral loading • Standard load factor for the selected lateral loading type • Zero-tension iterations as necessary

Figure 11-5 Loading table for ACI 318-05 Elevated Floor - six wind loadings have been added (and one stressing dead and three live loadings have been deleted)

After adding and deleting some loadings, the load combinations have been rebuilt. See “Rebuilding load combinations” on page 39. The Rebuild operation adds the load combination “Factored Wind LC: 1.2D + f1L+ 0.5Lr + 1.6W”, as shown in Figure 11-6.

• Ignores pattern loading • No results for point springs, line springs, point supports, line supports, walls. • No “Standard” results for any quantity • See Figure 11-2 for more information.

Figure 11-6 Rebuilt load combination: Factored Wind LC: 1.2D + f1L+ 0.5Lr + 1.6W

Concept now expands this load combination and calculates the following load combinations: 1 1.2 Self-dead + 1.0 Hyperstatic + 1.2 Other dead + 0.5 Live

Table 11-1 Load Combination Summary

(reducible) + 1.6 North Wind + 1.6 North Wind (transfer) 2 1.2 Self-dead + 1.0 Hyperstatic + 1.2 Other dead + 0.5 Live

(reducible) - 1.6 North Wind - 1.6 North Wind (transfer) 3 1.2 Self-dead + 1.0 Hyperstatic + 1.2 Other dead + 0.5 Live

(reducible) + 1.6 East Wind 4 1.2 Self-dead + 1.0 Hyperstatic + 1.2 Other dead + 0.5 Live

(reducible) - 1.6 East Wind 5 1.2 Self-dead + 1.0 Hyperstatic + 1.2 Other dead + 0.5 Live

(reducible) + 1.6 Trade Wind + 1.6 Sirocco Wind + 1.6 Zephyr Wind 6 1.2 Self-dead + 1.0 Hyperstatic + 1.2 Other dead + 0.5 Live

(reducible) - 1.6 Trade Wind - 1.6 Sirocco Wind - 1.6 Zephyr Wind

42

RAM Concept

Chapter 12

12 Selecting Design Rules You design concrete floors manually by calculating the resultants (moments, shears and axial forces) of a load combination and applying the appropriate code rules and formula. You select code rules based upon the type of member (reinforced slab, post-tensioned beam, etc.) and the type of load combinations. For example, codes intend some load combinations are for strength design and others for serviceability design.

6 A design summary envelopes the reinforcement require-

ments and section status for all rule set design section envelopes. Example:

The following example describes how RAM Concept selects the ACI 318-02 design rules for a post-tensioned beam with live and wind loadings.

RAM Concept uses a similar method. It sorts code rules into sets of rules and applies them to the resultant envelopes of load combinations. Thus, a rule set design is one or more code rules applied to the resultant envelope of one or more load combinations. For example, the set of code formula for bending and shear strength is the strength rule set. Concept applies this rule set to the envelope of all “factored” (or ultimate) load combinations. The strength rule set does not apply to service load combinations. You design most floors or members for more than one rule set. For example, a post-tensioned floor is usually checked for initial service stresses, service stresses and strength, all with different load combinations.

12.1 Using rule set designs RAM Concept uses the concept of a design strip to link finite element analysis with concrete code rules (see Chapter 22, “Defining Design Strips”). Each design strip’s properties include design system (beam / one-way slab / two-way slab) and the “considered as post-tensioned” option. Design strips contain design cross sections. You assign each load combination active rule set designs in the load combinations window. How RAM Concept utilizes rule set designs:

1 Load combinations generate envelopes for resultants

(moments, shears, axial forces and torsions). 2 All load combination envelopes with the same rule set

design are in turn enveloped. This is a rule set design envelope. 3 For each rule set design envelope, design strips generate

rule set design force envelopes. 4 Each design strip determines which code rules are appro-

Figure 12-1 Example of load combinations and rule sets

RAM Concept’s process is as follows: • The two load combinations generate envelopes for resultants. • The five active rule set designs (service design, code minimum design, user minimum design, strength design and ductility design) each create envelopes from the load combinations. • Each rule set design envelope creates a rule set design section envelope. • The design strip properties of “Structural system: beam” and “consider as post-tensioned” determines the following rules from ACI 318-02 are applicable:

priate for each rule set design. Design strip properties impact which particular rules are used.

• Strength Design: rules 18.7.2 (flexural strength) and 11.4 and 11.5 (shear strength) are used with the beam clauses.

5 Design and checking rules are applied to the rule set

• Minimum Design: rule 18.9.2.

design section envelopes.

RAM Concept

• Service Design: rules 18.3.3 and 18.4.2 (b).

43

Chapter 12 • These rules are applied to the rule set design section envelopes. • The reinforcement requirements and section status for all rule set design section envelopes are in turn enveloped for a design summary.

Ductility Design

Rules intended to produce ductile behavior. Soil Bearing

This is used in mat foundation (raft) files to facilitate the enveloping of soil bearing pressure. It does not use any active rules.

12.2 Rule set design properties The following is a list of rule set design properties: Name This relates to the rule set design. It most cases it is the same as the active rules, but there can be exceptions (see adding rule set designs - below). Active Rules This describes the set of rules applied by this rule set.

12.3 Types of active rules The available ACI 318-02 active rules are: Code Minimum Design

Rules for minimum reinforcement (shrinkage, detailing, etc.) based upon geometry rather than stress or moment level. Does not include shear reinforcement.

12.4 Adding and deleting rule set designs Adding a duplicate rule set design allows you to separate the results for different load combinations with the same active rules. For example, if a strength design is required for three different load combinations (1. Dead and Live; 2. Dead, Reduced Live and Snow; 3. Seismic) then you could keep the results separate by creating two new rule set designs with names such as “Snow” and “Seismic” which both use the code strength rules. This way you can view the strength reinforcement requirements separately. You can delete non-applicable rule set designs to simplify the file. For example, in ACI 318-02, initial service design, and sustained service design are not required for floors without post-tensioning. Another example is DL + 0.25LL Design is not required if the UBC is not used. To add a rule set design:

1 Choose Criteria > Design Rules. User Minimum Design

Reinforcement based on user defined reinforcement ratio. See the design strip property description on page 99 of Section 22.5. Initial Service Design

Checks of PT floor stresses just after application of prestress (when dead load is minimal). Service Design

Checks of PT floor stresses due to service loads.

2 Click Add Rule Set Design. 3 Type a name for the new Rule Set Design in the Add Rule

Set Design dialog box and click OK. A dialog box appears that requires you to specify the plans that you want created (Top and Bottom Reinforcement, Shear Reinforcement and Punching). 4 Choose the plans that you want created and click OK.

The new rule set design appears at the bottom of the window. 5 Select the active rules.

Rules for reinforcement bar based upon bar stress levels. To delete a rule set: Sustained Service Design

1 Choose Criteria > Design Rules.

Checks of PT floor compression stresses due to sustained loads.

2 Click Delete Rule Set Design.

Strength Design

Rules to ensure section has sufficient strength in bending and shear for factored (or ultimate) moments, and minimum shear reinforcement.

44

A dialog box appears with a list of the current rule set designs. 3 Choose the rule set design to delete and click OK.

RAM Concept

Chapter 13

13 Using a CAD Drawing You can define the model’s geometry quickly if there is a CAD file (with .dwg or .dxf filename extension) available to use as a background. You trace the CAD drawing with object tools to facilitate the finite element mesh generation. You can also use the CAD drawing to locate other objects such as loads. Snap tools make tracing the imported CAD drawing easier.

3 Select the appropriate units and click OK.

Note: RAM Concept itself does not recognize the meaning

When you import the drawing file, it will be visible on the Standard Plan of the Drawing Import Layer. You should verify that the plan scale is correct.

of actual drawing lines. It is not necessary, however, to use a CAD file. If the floor is straightforward, or there is no drawing available, you should skip this chapter. For strip-like models that do not warrant the use of a CAD file, it may be better to use Strip Wizard.

Note: It is possible to import a CAD drawing with one set of units into a model with another set of units.

13.1.2 Checking the imported information

To check that the imported drawing is at the correct scale:

1 Choose Layers > Drawing Import > Standard Plan. 2 Click Zoom Extent (

) to ensure that you are viewing

the entire CAD plan. 3 Select the Dimension tool (

13.1 Importing, verifying and viewing a drawing

) and draw a dimension line between two snapable points that are a known distance apart. The distance between the two points will appear as a dimension.

To use a background drawing you import the drawing and then verify that it is at the correct scale.

If this dimension is not as expected then the imported file may be in the wrong scale. Consider importing the drawing with different units to fix this problem.

13.1.1 Importing a CAD file You can import a drawing at any time. An imported drawing overwrites any previously imported drawing. RAM Concept can work with either a .dwg or a .dxf file. It is typically best to use a .dwg file. To import a CAD file:

1 Choose File > Import Drawing. 2 Select the CAD drawing file you want to import.

If Concept cannot determine the units of CAD file, the File Units dialog box will appear with a list of units. The units relate to the CAD file, not the Concept file.

RAM Concept

13.1.3 Making the drawing visible on other plans You can make the imported drawing visible on any plan through the Visible Objects dialog box. Usually you want to make it visible on the Mesh Input Standard Plan (for defining the floor geometry), and perhaps on some loading plans (for locations of line and point loads). You may choose to turn off some CAD layers if they clutter the drawing. If you happened to bring in an architectural drawing, it is probably a good idea to turn off the furniture. See “Controlling views” on page 11 for more information on making objects visible or hidden.

45

Chapter 13

46

RAM Concept

Chapter 14

14 Importing a Database from the RAM Structural System Note: In many places in this chapter the RAM Structural System is referred to as “RSS”.

Import Type Story

RAM Concept can import concrete structure information and loads from the RAM Structural System (Version 9.01 or higher) into a RAM Concept file. RAM Concept can also export support member forces back to RSS.

Elevated

Mat Foundation

1st

A

C

2nd

B

D

Table 14-1 Relationship between the selected story, the import slab type, and the slab area imported.

14.1 What can be imported from the RAM Structural System RAM Concept allows the selective import of concrete members (slabs, beams, openings, columns and walls), applied loads and member loads from one story of a RAM Structural System database. Member loads can be from gravity and / or lateral analyses.

14.2 Controlling which concrete members are imported

14.2.1 Definition of the “import perimeter” The selected slab areas define the import perimeter. Only RAM Structural System support members within the import perimeter will be imported. For example, in Figure 14-1, if the 1st story elevated slab is imported with the “columns above” setting, the two furthermost right columns between the 1st story and 2nd story will not be imported as they are not within the slab perimeter of the 1st story elevated slab. The following structural members can be imported:

1 Slabs

A story defined in the RAM Structural System can have two types of floors: elevated or mat foundation. The floor type designation determines which concrete members in the story are imported.

All slabs of the selected slab type.

Figure 14-1 and Table 14-1 show the relationship between the selected story, the import slab type and the slab area imported. Note that mats are below the designated story. For example, the 2nd story mat is the mat that supports the second story elevated floor.

3 Openings and Penetrations

2 Beams

All concrete beams from the selected story.

All openings and penetrations within the import perimeter. 4 Columns

Any column (below and / or above) whose center point lies inside the import perimeter. 5 Walls

Any wall (below and / or above) whose center line is contained by or crosses any part of the import perimeter. 6 Grids

All orthogonal and radial grids.

Note: All structural members are imported into RAM Concept’s Mesh Input layer. Grids are imported into the Drawing Import layer. Figure 14-1 The slab areas shown above (A,B,C,D) will be imported based upon the selections shown below.

RAM Concept

47

Chapter 14

14.3 About load importation RAM Concept imports applied loads and analyzed member forces from the selected member group. Certain components of member loads are ignored when importing. The components that are ignored depend on the slab type and whether the member forces are from gravity and lateral loads. The following table summarizes the force components that are imported onto a mat foundation and an elevated slab.

Table 14-3 shows how RSS load cases are mapped to Concept loading layers. RSS Load Case RAM Concept Loading Layer Dead

Dead Load

Live

Ignored (imported as 4 individual live loadings)

Live Reducible

Live Reducible

Live Unreducible

Live Unreducible

Live Storage

Live Storage

Live Roof

Live Load Roof

Partition

Partition (imported as “Live Unreducible” type)

Slab Type Loading Type

Forces Imported

Mat

Transfer Gravity

Fz, Mx, My

Mat

Transfer Lateral

Fx, Fy, Fz, Mx, My

Construction Live

Ignored

Elevated

Transfer Gravity

Fz

Mass Dead

Ignored

Elevated

Transfer Lateral

Fz, Mx, My

Construction Dead Construction Dead Load

Table 14-3 Mapping of RSS load cases

Table 14-2 Relationship between the slab type, member loading type, and imported force components for a slab.

Wall forces are resolved into a statically equivalent linearly varying force applied along the length of the wall. The following loads can be imported:

1 Direct gravity loads

Point, line and area gravity loads applied directly to the imported slabs.

2 Transfer gravity loads

Concept imports transferred gravity loads from RSS members above the import slabs. The loads include member self-weight with the transferred gravity loads. The loads are imported as point loads and line loads into separate Concept loading layers. A new Concept transfer gravity loading layer is created for each RSS Load Case, as in Table 14-3, but with the string “(transfer)” appended to the name. For example, transfer loads from the RSS Dead load case are imported into the Concept “Dead Load (transfer)” loading layer. The Concept “(transfer)” loading layers are not created if the Transfer Gravity Loads are not imported. 3 Lateral Member Loads

Lateral member forces (such as wind and seismic) from members above and below the imported slab are imported as point loads. The member loads are imported into a new loading layer for each analyzed load case in RSS. Concept creates the name for the new loading layer from the user's label and the RSS load type. For example, the name could be “mySeismic(EQ_UBC97_X_+E_F)”.

Note: Mat foundation loads imported from the RAM Structural System will always be reduced during the import. For this reason you should always choose the live load reduction code of “None” in these files.

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RAM Concept

Chapter 14

14.4 Importing a database You can import from the RAM Structural System at any time. An import overwrites some or all previously imported data, and may overwrite information you have directly input to RAM Concept. Refer to “Reimporting a database” for more information.

Note: Concept may not be able to import data correctly if the RSS file does not pass the “Data Check” operation in the RAM Modeler module. It is strongly recommended that your RSS file have no errors before attempting to import it into Concept. To import from the RAM Structural System:

1 Choose File > Import RAM Structural System.

If there is no open RAM Concept file the “Open RAM Structural System Database” dialog box will appear. Browse and select a RSS database (.rss) file and click OK. When a valid RSS database file is selected, the RAM Structural System dialog box in Figure 14-2 appears. The RSS filename selected appears after “File:” at the top of the window. You may click on the “Browse” button at the top of the window to select a different file with the file browser.

Note: If you select a file with a version prior to 9.0, an error will be displayed and you will be returned to the file browser. Clicking the Cancel button cancels the import operation. Note: If you are running RSS version 9, select RSS

Figure 14-2 RSS import dialog box

2 Select the story and slab type.

The dialog box makes “Columns Below Slab”, “Walls Below Slab”, “Beams” and “Openings and Penetrations” unavailable for a Mat Foundation.

3 Select the structural members from the check boxes

4 Select the loadings from the check boxes under

database files with the .ram extension.

under “Structure”.

“Loading”. The dialog box makes “Direct Gravity Loads” unavailable for a Mat Foundation. 5 Click OK to import the file, or Cancel to cancel the

import operation. After an RSS file is imported, a RAM Import Status dialog box, similar to that shown in Figure 14-3, appears with a summary and any warnings.

RAM Concept

49

Chapter 14 the loadings that Concept offers to remove. If you want to export the reactions from these pre-existing loads to RSS, you need to copy the loads from the original loadings to the corresponding RSS loadings that are being imported (after which you should manually delete the non-RSS loadings).

Note: If you have used the Export Geometry to RAM Structural System feature (section 36.2) prior to importing, then you always see this warning. The recommended workflow is to either draw the loads in RSS or draw the loads in Concept after importing from RSS; with either of these workflows, you can safely allow the loadings proposed for removal to be deleted.

Figure 14-3 Example of an import summary with warnings

The RSS geometry definitions and loads are now imported into RAM Concept. You can now generate the finite element mesh. See Chapter 18, “Generating the Mesh”.

Note: If you are reimporting there could be additional dialog boxes that appear with more warnings.

Note: Importing lateral analysis loads from RSS models that contain a large number of lateral load cases will cause Concept to create a large number of load combinations which will result in sluggish performance.

Figure 14-4 Choices for dealing with new loadings

RAM Concept will also prompt you to determine if you require rebuilding of the load combinations and design rules, as shown in Figure 14-5. You have three choices: • Rebuild: load combinations and design rules in the RAM Concept file are rebuilt

14.5 Reimporting a database If the information in the RAM Structural System database changes, the RAM Concept model will not be automatically updated. You can, however, reimport the changed information.

• Don’t Rebuild: the new load cases are added to the RAM Concept file, but not included in the load combinations. • Cancel: RAM Concept returns you to the file browser.

Changes to structural members and loads made in RAM Concept can be lost when importing an RSS file, so care should be taken to avoid losing information.

14.5.1 Resolving loading conflicts If the Concept file has existing loadings that do not match the RSS loadings to be imported, a dialog box like that in Figure 14-4 asks if you want to keep or delete the existing loadings. If you have already specified (drawn) loads in the loadings that Concept has proposed to delete, then you should keep 50

Figure 14-5 Choices for dealing with new loadings

Note: When reimporting a particular member type, e.g. beams, all entities of that category are removed from the RAM Concept file before importing. For example, if beams are imported, all beams in the RAM Concept file are

RAM Concept

Chapter 14 removed first. Any beams you have added manually in RAM Concept will be lost. If beams are not selected for import, then beams in the RAM Concept file will not be affected when the file is reimported.

A RSS Import Status dialog box will appear with a summary and any warnings. 5 Click OK.

Note: If any loading categories are selected, then ALL loads in reimported loading layers are removed. Any loads you have added manually on a loading layer being reimported will be lost.You have the option whether to regenerate load combinations or not. RAM Concept always asks you to confirm a reimport operation, because it may lead to loss of information. It warns you if the data to be reimported would be significantly different from the previously imported data, or if significant information will be lost. For example, RAM Concept warns you when reimporting a mat foundation after previously importing an elevated slab, or vice versa. To reimport from the RAM Structural System:

1 Choose File > Import RSS.

A file dialog box will open with the name of the last RSS file you imported into this RAM Concept file. 2 Select the RSS file and click OK.

The file can be a different RSS file which may have a significant (and possibly negative) effect on the RAM Concept model. The RAM Structural System Import dialog box will appear with a list of options. The default options will be the story and slab type from the last import. 3 Select the story, slab type, structure and loading and click

OK. A New Loadings confirmation box may appear that describes loadings in the RSS file that are not in the current RAM Concept file. Click Replace, Add or Cancel. A confirmation box appears that warns about differences from previously imported data.

14.6 Limitations, Defaults and Assumptions

14.6.1 Limitations • Not all information stored in a RAM Structural System database can be transferred into RAM Concept. • RAM Concept models RAM Structural System data using either the ACI 318-99, ACI 318-02, ACI 318-05, AS 3600:2001, Eurocode 2: 2004, CAN/CSA A23.3-04 or BS 8110: 1997 building code. A RAM Structural System database that has live load reduction set to China GB or Hong Kong will be imported using the BS 8110: 1997 building code; a live load reduction setting of NBC of Canada will be imported using the CAN/CSA A23.3-04 standard; otherwise the building code set in RAM Concrete is used to set the RAM Concept code. The building code can be changed, if necessary after the importation is complete. • RAM Concept does not model beam fixity. • RAM Concept models a column end as fixed if the RAM Structural System column is fixed along either its major or minor axis. • RAM Concept only models walls of constant height. RAM Concept will create a wall with the average height of the RAM Structural System wall. • The lateral loads applied to the structure in RAM Frame Analysis are not imported. • Concept ignores holes in walls modeled in RSS version 10.

14.6.2 Defaults RAM Concept uses the following defaults for properties that are not defined in the RAM Structural System. Beams

• Surface elevation is 0.0. Columns Figure 14-6 Examples of warnings for an import operation with different levels and structure type

4 Click Replace or Cancel.

RAM Concept

• Compressible is true. • Roller is false, except above mat foundations. • Columns above mat foundations are pinned at the top regardless of the setting in the RAM database.

51

Chapter 14 Walls

• Neither the top nor the bottom is fixed. • Modeled as a Shear Wall.

RSS Load Case Type

Sub-Type

Wind

User defined Wind story forces

Service *

Wind

all others

Service

Seismic

User defined Seismic story forces

Ultimate *

Seismic

UBC 94

Seismic

Service

Seismic

all others

Seismic

Ultimate

Dynamic

Eigen solution

Ignored

Dynamic

all others

Ignored

• Modeled as compressible. • The RAM Structural System “cracked section factor” is ignored.

14.6.3 Assumptions • All loads are applied to the surface of the slab. • Wall forces are applied as a linearly varying force along the length of the wall that is statically equivalent to the wall forces and moments. Refer to Table 14-4 and Table 14-5 for mapping of RAM load cases and types to RAM Concept’s loadings and force levels.

RSS Load Type

RAM Concept Loading

RAM Concept Loading Force Level (Limit State)

Wind

Wind

Service *

Seismic

Seismic

Ultimate *

Other

Seismic

Ultimate *

Virtual

Ignored

Table 14-4 RAM Modeler Force Level Assumptions

RAM Concept RAM Concept Loading Loading Force Level (Limit State)

Wind

User defined story forces

Seismic

Center of rigidity

Ignored

Virtual Work

Ignored

Ultimate *

Table 14-5 RAM Frame Load Cases

Note: * denotes assumed

14.7 Tight integration with the RAM Structural System

Note: * denotes assumed Starting with version 14.5, the RAM Structural System can be used to control the model data exported, run Concept, and manage the Concept data file as part of the RSS model file. Selection of the data to be imported into Concept is very similar to that described here. For more information, refer to the RSS Structural System documentation. Concept executes in a restricted mode when it is run from RAM Manager. The following operations are disabled: • New • Open • Close • Save As • Save Template • Strip Wizard • Sync ISM / New from Repository • All Sync RSS Operations • All Sync STAAD Operations

52

RAM Concept

Chapter 14 These restrictions are in place primarily to maintain the integrity of the Concept files when they are imbedded in the RSS model file.

RAM Concept

53

Chapter 14

54

RAM Concept

Chapter 15

15 Data Transfer from STAAD The STAAD analysis and design program can transfer structure geometry and loading information to RAM Concept.

STAAD starting Concept, the dialog box shown in Figure 15-1 opens.

15.1 STAAD Interface In STAAD, you can select slabs elements, wall elements, column elements and beams for export into RAM Concept. You can also select STAAD load cases for export and associate them with Concept loading types. The STAAD interface allows you to either run Concept immediately with the exported data or to save the data to a GCFF file for later import into Concept. If the STAAD file changes (perhaps loads or column sizes change), you can update the Concept file by re-exporting the STAAD information. Please see the STAAD manuals for more information on the STAAD interface.

15.2 RAM Concept Interface Figure 15-1 File options dialog box

15.2.1 Data Transfer Paths RAM Concept can import STAAD information in four ways: 1 Concept is started by STAAD to create a new file. 2 Concept is started by STAAD to update a previously

created file.

The options at the top of the dialog window are the same as for creating any new Concept file and are not discussed further here. The checkboxes at the bottom of the window allow you to import one or more of the following classes of information: slabs (including beams), walls, columns and loads.

3 The Concept File menu item New From STAAD GCFF

file is chosen to create a new file. 4 The Concept File menu item Update from STAAD GCFF

file is chosen to update an already opened Concept file.

15.2.2 New file options in RAM Concept

15.2.3 Update file options in RAM Concept When updating a Concept file with new STAAD information - either via the Update From STAAD GCFF file menu item or by STAAD starting Concept, the dialog box shown in Figure 15-2 opens.

When creating a new file from STAAD information - either via the New from STAAD GCFF file menu item or by

RAM Concept

55

Chapter 15 behave slightly differently due to the operation being an “update”. For example if “Columns” is selected, all existing columns will be removed and new columns defined by the STAAD information. If “Columns” is not selected, no changes will be made to the columns in the Concept file.

Figure 15-2 Update file options dialog box

The options in the window are the same as those discussed in “New file options in RAM Concept” on page 55, but

56

RAM Concept

Chapter 16

16 Data Transfer from ISM RAM Concept can exchange structure information with Bentley’s Integrated Structural Model (ISM) technology.

16.1 What is ISM? Bentley’s Integrated Structural Model (ISM) is a technology for sharing structural engineering project information among structural modeling, analysis, design, drafting and detailing applications. ISM is similar to Building Information Modeling (BIM), but focuses on the information that is important in the design, construction and modification of the load bearing components of buildings, bridges and other structures.

16.1.1 Purpose There are two related purposes for ISM: • The transfer of structural information between applications. • The coordination of structural information between applications. To provide for transferring information, ISM provides a means of defining, storing, reading and querying ISM models. To provide for coordination of information, ISM can detect differences between ISM models, allowing you to selectively update either an ISM repository or an application’s data. This gives you control over the consistency between the two data sets.

16.2 ISM Sync Tools Overview Concept can send structural data to and from an ISM repository through a set of ISM Synchronizing tools. These tools allow you to both create and update Concept models as well as ISM repositories. These flexible tools also allow you to create models and move data as your workflow dictates. There are four ISM operations: • Create ISM repository: creates a new ISM repository from the model currently open in Concept. • Create Concept file: creates a new Concept model from an existing ISM repository. • Update ISM repository: transfers changes made to the current Concept model into an existing ISM repository, and allows you to accept some or all of those changes. • Update Concept model: transfers changes made to the ISM repository into the current Concept model, and allows you to accept some or all of those changes. When the Update operations are executed, the Change Management environment is invoked to coordinate which changes are to be reflected in the models and repository. Create ISM Repository:

To create an ISM repository from a Concept model: 1 Choose File > Sync ISM > Create repository. Select the

repository file and click OK. 2 The “Export Story” dialog will appear, as in Figure 16-1.

16.1.2 ISM and Application Data ISM is not intended to store all of the information that all of its client applications contain. Rather, it is intended to store and communicate a consensus view of data that is common to two or more of its client applications, such as Concept. Concept continues to hold and maintain its own private copy of project data. Some of Concept’s data will duplicate that of the associated ISM repository. Concept’s data may even conflict with that in the ISM repository. Concept (or you as its user) may decide that maintaining conflicting data is best for Concept’s and ISM’s different uses.

Figure 16-1 ISM Export Dialog

3 Enter a story name and elevation, and click OK. The

story name and elevation are both required. 4 If the Extended UI checkbox is enabled, the ISM Change

Management environment will be executed, enabling manual inspection and filtering of the items to be exported. Create Concept File:

To create a Concept File from one story defined in an ISM repository:

RAM Concept

57

Chapter 16 1 Choose File > Sync ISM > New from repository, as in

4 Select the file's structure type, code and units.

Figure 16-2.

5 Select the story to be imported under “ISM Story” and

click OK. If the Extended UI checkbox is enabled, the ISM Change Management environment will be executed, allowing you to manually inspect and filter the items to be imported. Update ISM Repository:

To update the ISM repository with changes made to the Concept file, choose File > Sync ISM > Update repository. The ISM Change Management environment will appear, giving you control over each change to the repository. If the ISM repository cannot be found, you are given the opportunity to select its new location or cancel the operation. Update Concept Model:

Figure 16-2 New from Repository Menu

2 Select the ISM repository file and click OK 3 The “New File” dialog will appear, as in Figure 16-3.

To update the Concept File with changes made to the ISM repository, choose File > Sync ISM > Update from repository. The ISM Change Management environment will appear, giving you control over each change to the Concept file.

16.3 Import and Export Details It is useful to describe here the differences between the ISM and Concept models, the conversion process, and how the Concept model is modified to make the conversion process smoother.

16.3.1 Filtering The ISM model is very general. It can represent diverse structure types, such as buildings and bridges, and material types like steel, wood and concrete. Concept filters out any part of the ISM repository that it does not model or is not relevant. The Update operations use the filtered model to determine the context of the changes to be applied. For example, Concept filters out all steel members. When Concept updates the ISM repository, it does not need to replicate steel members in the model. The Change Management can deduce that Concept is not deleting the steel members because it never read them in. The Concept filter retains only the following objects from the ISM model: • The imported story information Figure 16-3 New File from ISM Dialog

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• Concrete slabs, footings and beams on the imported story

RAM Concept

Chapter 16 • Concrete walls and columns that are connected to the slabs or beams retained • Static Load Cases and their loads that are applied to the slabs or beams retained

Concept and ISM use slightly different terminology for structural members and loading types. Table 16-1 is a cross-reference of Concept and ISM type names. Concept Name

ISM Type(/Use)

N/A

Story

• Concentrated and Area surface rebar in slabs

Concrete Mix

Concrete

• Layer parallel rebar inside and parallel to a beam

Slab Area

Surface Member/Slab or Surface Member Modifier

Slab Opening

Surface Opening

Beam

Curve Member/Beam

• Non-planar slabs, walls and surface loads

Column

Curve Member/Column

• Sloped slabs

Wall

Surface Member/Wall

• Modifiers and openings in walls

Loading

Load Case

• Beams, columns and curve loads with geometry not equivalent to a single line segment

Point Load

Point Load

Line Load

Curve Load

Area Load

Surface Load

N/A

Section

Rebar

Rebar Material

• Concrete materials and curve member Sections that are used by the members retained

• Rebar materials used by imported rebar Concept ignores the following ISM objects:

• Beams and columns that do not have the Orientation, Section, and SectionPlacementPoint properties set • Beams with a non-vertical Orientation • Duplicate Load Cases that correspond to fixed Concept loadings

Concentrated Rebar Concentrated Surface Rebar

• Hyperstatic or Inset Load Case Cause

Distributed Rebar

Area Surface Rebar

• Rebar in walls or columns

Transverse Rebar

Perpendicular Rebar

• Non-horizontal rebar

Table 16-1 Concept and ISM Type Name Cross-Reference

16.3.2 The ISM Model ISM structure models consist of multiple stories. Each slab or beam is “on” exactly one story. Wall and column members may extend through multiple stories and are connected to slab and beam members. Load Cases contain point, line and area loads that are applied to exactly one member.

16.3.3 Slabs and Openings ISM and Concept model slab areas differently. It is instructive to describe the differences in detail here to explain how the import and export operations are affected. Concept slabs are defined by a collection of slab areas and openings with arbitrary overlapping polygonal boundaries. Each slab area defines material, thickness and surface elevation properties. An integer priority determines which slab area or opening takes precedence where two or more slab areas overlap. ISM slabs are defined by a collection of surface members with polygonal boundaries. Each surface member may contain any number of surface member modifiers. The

RAM Concept

59

Chapter 16 surface member and its modifiers define the slab material, thickness and surface position properties. Modifier boundaries must lie inside the parent surface member's boundary. Modifier boundaries may overlap, so modifiers have an integer priority to determine precedence in overlapping areas. Modifiers always take precedence over the parent surface member. Normal practice is for modifier priorities to be sequential, starting at 1. A surface member may also contain any number of surface member openings. Like modifier boundaries, opening boundaries must lie within the parent surface member's boundary and may overlap. However, openings always take precedence over the surface member and its modifiers. In effect, surface members have an infinitely low priority, surface member modifiers have an explicit integer priority, and openings have an infinitely high priority.

Note: We use the term effective shape to mean the surface member boundary minus all of its openings. This shape is not necessarily polygonal. Although not common, it may have holes and islands. The effective shape may also be disjoint if surface member openings split it into pieces. We also use the term outer boundary of an arbitrary shape. This is the shape with all interior holes filled. It may consist of more than one disjoint shapes, but each shape will be polygonal. Therefor, ISM surface member boundaries may overlap, as long as there is no overlap between the surface member effective shapes.

Importing ISM Slabs to Concept

Converting a single ISM surface member into a set of Concept slab areas and openings is straightforward. The surface members and surface member modifiers are converted to Concept slab areas. The openings are converted to Concept openings. The slab area created from the surface member is assigned a priority of 0. The openings are assigned a priority of 90. The slab areas created from the surface member modifiers are assigned priorities in the range 10-89, with an increment of at least 2. Modifier priorities are compressed where possible, e.g. where two non-overlapping modifiers may be set to the same priority. A surface member that overflows this range (i.e. it contains modifiers in a configuration that requires more than 45 distinct modifier priorities) should be very rare. In this case, some of the modifiers will have duplicate priorities. The user will need to fix this model in the Concept modeler and then update the ISM repository. The priority mapping is applied to each surface member on the story. If the boundaries of surface members overlap, it should only be in the opening of one surface member. The priorities of the slab areas and openings of the overlapping

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surface member are offset by a multiple of 100 to make the Concept model unambiguous. Exporting Concept slabs to ISM

Converting overlapping Concept slab areas and openings to ISM surface members with modifiers and openings is more complicated. The Concept model should map directly to ISM surface members to make ISM repository creation and update operations go smoothly. The Concept slab area and opening geometries and priorities must sometimes be modified. If necessary, the lowest priority Concept slab area is expanded to contain overlapping slab areas and is then converted to a parent ISM surface member. Overlapping slab areas are converted to surface modifiers of the parent surface member. Concept slabs that do not overlap are converted into separate ISM surface members. Any Concept slab that does not have any effect on the slabs it overlaps is not converted to an ISM modifier. ISM surface openings effectively have an infinite priority. In order to model ISM surface openings, any Concept slab openings that are obscured by higher-priority slab areas are first trimmed to their effective shape. New slab openings are added to the Concept model if the trimming operation splits an opening into two or more pieces. Openings that are completely obscured by higher-priority slab areas are not added to the ISM model. The slab areas and slab opening priorities are compressed and reassigned as described for importing ISM surface members. You will be notified when the shape or priority of a Concept slab area or opening is changed or when openings are added or removed. You can stop the ISM operation at any point and the Concept data will not be changed. Small Features

Changing the shape of a slab can sometimes introduce small features that are not detected until the model is meshed. For example, the corner of a drop cap might extend slightly past the edge of the lowest priority slab. When the lowest priority slab is extended to contain the drop cap, it may have a very small (< 50 mm) edge. The “Line too short” (39.1.2) or “Feature eliminated” (39.1.3) warnings will be generated when meshing the model. Removing these features will generally not hurt anything, but it is best to fix them manually in Concept and update the ISM repository to eliminate future warnings.

16.3.4 Slab Modeling Guidelines Almost any Concept slab model can be converted to an equivalent ISM model. Following these modeling guidelines in Concept will reduce the chance of problems in model consistency. RAM Concept

Chapter 16 • Drop Caps and Panels, on the interior or exterior, should not be modeled by adding openings to a slab and filling them with other slabs. Instead, increase the priority on the drop panel slabs so that they override the base slab. • Slab area islands can be handled properly if modeled with care. A slab area island is completely contained within, and higher priority than, a slab opening. The slab opening is contained within or on the edge of, and higher priority than, another slab area. If the island slab area does not overlap the outer slab area's effective shape, it will converted into a separate ISM surface member. The preferred ISM model is a surface member with an opening and a modifier. This can be accomplished by splitting the opening so that it surrounds the island slab without covering the larger slab. If the Concept slab is constructed with openings whose priorities are larger than all of the slab areas, then it will map correctly to the ISM surface member.

16.3.5 Support Members ISM wall and column definitions are much more flexible than Concept’s. However, because most building structures have regular features such as vertical columns, this normally won’t be a significant issue. An ISM repository models an entire building. Support members may extend through all stories of the building and be connected to members on each story. ISM walls are surface members; they may be as complex as slabs, with openings, arbitrary shapes and thickness variations. Walls and columns can also be sloped. On the other hand, Concept only models vertical support members, and their height is assumed to extend just to the next slab above or below. Concept walls are rectangular and openings are not supported. Importing ISM Support Members to Concept

Concept imports only ISM support members that are connected to a slab or beam that is on the story imported. Concept creates one or two support members above and below the imported slab. Concept models the support member height from the imported story to the next connected slab or beam above (or below), or to the end of the member if it is not connected to another story above (or below). If the ISM support member ends at the imported story or the next connected story, Concept models the complete support height to that end. If the support member does not terminate on one of these stories, the Concept member height is modeled from the elevation midpoint of all slabs and beams connected to it on that story. Concept will not create support members shorter than 500 mm for cases where the member extends only a short distance past the import story. If the ISM support member is sloped, Concept models the sloped length of the member, RAM Concept

not the difference in elevation of ends (i.e. the modeled height will be greater than the elevation difference). For example, consider a column that is connected to a slab on the imported story and stories above and below, and ends on the stories above and below. The column heights will be computed relative to the elevation midpoint of the imported slab. If a drop cap or deep beam is added to the imported slab and connected to the column in the ISM repository, the elevation midpoint imported slab will shift downward. When the Concept model is updated, the Concept column height above will increase and the column height below will decrease by equal amounts. Exporting Concept Support Members to ISM

When exporting support members to ISM, pairs of matching support members at the same location are merged to create a single ISM support member. Two support members are merged only if all of their properties match (e.g. Concrete mix, thickness, etc.), and either they were imported from the same ISM support member, or they are both new in Concept. If a pair of support members at a location cannot be merged, then two ISM support members are exported. The support member exported by Concept extends only to the ends of the heights modeled in Concept, relative to the center of the slab or beam the support member passes through. Dealing with this geometry approximation requires some care when updating Concept or ISM. When updating Concept from ISM, the Concept model may have shortened support members. In general, the ISM geometry can be accepted to capture changes made to the repository, and Concept will just create a new approximation. There are times when you should reject changes to the Concept support member geometry. For example, when the Concept support member geometry has been adjusted to compensate for a problem in the Concept approximation. In those cases, the Reject setting in the Changes Management environment will prevent the Concept geometry from changing. It is usually not desirable to update the ISM repository with the approximate Concept support member geometry. For this reason, updating the ISM repository support member is disabled by default. See 16.3.10 for information on enabling updates to support members. If updating support members is enabled, you can decide which properties should be changed. The support member geometry – defined by the Location or Boundary properties – can be updated for simple one or two story support members. Changes to Concrete mixes, dimensions or column orientation can also be updated.

16.3.6 ISM Section Shapes ISM supports a wide array of section shapes, including parametric sections, custom section shapes, composite

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Chapter 16 sections and linearly varying sections. Concept supports only two section shapes: solid rectangles for beams and solid rectangles or circles for columns. Concept must therefore create a rectangular or circular approximation for any non-rectangular or non-circular ISM section shape. ISM Parametric Sections use a small number of parameters to define the most common section shapes. For column members, Concept maps solid and hollow circular ISM parametric section shapes to solid circles. All other parametric shapes for beams and columns are approximated by rectangles. Table 16-2 shows the width and height the Concept rectangular section approximations for each ISM Parametric Section Type:

16.3.7 ISM Load Cases and Loads ISM Load Case objects and their Load Cause property are analogous to Concept Loadings and their Loading Type property. Table 16-3 gives the Concept Loading Type imported for each ISM Dead Load Cause. Ism Load Cause Concept Loading Type DeadConstruction

Stressing Dead

DeadStructure

Other Dead

DeadSuperimposed

Other Dead

DeadUnspecified

Other Dead

Table 16-3 Concept Dead Loading Types Imported

ISM Parametric Concept Width Section Type

Concept Height

Solid Rectangle

Width

Height

Hollow Rectangle

Width

Height

Ism Load Cause

Concept Loading Type

Solid Circle

Outer Diameter

Outer Diameter

FloorAssembly

Live Unreducible

Hollow Circle

Diameter

Diameter

FloorOffice

Live Reducible

I

Web Thickness

Depth

FloorResidential

Live Reducible

T

Web Thickness

Depth

FloorRetail

Live Reducible

L

Thickness

Depth

FloorStorage

Live Storage

C

Web Thickness

Depth

FloorUnspecified

Live Reducible

Double L

2*Thickness

Depth

ParkingHeavy

Live Parking

ParkingLight

Live Parking

ParkingUnspecified

Live Parking

Table 16-2 Rectangular Section Approximations to ISM Parametric Section Shapes

ISM also defines Custom, Built Up and Varying section shapes. ISM Custom sections are defined by an arbitrary geometric shape. Concept approximates Custom sections by a square of the same area. ISM Built Up sections are composites of other parametric or custom sections. Concept approximates Built Up sections by a square with the area of the sum of the areas of the section's components. ISM Varying sections vary shape linearly along a member. Concept approximates a Varying section shape by applying the rules for constant sections to the start of the first varying section segment. When updating an ISM repository, Concept section approximations will appear as changes in the Change Management environment. The Change action on these changes can be set to Always Reject to prevent the ISM sections from being replaced.

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Table 16-4 gives the Concept Loading Type imported for each ISM Floor Load Cause.

Table 16-4 Concept Floor Loading Types Imported

Table 16-5 gives the Concept Loading Type imported for each ISM Roof Load Cause. Ism Load Cause


RoofAccess

Live Roof

RoofRain

Live Roof

RoofSnowDrift

Snow

RoofSnowUniform

Snow

RoofSnowUnspecified

Snow

RoofUnspecified

Live Roof

Table 16-5 Concept Roof Loading Types Imported

RAM Concept

Chapter 16 Table 16-6 gives the Concept Loading Type imported for each ISM Lateral Load Cause.

Table 16-8 defines the ISM Load Cause exported for each Concept Loading Type.

Ism Load Cause


Concept Loading Type Ism Load Cause

SeismicService

Seismic Service

Balance

PostTensioning

SeismicUltimate

Seismic Ultimate

Stressing Dead

DeadConstruction

SeismicUnspecified

Seismic Ultimate

Other Dead

DeadSuperimposed

WindService

Wind Service

Live Reducible

FloorUnspecified

WindUltimate

Wind Ultimate

Live Unreducible

FloorAssembly

WindUnspecified

Wind Service

Live Storage

FloorStorage

Live Parking

ParkingUnspecified

Live Roof

RoofAccess

Snow

RoofSnowUnspecified

Other

Other

Wind Service

WindService

Wind Ultimate

WindUltimate

Seismic Service

SeismicService

Seismic Ultimate

SeismicUltimate

Table 16-6 Concept Lateral Loading Types Imported

Table 16-7 gives the Concept Loading Type imported for each ISM Other Load Cause. Ism Load Cause


EarthPressureService

Other

EarthPressureUltimate

Other

EarthPressureUnspecified

Other

FloorConstruction

Other

FluidContained

Other

FluidUncontained

Other

FluidUnspecified

Other

GroundWaterPressure

Other

Hydrodynamic

Other

Hydrostatic

Other

Ice

Other

Other

Other

PostTensioning

Balance

Settlement

Other

Shrinkage

Other

Thermal

Other

Table 16-7 Concept Other Loading Types Imported

Table 16-8 ISM Load Cases Exported

The Balance loading is not exported to ISM by default. It is not always useful to other programs, and it may significantly increase the size of the ISM repository. See the Options section below for information on enabling Balance loading export.

16.3.8 Member Loading Concept loads are applied to the highest priority slab or beam they intersect. ISM loads are applied to a single ISM member. When exporting loads to ISM, Concept must determine which single ISM member the load should be applied to. Concept may have to split line or area loads that straddle more than one ISM member. A Concept Point Load is applied to an ISM beam if it lies on the beam centerline. Otherwise, it is applied to the surface member whose effective shape contains the point. A Concept Line Load that is completely contained in the beam centerline is applied to that beam. Otherwise, the line load is trimmed to the effective shape of each ISM surface member it intersects. If the line load intersects more than one surface member or has a disjoint intersection with a single surface member, it is split into shorter line loads and applied to the surface members they overlap. Concept area loads are trimmed to the outer boundary of the effective shapes of all ISM surface members that they intersect. If the intersection is disjoint, the Concept area

RAM Concept

63

Chapter 16 load is split into smaller polygonal area loads and applied to the surface members they overlap. It is possible to create a Concept model in a way that makes it impossible for Concept to maintain the accuracy of both the Concept and ISM models. For example, consider a Concept slab containing an opening and a second slab inside the hole (an island). Concept maintains the user's intentions by creating an ISM surface member for each slab. If there is an area load covering both slabs, Concept must create an additional area load for the island slab. However, the larger Concept area load will still cover the island slab, so the next Update operation would create yet another area load on the island slab. Instead, Concept does not create a new area load for the island slab and will leave the ISM surface member unloaded. The preferred method for modeling this configuration is to split up the larger area load so that it does not overlap the island slab.

16.3.9 Rebar Exporting Concept Rebar to ISM

Concept exports three types of rebar to ISM: • User Concentrated Rebar

Importing ISM Rebar into Concept

Concept imports ISM Concentrated Surface Rebar and ISM Area Surface Rebar into Concept as User Concentrated and User Distributed rebar. ISM Layer Parallel Rebar that are in an imported beam imported and converted into User Concentrated rebar. Concept does not import non-horizontal ISM rebar. It also does not import any incompletely defined ISM rebar type. ISM Concentrated Surface rebar must define the BarDirection, BarSpacing, BarCount, BarLength, LayoutDirection, LayoutPoint and HookLocalAxes properties. ISM Area Surface rebar must define the BarDirection, BarSpacing, LayoutBoundary and HookLocalAxes properties. ISM Layer Parallel rebar must define the LayoutPath property. ISM Anchor, Hook90, Hook180 and None (straight) rebar end types are supported. An Unset or Other hook type is imported as straight. Hook135 is imported as a 90 degree hook. LapSplice, OffsetLapSplice, MechanicalSplice and WeldedSplice are imported as anchors. Concept never imports ISM Perpendicular Rebar. Concept only creates Transverse Rebar during a Calc All operation. Therefore, it cannot be created in any other way, either by the user or from imported ISM data.

• User Distributed Rebar • Program Transverse Rebar Concept User Concentrated rebar are exported as ISM Concentrated Surface Rebar. When the Concept rebar is entirely contained within a beam and is parallel to the beam centerline, it is exported as ISM Layer Parallel Rebar. Plain, anchor, 90 degree and 180 degree hook types are exported.

16.3.10 Options Options controlling the ISM operations are set by choosing File > Sync ISM > Options. See Figure 16-4.

Concept User Distributed Rebar are exported as ISM Area Surface Rebar. Plain, anchor, 90 degree and 180 degree hook types are exported. Concept Program Transverse Rebar are exported as ISM Perpendicular Rebar. Depending on the number of Concept transverse rebar, multiple ISM perpendicular rebar will be exported. If the Concept transverse rebar has two or more legs and is closed, a single ISM Rectangle Tie Rebar will be exported. If open, a single ISM Open U Tie Rebar will be exported. ISM Straight Perpendicular Rebar are exported if there is one leg or as interior legs if there are greater than two Concept legs. ISM Perpendicular Rebar are defined by a parallelogram, whereas Concept generates individual Transverse bars that are adjusted to fit small variations in slab geometry. It is not often impossible to fit the Concept Transverse rebar to the ISM Perpendicular rebar parallelogram exactly. Concept approximates the ISM parallelogram with the average width, depth and midpoints of the first and last individual transverse bars.

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Figure 16-4 ISM Options Dialog

The options are: • Update Support Members in ISM Repository: Walls and columns in the ISM repository are updated only when this option is enabled. This option is stored in the file; by default, support members are not updated. Support members are always imported from the ISM repository to create or update the Concept model and are always exported when creating an ISM repository. • Export Balance Loading: the Balance loading is exported to ISM only when this option is enabled. This option is stored in the file. It is off by default, so the Balance loading is not exported

RAM Concept

Chapter 17

17 Defining the Structure The easiest and recommended way to define the concrete structure is to use RAM Concept’s automatic meshing facility (otherwise known as the “Mesher”). This approach requires that you define supports, slabs (of varying thickness), beams and openings with objects that Mesher uses to generate the finite element model. You do this on the Mesh Input Layer’s Standard Plan.

17.3.1 General column properties

17.1 Using the Mesh Input Layer There is no set order in which you must define objects. Some people choose to draw supports first, whereas others draw the slab outline first. You can edit whatever drawn objects later. If you have imported a CAD drawing, make it visible on the Mesh Input Plan before drawing the structure.

17.2 About columns and walls RAM Concept allows for single story models whereby you define columns and walls below and above the slab. Supports above the slab do not provide vertical support, only horizontal support and bending resistance.

17.3 Column properties RAM Concept column properties are separated into two categories: general and live load reduction.

Figure 17-1 Column properties: general

Concrete Mix Type of concrete used (defined in Materials Specification). Height Vertical distance from centroid of slab element to far end of column. Support Set Defines the column as below or above the floor. Width Measured along the column’s r-axis. Set to zero for round columns. Depth / Diameter Measured along the column’s s-axis. Angle Plan angle measured counterclockwise from the global x-axis. It determines the column’s r-axis (and is usually zero). Bending Stiffness Factor Used to modify the bending stiffness without changing the dimensions or height. For example, you may expect an edge column to crack and rotate more than an internal column and so you might consider setting this value to 0.5. You could use the BSF to increase a column’s stiffness, but this is an unlikely scenario. Roller at Far End Results in zero horizontal shear in column.

RAM Concept

65

Chapter 17 Fixed Near Provides a moment connection (about x- and y-axes) between column and slab; otherwise pinned.

fixity settings are somewhat different, and there is no Bending Stiffness Factor.

Fixed Far Provides a moment connection (about x- and yaxes) at far end; otherwise pinned.

The following is a list of RAM Concept wall properties:

Compressible Allows for column to elongate in the zdirection according to Hooke’s law; otherwise incompressible. Compressible columns usually produce results that are more accurate.

Concrete Mix Type of concrete used (defined in Materials Specification). Height Vertical distance from centroid of slab element to far end of wall. Support Set Defines the wall as below or above the floor.

17.3.2 Live load reduction column properties

Thickness

See “Specifying Live Load Reduction Parameters” on page 148.

Shear wall “Locks” the wall to the slab horizontally and thus restrains it; otherwise, the slab can “slide” over the wall. Fixed Near Provides a moment connection between wall and slab about the wall’s r-axis; otherwise pinned.

17.4 Drawing columns Each column is located with an x- and y-coordinate. Two columns cannot have the same coordinates unless one is above and one is below.

Note: Ensure you are working on the Mesh Input layer, not the Element layer.

Fixed Far Provides a moment connection about the wall’s r-axis at far end; otherwise pinned. Compressible Allows for the wall to elongate in the zdirection according to Hooke’s law; otherwise incompressible. Compressible walls usually produce results that are more accurate.

Note: See “Setting default properties” on page 21 for relevant information.

17.6 Drawing walls To draw a column:

1 Choose the Column tool (

).

2 Click at the column center.

The wall tool is very similar to the column tool except that it uses a line rather than a point. A wall can pass through a column, or intersect another wall.

To copy columns from below to above:

1 Select the columns and choose Edit > Copy. 2 Choose Edit > Paste. This pastes the new column objects

in the same location as the original column objects. The pasted columns are the active selection. 3 Change the Support Set property from “below” to

“above” in the Column Properties dialog box.

Note: If you do not change the Support Set designation then there are duplicated columns that do not allow the model to run properly. If you have copied a large number, it is tedious to delete the second column at each location (one by one).

Note: Ensure you are working on the Mesh Input layer, not the Element layer.

Note: The Wall tool ( ), Right Wall tool (

) & Left Wall tool ( ) share the same button on the Layer Specific toolbar. See “Expanding tool buttons” on page 6. To draw a wall:

1 Choose the Wall tool (

).

2 Click at the wall end center points. To copy walls from below to above:

1 Select the walls and choose Edit > Copy. 2 Choose Edit > Paste. This pastes the new wall objects in

17.5 Wall properties

the same location as the original wall objects. The pasted walls are the active selection. 3 Change the Support Set property from “below” to

Wall properties are similar to column properties though instead of width, depth and angle there is thickness. The

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“above” in the Wall Properties dialog box.

RAM Concept

Chapter 17

17.7 About point and line supports The result of defining a point support is a single support at a finite element node. The result of defining a line support is one or more line supports that are each located at a finite element edges. RAM Concept uses the thickness of the lowest numbered element in determining the support elevation. For this reason, it is not advisable to locate point supports or line supports at slab steps.

Rotation about s-axis fixed Prevents rotation about the local s-axis.

17.9 Drawing point supports Each point support is located with an x- and y-coordinate. Two point supports cannot have the same coordinates.

All supports that have a horizontal rigidity should be placed at the mid-depth of the slab or they may cause an unintended arch action in addition to their horizontal rigidity (mid-depth placement is done by setting the “Elevation above slab soffit” to be one-half of the slab depth).

Note: The Point Support tool (

Normally there is no need to use horizontal fixities in point and line supports, as RAM Concept automatically stabilizes the structure in the x- and y-directions (you can turn this automatic stabilization off in the General tab of the Calc Options dialog box). One situation where you might use a horizontal support is a structure braced against sidesway but modeled without bracing members (perhaps something other than a concrete wall provides the bracing).

2 Click at the point support location.

Be very careful about specifying anything but “Fixed in zdirection” for point supports and “Translation in z-direction fixed” for line supports. For point supports, fixing the point support in the r- or s-direction could result in arch / membrane action. For line supports, fixing the slab translation along or across the support could result in arch / membrane action.

Elevation above slab soffit Vertical distance between the line support and the soffit.

17.8 Point support properties

Translation in z-direction fixed (OFF for line of symmetry) Prevents the slab from deflecting up or down at the support axis.

The following is a list of RAM Concept point support properties: Elevation above slab soffit Vertical distance between the point support and the soffit. Angle (r=x, s=y@0) Allows you to set the local axes. Fixed in r-direction Prevents movement along the local r-axis. Fixed in s-direction Prevents movement along the local s-axis. Fixed in z-direction Prevents movement along the global z-axis. Rotation about r-axis fixed Prevents rotation about the local r-axis.

RAM Concept

) and Line Support tool ( ) share the same button on the Layer Specific toolbar. See “Expanding tool buttons” on page 6. To draw a point support:

1 Choose the Point Support tool (

).

17.10 Line support properties The following is a list of RAM Concept line support properties:

Translation along support fixed (OFF for line of symmetry) Prevents the slab from moving along the support axis. Translation across support fixed (ON for line of symmetry) Prevents the slab from moving across the support axis.

Rotation about support axis fixed (ON for line of symmetry) Prevents rotation of the slab about the support’s longitudinal axis. Rotation about perp.-to-support fixed (OFF for line of sym) Prevents rotation of the slab about the support’s transverse axis.

17.11 Drawing line supports You can use line supports as an axis of symmetry. This is very useful if a floor is symmetrical and you wish to model

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Chapter 17 only half of it. Be aware that line supports could prevent post-tensioning forces being applied to the floor.

Spring Angle (r=x, s=y@0) Orientation of the local axes. The plan shows spring orientation.

Note: The Point Support tool (

R-Force Constant Spring constant in the direction of the local r-axis.

) and Line Support tool ( ) share the same button on the Layer Specific toolbar. See “Expanding tool buttons” on page 6. To drawing a line support:

1 Choose the Line Support tool (

).

2 Click at the support end points.

S-Force Constant Spring constant in the direction of the local s-axis. Z-Force Constant Spring constant in the direction of the global z-axis. R-Axis Moment Constant Angular spring constant about the local r-axis.

17.12 About springs The result of defining a point spring is a single spring at a finite element node. The result of defining a line spring is one or more line springs that are each located at a finite element edge. RAM Concept uses the thickness of the lowest numbered element in determining the spring elevation. For this reason, it is not advisable to locate springs at slab steps. All springs that have a horizontal stiffness should be placed at the mid-depth of the slab or they may cause an unintended arch action in addition to their horizontal stiffness (mid-depth placement is done by setting the “Elevation above slab soffit” to be one-half of the slab depth). For slabs with varying centroid elevations, it can be difficult to avoid adding a rotational restraint to the slab when using lateral springs and supports. Normally there is no need to use horizontal springs, as Concept automatically stabilizes the structure in the x- and y-directions (you can turn this automatic stabilization off in the General tab of the Calc Options dialog box). One situation where you might use a horizontal spring is a structure braced against sidesway but modeled without bracing members (perhaps soil friction provides the bracing). Be very careful about specifying anything but a z-force constant. R- and s-force constants could result in membrane action.

17.13 Point spring properties The following is a list of RAM Concept point spring properties: Elevation above slab soffit Vertical distance between the point spring and the soffit.

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S-Axis Moment Constant Angular spring constant about the local s-axis.

17.14 Drawing point springs Each point spring is located with an x- and y-coordinate. Two point springs cannot have the same coordinates.

Note: The Point Spring tool (

), Line Spring tool ( ), and Area Spring tool ( ) share the same button on the Layer Specific toolbar. See “Expanding tool buttons” on page 6. To draw a point spring:

1 Choose the Point Spring tool (

).

2 Click at the spring location.

17.15 Line spring properties The following is a list of RAM Concept line spring properties: Elevation above slab soffit Vertical distance between the line spring and the soffit. Spring Angle (R=X, S=Y@0) Orientation of the local axes. The plan shows spring orientation. R-Force Constant Spring constant in the direction of the local r-axis at each end. S-Force Constant Spring constant in the direction of the local s-axis at each end. Z-Force Constant Spring constant in the direction of the global z-axis at each end. R-Moment Constant Angular spring constant about the local r-axis at each end.

RAM Concept

Chapter 17 S-Moment Constant Angular spring constant about the local s-axis at each end.

S-Moment Constant Angular spring constant about the local s-axis.

Note: If the force constant (or moment constant) is uniform

Note: If the force constant (or moment constant) is uniform

you need to enter only one value. Otherwise you need to enter two values separated by a comma (ends 1 and 2). This allows linear variation of the force constant (or moment constant).

you need to enter only one value.

Note: The force constant (or moment constant) can linearly vary in any direction.

Note: If the force constant (or moment constant) varies you 17.16 Drawing line springs The line spring tool is very similar to the point spring tool except that it uses a line rather than a point.


), Line Spring tool ( ), and Area Spring tool ( ) share the same button on the Layer Specific toolbar. See “Expanding tool buttons” on page 6.

need to enter three values, separated by commas (corners 1, 2 and 3). This allows linear variation of the force constant (or moment constant) in two directions. See Figure 17-2.

Note: If you use the Area Spring tool to specify a varying force constant (or moment constant), Concept calculates the unique value of the fourth corner (three points define a plane).

To draw a line spring:

1 Choose the Line Spring tool (

).

2 Click at the line spring end points.

17.17 Area spring properties The following is a list of RAM Concept area spring properties: Elevation above slab soffit Vertical distance between the area spring and the soffit. Spring Angle (R=X, S=Y@0) Orientation of the local axes. The plan shows spring orientation. R-Force Constant Spring constant in the direction of the r-axis.

Figure 17-2 Area spring properties varying from 100 to 200 to 300 units at the first three corners. For quad areas, Concept calculates the fourth corner value.

17.18 Drawing area springs

S-Force Constant Spring constant in the direction of the s-axis. Z-Force Constant Spring constant in the direction of the global z-axis. R-Moment Constant Angular spring constant about the local r-axis.

You use the Area Spring tool ( corners.

) to locate the spring area


), Line Spring tool ( ), and Area Spring tool ( ) share the same button on the Layer Specific toolbar. See “Expanding tool buttons” on page 6. To draw an area spring:

1 Choose the Area Spring tool (

).

2 Click at the vertices of the area spring (or enter the

coordinates in the command line).

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69

Chapter 17 3 Close the polygon by typing “c” in the command line or

clicking at the first vertex.

between the beams and other meshed surfaces are filled during the process, although this will result in a warning.

Note: An Area Spring object can be larger than the

Note: Supports do not have priorities.

structure it supports.

17.19 About floor areas and members Objects representing slabs, beams and openings define floor areas and members. Often these objects overlap.

17.19.1 The priority method At any floor location, only one thickness (depth) is used, and the object with the highest priority defines that thickness. The thicknesses of overlapping objects do not add to define the thickness.

Figure 17-3 Slab, beam and opening objects defined in the Mesh Input Standard Plan

For example, you would expect the overall thickness of a drop panel located at a column to take priority over the slab thickness. By assigning a Priority to each object, the automatic mesh generator understands how to generate the finite elements. The lowest Priority is 1. This is so that you can keep adding beams, thickenings and slab areas with higher priorities. There is no limit to the highest priority (other than your computer and text overflow).

Note: Overlapping objects for slabs, beams and openings must have different priorities. Priority numbers need not be sequential.

17.19.2 Meshing beams as slabs Beam objects by default do not need to have priorities specified. However, beams have an option to be meshed “Mesh as Slab” using the priority method. Any beams using the priority method will be meshed first along with slab and opening areas. The remaining beams are meshed last and are merged with the elements that result from the mesh resulting from the priority method. Any “gaps”

Figure 17-4 The Element Slab Summary Plan after mesh generation from Figure 17-3.

17.20 Slab area properties Slab area properties fall into two categories: general and behavior.

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RAM Concept

Chapter 17 The following is an explanation of RAM Concept slab area properties:

R-Axis defines an orientation for the slab. If the slab is a two way slab with identical properties in all directions (“isotropic”), then the R-Axis is irrelevant, because there is no inherent orientation of the slab. However, if the slab is not isotropic, then this axis (defined as the counterclockwise angle from 3 o'clock) defines the r-axis which is used along with the other slab area properties to define the behavior of the slab. The s-axis is always 90 degrees counter-clockwise from the r-axis. Behavior This defines the slab area’s behavior type. It has four possible designations: • Two-way slab The slab is isotropic and behaves in the same manner in all directions. • One-way slab The slab has normal bending stiffness along the r-axis and about the s-axis (Ms). The slab has only minimal bending stiffness in the perpendicular direction (Mr). The slab also has reduced torsional stiffness (Mrs). The in-plane stiffnesses are not affected by this setting.

Figure 17-5 Slab area properties - general

Concrete Mix Type of concrete used (defined in Materials Specification). Thickness You define slab thickenings, such as drop caps and drop panels, by specifying an increased thickness. Surface Elevation It is customary to set the typical elevation as 0. Setting the elevation to a very large value (such as 100 feet or 30 m) may result in round off errors in the analysis. You create surface and soffit steps by using different surface elevations for different areas. Priority Generally, the typical slab thickness has a Priority of 1.

• No-torsion 2-way slab The slab behaves like a twoway slab, except that it has only minimal torsional stiffness (Mrs). • Custom All of the stiffnesses (relative to the isotropic slab stiffness) can be specified by the user. These values are called KMr, KMs, KMrs, KFr, KFs and KVrs. In general, we do not recommend using this option. Refer to “Orthotropic behavior” on page 380 for further information on the use of Behavior properties.

17.21 Drawing slab areas Use the Slab Area tool ( ) to define the slab area by clicking on each consecutive point (vertex). To close the polygon, click on the first polygon point or type “c” and press Return. To draw a slab area:

1 Choose the Slab Area tool (

).

2 Click at each slab area vertex consecutively. 3 Snap to the first vertex and click to close the polygon (or

type “c” and press Return).

Note: You can approximate curves by a series of straight edges.

Figure 17-6 Slab area properties - behavior

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Chapter 17

17.22 About beams In RAM Concept, you model beams as thickened slabs with the beam tool. You can assign properties that differentiate beam behavior from slab behavior.

17.23 Beam properties Beam properties fall into two categories: general and behavior. The following is an explanation of RAM Concept beam properties:

Figure 17-8 Beam properties - behavior

The beam behavior properties are very similar to the slab area properties. The beam R-Axis is automatically set to the beam longitudinal axis. Behavior This defines the beam’s behavior type. It has four possible values: • Standard The beam is isotropic and behaves in the same manner in all directions. • No-torsion The beam behaves like a two-way slab, except that it has only minimal torsional stiffness (Mrs).

Figure 17-7 Beam properties - general

• Custom All of the stiffnesses (relative to the isotropic slab stiffness) can be specified by the user. These values are called KMr, KMs, KMrs, KFr, KFs and KVrs. In general, we do not recommend using this option.

Concrete Mix Type of concrete used (defined in Materials Specification). Thickness is the same as beam depth. Surface Elevation It is customary to set the typical elevation as 0. Setting the elevation to a very large value (such as 100 feet or 30 m) may result in round off errors in the analysis. You create surface and soffit steps by using different surface elevations for different areas. Width The beam width automatically appears to scale. Priority Generally, beams have higher priorities than slabs. Mesh As Slab If checked, this beam will be meshed identically to slabs using the priority method.

17.24 Drawing beams You draw a beam by clicking the start and end points of its centerline using the Beam tool ( ). Each beam has six control points. The four additional points are automatically located so that the beam-ends are perpendicular to the sides. You can stretch the corner grip points to define mitered corners.

Note: The Beam tool ( ), Right Beam tool ( ) & Left Beam tool ( ) share the same button on the Layer Specific toolbar. See “Expanding tool buttons” on page 6. To draw a beam:

1 Choose the Beam tool (

).

2 Click at the each end of the beam centerline.

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Chapter 17 To define mitered corners on a beam:

1 Select the beam and choose the Stretch tool (

To draw a slab opening:

).

1 Choose the Slab Opening tool (

).

2 Snap to the beam corner grips and stretch them into

2 Click at each slab-opening vertex consecutively.

position.

3 Snap to the first vertex and click to close the polygon (or


Note: You approximate curves with a series of straight 17.25 Slab opening properties

edges.

There is only one slab opening property: Priority Generally, openings have the highest priorities in the floor.

17.26 Drawing slab openings The Slab Opening tool ( slab.

RAM Concept

) defines an opening in the

17.27 Checking the structure definition After you have fully defined the structure’s geometry, you should check for obvious errors. RAM Concept flags illegal modeling when generating the mesh. A list of possible errors appears in Chapter 18, “Generating the Mesh”. Once you have drawn all the support and floor objects on the Mesh Input Plan, you must generate the actual finite element mesh. The structure does not exist until you generate the mesh.

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Chapter 18

18 Generating the Mesh There are two ways to generate the finite element mesh in RAM Concept:

The dialog box shown in Figure 18-1 will appear.

• Using the automatic meshing facility that uses the mesh input objects described in Chapter 17, “Defining the Structure”. • Using the manual meshing tools. The first method is certainly easier and faster. It is the recommended method for nearly all models. The second method allows more control over mesh intensity. The mesh size can be more widely varied in different areas of the floor, but editing is more difficult. Instructions for the second (manual) method are in Chapter 19, “Manually Drawing the Finite Elements”.

Figure 18-1 Generate mesh dialog box

2 Specify the Element Size in the Generate Mesh dialog

box.

18.1 Generating the mesh automatically Finite elements do not exist (and hence there is no structure) until the mesh has been generated. You need to have defined the mesh input objects (using the procedure described in the preceding chapter) before generating the mesh. It is preferable to generate the mesh as soon as possible, although it is possible to draw additional objects on other layers (such as loads) before generation.

18.1.1 Deciding what mesh element size to use When generating the mesh you need to decide what element size to use. The maximum is 32.8 feet (10 meters). To speed the analysis, it is useful to choose a coarse mesh for preliminary design and a fine mesh for final design. A coarse mesh might have an element size of span length / 6. A fine mesh might have an element size of span length / 12. If in doubt, you should investigate the effects of different mesh element sizes. To generate the mesh automatically:

1 Click Generate Mesh (

).

3 Click Generate.

The time taken to generate the mesh depends upon the size of the floor and the specified mesh element size. For most models, the mesh generates in less than 15 seconds.

Note: Every time you generate a mesh, RAM Concept deletes any existing mesh and generates a new one.

18.1.2 Limitations of the automatic meshing The main automatic meshing limitation is that the minimum element size is 50 mm (0.164 feet). Concept can usually overcome this limitation by adjusting the mesh input objects to generate a mesh. Concept moves mesh input line objects (for example, walls, line supports) to accommodate point objects (for example, columns, point supports). Concept automatically adjusts the mesh input objects if: • Two control points are closer than the minimum element size. • A control point is closer to a line than the minimum element size.

Note: Concept generates warnings during the meshing if it was necessary to make adjustments. You can stop the meshing and make corrections. If you continue, you should check the mesh to see if the adjustments are satisfactory.

Note: Concept generates a warning if two slab areas (or beams or openings) with the same priority overlap. You can stop the meshing and make corrections. If you continue you

RAM Concept

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Chapter 18 should check the mesh to see if the adjustments are satisfactory as the choice of which slab area (or beam) governs the elements is effectively random.

Note: Concept moves two columns to the same point that you draw closer than the minimum element size. A mesh generates but the model does not run properly if: • A column or point support is outside of the slab areas. • A wall or line support is partially outside the slab areas. • An area spring is completely outside the slab areas. • Two columns or walls of the same support set are duplicated (intersecting walls are allowed). Figure 18-2 Mesh before Design Strips To avoid mesh warnings:

Do any one of the following: 1 Adjust objects on the Mesh Input plan so that the

minimum element size dimension (or more) separates them. 2 Edit priorities so that slab areas, beams and openings

with the same priorities do not overlap.

18.1.3 Viewing the finite element mesh You can view the finite element mesh on any plan, but the Standard Plan of the Element layer is the preferred plan to use. To view the finite element mesh:

1 Open Layers > Element > Standard Plan.

The mesh generated at this stage appears to be somewhat random. This is normal and in fact, for sensible mesh sizes it produces highly satisfactory design results. At times, however, such a mesh (adversely) affects the contour plots.

18.1.4 Improving the mesh You can significantly improve the mesh once design strips are drawn. The following diagrams show the differences.

Figure 18-3 Mesh after drawing Design Strips and Regenerating.

18.2 Selectively refining the mesh Although there is no setting that makes the mesh finer in some areas than others, you can employ a trick to achieve this.

18.2.1 Using point and line supports to refine the mesh You can draw “dummy” point or line supports to ensure that the mesh is finer in particular areas. You must ensure that all fixity boxes are unchecked, as shown in Figure 18-4 and Figure 18-5. A refined mesh example is shown in Figure 18-6.

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Figure 18-4 Point support dialog box with all fixity boxes unchecked.

Figure 18-5 Line support dialog box with all fixity boxes unchecked

Figure 18-6 Two slabs, identical in every way except for the implementation of line supports to refine the mesh.

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Chapter 18

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Chapter 19

19 Manually Drawing the Finite Elements Note: In most cases, you do not need to draw the finite element mesh manually. If you have used the automatic method, there is no need to read this chapter There are two ways to generate the finite element mesh in RAM Concept: • Using the automatic meshing facility, described in Chapter 18, “Generating the Mesh”, that uses the mesh input objects, described in Chapter 17, “Defining the Structure”. • Using the manual meshing tools described in this chapter. The first method is certainly easier and faster. It is the recommended method for nearly all models. The second method allows more control over mesh intensity: the mesh size can be more widely varied in different areas of the floor. The method is, however, more prone to user error and editing is more difficult. Do not use the manual method to supplement a mesh made with the automatic meshing facility. This is because manual elements would be lost if you used the mesh generation facility. For example, if you added a column element above in the element layer it would be lost when you regenerated.

Concrete Mix Type of concrete used (defined in Materials Specification). Height Vertical distance from centroid of slab element to far end of column. Support Set Defines the column as below or above the floor. Width Measured along the column’s r-axis. Set to zero for round columns. Depth / Diameter Measured along the column’s s-axis. Angle Plan angle measured counterclockwise from the global x-axis. It determines the column’s r-axis (and is usually zero). Bending Stiffness Factor Used to modify the bending stiffness without changing the dimensions or height. For example, you may expect an edge column to crack and rotate more than an internal column and so you might consider setting this value to 0.5. You could use the BSF to increase a column’s stiffness, but this is an unlikely scenario. Roller at Far End Results in zero horizontal shear in column. Fixed Near Provides a moment connection (about x- and y-axes) between column and slab; otherwise pinned.

19.1 Using the Element layer There is no set order in which you must define objects. Most people choose to draw supports first. If you have imported a CAD drawing, make it visible on the Element Standard Plan before drawing the structure.

19.2 About column elements and wall elements RAM Concept allows for single story models whereby you define columns and walls below and above the slab. Supports above the slab do not provide vertical support, only horizontal support and bending resistance.

Fixed Far Provides a moment connection (about x- and yaxes) at far end; otherwise pinned. Compressible Allows for column to elongate in the zdirection according to Hooke’s law; otherwise incompressible. Compressible columns usually produce results that are more accurate.

19.4 Drawing column elements Each column is located with an x- and y-coordinate. Two columns cannot have the same coordinates unless one is above and one is below.

Note: If slab elements are already drawn, you need to draw column elements at slab element nodes. To draw a column element:

19.3 Column element properties

1 Choose the Column Element tool (

).

2 Click at the column center.

The following is a list of RAM Concept column element properties:

RAM Concept

To copy columns from below to above:

1 Select the column elements and choose Edit > Copy.

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Chapter 19 2 Choose Edit > Paste. This pastes the new column

elements in the same location as the original column elements. The pasted column elements are the active selection. 3 Change the Support Set property from “below” to

“above” in the Column Element Properties dialog box.

Note: If you do not change the Support Set designation then there are duplicated column elements that do not allow the model to run properly. If you have copied a large number, it is tedious to delete the second column element at each location (one by one).

A wall element can pass through a column element, or intersect another wall element.

Note: If slab elements are already drawn, you need to draw wall elements along the edge of the slab elements. The ends of the wall elements must be at slab element nodes. Wall elements cannot traverse a slab finite element. To draw wall elements on slab elements:

1 Choose the Wall Element tool (

).

2 Click at the wall end center points. To draw wall elements where there are no slab elements:

1 Choose the Wall Element tool (

19.5 Wall element properties

).

2 Click at the wall end center points. 3 Specify the number of elements in the Wall Element Tool

Wall element properties are similar to column element properties though instead of width, depth and angle there is thickness. The fixity settings are somewhat different, and there is no Bending Stiffness Factor. The following is a list of RAM Concept wall element properties: Concrete Mix Type of concrete used (defined in Materials Specification).

dialog box and click OK. To copy walls from below to above:

1 Select the wall elements and choose Edit > Copy. 2 Choose Edit > Paste. This pastes the new wall elements

in the same location as the original wall element objects. The pasted wall elements are the active selection. 3 Change the Support Set property from “below” to

“above” in the Wall Element Properties dialog box.

Height Vertical distance from centroid of slab element to far end of wall element. Support Set Defines the wall element as below or above the floor. Thickness Shear wall “Locks” the wall element to the slab horizontally and thus restrains it; otherwise, the slab can “slide” over the wall. Fixed Near Provides a moment connection between the wall element and the slab about the wall element’s r-axis; otherwise pinned Fixed Far Provides a moment connection about the wall element’s r-axis at far end; otherwise pinned. Compressible Allows for wall element to elongate in the z-direction according to Hooke’s law; otherwise incompressible. Compressible walls usually produce results that are more accurate.

19.6 Drawing wall elements The wall element tool is very similar to the column tool except that it uses a line rather than a point.

80

19.7 About point and line supports The result of defining a point support is a single support at a finite element node. The result of defining a line support is one or more line supports that are each located at a finite element edge. RAM Concept uses the thickness of the lowest numbered element in determining the support elevation. For this reason, it is not advisable to locate point supports or line supports at slab steps. All supports that have a horizontal rigidity should be placed at the mid-depth of the slab or they may cause an unintended arch action in addition to their horizontal rigidity (mid-depth placement is done by setting the “Elevation above slab soffit” to be one-half of the slab depth). Normally there is no need to use horizontal fixities in point and line supports, as RAM Concept automatically stabilizes the structure in the x- and y-directions (you can turn this automatic stabilization off in the General tab of the Calc Options dialog box). One situation where you might use a horizontal support is a structure braced against sidesway but modeled without bracing members (perhaps something other than a concrete wall provides the bracing). Be very careful about specifying anything but “Fixed in zdirection” for point supports and “Translation in z-direction RAM Concept

Chapter 19 fixed” for line supports. For point supports, fixing the point support in the r- or s-direction could result in arch / membrane action. For line supports, fixing the slab translation along or across the support could result in arch / membrane action.

To drawing a line support on slab elements:

1 Choose the Line Support tool (

).

2 Click at the support end points.

19.12 About springs 19.8 Point support properties See “Point support properties” on page 67 for more information on point support properties.

19.9 Drawing point supports You draw point supports by clicking at their location with the Point Support tool (

).

Note: The Point Support tool ( (

) and Line Support tool ) share the same button on the Layer Specific toolbar.

Note: If slab elements are already drawn, you need to draw point supports at slab element nodes. To draw a point support:

1 Choose the Point Support tool (

).

2 Click at the point support location.

19.10 Line support properties See “Line support properties” on page 67 for more information on line support properties.

19.11 Drawing line supports You can use line supports as an axis of symmetry. This is very useful if a floor is symmetrical and you wish to model only half of it. Be aware that line supports could prevent post-tensioning forces being applied to the floor.

The result of defining a point spring is a single spring at a finite element node. The result of defining a line spring is one or more line springs that are each located at a finite element edge. RAM Concept uses the thickness of the lowest numbered element in determining the spring elevation. For this reason, it is not advisable to locate springs at slab steps. All springs that have a horizontal stiffness should be placed at the mid-depth of the slab or they may cause an unintended arch action in addition to their horizontal stiffness (mid-depth placement is done by setting the “Elevation above slab soffit” to be one-half of the slab depth). For slabs with varying centroid elevations, it can be difficult to avoid adding a rotational restraint to the slab when using lateral springs and supports. Normally there is no need to use horizontal springs, as RAM Concept automatically stabilizes the structure in the x- and y-directions (you can turn this automatic stabilization off in the General tab of the Calc Options dialog box). One situation where you might use a horizontal spring is a structure braced against sidesway but modeled without bracing members (perhaps soil friction provides the bracing). Be very careful about specifying anything but a z-force constant. R- and s-force constants could result in membrane action.

19.13 Point spring properties See “Point spring properties” on page 68 for more information on point spring properties.

Note: The Point Support tool ( (

) and Line Support tool ) share the same button on the Layer Specific toolbar.

Note: If slab elements are already drawn, you need to draw line supports along the edge of the slab elements. The ends of the line supports must be at slab element nodes. Line supports cannot traverse a slab finite element.

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Chapter 19

19.14 Drawing point springs Each point spring is located with an x- and y-coordinate. Two point springs cannot have the same coordinates.

Note: The Point Spring tool ( and Area Spring tool ( Layer Specific toolbar.

), Line Spring tool ( ), ) share the same button on the

19.18 Drawing area springs You use the Area Spring tool ( area corners.

) and locate the spring



Note: If slab elements are already drawn, you need to draw To draw an Area Spring:

point springs at slab element nodes.

1 Choose the Area Spring tool ( To draw a point spring:

2 Click at the four corner point locations of the area spring.

1 Choose the Point Spring tool (

).

2 Click at the spring location.

Note: An Area Spring object can be larger than the structure it supports.

19.15 Line spring properties See “Line spring properties” on page 68 for more information on line spring properties.

19.16 Drawing line springs The line spring tool is very similar to the point spring tool except that it uses a line rather than a point.


).


Note: If slab elements are already drawn, you need to draw

19.19 About floor areas You define floor slabs and beams manually with the slab meshing tools. Drawing elements manually requires more thought on the drawing process. Poor decisions could require a significant amount of editing and duplication of work. Drawing elements manually also requires careful application of the tools to ensure that the side of each element is the same length as the adjacent element. In other words, each element node must be at the corner of any element that touches it. Elements cannot overlap. You model beam elements as thickened slab elements with the same slab element tools. You model openings as empty spaces in the mesh.

line springs along the edge of the slab elements. The ends of the line springs must be at slab element nodes. Line springs cannot traverse a slab finite element.

19.20 Slab element properties To draw a line spring:

1 Choose the Line Spring tool (

).

2 Click at the line spring end points.

Slab area properties fall into two categories: general and behavior. The following is an explanation of RAM Concept slab area properties:

19.17 Area spring properties See “Area spring properties” on page 69 for more information on area spring properties.

Concrete Mix Type of concrete used (defined in Materials Specification). Thickness You define slab thickenings, such as drop caps and drop panels, by specifying an increased thickness. Surface Elevation It is customary to set the typical elevation as 0. Setting the elevation to a very large value (such as 100 feet or 30 m) may result in round off errors in

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Chapter 19 the analysis. You create surface and soffit steps by using different surface elevations for different areas.

the Poly Slab Mesh Elements tool ( ). This would often mean drawing slab panels (with columns in the corners) in one operation.

Note: The Rect Slab Mesh Elements tool ( Slab Mesh Elements tool ( Element layer toolbar.

) and Poly ) share the same button on the

Note: You can approximate curves by a series of straight edges. To draw a rectangular slab mesh area:

1 Choose the Rect Slab Mesh Elements (

) tool.

2 Click at two opposite corners of the rectangle. 3 Specify the element size in the Rect Mesh Tool dialog

box and click OK. To draw a polygon slab mesh area:

1 Choose the Poly Slab Mesh Elements (

) tool.

2 Click at each slab panel vertex consecutively.

Figure 19-1 Slab element properties - behavior


R-Axis defines an orientation for the slab. If the slab is a two way slab with identical properties in all directions (“isotropic”), then the R-Axis is irrelevant, because there is no inherent orientation of the slab. However, if the slab is not isotropic, then this axis (defined as the counterclockwise angle from 3 o'clock) defines the r-axis which is used along with the other slab area properties to define the behavior of the slab. The s-axis is always 90 degrees counter-clockwise from the r-axis. KMr, KMs, KMrs, KFr, KFs, KVrs Relative stiffnesses (compared to isotropic slab stiffness). Refer to “Orthotropic behavior” on page 380 for further information on the use of Behavior properties.

19.21 Drawing the slab elements You can draw slab elements one or more at a time. Usually you would attempt to draw as many as practical in one operation using the Rect Slab Mesh Elements tool (

RAM Concept

type “c” and press Return). 4 Specify the element size in the Poly Mesh Tool dialog

box and click OK. To draw a single mesh element:

1 Choose one of the single element tools (

).

2 Click at each of the three (or four) slab panel vertices

consecutively. 3 Snap to the first vertex and click to close the polygon (or


19.22 A few final words Do not click Generate Mesh ( ) after drawing the mesh elements manually. It deletes all the elements that you have drawn.

) or

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20 Drawing Loads RAM Concept allows you to draw point, line and area loads and moments on any loading plan. These loads can be in the directions of the global x-, y- and z-axes and the moments can be about the global x- and y-axes.

20.3 Point load properties The following is a list of RAM Concept point load properties:

Each load belongs to a loading layer, such as Live Loading. You define each loading in the loadings window, and draw the loads on plans.

Elevation above slab surface Vertical distance between the point load and the slab surface.

There is no limitation to the number of loads defined.

Fx Point force in the direction of global x-axis (horizontal force).

Loads are independent of the finite element mesh and have no effect on the automatic mesh generation. This is satisfactory for most loads. For very heavy point or line loads (such as on a mat or transfer slab), however, the loads should correlate with the finite element mesh nodes. You can do this by drawing pinned columns and walls above the floor, and drawing the loads at these locations with the help of snaps. Alternatively, you can refine the mesh locally with the use of “dummy” slab objects. Refer to “Selectively refining the mesh” on page 76 for further information. Horizontal loads may cause applied moments depending upon the elevation above the slab surface of the loads. If a load is located at a slab surface step, RAM Concept uses the thickness of the lowest numbered slab element in determining the load elevation. For this reason, it is not advisable to locate point or line loads at steps. Importing a CAD drawing may assist you in drawing loads.

Fy Point force in the direction of global y-axis (horizontal force). Fz Point force in the direction of global z-axis (vertical force). Mx Point moment about the global x-axis. My Point moment about the global y-axis.

Note: Although point loads need not be located at a finite element node, you should consider locating very large loads at nodes. Point loads must be located on finite elements; Concept issues a warning if you violate this rule.

Note: Sign convention is defined in Criteria > Signs. See Chapter 8, “Choosing Sign Convention”.

Note: Horizontal forces (Fx, Fy) cause applied moments unless the Elevation above slab surface is set to apply the load at the slab centroid.

20.1 About self-weight 20.4 Drawing point loads RAM Concept automatically calculates the floor’s selfweight for the Self-Dead Loading.

Each point load is located with an x- and y-coordinate. To draw a point load:

20.2 About superposition of loads

1 Choose the Point Load tool (

).

2 Click at the load location (or enter the coordinates in the

Point loads cannot be at the same location on the same loading layer. Line loads can intersect or overlap, but cannot have the exact same length and location on the same loading layer. Area Loads can overlap, but cannot have the exact same shape and location on the same loading layer. Overlapping loads are additive.

command line).

20.5 Line load properties The following is a list of RAM Concept line load properties: Elevation above slab surface Vertical distance between the line load and the slab surface. Fx Line force in the direction of global x-axis (horizontal force).

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Chapter 20 Fy Line force in the direction of global y-axis at each end (horizontal force).

20.6 Drawing line loads

Fz Line force in the direction of global z-axis at each end (vertical force).

There are two line load tools.

Mx Line moment about the global x-axis at each end.

20.6.1 Standard line load

My Line moment about the global y-axis at each end.

The line load tool is very similar to the point load tool except that it uses two points rather than one point.

Note: If the line force (or moment) is uniform you need to

To draw a line load:

enter only one value. Otherwise you need to enter two values separated by a comma (ends 1 and 2). This allows linear variation of the line force (or moment). See Figure 20-1.

1 Choose the Line Load tool (

Note: Although line loads need not be located at a finite element node, you should consider locating very large loads at element edges. Line loads must be completely located on finite elements; Concept issues a warning if you violate this rule.

).

2 Click at the load end points (or enter the coordinates in

the command line).

20.6.2 Perimeter line load The perimeter line load tool facilitates the drawing of multiple line load objects around the perimeter, with or without an offset.

Note: Sign convention is defined in Criteria > Signs. To draw a perimeter line load:


1 Choose the Perimeter Line Load tool (

).

2 Click anywhere on the slab. 3 In the dialog box that appears, enter the Inset Distance,

and click Apply.

20.7 Area load properties The following is a list of RAM Concept area load properties: Elevation above slab surface Vertical distance between the area load and the slab surface. Fx Area force in the direction of global x-axis (horizontal force). Fy Area force in the direction of global y-axis (horizontal force). Figure 20-1 Line load properties varying from 10 to 20 units.

Fz Area force in the direction of global z-axis (vertical force). Mx Area moment about the global x-axis.

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Chapter 20 My Area moment about the global y-axis.

20.8 Drawing area loads

Note: If the area force (or moment) is uniform you need to enter only one value per axis.

Note: The area force (or moment) can linearly vary in any direction. The area force variation could be for snowdrift, or sloping soil. Note: If the area force (or moment) varies you need to enter three values, separated by commas (vertices 1, 2 and 3). This allows linear variation of the line force (or moment) in two directions. See Figure 20-2.

You use the Area Load tool ( vertices.

) to locate the area load

While it is neater to draw area loads that match the floor, it is satisfactory to make the load oversize. RAM Concept ignores any part of an area load that is not on a floor element. Exaggerating the size too much affects the automatic printing and zooming bounds. To draw an area load:

Note: If you use more than three vertices, Concept calculates the unique value at all vertices (three points define a plane).

Note: Area loads must be at least partially located on finite elements; Concept issues a warning if you violate this rule. Concept ignores any part of an area load not on a finite element.

Note: Sign convention is defined in Criteria > Signs.

1 Choose the Area Load tool (

).

2 Click at the vertices of the area load (or enter the coordi-

nates in the command line). 3 Close the polygon by typing “c” in the command line or

clicking at the first vertex.

20.9 Copying loads


You can copy loads from one Loading plan to another. This is convenient since in practice most loads have values for more than one loading. To copy a load from one loading to another:

1 Select the load and choose Edit > Copy. 2 Open the loading plan to which you wish to paste. 3 Choose Edit > Paste. This pastes the new load in the same

plan location as the original load. The pasted load is the active selection. 4 Edit the properties of the new load.

Note: You can copy, paste and edit multiple loads simultaneously.

Figure 20-2 Area load properties varying from 10 to 20 to 30 units at the first three vertices. Concept calculates the values at all other vertices.

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Chapter 21

21 Creating Pattern Loading RAM Concept generates pattern loadings based upon the load patterns that you draw. “About load pattern” on page 36 explains the principle of load pattern.

To Draw Load Patterns:

1 Choose Layers > Pattern. 2 Open one of the load pattern plans (from Load Pattern 1

through Load Pattern 10). 3 Double click the Pattern Load tool (

).

21.1 Deciding how many load patterns to use

4 Specify which pattern number you wish to use (the

Mathematically, there could a large number of floor pattern loadings, which would all have different results. For practical reasons, the maximum number of load patterns is ten. This allows you to draw five load patterns in each direction.

Draw the on-pattern areas with a polygon.

Typical pattern loading configurations are:

7 Repeat for all patterns.

number should correspond to the load pattern plan’s number).

5 Click at each slab area vertex consecutively. 6 Snap to the first vertex and click to close the polygon (or


Note: Regardless of which load pattern plan you are using, the pattern number will be the last one specified. You will need to change this for each different pattern plan.

21.3 Load pattern filtering Internally, RAM Concept resolves a pattern loading by determining which slab and beam finite elements are partially or wholly within the related load pattern. The loads on these elements (the element loads) are multiplied by the on-pattern factor. For elements totally outside the pattern, the element loads are multiplied by the off-pattern factor. Figure 21-1 Beam Pattern Loadings. Note that these will not necessarily produce the maximum negative moments, but they will produce moments that are very close to the maximum and represent a practical solution in most situations.

Thus, RAM Concept’s calculation pattern areas approximate the pattern areas that you draw. You should consider this when drawing load patterns and choosing mesh size as it will affect the actual pattern loadings generated.

21.2 Drawing load patterns

21.3.1 Effect of mesh on load pattern

You draw load patterns as part of the pattern loading process.

The finite element mesh regularity and intensity has an effect on the load pattern process. The following example best explains the process.

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Chapter 21 Load pattern for four-panel slab

Actual pattern areas for an irregular fine mesh

Figure 21-2 To generate the maximum My at midspan you would use this load pattern.

Figure 21-4 With the finer mesh, the point load will not be included and there will be less additional area load in the pattern loading.

Actual pattern areas for an irregular coarse mesh

Actual pattern areas for a regular coarse mesh

Figure 21-3 The point load and some additional area load will be included in the pattern loading.

Figure 21-5 This mesh generates a pattern loading with an area that closely resembles the load pattern.

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Chapter 21 Drawing design strips significantly improves the mesh. See Chapter 18, “Generating the Mesh” for more information on improving the mesh.

Note: The mesh becomes more regular if you generate or regenerate after design strips are drawn.

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Chapter 22

22 Defining Design Strips Note: Design strips are perhaps the most important tool in RAM Concept. It is highly recommended that the designer takes the time to fully understand what a design strip does, and how to use them. If you use design strips improperly then the results will be meaningless.

three Span Segment Strips (left, center and right). These are known as design strips. See Figure 22-1 for further explanation.

Finite element analysis often produces high peak moments and stress concentrations which are inappropriate for calculation of reinforcement and evaluating performance. Code rules are generally intended for strip methods that assume an averaging (or “smearing”) of moment and shear across a designated width, such as a column strip. RAM Concept uses design strips and design sections to link finite element analysis with concrete code rules and concrete design.

22.1 Definition of a design strip A design strip is an object that: • contains a series of cross sections at specific locations • is usually the length of a span, or part of a span, but can in fact have any length within the structure • integrates resultants (moments, shears, axial forces, torsions) for all load combinations along each cross section (and, hence, across the design strip’s width) • applies appropriate code rules to the resultants A design strip is the same as a span segment strip.

22.2 Design strip terminology It is important to understand the different objects used to define design strips. Figure 22-1 Design strips for a two-way flat plate.

Span segment A line segment-line entity that is intended to indicate a portion of a structural span or a whole structural span. The “at support” properties of the Span Segment indicate where the span starts and stops. Span One or more connected Span Segments that together make up a single structural span. Nearly all spans require only one Span Segment.

22.3 Understanding how a design strip works RAM Concept generates design strips from span segments.

Frame One or more Spans that are connected together to form a continuous line of spans.

A design strip is normally the length of a span with a logical width.

Span Segment Strip A set of cross sections associated with a Span Segment. The Span Segment can have up to

Concept subdivides each individual design strip segment according to the following parameters: • minimum number of divisions

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Chapter 22 • maximum division spacing • support width • changes in concrete section along the span Concept locates a design strip cross section at the start of each division, plus one at the end. The length of each cross section equals the width of the design strip at that location. See Figure 22-2. Concept modifies the geometrical properties of each design strip cross section according to the cross section trimming and inter cross section slope limit settings. Concept integrates the resultants for each load combination along the length of each design strip cross section (and hence across the width of the design strip). See Figure 223. Concept uses some properties of each span segment to determine applicable code rules (beam or slab, posttensioned or reinforced) for the corresponding design strip. Concept applies the code rules to the envelope of the load combination integrals within a rule set. Other span segment properties (reinforcement bar sizes, cover) facilitate the actual code rule calculations. See “Span segment properties” on page 96 for more information.

Figure 22-2 Column strip and two middle strips belonging to one span with cross sections visible.

Concept separates design strips into two sets: latitude and longitude. The two sets are for convenience and recognize that concrete floors should be designed in two directions.

Note: As with all plans, you can rename the Latitude Design Strip Plan and Longitude Design Strip Plan by choosing Layer > Rename.

Figure 22-3 Moment about the y-axis (My) plotted across one cross section of three design strips.

22.4 The design strip process This is best explained by Figure 22-4. 94

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Chapter 22

Step 1 - Create the Span Segments

Specify the default span segment properties

AND / OR

EITHER

Generate Span Segments

Draw Span Segments (manually)

(and supplement and adjust if necessary)

Step 2 - Create Span Segment Strips You create Span Segment Strips from Span Segments with the Generate Strips command. You cannot draw or directly edit Span Segment Strips.

Step 3A - Examine Span Segment Strips Check the Lock Generated Strips box of any Span Segment that has satisfactory strips.

Step 3B - Edit Span Segment Properties Use the strip generation tab of the Span Segment properties dialog to modify the Span Segment Strips.

Step 3C - Edit Span Segments manually Use the Span Boundary, Strip Boundary, and Orient Span Cross Section tools to control the strip generation.

Step 3D - Set cross section trimming This enables you to modify the concrete section used for shear and flexure calculations.

Continue Figure 22-4 Flow diagram of the design strip process

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22.5 Span segment properties

Consider Axial Force in Strength Design Uses the net section axial force in bending design.

Span segment properties serve different purposes. RAM Concept uses properties to determine the following:

This is a very important setting related to the effect of axial force resultants (not necessarily axial loads) in a cross section. If you select this option, Concept includes the interaction of the axial force with the bending in the cross section strain calculations, similar to typical column design using strain compatibility. We generally recommend the consideration of axial forces in strength design. For sections with net axial compression this will tend to reduce the reinforcement demand while for sections with net axial tension it will typically increase the reinforcement demand.

• design method (e.g. inclusion of axial force) • design strip width and cross section geometry • appropriate code design rules (e.g. beam or slab) • reinforcement • live load reduction The following is an explanation of Concept span segment properties:

Consider as Post-Tensioned Enables Concept to decide which code rules are used. This determines if the design strip segment is checked for initial service design code rules (for the Initial Service LC) and whether RC or PT code rules are used (some codes do not make this distinction).

Note: If consider as post-tensioned is not used then Concept ignores tendons in strength calculations. Don’t reduce integrated M and V due to sign change The intent of this option is to allow for safe, conservative designs where cross sections include regions of moment (or shear) with opposite signs that cause the moment (or shear) recorded for the cross section to be less than that for a shorter sub- cross section. When this option is selected, the design forces are always more conservative than when the option is not selected. This option should not be used without due consideration.

Figure 22-5 Span segment properties - General

See “Using the “Don't Reduce Integrated M and V due to Sign Change” option” on page 391 for explanation.

Span Set Determines the set the span segment belongs to: latitude or longitude. Environment The environment setting affects which service rules Concept selects in some codes. Refer to the appropriate code discussion chapter for more information: • Section 55.5.4 on page 452 and Section 55.6.10 on page 458 for relevance to ACI318-02. • Section 59.6.15 on page 536 for relevance to AS3600. • Section 61.5.4 on page 563 for relevance to BS8110. • Section 62.5.4 on page 585 for relevance to IS 456. • Section 63.5 on page 585 for relevance to EC2. • Section 64.5 on page 629 for relevance to CSA A23.3.

Note: This setting has a significant effect on reinforcement quantities. Figure 22-6 Span segment properties - Strip Generation

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Chapter 22 Span Width Calc This determines how Concept calculates the span width. The choices are:

• the web with plus 0.07 times the span length plus 0.2 times the overhanging flange width on either side, not to exceed 0.14 times the span length (EC2 only)

• Automatic: this applies (sometimes fallible) logic to calculate the span width as the closest of:

• The web width plus 12 times the flange thickness on either side (CSA A23.3 codes only)

• the Span Boundaries (in the same latitude/longitude set as the Span Segment)

• The web width plus 0.1 times the span length on either side (CSA A23.3 codes only)

• the slab edges • half-way to the nearby spans or walls • Manual: this overrides the automatic calculation and determines span widths by the closest Span Boundary items (in the same latitude/longitude set as the Span Segment). See “Drawing span segments manually” on page 100 for further information.

Note: When the Manual setting is used in a strip segment, all of the span boundaries for that strip segment must be defined. A strip segment generates a span width of zero when some of its length does not have any span boundaries defined. Column Strip Width Calc This determines how the column strip width is determined. The term “column strip width” is used for more than flat slabs with column and middle strips. The choices are: • Full Width: this is typical for PT slabs designed to ACI318 and TR43. The column strip width is the same as the span width. • Code Slab: this is typical for two-way RC slabs, and two-way PT slabs designed to AS3600. The column strip width is the narrower of: • the span width • the Strip Boundaries (in the same latitude/longitude set as the Span Segment) • a fraction of the distance to the adjacent spans or supports (for all current codes this fraction is 0.25) • a fraction of the span length on each side of the span line (for all current codes this fraction is 0.25) • Code T-beam: the column strip width is the narrower of: • the span width • the Strip Boundaries (in the same latitude/longitude set as the Span Segment) • the web width plus 8 times the flange thickness on either side (ACI codes only) • 25% of the span length (ACI codes only) • the web width plus 0.07 times the span length on either side (AS 3600 and BS 8110 only) • the web width plus 0.058 times the span length plus 3 times the flange thickness on either side (IS 456 only) RAM Concept

• Manual: the column strip width is the narrower of: • the span width • the Strip Boundaries (in the same latitude/longitude set as the Span Segment) Design Column Strip for Column + Middle Strip Resultants instructs Concept to combine the column and middle strip forces into a single resultant at the centroid of the column strip cross section. The middle strip cross sections will still be generated, but the resulting forces in them will be zero. This can be useful, for example, when designing a beam with a column strip sized for the effective flange width and middle strips for the slab between the beam effective flanges. Using this option in this scenario will result in the beam cross section being designed for all forces in the entire bay. The middle strip cross sections will not have any design forces, but can still be designed for minimum reinforcement. Skew Angle The angle between the design strip cross section and a line perpendicular to the span segment. The typical value is zero. Min Number of Divisions Determines how many design cross sections per span. For N divisions there are N+1 design cross sections. It is generally advisable to make N an even number. The upside of more divisions is greater design accuracy; RAM Concept’s ability to find critical design locations and length of reinforcement is a function of the number of divisions. The downside of more divisions is that calculating takes longer; for large models, you might consider using a small number of divisions (say, 4) and then increasing the number for final design (but you should consider the effect of the next property). There is no reason for all design strips to have the same number of divisions. Should you be designing a transfer beam within a flat plate it would probably make sense to have more divisions for the beam design strip. Max Division Spacing Overrides the Min Number of Divisions with an upper bound on division spacing. Detect Supports and Edges Automatically (resets supports and widths below) This detects:

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Chapter 22 • the presence of supports at ends of span segments and overrides “Consider End as Support” and “Support Width”. • where the span spine is near the slab edge and “pulls back” the closest cross section by “x”, where x is the bar end cover plus 1 inch / 25 mm. • This is done by setting the support width to x. • If the spine end near the slab edge has detected a support, then the slab edge detection is NOT performed (and the regular support width calcs are used). Consider End 1 as Support These checkboxes allow Concept to determine your interpretation of “spans” in the structure. This determination of spans affects how Concept applies code rules that are span-related, including determining support regions, span regions and areas used in live load reduction. Support Width at End 1 The dimension of the support parallel to the design strip. The support width determines where the first and last design strip cross sections are located. Their locations are at half the support width (measured in the direction of the span) from the ends of the design strip. This is to facilitate reduction of moments to face of supports (it is thus important to start and end design strips at the center of supports). It is conservative to enter the support width as zero.

Inter Cross Section Slope Limit Reduces design strip cross sections based on slope limits. See “Inter Cross Section Slope Limit Trimming” on page 108 for more information. CS Top Bar The label used to identify the top face reinforcing bar used for flexural design. CS Bottom Bar The label used to identify the bottom face reinforcing bar used for flexural design. CS Shear Bar The label used to identify the reinforcing bar used for one-way shear design. The label is not necessarily the bar size. Reinforcement bar labels (and their properties) are specified in the Criteria > Materials. It is possible for different design strips to have different bars. After completing the calculation process, RAM Concept reports design strip reinforcement requirements based upon the bars specified in the design strip properties. You can view the required reinforcement area in plots and tables. CS Top Cover Clear cover to the top longitudinal bars. CS Bottom Cover Clear cover to the bottom longitudinal bars. CS Legs in Shear Reinforcement Determines the area of vertical shear reinforcement by multiplying the number of legs by the Shear Bar area. CS Torsion Design The method used for torsion design. See “Torsion Considerations” on page 405 of Chapter 51, “Section Design Notes” for further explanation. CS Design System The design system (beam / one-way slab / two-way slab) for the design strip. Minimum reinforcement and other rules are dependent upon what type of system is in use in the span. For example, the minimum requirements for beam stirrups are different to those for a one-way slab. CS Service Design Type (Eurocode 2 only) The service design type for members defined as PT for the design strip. The choices are: Stress: Perform a hypothetical stress limit design as prescribed in TR43.

Figure 22-7 Span segment properties - Column Strip

Crack Width: Perform a crack width design in accordance with Eurocode 2 clause 7.2/7.3.

Cross Section Trimming Reduces design strip cross sections based on geometry. See “About cross section trimming” on page 105 for more information.

Stress & Crack Width: Perform both Stress and Crack Width design. See Chapter 57, “BS EN 1992-1-1:2004 (Eurocode 2) with TR43 Design” for additional information.

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Chapter 22 CS Crack Width Limit (Eurocode 2 only) The crack width limit wmax to use when designing for Eurocode 2 clause 7.3. When “Code” is selected the values in UK National Annex Table NA.4 are used.

CS Min. Bottom Reinforcement Ratio The user defined reinforcement ratio for the bottom face.

CS Span Detailer The detailing system used. See “Span detailing” on page 415 of Chapter 53, “Reinforcement Notes”. The choices are: • None • Code • User-defined CS Min. Reinforcement Location Determines the face for minimum reinforcement. The choices are: Elevated Slab: Some minimum tensile reinforcement code rules do not consider flexural stress conditions; they determine minimum reinforcement based solely on geometry and the “expected” tensile face. For example, ACI 318-99 Rule 18.9.3.3 stipulates that the minimum reinforcement at a column in an elevated slab should be in the top face. This setting ensures RAM Concept uses that face. Mat Foundation: Similar to above, you would expect the minimum reinforcement at a column in a mat to be in the bottom face.

Figure 22-8 Span segment properties - Middle Strip

Note: Middle strips have one additional property to column strips. The rest of the properties are the same, but can have different values to those of the column strips. Middle Strip uses Column Strip Properties Sets the middle strip properties to those of the column strip.

Tension Face: This setting details the minimum reinforcement on the tensile face, or the face with the least amount of compression. Top: This setting details the minimum reinforcement on the top face, regardless of the concrete stresses. Bottom: This setting details the minimum reinforcement on the bottom face, regardless of the concrete stresses. None: No minimum reinforcement is detailed. CS Min. Top Reinforcement Ratio The user defined reinforcement ratio for the top face. Concept multiplies the trimmed cross sectional area by this ratio.

Figure 22-9 Span segment properties - Live Load Reduction

Max live Load Reduction See Chapter 52, “Live Load Reduction Notes” for information on Concept’s implementation of live load reduction.

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Chapter 22 User specified LLR parameters See Chapter 52, “Live Load Reduction Notes” for information on Concept’s implementation of live load reduction.

22.6.2 Drawing span segments manually

22.6 Creating span segments

To draw a single span segment:

You sometimes need to manually draw or adjust span segments for floors that are not rectilinear or have complications.

1 Choose the Span Segment tool (

You can create span segments in two ways: automatic and manual. For most models you use the automatic feature to generate span segments once in each orthogonal direction, and then make manual adjustments.

).

2 Click at the span segment start point. 3 Click at the span segment end point.

The two clicks define the span segment spine. To draw multiple span segments:

22.6.1 Generating span segments automatically

1 Choose the Span Segment Polyline tool (

Unless you have a truly one-way concrete floor, it would be usual to first generate one set of span segments (and hence design strips) on the Latitude Design Spans Plan, and then an orthogonal set on the Longitude Design Spans Plan.

3 Click at the first span segment end point.

To generate latitude span segments:

6 Right click and select enter to close the operation.

1 Click the Generate Spans tool (

), or choose Process >

Generate Spans. The Generate Spans dialog box appears.

).

2 Click at the first span segment start point.

4 Click at the second span segment end point. 5 Continue to click segment end points until all related

segments are drawn.

Note: Start and end points are normally supports. There are, however, exceptions, such as a design strip used for a pour strip to discriminate between PT and RC areas, or used for a span with user-defined reinforcement in discrete locations.

22.7 Creating span segment strips (design strips) You generate span segment strips from span segments. This can be done for all strips (on both latitude and longitude plans) or just selected strips. To generate span segment strips

1 Click the Generate Strips tool (


Generate Strips.

Note: The Generate Strips command does not generate 2 Set Spans to Generate to latitude. 3 Select other options and click OK.

The span segments appear (with nominated orientation) on the Latitude Design Spans Plan. You should repeat this process for the longitude direction.

strips for any span segment with the Lock Generated Strips checked. This is useful when you are satisfied with some, but not all, of the design strips.

Note: Each span segment can generate up to 3 strips: a center (“column”) strip, a left (“middle”) strip and a right (“middle”) strip. Together, these three strips form the entire span strip. To generate some span segment strips

1 Select one or more span segments 2 Choose the Generate Selected Strips tool (

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Chapter 22 Concept recalculates the span segment strips for the selected span segments.

22.8 Defining span segment widths and strip widths manually

Example 22-1 Figures 22-10 through 22-12 show the use of span boundaries to control the span segment width. Figure 22-13 shows an alternative.

Concept often generates span segment widths and strips that require modification. This tendency becomes apparent once you have tried the span segment generation a few times. You should always examine the strip widths to determine that they are to your satisfaction.

22.8.1 Defining span segment boundaries manually You can manually define the span segment width when the automatic span width calculation has not provided a satisfactory result. To set the span segment width:

1 Choose the Span Boundary Polyline tool. 2 Click at the span boundary start point. 3 Click at the next span boundary point. 4 Continue to click span boundary points until all are

defined. 5 Right click and select enter to close the operation.

Note: Boundaries with a span set of latitude (longitude) only affect latitude (longitude) span segment strips. Figure 22-10 Slab with span segments.

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Figure 22-11 Strips generated from the span segments in Figure 22-10. One span has some illogical design strips because the calculated span width is excessive.

Figure 22-13 The same span segment strips with the cross sections oriented to ninety degrees. This did not require manual span boundaries.

22.8.2 Defining strip boundaries manually You can manually define the “column” strip boundaries when the Column Strip Width Calc has not provided a satisfactory result. To set the strip boundary:

1 Choose the Strip Boundary Polyline tool(

).

2 Click at the strip boundary start point. 3 Click at the next strip boundary point. Figure 22-12 Regenerated design strips after modification of span width with span boundaries (shown inside ellipses).

4 Continue to click strip boundary points until all are

defined. Unequal spans are a source of varying column strip widths. You can choose to accept the column strip widths that Concept calculates, or make some modifications. BS8110 Clause 3.7.2.9 states the following: “Columns strips between unlike panels: Where there is a support common to two panels of such dimensions that the strips in one panel do not match those in the other, the division of the panels over the region of the common support should be taken as that calculated for the panel giving the wider column strip.” The column strips in the following example are modified with logic derived from this clause.

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Chapter 22 Example 22-2 Figures 22-14 through 22-16 show the use of strip boundaries to control the column strip width

Figure 22-16 Strip boundaries have made transitioning column strip widths Figure 22-14 Slab with span segments.

Note: The short span segments in Figure 22-16 have Column Strip Width Calc set to Manual Example 22-3 Figures 22-17 through 22-20 show the use of strip boundaries to control the column strip width.

Figure 22-15 Strips generated from the span segments in Figure 22-14.

Figure 22-17 Slab with span segments

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Figure 22-20 Strip boundaries have made a logical column strip width.

Example 22-4 Figure 22-18 Strips generated from the span segments in Figure 22-17. One span (with gray shading) has illogical span width and column strip width.

Short spans and cantilevers present problems for the design because Concept will generate narrow column strips. Codes recommend that columns strips are no more than half the span in width. Concept makes the (commonly used) assumption that the equivalent length of a cantilever is 2L. The cantilever column strip width is thus L. This can be quite narrow for short cantilevers.

Figure 22-19 Span boundaries have made a logical span width, but the column strip width is still a problem.

Figure 22-21 Slab with span segments

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Chapter 22

22.9 Cross Section Trimming RAM Concept automatically trims cross sections in span segment strips according to the trimming settings in the associated span segments.

22.9.1 About cross section trimming True cross section shapes in a slab can be quite irregular due to slab steps and other forming or architectural considerations. While it is generally advised to model the geometry of the concrete as per the form in the constructed building, it is not advised to always use the true geometry in design. It is often better to modify cross sections considering both their own shape and that of the nearby concrete. Concept offers two types of cross section trimming: Single Cross Section Trimming and Inter Cross Section Slope Limits.

Figure 22-22 Strips generated from the span segments in Figure 22-21.

Single Cross Section Trimming considers one cross-section at a time and modifies the cross-section based on the userspecified trimming type. Inter Cross Section Slope Limits trims the top and/or bottom of cross-sections based on the adjacent crosssections, their elevations, and the distance between the cross-sections. Inter Cross Section Slope Limit trimming always occurs after Single Cross Section Trimming.

22.9.2 About shear core It is important to understand “shear core” before using cross section trimming. Concept defines the shear core as the parts of the trimmed cross section that include any vertical slices that extend from the top of the cross section to the bottom of the cross section, as shown in Figure 22-24. Concept bases one-way shear calculations on the entire shear force and shear core. For example, in a T-beam the shear calculations are based on the cross-sectional area of the stem and the flange immediately above the stem.

Figure 22-23 Strip boundaries have made a logical column strip width.

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Cross-sections can have multiple separate cores. For example, in a double-T-beam, the core is the two stems and the flange areas above the two stems. Concept typically

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Note: The shear core is modified for post-tensioning ducts as described in “Concrete “Core” Determination” on page 405.

22.9.3 Shear core in slabs It is common for Concept to report unexpected shear reinforcement in slabs with section changes when the trimming is not set appropriately. It is quite possible for a slab cross section with a small shear core to show large amounts of shear reinforcement or even design failure, even when the shear force is small. See Section 22.9.5 for trimming settings for rectification.

Figure 22-26 Slab depression showing shear core (right). Such narrow shear core “slivers” often result in shear reinforcement and design failure.

22.9.4 Viewing a perspective of design strip cross sections Viewing a perspective of the design strip cross sections is a useful way of checking the validity of the design strip cross section trimming settings. To view the latitude design strip cross section perspective:

1 Choose Layers > Design Strips > Latitude Cross Sections

Perspective

Figure 22-24 Shear core (shaded) for various cross sections

Some odd shaped cross-sections do not have a shear core. In such cases, Concept cannot calculate some capacity values (such as shear capacity). See the example in Figure 22-25.

Figure 22-27 Design strip cross section perspective. Parts of the cross section not in the shear core are a different color.

narrow shear core

zero shear core: no vertical slice extends from top to bottom

Figure 22-25 One cross section with a narrow shear core and one with zero shear core.

22.9.5 Single Cross Section Trimming Concept offers six different types of single cross section trimming: Max Rectangle The top and bottom of the cross section is trimmed, and other pieces may be removed to produce a cross section with a uniform top and bottom elevation, and a maximum area. The “rectangle” formed may actually be

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Chapter 22 multiple separated rectangles with the same top and bottom elevations.

separated. Rectangles are considered the same as flangeless Tees. See the example in Figures 22-30 and 22-31.

Figure 22-28 Untrimmed slab showing cross-section (left) and shear core (right).

Figure 22-30 Untrimmed beam showing cross-section (left) and shear core (right). Figure 22-29 “Beam rectangle” trimming (left) and “Slab Rectangle” trimming (right) showing revised cross-sections. The shear core is now the same as the cross section.

Beam Rectangle Vertical slices of the cross section are removed until the remaining portion is the maximum height rectangle possible. This rectangle can be multiple separated rectangles with the same top and bottom elevations. See the example in Figures 22-28 and 22-29. Slab Rectangle The top and bottom of the cross section is trimmed to produce a cross section with a uniform top and bottom elevation, and a maximum width. If multiple maximum-width rectangles are possible, the deepest on (maximum area) is used. The “rectangle” formed may actually be multiple separated rectangles with the same top and bottom elevations. See the example in Figures 22-28 and 22-29.

Figure 22-31 “T or L” trimming showing revised section (left) and shear core (right).

Inverted T or L Same as T or L, but with the flange on the bottom. Max Shear Core The top and/or bottom of the cross section is trimmed to produce a cross section with the maximum shear core area. See the example in Figures 2232 and 22-33.

T or L The top and bottom of the cross section is trimmed, and other pieces may be removed to produce a cross section with a uniform top elevation, and only two bottom elevations (flange bottom and web bottom). The Tees and Els formed can be joined (such as double-tees) or

Figure 22-32 Untrimmed beam showing cross- section (left) and shear core (right).

Figure 22-33 “Max Shear Core” trimming showing revised section (left) and shear core (right).

None - No (single) cross section trimming is performed.

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22.9.6 Selecting cross section trimming You must determine which cross section trimming is most appropriate, but the following is provided for guidance:

A

t1

t2

Typical slabs with drop caps (but not drop panels):

A

The best trimming is usually Max Rectangle. Slabs with drop panels (but not drop caps):

The best trimming is usually T or L.

span direction

Figure 22-34 Elevation of thickened slab. It would be unrealistic to use a design depth of t2 at cross-section A-A.

Slabs with drop panels and drop caps:

The best trimming is usually T or L, but this assumes that the drop cap cross-sectional area is smaller than the drop panel cross sectional area. Down-turned beams:

The best trimming is usually T or L. Up-turned beams:

The best trimming is usually Inverted T or L. After a Calc-All, you can view the actual cross-section perspectives. See “Viewing a perspective of design strip cross sections” on page 106.

1

4

Figure 22-35 Elevation of effective design slab thickness using a slope limit of 0.25.

A slope limit of 0.0 will not allow any change between adjacent cross sections’ top elevations and bottom elevations. This effectively trims all the cross sections in a span segment strip to have the same top and bottom elevation. In general, we do not recommend using a slope limit over 0.25.

22.9.7 Inter Cross Section Slope Limit Trimming Once cross sections have been individually trimmed, they are trimmed relative to each other. This Inter Cross Section Slope Limit trimming effectively trims the top and bottom elevations of adjacent cross section to limit the slopes between them.

span direction Figure 22-36 Elevation of stepped slab. It would be unrealistic to use the full depth for all cross-section design.

This is done because compression and tension forces cannot “flow” at sharp angles from one cross-section to the next. Figures 22-34 through 22-37 show two examples with the Inter Cross Section Slope Limit set to 0.25. Figure 22-37 Elevation of effective design slab thickness using a slope limit of 0.25.

22.10 Improving the mesh The presence of design strips can significantly improve the regularity of the finite element mesh. We recommend that once you have completed the design strips, you regenerate the mesh. See Chapter 18, “Generating the Mesh” for more information.

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22.11 Additional design strip information

22.12 Irregular column layouts

RAM Concept automates a large percentage of the design strip process. It is relatively straightforward to rationalize the layout of design strips when the support arrangement is rectilinear.

Laying out design strips for irregular column layouts requires consideration of a number of issues.

The more complicated the geometry the more you have to think about the design strip layout and make manual changes.

These include: 1 Skew angles: whether latitude and longitude design strips

should be strictly orthogonal. 2 If tendons components from two directions are affecting

the design strip. If there is a lot of repetitive geometry in a floor then it should not be necessary to use design strips everywhere. You should only use as many as required to adequately design the floor. For example, if a floor has many beams of the same loading, tributary area, span and size then there is no need to use design strips for each similar beam. This is just as you would not perform hand calculations for each of twenty identical beams. Not withstanding, although slabs or beams may appear identical, continuity effects and other considerations may have a significant influence and the results could be different. It is better to define design strips properly in some critical areas than to cover the floor with unsuitable strips. When in doubt, draw a design strip, but keep in mind that the number of design strips affects the calculation time. Some engineering judgement is always a good thing. Keep in mind that any area without strips will not have the finite elements improved when you regenerate the mesh.

The following sections discuss these issues.

22.12.1 Design Strip Skew Angles It is intuitive that there would be a limit on the skew angle of design strips. One reference guideline is the Eurocode (EC2: 4.3.1.1 P(8)): “For slabs, deviations between the direction of the principal stress and the main reinforcement of less than 15 degrees may be ignored”. This suggests that flat slabs / flat plates should be designed for two directions that are between 75 and 105 degrees apart, which means the skew angle should not exceed fifteen degrees. The span segment property Skew Angle enables you to manipulate span segments such that design strip cross sections are normalized in each direction. This is shown in figures 22-38 through 22-41.

In general, design strips for one span set (latitude or longitude) should not overlap. For beam and slab systems, you might consider placing design strips parallel and in between the beams. This is because the beam strips only collect the moments and shears over the width of the strip. If the beams are not significantly stiffer than the slab, there may be design reinforcement required for the slab. The following sections discuss some situations with irregular geometry.

Note: See “Miscellaneous tips” on page 114 for some more tips and hints. Figure 22-38 Span segment 2-2 has an angle of 15 degrees. The skew angle is zero so the cross sections (shown in Figure ) are perpendicular to the span segment.

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22.12.2 Effect of tendon components on design strip cross sections In many instances the “latitude” and “longitude” tendons may be detailed and constructed in a non-orthogonal manner. This is often ignored in hand or strip calculations but it is a real issue that can affect design criteria such as service, strength and ductility. RAM Concept considers the force components of all tendons that cross a design strip cross section (or a design section). The following figures show an example.

Figure 22-39 Design strip cross-section

Figure 22-40 Span segment 2-2 has an angle of 15 degrees. The skew angle is minus fifteen degrees so the cross sections (shown in Figure 22-41) are parallel to those of adjacent spans

Figure 22-42 A skewed design strip with three design cross sections. The latitude tendons are not orthogonal to the longitude tendons.

Figure 22-43 Perspective shows the central cross section is perpendicular to the latitude tendons which are at the low point. Due to the layout the strip collects a component of the longitude tendon which is at its high point. This configuration may cause design issues. Figure 22-41 Revised design strip cross sections.

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22.12.3 Examples of irregular grids The following examples show design strip layouts for nonrectilinear grids. Example 22-5 Column and middle strips Figures 22-44 through 22-46 show the process of generating column and middle strips for an irregular grid. Figure 22-46 shows design strips, a number of which are not satisfactory. In particular, the 3-2 span segment strips do not adequately consider the slab near the “irregular” columns. Figures 22-47 through 22-50 show a better solution enabled with manual modifications. Figure 22-46 Design strips generated by Concept. Span 3-2 has unsatisfactory design strips.

Figure 22-44 Irregular column layout

Figure 22-47 Span 2-1, 3-2 and 4-1 deleted

Figure 22-45 Spans generated by Concept.

Figure 22-48 Manually drawn spans (2-1, 3-1, 4-1 and 5-1) after renumbering

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Chapter 22 Example 22-6 Full panel design strips for an irregular grid (ACI318 and TR43 post-tension design)

Figure 22-49 Regenerated design strips based on revised spans. Figure 22-51 Irregular column layout

Figure 22-50 Regenerated design strips after using the “Orient Span Cross Section” tool. Figure 22-52 Spans generated by Concept.

Figure 22-53 Design strips generated by Concept. Span 3-2 has unsatisfactory design strips.

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Figure 22-54 Span 2-1, 3-2 and 4-1 deleted

Figure 22-57 Regenerated design strips after using the “Orient Span Cross Section” tool.

22.12.4 Drawing design strips near walls There are some considerations for drawing design strips near walls. Omission of design strips parallel to walls

Since a wall is a continuous support, there is usually no need to design a floor over, and parallel to, a wall for strength. You may, however, be interested in the minimum reinforcement requirements and so a design strip could be warranted.

Figure 22-55 Manually drawn spans (2-1, 3-1, 4-1 and 5-1) after renumbering

Strips over or under walls will occasionally have unrealistic stress peaks as the forces and moments are continually transferred back and forth between the wall elements and the slab elements. For this reason, some designers eliminate span segments over and under walls.

Figure 22-58 Column and middle strips with strip omitted over wall.

22.12.5 Changing from PT to RC design Figure 22-56 Regenerated design strips based on revised spans.

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It is quite common for a floor to have a mixture of PT and RC areas. For example, a pour strip (an area with no posttensioning that joins two post-tensioned slabs).

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Chapter 22 For most codes, PT design rules are different from those for RC. As such, you should use multiple design strip segments in one span. Figure 22-59 shows two examples of a slab with tendons stopping either side of a pour strip (in gray). On the left, span segment 2-1 has been generated and extends from support to support. This means that the entire segment is designed according to the “Consider as PostTensioned” option. If the option is checked, then the pour strip design is wrong. On the right, span segments 1-1, 1-2(2) and 1-1 (3) have been drawn manually. The “Consider End x as Support” options have been unchecked, and support widths set to zero, where end “x” is at the pour strip. The “Consider as Post-Tensioned” option is checked for 11 and 1-1(3), but not 1-1(2). The pour strip is thus designed as reinforced, not post-tensioned, concrete. Concept designs the PT span segments for service stress rules and checks initial stresses, but not the RC areas.

22.13 Miscellaneous tips Middle strip support widths

Middle strip support widths are the same as those of the associated column strip. Should you require to use middle strips with a different support width (say, zero), you need to manually draw span segments for the column and middle strips and use the span boundary tool. Span segments that have no width

A span segment has zero width if the Span Width Calc is set to “manual” and some of its length does not have any span boundaries defined. Design strips (span segment strips) with no cross sections

You can specify a design strips’ minimum number of divisions as zero. Combined with a large maximum spacing, the number of cross sections could then be zero. This could be useful in affecting other span segments’ strip generation, without slowing down the calculations. (The overall number of cross sections has a significant effect on calculation time). For an example of this application, see steps 13 to 15 on page 365 of Chapter 48, “Mat Foundation Tutorial”.

22.14 A final word on design strips Figure 22-59 Multiple span segments used to model an RC pour strip.

Note: You could define the pour strip to have orthotropic behavior such that it is very flexible in the Y direction. This is done in the Mesh Input Layer. See “Slab area properties” on page 70 of Chapter 17, “Defining the Structure”.

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Design strips are extremely powerful tools, but that is all they are: tools. It is important that you understand the calculations that these tools perform, so you can determine the appropriateness of the calculation for the situation under consideration, and so you can set the tools’ parameters correctly.

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Chapter 23

23 Defining Design Sections A design section is the equivalent of one design strip cross section. You draw design sections manually to supplement design strips.

Bottom Ignore Depth The bottom concrete ignored in flexural and one-way shear design. See “About ignore depths” on page 116 for more information on this important issue.

23.1 Using design sections There are situations where you may choose to use design sections rather than design strips. This would include: • In some areas, you may only require design information at one cross section rather than for an entire span. • A design strip may not provide sufficient design information. • A design strip may be inappropriate. For example, a slab step may not be orthogonal to the span (and design strip) and you want the reinforcement bars designed perpendicular to the step. In this case, you might draw a design section parallel to the step. • You find it is too difficult to define a design strip for an area with very complicated structural geometry.

Figure 23-2 Design section properties - Design Parameters

Span Length Used to calculate the following: • Minimum reinforcement rules for some codes. • The upper bound on fps for unbonded tendons based upon the selected code’s criteria (these criteria often include a span length parameter).

23.2 Design section properties Design sections have similar properties to design strips. See “Span segment properties” on page 96 for definitions and explanations. The following properties are unique to design sections:

Tributary Length This creates a zone over which the reinforcement required by the design section must be provided (development lengths, if required, are in addition to this zone). The zone length on the right side of the design section is the smaller of these two values: • TributaryLength/2.0 • (SpanRatio - 0.0) * SpanLength The zone length on the left side of the design section is the smaller of these two values: • TributaryLength/2.0 • (1.0 - SpanRatio) * SpanLength The intent of the span-ratio-based limit is to restrain the reinforcement zone to within the span, even if the design section is at the beginning or end of a span.

Note: The Visible Objects dialog can be used to show the Figure 23-1 Design section properties - General

reinforced zone to be outlined and hatched. The region displayed also considers all the span ratio implications. The hatched region does not display before a calc-all.

Top Ignore Depth The top concrete ignored in flexural and one-way shear design. See “About ignore depths” on page 116 for more information on this important issue.

Span Ratio Determines the location of the design section relative to supports and midspan.

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Chapter 23 Strip Type (Eurocode 2 only) Determines the type of strip defined by this design section.

23.4 About ignore depths

The choices are:

Design sections use the full concrete section available unless overridden by “Top Ignore Depth” or “Bottom Ignore Depth”.

Col. Strip (Full Width): Use design rules for full bay width cross sections (generally used without middle strips). Col. Strip (w/ Mid. Strips): Use design rules for partial bay width column strips (generally used in conjunction with middle strips).

In many instances, it is inappropriate to use the full concrete cross-section properties of a design section for flexural and one-way shear design since some concrete is not effective.

Middle Strip: Use design rules for partial bay width middle strips (generally used in conjunction with column strips).

Note: Design section “ignore depth” settings are the

CS Service Design Type (Eurocode 2 only) The service design type for members defined as PT for the design strip.

equivalent of design strip “cross section trimming” settings. See “Cross Section Trimming” on page 105 of Chapter 22, “Defining Design Strips” for more information.

The choices are:

23.4.1 When to use ignore depths

Stress: Perform a hypothetical stress limit design as prescribed in TR43.

It is sometimes obvious when to use ignore depth. Often, however, engineering judgement is required to determine the use of ignore depth.

Crack Width: Perform a crack width design in accordance with Eurocode 2 clause 7.2/7.3. Stress & Crack Width: Perform both Stress and Crack Width design. See Chapter 57, “BS EN 1992-1-1:2004 (Eurocode 2) with TR43 Design” for additional information. CS Crack Width Limit (Eurocode 2 only) The crack width limit wmax to use when designing for Eurocode 2 clause 7.3. When “Code” is selected the values in UK National Annex Table NA.4 are used.

You should decide if the concrete is effective based on code rules and a practical assessment of the situation. There are too many permutations of concrete form to lay down rules, and, as such, the following is for discussion purposes only.

23.4.2 Examples of concrete form that should use ignore depth The following are examples of when design sections should ignore part of the concrete cross-section: Example 1

23.3 Drawing design sections When using design sections it is advisable to draw one set on the Latitude Design Spans Plan, and the other on the Longitude Design Spans Plan.

A two-way slab thickening that the building code deems does not comply as a drop panel. That is, a drop cap. You should ignore the incremental thickness of the drop cap below the slab. RAM Concept then only uses the drop cap for punching checks.

Design sections are located by a line that has a start point and an end point. To draw a design section:

1 Choose the Design Section tool (

).

2 Click at the design section start point. 3 Click at the design section end point.

Note: You can use relative coordinates to define exact lengths. Alternatively, you can draw User Lines to provide snap points to define exact lengths.

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Figure 23-3 Two-way slab with drop cap that should be ignored for flexure.

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Chapter 23 Example 2

A beam or slab that supports an upstand that is not an effective part of the concrete section. You should enter an appropriate “Top Ignore Depth” value.

If the slab is to be designed for the bending moment within the beam then you should consider the actual depth that can be mobilized for bending.

Figure 23-6 Slab supported by a beam that is effective for slab bending.

Figure 23-4 Beam with upstand to be ignored. Example 3

A beam or slab that deepens abruptly and the full depth of the concrete cannot be mobilized for flexure. You should enter an appropriate “Bottom Ignore Depth” value. Figure 23-5 shows bending moments in a slab perpendicular to a beam. For such an arrangement you need to decide if the slab should be designed for the bending moment at the face of the beam, or within the beam.

Figure 23-7 Slab supported by a deep beam that is not fully effective for slab bending. Ignore depth should be used for the design sections to utilize a shallower section.

23.4.3 Effect of ignore depth on reinforcement location RAM Concept locates reinforcement based upon the covers and ignore depth settings. You should consider this to ensure that reinforcement bars are designed at the appropriate depth.

Figure 23-8 Using ignore depth to locate reinforcement bars at the correct elevation. Figure 23-5 Slab bending moments

If the slab is to be designed for the bending moment at the face of beam, then it is a matter of locating a design section within the slab depth.

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23.5 A final word on design sections Design sections are powerful tools, but that is all they are: tools. It is important that you understand the calculations

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consideration, and so you can set the tools’ parameters correctly.

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Chapter 24

24 Defining Punching Shear Checks Punching shear is often a critical consideration when designing slabs, In particular, post-tensioned slabs are usually thinner than their reinforced counterparts and hence punching considerations are even more important.

24.1 About punching shear checks RAM Concept can calculate punching failure planes and the punching shear stresses due to column reactions (Fz, Mx, My). RAM Concept is not infallible in its determination of potentially critical sections. For unusual geometries, RAM Concept may not check the appropriate section and / or may check inappropriate sections that give higher than appropriate stress ratios. You should review RAM Concept’s selections of potentially critical sections and use engineering judgment to decide if RAM Concept’s selections and the application of the ACI 318 model are appropriate.

24.2 Punching shear check properties and options The following explains the general and code specific Punching Shear Check properties and options.

24.2.1 General Maximum Search Radius The radius that defines the area RAM Concept searches for potential failure locations. The analysis is conservative when you set a very large radius, but this has two detrimental effects: Concept will need to review a larger area of slab and hence take longer to check that punching location. More importantly, Concept will consider slab openings that are far from the column in determining the potentially critical section that may result in a smaller critical section than is appropriate. Cover to CGS The distance that will be subtracted from the slab depth in each region to determine the “effective depth” for critical section calculations. For columns under, this is usually the distance from the top of the slab to the bottom of the top bar. Concept subtracts this distance from the slab thickness to determine the “d” distance. If the depth in any region is smaller than the specified Cover to CGS, the region is treated as a hole.

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Angle This is the angle of the first ray measured counterclockwise from the global x-axis. Number of Desired Sections per Zone A zone can be envisioned as a region outside a column, drop cap, beam, etc. A column connection in a simple plate will have only one zone. A column connection with a drop cap will have multiple zones. This property enables Concept to determine how many sections you want to generate in each of these “zones”. This property can be used to eliminate unwanted sections, but caution should be used when reducing the desired number of sections. The sections generated are based upon the minimum critical section cross-sectional area, and they are not actually analyzed until after they are generated. By setting this value to 1 you would be likely to get only the most critical section in each zone but this is not guaranteed. Edge Treatment This determines how RAM Concept treats edges and openings. An edge treatment of Sector Voids is always conservative. For columns near a slab edge, however, the Sector Voids setting stops the critical section before it reaches the slab edge (at a ray from the column center to the slab edge that has a length equal to the search radius). An edge treatment of Failure Planes probably produces better results for critical sections at edge and corner locations. This setting, however, requires you to review the results more carefully to ensure that Concept has checked all the appropriate sections. An edge treatment of Ignore Edges is generally unconservative. You may want to try this setting to see if Concept finds a critical section that it missed with the other settings. Connection Type This determines which column classification Concept uses for calculating allowable stresses. A Corner type uses corner column rules (post-tensioning is ignored). An Edge type uses edge column rules (post-tensioning is ignored). An Interior type uses interior column rules (Concept considers the section as post-tensioned if the P/A exceeds 125 psi). An Auto type determines if the column is corner, edge or interior type based upon the total void angle around it. If the void angle is less than 90 degrees then the column is an interior type. If the void angle is between 90 and 180

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Chapter 24 degrees then the column is an edge type. If the void angle is 180 degrees or more then the column is a corner type. See “Column connection type” on page 650 of Chapter 66, “Punching Shear Design Notes” for more information. Use Ancon Shearfix SSR System If this option is selected then the Ancon Shearfix system will be used for any necessary SSR design. SSR System The stud shear reinforcement system used, if required, for design. These systems can be edited on the Materials page. This selection is only applicable if the “Use Ancon Shearfix SSR System” is not selected. Max Overhang Factor The maximum distance, as a function of effective depth “d”, to allow the critical sections to extend from the originating shape. Align with Rectangular Columns Aligns the punch check angle with the rectangular column angle during a “calc all”.

Use ACI-421.1R-99 Increased Max Stud Spacing Suggestion Allows higher maximum stud spacings, depending upon the stress levels in the critical sections.

Note: Although ACI 421.1R-99 is an ACI publication, it is not officially recognized by the ACI 318 standard. As such, it should only be utilized under the discretion and judgment of an Engineer with a full understanding of the provision and its recommendations. 24.2.3 AS3600 specific options Closed Ties In R/S-Axis Torsion Strip Use these options if you are providing minimum closed ties in the torsion strips in accordance with AS3600. Concept does not actually design this reinforcement, but uses the appropriate code provisions in calculating the punching capacity. You should ensure that this reinforcement is provided if using these options.

Design SSR if Necessary Generates an SSR design (if possible) where the unreinforced strength is insufficient.

24.2.4 BS 8110/EC2 specific options

Align SSR w/ Punch Check Axis Aligns the SSR with the punch check axis. For example, it is intended to be used when the slab edge is not parallel to the column faces and it would be preferable to have the rails align with the slab geometry instead of the column face.

Rail Layout Pattern Controls the layout of the primary rails around a column. The cruciform layout selection will provide parallel rails along each column face and a diagonal rail in each corner. The radial layout selection will provide rails that are radial from the punch check center. Note that for columns with small dimensions it is possible for the layout selection to produce identical layouts.

Note: This last option is not available for AS3600 as the SSR are always aligned with the punching check axis.

24.2.2 Ancon Shearfix Parameters Top and Bottom Cover The cover is used in conjunction with the slab depth to determine the physical rail depth. Stud Size The Ancon Shearfix stud size (diameter) to use in the design. If “auto” is selected, RAM Concept will design the smallest stud size possible for the maximum stud spacing and fixed rail layout.

Note: These parameters are only used when the “Use Ancon Shearfix SSR System” option is selected. Use ACI 421.1R-99 Increased Max Vn Suggestion Allows the use of a higher maximum ΦV n for SSR design. Use ACI-421.1R-99 Increased Vc Suggestion Allows the use of a higher vc value for use in strength computations for SSR design.

Apply supplemental max stress limit This option provides a supplemental maximum stress limit on the basic control perimeters as suggested in the paper “Effectiveness of punching shear reinforcement to EN 1992-1-1:2004” in The Structural Engineer 87 (10) May 2009. Reinforcement Ratio For specification of “ ρ 1 ” for equation 6.47. You should calculate the input value using the equation in clause 6.4.4 of the EN 1992-1-1:2004 code. Beta Factor This represents a ratio of the maximum stress on a critical section (including shear and moment transfer) over the maximum stress due to shear only. This option allows the user to select “Auto Calc”, 1.15 (interior), 1.4 (edge), 1.5 (corner), or input any positive value for Beta directly. The factors for each column condition are taken from clause 6.4.3 (6) of the EN 1992-1-1:2004 Code and are meant to be used only when lateral stability does not depend upon frame action and where adjacent spans do not differ in length by more than 25%. “Auto Calc” uses the model and calculation methods described in Chapter 66, “Punching Shear Design Notes”.

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24.3 Drawing punching shear checks You can draw punching shear checks for all columns simultaneously. To draw punching shear checks:

1 Choose Layers > Design Strips > Punching Checks Plan. 2 Select the Punching Shear Check tool (

).

3 Fence the columns.

24.4 A final word on punching shear checks Punching shear checks are extremely powerful tools, but that is all they are: tools. It is important that you understand the calculations that these tools perform, so you can determine the appropriateness of the calculation for the situation under consideration, and so you can set the tools’ parameters correctly.

A circle of the prescribed radius appears at each column within the fence.

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Chapter 25

25 Drawing Reinforcement Bars Note: Drawing your own reinforcement bars is not necessary but an advanced feature you may wish to utilize once you are experienced with the program. The Reinforcement layer allows you to: • supplement the Program reinforcement by drawing actual (User) bars on plans using various tools • change some Program bars to User reinforcement

• Transverse Individual Bars - single transverse bars (strirrups/links/ligatures) that are generated from Transverse Reinforcement • Stud Shear Reinforcement (SSR) Callouts - a fixed number of SSR rails with a fixed number of studs. • SSR Rails - individual rails that are generated from SSR Callouts.

The Reinforcement layer facilitates a production quality reinforcement layout.

You can directly create (by drawing) Concentrated Reinforcement and Distributed Reinforcement. You cannot directly create any of the other types of reinforcement.

25.1 Reinforcement bar definitions

25.2 Reinforcement properties

25.1.1 About User and Program Reinforcement There are two types of reinforcement bar: Program and User. All reinforcement is tagged (identified) as one type or the other. When performing design calculations, Concept generates Program reinforcement required in addition to any existing User reinforcement. In subsequent calculations, Concept removes all of the Program reinforcement before starting the calculations. You can change Program Concentrated Reinforcement to User Concentrated Reinforcement merely by changing its tag (in the object properties window). You might do this to modify Concept's design. When performing subsequent calculations, Concept only designs reinforcement needed in addition to the reinforcement tagged as User.

Figure 25-1 Concentrated rebar properties - General

You could also change “User” reinforcement to “Program” reinforcement, but this has no value since Concept removes all existing program reinforcement when it generates new “Program” reinforcement.

25.1.2 Reinforcement object types There are seven object types in the Reinforcement layer: • Concentrated Reinforcement - a fixed number of bars over a parallelogram area • Distributed Reinforcement - a bar spacing applied over a polygon area. • Individual Bars - single bars that are generated from Concentrated and Distributed Reinforcement.

Figure 25-2 Distributed rebar properties - General

• Transverse Reinforcement - a fixed number of transverse bars at a fixed spacing. RAM Concept

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Chapter 25 Span Set Determines the set the reinforcement belongs to: latitude or longitude.

Skew Reinforcement Extent tool” on page 128 for more information).

Elevation Reference The choices are:

Quantity Type The choices are:

• Absolute: the elevation relative to the zero datum. This is not recommended other than for very complicated geometry.

• Quantity: number of bars • Spacing: bar spacing

• Above Soffit: The elevation is measured from the soffit elevation to the center of the bar.

Number of bars Only editable if Quantity Type is set to Quantity

• Above Surface: The elevation is measured from the surface elevation to the center of the bar. The value is almost always negative

Spacing Only editable if Quantity Type is set to Spacing.

• Top Cover: The elevation is measured from the surface elevation to the top of the bar. The value is always positive. • Bottom Cover: The elevation is measured from the soffit elevation to the underside of the bar. The value is always positive. Elevation The distance used with the elevation reference. Ending at End 1 The choices are: • Straight: • 90 Hook:

Orientation The plan angle of the reinforcement (distributed reinforcement only - see “The Orient Reinforcement tool” on page 128 for more information). Zone Width The width of the concentrated reinforcement zone. Designed By The choices are: • User: Bars drawn by the user • Program: Bars calculated and drawn by Concept.

Note: See “Concentrated and distributed reinforcement callouts” on page 131 for discussion on the second (Presentation) tab.

• 180 Hook: • Anchored:

25.3 About drawing reinforcement

Ending at End 2 Similar to End 1 Slab Face This is used for (1) graphic display purposes (2) design rules. The choices are: • Per Elev. Reference - the default and typical setting

You can draw reinforcement in a number of ways: • A group of one or more concentrated reinforcement bars using one of the three Concentrated Reinforcement tools. • A group of distributed reinforcement bars using one of the three Distributed Reinforcement tools

• Top • Bottom • Both • Auto

Note: Special Caution - Reinforcement set to “Auto” face will not appear on either the “top” or the “bottom” reinforcement plans. If you use “Auto” face reinforcement, change the default plan settings (or add some plans) to be certain that all of the reinforcement used is visible on the plans in your report. Bar Type The label used to identify the reinforcing bar. The label is not necessarily the bar size. Reinforcement bar labels (and their properties) are specified in the Criteria > Materials.

25.3.1 Expected workflows It is expected that you will typically convert the “Program” reinforcement to “User” reinforcement and modify it. One common exception to this might be that you may want to specify a bottom mat of reinforcement. There is no difficulty if you convert some reinforcement and directly draw other reinforcement.

25.4 Drawing concentrated reinforcement Concentrated reinforcement consists of one or more bars located within a parallelogram.

Bar Extent Skew The orientation of the bar’s extent line in degrees (concentrated reinforcement only - see “The

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Chapter 25 The parallelogram is initially a rectangle with a default width, but you can use the stretch tool to edit the width and the skew tool to change the shape.

25.5 Drawing distributed reinforcement Distributed reinforcement consists of a group of bars located within a polygon.

25.4.1 Drawing concentrated reinforcement You can draw concentrated rebar by specifying the end points or specifying the midpoint and one endpoint. To draw concentrated reinforcement #1:

1 Select the Concentrated Reinforcement tool (

).

25.5.1 Drawing distributed reinforcement You draw distributed reinforcement within a polygon. This is done by defining the polygon with mouse clicks or using the slab perimeter.

2 Click at one endpoint.

To draw distributed reinforcement #1:

3 Click at the other endpoint.

1 Choose the Distributed Reinf. tool (

Note: See Example 25-1 “Drawing concentrated bottom

2 Click at each polygon vertex consecutively.

bars” on page 126 for more information.


).

type “c” and press Return). To draw concentrated reinforcement #2:

1 Select the Concentrated Reinforcement tool (

).

2 Click at the midpoint. 3 Click at one endpoint.

Note: This creates two objects: a polygon and a reinforcement object that belongs to either the latitude reinforcement layer or longitude reinforcement layer.

Note: Once the file is run you can view the individual bars


through the Visible Objects dialog box.

bars by defining the midpoint” on page 126 for more information.

Note: See Example 25-4 “Drawing distributed bottom

25.4.2 Drawing concentrated reinforcement in two directions


You can draw concentrated rebar in two directions by specifying the midpoint and one endpoint.

2 Click somewhere on the slab.

bars over part of the floor” on page 127 for more information.

1 Choose the Distributed Reinf. in Perimeter tool (

).

3 Click at another point to define the orientation of the

To draw concentrated reinforcement in two directions:

reinforcement.

1 Select the Concentrated Reinforcement Cross tool

Note: This creates two objects: a polygon matching the

(

slab outline and a reinforcement object that belongs to either the latitude reinforcement layer or longitude reinforcement layer.

).

2 Click at the midpoint. 3 Click at one endpoint.

Note: Once the file is run you can view the individual bars.

Note: This creates two reinforcement objects: one that

Note: See Example 25-5 “Drawing distributed bottom

belongs to the latitude reinforcement layer and one that belongs to the longitude reinforcement layer.

bars over the entire floor” on page 127 for more information.



bars in two directions” on page 126 for more information.

1 Choose the Distributed Reinf. Cross in Perimeter tool

(

).

2 Click somewhere on the slab. 3 Click at another point to define the orientation of the

reinforcement.

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Chapter 25 A polygon appears that is the shape of the slab. Once the file is run you can view the individual bars.

Example 25-2 Drawing concentrated bottom bars by defining the midpoint

Note: This creates three objects: a polygon matching the slab outline, a reinforcement object that belongs to the latitude reinforcement layer and a reinforcement object that belongs to the longitude reinforcement layer.

Note: See Example 25-6 “Drawing a bottom mat over the entire floor” on page 128 for more information.

25.6 Concentrated and distributed reinforcement drawing examples Example 25-1 Drawing concentrated bottom bars

Figure 25-4 Concentrated bars drawn by clicking at points A and B with the second Concentrated Reinforcement tool.

Example 25-3 Drawing concentrated bottom bars in two directions

Figure 25-3 Concentrated bars drawn by clicking at points A and B with the first Concentrated Reinforcement tool.

Figure 25-5 Concentrated bars in two directions drawn by clicking at points A and B with the Concentrated Reinforcement Cross tool.

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Chapter 25 Example 25-4 Drawing distributed bottom bars over part of the floor

Example 25-5 Drawing distributed bottom bars over the entire floor

Figure 25-6 Distributed bar polygon drawn over part of the slab by clicking at 5 vertices with the Distributed Reinforcement tool. Hatching is turned ON.

Figure 25-8 Distributed bars polygon drawn over the slab by clicking at points A and B with the Distributed Reinforcement in Perimeter tool. Hatching is turned ON.

Figure 25-7 Individual distributed bars shown via Visible Objects dialog box. Hatching is turned OFF.

RAM Concept

Figure 25-9 Individual distributed bars shown via Visible Objects dialog box. Hatching is turned OFF.

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Chapter 25 Example 25-6 Drawing a bottom mat over the entire floor

25.7.1 The Orient Reinforcement tool This tool allows you to draw a line segment that represents the desired orientation of selected reinforcement objects’ individual bars. After you draw this line, Concept rotates any selected concentrated reinforcement objects, and orients any distributed reinforcement parallel to the drawn line. The selected reinforcement creates individual bars of the same orientation after calculation. To change the reinforcement orientation:

1 Select the reinforcement object. 2 Choose the Orient Reinforcement tool (

).

3 Click anywhere on the plan. 4 Click at a location on the plan to create a line parallel to

the desired direction of the reinforcement. Figure 25-10 Distributed bottom mat polygon drawn over the slab by clicking at points A and B with the Distributed Reinforcement Cross in Perimeter tool. Hatching is turned ON.

Note: Use snap orthogonal or snap to perpendicular to help with orientation where appropriate

Note: Selecting both reinforcement objects created with the Concentrated Rebar Cross tool or the Distributed Rebar Cross in Perimeter tool orientates both reinforcement objects.

Note: See Example 25-7 “Orientating concentrated reinforcement” on page 129 for more information.

25.7.2 The Skew Reinforcement Extent tool This tool allows you to draw a line segment that represents the desired orientation of selected Concentrated Reinforcement objects' extent line. This tool allows you to create parallelogram regions of Concentrated Reinforcement. Distributed reinforcement cannot be skewed. To skew the reinforcement extent

1 Select the concentrated reinforcement object. Figure 25-11 Individual distributed bars shown via Visible Objects dialog box. Hatching is turned OFF.

2 Choose the Skew Reinforcement Extent tool (

).

3 Click anywhere on the plan (but preferably near the

reinforcement object)

25.7 Other reinforcement plan tools

4 Click at a location on the plan to create a line parallel to

There are three special tools in the Reinforcement layer that you can use to edit the plan properties of reinforcement.

Note: See Example 25-8 “Skewing concentrated

the desired extent line. reinforcement” on page 130 for more information.

25.7.3 Auto Hook tool This tool allows you to automatically extend concentrated rebar callouts in close proximity to the slab edge and apply hooks to a selected set of user reinforcement.

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Chapter 25 To apply hooks to reinforcement near the slab edge

1 Select the user concentrated reinforcement that you wish

to modify. 2 Choose the Auto Hook tool (

Example 25-7 Orientating concentrated reinforcement

).

3 Select the hook type from the drop down menu. 4 Set the Edge Detection Tolerance. Only bar ends within

this distance of a slab edge will be modified. 5 If you want the bar end extended to the slab edge, check

the “Perform Bar Extension” box and set the desired edge cover and bar rounding length. 6 Click “OK”.

Note: See Example 25-10 “Automatically applying hooks to user reinforcement” on page 131 for more information.

Figure 25-12 Using the Orient Reinforcement tool to define the line A B parallel to the desired orientation

Figure 25-13 The reoriented concentrated reinforcement

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Chapter 25 Example 25-8 Skewing concentrated reinforcement

Figure 25-14 Using the Skew Reinforcement tool to define the line A B parallel to the desired skewed ends

Figure 25-15 The skewed concentrated reinforcement with the extent line parallel to line AB.

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Example 25-9 Stretching concentrated reinforcement

Figure 25-16 Using the stretch tool at point A to widen the concentrated reinforcement parallelogram

Figure 25-17 The stretched concentrated reinforcement

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Chapter 25 Example 25-10 Automatically applying hooks to user reinforcement

modify so the reinforcement is described per your office standards.

25.9.1 Concentrated and distributed reinforcement callouts

Figure 25-18 Use the auto hook tool to apply hooks to all four concentrated bar callouts

Figure 25-20 Concentrated rebar properties - Presentation

Figure 25-19 Hooks applied and bars extended to the slab edge

Figure 25-21 Distributed rebar properties - Presentation

25.8 Layout and Detailing Parameters There are five calculation option parameters that influence how Concept lays out and details reinforcement. Refer to “Reinforcement layout and detailing parameters” on page 151 of Chapter 28, “Calculating Results”.

The Concentrated and Distributed Reinforcement format specifiers use the following key values: • $Q - Bar quantity • $F - Bar face • $B - Bar name • $L - Bar length

25.9 Reinforcement Text Formatting:

• $U - Bar length units • $u - Bar spacing units

Concentrated Reinforcement, Distributed Reinforcement and SSR Callouts all have format specifiers that you can

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• $S - Bar spacing • \n - Start new line 131

Chapter 25

25.9.2 Examples of reinforcement text formatting The following examples show generated text for different codes.

25.9.3 SSR Callout The SSR Callout format specifiers use the following key values: • $R - Rail quantity

Example 25-11 ACI 318-05

• $S - Studs per rail

The Concentrated Reinforcement format specifier “$Q $B x $L $U $F@$S $u” would generate text on the plan view such as:

• $F - First stud spacing

28 #5 x 15 feet T @ 12.1 inches

• $U - Stud spacing units

For the same Concentrated Reinforcement, the format specifier ($Q)$Bx$L$F” would generate the text:

• $S - Stud spacing

(28)#5x15T Example 25-12 AS 3600-2001 The Concentrated Reinforcement format specifier $Q $B x $L $U $F@$S $u” would generate text on the plan view such as: 28 N16 x 4.57 m T @ 307 mm For the same Concentrated Reinforcement, the format specifier “($Q)$Bx$L$F” would generate the text:

• $T - Typical stud spacing • $N - SSR system name

• \n - Start new line The SSR Callout format specifier “($R)$S@$T First Spacing = $F $U\n$N” would generate text on the plan view such as: (12)8@3 First Spacing = 2.5 inches 3/8” SSR For the same SSR Callout, the format specifier “$R rails with $S studs” would generate the text: 12 rails with 8 studs

(28)N16x4.57T Example 25-13 BS 8110 : 1997, EC2 and IS456-2000 The Concentrated Reinforcement format specifier $Q $B x $L $U $F@$S $u” would generate text on the plan view such as: 28 T16 x 4.57 m T @ 307 mm For the same Concentrated Reinforcement, the format specifier “($Q)$Bx$L$F” would generate the text:

25.10 About SSR callouts and SSR rails: Concept generates SSR Callouts and SSR Rails from the results of its punching shear calculations. This generated reinforcement is for display purposes only - it is not used in calculations and cannot be changed to “user” reinforcement.

(28)T16x4.57T

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Chapter 26

26 Defining Tendons Note: You could bypass this chapter if you are designing a structure with only bar reinforcement. There is no unique quantity or layout of post-tensioning that provides a satisfactory PT design. This is particularly true with partial prestress design where the emphasis is on strength, deflection and crack control rather than hypothetical service stresses. Historically, many 2D programs have used allowable service stresses to drive their algorithms for providing a PT solution. This is fast losing favor; some codes have all but abandoned using (hypothetical) service stresses as a design criterion, and other codes (such as ACI 318) are moving in that direction. Some computer generated tendon layouts are not practical for real design. Whereas you expect a 2D program to help provide a workable tendon design based upon spans, sections and loads, the possible randomness of supports makes this extremely difficult in 3D. Thus, in RAM Concept, it is necessary for you to define the tendons by generating or drawing them in plan and specifying parameters such as profile and number of strands. For guidance, you should use one of the following for your first estimate: • your experience • a preliminary run with Strip Wizard • a logical guess based upon precompression (P/A) considerations • a random guess (correctly drawn design strips flag incorrect guesses, and you can use “The Auditor” for help in iterating)

26.1 Tendon definitions

26.1.1 Post-Tensioning terminology and definitions • Strand - a single wire or group of bundled wires. In posttensioned construction a strand is a unit of post-tensioning reinforcement, similar to a reinforcing bar being the unit of RC reinforcement.

• Duct - a tube, conduit, or sheathing containing one or more strands with a single anchorage. The maximum number of strands in a duct is defined in the prestressing material properties. For monostrand tendons (bonded or unbonded), each duct contains a single strand. • Tendon - In practice, the PT industry defines a tendon as a group of strands that share a common anchorage. The “group” may be just one strand, as is the case with most unbonded systems, or “monostrand”. It is not always necessary for real tendons to match Concept tendon exactly. For example, it is common practice in monostrand to group tendons together in the field. For this situation, it is usually convenient to specify the total number of strands in the group in a single Concept tendon. In this case the correct number of ducts can still be calculated correctly using the input duct properties.

26.1.2 Using the latitude and longitude prestressing folders RAM Concept has two folders for prestressing called latitude and longitude. By using Concept’s two tendon folders, you can separate tendons and tendon parameters into two groups. Separating orthogonal tendons allows for easier editing and a clearer presentation. Each folder contains three layers: • Tendon Parameters Layer - defines high level objects used for the generation of individual tendons. This layer facilitates a production quality presentation of high level tendon layout information. • Generated Tendon Layer - contains the individual tendons generated from the parameter objects on the Tendon Parameters Layer. The generated individual tendons can not be edited, but can be selected and copied to the Manual Tendon Layer for further manipulation. • Manual Tendon Layer - contains individual tendons drawn or otherwise manipulated manually by the user. During analysis and design, all tendons on the generated tendon layers (latitude and longitude) and the manual tendon layers (latitude and longitude) are included in the calculations. Therefore it is important not to duplicate tendons on the generated and manual layers.

Note: Latitude and longitude are just names. You could define all tendons, which might be at various plan angles, on one plan.

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Chapter 26

26.2 Tendon Parameters Layer

26.2.2 Banded Tendon Polyline and Distributed Tendon Quadrilateral Properties

26.2.1 Tendon Parameters object types There are five object types in the Tendon Parameters Layer: • Banded Tendon Polyline - a polyline representing a specification for generation of a group of tendons at a fixed spacing and parallel to the polyline segments. • Distributed Tendon Quadrilateral - a quadrilateral representing a specification for generation of an array of tendons at a specified angle within the shape. • Distributed Tendon Overlap - a graphical only object that displays the cumulative force or number of strands in an area of overlapping distributed tendon quadrilaterals.

Figure 26-1 Distributed tendon quadrilateral properties - General

• Tendon Void - a polygon shape that represents an area where no tendons are to be generated. Typical usage might be stressing blockouts or small slab areas that are too short for tendons to get stressed. • Profile Polyline - a polyline that defines a tendon elevation at the location where any banded tendon polyline or distributed tendon quadrilateral intersects it.

Figure 26-2 Banded tendon polyline properties - General

Tendon Specification Type Determines the mode for specifying strand quantities that go into the generated tendons. The choices are: • Force • Strands Effective Force Only enabled when “force” is selected for “Tendon Specification Type”. For banded tendon polylines, this value represents the total effective force to be generated in the banded group. For distributed tendon quadrilaterals, this represents the effective force per unit width of slab to generate in the distributed tendon array.

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Chapter 26 Number of Strands Only enabled when “strands” is selected for “Tendon Specification Type”. For banded tendon polylines, this value represents the total number of strands to be generated in the banded group. For distributed tendon quadrilaterals, this represents the number of strands per unit width of slab to generate in the distributed tendon array.

Inflection Point Ratio Determines the distance, x, from end 1 in the span to the point where the tendon curvature changes sign. The inflection point ratio is the ratio of x to the distance from end 1 to end 2. A value of 0.2 places the inflection point 10% of the span distance from end 1 if end 2 is at midspan. This is a commonly used value.

Max Strands/Tendon For banded tendon polylines, this value defines the maximum number of strands to put into a single generated tendon.

parabola.

Layout Type For banded tendon polylines, this value defines the layout type of the generated tendons. The choices are: • Spacing • Width Tendon Spacing Defines the lateral spacing between generated tendons.

Note: An inflection point ratio of zero results in a simple Harped Specifies the tendon segment as having a straight profile (as opposed to a parabolic profile).

26.2.3 Distributed Tendon Overlap and Tendon Void Properties These objects have no user editable properties

26.2.4 Profile Polyline Properties

Layout Width For banded tendon polylines, defines the total width of the generated tendon layout when “width” is selected for “Layout Type”. The width includes a half space on each side of the outermost generated tendons.

Elevation The vertical distance from the elevation reference to the centroid of the tendon’s strands, also referred to as CGS (center of gravity of strand).

Tendon Type For banded tendon polylines, defines the behavior of the banded tendon polyline and the properties of the generated tendon. The choices are:

bottom cover to the CGS of the strands. Future versions will allow inputting of duct dimensions and allow a top and bottom cover to the outside of the duct to be input.

Note: This version of RAM Concept measures the top and

• Primary

Note: The CGS is not the same as mid-depth of a bonded

• Added

tendon’s duct.

Added Tendon Generation For banded tendon polylines, controls the behavior of the automatic generation of added tendons to balance forces at connected banded tendon polyline ends. The choices are: • None • Fixed Length • Span Fraction Added Tendon Length For banded tendon polylines when “Fixed Length” is selected for “Added Tendon Generation”, controls the length of the automatically generated banded tendon polyline. Added Tendon Span Fraction For banded tendon polylines when “Span Fraction” is selected for “Added Tendon Generation”, controls the length of the automatically generated banded tendon polyline as a function of the span containing the joint that the added tendon is attached. PT System The label used to identify the PT system for the generated tendons. The label is not necessarily the size and type of strand. The Materials Specification defines the PT system properties. It is possible to mix systems in a single tendon parameters layer.

RAM Concept

Elevation Reference The choices are: • Absolute: the elevation relative to the zero datum. This is not recommended other than for very complicated geometry. • Above Soffit: The elevation is measured from the soffit elevation to the CGS of the tendon. • Above Surface: The elevation is measured from the surface elevation to the CGS of the tendon. The value is almost always negative. • Top Cover: The elevation is measured from the surface elevation to the CGS of the tendon. The value is always positive. • Bottom Cover: The elevation is measured from the soffit elevation to the CGS of the tendon. The value is always positive. Profile Location Determines the orientations of the created tendon half-spans (and the corresponding inflection point location). The choices are: • Support • Span

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Chapter 26 The support profile polylines are displayed graphically as solid lines on plan, while the span polylines are displayed as dashed lines.

• Above Surface: The elevation is measured from the surface elevation to the CGS of the tendon. The value is almost always negative.

Before you begin drawing tendons, specify the default properties for the tool(s) you will use. The default values are set in the Default Properties dialog box. Double click one of the tendon drawing tools (Half Span Tendon ( ), Half Span Tendon Panel (

Full Span Tendon Panel (

• Absolute: the elevation relative to the zero datum. This is not recommended other than for very complicated geometry. • Above Soffit: The elevation is measured from the soffit elevation to the CGS of the tendon.

26.3 Tendon properties

Full Span Tendon (

Elevation Reference The choices are:

), ), or

)) to edit its properties.

Note: Setting the default properties for one tendon drawing tool sets properties for all the tendon drawing tools. The following is a list of RAM Concept tendon properties: PT System The label used to identify the PT system for the generated tendons. The label is not necessarily the size and type of strand. The Materials Specification defines the PT system properties. It is possible to mix systems in a single tendon layer. Strands per Tendon Specifies the number of strands in the selected tendon(s). It need not be an integer value. While the total number of strands in Concept and the real structure must match, the grouping of strands into tendons need not be the same in Concept as in the real structure. It is usually not necessary to model each real tendon as a Concept tendon - fewer Concept tendons (with a larger number of strands per tendon) are often used. An exception is for specific code rules that require a deduction in shear area for duct size. In those situations you should specify the correct duct size and number of strands per tendon. For example, if you model six 4-strand ducts containing 2 strands each, as three 4-strand ducts containing 4 strands each, Concept considers the correct number of strands (12), but only three of the six ducts. Elevation (Elevation Value at end 1 and Elevation Value at end 2) The vertical distance from the elevation reference to the centroid of the tendon’s strands, also referred to as CGS (center of gravity of strand).

Note: This version of RAM Concept measures the top and bottom cover to the CGS of the strands. Future versions will allow inputting of duct dimensions and allow a top and bottom cover to the outside of the duct to be input.

• Top Cover: The elevation is measured from the surface elevation to the CGS of the tendon. The value is always positive. • Bottom Cover: The elevation is measured from the soffit elevation to the CGS of the tendon. The value is always positive. The dimension from the elevation reference (at that exact plan location) to the CGS is the Elevation Value. Thus, if a profile point is located over a slab thickening (drop cap, beam etc.) then the thickening should be taken into account if the elevation reference refers to the changing surface. Concept does not currently use dimensions to underside of duct, or cover, to determine elevation values. Future versions will incorporate this calculation. The path of a tendon along with the number of strands determines the forces the tendon exerts on the concrete. Profile points (that are usually the tendon high and low points) define this path. If necessary, you can introduce intermediate profile points. Tendons are comprised of segments. For elevated floors, each segment has a high point (end 1) and a low point (end 2). For mats, the reverse is generally true. Each segment can represent a half of a span, or a partial half span. Most user defined spans have a tendon with two segments. Cantilevers and some user defined spans have tendons with one segment. Selections for Elevation Value and Elevation Reference should consider cover and load balancing. Profiles typically vary according to span lengths.

Note: Profile values displayed in RAM Concept are always from the soffit. When structure and/or tendon changes are made, the profile values can be temporarily out of date and incorrect. In order to update the profile values, use the “Generate Tendons” command or run a “Calc All”. Inflection Point Ratio Determines the distance, x, from end 1 in the span to the point where the tendon curvature changes sign. The inflection point ratio is the ratio of x to the distance from end 1 to end 2. A value of 0.2 places the

Note: The CGS is not the same as mid-depth of a bonded tendon’s duct.

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Chapter 26 inflection point 10% of the span distance from end 1 if end 2 is at midspan. This is a commonly used value.

26.4.2 Most tendon definition done on the tendon parameters layers

Note: An inflection point ratio of zero results in a simple

The Engineer specifies most prestressing on the tendon parameters layers but wants to supplement with isolated individually drawn tendons on the manual tendon layers. This might be faster to make minor adjustments than changing tendon parameter objects. The drawing production workflow might be to export tendon parameter and manual tendon plans on the plan(s), then modify those objects in CAD to product the final drawings.

parabola. Harped Specifies the tendon segment as having a straight profile (as opposed to a parabolic profile). Half Span Ratio (Half Span Ratio End 1 and Half Span Ratio End 2) Specifies the portion of the half span that this segment represents. The end 2 half span ratio must always be greater than the end 1 half span ratio. Half span ratios of 0 and 1 represent an entire half span. It is not recommended that these values be changed by the user. Position Profile Point 2 for equal balance loads If two entire half span tendon segments in a single span have different values for end 1 then the Position Profile Point 2 for equal balance loads option moves the low point in plan to equilibrate the uplift during an analysis calculation.

Note: Do not select this option if the half span ratios of both tendon segments are not 0 and 1 or if the profile values are at the same elevation. A segment with such profiles would have zero uplift and so the formulation does not work.

26.4.3 All work done on manual tendon layers The Engineer prefers working with individual tendons for both design and production of final tendon plans. The Engineer can draw the individual tendons on the manual tendon layers, or define objects on the tendon parameters layers to quickly generate a large number of tendons that can then be manipulated manually. Since the tendon objects on the generated tendon layers can not be edited, they will need to be copied and pasted from the generated tendon layers to the manual tendon layers. The objects on the tendon parameters layers would then be deleted to avoid duplication.

26.4 About creating tendons There are two ways to generate tendons: • Specification of objects on the tendon parameters layers, resulting in generated tendons on the generated tendon layers. • Drawing individual tendons directly on the manual tendon layers. These tendon generation schemes support a number of workflows related to tendon generation and design. The most common are outlined here:

26.5 Drawing banded tendon polylines Banded tendon polylines consist of two or more connected points that define a polyline. Once drawn the stretch tool can be used to modify the location of any of the points. To draw a banded tendon polyline:

1 Choose the Banded Tendon Polyline tool (

).

2 Click at the tendon polyline start point. 3 Click the next tendon polyline point (can be drawn across

multiple spans or partial spans).

26.4.1 All tendon definition done on the tendon parameters layers The Engineer specifies all prestressing on the tendon parameters layers, allowing RAM Concept to automatically generate individual tendons from the tendon parameters objects. When making changes to the tendon layout the Engineer will add, delete, or edit objects on the tendon parameters layer only. The Engineer might use the tendon parameter plans or the generated tendon plans for their tendon design plans.

RAM Concept

4 Continue to click tendon polyline points until all are

defined. 5 Right click and select enter to complete the operation.

Note: Banded tendon polylines can be connected at their end points to single or multiple other banded tendon polylines. However, it is an error to define banded tendon polylines that overlap.

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Chapter 26

26.6 Drawing distributed tendon quadrilaterals

Where banded tendon polylines end away from a profile polyline or intersect a slab edge, the tendon is profiled to the mid-depth of the slab at the end or slab edge intersection location.

Distributed tendon quadrilaterals define a specification to generate a specific force or number of strands per unit width at a given angle within a defined 4 sided polygon. To draw a distributed tendon quadrilateral:

1 Choose the Distributed Tendon Quadrilateral tool (

).

2 Click each of the four vertices of the quadrilateral vertex

sequentially (the quadrilateral can extend across multiple spans or bays). Since distributed tendon quadrilaterals are meant to represent a “smeared” tendon force, the spacing specified isn’t typically critical. However, due to geometrical irregularities inaccuracies can be introduced near the edges of the shape. RAM Concept automatically attempts to provide a half space at each edge of the tendon layout area to minimize this effect. This effect can also be minimized by specifying a smaller spacing, at the expense of a larger number of generated tendons and increased run time. A spacing of 2 ft (0.75 m) will normally provide a good balance between accuracy and computational expense.

Where distributed tendon quadrilaterals end between two profile polylines or the slab edge, the tendons are profiled as if they were extended to the next adjacent profile polyline or slab edge (representing a partial half span). This allows two distributed tendon quadrilaterals with different angles to be drawn adjacent to each other along a span and represent continuous span tendons. Where distributed tendon quadrilaterals intersect the slab edge and there is no profile polyline near the edge, the tendons are profiled to the mid-depth of the slab. Profile polylines can be created in a number of ways: • Drawing them manually. • Generating them for the entire floor in one span direction using the Generate Profile Polylines tool. • Generate span polylines from already defined support polylines using the Generate Span Polylines tool.

26.7.1 Drawing Profile Polylines

Note: Distributed tendon quadrilaterals with common spacing, PT System, inflection point ratio, and harped property can be drawn overlapping and RAM Concept will consider the cumulative force/strands in overlapping regions.

To draw a profile polyline:

1 Choose the Banded Tendon Polyline tool (

).

2 Click at the profile polyline start point. 3 Click the next profile polyline point. 4 Continue to click profile polyline points until all are

26.7 Defining profiles for banded tendon polylines and distributed tendon quadrilaterals Profiles are determined for banded tendon polylines and distributed tendon quadrilaterals by creating profile polylines. Tendon half spans are created wherever a generated tendon intersects a profile polyline. The generated half span tendons are oriented in the following direction (which will determine the inflection point location): • support polyline - span polyline • support polyline - slab edge • slab edge - span polyline Where generated tendons intersect identical profile polyline types (i.e, both supports), the tendon is oriented from the location of highest absolute elevation to the location of lowest absolute elevation. If the end elevations are the same then the orientation will be random (and not important).

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defined. 5 Right click and select enter to complete the operation.

26.7.2 Defining profile polylines using the Generate Profile Polylines tool This tool allows you to generate profile polylines automatically using span segments that have already been defined on the design strip layer. Support polylines are generated from existing span segments. Latitude tendon support polylines are generated from longitude span segments and vice-versa. Span polylines are created from the support polylines created in the first step of the operation. If no span segments are drawn on the corresponding layer then no profile polylines will be created. To generate profile polylines

1 Choose the Generate Profile Polylines tool (

).

2 Select the span set to generate profile polylines for.

Generally you will select the layer in the prestressing folder you are currently working in.

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Chapter 26 3 To generate support polylines from the span segments,

4 Set the span ratio for the generated span polylines. This

check the “generate support polylines” box and set the elevation reference and elevation desired for the generated support polylines.

is the desired span control point. For a profile control point at mid-span, set this value to 0.5.

4 If support polylines are generated, to generate span

polylines check the “generate span polylines” box and set the elevation reference and elevation desired for the generated span polylines. If the tendon span angle is consistent throughout the floor then set it in the Span Orientation Angle box. This will generate the span polylines in the specified direction between the generated support polylines. If there is more than one span orientation angle in the floor then “Use Medial Axis” can be selected. The Use Medial Axis option will generate span polylines that are equidistant from the generated support polylines. For a single spanning direction, the best results will normally be achieved by setting this angle.

Figure 26-4 Generate span polylines tool

26.8 Other tendon parameter plan objects and tools

26.8.1 Drawing tendon voids Tendon void polygons can be defined in areas where generated tendons are not desired. This might be used to create a stressing blockout in a banded tendon polyline or to prevent very short tendons from being created in an area covered by a distributed tendon quadrilateral. Tendon void polygons prevent creation of tendons inside their boundaries and apply only to the layer on which they are drawn. These objects do not affect the manual tendon layers. Figure 26-3 Generate profile polylines tool

To draw a tendon void:

1 Select the Tendon Void tool (

).

26.7.3 Defining span polylines using the Generate Span Polylines tool

2 Click at each polygon vertex consecutively.

This tool allows you to generate span polylines automatically using support polylines that have been previously generated.


To generate profile polylines

1 Select the support polylines that you want span polylines

generated between (

).

2 Choose the Generate Profile Polylines tool (

).

3 Set the elevation reference, elevation, and span orien-

tation angle for the generated span polylines.


26.8.2 Segment banded tendon polyline tool The segment banded tendon polyline tool is used to segment previously created banded tendon polylines where they cross the defined segmentation line. This can be useful, for example, where tendons need to be added in an end span of a previously defined banded tendon polyline. To segment banded tendon polylines:

1 Select the Segment Banded Tendon Polylines tool (

).

2 Click two points defining a line that will segment all

banded tendon polylines that cross it.

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Chapter 26

26.8.3 Generate program tendons tool The generate program tendons tool is used to create tendons on the generated tendon layers from the objects on the tendon parameters layer. It also updates the graphical representation of the objects on the tendon parameters layer such as the fillet data for the banded tendon polylines. These operations will also be performed during a “calc all”, if they are out of date. To generate program tendons

1 Click the generate program tendons tool (

).

2 A log will be displayed if any warnings or errors occurred

during the generation.

26.10 Tendon parameter drawing and text formatting Banded tendon polylines, distributed tendon quadrilaterals, and distributed tendon overlap areas have drawing controls and format specifiers intended to aid in the production of design quality drawings.

26.10.1 Banded tendon polyline formatting options Banded tendon polylines have a number of formatting properties to aid in the production of drawings: • Description - a user formatted string used to describe the banded tendon polyline properties.

26.9 Tendon parameter drawing examples Example 26-1 Drawing banded tendon polylines

The formatted description strings for the banded tendon polyline use the following key values: • $F - force • $f - force units • $N - number of strands • $P - PT system name • $I - inflection point ratio • $S - spacing • $s - spacing units • $T - number of tendons • \n - new line

Figure 26-5 Banded tendon polylines drawn by clicking on points A,B,C,D,E in sequence with Banded Tendon Polyline tool.

Example 26-2 Drawing distributed tendon quadrilaterals

• Draw Fillets - displays filleted connections between segments of banded tendon polylines using the Fillet Radius property set. The Fillet Radius property can be set to “Use Maximum” or a value smaller than the maximum can be typed into this box. • Profile Points - displays the profile control point information for the banded tendon polyline. The profile values are always referenced from the slab soffit to the CGS of the strands. • Symbol @ End 1,2 - displays the symbol at the end of the banded tendon polyline. Choices are: • None • Stressing End • Dead End

Figure 26-6 Three distributed tendon quadrilaterals drawn by clicking on points A-D with distributed tendon quadrilateral tool.

26.10.2 Distributed tendon quadrilateral formatting options Distributed tendon quadrilaterals have a number of formatting properties to aid in the production of drawings:

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Chapter 26 • Description - a user formatted string used to describe the distributed tendon quadrilateral properties. The formatted description strings for the banded tendon polyline use the following key values:

• Arrow

26.11 About drawing individual tendons

• $F - force/width • $f - force/width units • $N - number of strands • $n - number of strands/width units • $P - PT system name • $I - inflection point ratio • $S - spacing • $s - spacing units • $A - angle and units • \n - new line • Profile Points - displays the profile control point information for the banded tendon polyline. The profile values are always referenced from the slab soffit to the CGS of the strands. In addition to the profile points where the main tendon intersects profile polylines, the following additional points are provided to describe the distributed tendon profiles: • Edges - profiles at the edge of the distributed tendon quadrilaterals or slab edges. • Span Changes - profiles at drastic changes in span profiles. • Concrete Elevation Changes - profile changes where the concrete reference plane changes such as beams or drop caps. • Profile Polyline Ends - profiles at the ends of profile polylines The intent is that with all these points displayed the profiling of all tendons within the distributed tendon quadrilateral are defined by connecting support and span profile points. Profile points are not displayed at slab edges where no profile polylines are used. • Symbol @ End 1,2 - displays the symbol at the end of the distributed tendon quadrilateral main tendon. Choices are:

You can draw individual tendons on the manual tendon layers in a number of ways: • A single tendon one segment at a time using the Half Span Tendon tool (typically used for cantilevers). • A single tendon one span at a time using the Full Span Tendon tool. • A single tendon with numerous spans using the Tendon Polyline tool. • A number of tendons one segment at a time using the Half Span Tendon Panel tool. • A number of tendons one span at a time using the Full Span Tendon Panel tool. You use these tools in different situations. You might find drawing one tendon and then copying it is quicker than using the polyline and panel tools.

26.12 Drawing single tendons The following instructions are relevant for elevated floors where the tendon has a high point at supports and a low point near midspan. For mats, the reverse is generally true.

26.12.1 Drawing a half-span tendon You might use the half-span tendon tool for cantilevers and short end spans. For such uses, the Profile at End 2 value would commonly be half the slab thickness or the beam centroid dimension. To draw a half-span tendon:

1 Select the Half Span Tendon tool (

).

2 Click at the tendon high point. 3 Click at the tendon low point.

• None

Note: The order of mouse clicks is very important when

• Stressing End

drawing half-span tendons because the tool measures the inflection point from the high point (end 1).

• Dead End • Break • Symbol @ Extent Ends - displays the symbol at the end of the distributed tendon quadrilateral extent line. Choices are:

26.12.2 Drawing a full-span tendon You typically use the full-span tendon tool for conventional spans.

• None

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Chapter 26 To draw a full-span tendon:

1 Select the Full Span Tendon tool (

).

2 Click at the two tendon high points. The low point (End

2) automatically locates at the midpoint of the tendon.

Note: The low point can be adjusted with the Stretch tool ( ) or the “Position Profile Point 2 for equal balance loads” option in the Tendon Properties dialog box.

26.12.3 Drawing a multi-span tendon with the tendon polyline The Tendon Polyline tool ( ) allows you to draw a series of full span tendons with fewer mouse clicks. To draw a tendon polyline:

1 Select the Tendon Polyline tool (

).

2 Click a series of tendon high points. The low points (End

2) automatically locate at the midpoint of high points. 3 Right-click after clicking the last high point. 4 Click Enter Figure 26-1 Tendons with parallel layout and spacing not to exceed five feet.

26.13 Drawing multiple tendons You can draw a group of tendons in one operation with the tendon panel tools. You designate the panel to lay out the tendons, along with the desired tendon spacing, and RAM Concept draws the tendons. The drawing process requires you to draw the panel points sequentially in a clockwise or counter-clockwise manner to form a quadrilateral.

26.13.1 Tendon panel layout options Layout The choices are Parallel and Splayed.

Figure 26-2 Tendons with splayed layout and spacing not to exceed five feet.

Tendon Spacing The choices are Fixed, Equal and Auto Connect. 142

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Chapter 26 “Fixed” draws tendons at exactly the specified spacing distance apart. It is not available with splayed tendons. “Equal (not to exceed maximum)” draws tendons an equal distance apart that is at most the spacing value. “Auto connect (based on last edge)” draws tendons connected to the profile points on the last edge of the tendon panel area. Skip Start Tendon / Skip End Tendon Omits edge tendons.

Figure 26-4 Tendons after Auto Connect. To draw a Half-Span Tendon Panel:

1 Select the Half Span Tendon Panel tool (

).

2 Click at the tendon high and low points of the first tendon

in the tendon panel area. 3 Click at the tendon low and high points of the opposite

edge of the tendon panel area. The Tendon Panel dialog box appears after the fourth click. Figure 26-3 Tendons after Auto Connect.

4 Select options (see discussion above). To draw a Full-Span Tendon Panel:

1 Select the Full Span Tendon Panel tool (

).

2 Click at the tendon high points of the first tendon in the

tendon panel area. 3 Click at the tendon high points of the opposite edge of the

tendon panel area (following a clockwise or counterclockwise direction). The Tendon Panel dialog box appears after the fourth click. 4 Select options (see discussion above).

Note: A low point (End 2) automatically locates at the midpoint of each tendon.

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Chapter 26

26.14 Editing tendons

4 Enter the new profile value. 5 Uncheck either tendon layer that you do not want edited.

As with any object, you can edit tendons on the manual tendon layers after they are drawn.

6 Uncheck either end number that you do not want edited,

and click OK.

26.14.1 Calc profile tool You can adjust profiles manually or use the Calc Profile tool (

) for automatic adjustment.

Too much uplift in a tendon can cause deflection reversals that may crack the slab. For this and other reasons, it is a good idea to have the amount of uplift or load balance somewhat consistent from span to span. To edit a tendon based on uplift:

1 Select a tendon segment. 2 Click the Calc Profile tool (

).The Calc Tendon Profile dialog box appears and reports the current balance load. 3 Input the desired balance load (values are typically

negative) in the Calc Tendon Profile dialog box and click Calc. The low point (end 2) adjusts to provide the desired uplift. You can select two segments in the same span and Concept calculates the low point based on average uplift. It is generally not necessary to balance exactly the same amount of load in each span. It is not advisable to have an excessive number of different low points. Manually rounding the profile values can produce a more practical design. If the desired balance load is too high then Concept could calculate a negative profile that causes an error when calculating the results.

Note: Concept does not check cover violations 26.14.2 Change profiles tool

Figure 26-5 Change tendon profiles tool

26.15 About jacks Jacks can be specified for tendons on manual tendon layers. RAM Concept calculates the force losses in a tendon if you draw jacks at live (stressing) ends. If you draw a jack at each end of a tendon then it is double end stressed. If only one jack is drawn then the other end of the tendon is a dead end. If you draw a single jack on a tendon layer then every tendon on that layer must have at least one jack attached. Concept uses the relevant value of fse (specified in the Materials criteria page) as the effective stress for any tendon without a jack.

When a plan viewing one of the tendon layers is active, Concept adds a Change Profiles items to the Tools menu. This menu item allows you to change all tendon profiles with a given value to a new value. This can be very useful in circumstances such as change slab or beam depths. To change the profile of a number of tendons:

1 Open a plan from the Latitude Tendon or Longitude

Tendon layer. 2 Choose > Tools > Change Profiles.

The Change Tendon Profiles dialog box appears. 3 Enter the profile value that you wish to change.

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26.16 Jack properties Set the default jack properties in the Default Jack Properties dialog box by double clicking the Jack tool ( ). You can choose to ignore the jack property values in the Jack Properties dialog and instead use the PT System values. The following is a list of jack properties: Jacking Stress The stress in the strand at the jack at jacking.

RAM Concept

Chapter 26 Anchor Friction Coefficient Loss of stress due to friction in the anchorage. It is a fraction with no units. You would enter a 2% loss as 0.02. Most PT suppliers recommend a value of zero for unbonded tendons. You might consult with a local PT supplier regarding bonded tendons. Wobble Friction Coefficient Friction calculations use this property (k) to estimate losses due to accidental curvature (in the horizontal and vertical planes). It is the product of the angle friction coefficient and the accidental angular change per unit length.

Seating Distance The distance that the wedges recede into the anchorage. This occurs when the field operator releases the tension in the jack. Long Term Losses The sum of losses such as creep and shrinkage of concrete, and relaxation of strand. It also includes the loss due to elastic shortening of the concrete even though it is a short-term loss.

26.17 Drawing the jacks

Note: Some engineering communities (Australia in particular) use a definition of wobble coefficient that is the accidental angular change per unit length. These communities can calculate the wobble coefficient that Concept uses, k, with the following relationship: k = AngularWobbleCoefficient * mu.

You draw jacks with the Jack tool ( ) by clicking a rectangle around the stressed ends of the tendons.

Angle Friction Coefficient Loss due to deliberate curvature (in the horizontal and vertical planes). Most designers know it as mu.

2 Click at opposite corners of a rectangle encompassing the

To draw tendon jack(s):

1 Select the Jack tool (

).

tendon live ends.

Note: You can delete a single jack by double clicking it. To delete multiple jacks, consider making all objects except the jacks invisible, then select and delete the jacks.

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Chapter 27

27 Using Live Load Reduction RAM Concept can automatically perform live load reduction calculations on columns, punching checks, design strip segments and design sections per the requirements of the selected live load reduction code.

27.3 Setting the Live Load Reduction Code You choose the live load reduction code in the Calc Options. The default live load reduction code is “None”, causing no reductions to be used.

27.1 About Live Load Reduction To set the live load reduction code:

Most design codes allow the design of members supporting large areas to ignore a fraction of the live load effects on the member. This “live load reduction” is allowed because the probability of all of a large supported area being simultaneously fully loaded is small. While each code has its own rules, the common approach is that the larger the supported area, the larger the allowed reduction, up to a limit.

1 Choose Criteria > Calc Options 2 Choose the General tab 3 Choose the live load reduction code, as shown in Figure

27-1.

27.2 Live Load Reduction Options RAM Concept currently allows several different live load reduction calculation options: ASCE 7-02 Reduction using ASCE 7-02, section 4.8. ASCE 7-10 Reduction using ASCE 7-10, section 4.7. IBC 2003 Reduction using IBC 2003, section 1607.9.

Figure 27-1 Calc Options Dialog

IBC 2006 Reduction using IBC 2006, section 1607.9. IBC 2009 Reduction using IBC 2009, section 1607.9. UBC 1997 Reduction per UBC 1997, section 1607.5.

27.4 Live Loading Types

AS/NZS 1170.1-2002 Reduction per AS/NZS 1170.1, section 3.4.2.

RAM Concept allows several different live loading types. These types are affected by live load reduction in different ways, depending upon the design code. The types are:

BS 6399-1:1996 Reduction per BS 6399, sections 6.1 through 6.3.

Live (Reducible) Loading Standard live load reduction is performed

IS 875 (Part 2) - 1987 Live Load Reduction Reduction per IS 875 (Part 2) section 3.2

Live (Unreducible) Loading No live load reduction is performed

Eurocode 1-2002 (UK Annex) Reduction per clause 6.3.1.2 and UK Annex 2.5-2.6

Live (Storage) Loading Special “storage” live load reduction is performed if allowed in the specified code.

National Building Code of Canada 2005 Reduction per clause 4.1.5.9

Live (Parking) Loading Special “parking” live load reduction is performed if allowed in the specified code.

None No live load reduction is performed.

Live (Roof) Loading No live load reduction is performed.

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Chapter 27 These loading types are specified in the Loadings window. See section 10.2 though section 10.6 of Chapter 10, “Specifying Loadings” for more information.

To specify overriding values for number of levels supported, tributary area, and influence area:

Note: Live (Roof) Loading is reducible in the RAM Struc-

2 Select the object(s)

tural System, but not in RAM Concept.

3 Choose Edit > Selection properties

1 Open the appropriate plan

4 In the Default Properties dialog box (see Figure 27-2):

• Click the Live Load Reduction tab

27.5 Live Load Reduction Parameters RAM Concept uses up to six parameters to determine the allowed reduction factors:

• Check the Use Specified LLR Parameters box • Set the values for LLR Levels, Trib Area, and Influence Area. 5 Click OK.

Loading type - Only certain loading types may be reduced (as is discussed above) Member type - Most codes have special reduction rules for certain member types (such as columns) Maximum allowed reduction - The user may specify a maximum reduction value for each member. Number of levels supported - Most codes consider the number of levels supported when calculating the allowed reductions. If RAM Concept's automatic calculation of areas is used, then the number of levels supported is assumed to be one. Tributary area - Most codes use the tributary area of the member as the primary live load reduction parameter. Influence area - RAM Concept has options for two codes that use the influence area of the member as the primary live load reduction parameter. RAM Concept calculates the last three parametric values. You can view the values on plan as described in “To view the column element LLR results” and “To view the latitude design strip LLR results” on page 157.

Figure 27-2 Live Load Reduction Properties

You can override the calculation by specifying the parameters’ values. The next section describes how to edit these values.

27.7 Implementation of Live Load Reduction

27.6 Specifying Live Load Reduction Parameters

See Chapter 52, “Live Load Reduction Notes” for information on RAM Concept’s implementation of live load reduction.

You can specify live load reduction values for columns, punching checks, design strip segments and design sections.

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28 Calculating Results You generally calculate results many times during the modeling and design process. You can calculate as soon as elements have been generated (e.g. self-weight deflection) or wait until modeling is close to finished. It is conceivable that you would not calculate results until all tendons, loads and design strips are drawn. It makes sense, however, to “run” the file during modeling to check for errors. That way you could avoid repeating the same modeling error.

28.1 Calculating the results You can calculate all or some of the results with or without a review of the calculation options.

28.1.1 Calculating all of the results To calculate results:

1 Click Calc All (

), or choose Process > Calc All.

Modeling errors are common and you may encounter error messages when calculating results. If the file runs successfully without errors, the Calc All icon becomes grayed-out. If errors occur then the calculator does not become grayed-out. See “About analysis errors” on page 153 for more information.

28.1.2 Partially calculating the results To partially calculate results:

1 Click Calc Partial (

The slider on the left side of the Calc dialog box determines the level to which Concept performs the calculations. The options are: Through analysis Calculations are performed up to and including the global slab analysis (slab moments deflections, etc.) and the strip and section forces. Through design Concept performs the design of strips, sections and punching shear checks, in addition to all the Through analysis calculations. Through layout Concept performs the layout of program reinforcement on the Reinforcement layer, in addition to all the Through design calculations. All Concept performs the detailing of program reinforcement into individual bars (viewable in perspectives), in addition to all the Through layout calculations. The checkboxes on the right side of the Calc dialog window provide options on how Concept performs the calculations. The options are: Skip warnings Optional warnings do not stop the calculations, but are added as notes to the Calc Log. This setting is off by default. Calculate only out-of-date items Existing calculation results are not replaced by new calculations unless Concept detects that the existing calculations are out-of-date. This setting is on by default. Warnings invalidate calculations Previous calculation warnings are considered to invalidate their associated results, causing the re-calculation of the item that caused the warning. This setting is on by default.

), or choose Process > Calc Partial.

The dialog box shown in Figure 28-1.

28.1.3 Calculation options You can review and change the calculation options. To access the Calc Options:

1 Choose Criteria > Calc Options. 2 Choose the General tab.

Figure 28-1 Calc dialog box

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Chapter 28 transverse shear (and SSR design for punching shear) design for the given longitudinal reinforcement. When a “calc all” is run using this option, any program reinforcement will be deleted before the start of the analysis and no additional program reinforcement will be designed.

28.1.5 Code options Design The applicable design code. You can switch design codes during the design process. Note that switching codes does not automatically change the load factors. See “Rebuilding load combinations” on page 39 for information on changing code specific load factors. Live load reduction The applicable loading code. Figure 28-2 Calc options dialog, General tab

The following describes the calculation options:

28.1.4 General options Auto-stabilize structure in X- and Y-directions Auto-stabilization introduces a small horizontal brace for structures that have no horizontal restraint. This is only suitable for structures with no external horizontal loads. Create viewable self-dead loading This setting controls whether RAM Concept creates loads that are viewable in plans and perspectives for the self-dead loading. This setting has no effect on the actual loading calculations. You would normally leave this unchecked.

See Chapter 27, “Using Live Load Reduction”, for information on the loading code.

28.1.6 Zero tension iteration options If a mat is flexible or there are large overturning loads then the springs may initially be resisting tension. You can reduce this tension by iteration. Zero tension iterations use an “accelerator” factor to make convergence faster. An accelerator value of 1 results in no acceleration, while a value that is too large may result in wild oscillations instead of convergence. RAM Concept calculates the accelerator value as follows: accelerator = (Tj / Ti)power ≤ maxAccelerator

Include supports above slab in self-dead loading This includes the weight of supports (columns and walls) as loads. You should consider that Concept bases punching shear calculations at columns below on the total column reaction that includes any loads applied directly above.

where

Include tendon component in punch check reaction This includes the vertical component of the tendon force within the punch zone (which often reduces the punch check reaction). See “Contribution from the Vertical Component of Prestress” on page 648 of Chapter 66, “Punching Shear Design Notes” for more information.

power = the user-controlled “Accelerator Power” (typically 1.0)

Check capacity of long. user reinf. without designing additional program reinf. This option instructs RAM Concept to perform a check of the existing defined longitudinal user reinforcement and posttensioning and report any failed locations. Since RAM Concept does not currently have user defined transverse (shear) reinforcement, Concept always performs a

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Tj = the tension force offset in iteration j (j = i+1) Ti = the tension force offset in iteration i

maxAccelerator = the user-controlled maximum allowed acceleration (typically 1.5) Iterations to use The number of iterations used in calculations. The higher the number of iterations, the closer the tension is to zero. Accelerator Power The power in the above formula; typically this is 1. Max. Acceleration The maximum allowed acceleration.

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Chapter 28

28.1.7 Reinforcement layout and detailing parameters

28.1.8 Load History / Effective curvature ratio options

There are five parameters that influence how Concept lays out and details reinforcement.

Load history and effective curvature ratio options are accessible on the Load History / ECR tab.

Three of the parameters are layout “cost” values that affect Concept's priorities when laying out program reinforcement. They have no effect on user reinforcement. The cost parameters are: Bar Length Cost When this value is increased Concept gives a higher priority to minimizing the weight of the reinforcement. This also causes Concept to create a larger number of callouts. Bar Group Length Cost When this value is increased Concept gives a higher priority to minimizing the total length of all of the callouts summed together. This also causes Concept to use more reinforcement than necessary in some areas. Bar Callout Cost When this value is increased Concept gives a higher priority to minimizing the total number of callouts. This also causes Concept to use more reinforcement than necessary in some areas, and may cause Concept to provide reinforcement where none is required. Using the default values for these three cost parameters usually results in acceptable program reinforcement layouts. However, you may want to try adjusting these parameters if you want Concept to arrive at different layouts. The other two parameters are as follows: Bar Rounding Length Concept lays out the program reinforcement with lengths that are a multiple of this value. The only instance where the program reinforcement does not use this rounding length is where both ends of a reinforcement callout are not straight (they are hooked or anchored). Bar End Cover Concept uses this value when detailing both user and program reinforcement. Bar ends - except for bar ends with anchors - are always pulled back from slab edges by this amount.

Figure 28-3 Calc options dialog, Load History / ECR tab

RAM Concept calculates an effective curvature ratio (ECR) at every cross section: ECR = Ce / Cg Where Ce = the effective cross section curvature Cg = the gross section curvature RAM Concept calculates Ce by the approximate formula: Ce = (kc BSR Cg) + ((1 – BSR) Cccs) where kc = the concrete design creep factor (often 3.35) = total strain / elastic strain

Note: ACI 209 reports the value of 3.35 as an average creep value. RAM Concept files adopt this value as a default. BSR = Branson’s Stress Ratio Cccs = the cross section curvature considering cracking, creep and shrinkage. See Chapter 51, “Section Design Notes” for further explanation. Creep factor kc as defined above. See Chapter 65, “Load History Deflections” for additional information.

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Chapter 28 Shrinkage strain The design shrinkage value used to determine long-term curvature in cross sections. See Chapter 65, “Load History Deflections” for additional information.

28.1.10 Vibration options Vibration and footfall analysis options are accessible on the vibrations tab.

28.1.9 Load History These are parameters that apply to RAM Concept's load history calculations. Initial Load Application The time of application of the initial loads. This becomes the start time of the first load history step specified in the Load History Criteria page. Moist Cure Duration The duration of the moist cure period. This is used in the calculation of shrinkage strains. Convergence Tolerance The maximum specified difference in calculated deflection between iterations in order to consider RAM Concept to have converged upon the solution. Ageing Coefficient The coefficient that accounts for various behaviors in the calculation of sustained loads. See Chapter 65, “Load History Deflections” for additional information. Shrinkage Restraint % A percentage of the free shrinkage strain to consider as externally restrained. The shrinkage restraint is used to calculate a hypothetical tension strain which is included in the tension stiffening calculations. A normal range for this value will be 0 to 20%. See Chapter 65, “Load History Deflections” for additional information. Iterations to Use The maximum number of iterations to use to calculate instantaneous or sustained portion of a unique load history step. Accelerator Power A value that determines how much weight to give newly calculated curvatures in an iteration compared to the average curvatures from the previous iteration. A value of 1.0 indicates to give the newly calculated curvature equal weight as the previous average curvature. A value of greater than 1.0 will give the newly calculated curvature more weight than the previous average curvature.

Figure 28-4 Calc options dialog, Vibrations tab

These are parameters that apply to RAM Concept's vibration calculations. Number of modes The number of modes for RAM Concept to calculate in the Eigenvalue analysis. Dynamic concrete modulus factor The ratio of concrete modulus of elasticity to use in the dynamic analysis over the concrete modulus of elasticity defined for the static analysis. Stiffness matrix Controls the stiffness matrix that is used to solve the Eigenvalue analysis. The global linear elastic analysis model can be used, or any load history step can be selected. Minimum footstep frequency The minimum footstep frequency to consider in the footfall analysis. Normal footstep rates range from 1.5 to 2.5 Hz. Maximum footstep frequency The maximum footstep frequency to consider in the footfall analysis. Normal footstep rates range from 1.5 to 2.5 Hz. Damping Ratio The damping ratio to use in the vibration analysis, as a fraction of critical damping (damping ratio = 1). Normal range for concrete buildings is 0.01 to 0.04. Simplifed (fast) calculation This analysis uses a fast calculation technique that is generally suitable for day to day design where RMS velocity values are not required. Modal Analysis This analysis uses a comprehensive dynamic modal superposition analysis which is suitable for structures that are vibrationally sensitive or if RMS velocity values are required.

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Chapter 28 Simplifed (fast) calculation This analysis uses a fast calculation technique that is generally suitable for day to day design where RMS velocity values are not required. Duration, Time Increment Defines the number of time points that are used to calculate the modal analysis. The duration should generally be set to capture at least 30 cycles of forcing and the time increment should be set to at least 10 times shorter than the 4th harmonic of the fastest walking frequency. Weight of Person The static weight of the person walking. Simplifed (fast) calculation This analysis uses a fast calculation technique that is generally suitable for day to day design where RMS velocity values are not required. Max natural frequency Defines the maximum natural frequency that is used in the dynamic analysis for the resonant response. All nodes Will consider excitation at every node. Critical Nodes Will consider excitation only at nodes where the expected response factor is greater than or equal to the Excitation Response Factor Threshold. Excitation Response Factor Threshold When considering Critical Nodes, the threshold value of interest. All DOF at all nodes Will calculate a response at every DOF at every node for the Modal Analysis (not recommended). Vertical DOF at all nodes Will calculate a response at every node, but only for vertical DOF. Vertical DOF at all nodes Will calculate a response only at the excited nodes.

• fix the problem and continue calculation • stop the analysis

28.3 Recalculating Some or all of the calculation analysis information becomes out-dated when you edit the model. Click Calc All (

) to run a new analysis calculation. If the Calc All

option is grayed-out (

), the analysis results are current.

When you recalculate, the analysis starts from the point where the information is no longer valid. For example, if you were to add a load, it would not affect the stiffness matrix. The recalculation would start with the analysis of loads and then move on to design. If you were to edit the concrete elements however, the calculation would start from the beginning.

28.4 Calculating load history deflections To calculate results:

1 Click Calc Load History Deflections(

), or choose

Process > Calc Load History Deflections. If any calculations are out of date at the time, a “Calc All” will effectively be performed prior to calculating the Load History Deflections.

28.5 Calculating vibration analysis To calculate results:

28.2 About analysis errors

1 Click Calc Vibration Analysis(


Calc Vibration Analysis. Two types of errors can occur during calculation: fatal and non-fatal. RAM Concept generates an Analysis Error message if an error occurs. If a fatal error occurs, analysis cannot continue. You must correct the problem, then recalculate. For example, if the structure is unstable then Concept cannot triangularize the stiffness matrix. After non-fatal error occurs, you can choose whether to continue the analysis calculation or not. For example, if a point load is not located on the structure, you can do one of the following: • continue the analysis and ignore the point load

RAM Concept

Note: If a load history stiffness matrix is selected, the load history analysis must be run after specifying the load history step to use and prior to running the vibration analysis.

28.6 Reviewing the calc log After RAM Concept calculates results, you can review the calc log to check for detected errors. To open the Calc Log:

1 Choose Report > Calc Log.

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Chapter 28 To open the Load History Calc Log:

1 Choose Report > Load History Calc Log. To open the Vibration Calc Log:

1 Choose Report > Vibration Calc Log.

28.7 Decreasing calculation time The time it takes RAM Concept to calculate results is dependent upon a number of parameters. You have control over some of these parameters. Desired Element Size

The time to analyze the stiffness matrix is a function of the number of finite element nodes. You can speed up the analysis time by using larger finite elements for preliminary work. This means specifying a large Desired Element Size when generating the mesh.

calculation time by eliminating load patterns and setting alternate envelope factors to the same as load factors in the Load Combinations window (Choose Criteria > Load Combo to open the Load Combinations window). SSR Design

Stud shear reinforcement design adds significantly to the calculation time. You might consider delaying the drawing of punching checks until most of the design is close to finish. Detailed Section Analysis

A cracked section analysis takes significant time. If you are not interested in these results or they are not appropriate then you can turn the detailed section analysis off. To turn off Detailed Section Analysis:

1 Choose Criteria > Design Rules. 2 Uncheck the Include detailed section analysis boxes. Load History Deflections

Design Strip “Min Number of Divisions” and “Max Division Spacing”

The calculation time is a function of the number of span segment strip cross sections and design sections on the slab. Each span segment strip with “n” internal divisions produces at least “n+1” design cross sections; more if the maximum spacing governs. You can speed up the analysis time by using a small number of divisions and large maximum spacing for preliminary design.

Load history deflection calculation time is affected significantly by the number of cross sections and the convergence tolerance/iterations to use. Calculation time can be reduced by reducing the number of cross sections or increasing the convergence tolerance and/or reducing the iterations to use.

Enveloping

Load patterns and alternate envelope factors produce additional calculations. The Concept algorithms for enveloping are quite efficient and so do not slow down the calculations very much. You could, however, speed up the

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Chapter 29

29 Viewing the Results RAM Concept produces a large volume of results from the model analysis.

This section explains how to find such results.

If you take the time to understand how Concept calculates results (and their accessibility), Concept can be a much more powerful tool in your workplace.

the file has RAM Concept’s default new file setup. The default new file setup provides preconfigured plans to show some of the results in an organized way. You can change these plans by editing the visible objects and plots. Keep in mind that this may void or make irrelevant some of the instructions below.

Note: When you create a new file without using a template,

29.1 Type of results You can view the results generated via text tables, plans, and perspectives on layers of the following types: • Loading • Load Combination • Rule Set Design • Load History Deflections

29.2.1 Viewing reinforcement results RAM Concept stores the envelope of all required reinforcement for all rule set designs in the Design Status folder. There are a number of plans available to show different reinforcement. The names of reinforcement plans in the default new file setup match the visible reinforcement.

• Vibrations

To view reinforcement

• Design Status

1 Choose Layers > Design Status > Reinforcement Plan.

To locate a particular result, you need to know on which layer it belongs. Only that layer contains the plans, perspectives and text tables that show those results. For example, you find the Live Loading: Deflection Plan on the Live Loading layer, but the service deflection is in the Service LC layer.

If this plan shows more information than you require, consider using an alternate plan such as the Longitude Bottom Reinforcement Plan. To view longitudinal direction bottom reinforcement

1 Choose Layers > Design Status > Longitude Bottom

Reinforcement Plan. To view a reinforcement plot

29.2 Viewing frequently used results

1 Choose a reinforcement plan. 2 Choose View > Plot (

In general, using plans is the most useful way to view results. Most results of interest relate to the following: • reinforcement quantities • status • deflections

).

The Plot dialog box appears with the Section Design dialog. 3 Check the Active box. 4 Select a reinforcement radio button. 5 Enter the Min Frame # and Max Frame #, and click OK.

• support reactions • precompression

29.2.2 Viewing status

• load balance • bending moment contours • section stresses (for some codes) • punching shear

It is possible for a concrete member not to comply with code irrespective of the reinforcement provided. For example, there is a limit on how much shear a member can resist. RAM Concept reports a violation when the shear exceeds the limit.

• bearing pressures Status refers to code violations. When a design strip complies with all code rules in a rule set design then its status is “OK”. If there are violations then the status is “Failed” or “Exceeded” (depending on the rule) and RAM Concept identifies the code rule. RAM Concept

155

Chapter 29 Concept stores the envelope of status for all rule set designs in the design status layer folder.

29.2.4 Viewing support reactions

To view the status

Support reaction plans are available by default for most loadings and some load combinations.

1 Choose Layers > Design Status > Status Plan.

Filtering can make trivial reactions invisible.

Note: There is no consideration of deflection limits in the status report.

To view self-weight reactions:

1 Choose Layers > Loadings > Self-Dead Loading >

Reactions Plan.

29.2.3 Viewing deflections

To view live load reactions:

You may be interested in a number of different deflection plans. Usually these are for vertical deflection but RAM Concept does calculate lateral deflections and hence these are viewable.

1 Choose Layers > Loadings > Live Loading > Std

All deflection intensity and contour plots use uncracked section (Igross) results and do not consider cracking (unless the load factors have been increased for this purpose).

1 Choose Layers > Load Combinations > All Dead LC >

Note: Intensity and contour plots are accessed via the plot

1 Choose Layers > Load Combinations > Factored LC >

“Slab” tab.

Std Reactions Plan.

Deflection results that do consider cracking are available via plots that use the Section Analysis tab and L.T. Deflection plot.

Note: You could change these plans with the plot setting

Reactions Plan. To view dead load reactions:

Std Reactions Plan. To view factored load reactions:

29.2.5 Viewing post-tensioning precompression (P/A)

such that the plot is no longer consistent with the plan name. As such, changing the plot is discouraged.

Precompression plans can be useful for viewing the level of tendon prestress and the effect of restraining supports. The default plans are for the x and y directions.

See Chapter 65, “Load History Deflections” for more information.

To view the precompression in the x-direction

Note: “Slab” (identified by the plot tab) deflection plots are available for loadings and load combinations. “Section Analysis” (identified by the plot tab) deflection plots are available for rule sets. To view service deflection

1 Choose Layers > Load Combinations > Service LC >

1 Choose Layers > Loadings > Balance Loading > Fx

Precompression Plan.

29.2.6 Viewing balanced load percentages You can view the percentage of load that is balanced by the post-tensioning within design strips.

Max Deflection Plan. To view the strip-based long term deflection for ACI318 or BS8110

To view the balanced load percentages on the latitude design strips plan

1 Choose Layers > Design Strips > Latitude Design Strips

1 Choose Layers > Rule Set Designs > Service Design >

Plan

L.T. Deflection Plan.

2 Choose View > Visible Objects (

To view the strip-based long term deflection for AS3600

1 Choose Layers > Rule Set Designs > Max Service Design

> L.T. Deflection Plan.

).

3 Check the Balanced Load Percentages box, and click

OK.

Note: See “Calculating the balanced load percentages” on page 389 for more information.

To view the strip-based long term deflection for EC2

1 Choose Layers > Rule Set Designs > Quasi-Permanent

Service Design > L.T. Deflection Plan.

29.2.7 Viewing bending moment contours Bending moment contour plans can be useful for understanding the flexural behavior of complicated floors.

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Chapter 29 The Bending Moment Distribution tool ( usefulness of the plan.

) increases the

To view the factored moments about the x-axis

1 Choose Layers > Load Combinations > Factored LC >

Mx Plan.

29.2.8 Viewing section stresses Some codes have concrete stress limits for post-tensioned floors. You may want to know these stresses for the Initial Service Design and Service Design. Usually you want to view stresses based upon the design strips rather than contours, as the design process rarely uses peak stresses derived from contours. To view the strip-based initial top stresses

1 Choose Layers > Rule Set Designs > Initial Service

Design > Top Stress Plan.

To view the punching shear SSR

1 Choose Layers > Design Status > SSR Plan.

29.2.10 Viewing live load reduction results You can view live load reduction results for each “member” (columns, punching checks, design strip segments and design sections) and some loadings. To view the column element LLR results

1 Choose Layers > Element > Slab Summary Plan. 2 Choose View > Visible Objects (

).

3 Check the LLR Parameters box, and click OK. To view the latitude design strip LLR results

1 Choose Layers > Design Strip > Latitude Design Strip

Plan. 2 Choose View > Visible Objects (

).

3 Check the LLR Parameters box, and click OK. To view the strip-based initial bottom stresses

1 Choose Layers > Rule Set Designs > Initial Service

Design > Bottom Stress Plan.

29.2.11 Viewing soil bearing pressures

To view the strip-based service top stresses

Files created with “Mat foundation” checked in the New File dialog box have bearing pressure plans provided.


Top Stress Plan. To view the strip-based service bottom stresses


To view live loading soil bearing pressure

1 Choose Layers > Loadings > Live Loading > Max Soil

Bearing Pressure Plan.

Bottom Stress Plan.

To view service soil bearing pressure

Note: If too much information is visible then edit the plot.


You could make the capacities invisible, or limit the range of strip numbers

Max Soil Bearing Pressure Plan.

Note: You can add soil bearing pressure plans to files. See “Creating new result plans” on page 158.

29.2.9 Viewing punching shear results RAM Concept checks punching (or two-way) shear for the appropriate code. It calculates the stresses at each vertex of a potential failure plane and compares the calculated stresses to allowable values. To view the punching shear status

29.3 Viewing other results There are times when the result you seek is not visible on the default plans. The following describes how to show such results.

1 Choose Layers > Design Status > Punching Shear Status

Plan.

Note: “USR” is unreinforced stress ratio Note: “RSR” is reinforced stress ratio Note: “CTSR” is closed ties stress ratio. This is only available for AS3600. See “The AS 3600 Punching Shear Model” on page 656 of Chapter 66, “Punching Shear Design Notes”.

29.3.1 Changing which result objects are visible In the default new file setup, specific objects are visible by default. You can modify the visible objects to show less or more results. To change the visible objects:


RAM Concept

). 157

Chapter 29 2 Choose options in the Visible Objects dialog box and

click OK

• Enter a name such as “Strength BMD”.

Note: See “Controlling views” on page 11 for more infor-

• RAM Concept automatically appends the word “plan” to the name and prepends the layer name.

mation.

• Select the Strength Design layer, and click OK. • The Visible Objects dialog box appears.

29.3.2 Changing which results plot

• Click Show Nothing, and click OK.

The plot settings control which results plot on a plan or a perspective. The default file setup has specific plot settings for particular plans or perspectives. You may decide to change the settings to suit your requirements, or to make the plan easier to read.

• Choose View > Plot (

• The Plot dialog box appears. • Select the Section Analysis tab. • Check Active. Keep the Value as Bending Moment

To change a plot setting:

1 Choose View > Plot (

).

).

• Uncheck Maximum Capacity and Minimum Capacity. • Click OK.

The Plot dialog box appears. 2 Make changes and click OK.

Note: You can select specific frame numbers in the dialog

Note: The way plans and perspectives are named is often

box. This could be used to show a plot for, say, a single beam.

a reflection of the plot settings used. If you change the plot settings, you might make the names inaccurate.

Note: You can selectively turn off left, middle and right

Note: You must first open the plan or perspective before

strips. Left and right are the “half” middle strips. Center is the column strip.

you can use the plot command. Example 29-1 Plotting the strip bending moment on an existing plan The following example demonstrates plotting the bending moment envelope on the Strength Design: Reinforcement Plan:

Example 29-3 Creating a new reactions plan The following example demonstrates creating a Service LC reactions plan: • Choose Layers > New Plan. • Enter a name such as “Reactions”.

• Choose Layers > Rule Set Designs > Strength Design > Reinforcement Plan.

• RAM Concept automatically appends the word “plan” to the name and prepends the layer name.


• Select the Service LC layer, and click OK.

).

• On the Strip tab, check “Active”.

• The Visible Objects dialog box appears.

• Select “Bending”

• Click OK.

• Check “Maximum Moment”, and “Minimum Moment”.


• Click OK.

• The Plot dialog box appears.

).

• Select the Reaction tab.

29.3.3 Creating new result plans

• Check Active.

You can create new plans for results that are not available in the plans in the default new file setup. See “Creating new plans” on page 11 and “Creating new perspectives” on page 11 for more information on how to create new plans and perspectives.

• Select Standard.

Example 29-2 Creating a new bending moment plan The following example demonstrates creating a bending moment plot plan for the Strength Rule Set. • Choose Layers > New Plan.

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• Check the supports (under Value) for which you want to view reactions.

29.4 Section distribution plots RAM Concept’s section distribution plots allow you to see the variation of analysis values across any line drawn on the structure. These distribution plots can be very helpful in RAM Concept

Chapter 29 understanding the behavior of the structure (especially for moments and deflections), but they are not intended to be used for quantitative design purposes.

Bending Moment Distribution tool ( ), the contour plot and the distribution plot would display the same values.

29.4.1 Distribution plot values Distribution plots are created using the Bending Moment Distribution tool ( (

), Vertical Shear Distribution tool

), Axial Force Distribution tool (

) and Selected

Plot Distribution tool ( ). These plots display predictions of values along the lines drawn across the slab. RAM Concept bases these predictions on the calculated results of the individual elements. RAM Concept’s calculation method guarantees that the results for design strip segments and design sections are in equilibrium with the nodal loads. The results for plots across elements are not necessarily exact, however, and can be much less accurate for coarse meshes or elements with high aspect ratios. Even though RAM Concept’s calculation method guarantees stored elastic energy of the stresses in each element is equal to the energy of the loads applied to the element, for some oddly shaped elements (such as pointy triangles), the energy formulation can result in local fictitious stress spikes. Note that this limitation does not affect design strip segments or design sections and does not affect RAM Concept’s reinforcement calculations.

29.4.2 Moment distribution plots You can create moment distribution plots using the Bending Moment Distribution tool ( ). The plot displayed along the drawn line shows the distribution of bending moment about the axis of the line. The values in the main 2D plot (if any) controlled by the Plot ( ) dialog box have no effect on the moment distribution plot. The integrated moment value shown below the moment distribution plot is the sum of the area of the plot, but does not include the bending moment that is due to axial forces and variations in the centroid elevation of the slab (such as the bending moment caused by axial forces in the web and flanges of a T-beam). You should use design strips and design sections to determine design quantities as they capture both components of the bending moment. Figure 29-1 on page 159 shows a moment distribution plot for My moments drawn on a contour plot for Mx moments. The distribution plot shows My moments because the line drawn on the plan is parallel to the y-axis. The distribution plot has an integrated value of –657 kip-ft and a peak value of –73.9 kips (or –-73.9 kip-ft/foot). The contour plot values have no effect on the distribution plot values. If you used the Selected Plot Distribution tool (

RAM Concept

) instead of the

Figure 29-1 Moment distribution plot showing My moments on an Mx contour plot.

29.4.3 Shear distribution plots You can create shear distribution plots using the Vertical Shear Distribution tool ( ). The plot displayed along the drawn line shows the distribution of vertical shear force across the line. The values in the main 2D plot (if any) controlled by the Plot ( ) dialog box have no effect on the shear distribution plot. The integrated shear value shown below the shear distribution plot is the sum of the area of the plot. Design strips and design sections provide a more accurate calculation of this integrated value.

29.4.4 Axial force distribution plots You can create axial force distribution plots using the Axial Force Distribution tool ( ). The plot displayed along the drawn line shows the distribution of axial (horizontal) force across the line. The values in the main 2D plot (if any)

159

Chapter 29 controlled by the Plot ( ) dialog box have no effect on the axial force distribution plot. The integrated axial force value shown below the axial force distribution plot is the sum of the area of the plot. Design strips and design sections provide a more accurate calculation of this integrated value.

29.4.7 Summary Section distribution plots allow you to see the variation of analysis values across any line draw on the structure. These distribution plots are very helpful in understanding the behavior of the structure, but you should not use them for quantitative design purposes. You should always use design strips and design sections to determine design quantities

29.4.5 Selected distribution plots You can create selected distribution plots using the Selected Plot Distribution tool ( ). The plot displayed along the drawn line shows the distribution of the values shown in the main 2D plot (controlled in the Plot ( ) dialog box). The integrated value shown below the distribution plot is the sum of the area of the plot. This integrated value may or may not be useful depending upon the plotted quantity (for example, the integration of a topstress plot is a force/length value, which is largely useless). You need to take special care when using the Selected Plot Distribution tool ( ) with the “max” and “min” axis contour plots (such as a Service LC Max Bottom Stress Plan). The “max” and “min” stress plots show the maximum or minimum principal value at every point in the slab. At each point along a selected plot distribution of the principal values, the principal axes may be different. The integrated value for the distribution plot has mathematical meaning, but does not have any structural meaning. If you want to see the distribution of stresses (or moments, etc.) about a particular axis, you can use the Plot ( ) dialog box to set the contour plot axis (using the Value Plotted Axis) to be the axis of the results you want to view. The Selected Plot Distribution tool ( values for that axis.

) then shows the

29.4.6 Effects of averaging Distribution plots display the calculated results of the individual elements. At the shared edge of two elements, RAM Concept uses simple averaging. This produces reasonable results in most cases, but can cause distortions of the integrated result when RAM Concept averages a small element’s result with a large element’s result. The selected distribution plots are additionally affected by the plan averaging that occurs in the 2D plot controlled by the Plot (

29.5 Miscellaneous results information The following sections are for clarification of some results.

29.5.1 Top and bottom longitudinal reinforcement RAM Concept shows longitudinal reinforcement on plan with the following parameters: • number of bars • bar type (as defined as a design strip property) • length of the bars • bar spacing The reinforcement shown on the Rule Set Designs and Design Status layers represents what is required in addition to any specified user reinforcement and does not include development length considerations. For a complete consideration of all parameters including development length refer to the Reinforcement Layer. Figure 29-2 and Figure 29-3 show top reinforcement at a column. There are two callouts because the design strips terminate at the column. The required reinforcement is different on each side, as often happens. You need to rationalize this information and detail the bars in a logical manner. The left hand reinforcement is nine #5 bars, each 6.5 ft. long [nine 16 mm bars, each 1.8 m long].

Figure 29-2 Design Status: Latitude Top Reinforcement Plan (US units)

) dialog box.

This distortion caused by averaging is another reason why you should always use design strips and design sections to determine design quantities. Figure 29-3 Design Status: Latitude Top Reinforcement Plan (metric)

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RAM Concept

Chapter 29 Figure 29-4 and Figure 29-5 show bottom reinforcement. The reinforcement is thirteen #4 bars, each 9.5 ft. long [fifteen 12 mm bars, each 2.9 m long].

cross sections. If the reinforcement is placed away from the perpendicular orientation (such as that shown in Figure 296), the reinforcement quantity may need to be increased.

Figure 29-4 Design Status: Bottom Reinforcement Plan (US units)

Figure 29-5 Design Status: Bottom Reinforcement Plan (metric)

29.5.2 Reinforcement bar lengths Concept calculates the reinforcement bar lengths by determining termination points. The termination points are located at design strip segment cross sections where the bars are no longer required for any rule set design. The bar lengths shown on plan do not include development or embedment lengths.

29.5.3 Orientation of reinforcement

Figure 29-6 Reinforcement drawing and plotting relative to local axis

29.5.4 Shear reinforcement Concept shows shear reinforcement zones on plan with the following parameters: • number of spaces in the zone • number of legs per shear reinforcement set

Concept draws and plots reinforcement along an axis determined by the first and last cross section of the design strip. Top bars appear “over” the axis and parallel to it. Bottom bars appear “under” this axis and parallel to it. Reinforcement plots are perpendicular to the axis. Figure 29-6 shows the axis, line A-B, for a middle strip. Point A is at the midpoint of the first middle strip cross section, and point B is the midpoint of the last middle strip cross section. Design and capacity calculations always assume that the reinforcement (other than tendons) is perpendicular to the

RAM Concept

• spacing of the sets • length of the zone Figure 29-7 shows shear reinforcement. For US units and bar size, the zone is 2.78 ft. long and has 4 spaces with two #4 legs @ 8.34” centers. For metric units and bar size, the zone is 0.772 m long and has 4 spaces with two 12 mm legs @ 193” centers. For both unit systems, there are five shear reinforcement sets (spaces + 1).

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Chapter 29 If a punching section can be classified by any of the “standard” rules, it is considered to be a “standard” section. The rules for “standard” sections are: 1 Interior Rectangular:

• must be uniform thickness • must have 4 sides • section centroid must coincide with column centroid • opposite sides must be parallel and have same length • adjacent sides must be perpendicular • must be continuous (no gaps) 2 Edge Rectangular:

• must be uniform thickness Figure 29-7 Design Status: Shear Reinforcement Plan (US and metric units).

• must have 3 sides • opposite sides must be parallel and have same length • adjacent sides must be perpendicular

29.5.5 Punching Shear Results Punching shear design notes appear in Chapter 66, “Punching Shear Design Notes”. Non-Standard Sections: ACI 318 and CSA A23.3

Some times the punching shear status is “Non-Standard Section”. This is a warning, not an error. “Non-Standard Section” means that at least one of the critical sections that RAM Concept is investigating for that column does not perfectly fit one of the three cases: interior, edge and corner. When you get a “Non-Standard Section”, you need to inspect the critical sections that Concept has defined, and use your engineering judgment to determine if you feel they fit the ACI/CSA punching model (you should always visually inspect the critical sections, even if Concept does not flag them as non-standard). Concept still calculates a stress ratio for non-standard sections.

• can only have two discontinuous ends (assumed at slab edge) 3 Corner Rectangular:

• must be uniform thickness • must have 2 sides • sides must be perpendicular • can only have two discontinuous ends (assumed at slab edge) 4 Interior Round (circular shape idealized into straight line

segments): • must be uniform thickness • section centroid must coincide with column centroid • all segment ends must be on same radius from the center of the column • must be continuous (no gaps) 5 Corner or Edge Round (circular shape idealized into

Non-Standard Sections: AS3600, BS8110, EC2 and IS 456

Some times the punching shear status is “Non-Standard Section”. This is a warning, not an error. “Non-Standard Section” means that at least one of the critical sections that RAM Concept is investigating for that column does not perfectly fit one of the three cases: interior, edge and corner. When you get a “Non-Standard Section”, you need to inspect the critical sections that Concept has defined, and use your engineering judgment to determine if you feel they fit the code punching model (you should always visually inspect the critical sections, even if Concept does not flag them as non-standard). Concept still calculates a stress ratio for non-standard sections.

162

straight line segments): • must be uniform thickness • column must be round • can only have two discontinuous ends (assumed at slab edge) • can only have two segment end points that are a different radius from the center of the column than all other segment end points (assumed at slab edge) • discontinuous segment end points must be the “off radius” points (at slab edge)

Note: The rules are applied to EC2 sections before the corners are filleted.

RAM Concept

Chapter 29

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Chapter 29

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Chapter 30

30 Plotting Results The plot settings control which results plot on a plan or a perspective. The default file setup has specific plot settings for particular plans and perspectives. You can customize these settings or create new plans and perspectives that show your desired plots.

Slab plots are available for loading, load combination and rule set layers.

Plot settings are controlled via the Plot dialog which is accessed through the Plot command (

).

30.1 Setting the plotted results You may decide to change the settings to suit your requirements. To change a plot setting:

1 Open the plan or perspective you want to change. 2 Choose View > Plot (

).

The Plot dialog box appears. 3 Select a tab and check Active to make that plot active.

Figure 30-1 The plot dialog with slab result plotting active.

The “Animation Control” is described in more detail in the section, “Plotting Results.”

4 Make changes and click OK.

Note: The name of a plan or perspective is often indicative

30.2.1 About slab plotting contexts

of its plot settings. If you change the plot settings, you may want to rename the plan or perspective.

There are three possible contexts: “Standard”, “Max” and “Min”. The Max and Min context are used to envelope the maximum and minimum values for each point in the slab.

30.2 Slab Checking the Active box in the Slab tab allows you to display and control various slab analysis plot quantities such as moment, shear, axial, torsion, deflections, and area spring reactions. For plotting axial stresses or in-plane shear stresses, select the depth at which to plot the value. Other plot values are not dependent upon depth. We recommend curve smoothing for contour plots. Without curve smoothing, contours will be plotted element by element, which can make it difficult to observe the results of a larger region (also, for some plotted quantities, nothing will be shown unless curve smoothing is on). RAM Concept allows you to define a resolution for the selected plot value. Finer plot resolutions require longer screen regeneration times. For contour plots, you can control the frequency of the contour lines by unchecking “Use default magnitudes” and entering the desired contour value. For color contour plots, you can set the upper and lower limits of the contour values by entering the minimum and maximum values.

RAM Concept

While the meaning of the Standard, Max and Min contexts is somewhat self-evident, Table 30-1 lists how Concept calculates these values considering load patterns and standard and alternate load factors.

30.2.2 Max and Min context slab plot limitations Concept stores only a limited number of slab analysis values. For example, standard, maximum and minimum Mx, My and Mxy values are stored, while moment values about other axes (not x- or y- axis) are calculated via Mohr’s Circle calculations. Similarly, standard, maximum and minimum Px, Py, Vxy, Mx, My and Mxy values are used to calculate stress values at the top, center and bottom of the slab. Because minimum and maximum values are not stored for these derived values, the calculation of the minimum and maximum values is approximate. Example: if one loading pattern gives an x-deflection of 10 and a y-deflection of 0, while another pattern gives a xdeflection of 0 and a y-deflection of 10, the Max context

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Chapter 30 deflection will be reported as 14.4, even though the true maximum deflections never exceeded 10.

• Lateral deflection values where the center of the slab is not at elevation zero.

The following slab maximum and minimum context plot values should always be considered approximate: • Values for any axis that is not the x- or y- axis. • Stress values for any depth that is not mid-depth. • Lateral deflection values for any depth that is not middepth.

Layer Type

Standard

Loading

Values with full applied Maximum values that occur considloads (no pattern loading) ering each pattern loading (complete with pattern factors) and the full loading.

Linear combination of Loading Standard values Load Combination using the Standard load factors Single

Lateral Group

(not available)

Load Combination

Max

(not available)

Minimum values that occur considering each pattern loading (complete with pattern factors) and the full loading.

Values that occur when combining all loadings, taking the maximum value of the following four values for each loading:

Values that occur when combining all loadings, taking the minimum value of the following four values for each loading:

• Standard Load Factor * Max

• Standard Load Factor * Max

• Alt Load Factor * Max


• Standard Load Factor * Min

• Standard Load Factor * Min

• Alt Load Factor * Min


Values that occur when combining all gravity loadings, taking the maximum value of the following four values for each loading:

Values that occur when combining all gravity loadings, taking the minimum value of the following four values for each loading:

• Std Load Factor * Max

• Std Load Factor * Max



• Std Load Factor * Min

• Std Load Factor * Min



Plus the maximum single value of all of the lateral loadings' (of the correct type) values:

Rule Set

Min

Plus the minimum single value of all of the lateral loadings' (of the correct type) values:

• Std Lateral Load Factor * Max

• Std Lateral Load Factor * Max

• Alt Lateral Load Factor * Max

• Alt Lateral Load Factor * Max

• Std Lateral Load Factor * Min

• Std Lateral Load Factor * Min

• Alt Lateral Load Factor * Min

• Alt Lateral Load Factor * Min

Maximum of all of the related load combination values

Minimum of all of the related load combination values

Table 30-1 Calculation of Standard, Max and Min values

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30.3 Reaction Checking the Active box in the Reaction tab allows you to display and control analysis reaction quantities. Selecting the Standard context button displays reactions corresponding to the standard results (more information about standard and enveloping results is available in Chapter 50, “Analysis Notes”). For the standard results, you can display any number of reactions for column above/below, wall above/below, point spring/support, line spring/support, and the standard reactions used for the punching checks. If a column above and below occur at the same location in plan, and both Column Above and Column Below boxes are checked, the sum of the reactions is shown at that location. The same holds true for walls above and below.

Figure 30-3 Plot dialog reaction tab

The other buttons in the Context group are for the enveloped results. Concept displays reactions for columns (above/below) and punching checks for the envelope result of the selected context. Wall reactions will be enveloped and available for plotting in future versions. The “standard” reaction context values are only available for loading and load combination layers, while the six enveloped contexts are available for loading, load combination and rule set design layers.


30.4 Strip


Checking the Active box in the Strip tab allows you to display analysis results for the design strips. Each plot value represents the variation of the selected value at each design strip segment cross section (along the axis of each strip selected). Plots related to the maximum and minimum moments and shears can be displayed, enabling the envelope for a particular plot value to be displayed. The Torsion value is the torsion about the centroid of the design strip segment, in equilibrium with the element nodal forces. The Twist value is the component of the torsion due to the slab twisting moment (Mxy for design strips parallel to the x- or y- axes) calculated from the element stress predictions

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Chapter 30 (and is not necessarily in equilibrium with the element nodal forces). The Twist value is not recommended for use in torsion design.

Section analysis plots are only available for rule set design layers.

Absolute Twist is the sum of the absolute value of the twist along the cross section. This value differs from the “Twist” value in that it is always positive, and that in its calculation, twist values of different signs do not cancel out. The Absolute Twist value is not used in design unless Wood-Armer torsion design is selected.

Note: The accuracy of the Twist and Absolute Twist values are determined from element stress predictions and are dependent upon the quality and the refinement of the mesh. Unlike the Torsion value, there is no guarantee that these values will be in equilibrium with the applied nodal loads. Definitions of other values can be found in Chapter 50, “Analysis Notes”. The “standard” strip context values are only available for loading and load combination layers, while the four enveloped contexts are available for loading, load combination and rule set design layers.

Figure 30-6 Plot dialog section analysis tab.

30.6 Section Design Checking the Active box in the Section Design tab allows you to plot top, bottom and shear reinforcement quantities corresponding to Concept’s final design or a design for a particular rule set. The “Top Developed” and “Bottom Developed” values represent the amount of fully developed top and bottom reinforcement that is required at each location. Section design plots are only available for rule set designs and the design status layers.

Figure 30-5 Plot dialog strip tab.

30.5 Section Analysis Checking the Active box in the Section Analysis tab allows you to display analysis and design results for the design strips including moments, shears, stresses, crack width, and effective curvature ratio. The plotted analysis results are for the envelope results. They can be plotted against the design capacity resulting from RAM Concept’s final design. Note that some quantities may not have capacity values defined.

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Figure 30-7 Plot dialog section design tab

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30.6.1 About section design “context” plots

30.6.2 About skyline plots

The Section Design plot group box, “Context” allows for three possible contexts:

When you select the “With Span Detailing” or “User Provided Reinf” contexts, Concept plots the reinforcement with a “skyline” plot.

• With Span Detailing • Without Span Detailing, and • User Provided Reinf. Span detailing is explained in Section 53.1 on page 415 of Chapter 53, “Reinforcement Notes”. The effects of the Span Detailing Contexts on plots are explained in Table 30-2 and Table 30-3. For the Design Status layer, the context of “With Span Detailing” includes the effects of the assumed reinforcement development calculations in the plots of developed reinforcement.

In a skyline plot, each calculated value is valid for a portion of the span (as shown by a horizontal line) instead of the values being interpolated between cross sections. While this is primarily just a graphical difference, the actual detailing of the reinforcement into bar callouts is performed using the skyline plot values. For rule set designs, the effects of the Span Detailing Context (other than the skyline plotting) are as shown in Table 30-2 below. For the Design Status layer, the effects of the Span Detailing Context (other than the skyline plotting) are as shown in Table 30-3 below.

Value

Without span detailing

Top

As calculated per section Values calculated per section are Vector component of area of user lengthened according to the span individual bars intersected by the detailer rules (see Section 53.1 “Span cross sections detailing” of Chapter 53, “Reinforcement Notes”).

Bottom Top and Bottom Top Dev

With span detailing

As calculated per section As calculated per section

Vector component of developed area of user individual bars intersected by the cross sections


(none)

Bottom Dev Shear

User provided reinforcement

Shear Density Shear Spacing Table 30-2 Effects of span detailing context on rule set plots

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Value

Without span detailing

Top

As calculated per section Values calculated per section are Vector component of area of user lengthened according to the span individual bars intersected by the detailer rules (see Section 53.1 “Span cross sections detailing” of Chapter 53, “Reinforcement Notes”).

Bottom Top and Bottom Top Dev Bottom Dev

With span detailing

User provided reinforcement

As calculated per section Plotted values are the maximum of Vector component of developed area the reinforcement calculated per sec- of user individual bars intersected by tion and the amount of developed the cross sections reinforcement calculated from the span-detailed amounts of non-developed reinforcement (see Section 53.1 “Span detailing” of Chapter 53, “Reinforcement Notes”). These values are used in the final capacity check calculations.

Shear


(none)

Shear Density Shear Spacing Table 30-3 Effects of Span Detailing Context on Design Status Plots

30.7 Punching Analysis Checking the Active box in the Punching Analysis tab allows you to display information about the punching analysis including stresses for each critical section for any of the enveloped force sets. The values displayed are for the selected critical section(s) with the selected force set, and are not necessarily the worst case for the column. The most critical punching case can always be displayed by selecting the Max Stress Ratio button and checking Section 1. Punching analysis plots are only available for rule set design and the design status layers.

Figure 30-8 Plot dialog punching analysis tab

30.7.1 Punching Shear Results Punching shear design notes appear in Chapter 66, “Punching Shear Design Notes”. There is discussion of “Non-Standard Section” in “Punching Shear Results” on page 162.

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30.8 Vibration Analysis

to the minimum values, then grow to the maximum and repeat.

30.8.1 Vibration Results Vibration analysis notes appear in Chapter 67, “Vibration Analysis Notes”.

Figure 30-11 Plot animation controller

Playing the animation is controlled by buttons in the main tool bar. Press the play/pause button to play or pause the animation. The slider controls the duration of the animation. When set at the leftmost value (-), the duration of the animation (from minimum to maximum values) will be approximately 10 seconds. The next slider positions set the duration to 5 seconds, 2 seconds and 1 second. The rightmost value (+) plays the animation as fast as possible. Many Concept functions, such as zooming and panning, will function while the animation is playing, although some mouse motions will freeze the animation temporarily. The animation speed slider can be changed at any time.

Figure 30-9 Plot dialog vibration analysis tab

30.9 Plot Animation Controls Slab and Vibration plot data can be animated in an endless loop. The animation scales most plot values from their normal values to zero and back. Vibration mode plot values are scaled from +1 to -1 to simulate oscillating values. You have control over playing the animation, the number of animation frames, and the animation speed.

The geometry for each animation frame is cached the first time the frame is displayed. A small status box is displayed when the frame is being computed. Each subsequent display of a frame uses the cached geometry for fast display. Pausing or resuming the animation while the animation frames are being computed does not affect the cached data. However, the animation geometry cache is discarded when switching to another plan or perspective view, and must be recomputed when switching back. Any change to the plot settings also invalidates the cached geometry. The cached geometry can consume a significant amount of process memory. Memory consumption grows linearly with the number of frames. Intensity plots generally consume more memory than Color Contour plots, and Color Contour plots consume much more memory than Contour line plots. The static portions of the scene, e.g. slabs, walls and columns, do not contribute to the memory consumption.

30.10 Difference Plot Controls Figure 30-10 Plot animation setup To enable animation:

1 Check the Enable Animation box. 2 Enter a positive number in # Frames.

When the Plot Settings dialog is confirmed, the first frame of the animation is displayed with the maximum plot values. When the animation is played, the data will shrink

The difference between two plot layers can be plotted if the results of the two layers are compatible. Select the layer to be subtracted from the Diff Layer choice box, or None if no difference is desired.

Figure 30-12 Plot difference control

Section Analysis, Section Design, Punching Analysis and Vibration results cannot be differenced. Otherwise, a

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Chapter 30 difference layer is compatible with the plot layer if the difference layer has results available for the data selected in the plot layer. The dialog cannot be be confirmed if there is a difference incompatibility. For example, consider Plot Layer set to Self-Dead Loading and Diff Layer set to Code Minimum Design. The Code Minimum Design layer has results for Slab, Reaction and Strip, therefore any (or all) of these layers can be active. The Code Minimum Design layer does not have standard context results; selecting the standard context on any of the

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tabs will be incompatible. The text next to the Diff Layer choice box will describe the first incompatibility detected. Now consider the layers reversed, Plot Layer set to Code Minimum Design and Diff Layer set to Self-Dead Loading. Any settings can be differenced on the Slab, Reaction and Strip tabs, because the Code Minimum Design layer contains a subset of the results available in the Self-Dead Loading layer. However, activating any one of the Section Analysis, Section Design or Punching Analysis tabs will be incompatible.

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31 Using the Auditor • Pass 1 There will be times when a design result calculated by RAM Concept may be confusing or unexpected. This could be due to incorrect input, an unusual set of resultants (for example: a negative moment at mid-span), or a code rule interpretation. The Auditor assists in displaying design information for you to review.

• Pass 2 • Final check

31.3 About the information displayed by the Auditor 31.1 How the Auditor can assist the design process The Auditor is a tool that displays input data, parameters, resultants and code specific results for design strip cross sections, design sections and punching checks, in text format.

The information displayed by the Auditor is for a single cross section of one span segment strip, or a design section. The Auditor displays the following:

1 Design strip and cross-section number, or design section

number 2 Concrete components for a cross section

The Auditor displays information that could be useful for:

• number of concrete blocks

1 Checking input data such as reinforcement bar cover.

• top and bottom elevation of each block

2 Checking calculated data such as the elevation of the

• depth and width of each block

center of a reinforcement bar. 3 Reviewing the rule set designs (service, strength etc.) 4 Checking the envelope of resultants (moment, shear

• initial and final strengths (cylinder and cube) • initial and final Ec (modulus of elasticity) values

force, axial force etc.).

• density

5 Revising the number of strands in a tendon to satisfy code

• inclusion or exclusion of block from shear core

stress limits.

See “Concrete “Core” Determination” on page 405 for discussion of shear core. 3 Reinforcement properties for each bar type

31.2 About the three design steps RAM Concept performs its design in 3 steps: Step 1: Each Rule set performs its “Pass 1” selection of reinforcement. For most rule sets this is the entire design.

• elevation • yield stress • Ec (modulus of elasticity) value • bar area • bar diameter

Step 1b: The selected reinforcement of all the rule sets is summarized. Step 2: Each Rule set performs its “Pass 2” selection of reinforcement needed in addition to that summarized in step 1b. For most rule sets nothing happens in this step, but for some rule sets –such as shear design and ductility design the summarized step 1 reinforcement needs to be known before the design can be performed. Step 2b: The selected reinforcement of all the rule sets is summarized. Step 3: Each Rule set performs a final check (no reinforcement is added in this step) and final analysis. The Auditor reports the three steps as the following:

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4 Tendon properties for each tendon type

• elevation of cgs (center of gravity of strand) above datum • ultimate strength (stress) • yield stress • effective stress • Ec (modulus of elasticity) value • area of strand • bonding • R-component [the component of the tendon parallel to the design strip cross section (perpendicular to the design strip spine)] 173

Chapter 31 • S-component [the component of the tendon perpendicular to the design strip cross-section (parallel to the design strip spine)] • Z-component [the vertical component of the tendon across the cross-section (only used for hyperstatic calculations)]

• force • force elevation • Untensioned reinforcement forces for each bar • elevation • strain

• length

• stress

• initial concrete strain

• bar area

• duct width

• force

• number of strands per duct

• Post-tensioning forces for each tendon

• cross sectional area per strand

• elevation

• number of ducts

• cross-section strain

5 Base design envelopes (for each Rule Set Design):

The envelopes for maxima and minima of moment and shear force are displayed. These are modified, as appropriate, for torsion and axial force design. The envelopes list the following resultants: • Vr (horizontal shear)

• component cross-section strain (considers tendon angle) • Tendon Force (effective force in cross section plane)

31.4 Using the Auditor

• Ps (axial tension) • Vz (vertical shear) • Mr (bending) • Ts (torsion) • Mz (diaphragm bending) 6 Reinforcement (for each Rule Set Design):

Depending upon the rule set, RAM Concept adds reinforcement to the cross section.

The Auditor can be used for specific rule set designs, or for the design summary.

Note: A rule set audit has significantly less data than a design summary audit. As such, a rule set audit may be more useful. To use the Auditor for a rule set design:

1 Choose Layers > Rule Set Designs > Selected Design >

Selected Plan

• As Top

2 Select the Auditor tool (

• As Bot.

3 Click on the plan at the design strip cross-section, or

• As Shear Density • As Shear Spacing • As Shear (density multiplied by spacing) Brackets appear after each result showing which code rule governed.

).

design section, you wish to audit. The Auditor window opens. 4 Scroll to find the information you require.

Note: You may find it convenient to make the design cross sections visible for the purpose of selecting the correct one.

7 Cross Section Forces (Analysis)

Note: The Auditor selects either (i) the nearest cross-

Depending upon the rule set, the Auditor displays cross section forces and other information.

section (of a visible span segment strip) to the point you click, or (ii) nothing, if there is no cross section within 3 feet [1m] of the point you click. The cross-sections themselves do not need to be visible.

• Cross Section Strains • curvature • top, centroid and bottom strains • Concrete Forces for each block • top and bottom stress

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Note: The Auditor will not work if a Calc All has not been performed.

Note: The Auditor’s results may not be current if the analysis is not current. (If the Calc All option is grayed-out ( ), the analysis results are current).

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Chapter 31 To use the Auditor for the design summary:

1 Choose Layers > Design Status > Selected Plan.

31.6 About the information displayed by the Punching Check Auditor

2 Follow instructions for “rule set design” above.

The information displayed by the Punching Check Auditor is for a punching check at a single column.

31.5 Using the Auditor for guidance on post-tensioning

The Auditor displays the following:

1 Punching check number 2 Location (coordinates)

Certain codes limit the service stresses and designers are required to comply with the limits. The Auditor displays advice on how much additional post-tensioning strand is required in a design strip to satisfy certain code clauses.

3 Geometry

• axis angle • radius

This information is accessible from many plans, but the instructions below are for using the Service Rule Set Design.

4 Cover to CGS

To use the Auditor for guidance on post-tensioning:

7 Resultant envelopes


8 Critical section perimeter properties

Status Plan 2 Select the Auditor tool (

5 Concrete Strength 6 Precompression

• number of critical sections ).

3 Click on the plan at the design strip cross-section which

has failed a stress criterion and for which you require guidance.

• perimeter length • perimeter depth • torsion strip properties (for AS3600)

The Auditor window opens.

9 Unreinforced stress ratio

4 Scroll to the text bordered by two lines of asterisks (top

10 Stud shear reinforcement rail properties (if required for

and bottom) near the bottom of the audit. If the maximum tensile stress is within code then no information will be displayed. If the calculated concrete tensile stresses exceed the allowable limit then the Auditor suggests the percentage increase in strand required to satisfy the stress limit.

design). 11 Summary

31.7 Using the Punching Check Auditor The Auditor can be used for the strength rule set design, or for the design summary. To use the Punching Check Auditor for the strength rule set design:

1 Choose Layers > Rule Set Designs > Strength Design > Figure 31-1 Auditor text indicating percentage increase required to comply with code.

Note: The precompression and balance effects of a tendon are not necessarily limited to the area (and design strip) where the tendon is located. Due to the diversion of prestress (bleed of P/A) beyond the design strip the suggested percentage increase may not be exact.

Note: If there are tendons intersecting the cross-section at an angle other than ninety degrees then the suggested percentage increase may be inaccurate.

Selected Plan 2 Select the Punching Check Auditor tool (

).

3 Click on the plan at the punching check location you wish

to audit. The Auditor window opens. 4 Scroll to find the information you require.

Note: The Auditor will not work if a Calc All has not been performed.

Note: The Auditor’s results may not be current if the analysis is not current. (If the Calc All option is grayed-out ( ), the analysis results are current).

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Chapter 31 To use the Auditor for the design summary:

Follow instructions for the “strength rule set design” above.

1 Choose Layers > Design Status > Selected Plan.

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32 Using the Report Viewer It will sometimes be desirable to save or print a report for a particular aspect of the design. The report viewer enables this functionality for punch check results.

32.2 Saving Reports It will sometimes be desirable to save generated reports. To save reports displayed in the Report Viewer:

1 Select File>Save from the Report Viewer menu.

32.1 Using the Report Viewer

2 Enter a filename to save the file. The default file

extension will be .crvz for RAM Concept Reports. The Report Viewer can be invoked for punch checks from the design strip layer, the design summary layer, or for an individual rule set design layer. The information the report contains will always be the entire design summary. To use the Report Viewer:

1 Select the Report Viewer tool (

32.3 Opening Previously Saved Reports To open reports previously saved in the Report Viewer:

).

2 Draw a rectangle around all the punch checks you wish

to generate a report for. The Report viewer window opens.

1 Select File>Open from the Report Viewer menu or the

RAM Concept menu. If opening from the RAM Concept menu, select “RAM Concept Reports” under “Files of type:”. 2 Type or select the filename of the file to be opened.

3 A report for each punch check will be contained on an

individal tab. Select the tab for the desired punch check.

Note: The Report will not be displayed if a Calc All has not been performed.

32.4 Printing Reports

Note: The generated report’s results may not be current if

To print reports generated in the Report Viewer:

the analysis is not current. (If the Calc All option is grayedout ( ), the analysis results are current).

1 Select File>Print from the Report Viewer menu. 2 After configuring the desired print settings, select the

print icon from the toolbar.

Note: The resolution of the printed report can be controlled by using the zoom controls on the View menu of the Report Viewer.

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33 Using the Estimate When preparing a design, it can be useful to know the amount and cost of the materials used in the model. The estimate window serves this purpose.

Mild Steel Reinforcing

The estimate is particularly useful for comparing preliminary schemes. You can also use it to compare changes made to a design.

The weight of reinforcement based upon the detailed reinforcement in the Reinforcement layer. This does include bar hooks, but does not include laps. The quantities do not include bars not shown in the Reinforcement layer such as “detailing” or tendon support bars.

RAM Concept automatically calculates material quantities. Specified unit costs allow supply and installation costs to be calculated

33.3 Editing the unit costs

33.1 Viewing the estimate

You can only edit unit costs. The estimate separates unit costs into materials and installation (labor). To edit the unit costs:

The Estimate window lists the different material quantities and their unit costs for supply and installation (labor). To view the Estimate:

1 Choose Report > Estimate. 2 Enter the costs for each material.

Note: The costs update when you press Enter or Tab.

1 Choose Report > Estimate.

33.2 What the estimate calculates The material quantities calculated are: Concrete

The volume of the concrete floor excluding supports. Formwork

The area of horizontal soffit formwork. Post-Tensioning

The weight of strand based upon tendon plan length. This does not include stressing tails or allowance for drape.

RAM Concept

33.4 About unit costs Unit costs can vary for many reasons, including the following: • Region (labor availability and skill). • Size of the floor and the project. • Formwork system (usually flat slabs are more economical to form than beams). • Post-tensioning costs are not the same for different systems. Unbonded systems are often less expensive in some countries, but this may not be true if large bonded tendons are used in beams. • Large diameter reinforcing bar is generally less expensive than small diameter bar for materials and labor.

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34 Printing RAM Concept provides a range of printing customization options to help you create professional printouts and reports. You control the information included on a page and in a report. Every window in RAM Concept can be printed individually or as part of a report. This chapter describes the printing features you can use to achieve the result you want and offers techniques for printing efficiently.

Note: See “Determining the fit of plans” on page 182 for more information on setting the print scale of plan windows.

34.1 Basic printing instructions You can selectively print windows, or the entire report. To print a window:

1 Make the window you want to print the active window. 2 Choose Report > Print Window. 3 Select the printing options you want. See “General

printing options” on page 181 for more information.

Consult your printer documentation for information on setting up your printer and selecting the appropriate printer driver.

34.2.2 Page range In the Page Range section of the Print dialog box, select which pages to print: • Use the All option to print all the pages in the report, or all the pages that are required to print the active window. • Specify the range of pages you want to print. Type a hyphen between two numbers to print the pages in that range (inclusive). You must type the numbers separated by hyphens in ascending order (4-7, not 7-4).

34.2.3 Number of copies In the Print dialog box, the Number of copies option indicates the number of printed copies of the print job you want. Enter a value from 1 to 9999.

4 Click Print.

34.2.4 Printing to PDF To print the report:

1 Choose Report > Print Report 2 Select the printing options you want. See “General

printing options” below for more information.

RAM Concept has the ability to print directly to the .pdf file format. Desired paper size, orientation, and margins can be set up by choosing the Report > Setup PDF Export dialog.

3 Click Print.

Note: To make sure you get the desired printing results, preview the print job before you print. See “Previewing the print job” on page 183 for more information.

34.2 General printing options The Print dialog tells RAM Concept what printer to use, which pages to print, and how many copies you need. Review these settings every time you print a window or report.

34.3 Select and Configure Printer options In the Select and Configure Printer dialog box, you can set the printer, page size and source, default orientation, and margin size for your printed pages. These per-printer settings are stored on your system and are used as the default settings every time you print. To change the print setup options:

1 Choose Report > Select and Configure Printers. 2 Select the printer that is of interest. 3 Click on the Page Setup button and select the options that

34.2.1 Printer selection Specify the printer you want RAM Concept to print via the Select and Configure Printers menu item. The printer can also be selected in the Select Printer section of the Print dialog, but the per printer stored settings will not be used. With the latest compatible drivers installed, RAM Concept can print on any Windows printer or plotter connected directly to your computer or connected via a network. RAM Concept

you want in the dialog that opens.Click OK. 4 Click OK.

34.3.1 Printer selection The last printer selected in the Select and Configure Printers dialog is the default printer for RAM Concept.

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Chapter 34 RAM Concept can print on any printer with the appropriate printer drivers installed.

To specify the printed area with coordinates:

1 Choose View > Print Area or double click on the Print

Area tool (

34.3.2 Paper size and source Select the paper size and paper source the printer uses from the Paper section of the Page Setup portion of the Select and Configure Printer dialog. The printer selection dictates the options for the size and source.

34.3.3 Default orientation In the Orientation section of the Page Setup portion of the Select and Configure Printers dialog, select the default page orientation: • Use Portrait for a vertical page orientation. • Specify Landscape for a horizontal page orientation. Page orientation is also customizable for each individual printed window in the Report Contents window. See “Printing optimizations” on page 183 for more information.

34.3.4 Margin size Set the page margins in the Margins section of the Page Setup portion of the Select and Configure Printers dialog. If the left, right, top, or bottom margin sizes you select overlap, or they are off the paper, an alert message appears.

).

2 Uncheck the option to “Automatically calculate printing

area” and enter the left, right, top, and bottom coordinates in the Printing Area Setup dialog. Check “Set for all plans” if you want this printing area to be used by all plans. 3 Click OK.

34.5 Printing the desired perspective viewpoint The saved print viewpoint determines how a perspective window prints. Sometimes a viewpoint that looks good on screen may not appear as desired in print due to the dimensions of the page. Remember to examine the print preview carefully after setting the print viewpoint to verify that the scale and orientation of the model fit on the page as intended. Use the Set Print Viewpoint tool ( ) to save the print viewpoint to what is visible on screen. This viewpoint does not change unless you reset it. You can manipulate the model on screen without affecting the saved print viewpoint. To display the saved print viewpoint, use the Show Print Viewpoint tool (

).

To set the print viewpoint:

1 Adjust the on screen viewpoint by:

34.4 Determining the fit of plans Plans print according to their Print Area and Print Scale settings. Everything within the printing area boundary prints using as many pages as necessary to print at the desired scale.

).

• Rotating the model with the Rotate about x- and y-axes tool ( (

) and the Rotate about z-axis tool

).

).

2 Enter the scale in the Print Scale dialog and click OK.

Note: Typically, you want to check “Set for all plans” in the Print Scale dialog if you are printing a report. To specify the printed area on the plan:

1 Select the Print Area tool (

using the Scale tool (

• Zooming to show the desired portion of the model.

To specify the print scale:

1 Select the Print Scale tool (

• Setting the relative scales of the coordinate axes

).

2 Click at two opposite corners to identify the rectangular

• Setting the projection to Parallel Projection ( or Perspective Projection ( Solid Modeling (

) and the modeling to

) or Wire Modeling (

2 Click Set Print Viewpoint (

)

).

).

To show the set print viewpoint on screen:

1 Click Show Print Viewpoint (

).

boundary.

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34.6 Previewing the print job Preview the print job before you send it to the printer to ensure the images and text fit as desired on the chosen paper with the specified margin, and orientation settings. See “Select and Configure Printer options” on page 181 for more information on how to change the page setup. To preview the active window print job:

1 Choose Report > Window Preview. 2 Examine the preview as described in the following

sections and click Close. To preview the report print job:

1 Choose Report > Report Preview. 2 Examine the preview as described in the following

sections and click Close.

You can print each window or report item in RAM Concept in Portrait or Landscape orientation. The default page orientation is set in the Select and Configure Printer dialog box. See “Select and Configure Printer options” on page 181 for more information on setting the default orientation. You may want some items in a report or a specific window to print in a different orientation than the rest. Use the Orientation column of the Report Contents window to specify the orientation of an item. Choose Default to use the Page Setup settings, or Portrait or Landscape to override the Page Setup orientation. To set the orientation of a particular window or item:

1 Make sure the Orientation column is visible in the Report

Contents window. You may need to widen the window or scroll horizontally. 2 Click on the Orientation column value for the item to

toggle between Default, Portrait and Landscape. A value of Default in the Orientation column sets the orientation to the default orientation set in the Page Setup dialog box.

34.6.1 Zooming Scale the print preview by setting the zoom percentage in the print preview window. You can choose a zoom factor of 500%, 200%, 150%, 100%, 75%, 50%, 25%, 10%, Fit Page or Fit Width, or you can type a numeric percentage of your choice (between 5% and 500%).

34.6.2 Viewing multiple pages at once You can view the print preview one, two, or four pages at a time. Use One Page (

34.7.1 Customizing page orientation

) to view one page of the print job

at a time. Click Multi Page ( ) and select 2-up to view two pages at a time or 4-up to view four pages at once.

34.6.3 Paging through the print job The print preview automatically opens to the first page in the print job. Use Next (

) to page forward through the

print job and Previous (

) to page back.

34.7.2 Customizing the printed appearance of plans and perspectives In the same way that you change the colors, font, and line type of plan and perspective windows on the screen, you can customize their appearance in print. Use the Print tab for schemes in the Appearance dialog to set the appearance settings for a plan or perspective you wish to print. See “Changing colors, font, and line type” on page 13 for more information about appearance schemes and changing appearance settings. If you want the printed plan or perspective to have the same appearance settings as what you see in the respective window, click Set Same As Screen on the Print tab. In most cases, you want: • background color in printing to be white (no printed background) • print font size to be smaller then the screen font • print line scale to be larger then on screen

34.7 Printing optimizations

To change the printed appearance of a plan or perspective:

1 Make the Plan or Perspective the active window.

To achieve the best possible results when printing, you may need to customize the page orientation and appearance settings for the individual report items (or windows).

RAM Concept

2 Choose View > Appearance. 3 Specify options on the Print tab of the Appearance

Settings dialog box and click OK.

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34.8 Changing the report contents

every plan, perspective, and text table on that layer to “No”.

The contents of the report are customizable to suit your specific needs. You have control over what plans, perspectives and text items are included in a report and their order and orientation. You change the report contents through the Report Contents window.

To include or exclude a report item:

1 Make sure the Include column is visible in the Report

Contents window. You may need to widen the window or scroll horizontally. 2 Click on the Include column value for the item you wish

to include or exclude to toggle between Yes and No. A value of Yes in the Include column includes the item in the report printout while a value of No excludes the item.

Note: If you want to include an item in the report, make sure every item in the hierarchy above it is also included. The following is an example list of windows you might include in a report for an elevated PT slab using the ACI 318 design approach: • Report Cover • Units • Signs • Materials • Loadings • Load Combinations • Design Rules • Estimate • Element: Standard Plan Figure 34-1 In the Report Contents Window, you can change the order of report items, set whether an item is included in the report, and change the printed orientation or an item.

• Element: Slab Summary Plan • Element: Structure Summary Perspective • Latitude Tendon: Standard Plan

34.8.1 Including items in the report Any window can be included as an item in the report. Modify the selection of plans, perspectives and tables to be included in the report via the Report Contents window. Toggle the Include column value to specify whether an item is included in the report or not. For something to print in the report, it requires that its Include value is “Yes” and every item above it in the report hierarchy is also “Yes”. For example, if you want the Standard Plan on the Latitude Tendon Layer to be included in the report, the plan itself should have an Include value of “Yes”, the Latitude Tendon layer should be “Yes” and the Layers folder should be “Yes”. Likewise, with an Include value of “No” for the Criteria folder, RAM Concept does not include anything in that folder in the report. This functionality is especially useful if you want to omit everything on a particular layer from the report. You can do so with one click, rather then changing the Include value of

• Longitude Tendon: Standard Plan • Temporary Construction (at Stressing) Loading: All Loads Plan (if used) • Other Dead Loading: All Loads Plan • Live (Reducible) Loading: All Loads Plan • Live (Unreducible) Loading: All Loads Plan • [other live loadings (Storage, Roof) if used] • Service LC: Deflection Plan • Factored LC: Mx Plan • Factored LC: My Plan • Factored LC: Reactions Plan • Reinforcement: Latitude Bars Plan • Reinforcement: Longitude Bars Plan • Reinforcement: SSR Plan • Design Status: Status Plan • Design Status: Punching Shear Status Plan

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34.8.2 Reordering report items The order of report items in the Report Contents window is the order they print in the report. You can reorder items that are within the same folder or layer by dragging them to a new position. You cannot move items outside their folder or layer. For example, you can move the Units item to a

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new location inside the Criteria folder but you cannot move it into the Layers folder. To change the location of a report item:

1 In the Report Contents Window, press down on the left

mouse button over the report item you want to move. 2 Drag the report item to its new location and release the

left mouse button. (RAM Concept does not allow you to move a report item outside of it’s folder or layer)

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35 Exporting Plans and Tables You can export any plan or text table in RAM Concept. Concept supports export of plans as .dwg or .dxf files in AutoCAD R12 through AutoCAD 2004 format. Tables export as text files, which you can open with most spreadsheet software.

To choose a text size:

1 Choose View > Appearance. 2 In the Font section of the Appearance dialog box, click

AaBbZz to select a font. The point size of text is 72 times the actual size. Thus, 9 points is one-eighth of an inch.

35.1 Exporting a plan RAM Concept exports a plan with whatever information is visible at the time. You need to open a plan and make it the active window before exporting. You make a plan the active window by clicking on it.

3 In the Select Font dialog box, choose the font size and

click OK. 4 Set the font scale to zero and click OK.

Note: Do not use Enlarge Fonts ( (

) or Shrink Fonts ) to change the text size before exporting.

To export the active plan:

1 Choose File > Export Drawing.

35.2 Exporting a table

The Export Drawing dialog box appears. 2 Choose a name and type for the AutoCAD file and click

Save. The File Units dialog box appears. 3 Select the units for the AutoCAD file and click OK.

Text tables export to tab-delimited text files that you can open with most spreadsheet software. To export a text table:

1 Open the text table you wish to export. 2 Click Export (at the top of the window). 3 Enter a name for the text file and click Save.

35.1.1 Selecting the text size The exported text size depends on the visible text size on the screen. You can change the text size to suit the export.

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36 Exporting a Database to the RAM Structural System Note: In many places in this chapter the RAM Structural System is referred to as “RSS”. RAM Concept has functions that can export reactions and geometry to the RAM Structural System.

36.1 About the export of reactions RAM Concept has a function that exports wall and column reactions to the RAM Structural System.This export capability allows RSS to use Concept's accurate load distribution to calculate wall, column and foundation gravity forces. The export capability also allows RSS to consider the effects of floor tendons on columns and walls for post-tensioned structures. This export capability only applies to elevated slab models created in RAM Concept by importing from the RAM Structural System.

Note: The RAM Structural System requires RAM Concrete to consider the exported Concept reactions. The RAM Concept force export function transfers column and wall reactions to the RAM Structural System database. The export only sets the wall and column reactions for the end of the columns and/or walls that are touching the elevated slab. Exporting of reactions does not affect the support axial force of walls and columns above the slab. The structure above the column or wall determines the axial force. RAM Concept only exports reactions from gravity loadings imported from RSS back to RSS. For example, if you add “Swimming Pool Loading” to a Concept file, the export function will not transfer reactions from that loading to RSS.

Note: RAM Concept does not export Construction Dead Loading reactions, as they would have no further use in RSS.

Note: RAM Concept never exports lateral loadings (imported from RSS or otherwise) to RSS.

36.1.1 Special handling of the Self-Dead Loading and the Balance Loading during export Concept adds the “Self-Dead Loading” reactions to the “Dead Load” reactions during export. This ensures that the RAM Concrete Analysis of the structure considers the selfweight of the slab.

Note: The RAM Structural System provides the option to have beam and slab self-weights calculated automatically, or input manually as part of the dead load case. Conversely, RAM Concept always automatically includes beam and slab self-weights in its analysis. We recommend that, when using RSS in combination with Concept, you have RSS automatically calculate the beam and slab self-weight loads. That will eliminate any confusion regarding whether self-weight loads are included in the analysis or need to be manually specified as part of the dead load case, even when some levels are designed with RSS and some levels are designed with Concept. RAM Concept does not currently export “Transfer” loading reactions to RSS. When analyzing a building with a transfer slab, RSS uses its own internal distribution of the transfer forces in the slab rather than forces from Concept's floor analysis. Concept’s exported “Direct” loading reactions will be used by RSS, if you so direct. See “Using RAM Concept reactions in RAM Concrete” on page 190 for further information. RAM Concept exports the balance loading reactions to a “hyperstatic” load case that is only visible in RAM Concrete. Generally, balance forces and hyperstatic forces are not the same, but for a support that contains no tendons, however, the balance forces are equal to the hyperstatic forces.

Note: See “Post-tensioning loadings” on page 386 for a discussion of balance and hyperstatic loadings.

36.1.2 Special handling of the Partition Loading during export Concept adds the “Partition Load” reactions to the “Live Load Unreducible” reactions during export.

Note: “Loadings” in RAM Concept are analogous to “load cases” in RSS.

36.1.3 The export of reactions process You can export reactions to RSS at any time after you perform a “Calc All” operation and you save the file.

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Chapter 36 To export to the RAM Structural System

Choose File > Export Reactions to RAM Structural System. A dialog box, as shown in Figure 36-1, opens with a list of RSS story names to which you can export reactions. Concept labels one story name as “Source Story”. This is the RSS story previously imported to create this Concept file. Concept lists other stories in the RSS file with the same floor type, and labels them “Identical Story” or “Compatible Story”. A story is compatible with, but not identical to, the source story if it has a different story height, member sizes, or (for the top story of the type) any columns above it have different orientations. Select any combination of stories, and click “OK”. RAM Concept displays a log detailing the results of the export operation when the export is completed.

you must reimport from RSS and recalculate results before exporting. If someone has made a “minor” change to the source story, Concept gives you the option of reimporting. Major changes include adding or deleting columns or walls. Changing a column size is a minor change. Concept cannot export the file if someone has added columns or walls after importing from RSS, or if any springs or rigid supports are present in the Concept model.

36.1.6 Checks performed after choosing export stories RAM Concept checks each story you choose to export against the RSS file in detail. If Concept detects any errors, you may cancel the export operation or return to the story selection window to deselect the stories with errors. If Concept issues only warnings, you may continue with the export or return to the story selection window. Concept generates warnings for any columns or walls above the Concept slab that do not have matching columns or walls above the export story selected. This typically only happens at the highest story of the floor type, where it transitions to a different floor type or the roof. Concept also generates warnings if a selected story's height is different from the source story height.

36.1.7 Using RAM Concept reactions in RAM Concrete

Figure 36-1 Export Reactions to RAM Structural System dialog box

Once you export the column and wall reactions to RSS, they become available to RAM Concrete for analysis and design purposes, but only if you inform RSS that you want to use them.

36.1.4 About export reactions access and consistency checking

To set RAM Concrete to use RAM Concept’s reactions

1 Start RAM Concrete

RAM Concept performs consistency checking before the actual export operation to ensure that it can export reactions correctly. Concept performs the checks before and after choosing the export stories.

2 Choose Criteria > Column Forces

36.1.5 Checks performed before choosing export stories

You can use this dialog to review the RSS levels that have Concept forces and the Concept file name from which you exported the forces. The “Read” column displays the date you imported each level from RSS into Concept. The “Saved” column displays the date you exported member reactions from Concept to that level. The “Source Story” column indicates the source story of the RSS file used to import data into the Concept file. If the “Source Story”, “Saved” and “Concept File” entries are empty, then you have not exported member forces to that level. If the

The first check performed is your access to the RSS file from which the RAM Concept floor was imported. The export operation can proceed only if the RSS file exists, it is not currently open in RSS and you are able to access and modify it. Concept also checks the RSS file for changes made to the source story since importation into the Concept file. If someone has made a “major” change to the source story,

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Select the button at the top to “Use RAM Concept Analysis Forces at selected levels”. Select the levels by checking the box in the “Use” column.

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Chapter 36 “Read” entry is empty, then you have never imported that level to Concept.

To export geometry to the RAM Structural System

1 Choose File > Export Geometry to RAM Structural

Note: RSS uses Concept wall reactions on all levels where

System.

Concept column reactions are used.

Note: The menu item is disabled if there is no model

Note: After exporting Concept reactions to RSS, you will

currently open.

need to perform a RAM Concrete reanalysis of the structure before designing any members or importing any member forces from RSS to Concept (such as for a mat foundation).

A file browser appears which allows the selection of an RSS file.

36.1.8 How the RAM Structural System - RAM Concept link works The key to the export of Concept's reactions to RSS are the imported walls and columns and the imported direct gravity loadings. Walls and columns that you import from RSS have special RSS identifiers “tagged” to them. These identifiers allow Concept to match its column and wall elements to the corresponding members in RSS. Concept will even allow you to move the walls and columns slightly (up to 50mm or 2").

2 Select a RSS file or enter a new filename.

If a new RSS filename is entered, a new RSS database is created with the current Concept model’s units. If the Concept model design code is ACI 318-99, ACI 318-02, ACI 318-05 or BS8110, the design code of the RSS database is set accordingly. Otherwise the database design code of the new RSS database will be the user's default design code. After a file is selected, the “Export Geometry to RAM Structural System” dialog appears, as shown in Figure 362.

Concept will not allow you to export if you add, delete, or significantly move imported columns or walls (or do not import walls and columns). Concept does this to ensure transfer of the full equilibrium gravity load between Concept and RSS.

Note: If you accidentally delete an imported support, or the supports change in RSS, you can always reimport the walls and columns. RSS tracks a fixed set of gravity loadings through the structures. These loadings are Dead Load, Live Load Reducible, Live Load Unreducible, Live Load Storage and Live Load Roof (when Concept and RAM Concrete are used the Hyperstatic loading is tracked as well). To ensure compatibility with RSS, Concept will not allow you to delete these imported gravity loadings. Concept does allow you to modify the imported RSS gravity loading and to add more gravity loadings. Concept assumes that you are fully aware that it considers only the loads that appear in the imported RSS loadings in the reactions it exports back to RSS.

36.2 About the export of geometry Column and wall geometry can be exported to a new or existing RAM Structural System database file. This geometry can only be exported to a new RSS floor type.

Figure 36-2 Export Geometry to RAM Structural System dialog box

The dialog lists the floor types present in the RSS file. 3 Enter the new floor type name in the “New Floor Type

Name” text field. A popup notifies you if the floor type name entered is already defined. The “General snapping distance” is the maximum distance structural features could be moved in order to merge closely spaced objects together. If the “Snap slab/deck edges to wall centerlines” box is checked, Concept will attempt to move slab and deck edges that are close to wall centerlines to be coincident in the exported data. The originating RAM Concept data will not be modified. This will potentially eliminate small elements in the RSS mesh and thus improve run times. If the “Export uniform thickness deck” box is checked, RAM Concept will export a single deck to RSS of a

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Chapter 36 uniform thickness designated. The concrete properties from the largest slab area in Concept are used if this option is selected.

allows models to be exported before they are meshed, so some errors are detected and arbitrarily corrected when the geometry is exported.

The “Columns (below)”, “Walls (below)”, “Beams”, and “Slabs” check boxes select whether columns, walls, beams, and slabs are exported. Concept exports only the columns and walls below the floor, because it is those elements that are associated with a floor type in RSS.

If two or more walls overlap, completely or partially, only one of the overlapping segments will be exported. If two or more columns have the same location, only one column at that location will be exported. In either case, a pop-up dialog describes the columns and wall segments that were not exported.

If you check “Start RSS after Export”, then RSS starts on the file after the geometry is exported. This has no effect if RSS is already running. 4 Click “Create New Floor Type” to export the selected

members to the new floor type.

Note: Column, wall, beam, and slab geometry can only be exported to a new RSS floor type.

36.2.1 About errors and ambiguities Errors and ambiguities in a Concept model are normally detected and corrected when the model is meshed. Concept

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If any columns or wall segments are not exported, the user should check the material properties of the elements that were exported to RSS. If the overlapping columns or walls had different properties, the user may have to reassign the desired values in RSS. The user can also mesh the model and resolve such errors within Concept before exporting. Walls defined in RSS may not intersect other walls or span columns or the ends of other walls. Each Concept wall is split into segments at each of these locations before being exported. The splitting of walls is not reported, but the effect will be seen as individual walls in RSS.

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37 Using Strip Wizard Strip Wizard is a dialog that automates the initial steps in the process of creating a model in RAM Concept. When modeling a straightforward slab or beam, you can efficiently use Strip Wizard to enter the structural data without having to draw in a plan window. With the wizard, you can enter the spans, tributaries, loads and posttensioning in the same way you would with a conventional two-dimensional program. Since entering the structural data in Strip Wizard is so quick and easy, it is particularly useful for preliminary design of slabs, beams, and joists. Strip Wizard uses the structural information you provide to build a model in a new Concept file. You can then modify the file by drawing openings, surface steps, point loads, and such using plan windows. Strip Wizard is deliberately simple, so use it to create the basic structure, and then modify the structure in plans if necessary. The authors intend that Strip Wizard be largely for assessment of two-dimensional behavior. The (automatic) design results are only for one direction (the x-axis). Since Concept is a three-dimensional program, line supports are automatically included along the edges of the model that allow deflection but no rotation. This closely simulates two-dimensional behavior.

37.1 Starting Strip Wizard When you start Strip Wizard, it prompts you to create a new RAM Concept file. This file is where the wizard generates your model once you enter all the structural data. Strip Wizard uses all the generic settings defined in the new file (such as units, materials, loadings, etc). If you want Strip Wizard to use your custom settings, create the new file from a template. For example, if you want certain concrete mixes to be available when specifying general design parameters, you should create the new file from a Concept template with these concrete mixes. After you have chosen options in the New File dialog, the Strip Wizard dialog appears. At this point, you can load previously saved Strip Wizard settings if you want (see “Loading and saving Strip Wizard settings” on page 197 for more information). To start defining your strip, proceed to the next page in the wizard by clicking Next. To start Strip Wizard:

1 Choose File > Strip Wizard. 2 Specify options in the New File dialog box and then click

OK. The Strip Wizard dialog appears.

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3 Click Next to proceed or you can load Strip Wizard

Settings (see “Loading and saving Strip Wizard settings” on page 197 for more information).

37.2 Specifying general parameters Specify the structure type, spans and concrete mixes on the General Parameters page of the Wizard. Structure Type

Decide what type of structure you want Strip Wizard to create and whether to use post-tensioning. The floor can be set up as post-tensioned or reinforced and can be one of the following systems: • Two-way slab • One-way slab • Beam • Joist Spans

Enter the number of spans for the strip (not including cantilevers). Decide if you are using start or end cantilevers. Check “Asymmetric” to allow the model to have different tributaries on either side of the columns. Concrete Mixes

Choose a concrete mix for the slabs and beams and one for the supports.

Note: The concrete mixes available are the mixes in the new file created when you started Strip Wizard. If you want to use specific mixes, use a template when creating the new file.

37.3 Entering span data The table you see on the Span Data page depends on the information you entered on the General Parameters page. The cantilevers and spans appear as rows in the table. The table columns depend on whether you are modeling a oneway or two-way system, beam system, or joist system. For this table and subsequent pages, the top data row’s name is “Typical”. Data entered here automatically copies to the rows below. You can overwrite the copied data.

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37.3.1 One-way and two-way systems

37.3.3 Joist systems

Span length, slab thickness and tributary width define these systems. They can vary span by span.

Span length, web properties (depth, width, spacing and number), slab thickness and tributary width define these systems. They can vary span by span. This system does not allow asymmetry.

Length

The span length from center to center of supports. Thickness

The slab structural depth. Start Width

The slab width at the beginning (or left hand end) of the span. For asymmetric strips, L Start Width is the left start width, and R Start Width is the right start width.

Length

The span length from center to center of supports. W Depth

The joist web structural depth (including the flange depth). W Width

The joist web width.

End Width

F Depth

The slab width at the end of the span. For asymmetric strips, L End Width is the left end width, and R End Width is the right end width.

The flange (slab) depth (thickness).

37.3.2 Beam systems

Pan Start Offset

The distance from the beginning (or left hand end) of the span to the pan (or void former).

Span length, beam depth, beam width, slab thickness and tributary width define these systems. They can vary span by span.

Pan End Offset

Length

Additional Web Properties

The span length from center to center of supports. W Depth

The distance from the end of the pan (or void former) to the end of the span.

The following properties determine the tributary width for the whole model. The width cannot vary span by span.

The beam web structural depth (including the flange depth).

Spacing

W Width

Number

The beam web width.

The center-to-center spacing of the webs.

The total number of webs.

F Depth

The flange (slab) depth (thickness).

37.4 Entering support data

Start Trib Width

The tributary (and hence slab) width at the beginning (or left hand end) of the span. For asymmetric strips, L Trib Start Width is the left tributary start width, and R Trib Start Width is the right tributary start width.

The Support Data page is for entering supports above and below. You must specify supports below but they are optional above.

End Trib Width

37.4.1 Support (above and below) properties

The tributary (and hence slab) width at the end of the span. For asymmetric strips, L Trib End Width is the left tributary end width, and R End Width is the right tributary end width.

Depth, width, height, bottom fixity and top fixity define the supports. They can vary span by span.

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Strip Wizard interprets a support with a width four or more times the depth as a wall. Otherwise, it is a column.

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37.6 Entering the loads

The support dimension parallel to the span. Width

The support dimension perpendicular to the span (enter zero for round columns). Height

The Loads page is for entering area and line loads in the zdirection for two standard loadings.

37.6.1 Load properties

The support’s height from its base to mid-depth of the floor.

Area and line loads can be input for two different loadings on each span.

Bottom Fixity

Dead Area Load

The moment connection at the base of the support.

The area load over the entire span.

Top Fixity

Dead Line Load

The moment connection between the support and the floor.

The line load from the first support center to the second support center for each span. Live Area Load

37.5 Adding drop caps and drop panels The Drop Caps and Drop Panels page is for entering drop caps and drop panels for two-way slabs. The page is not available for one-way slabs, beams or joists. Strip Wizard uses drop caps for punching shear only; it ignores them for flexural design. Some codes provide guidance on what dimensions are required to consider a thickening as a drop panel. Strip Wizard does not check such rules.

The live load over the entire span. Live Line Load

The live load from the first support center to the second support center for each span. Loadings to use

The Dead and Live are just names. You can specify the loads as belonging to any of the Standard loadings in the RAM Concept file. “Dead”

37.5.1 Drop cap and drop panel properties Thickness, width, before length and after length define the drops. They can vary span by span.

This can be any one of the standard loadings in the RAM Concept file. “Live”

It is possible to have drop caps and drop panels at the same support. The drop cap should be the thicker of the two.

This can be any one of the standard loadings in the RAM Concept file (except for that used for “Dead”).

Thickness

The total thickness (structural depth) of the drop. This is not the incremental increase in thickness.

37.7 Specifying the post-tensioning

Width

The drop dimension perpendicular to the span. Before Length

The dimension parallel to the span from the beginning of the drop to the support center. After Length

The Post-Tensioning page is only available if you checked “Post-Tensioned” in the Structure Type section of the General Parameters page. Most of the data entered on this page relates to minimum precompression, load balancing and tendon cover. Strip Wizard uses this data in conjunction with data for spans, depths and loads to generate a single profiled tendon.

The dimension parallel to the span from the support center to the end of the drop.

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37.7.1 General PT information You specify the type of tendon and information that helps to determine the number of strands.

37.8 Specifying reinforcement The Reinforcement page is for specifying reinforcement bars and general covers.

PT System

Specifies the size and type of strands for the tendon (as defined in the Materials Specification of the RAM Concept file).

37.8.1 Reinforcing bar You specify the bars from those available in the RAM Concept file.

Stressing

Specifies the stressing (jack) locations. Concept calculates tendon friction and other losses if jacks are located at one or both ends.

Top

Name of reinforcement bar used in the top face for flexural design.

Min P/A

Bottom

The minimum average precompression required for the concrete. Following the code minimum does not usually result in the most economical design.

Name of reinforcement bar used in the bottom face for flexural design. Shear

37.7.2 Balance load

Name of reinforcement bar used for one-way shear design.

Balance load refers to the amount of uplift provided by the tendons. The industry has traditionally expressed this as a percentage of gravity loads.

37.8.2 Reinforcement clear cover

Min Balance Load Percentage:

The covers are for bars and tendons. Rounding of tendon profiles could override the tendon covers.

The percentage of the specified load balanced by tendons.

Top

Balance Load Considers:

Clear cover to the top longitudinal bars and tendons.

Specifies the loadings that the balance loading is based upon. The choices are self-weight of concrete, self-weight plus “dead”, or total load.

37.7.3 Profiling These selections vary the tendon profile shape. Straight Profile Distance at Supports

The length of tendon that is horizontal at a support. The dimension is the total flat distance, not the distance each side of the support. Round Profiles to Nearest

The profile distance increment. This allows rounding of tendon high and low points to convenient values. If this value is too large it may cause cover violations.

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Bottom

Clear cover to the bottom longitudinal bars and tendons.

37.8.3 Punching shear checks You decide if Concept performs punching shear calculations. Perform punching shear checks

Checking this box instructs Concept to draw punching shear checks at each column. Cover to CGS

The distance from the top of the slab to the centroid of the top reinforcement. Usually this is the distance from the top of the slab to the bottom of the top bar. Concept subtracts this distance from the slab thickness to determine the “d” distance.

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37.9 Completing Strip Wizard The Completing Strip Wizard page is the final page in the wizard dialog. At this point, you can choose to save the information you have just entered so that you may load it into the wizard later. See “Loading and saving Strip Wizard settings” on page 197 for more information. When you click Finish on the Completing Strip Wizard page, Strip Wizard draws your model in the RAM Concept file based on the data you have provided. The leftmost support of your model is located at the origin (0,0). Open plans on the Mesh Input, Latitude Tendon, and Design Strip layers to view your model. You cannot view the finite element mesh, however, until you generate the mesh. To complete the wizard:

1 Click Finish on the Completing Strip Wizard page.

37.10 Generating the mesh and calculating results

See Chapter 18, “Generating the Mesh” and Chapter 28, “Calculating Results” for further information.

37.11 Loading and saving Strip Wizard settings The data you entered into the Strip Wizard can be saved as a Strip Wizard Settings file (with a filename extension of .cptstrip) and reloaded into the wizard later. The Strip Wizard Settings file contains only the information you entered into the wizard pages. Save your Strip Wizard Settings before you click Finish on the final page of the dialog. Loading Strip Wizard Settings just sets the values in the Strip Wizard dialog to the values stored in the Settings file. After you load your Strip Wizard Settings, you then page through the dialog as usual by clicking Next. You can change the data in the wizard to create a different strip. This does not affect the Settings file you loaded. You must save a new Strip Wizard Settings file if you want your changes to be stored for later use. To load strip wizard settings:

After completing Strip Wizard, you are ready to generate the mesh and run an analysis calculation on your model. To get the best finite element mesh you need to regenerate twice: once before, and once after, calculating.This is because calculating generates the design strips, which in turn can be used to improve the mesh the second time you generate.

1 Click Load on the Welcome to Strip Wizard page. 2 Select the Strip Wizard Settings file (with a filename

extension of .cptstrip) and click Open. To save strip wizard settings:

1 Click Save on the Completing the Strip Wizard page

(before you click Finish). 2 Enter the name of your Strip Wizard Settings file and

click Save.

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38 General Tips This chapter provides advice on learning RAM Concept and tips that are not explained elsewhere.

38.2 Walls

Note: It is strongly suggested that you refer to “Learning RAM Concept” on page 2 of Chapter 1, “Introduction” before reading this chapter.

38.2.1 Drawing connecting walls It is recommended that intersecting walls are drawn such that one wall terminates at the centerline of the other, as shown in 38-2.

38.1 Beams You should be careful when modeling beams. If you use standard finite elements then the beam’s torsional stiffness could be overestimated, which could erroneously reduce the deflection in the adjacent slabs. In Concept, there is no difference between standard slab and beam elements, and standard elements have a torsional stiffness that is proportional to their depth cubed. The actual torsional stiffness of a beam is proportional to the cube of the lesser value of depth and width. Standard elements thus overestimate the torsional stiffness of beams that are deeper than they are wide. For this reason, you should consider using the “No-torsion” behavior for beams, especially deep edge beams. See “Beam properties” on page 72 for more information.

Figure 38-2 Connecting walls

38.2.2 Walls above Walls above behave similarly to beams: they stiffen the floor. This is especially relevant in transfer floors. The floor moments DO NOT include the bending moments in the actual walls. We recommend that if you are in doubt as to the effect of walls above, do not model them.

Figure 38-1 No-torsion beam setting

Figure 38-3 Comparison of two floors identical in all respects except that one has a wall above (Two images with slab shown, two with no slab shown).

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38.3 Restraint Columns and walls restrain the floor against (posttensioning induced) axial deformations unless you model columns with rollers and walls as “slip” walls (shear wall property unchecked). It is unlikely that columns above restrain the floor so a roller above will generally be appropriate

Figure 38-4 Effect of wall modeled above: no wall (left) vs. wall above (right) - plot of slab moment about x-axis.

38.2.3 The difference between walls above and upstand beams of similar proportions

Restraint generally reduces the precompression and hence increases the service reinforcement. It usually increases strength reinforcement too.

38.4 Miscellaneous

Concept treats walls above the slab similarly to beams. Using “wall-beams” instead of just thickened slab elements has both advantages and disadvantages; overall it is not recommended to model walls above the slab as beams.

There are many tools and capabilities described in the preceding chapters that are useful but often overlooked.

Slab elements have two major advantages over wall elements (“wall-beams”):

38.4.1 Templates

Concept design strip cross sections automatically integrate the forces across slab elements. Wall-beam elements are ignored in these integrations. Also, Concept provides you many controls over how slab element results can be displayed; wall-beam elements (like wall elements) can only plot their reactions to the slab. However, as discussed in “Beams” on page 199, Concept’s standard slab elements have a torsional stiffness that is proportional to their depth cubed. This can cause a large over-estimation of the torsional stiffness for a very thick slab element if it is adjacent to relatively thin elements. “Wall-beam” elements do not have this problem. As such, walls above that are modeled as upstand beams should use the “No-torsion” beam setting discussed in “Beams” on page 199. When modeling wall-beams, Concept interprets some of the wall element parameters differently. If the wall-beam is not rotationally fixed to the slab then the wall-beam will have zero torsional stiffness. If the wall-beam is not a shear wall then it will have zero axial stiffness. The vertically compressible and rotationally fixed at far end parameters are ignored. Wall-beam elements have one advantage over slab elements. Slab elements of drastically differing thicknesses in the same structure can cause the automatic plotting controls to show (correctly) huge force variations in and adjacent to thick slab elements and almost no variation within the thin slab element areas. This does not generally happen if walls above are modeled as wall-beams.

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We have created a template (for the purpose of starting a file) that may or may not suit your needs. You can create your own template with additional plans, materials and settings that you can use when you start a new file. See “About templates” on page 6.

38.4.2 Adding plans You can add plans. See“Creating new plans” on page 11 and “Creating new result plans” on page 158.

38.4.3 Copying and moving objects Many users do not appreciate that selected objects can be copied and moved through a combination of holding down the shift key and using the move command (or similar). See “Moving, rotating, stretching, and mirroring objects” on page 19. You should also familiarize yourself with using the relative coordinates command. See “Using relative coordinates” on page 18. To copy and move an object using relative coordinates

1 With the Selection tool ( 2 Choose the Move tool (

), select the object. ).

3 Hold down the Shift key and click anywhere on the

workspace. 4 Type the letter “r” followed by the x- and y-coordinates

separated by a comma (e.g. r10, 5), and press Return.

RAM Concept

Chapter 38 This moves a copy of the selection x units to the right and y units upward.

based) moments (actual and demand), crack widths and reinforcement, to name just a few.

38.4.4 Expanding tool buttons

Some clients prefer to plot the reinforcement on new plans rather than use the template plans that show bar call-outs.

You can expand many tools to reveal additional capabilities. See “Expanding tool buttons” on page 6.

38.4.5 The Utility tool The Utility tool can save you a lot of time when you need to move and stretch many objects or control points. See “Using the Utility tool to move and stretch” on page 20.

38.4.9 Reducing the information shown on plans You can remove trivial results such as small reactions in two different ways. See “Specifying report as zero” on page 25, and “Reaction” on page 167 and Figure on page 167.

38.4.10 Load balancing 38.4.6 Left Wall and Right Wall tools The Left Wall and Right Wall tools can be very useful. See “Drawing walls” on page 66.

38.4.7 Changing multiple tendon profile points You can seek and change profile points that have the same value in one operation. See “Change profiles tool” on page 144.

38.4.8 Plotting Results

You can view the percentage of load that is balanced by the post-tensioning within design strips. See “Viewing balanced load percentages” on page 156.

38.4.11 The Auditor This can be invaluable in unlocking the “black-box” of calculations. See Chapter 31, “Using the Auditor”.

Note: Many users complain that there is too much information revealed by the auditor. You can reduce the information by auditing a rule set rather than the design summary.

Many users are unaware of the power of the plot capabilities. You can plot many results including (strip

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39 Frequently Asked Questions This chapter addresses many of the questions that we are frequently asked.

techniques are suitable for such structures. See the FAQ for “Mats (rafts)” on page 206.

It should be read in conjunction with:

Is Concept capable of running a single design strip for quick preliminary runs without modeling the whole building?

• “Learning RAM Concept”: Section 1.5 of Chapter 1 • Chapter 38, “General Tips”, and • Chapter 40, “Errors and Warnings”

Yes. See Chapter 37, “Using Strip Wizard” and Chapter 49, “Strip Wizard Tutorial”. Can I model a pour strip?

Yes, although there are limitations.

39.1 Capabilities and Modeling What can Concept design?

Elevated (suspended) concrete floors and mat foundations (rafts). They can be reinforced concrete, post-tensioned concrete or hybrid. See “Structural systems” on page 1 for more information. Is there a limit on the size of structure modeled?

The only limit is the performance of the computer hardware. The analysis run time is approximately proportional to the square of the number of nodes in the model, so large structures may take a significant amount of time to analyze. Design time is approximately proportional to the number of span segment strip cross sections. See “Decreasing calculation time” on page 154 for more information. The file size can also be limited by the amount of RAM the computer has available. Is there any restriction to the maximum thickness of slab that can be modeled?

Concept's analysis of slab elements considers shear deformation as well as bending deformation. This ensures that Concept gives reasonable results for both thin slabs and thick slabs. In general, Concept's design provisions apply the code requirements that are appropriate for slabs with typical span-to-depth ratios. If the geometry of your slab is outside the usual ranges, you may need to consider if any special design considerations are necessary. Can Concept design more than one story at a time?

Not by itself. You can use the RAM Structural System to integrate numerous floors into one large model.

1 Use the orthotropic properties for the pour strip area such

that the axial stiffness perpendicular to the strip is significantly reduced. See the discussion below Figure 17-6 on page 71 2 Terminate tendons either side of the pour strip.

Note: Modeling a pour strip in this manner does not consider the temporary situation before the strip is poured back. This could affect deflections and resultants. How can I model curved edges or walls?

Use a series of straight lines. The approximation should have negligible effect. Can Concept be used to design retaining walls by drawing the wall as a slab?

While Concept is not optimized for this use, it can perform most of the analysis and design tasks if you are very careful. Care must be used as Concept assumes that gravity loads are in the downward Z direction. You need to set all of the self-dead loading load factors to zero and create your own self-weight loadings. You probably want to apply these loads at the mid-slab depth; otherwise the eccentricity will add a self-weight moment to the slab. While Concept's design cross sections reports all of the moments and forces on the design cross section, Concept does not perform design considering all of the forces and moments. Specifically, Concept does not consider the Mz value in design, because Concept does not specify the positioning of reinforcement that is important for Mz design. Concept does not consider “P-delta” effects. What does “hybrid” mean?

Can I use Concept to design slab-on-ground?

The expression “slab-on-ground” is often used to described residential house slabs. The designer has to use engineering judgment to determine if mat analysis and design

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A hybrid floor is one that contains both PT and RC areas. Most post-tensioned floors have some RC elements such as pour strips and elevator core slabs. By selecting the appropriate design rules these regions can be designed at the same time as the PT elements. 203

Chapter 39

39.2 Files

39.3 Plans and perspectives

What is the difference between creating a mat (raft) file and an elevated slab file?

What's the difference between a plan and a layer?

There is really no difference; all files give you the same capabilities. The default files are setup differently because there are usually additional load cases and plans for a mat (lateral load cases, soil bearing plans, etc.). With some work, you could turn any elevated slab file into a mat file and vice versa. Can I save the data file with results?

This cannot be done with the current version - you need to open the file and recalculate. We expect to add this feature in a future version (but the “save with results” files will be huge).

A layer is an organizational concept. A layer is a collection of related objects and results and each object and result resides on one and only one layer. For example, all slab elements are on the Element layer. Plans, on the other hand, are a display and editing concept. Each plan is a filtered view of all of Concept’s layers. A plan can be set up to edit a particular layer, but the plan does not “own” the layer. All changes that are made to the layer using the plan will be visible in all other plans, because all plans are viewing the same set of layers. See Chapter 3, “Understanding Layers” and Chapter 4, “Using Plans and Perspectives” for more information.

Can I work from CAD drawings?

How do I delete unwanted plans?

Yes. See Chapter 13, “Using a CAD Drawing”.

1 Choose Layers > Delete.

Is it necessary to start a model with a DWG or DXF file?

No. For straightforward geometry it may be quicker to draw “from scratch”. It can be useful to specify a grid and then use snap to grid to locate columns and walls. I deleted the imported drawing – can it be brought back?

Yes. It is sometimes a good idea to delete the imported drawing as it affects the extent that Concept displays and prints. Any DWG or DXF file can be re-imported if necessary. If you moved the imported drawing or structure after the first import then the new import will not match. You can move the new drawing if necessary. Can Concept export to a drawing file to aid in drafting?

A dialog box appears. 2 Click OK to confirm the deletion. Can I view all information on one plan?

Yes, but it is generally not advised. You can turn on all objects from one layer in one operation, and then repeat for the next layer. 1 Make the plan or perspective the active window. 2 Choose View > Visible Objects (

).

3 Click on the tab for the object’s layer.

The plan or perspective’s layer is the one initially selected. 4 Check the Show All box, and click OK.


Yes. See “Exporting a plan” on page 187 of Chapter 35. How can I tell if there is an object on a layer? Can I export results?

Yes. See “Exporting a table” on page 187 of Chapter 35. Can I change the default new file settings?

Yes. See “About templates” on page 6. Can I set the default file for an RC design?

Yes. You could create a template that is suited to RC design, such as eliminating the Initial Service Load Combination and Initial Service Rule Set, and unchecking the Consider as Post-Tensioned option in the span segment properties. See “About templates” on page 6.

See “Determining which plans contain objects” on page 10 of Chapter 3, “Understanding Layers”. I have two items at the same location, how do I select just one of them?

Double click at the location and you should select just one object. Hold down shift and double click again and you select the other object. Why do I see nothing in a perspective display?

The perspective “camera” may be looking in the wrong direction. Click Zoom Extent ( Viewpoint (

204

) or Show Print

).

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Chapter 39 Why can I not see the area springs in a perspective?

Area springs can take a long time to generate in a perspective and so are not turned on in the default files. You need to turn them on with the Visible Objects dialog. What does “conflicting” mean in a Selected Items field?

This means that more than one object has been selected and they have different values for that property. For example, if you select two slab objects that have different thicknesses then the thickness field displays “conflicting”.

Without the priority system the modeling of floors would require one of two methods: • Objects for slabs of different thicknesses, beams, openings etc. could not overlap - this would be very tiresome for all but very simple floors, or • Depths would have to additive. For example, you would have to deduct slab depth from beam depth. If you had to change the slab depth then a change would be required for the beam, unless its depth changed by the same amount. Can I copy columns or walls below to the same above?

Note: In versions prior to 3.0 the field would be blank in such instances.

Yes. 1 Select all of the columns or walls you wish to copy. 2 Choose Edit > Copy (or right-click and choose Copy

39.4 Units

from the popup menu that appears). 3 Choose Edit > Paste (or right-click and choose Paste from

What units can I use?

See Chapter 7, “Choosing Units”.

the popup menu that appears). The pasted objects are the current selection. 4 Choose Edit > Selection Properties, or right-click and

Can I switch units after creating a file?

choose Selection Properties.

See “Changing the units” on page 25.

5 Change Support Set from Below to Above, and click OK.

Note: It is important that you do not abandon the process 39.5 Codes Can I change codes after creating a file?

after pasting. Otherwise, you will have two supports below at various locations, which causes calculation errors. The meshing operation produces a very irregular mesh. Is this satisfactory?

Yes. See “Code options” on page 150.

This depends upon a number of factors. See “Deciding what mesh element size to use” on page 75 and “Improving the mesh” on page 76.

39.6 Sign Conventions

Can I vary the mesh intensity at different locations?

Indirectly. See “Selectively refining the mesh” on page 76. What is the sign convention for moments shears and reactions?

See “Selecting sign convention” on page 27 and “About plot sign convention” on page 28.

What value should I use for the area springs Z force constant?

The geotechnical engineer commonly provides a value called the “subgrade modulus” or “modulus of subgrade reaction”.

Can I change the sign convention?

Yes. See “Changing the sign convention” on page 28.

39.7 Structure

As a guide only: realistic values vary from 100 pci (approx. 25 MN/m3) for soft clay to 750 pci (approx. 200 MN/m3) for very dense gravel.

39.7.2 Element layer How can I view the slab without the mesh?

39.7.1 Mesh Input layer

Choose Layers > Element > Slab Summary Plan

Why is it necessary to have priorities?

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Chapter 39 What is the difference between beam and slab elements?

There is no difference unless you modify their behavior. See discussion of behavior in “Slab area properties” on page 70 and “Beam properties” on page 72.

39.7.5 Mats (rafts) How do I design a mat foundation?

The Chapter 48, “Mat Foundation Tutorial” introduces the concepts for mat design.

How many nodes or elements are allowed?

There is no limit, other than the limitations of your computer.

Does Concept ignore soil tension?

You can reduce the tension by iteration. The tension gets closer to zero with an increase in the number of iterations.

How many elements should I use per span or panel?

This cannot be answered directly as it depends upon the structure and loads. See “Deciding what mesh element size to use” on page 75.

39.7.3 Columns Do columns restrain the slab?

Depending upon the defined fixity, columns can provide rotational and lateral restraint. If the far end of a column is defined as a “roller” support (or both ends of the column are pinned) then the column does not provide any lateral restraint to the slab. Do columns above the slab support the slab vertically?

No. Columns only restrain the slab rotationally and laterally.

39.7.4 Walls Do walls restrain the slab laterally?

Yes, if you select Shear Wall as a property. If the Shear Wall is unchecked then the slab is allowed to slip freely over the top of the wall. The walls rotational stiffness is independent of the Shear Wall setting; use the fixity settings to control the walls rotational stiffness about its longitudinal axis.

See “Zero tension iteration options” on page 150 for more information. Does Concept design for soil heave?

Not directly. You could draw spring supports that approximate varying soil support. Do I need to draw the columns above in a mat foundation model?

No, but it is a good idea. It ensures a node is placed at that location where there is likely to be a heavy point load. Can Concept design for pile supports?

Yes. Use either (flexible) columns under, or point springs. Skin friction is not considered. Can Concept design for pile and mat (raft) action together?

Yes, but the results could be very susceptible to variations in geotechnical parameters. For example, if the soil’s stiffness is overestimated, the actual pile reactions could be significantly underestimated. Use caution. Does the area spring support have to match the mesh?

No. Can the soil stiffness vary?

Yes. You can vary the stiffness in two directions. See “Area spring properties” on page 69.

What is the effect of specifying walls above?

Where do I select the allowable soil bearing pressure?

Wall elements can be used to model the stiffness and spanning ability of walls connected to the slab. You should exercise caution when using them. See “Walls above” on page 199.

This is not an input parameter. You need to look at soil bearing pressure plans (which have a maxima / minima legend) to assess the maximum pressures. Also, see the FAQ on “Soil bearing” on page 216 (in the results section).

Do walls above the slab support the slab vertically?

Does Concept iterate to remove tension in a point or line spring?

No, they act like beams. See “Walls above” on page 199.

No, only for area springs.

Do walls above the slab provide rotational restraint?

There is no restraint at the far end of a wall above. (Even if “Rotationally Fixed at Far End” is checked, it is ignored).

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39.8 Tendons Why are some tendons shown at the wrong elevation in the tendon perspective?

The soffit elevation at each profile point is determined during the Analyze All and Calculate All commands. If one of these commands is not performed since the drawing (or moving, etc.) of a tendon, or since a change in the mesh, the tendon elevations in perspectives are not accurate. The same is true for elevations optionally shown as text on the plans. It is quicker to analyze (but not using “Calculate All”) with Process > Analyze All. This avoids processing the design calculations. What do “Latitude” and “Longitude” Tendons mean?

In the USA, Britain and other countries it is typical practice to place all the tendons in one direction in a concentrated band over column lines. If the designer is using another practice then we recommend that you still use the Latitude and Longitude tendon layers because it makes editing the PT easier. i.e. Put the tendons in the X direction on one layer and the Y tendons on the other. Latitude and Longitude are just layer names.

Does it matter how I draw “half” tendons?

Yes. The inflection point is measured from the first point clicked and the profiles are specified in the order of the points clicked. To be compatible with the tendons created using the Full Span Tendon tool, we strongly recommend that you always start at the high point. Can I terminate some strands past a column?

This can be done with one of two methods. 1 The tendon can be “forked” such that the number of

strands decreases. As shown in Figure 39-1, if the transition is from 15S (15 strands) to 10S (because an adjacent span does not require that many strands) then terminate 5S using a half span tendon. It is common to terminate strands at quarter span and at the slab centroid.

Note: You should only use this method for tendons with no jacks attached. This is because a jack attached to tendons of different lengths has inaccurate seating (wedge draw-in) loss calculations.

Figure 39-1 Termination of strands (no jacks)

Do I have to draw the tendons for a post-tensioned slab?

Yes. It is not difficult, and encourages you to address detailing issues before they become field problems. How do I draw tendons?

2 The second method can be used when jacks are modeled.

If the total number of strands is 15S then one tendon with 10S needs to be continuous with an additional tendon with 5S alongside. It is common to terminate tendons at quarter span and at the slab centroid.

See “About drawing individual tendons” on page 141, “Drawing single tendons” on page 141 and “Drawing multiple tendons” on page 142. You double click the tendon tool to change default tendon properties and then draw tendons span by span, or panel by panel. You can select a specific tendon segment and right-click to change that segment’s properties. You can seek and change profile points that have the same value in one operation. See “Change profiles tool” on page 144.

Figure 39-2 Termination of strands / tendons (jacked). Plan alignment of tendons is subjective. Does Concept check to make sure the number of strands in connected tendon segments is consistent?

Yes. See section 40.3.3 of Chapter 40, “Errors and Warnings”.

Can I harp tendons?

How does Concept calculate friction losses?

Yes. Any tendon segment can be declared to be harped. The “half-span” tendon tool is useful for any harp point (or any low point) that is not at mid-span. Multiple harp points can be located in any span by using multiple tendon segments.

Concept only calculates friction losses if jacks are specified.

RAM Concept

Concept performs friction loss calculations considering the (elevation view) curvature of the tendons, the (plan view) horizontal kinks in the tendon and the jacking and friction parameters. The stress in the tendon is assumed to vary linearly along each tendon segment. 207

Chapter 39 Along each tendon the following formula used is: P2 = P1 * exp-(mu * theta + k * L)

Does Concept calculate elongations (extensions)?

Yes, if jacks are specified. Use the Visible Objects dialog to view Jack Elongation on a plan.

where •

P1 is the known stress at one end of a tendon segment

• P2 is the unknown stress at the other end of a tendon segment

Do the elongations (extensions) include the effect of the seating distance (wedge draw-in)?

Yes. The elongation reported includes the deduction of the seating distance.

• mu is the angular friction coefficient (in units of 1/radians)

Where are tendon profiles measured from?

• theta is the total angular change along the tendon segment

See discussion on Profile in “Choose the Banded Tendon Polyline tool ().” on page 137.

•

k is the wobble coefficient (in units of 1/length)

•

L is the tendon segment length

Note: Some engineering communities (Australia in particular) use a definition of wobble coefficient that is the accidental angular change per unit length. These communities can calculate the wobble coefficient that Concept uses, k, with the following relationship: k = AngularWobbleCoefficient * mu. At the joints between tendon segments Concept uses the following formula: P4 = P3 * exp-(mu * angle)

P4 is the unknown stress in the next tendon segment

• P3 is the known stress in the previous tendon segment (or the jack stress) •

This is a matter of engineering judgment. There is certainly no need to lay out individual strands and it is usually satisfactory to group strands in larger tendon groups than that installed in the field. Keep in mind that design strip cross sections consider only the tendons that they cut through to calculate strength etc. There could be instances where you want to model banded tendons in multiple groups (if the band is very wide). I have laid out the longitude tendons but want to change the number of strands per group. Do I have to lay them out again?

where •

It's much easier to take all the strands and put them into one tendon bundle instead of having to lay them all out. Is there much difference to the model whether you distribute tendons over the tributary or not?

mu is the same angular friction coefficient as above

• angle is the total angle change at the tendon profile point (includes both horizontal and vertical kinks)

No. The number of strands in a tendon does not have to be an integer, so you can change it by any increment. Can I determine the force in a tendon?

Yes. Use the Visible Objects dialog to view the Tendon Forces on a plan.

Concept incorporates seating loss (wedge draw-in loss) into the losses using the standard strain integration formulation. The equations above are still used, but the known and unknown values are swapped. Concept adjusts the tendon stresses iteratively until the integration of the strain change in the tendon equals the specified anchorage seat loss.

Does Concept check for tendons being outside of the concrete?

Long term losses are input by the user as a jack parameter.

No. The load balance tool is available to help you calculate low points, but is not mandatory.

See “About jacks” and “Jack properties” on page 144 for more information.

Yes. See discussion in sections 40.3.4 and 40.3.5 of Chapter 40, “Errors and Warnings”. Do I need to do a load balancing calculation with all the tendons?

The load balancing percentage shown on the design strips plan does not make sense. How is this calculated?

Do I have to specify jacks?

No. Concept uses the relevant value of fse (specified in the Materials criteria page) as the effective stress for any tendon without a jack.

Concept’s balanced load percentage calculation assumes that what you define as a span, actually behaves like a span. Sometimes this is not the case. To calculate the effective dead load applied, Concept uses: D = 8 Md / L 2

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Chapter 39 Where:

Example 39-1 Lateral SE

D is the dead load to be calculated

Consider the structure with two elevated floors shown in Figure 39-3. Each level is 3m high and the structure is 10m wide.

Md is the total dead load span moment (calculated from the moments at the first, middle and last cross sections of the span) L is the span length (as determined from the span segments, support conditions, etc.) The calculation for the effective balance load is similar: B = 8 Mb / L 2 The percentage balanced is 100 . (-B/D) If, for example, the dead load moments at the start, middle and end cross sections are not negative, positive and negative then percentage balance calculation will not be useful. This does not mean your strips are wrong, but it might mean that your tendon layout is not doing what you think it is doing. Look at the DL (or DL + LL) deflections (without balance loading) and try to get a better feeling for how the structure is working and from there determine where to add and remove tendons.

39.9 Loadings Is pattern loading possible?

Figure 39-3 Example with two elevated floors

Assume the following: • a frame analysis has been performed on the building for this 100kN loading and the column forces are known • a very simple distribution of forces (reasonable for beams much stiffer than columns) The forces on the top level slab (including column reactions) are:

Yes. See Chapter 21, “Creating Pattern Loading”. For an irregular structure it is very time consuming to draw the area loads to match the structure. Is there a faster way?

It is not necessary for area loads to match the structure. Area loads can overlap each other and they can “overhang” the floor. This is shown in the PT tutorial. Figure 39-4 Forces on top level slab Are area loads additive or does the maximum govern?

Loads are additive.

Fx0 = 100kN

How do Lateral Self Equilibrium loadings work?

Fx1 = -50kN

Fx2 = -50kN

Fz1 = -15kN

Fz2 = 15kN

My1 = 75kN-m

My2 = 75kN-m

Refer to “Self-equilibrium analysis” on page 387 of Chapter 50, “Analysis Notes”. However, the best way to understand Lateral SE could be this simple example:

RAM Concept

These forces are in equilibrium and are applied directly to the slab in a lateral SE loading. Concept then calculates the correct forces in the slab, design strips and punching checks.

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Chapter 39 For the intermediate level there are more forces to consider (all of these are from the frame analysis). The forces that the columns apply to the slab are:

This situation is very much like shrinkage/swelling. Expansion / swelling generally causes compressive stresses in the slab which enhance its strength (they act similar to prestressing) and can usually be ignored. Shrinkage/contraction generally causes tension stresses which are more troublesome. Many designers take the approach that shrinkage is primarily a deformation compatibility problem and as soon as cracks form in the slab (or supports), most of the shrinkage forces are relieved. These designers ensure that there is enough reinforcement to control cracking and take measures to reduce the shrinkage, but generally do not design for the shrinkage forces.

Figure 39-5 Forces on intermediate level slab

Fx3 = 50kN

Fx4 = -50kN

Fx5 = 50kN

Fx6 = -50kN

Fz3 = 15kN

Fz4 = -45kN

Fz5 = -15kN

Fz6 = 45kN

My3 = 75kN-m

My4 = 75kN-m

My5 = 75kN-m

My6 = 75kN-m

These forces are in equilibrium and are applied directly to the slab in a lateral SE loading. Since the “3” and “4” forces occur at the same location, they can be added together and applied as a single load (same for “5” and “6”). Concept then calculates the correct forces in the slab, design strips and punching checks.

Note: There is one simplification - if you do not care about diaphragm forces, then you can ignore all the Fx and Fy forces. This assumes that the Fx and Fy forces act at the center of your slab and that the centroid elevation of your slab is constant. When these two assumptions are not true, the effects of these forces are typically still not large, but you may need to use some judgment before you ignore them. Can I input thermal loads into Concept?

Rationally considering thermal loads and stresses is difficult. Concept does not make it significantly easier. The most important thing to remember is that thermal loads cause deformations, not forces. It is the restraint of the deformations that induce forces into the slab. If there is no temperature gradient through the slab (and the slab is flat), then the thermal expansion/contraction will not cause any out-of-plane deformation, but will cause in plane stresses if the temperature changes are not uniform across the slab, or if the supports restrain the slab from lateral movement. 210

For temperature gradients across the slab, transverse deformations (like slab curling) happen. Cracking will also partially relieve these stresses, but the situation is not as simple as in-plane temperature changes. Concept does offer a means to model the thermal forces, but it takes some work, and does not consider the reduction in stresses that happens after cracking. Here is the approach: • Add a Thermal loading, set its Analysis type to Lateral SE (the loading will be a self-equilibrium loading, but won’t be “lateral”). Leave the loading type as “Other”. • Set the load combo load factors for the Thermal Loading. • Apply the thermal restraint reactions to the Thermal Loading, but don’t apply any load that simulate the thermal deformations themselves. This set of reactions is in self-equilibrium (more on how to calculate these below). This approach will appropriately design for the thermal (restraint) forces in the slab, but will not appropriately consider the thermal deformations in the deflection predictions. There are two methods to calculate the thermal restraint reactions: get them from another analysis or iteratively determine them in Concept. You may be able to model the thermal loads in SAP. If so, you can just apply the reactions to the slab from the walls and columns as the thermal loads. The reactions will be a self-equilibrium set of forces. To determine the reactions loads iteratively in Concept: • Apply loads to the Thermal Loading that create the thermal strains assuming the slab is free to deform. These loads should be a self-equilibrium set of forces. • Analyze the slab (and see that the loads cause the slab to separate from the walls and columns). • Change the Thermal Loading analysis type to Normal (temporarily) RAM Concept

Chapter 39 • Analyze the slab (and see that the reactions keep the slab attached to the supports).

39.12 Results

• Apply the support reactions as loads (they will be a selfequilibrium set). Ensure that the load elevations are set correctly.

39.12.1 Reactions

• Change the Thermal Loading analysis type back to Lateral SE.

Does Concept include the weight of columns and walls in self weight calculations?

• Analyze the slab (and see that the “reaction” loads keep that slab attached to the supports).

Concept never includes the weight of supports below.

• Remove the original loads that caused the thermal strains. The remaining loads are still a self-equilibrium set - and are the loads for which to design.

You decide if the weight of supports above is included. This is a choice you can make in the Calculation Options. Can I choose which column and wall reactions are shown?

Yes - you can change what Concept plots. See “Reaction” on page 167 and Figure on page 167.

39.10 Analysis Should I use “Auto-stabilize structure in X and Y directions” in the Calc Options?

This is only necessary if your structure has no lateral stability, such as an elevated floor with columns on rollers, or a mat (raft) with no X or Y direction springs. Autostabilize does not work if there are lateral loads.

39.11 Design Issues What support width is used for round columns?

If there are columns (and or walls) above and below an elevated slab you can select (through the Plot dialog) which reactions are shown. The choices are • the total reaction on the slab (below and above) • the reaction below • the reaction above The reaction plans show many small values for Fx and Fy which makes the plan difficult to read. Can I look at just Fz?

You can control this in two ways. The simplest way is to turn off Fx and Fy with the plot settings. See “Changing which results plot” on page 158.

Concept calculates the support width for an equivalent (in area) square column.

Alternatively, you can filter out small reactions and moments through the Units window. See “Specifying report as zero” on page 25.

What is the relevance of the Include Detailed Section Analysis box in Criteria > Design Rules?

The wall reactions are shown per straight section of wall. Can I see the reaction per wall element?

That box instructs Concept to do a cracked section analysis even if one is not required for the code criteria.

No. This is not available because there would be too much information shown.

The only reason to check the box is if you want to see cracked section stresses even when they are not used for code checking / design.

I have modeled columns at the end of walls. The column reactions are huge and the wall reaction is negative. Is this realistic?

The only reason not to check the box is that cracked section analyses can be slow. See “Detailed Section Analysis” on page 154 of Chapter 28, “Calculating Results”.

The huge result is mathematically correct but may not be realistic. Try modeling the column and walls in question as vertically compressible. This may reduce the column reaction to a more realistic value. How can I determine the reaction at the end of a wall?

Reactions are reported for continuous walls, so if you need discrete reactions leave a gap in the wall or specify a column at the end of a wall.

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39.12.2 Plots Why is there moment shown at a free edge about an axis parallel to the edge?

• For example, for the service load combination, the load factor on live load could be 1.0 and the alternate envelope factor could be 0.0. This would produce differing maximum and minimum values. • Pattern loadings • More than one load combination using the same rule set. The default plot shows the maximum and minimum deflections. You could choose to show just the maximum values via the plot dialog, but remember that the absolute of minimum could be more than the maximum. It would be possible that minimum governs if you have upward deflection.

Note: This also applies for plots of demand for resultants such as moment or shear. Figure 39-6 Plan of moment about Y-Y axis at opening. The circled moment is displayed as non-zero.

39.12.3 Torsion The plotted moments are smoothed curves of the element center moments. A slab element at a free edge may have a small moment at it center. The values shown between element centers are interpolated, but since there is no element outside the edge, there is no way for that value to ever reach zero. For better visual results (values closer to zero at the edge), you should use smaller elements at the edge. The distance from the edge to the edge element center is the most important parameter. I have a pinned column at the edge of the slab. Why is there moment shown at the edge about an axis parallel to the edge?

I have set the Behavior of a beam to “No-torsion”. Why is there still torsion in the beam?

When you set your beams to have “no torsion”, you are really setting them to have no “twist” (Mxy). Twist is only one component of torsion. Torsion is a moment that in Concept is measured about the centroid point of the cross section. The z-coordinate of this centroid is the mathematical centroid elevation of the cross section, the x- and y- coordinates of the centroid are the centre of the “core” portion of the centroid. The vertical shear in the cross section will create torsion unless it is centred upon the centroid. In an edge beam, the vertical shear at the ends must be centered on the column, or there MUST be torsion to maintain equilibrium.

39.12.4 Envelopes What is the significance of Envelopes in the Audit?

An envelope is a resultant (set of forces) in which one of the force values is a maximum or minimum for an item (such as a cross section) under consideration. All of the force values within a single envelope occur simultaneously. The explanation is the same as the preceding question.

Audit envelopes are created by the following process:

Why are there two lines for deflection in the strip plots?

• for each rule set, 6 envelopes are added to a list (Max M, Min M, Max V, Min V, Max P, Min P)

The two plots for maximum and minimum differ if you have one of the following conditions:

• duplicates are removed (if Max M and Max V are identical, one of them will be removed)

• Alternate envelope factors that are not the same as the load factors (see “About alternate envelope factors” on page 41 of Chapter 11, “Specifying Load Combinations”).

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• torsion conversion is performed (this can modify the torsion values, it can also create additional envelopes)

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Chapter 39 The result is a list of envelopes (possibly just one, but also possibly up to 12).

Note: Some “torsion conversions” (such as modifying the bending moment due to the torsion) can double the number of envelopes in effect.

2 The depth of the span segment strip cross section

contributes to a large amount of minimum reinforcement. This may be because the cross section depth is based upon a thickened area. 3 The bonded tendons are not in the tensile zone. Why are the reinforcement results on the Design Status layer in different colors?

39.12.5 Reinforcement Can I determine the reinforcement spacing?

The default Appearance scheme uses different colors for “Failed Span Design” and “OK Span Design”.

Yes. 1 Choose the appropriate reinforcement plan. 2 Choose View > Visible Objects (

).

3 Check Bar Spacings under the Span Designs or Section

Designs columns.

Note: Plotted reinforcement quantities cannot show bar spacing.

39.12.6 AS3600 specific reinforcement questions I am getting more reinforcement than expected. Why is this?

The default setting for design strip Environment is Normal. Changing to Protected can reduce the amount of reinforcement. See “Section 9.4.3.2 Shrinkage and Temperature” on page 536 for further clarification.

Why is the Minimum Reinforcing required placed on the wrong slab face?

This sometimes happens for an ACI318 or BS8110 / TR43 design. Concept locates the minimum reinforcing required by certain design criteria on the tension face of the slab (or the face with the least amount of compression); this normally works well for both elevated slabs and mat foundations. However, in certain cases the moment at a design strip cross section is of the opposite sign of what would be expected given the location. For an elevated slab this can lead to reinforcing at columns being at the bottom of the slab and reinforcing at mid-span being at the top of the slab. For example, for ACI318 or TR43 if there is no tension at a slab location under service conditions, then Concept places the minimum support rebar on the face with the least amount of compression. This could be the bottom face at a column. You can overrule this by choosing Elevated Slab for the design strip property CS Min. Reinforcement Location. See “Span segment properties”, which starts on page 96. The description of CS Min. Reinforcement Location follows Figure 22-7. I am getting more reinforcement than expected. Why is this?

This can be for a number of reasons. The common ones are:

39.12.7 BS8110 / TR43 specific reinforcement questions Why is there bottom steel at the column?

There are a couple of possibilities. 1 See “Why is the Minimum Reinforcing required placed

on the wrong slab face?” on page 213. 2 TR43 (1st Edition) clause 6.10.5 states that “additional

un-tensioned reinforcement shall be designed to cater for the full tension force generated by the assumed flexural tensile stresses in the concrete” for “Support zones in all flat slabs”. The note under TR43 table 2 states that “the support zone shall be considered as any part of the span under consideration within 0.2 x L of the support, where L is the effective span”. This often means that there is tension on the bottom face near the “edge” of the support zone, beyond contraflexure. Per 6.10.5, Concept adds reinforcement to the bottom face in such instances.

Note: Concept might draw reinforcement bars to the column, but a plot could reveal that is only required over a limited zone.

Note: Using column and middle strips for a TR43 PT flat plate tends to increase the likelihood of this situation.

1 The floor is post-tensioned and yet you have not checked

the Consider as Post-Tensioned option. Concept is ignoring the tendons. See the description in “Span segment properties” on page 96.

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Chapter 39 Why is there mild service reinforcement near midspan of a bonded post-tensioned flat plate?

When designing to TR43 (BS8110) with bonded tendons, many designers are surprised to see bottom service reinforcement. TR43 (1st Edition) clause 6.10.5 states that “.... additional un-tensioned reinforcement shall be designed to cater for the full tension force generated by the assumed flexural tensile stresses in the concrete for .... span zones in flat slabs using unbonded tendons where the tensile stress

Figure 39-9 Example 2: ineffective tendons in tension zone: (i) small number of strands (ii) near neutral axis

39.12.8 Punching Shear

exceeds 0.15 f cu .” How does Concept check punching shear?

Many designers consider that they do not have to provide un-tensioned reinforcement if they use bonded tendons. However, what they miss is that the reinforcement “shall be placed in the tensile zone, as near as practicable to the outer fibre”. Concept examines the location of the bonded tendons and determines if it is effective. See “Calculation of Supplemental Reinforcement Per TR 43, 6.10.5” on page 571 for further explanation. The following figures show where bonded tendons would not provide serviceability crack control.

See Chapter 66, “Punching Shear Design Notes”. Does Concept check punching shear at the ends of the walls?

No. What is the stress ratio?

The ratio of maximum stress to allowable stress. Does Concept use redistributed moments in punching shear checks?

No. The biaxial moments are factored elastic moments. Is the design insufficient if the stress ratio exceeds 1.0?

The punching shear at such a column is either: 1 sufficient if provided with design punching shear

reinforcement, or 2 insufficient (reinforcement cannot solve the problem and

the concrete form needs revision). Why is there a punching failure at a beam? I thought that punching shear failures occur only in flat slabs. Figure 39-7 Assumed stress distribution

The code provides formula for calculating punching shear. This does not apply any logic as to whether a punching failure can occur. Concept is only doing a punching check at a column supporting a beam because the user drew a punching check there. You should decide the nature of the potential failure mechanism and thus whether punching check is appropriate.

Figure 39-8 Example 1: tendons in compression zone (not effective)

Shallow beams could certainly have punching failure. Deep beams are less likely to have punching failure, and one-way shear failure would be the likely failure mechanism. For example, column A in Figures 39-10 and 39-11 is satisfactory for one-way shear (with reinforcement in the beam) but the code equation determines that there is a punching failure. You need to decide if this is appropriate.

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Chapter 39 It would be possible, but very rare, for a punching failure at column B since it is satisfactory for one-way shear in the beam (with reinforcement).

39.12.9 Shear reinforcement (one-way) Why does my flat slab (or flat plate) model have one-way shear reinforcement results? I would expect punching shear to govern, not one-way shear. [Similarly: Why does my flat slab (or flat plate) model have oneway shear failures?]

When engineers design flat slabs by hand, they often IGNORE the one-way checks. They decide that punching is all that is appropriate. (This is often decided without much consideration – it just “seems right”).

Figure 39-10 Mixed form: flat slab with column capitals and beams

Concept does not make this decision, as nowhere does the code advise to ignore one-way shear checks in a flat slab or flat plate. Nonetheless - you should decide what the possible failure mechanism is and so what is appropriate. It may, or may not, be appropriate to ignore the one-way shear results. For example, columns C in Figures 39-10 and 39-11 are satisfactory for punching shear (without reinforcement) but the mathematics of the code requires one-way shear reinforcement. It is up to you to decide if this is appropriate.

Note: In fact, ACI 318-02 rule 11.12.1.1 specifically requires a one-way shear check in flat plates. The results have a lot more shear reinforcement than expected.

This is likely to be a shear core issue. Refer to “About shear core” on page 105 and “Shear core in slabs” on page 106 of Chapter 22, “Defining Design Strips”. For a post-tensioned beam, the reason could be that Concept is deducting a fraction of the (bonded) duct from the web width per the appropriate code rules. Concept calculates the number of duct by dividing the Strands per tendon by the Max strands per duct (as specified in the Materials) and rounding up to the next integer. Refer to the following sections for an explanation of Concept’s shear web calculation: • For AS 3600, “Section 8.2 Shear Design” on page 533 Figure 39-11 Shear results

• For BS 8110, “Section 3.4.5 Design shear resistance of beams” on page 566. • For IS 456, “Section 22.4 Design shear resistance of beams” on page 593. • For EC2, “Section 6.2 Design shear resistance” on page 614. • For CSA A23.3, “Section 11.3 Shear Resistance of Beams” on page 635

Note: There is no ACI318 rule concerning deduction of ducts.

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Chapter 39 What does this audit text mean: “Depth “d” is zero - replacing with “column” effective depth. Depth is still zero - giving up.”?

39.12.11 Soil bearing

The is likely a combination of two things:

There are many soil bearing pressure plans. Is there a summary?

• there is net compression force and a small moment, and as such the bending designer does not provide any reinforcement

The Soil Bearing Design rule set envelopes the maximum and minimum bearing pressures for all load combinations.

• the minimum designer has been turned off

Choose Layers > Rule Set Designs > Soil Bearing Design > Max Soil Bearing Pressure Plan

If this is the case, you should consider turning the minimum designer back on.

39.12.10 Deflection Is cracking taken into account for deflection?

Not all deflection results consider creep and cracking. It is very important that you understand which ones do and which do not. See Chapter 65, “Load History Deflections”. Does Concept warn if deflection is too high?

No. Allowable deflection is a very subjective issue and Concept does not warn if deflections exceed conventional limits.

Note: Concept does display a warning when deflections

39.13 Performance What are the graphics cards requirements?

It is recommended that you use a graphics card supported by DirectX 9.0. See the graphics card manufacturer for latest information on DirectX drivers. If no graphics card supported by DirectX can be found, Concept attempts to use software emulation under Windows XP SP2 ,Vista and Windows 7. At least 128 MB of video RAM is recommended, but 256 MB is more desirable. For optimal performance, graphics display color depth should be set to 24-bit or higher. When using a color depth setting of 16-bit, some inconsistencies will be noted.

are so large that the analysis itself may no longer be valid. This typically happens for structures that are unstable or nearly unstable. Often the instability is related to unrestrained lateral displacements.

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40 Errors and Warnings RAM Concept has many error and warning messages that can be triggered during modeling and analysis. Some messages are self-explanatory and do not warrant further explanation. This chapter explains some of the more complicated warning and error messages that commonly arise. Most errors and warnings advise of a coordinate (x,y) or an object number. Concept shows coordinates at the bottom of the workspace (see Figure 2-1 on page 5). You can turn on object numbers with the Visible Objects (

3 Check the Priorities boxes under Beams and Slab Areas,

then click OK. 4 Use the coordinates in the error dialog box to find the

location of the problem, and revise the assigned priorities. Usually this requires making sure that the thickest slab or beam have the higher priority (the lowest priority is 1).

Note: The highest priority is not always assigned to the thickest element. For example, where a standard slab area overlaps a depressed slab area.

) dialog box.

40.1.2 Line is too short at (x,y) To show an object number:

1 Choose Layers > Plan. 2 Choose View > Visible Objects (

).


Concept has a minimum element size of 50 mm (approximately 2 inches). This is effectively a “snap” distance. When an object such as a slab area has two nodes closer than this distance the line between them is too short. In such cases, Concept merges the two nodes together and reports the coordinates of this occurrence in the dialog box.

3 Check the Numbers box under the appropriate object’s

column, then click OK.

You can view the resulting elements and nodes in the element standard plan.

40.1 Meshing

40.1.3 Feature eliminated at (x,y) This warning is a result of one of two things:

Concept can generate several different errors and warnings for meshing. A general description of meshing limitations is in “Limitations of the automatic meshing” on page 75. It is strongly advised that you heed such errors and warnings and fix the problems. Otherwise, Concept generates the mesh everytime you do a “Calc All”.

Note: Nearly all meshing problems are due to the user’s failure to use snapping properly.

40.1.1 Two or more slab areas or beams with the same priority overlap at (x,y) Overlapping slabs and beams should have different priorities. This is explained in “The priority method” on page 70. The error is generated when two or more overlapping slab or beam objects have the same priority.

1 Choose Layers > Mesh Input Layer > Standard Plan.

).


RAM Concept

• Failure to use snapping, causing small overlaps.

40.1.4 Recursion too deep If the mesh ends up with 3 nodes at a tight angle, Concept attempts to use recursion numerous times to adjust the nodes and make the minimum angle larger. In such a case, the standard number of recursions did not solve the tight angle, so the warning message reported that the recursion was too “deep”. This does not generally cause a problem, although it is indicative that there is a “pointy” element which can affect the contour plots. Generally it is best to avoid this situation. See “Feature eliminated at (x,y)”.

Note: You should investigate the meshing / modeling of the problem area to ensure that Concept's elements are reasonable for the area.

To fix this error:


• A feature is too small to model (for example, a 1" (25mm) wide slab area), or

Note: This error is usually caused by a failure to use snapping while drawing: two lines that are supposed to be in the same place are instead slightly off parallel and intersect.

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40.1.5 An error has been found. Two column elements below the slab are at the same location. Delete column element #a or #b.

40.2.2 An error has occurred while assembling the load vector. A line load is not totally on the slab. Revise line load #a.

This error occurs when you inadvertently draw a column at the same location twice, or copy and paste a column and do not change the Support Set (above or below).

A line load that is not completely on finite elements generates this error. There may be times you ignore the error, such as when a line load crosses an opening. Concept ignores the part of the load crossing the opening.

To fix this error:

1 Choose Layers > Mesh Input Layer > Standard Plan. 2 Choose View > Visible Objects (

).

3 Check the Column numbers box.

Note: You should closely investigate such an error. A line load may appear to be on a slab edge, but actually be outside it. If you believe you have a line load across an opening and ignore the error, you may miss a real problem.

4 Place the cursor at the appropriate column, double click

and delete.

40.3 Tendons 40.1.6 An error has been found. A column element below the slab is not attached to the slab. Revise column element #a (below the slab)

40.3.1 Tendon # has a radius (a) that is less than the minimum allowable (b).

This error occurs when a column is outside the slab boundary (or within an opening). To fix the problem you should move the column or edit the slab such that the column is within the slab boundary.

Parabolic tendons with a large drape relative to their length have a small radius. A warning is triggered when the tendon segment radius is less than the minimum radius for that tendon system.

40.1.7 It is good modeling practice to connect wall centerlines. Click on the Fix button to move wall endpoints to a nearby centerline This warning occurs when the end of a wall is drawn within close proximity, but not coincident with another wall centerline. Walls should be modeled this way in order to create the best analytical finite element mesh. The dialog box offers an automatic fix (Click on the Fix button). If you click this button, Concept moves the wall endpoint to the centerline of the nearby wall.

A tendon’s minimum (vertical) radius is specified in the Materials section. Concept does not check horizontal radii as tendon segments are straight in plan. The radii shown are suggestions based on industry standards. You can change them based on advice from prestress companies.

Note: The warning can be indicative of an overbalanced condition (too much uplift) for parabolic tendons. To remove the warning you can adjust the tendon profile or change the minimum radius in the Material section. To edit the minimum radius:

1 Choose Criteria > Materials. 2 Edit the minimum radius for the PT system.

40.2 Loads 40.3.2 Cannot auto-position profile point at (x,y) due to profile point value 40.2.1 An error has occurred while assembling the load vector. A point load is not on the slab. Revise point load #a. A point load that is not on a finite element is considered an error. Apart from generating the error, Concept essentially ignores the load.

This warning occurs when both of the following are true for two tendon segments that share a Profile Point 2: 1 The tendon segments have the Position Profile Point 2 for

equal balance loads option checked, and 2 One, and only one, of the tendon segments is flat (that is, the

values for Profile Point 1 and Profile Point 2 produce a flat tendon segment: this usually occurs when the two values are equal).

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Chapter 40 The Position Profile Point 2 for equal balance loads option is intended to move the plan position of Profile Point 2 so that the uplift is equal for both tendon segments. This is not possible when one tendon segment is flat (zero drape) as there is no uplift in that tendon segment.

40.3.3 An error has occurred while trying to calculate a profile. A profile point is not on the slab. Click on the Fix button to correct the profile point at (x,y).

4 Use the new system for the harped tendons.

40.3.7 An error has occurred while trying to calculate the tendon effective stresses. A tendon has a different number of strands than an adjacent tendon. Investigate tendon #a. You can vary the number of strands along a continuous tendon, but it is discouraged. This warning alerts you that the number of strands within the tendon is variable.

This occurs when a tendon extends beyond the slab edge. To fix this error, stretch the profile point so its end is on the edge or slightly inside the slab edge.

To avoid the warning go to the appropriate tendon layer (the dialog box indicates on which layer the tendon is located) and change the number of strands in the tendon.

The dialog box offers an automatic fix (Click on the Fix button). If you click this button, Concept moves the profile point to the nearest concrete element.

tool.

40.3.4 An error has occurred while trying to calculate a profile. A profile point is not within the slab (vertically). Adjust the profile at (x,y). This occurs when a tendon profile point is not within the slab thickness. Profile values are always relative to the slab or beam soffit at the location of the profile point. The easiest way to find these problems is to look at a tendon perspective. If a profile point is at a top or bottom surface step, Concept moves the profile point so that there is no ambiguity. You should check that the profile point is within the expected slab area.

40.3.5 An error has occurred while trying to calculate the tendon profiles. A tendon is out of the slab at (x,y). This is different to 40.3.4 in that the profile points are within the slab, but the tendon is out of the slab somewhere between the profile points. This usually occurs when there is a top or bottom surface step.

40.3.6 Tendon #a is harped, and hence violates the minimum allowable radius (b) A harped tendon has (vertically) straight segments. There is thus a zero radius at the profile point(s). To avoid the harped tendon warning:

1 Choose Criteria > Materials. 2 Create a new PT system (possibly called “Harped”). 3 Set the minimum radius for the new PT system to zero.

RAM Concept

Note: It is usually best to use the Select Connected Tendons See “Can I terminate some strands past a column?” on page 207 of Chapter 39, “Frequently Asked Questions” for more advice.

40.3.8 An error has occurred while trying to calculate the tendon effective stresses. A tendon is not connected to any jacks. Investigate tendon #a. [If any tendons are stressed then all tendons must be stressed.] Concept calculates losses in tendons that have one or two jacks attached. Concept does not allow a (latitude or longitude) tendon layer to have some tendons with jacks but other tendons with no jacks. You can have one tendon layer (say, latitude) with jacked tendons and the other tendon layer with no jacks. When you encounter this error, find the tendon (from the number given) and draw at least one jack on the tendon.

40.4 Load History Deflections

40.4.1 An error has been found while calculating load history deflections. The floor may have incomplete design strip/cross section coverage to accurately calculate load history deflections. The slab coverages are a and b in orthogonal directions In order to accurately calculate load history deflections, Concept needs each element containing significant forces to be covered by the tributary of a design strip cross section or design section tributary. In order to make sure the user hasn’t forgotten to define strips over a large portion of the slab, Concept performs some rudimentary checks to make

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Chapter 40 sure a large portion of the slab is covered by cross section tributaries in two pependicular directions. This warning can be safely ignored in one-way slab regions where the spanning direction is appropriately covered by cross sections.

40.5 Miscellaneous

40.5.1 An Error occurred while trying to calculate everything. An error has occurred while triangularizing the stiffness matrix. The structure is unstable at node: a, DOF: Y-Axis Translation. Revise the structure. This means that the structure has no lateral stability. You need to either provide some lateral stability (e.g. shear walls, columns with sufficient moment connections, lateral springs etc.) or auto-stabilize the structure. To auto-stabilize the structure:

1 Choose Criteria > Calc Options 2 Choose the General tab 3 Check the Auto-stabilize structure in X and Y directions

box.

dead and live loadings. Concept provides the warning when this is violated. The warning usually occurs when you have added load combinations and forgotten to enter the Balance Loading load factors. To avoid the warning change all load factors for the Balance Loading to 1 for all of the load combinations that utilize the service (sustained service / max service) rule sets.

40.5.4 Load Combination “Service” (Sustained Service / Max Service) has unusual balance and / or hyperstatic load factors. This is likely an error. Any load combination that uses the Service (and Sustained Service / Max Service) rule sets should logically have a load factor of 1 for the Balance Loading (regardless of the presence of tendons) and a load factor (and alternate envelope factor) of zero for the Hyperstatic Loading. Concept provides the warning when this is violated. The warning usually occurs when you have added load combinations and forgotten to enter the Balance Loading load factors. To avoid the warning change all load factors for the Balance Loading to 1 for all of the load combinations that utilize the service (sustained service / max service) rule sets.

Note: This does not work if there are lateral loads. 40.5.2 An error occurred: Loading has horizontal loads, but the structure is automatically stabilized in the X and Y directions. You cannot auto-stabilize the structure if there are horizontal loads (other than tendons). You must (1) uncheck the Auto-stabilize structure in X and Y directions box in the General tab of the Calc Options, and (2) provide some lateral stability (e.g. shear walls, columns with sufficient moment connections, lateral springs etc.).

40.5.3 The code rules selected in Rule Set “Service Design” do not appear compatible with the load factors in the load combinations using the rule set. This is likely an error. Any load combination that uses the Service (and Sustained Service / Max Service) rule sets should logically have a load factor of 1 for the Balance Loading (regardless of the presence of tendons) and load factors of no more than 1 for

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40.5.5 Rule Set “Strength Design” is being used by load combinations that appear to have load factors set for different purposes. This is likely an error. Any load combination that uses the Strength (or Ductility) rule sets should logically have a load factor (and alternate envelope factor) of 1 for the Hyperstatic Loading (regardless of the presence of tendons). Concept provides the warning when this is violated. The warning usually occurs when you have added load combinations and forgotten to enter the Hyperstatic Loading load factors. To avoid the warning change all load factors (and alternate envelope factors) for the Hyperstatic Loading to 1 for all of the load combinations that utilize the strength or ductility rule sets.

40.5.6 The mat / raft is likely unstable. There is less that 25% contact area. When the mat (raft) has a significantly reduced bearing area it is likely that bearing pressures are very high and there could be instability.

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Chapter 40

40.5.7 Punching Check #a is not located at a column This error occurs when a column is relocated after the punching checks have been drawn and the punching check is no longer centered on the column. You need to remove and redraw the punching check. It usually helps to show the punching check number. To display the punching check number (as opposed to column number):

1 Choose Layers > Design Strips > Punching Checks Plan. 2 Choose View > Visible Objects (

).

3 Check the Punching Shear Checks numbers box.

40.5.8 Too many slab shapes intersecting the column shape at (x,y) RAM Concept uses very sophisticated algorithms to find the critical sections around the column and slab irregularities. If the column intersects a large number of slab thickness changes (such as where beams frame in on each side), the run time could be very long. In this instance, Concept just reports this error. This error can be resolved by making the punch check smaller, simplifying the slab geometry around the column, or deleting the punch check.

RAM Concept

40.5.9 An error has been found. The cross section trimming for strip ab-c has caused there to be no concrete remaining at one or more locations. This error is typically reported at steps in the slabs. The inter cross section slope limit is trimming the entire cross section away at the step. See “Inter Cross Section Slope Limit Trimming” on page 108 for more information. You can avoid the problem by setting the inter cross section slope limit to a large value in spans containing large steps. You should, however, consider the underlying reason for the error.

40.5.10 An error has been found. [Design strip] ab-c has reinforcing bars with too much cover (the bottom bar is closer to the top than the top bar). The trimmed cross section has a thickness and covers such that the location of the bars is illogical. This is likely to happen with thin slabs, or steps.

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Chapter 41

41 Simple RC Slab Tutorial This chapter describes the steps for modeling a single panel two-way flat plate with uniform loads.

6 Go to “Draw the slab area:”, or select and delete the four columns and try the next method.

The objective of the tutorial is to help you learn some basic modeling skills and expose you to a number of tools and methods that should prove useful for real projects.

7 Right click over the plan and choose Grid.

The codes used are ACI 318-02, AS3600-2001, BS8110:1997, EC2 - 2004, IS 456 : 2000, and CSA A23.304.

8 In the Grid Setup dialog box:

• Set x and y to 1 foot [0.25 meters]. • Click OK. 9 Turn on Snap to Grid (

).

10 Click the Column tool (

The instructions show “US units” for an ACI 318 design, with metric values and units in square brackets for AS3600, BS8110, EC2, IS 456, and CSA A23.3. The metric values are not exact conversions.

).

11 Place the cursor near the following coordinates and click

(the cursor will snap to the grid and the coordinates appear in the command line): • 0, 0 ft. [0, 0 m]

For information on creating a new file, see “Creating and opening files” on page 5.

• 24, 0 ft. [7.25, 0 m] • 24, 20 ft. [7.25, 6 m] • 0, 20 ft. [0, 6 m]

41.1 Defining the structure

12 Go to “Draw the slab area:”, or select and delete the four

columns and try the next method. You start by drawing the structure and generating the element mesh.

13 Draw the two columns at 0, 0 ft. [0, 0 m] and 24, 0 ft.

[7.25, 0 m] by one of the previous two methods. 14 Select the two columns.

Define the column locations and properties:

1 Choose Layers > Mesh Input > Standard Plan. 2 Double click the Column tool (

).

3 In the Default Column Properties dialog box:

• Choose a Concrete Strength of 5000 psi [32 MPa for AS3600; C32/40 for BS8110 & EC2, M40 for IS 456; 30 MPa for CSA A23.3].

15 Click the move tool (

).

16 Hold down shift and click anywhere on the workspace. 17 Type r0,20 [r0, 6], and press Return.

Note: This copies the two columns using the relative command. See “Using relative coordinates” on page 18 for further explanation.

• Set Width to 24 inches [600 mm].

Draw the slab area:

• Set Depth to 24 inches [600 mm].

1 Turn on Snap to Intersection (

4 Click OK.

Define the column locations by one of the following three methods. We strongly recommend you try all of them for the purpose of learning different procedures. 5 Enter the following coordinates (x, y) and press return

after each: • 0, 0 ft. [0, 0 m] • 24, 0 ft. [7.25, 0 m] • 24, 20 ft. [7.25, 6 m] • 0, 20 ft. [0, 6 m]

).

2 If previously turned on, turn off Snap to Grid ( 3 Double click the Slab Area tool (

).

) to edit the default

properties. 4 In the Default Slab Area Properties dialog box:

• Choose a Concrete Strength of 5000 psi [32 MPa for AS3600; C32/40 for BS8110 & EC2, M40 for IS 456; 30 MPa for CSA A23.3]. • Set Thickness to 12 inches [300 mm]. • Leave Surface Elevation as 0 and Priority as 1. • Click OK.

see Figure 2-1 on page 5.

) selected, define the four corners of the slab by snapping at the “outside” corner of each column.

Note: Do not enter the actual units (ft., m)

6 Complete the rectangle by clicking at your starting point

Note: The coordinates will appear in the command line,

RAM Concept

5 With the Slab Area tool (

(or type “c” in the command line and press Return).

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Chapter 41 Hatch the slab area:


).

The Visible Objects dialog box will appear.

You will now see a somewhat random mesh. This produces reasonable results, but a regular mesh is better. You can regenerate a significantly improved mesh once you have defined design strips. This mesh is shown in Figure 41-4.

2 Check “Hatching” under “Slab Areas”, and then click

OK.

Note: You can also right click to see a popup menu that includes the Visible Objects command. You have now defined the slab but the element mesh does not yet exist.

Figure 41-2 Element: Standard Plan (ACI318 example dimensions).

Figure 41-1 After defining the slab, the Mesh Input: Standard Plan shows the slab area (hatched), and the columns. Generate the mesh:


).

2 In the Generate Mesh dialog box set the Element Size to

2 feet [0.6 m]. 3 Click Generate. View the mesh:

1 Choose Layers > Element > Standard Plan. Figure 41-3 Element: Standard Plan (AS3600, BS8110, EC2, IS 456 and CSA A23.3 example).

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41.2 Drawing the loads RAM Concept calculates the concrete self-weight automatically. There is no limit to the number of loadings than can be specified but this example defines only Live Loading. Draw live loads:

1 Choose Layers > Loadings > Live (Reducible) Loading >

All Loads Plan. 2 Double click the Area Load tool (

).

3 In the Default Area Load Properties dialog box:

• Change Fz to 50 psf [2.5 kN/m2]. • Click OK. Figure 41-4 Element: Standard Plan after regeneration (for ACI318 example; the metric codes produce a similar mesh)

This tool will now draw area loads of 50 psf [2.5 kN/ m2]. 4 Define an area load over the entire slab by clicking four

View the structure:

1 Choose Layers > Element > Structure Summary

Perspective. 2 Use the Rotate about x- and y-axes tool (

corners of a quadrilateral and then typing “c”. This shape need not match the slab’s exact dimensions, but should cover the slab.

) to rotate

the floor. 3 Click the Set Print Viewpoint tool (

).

Upon returning to this perspective, you can look at the saved view by clicking Show Set Viewpoint (

).

Figure 41-6 Live (Reducible) Loading: All Loads Plan (with area loads hatching turned on): ACI318 example.

Figure 41-5 Element: Structure Summary Perspective.

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Chapter 41 • Check the Middle Strip uses Column Strip Properties box. • Click OK. 4 Click the Generate Spans tool (


Generate Spans. 5 The Generate Spans dialog box opens with Spans to

Generate set to Latitude (as shown in Figure 41-8): • Set Minimum Span Length to 2 feet [0.6 meters]. • Click OK.

Figure 41-7 Live (Reducible) Loading: All Loads Plan (with area loads hatching turned on): AS3600, BS8110, EC2, IS 456, & CSA A23.3 example.

41.3 Defining the design strips Design strips are an essential part of RAM Concept because they link finite element analysis with concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for cross-section design. There are two directions named Latitude and Longitude. It is normal practice to design two-way RC flat plates with column and middle strips in two orthogonal directions, and that practice is used here.

Figure 41-8 Generate spans dialog box

The latitude spans appear, as shown in Figure 41-9. 6 Click the Generate Strips tool (


Generate Strips. The latitude design strips appear, as shown in Figure 41-10.

Draw latitude design strips:

1 Choose Layers > Design Strip > Latitude Design Spans

Plan. 2 Double click the Span Segment tool (

).

3 The Default Span Properties dialog box opens to the Strip

Generation properties. • Set Column Strip Width Calc to Code Slab (this is the default for the AS3600 and IS 456 templates). • Click the General tab. • Uncheck the Consider as Post-Tensioned box. • Click the Column Strip tab. • Change CS Top Bar to #6 [N20 for AS3600; T20 for BS8110; H20 for EC2; T20 for IS 456; 20M for CSA A23.3]. • Change CS Bottom Bar to #5 [N16 for AS3600; T16 for BS8110; H16 for EC2; T16 for IS 456].

Figure 41-9 Latitude direction spans

• Click the Middle Strip tab.

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Chapter 41 • Click the “up-down” orientation button, and click OK.

Figure 41-10 Latitude direction design strips (with hatching turned on) Figure 41-11 Generate spans dialog box

Draw longitude design strips:

1 Choose Layers > Design Strip > Longitude Design Spans

The longitude spans appear, as shown in Figure 41-12.


).



3 Click the Column Strip tab in the Default Span Properties

Generate Strips.

dialog box.

The longitude design strips appear, as shown in Figure 4113.

The defaults set up in the Latitude Design Spans Plan will have remained the same. Since the cover cannot be the same for both directions, change it for the longitudinal direction. • Change CS Top Cover to 2.25 inches [60 mm]. • Change CS Bottom Cover to 1.38 inches [41 mm]. • Click OK. 4 Click the Generate Spans tool (


Generate Spans. 5 In the Generate Spans dialog box:

• Set Spans to Generate to Longitude.

Figure 41-12 Longitude direction spans

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Figure 41-13 Longitude direction design strips (with hatching turned on) Figure 41-14 Design Strip: Punching Checks Plan

Now that there are design strips, you can generate a much more regular mesh.

41.5 Calculate and view the results

Regenerate the mesh:


).

2 Click Generate. 3 There is now a better mesh. View the mesh on the

Element Standard Plan.

You can “run” the file at any time during modeling to analyze and check for errors. After you have drawn design strips, Concept can analyze and design. You can then view the results.

Refer to Figure 41-4 to view the new mesh. Calculate:

1 Click Calc All (

).

41.4 Drawing punching shear checks 41.5.1 Design status Drawing the punching checks is very straightforward. Draw punching shear checks:

1 Choose Layers > Design Strip > Punching Checks Plan. 2 Double click the Punching Shear Check tool (

).

3 In the Default Punching Shear Check Properties dialog

box: • Change Cover to CGS to 2.25 inches [60 mm] (the average top cover) • Click OK. 4 Fence the slab with the Punching Shear Check tool.

See Figure 41-14 to view the punching checks.

The purpose of status plans is to indicate whether there are any violations of code limits for ductility, one-way shear, and punching shear. View Status:


For ACI318, AS3600 and IS 456, the status plan shows OK for all design strips and punching shear checks. See Figure 41-15. The BS8110 status plan shows punching shear failure. See Figure 41-16. The EC2 and CSA A23.3 status plan show OK for all design strips and OK with SSR for all punching shear checks.

Note: Status does not flag excessive deflections.

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Chapter 41 View Reinforcement:


This shows all the code-determined reinforcement for each of the eight design strips. See Figures 41-17 through 41-20.

Figure 41-15 Design Status: Status Plan for ACI318, AS3600 & IS 456

Figure 41-17 Design Status: Reinforcement Plan for ACI318

Figure 41-16 Design Status: Status Plan for BS8110 (Amd #1 & #2)

41.5.2 Design reinforcement

Figure 41-18 Design Status: Reinforcement Plan for AS3600

You can view reinforcement results as bar drawings or plots.

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Chapter 41 design strip cross section. The following uses latitude bottom reinforcement as an example. View Reinforcement Controlling Criteria:

1 Choose Layers > Design Status > Latitude Bottom

Reinforcement Plan. 2 Choose View > Visible Objects (

).

3 In the span designs (not section designs) column:

uncheck Bar Descriptions and check Controlling Criteria, and click OK. See Figures 41-25 through 41-28 for latitude bottom reinforcement controlling criteria.

Figure 41-19 Design Status: Reinforcement Plan for BS8110 (Amd #1 & #2)

Figure 41-21 Design Status: Latitude Bottom Reinforcement Plan for ACI318.

Figure 41-20 Design Status: Reinforcement Plan for IS 456

Such plans often suffer from “information overload” with congested results. For this reason, you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom), direction (latitude or longitude), and type (flexural or shear). You should decide which plans best convey the results without too much clutter. View Specific Reinforcement:


Reinforcement Plan. See Figures 41-21 through 41-24.

Figure 41-22 Design Status: Latitude Bottom Reinforcement Plan for AS3600.

Concept provides you with the code clause numbers that control the maximum top and bottom reinforcement at any

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Figure 41-23 Design Status: Latitude Bottom Reinforcement Plan for BS8110 (Amd #1 & #2). Figure 41-26 Design Status: Latitude Bottom Reinforcement Plan for AS3600 with Bar Descriptions unchecked and Controlling Criteria checked.

Figure 41-24 Design Status: Latitude Bottom Reinforcement Plan for IS 456.

Figure 41-27 Design Status: Latitude Bottom Reinforcement Plan for BS8110 with Bar Descriptions unchecked and Controlling Criteria checked.

Figure 41-25 Design Status: Latitude Bottom Reinforcement Plan for ACI318 with Bar Descriptions unchecked and controlling Criteria checked.

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Chapter 41 6 Check the Active box. 7 Select the Bottom radio button. 8 Change Max Frame Number to 2, and click OK.

See Figures 41-29 to 41-32 for the reinforcement plots.

Figure 41-28 Design Status: Latitude Bottom Reinforcement Plan for IS 456 with Bar Descriptions unchecked and Controlling Criteria checked.

41.5.3 Design reinforcement plots Concept has plotting options that you can use to view various strip-based results such as moment, shear, precompression, reinforcement and crack width.

Figure 41-29 Design Status: Plot: Latitude Bottom Reinforcement Plan for ACI318.

This section steps you through setting up a reinforcement plot. You can bypass this section, but there are steps that help you learn the more powerful aspects of the program. To create a new plan that plots latitude bottom reinforcement:

1 Choose Layers > New Plan. 2 Enter a name for the plan, such as “Plot: Latitude Bottom

Reinforcement”. (Concept automatically prepends the layer name and appends the word “Plan”). 3 Select the “Design Status” layer, and click OK.

The Visible Objects dialog box appears. 4 Click Show Nothing and click OK. 5 Choose View > Plot (

).

The Plot dialog box appears with the Section Design dialog.

232

Figure 41-30 Design Status: Plot: Latitude Bottom Reinforcement Plan for AS3600

RAM Concept

Chapter 41 You can see that, for ACI318, AS3600 and IS 456, the unreinforced stress ratio (USR) is less than 1.0 and hence punching shear capacity is satisfactory. These results are shown in Figure 41-33, Figure 41-34 and 41-37. The USR for BS8110 is 1.17, as shown in Figure 41-35. Since the stress ratio exceeds 1.0, shear reinforcement is required. Concept designs stud shear reinforcement (SSR) for such situations. View SSR:

1 Choose Layers > Design Status > SSR Plan.

The result for BS8110 is shown in Figure 41-36.

Figure 41-31 Design Status: Plot: Latitude Bottom Reinforcement Plan for BS8110 (Amd #1 & #2).

Figure 41-33 Design Status: Punching Shear Status Plan for ACI318.

Figure 41-32 Design Status: Plot: Latitude Bottom Reinforcement Plan for IS 456

41.5.4 Punching shear You can view punching shear results on dedicated plans. View Punching Shear:


Plan. Figure 41-34 Design Status: Punching Shear Status Plan for AS3600

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Chapter 41 Concept uses gross section inertia for deflection contours. You can investigate the effects of creep, shrinkage and cracking with Load History Deflections. See Chapter 65, “Load History Deflections” for more information.

Note: The following deflection plans DO NOT consider cracking, creep or shrinkage. View service deflection:


Deflection Plan. The service deflection contours should be visible, as shown in Figures 41-38 through 41-41.

Note: These models use compressible columns and hence Figure 41-35 Design Status: Punching Shear Status Plan for BS8110 (Amd #1 & #2).

the deflection includes column deflection.

Note: The AS3600 template uses 70% of live load for the Service LC.

Figure 41-36 Design Status: SSR Plan for BS8110 (Amd #1 & #2).

Figure 41-38 Service LC: Deflection Plan for ACI318.

Figure 41-37 Design Status: Punching Shear Status Plan for IS 456

41.5.5 Deflection Usually you are interested in deflections for Service (Dead and Live Load plus PT if applicable) and Long Term.

234

Figure 41-39 Service LC: Deflection Plan for AS3600.

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Chapter 41

41.5.6 Bending Moments

.

While it is not necessary to view bending moments, it can be useful, especially for irregular structures. Even though principal moments are important, the default moment contours plans are for Mx (moment about the x-axis) and My. This is because most designers detail reinforcement orthogonally, and the directions are usually the x- and yaxes. You can view moments about any axes, including the principal axes. It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful.

Note: Plot Distribution Tools are useful for qualitative results but not quantitative results. Refer “Section distribution plots” on page 158, and, in particular, the “Summary” on page 160 Figure 41-40 Service LC: Deflection Plan for BS8110.

View Moments:

1 Choose Layers > Load Combinations > Code Specific

Load Combination > Mx Plan. For ACI318, use Factored LC: 1.4D. For AS3600, use Ultimate LC: 1.2D + 1.5 L. For BS8110, use Ultimate LC: 1.4D + 1.6L + 1.6S. For IS 456, use Ultimate LC: 1.5D + 1.5 L + 1.6S. For EC2, use Ultimate LC: 1.25D + 0.9H + 1.5L + 0.75S For CSA A23.3, use Factored LC: 1.4D. The contours are moment per unit length about the global x-axis. 2 Turn on Snap Orthogonal (

)

3 Click the Selected Plot Distribution tool (

Figure 41-41 Service LC: Deflection Plan for IS 456.

).

4 Click first at the top of the structure and again on the View service deflection without colors:

bottom side.


This shows the bending moment shape, about the x-axis, along the line you have drawn. See Figures 41-42 through 41-45.

Deflection Plan. 2 Right click over the plan and choose Plot (

) to change

Plot Type from Color Contour to Contour.

Note: As previously mentioned, you are strongly advised to review Chapter 65, “Load History Deflections” to understand how Concept considers cracking, creep and shrinkage for deflection calculations.

5 Now click from left to right across the structure.

This shows how Mx varies along the span. If you do it through the column centers, you will see how the column strip has large negative moments and a small positive moment near midspan. If you do it in the middle strip, you will see only positive moments. See “About plot sign convention” on page 28 of Chapter 8, “Choosing Sign Convention” for further information.

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Chapter 41

Figure 41-42 Factored LC: 1.4D: Mx Plan showing use of Plot Distribution tool for ACI318.

Figure 41-44 Ultimate LC: 1.4D+1.6L: Mx Plan showing use of Plot Distribution tool for BS8110.

Figure 41-45 Ultimate LC: 1.5D+1.5L: Mx Plan showing use of Plot Distribution tool for IS 456. Figure 41-43 Ultimate LC: 1.2D+1.5L: Mx Plan showing use of Plot Distribution tool for AS3600.

41.6 Drawing reinforcement Version 3.0 introduces vastly improved tools for drawing reinforcement bars.

41.6.1 Drawing a bottom reinforcement mat In this section you are shown how to draw a bottom reinforcement mat and see the ramifications. Draw bottom reinforcement:

1 Choose Layers > Reinforcement > Bottom Bars Plan. 2 Double click the Distributed Reinf. Cross in Perimeter

tool (

).

3 The Default Distributed Reinforcement Properties dialog

box opens.

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Chapter 41 • Note that Elevation Reference is set to Bottom Cover. • Change Elevation to 0.75 inches [25 mm for AS3600, BS8110, IS 456, EC2, and CSA A23.3]. • Change Bar Type to #5 [N16 for AS3600; T16 for BS8110; T16 for IS 456; H16 for EC2; 15M for CSA A23.3]. • Change Spacing to 12 inches [225 mm for AS3600; BS8110, IS 456, EC2, and CSA A23.3]. 4 Turn on Snap Orthogonal (

).

5 Click somewhere on the slab. 6 Click at another point to the left or right to define the

orientation of the (primary) reinforcement. A polygon appears that is the shape of the slab. Once the file is run you can view the individual bars via the Visible Objects dialog box.

Note: This creates three objects: a polygon matching the

Figure 41-47 Bottom mat defined by clicking at points A and B. Point C appears such that AC = AB. The bars are shown to points A and B but the symbol indicates the reinforcement continues to the slab edges.

slab outline, a reinforcement object that belongs to the latitude reinforcement layer and a reinforcement object that belongs to the longitude reinforcement layer. 7 Using the Stretch tool, you can adjust the bar grip

postilions for a better appearance. Refer to Figures 41-46 to 41-47 for ACI 318. Refer to Figures 41-49 to 41-51 for AS3600, BS8110 and IS 456.

Figure 41-48 Bottom mat modified by stretching grip points at B and C.

Figure 41-46 ACI 318: Reinforcement > Bottom Bars Plan

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Chapter 41

Figure 41-49 AS3600, BS8110, IS456: Reinforcement > Bottom Bars Plan

Figure 41-51 Bottom mat modified by stretching grip points at B and C.

Figure 41-50 Bottom mat defined by clicking at points A and B. Point C appears such that AC = AB. The bars are shown to points A and B but the symbol indicates the reinforcement continues to the slab edges.

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Chapter 42

42 PT Flat Plate Tutorial: ACI 318-08 This chapter describes the steps for modeling a posttensioned two-way flat plate with uniform loads. The objective of this tutorial is to build on the skills learned in the Chapter 41 RC tutorial and introduce new steps, such as using a CAD drawing and post-tensioning. Some tools and methods described in the RC tutorial are not used here. As such, it is highly recommended that you first do the RC tutorial. This is not a particularly “aggressive” design. After you have completed the tutorial, you may wish to make the slab thinner to investigate the ramifications.

Draw the slab area:


(

) and Snap to Point

).

2 Double click the Slab Area tool (



• Choose a Concrete Strength of 5000 psi. • Set Thickness to 10 inches. • Leave Surface Elevation as 0 and Priority as 1. • Click OK.

You could also use this as a reinforced concrete tutorial by making a few adjustments (for example, a thicker slab).


) selected, define the 10 vertices of the slab outline by snapping to the imported drawing’s slab corners.


Note: There are two vertices near each other near B-5 at 86, 27 ft and 86, 29 ft. Cursor plan coordinates display next to the command prompt. 5 Complete the polygon by clicking at your starting point

42.1 Import the CAD drawing

(or type “c” in the command line and press Enter).

The CAD file you import is located in your RAM Concept program directory Import the CAD file:

1 Choose File > Import Drawing. 2 Select the CAD drawing file flat_plate.dwg.

The File Units dialog box appears. 3 Select Inches (the units used in the CAD file) and click

OK.

42.2 Define the structure To use the CAD file you need to make it visible on the Mesh Input layer. Show the drawing on the mesh input layer:

1 Choose Layers > Mesh Input > Standard Plan. 2 Choose View > Visible Objects (

).


Figure 42-1 The slab outline on the Mesh Input: Standard Plan. Draw the balcony slab area:



includes the Visible Objects command.

properties.

3 Click the Drawing Import tab.

2 In the Default Slab Area Properties dialog box:

4 Click Show All, and then click OK.

• Change Thickness to 8 inches. • Change Surface Elevation to -2 inches. • Change the Priority to 2, and click OK.

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239

Chapter 42 3 With the Slab Area tool (

) selected, define the six vertices of the balcony outline by clicking at each vertex, and then click at your starting point (or type “c” in the command line and press Enter).

Draw the opening:

1 Select the Slab Opening tool (

).

2 Define the four corners of the opening by clicking at each

location, and then click at your starting point.

Figure 42-2 The balcony slab on the Mesh Input: Standard Plan. Draw the drop caps:




• Change Thickness to 20 inches.

Figure 42-3 The opening on the Mesh Input: Standard Plan. Hatch the slab areas:

• Change Surface Elevation to 0, and leave the Priority as 2.


• Click OK.


).

) selected, define the four drop caps with four or five vertices as appropriate.

2 Check “Hatching” under “Slab Areas”.

4 Go to “Draw the opening:”, or try the next method


5 With the Selection tool (

), select (by double-clicking) and delete the drop cap at B-2.


6 Click Redraw (



).

Some tool button icons have a small triangle in the lower right corner ( ). This indicates that there are other similar tools available for this button. 7 Place the mouse over the Slab Area tool (

) and press

down on the left mouse button for one second.

3 Check “Hatching” under “Slab Openings”, and click OK.

1 Double click on the Column tool (

).


• Choose a Concrete Strength of 5000 psi. • Set Width to 24 inches. • Set Depth/Diameter to 24 inches.

A pop-up menu appears.

3 Click OK.

8 Select the Drop Cap tool from the menu.

4 Click at the center of all 13 column locations shown on

the imported drawing. The selected tool becomes current for that button. 9 Click at the column at B-2.

Define the wall location and properties:

1 Turn on Snap Orthogonal (

A Drop Cap Tool dialog box appears. 10 Enter an angle of zero degrees. 11 Enter a side dimension of 3.75 feet and click OK.

2 Double click on the Wall tool (

). ).

3 In the Default Wall Properties dialog box:

• Choose a Concrete Strength of 3000 psi. 4 Click OK.

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Chapter 42 5 Define the wall by clicking at the start and end points, on

3 Click Generate.

the centerline. • Place the cursor near 29.5, 87 ft and it will snap to where the center of the wall intersects the edge of the slab, and click. • Place the cursor at the center of the column at C-2 (it will snap orthogonally) and click.

View the mesh:

1 Choose Layers > Element > Standard Plan.

You will now see a somewhat random mesh. This will still produce reasonable results, but will significantly improve when you regenerate it later on.

You have now defined the structure but the element mesh does not yet exist. 6 Go to “Generate the mesh:”, or try the next method. 7 The wall should be highlighted as it is the current

selection. If not, select it by double-clicking and press Delete. 8 Click Redraw (

).

9 Place the mouse over the Wall tool (

) and press down

on the left mouse button for one second. A pop-up menu appears. 10 Select the Left Wall tool from the menu. 11 Click at the extreme corner of the slab near D-2. 12 Click at Grid C, near C-2.

Figure 42-5 Element: Standard Plan. View the structure:



) to rotate the

floor. 3 Click the Set Print Viewpoint tool (

).


).

Figure 42-4 After defining the slab, the Mesh Input: Standard Plan shows the slab areas and opening (hatched), the columns and the wall. Generate the mesh:


).



3 feet.

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Chapter 42

42.3 Define the loads RAM Concept calculates the concrete self-weight automatically. Concept uses superposition of loads. The easiest way to define areas with increased area loads is to draw a “blanket” area load over the entire floor, and then draw the additional loads. There is no limit to the number of loadings than can be specified.

Figure 42-7 Live (Reducible) Loading: All Loads Plan (showing the balcony area load).

Define the typical live load:



).


• Change Fz to 40 psf and click OK. This tool will now draw area loads of 40 psf. 4 Define an area load over the entire slab by clicking four

corners of a quadrilateral and then typing “c”. This shape need not match the slab’s exact dimensions, but should cover the slab. Define the balcony live load:


).

2 Define an area load by snapping to the six vertices of the

balcony (and then type “c”). In this situation, it is best for the load to match the balcony’s dimensions. You have drawn another 40 psf load. This load should be highlighted as it is the current selection. If not, select it before proceeding by double-clicking with the selection tool. 3 Choose Edit > Selection Properties, or right-click and

choose Selection Properties. 4 In the dialog box, change Fz to 60 psf and click OK.

There is now a total live load on the balcony of 100 psf.

Note: You could have drawn the 60 psf load by first changing the area load default properties and then using the tool.

Figure 42-8 Live (Reducible) Loading: All Loads Plan (with area loads hatching turned on). Define the other dead loading:


All Loads Plan. 2 With the Selection tool (

), select both area loads (fencing the balcony load selects both loads). 3 Choose Edit > Copy. 4 Choose Layers > Loadings > Other Dead Loading > All

Loads Plan. 5 Choose Edit > Paste.

This pastes the live loads onto the Other Dead Loading: All Loads Plan, ready for editing. 6 With the Selection tool (

), select the “blanket” load by double clicking in the center of the floor. 7 Right click on the plan and choose Selection Properties

from the popup menu. 8 In the Properties dialog box, change Fz to 20 psf, and

click OK. 242

RAM Concept

Chapter 42 9 Double-click the balcony load.

The balcony load should be the only selected load. 10 Right click on the plan and choose Selection Properties

from the popup menu. 11 In the Properties dialog box, change Fz to -20 psf, and

click OK. The balcony other dead load is now effectively zero.

Figure 42-9 Other Dead Loading: All Loads Plan (with area loads hatching turned on).

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Chapter 42

42.4 Define the post-tensioning

11 With the Tendon Polyline tool (

) selected, draw a

tendon along grid B: Post-tensioning methodology varies from country to country. In the USA it is common to use the “banding” technique for detailing tendons in two-way slabs. Banding means concentrating the tendons over support points in one direction, and distributing them uniformly in the orthogonal direction. This method is generally used in conjunction with full-panel design strips. That is, column and middle strips are not used.

Note: RAM Concept has two layers for tendons called latitude and longitude. Refer to “Using the latitude and longitude prestressing folders” on page 133 for more information.

Note: The tutorial in Chapter 49 explains the use of Strip Wizard to establish an estimate of the number of strands required for the critical band.

• Click at the center of the column at grid intersection B-1. • Click at the center of the column at B-2. • Click at the center of the column at B-3. • Click at the center of the column at B-5. • Right click, and then click Enter. 12 With the Tendon Polyline tool (

• Click at the center of the column at grid intersection B.8-1. • Click at the center of the column at C-2. • Click at the center of the column at C-3. • Click at the center of the column at C-4. • Right click, and then click Enter.

Define the manual latitude tendons:

1 Choose Layers > Latitude Prestressing > Manual

Latitude Tendon > Standard Plan. 2 Choose View > Visible Objects (

).

The latitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 10-inch slab. 13 With the Selection tool (

), select all of the terminated tendon segments, other than those over a drop cap, by:

3 Click the Drawing Import tab. 4 Click Show All, and click OK.

• Double clicking at grid intersection B-1.

Showing the CAD file makes the following instructions easier to follow. 5 Double click the Tendon Polyline tool (

) to edit its

default properties. 6 In the Default Tendon Properties dialog box:

• Hold the Shift key down and double click at B.81. • Hold the Shift key down and double click at C-4. • Hold the Shift key down and double click at D-2. • Hold the Shift key down and double click at D-4.

• Set Strands per Tendon to 9.

14 Right click on the plan and choose Selection Properties

• Set Profile at end 1 to 8.75 inches.

from the popup menu.

• Set Profile at end 2 to 1.25 inches, and click OK.

15 In the Properties dialog box, set Profile at end 1 to 5

Note: The one-inch cover to the half-inch diameter strand

inches and click OK.

determines these profiles.


7 Turn on Snap to Intersection ( 8 With the Tendon Polyline tool (

), select all of the terminated tendon segments over a drop cap, by:

). ) selected, draw a

tendon along grid A:

• Double clicking at grid intersection A-1. • Hold the Shift key down and double click at A-3.

• Click at the center of the column at grid intersection A-1.

• Hold the Shift key down and double click at B-5. 17 Right click on the plan and choose Selection Properties

• Click at the center of the column at A-2.




• Right click, and then click Enter.

inches and click OK.

9 Double click the Tendon Polyline tool (

) to edit its


• Set Strands per Tendon to 21, and click OK.

244

) selected, draw a

tendon along grid C:

Note: This sets the tendon anchorage profile to the centroid of the 10-inch slab, rather than the centroid of the drop cap. 19 With the Selection tool (

), double click the tendon

segment at B-2.

RAM Concept

Chapter 42 20 Right click on the plan and choose Selection Properties

from the popup menu. 21 In the Properties dialog box, set Profile at end 1 to 18.75

inches and click OK. 22 With the Selection tool (


segment at C-2. 23 Right click on the plan and choose Selection Properties


inches, and click OK.

Note: This accounts for the step near this location. 25 With the Selection tool (

), select the tendon segments

between C-2 and C-3. 26 Click the Calc Profile tool (

).

The Calc Tendon Profile dialog box appears and reports the current balance load is -2.58 kips/ft. If this is not the number then you probably selected only one tendon segment.

Figure 42-10 Manual Latitude Tendon: Standard Plan

27 Click Cancel. 28 With the Selection tool (

), select the tendon between

C-3 and C-4. 29 Click the Calc Profile tool (

).

30 Input the desired balance load as -2.6 kips/ft in the Calc

Tendon Profile dialog box and click Calc. The low point (end 2) adjusts to 5.01 inches. 31 With the Selection tool (

), select all the end span

tendons between grids 3 and 5. 32 Right click on the plan and choose Selection Properties

from the popup menu. 33 In the Properties dialog box, set Profile at end 2 to 5


Note: These steps first used the Calc Profile tool to determine a low point that produces a similar average uplift in an end span as the adjacent span, and then manually changed the low points for practical reasons.

Define a latitude tendon polyline:

This example shows that the tendon generation can be mixed between the tendon parameters and manual tendon layers. In most cases you would use exclusively one or the other to work with tendons. 1 Choose Layers > Latitude Prestressing > Latitude

Tendon Parameters. 2 Turn on Snap Orthogonal ( 3 Turn on Snap to Intersection (

). ).

4 Double click the Banded Tendon Polyline tool (

) to

edit its default properties. 5 In the Default Banded Tendon Polyline Properties dialog

box: • Set Number of Strands to 9, and click OK. 6 With the Banded Tendon Polyline tool (

) selected,

draw a banded tendon polyline: • Click at the center of the column at D-4. • Click at the edge of the slab near D-2. Define the latitude profile polylines:

1 Double click the Profile Polyline tool (

) to edit its

default properties. 2 In the Default Profile Polyline Properties dialog box:

• Set Elevation to 5 inches. 3 Draw a profile polyline:

• Click at the top of the column intersection with column line 4 at D-4.

RAM Concept

245

Chapter 42 • Click at the bottom of the column intersection with line 4 at D-4. • Right click and select Enter.

• Set Strands per Tendon to 4. • Set Profile at end 1 to 8.75 inches. • Set Profile at end 2 to 1.25 inches, and click OK.

4 Draw a profile polyline:

• Click at the top of the column intersection with column line 3 at D-3. • Click at the bottom of the column intersection with line 3 at D-3.

Note: The one-inch cover to the half-inch diameter strand determines these profiles. Strictly speaking, you should adjust Profile at end 1 at columns (to avoid a clash with latitude tendons) but you can ignore for this tutorial. 5 With the Full-Span Tendon Panel tool (

) selected,

draw tendons in the bottom left panel:

• Right click and select Enter.



• Click at the corner of the slab at D-2.

• Click at the center of the column at B-1.

• Type r0,-2.


• Right click and select Enter 6 Select the profile polyline at D-3, right click and choose

Selection Properties. Change the elevation to 1.25 inches.

6 In the Tendon Panel dialog box:

• Set Tendon Spacing to Equal.

7 Select all 3 drawn profile polylines. 8 Choose the Generate Span Polylines tool (


).

• Set Spacing to 6 feet, and click OK.

9 Set the Elevation to 1.25 inches, and click OK.

Note: This spacing exceeds some code maxima, but the tendon layout is for design purposes and not necessarily for detailing. 7 With the Full-Span Tendon Panel tool (

) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection B-1. • Click at the center of the column at B.8-1. • Click at the center of the column at C-2. • Click at the center of the column at B-2. 8 In the Tendon Panel dialog box:

• Set Auto Connect, and click OK. 9 Turn on Snap Nearest Snapable Point (

Orthogonal (

) and Snap

).

10 With the Half Span Tendon Panel tool (

) selected,

draw tendons in the balcony: • Click at the center of the column at grid intersection B.8-1. Figure 42-11 Latitude Tendon Parameters: Standard Plan

• Click at the edge of the slab at 0, 59 ft. • Click at the tendon profile point at 24, 56.6 ft.

Define the manual longitude tendons:

1 Choose Layers > Longitude Prestressing > Manual

Note: The snap orthogonal snaps the cursor to 24, 59 ft.

Longitude Tendon > Standard Plan. 2 Turn on Snap to Intersection (

• Click at the tendon profile point at 24, 56.6 ft.

).

3 Double click the Full-Span Tendon Panel tool (

edit its default properties. 4 In the Default Tendon Properties dialog box:

) to


• Set Auto Connect, and click OK. 12 Right click on the plan and choose Selection Properties


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RAM Concept

Chapter 42

inches and Profile at end 2 to 4 inches, and click OK.

• Click at the center of the column at grid intersection B-3.


• Click at the center of the column at C-3.


), select the two shortest of the half-span (cantilever) tendon segments. 15 Right click on the plan and choose Selection Properties


• Click at the center of the column at C-4. • Click at the center of the column at B-5. 24 In the Tendon Panel dialog box:


• Set Layout to Splayed.

Note: This makes the short tendon segments flat.


17 With the Full-Span Tendon Panel tool (

• Set Spacing to 6 feet.

) selected,

draw tendons in the next panel:

• Check Skip start tendon, and click OK.

• Click at the center of the column at grid intersection A-2. • Click at the center of the column at B-2.


) selected,



• Click at the center of the column at grid intersection C-3.


• Click at the center of the column at D-3. • Click at the center of the column at D-4.





• Set Spacing to 6 feet. • Check Skip start tendon, and click OK. 19 With the Full-Span Tendon Panel tool (

) selected,


• Set Auto Connect. • Uncheck Skip start tendon, and click OK.

Note: Auto-connect will ignore the tendons at the first click


because there are already two tendon segments connected at that point.

• Click at the center of the column at C-2. • Click at the center of the column at C-3.

The panel in the top right has too many tendons and some should be deleted.


27 Select the second tendon in this panel.

20 In the Tendon Panel dialog box, click OK to accept the

28 Hold down shift and select the fifth tendon in this panel,

last choices. Alternatively, you could select Auto Connect, but you would have to uncheck Skip Start Tendon.

and press Delete.


draw tendons that terminate in this panel:

) selected,



• Turn on Snap Orthogonal (

Note: This sequence is counterclockwise.

) selected,

).

• Click at the profile point at 63.2, 58 ft.

• Click at the center of the column at grid intersection C-3. • Click at the center of the column at D-3.

• Type r0,7. • Click at the last tendon profile point at 72.8, 58 ft.

Note: The snap orthogonal snaps the cursor to 72.8, 65 ft.

• Enter 31, 86 (feet).

• Click at the last tendon profile point at 72.8, 58 ft. • Turn off Snap Orthogonal (

).


• Click at the center of the column at C-2. 22 In the Tendon Panel dialog box:


• Set Auto Connect.


• Uncheck Skip start tendon, and click OK.



) selected,



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247

Chapter 42 The longitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 10-inch slab. 33 With the Selection tool (

), select all of the terminated tendon segments, other than those over a drop cap or within the balcony slab: • Fence the tendon segments that end on grid A.

48 Repeat for the tendon segment below the moved tendon.

Note: You could cut down the number of steps in moving the tendon from the opening by using the Utility tool. This combines the selection tool with move and stretch. Refer to “Expanding tool buttons” on page 6 and “Using the Utility tool to move and stretch” on page 20 for further information.

• Hold the Shift key down and repeat the procedure until you have selected all applicable end tendon segments (tendon segments terminating at grids B and D). 34 Right click on the plan and choose Selection Properties


inches and click OK. 36 With the Selection tool (

), select all of the terminated tendon segments over a drop cap, by: • Double clicking at grid intersection A-1. • Hold the Shift key down and double click at A-3. • Hold the Shift key down and double click at B-5. 37 Right click on the plan and choose Selection Properties



Note: This sets the tendon anchorage profile to the centroid of the 10-inch slab, rather than the centroid of the drop cap. 39 With the Selection tool (


segment at B-2. 40 Right click on the plan and choose Selection Properties


inches and click OK. Finally, you need to move the tendon that goes through the opening. 42 With the Selection tool (

Figure 42-12 Longitude Tendon: Standard Plan. Replace some manual longitude tendons with a distributed tendon quadrilateral:


), select the tendons between lines 1 and 2, and press the delete button. 2 Choose Layers > Longitude Prestressing > Longitude

Tendon Parameters. 3 Turn on Snap Orthogonal ( 4 Turn on Snap to Intersection (

). ).

5 Double click the Distributed Tendon Quadrilateral tool

(

).

), select the tendon segment that passes through the opening.

• Change the Tendon Orientation Angle to 90 degrees.

43 Choose the Move tool (

• Change the Number of Strands to 0.6667 /feet, and click OK.

).

44 Click anywhere on the plan, and type r-1.5,0. 45 With the Selection tool (

), select the tendon segment

above the moved tendon. 46 Choose the Stretch tool (

).

47 Stretch the end of the tendon segment to meet the end of

the moved tendon.

6 With the Distributed Tendon Quadrilateral tool (

)

selected: • Click the corner of the slab at A-1. • Click the corner of the slab at C-1. • Click the center of the column at C-2. • Click the edge of the slab at A-2.

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RAM Concept

Chapter 42 22 Right click and choose Selection Properties.

Define the longitude profile polylines:

1 Double click the Profile Polyline tool (

) to edit its

23 Change the Elevation Reference to Above Soffit and the

default properties.

Elevation to 4 inches, and click OK.

2 In the Default Profile Polyline Properties dialog box:

24 Select all four profile polylines on the longitude tendon

parameters layer along lines C/B.8, B, and A.

• Set Elevation to 5 inches. 3 Turn off Snap Orthogonal (

25 Choose the Generate Span Polylines tool (

).

).

26 Set the Elevation to 1.25 inches and the Span Orientation


• Click at the intersection of the slab edge with line B.8 near line 1. • Click at the center of the column at B.8-1.

Angle to 90 degrees, and click OK. 27 Choose the Generate Tendons tool (

) and inspect the generated tendons on the Generated Latitude Tendon and Generated Longitude Tendon layers.

• Click at the center of the column at C-2. • Right click and select Enter. 5 Draw a profile polyline:

• Click at the intersection of the slab edge with line B near line 1. • Click at the center of the column at B-2. • Right click and select Enter. 6 Draw a profile polyline:

• Click at the intersection of the slab edge with line A near line 1. • Click at the center of the column at A-2. • Right click and select Enter. 7 Choose the Move tool (

).

8 Hold down the shift key, click anywhere on the plan, and

type r0,-0.75. 9 Select the profile polyline between B-1 and B-2. 10 Right click and choose Selection Properties.

Figure 42-13 Longitude Tendon Parameters: Standard Plan

11 Change the elevation to 1.25 inches. 12 Select the profile polyline between B.8-1 and C-2. 13 Turn on Snap Nearest Snapable Point ( 14 Choose the Stretch tool (

).

).

15 Stretch the end of the profile polyline at C-2 to approxi-

matley mid way between lines 1 and 2. 16 Right click and choose Selection Properties. 17 Change the Elevation Reference to Above Soffit and the

Elevation to 6 inches, and click OK. 18 Choose the Profile Polyline tool (

).

).


• Click at the end of the profile polyline point stretched to mid way between lines 1 and 2. • Click at the center of the column at C-2. • Right click and select Enter.

RAM Concept

Design strips are an essential part of RAM Concept because they link finite element analysis with concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for section design. There are two directions called Latitude and Longitude.

).

19 Turn off Snap Nearest Snapable Point ( 20 Turn on Snap to Point (

42.5 Create the design strips

Generate the latitude spans:

1 Choose Layers > Design Strips > Latitude Design Spans


).

The Default Span Properties dialog box opens to the Strip Generation properties. 3 Click the General tab.

249

Chapter 42 4 Change Environment to Class U (corrosive).

The design strips appear in the latitude direction.

Note: This actually has no effect because ACI 318 requires two-way post-tensioned slabs to be designed as class U. Note: The Consider as Post-Tensioned box is already checked in the ACI 318 template. 5 Click the Column Strip tab. 6 Set Cross Section Trimming to Max Rectangle. 7 Change CS Top Cover to 1 inch. 8 Change CS Code Min. Reinforcement Location to

Elevated Slab. 9 Click OK. 10 Click the Generate Spans tool (


Generate Spans. The Generate Spans dialog box opens with Spans to Generate set to Latitude. 11 Set Minimum Span Length to 2 feet and click OK.

The span segments appear in the latitude direction.

Figure 42-15 Latitude design strips (with hatching turned on). Some editing is now required.

Concept uses imperfect algorithms that do not always produce acceptable span segments and span segment strips, as shown in Figures 42-16 through 42-18. You can make corrections with a number of tools You can see this more easily if the strip hatching is turned on. Hatch the strips:


).

The Visible Objects dialog box will appear. 2 Check Hatching under Latitude Span Segment Strips, and

click OK.


Figure 42-14 Design Strip: Latitude Design Spans Plan.

Two span segments are skewed. How you treat skewed strips is often a subjective matter, but in this tutorial we suggest one strip is straightened and the other edited in a different manner. Generate the latitude strips:



Figure 42-16 Skewed span segment that snapped to end of wall

Generate Strips. Straighten a span segment:

1 Select span segment 4-2 (between the wall and grid D3),

as shown in Figure 42-16.

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RAM Concept

Chapter 42 2 Turn on Snap to Intersection ( 3 Select the Rotate tool (

).

2 Click at the intersection of Grid B and Grid C design

strips near Grid 3 (point A in Figure 42-18).

).

4 Click at the end of the span segment at grid D3.

3 Click to the right of the slab edge (point B).

5 Click at the end of the span segment at the wall.

4 Right-click, and click enter.

The command line prompts Enter rotation end angle.

Regenerate the latitude span strips:

6 Enter 180 and press Enter.


).

The selected span segment is now horizontal.

The two edited spans produce improved span strips, as shown in Figure 42-19.

Figure 42-17 Diagonal strip that warrants manual improvement. Edit the span cross section orientation:

1 Select span segment 3-1 as shown in Figure 42-17. 2 Select the Orient Span Cross Section tool ( 3 Turn on Snap Orthogonal (

).

).

4 Click near the diagonal span strip and then again above

or below the first click. The orientation line half way along the span strip is now “vertical”.

Figure 42-19 Design Strip: Latitude Design Strips Plan after strip regeneration. Generate the longitude spans:

1 Choose Layers > Design Strips > Longitude Design

Spans Plan. 2 Double click the Span Segment tool (

).

3 Click the Column Strip tab.

The defaults set up in the Latitude Design Spans Plan will have remained the same. Since the cover cannot be the same for both directions, change it for the longitudinal direction. • Change CS Top Cover to 1.63 inches. • Change CS Bottom Cover to 1.25. • Click OK. 4 Click the Generate Spans tool (


Generate Spans.

Figure 42-18 Design strip with excessive width.

5 In the Generate Spans dialog box: Draw a Span Boundary Polyline:

1 Select the Span Boundary Polyline tool (

• Set Spans to Generate to Longitude. ). • Click the “up-down” orientation button tool ( ).

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251

Chapter 42 • Click OK.

Edit the span cross section orientation:

The spans appear in the longitude direction, as shown in Figure 42-20. One span segment on grid 2 is slightly skewed due to the column wall detail at C2. Another span segment overlays a wall and is unnecessary since the slab is continuously supported (see “Drawing design strips near walls” on page 113 for discussion).

1 Select the diagonal span segment between B-5 and C-4. 2 Select the Orient Span Cross Section tool ( 3 Turn on Snap Orthogonal (

).

).

4 Click near the diagonal span strip and then again to the

left or right of the first click. The orientation line half way along the span strip is now “horizontal”. Generate the longitude strips:



Generate Strips. The design strips appear in the longitude direction.

Figure 42-20 Design Strip: Longitude Design Spans Plan. Straighten a span segment:

1 Select the span segment between grid B2 and C2 (the

highlighted span segment in Figure 42-20). 2 Turn on Snap to Intersection ( 3 Select the Rotate tool (

).

).

Figure 42-21 Design Strip: Longitude Design Spans Plan after strip generation.

4 Click at the end of the span segment at grid B2. 5 Click at the end of the span segment at the wall.

Check for punching shear:

1 Choose Layers > Design Strip > Punching Checks Plan.


2 Double click the Punching Shear Check tool (

).



The selected span segment is now vertical.

box:

Delete the span segment over the wall:

• Change Cover to CGS to 1.63 inches (cover to centroid of top reinforcement).

1 Select the span segment that overlays the wall, and press

• Click OK.

Delete.

252

4 Fence the slab with the Punching Shear Check tool.

RAM Concept

Chapter 42 Regenerate the mesh:


).

2 Enter Element Size of 2.5 feet and click Generate.

There is now a better mesh. View the mesh on the Element: Standard Plan.

Figure 42-22 Design Strip: Punching Checks Plan.

42.6 Regenerate the mesh The presence of design strips can significantly improve the regularity of the finite element mesh. We recommend that once you have completed the design strips, you regenerate the mesh.

RAM Concept

Figure 42-23 Element: Standard Plan after regeneration.

253

Chapter 42

42.7 Calculate and view the results After you run the model, you can view the results of the analysis and design calculations.

The problem is that the cross sections are trimmed with the Max Rectangle setting. For span segment 6-2, that setting is causing a problem because of the combination of the drop cap and thinner balcony slab. Edit span segment 6-2:

Review Calc Options:


1 Choose > Criteria > Calc Options

Spans Plan.

2 Review the options, and click OK.


Note: See “Calculating the results” on page 149 of

3 Check the Numbers box under Longitude Span

Chapter 28 for more information.

Segments, and click OK. 4 Select span segment 6-2.

Calculate:

1 Click Calc All (

).


An error message appears concerning a problem with a tendon out of the slab in strip 6C-2.


from the popup menu. 6 Click the Column Strip tab. 7 Change CS Cross Section Trimming to Inverted T or L,

2 Click Continue three times to clear the error message.

and click OK.

The source of the error messages must be investigated.

Recalculate:

1 Click Calc All (

View the design strips with tendons:

1 Choose Layers > Design Strips > Longitude Cross

Sections Perspective. 2 Choose View > Visible Objects (

).


Concept completes the calculations without errors. See “Cross Section Trimming” on page 105 for a thorough explanation of Cross Section trimming.

3 Click the Tendons tab. 4 Select the Longitude Tendons layer, check Tendons, and click OK.

42.7.1 Design status

5 Use the Rotate about X and Y axes tool (

Look at design status:

) and the Zoom Rectangle ( ) tool to view the problem location shown in Figure 42-24 and Figure 42-25.


Figure 42-24 Longitude Cross Sections Perspective with longitude tendons visible.

Figure 42-26 Design Status: Status Plan.

Figure 42-25 Rotation and zoom-in of the problem location in Figure 4224.

254

This shows OK for all design strips. This means that there are no violations of code limits for ductility, flexural stress and one-way shear. Note that status does not flag excessive deflections.

RAM Concept

Chapter 42 There are punching shear status results at each column. You can see these more easily on the dedicated punching plan. 2 Choose Layers > Design Status > Punching Shear Status

Plan. Concept has noted “Non-standard section” at six column locations and “OK with SSR” at one column. “Non-standard Section” is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three ACI 318-05 cases: interior, edge and corner. Concept still calculates a stress ratio for nonstandard sections. Refer to “Non-Standard Sections: ACI 318 and CSA A23.3” on page 162 of Chapter 29 for more information. Where the unreinforced stress ratio (USR) is less than 1.0, the column’s punching shear is satisfactory without any reinforcement (subject to the comments above concerning “Non-standard section)). Stud shear reinforcement is required where Concept reports “OK with SSR”. If Concept reports “Failed” then SSR does not solve the problem and a thickening is required.

Note: Choose > Layers > Design Status > SSR Plan to view the stud shear reinforcement.

Figure 42-28 Design Status: Reinforcement Plan.

This shows all the code-determined reinforcement for each of the design strips. Since the slab is post-tensioned, there is not much reinforcement. You might choose to view all design reinforcement on the one plan, or you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom) and direction (latitude or longitude). 2 Choose the plans that best convey the results without too

much clutter.

Figure 42-27 Design Status: Punching Shear Status Plan.

42.7.2 Design reinforcement Look at design reinforcement:


RAM Concept

Figure 42-29 Design Status: Latitude Bottom Reinforcement Plan.

The Reinforcement layer plans show detailed reinforcement. In particular, the top bars are rationalized so that the number is consistent each side of columns.

255

Chapter 42 • Click OK

Look at detailed top reinforcement:

Choose Layers > Reinforcement > Top Bars Plan.

Figure 42-31 Service Design: Top Stress Plan.

Figure 42-30 Reinforcement: Top Bars Plan

To view the Max Demand more easily you can uncheck Max Capacity in the plot options.

42.7.3 Concrete stresses ACI 318-05 has limits for the hypothetical stresses due to flexure and axial loads. The code bases the rules upon “averaging” rather than peak values.

Similarly, you can view the bottom stress plan at Layers > Rule Set Designs > Service Design > Bottom Stress Plan.

Stress contour plots of the net flexural stresses are available in Concept. Most designers will not be interested in these plots because, in following the code, Concept does not use the contours directly in design.

42.7.4 Deflection

What will likely be of interest are the plans that show the concrete stresses plotted along the design strips. These are the average stresses based upon the design strip widths.


Top Stress Plan. 3 In the Plot Settings dialog box:

• Change Max Frame # to 4.

Calculate Load History Deflections:

1 Click Calc Load History Deflections (

), or choose

Process > Calc Load History Deflections.

View top stress plan:

2 Right click over the plan and choose Plot (

Usually you are interested in short-term and long-term deflections. Load history deflections can be used to evaluate both.

).

The Maximum Short Term Load, Sustained Load, and Final Instantaneous Load History Deflection Layers provide contour plans for deflection. View maximum short term load deflection:

1 Choose Layers > Load History Deflections> Maximum

Short Term Load> Std Deflection Plan.

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RAM Concept

Chapter 42

42.7.5 Bending Moments While it is not necessary to view bending moments, it can be useful, especially for irregular structures. Even though principal moments are important, the default moment contours plans are for Mx (moment about the x-axis) and My. This is because most designers detail reinforcement orthogonally, and the directions are usually the x- and yaxes. You can view moments about any axes, including the principal axes. It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful. View Factored LC Moments:

1 Choose Layers > Load Combinations > Factored LC:

1.2D + 1.6L + 0.5Lr > Mx Plan. The Mx contours should be visible. 2 Turn on Snap Orthogonal (

)

3 Click the Selected Plot Distribution tool ( Figure 42-32 Maximum Short Term Load: Deflection Plan.

).

4 Click first at grid intersection B-3, and then click at grid

intersection D-3. 2 Right click over the plan and choose Plot (

) to change


This shows the bending moment shape along the line you have drawn.

View sustained deflection:

5 While pressing the Shift key, click at grid intersection B-

1 Choose Layers > Load History Deflections> Sustained

1, and then click at grid intersection B-3.

Load> Std Deflection Plan.

This shows how Mx varies across the panel, and highlights the approximate nature of the ACI318-05 post-tension design method. See “Section distribution plots” on page 158 for more information.

Figure 42-33 Sustained Load: Deflection Plan.

Figure 42-34 Factored LC: 1.2D + 1.6L + 0.5Lr: Mx Plan showing use of Plot Distribution tool.

RAM Concept

257

Chapter 42 View the balanced load percentages:

3 Choose “Balanced Load Percentages” in the Visible


Objects dialog box and click OK.

Plan 2 Choose View > Visible Objects (

258

).

See “Calculating the balanced load percentages” on page 389 for more information.

RAM Concept

Chapter 43

43 PT Flat Plate Tutorial: AS3600-2001 This chapter describes the steps for modeling a posttensioned two-way flat plate with uniform loads. The objective of this tutorial is to build on the skills learned in the Chapter 41 RC tutorial and introduce new steps, such as using a CAD drawing and post-tensioning. Some tools and methods described in the RC tutorial are not used here. As such, it is highly recommended that you first do the RC tutorial. This is not a particularly “aggressive” design. After you have completed the tutorial, you may wish to make the slab thinner to investigate the ramifications.

Draw the slab area:


(

) and Snap to Point

).




• Choose a Concrete Strength of 32 MPa. • Set Thickness to 250 mm. • Leave Surface Elevation as 0 and Priority as 1. • Click OK.





Note: There are two vertices near each other near B-5 at 26.05, 8.2 m and 26.05, 8.8 m. Cursor plan coordinates display next to the command prompt. 5 Complete the polygon by clicking at your starting point




1 Choose File > Import Drawing. 2 Select the CAD drawing file flat_plate_metric.dwg.

The File Units dialog box appears. 3 Select Millimeters (the units used in the CAD file) and

click OK.



).






properties.




• Change Thickness to 200 mm. • Change Surface Elevation to -50 mm. • Change the Priority to 2, and click OK.

RAM Concept

259



Draw the opening:


).







• Change Thickness to 500 mm.




• Click OK.


).




OK.




), select (by double-clicking) and delete the drop cap at B-2. 6 Click Redraw (

3 Check “Hatching” under “Slab Openings”, and then click


). Define the column locations and properties:


) and press

down on the left mouse button for one second. A pop-up menu appears. 8 Select the Drop Cap tool from the menu.


).


• Choose a Concrete Strength of 32 MPa. • Set Width to 600 mm. • Set Depth/Diameter to 600 mm. 3 Click OK. 4 Click at the center of all 13 column locations shown on

The selected tool becomes current for that button. 9 Click at the column at B-2.

the imported drawing. Define the wall location and properties:

A Drop Cap Tool dialog box appears.


10 Enter an angle of zero degrees.


11 Enter a side dimension of 1.2 m and click OK.


). ).

• Choose a Concrete Strength of 20 MPa.

260

RAM Concept

Chapter 43 4 Click OK.


5 Define the wall by clicking at the start and end points, on

1 m.

the centerline:

3 Click Generate.

• Place the cursor near 8.825, 26.3 m and it will snap to where the center of the wall intersects the edge of the slab, and click. • Place the cursor at the center of the column at C-2 (it will snap orthogonally) and click. You have now defined the structure but the element mesh does not yet exist.

View the mesh:



6 Go to “Generate the mesh:”, or try the next method. 7 The wall should be highlighted as it is the current


).


) and press down





) to rotate the


).


).



). Figure 43-6 Element: Structure Summary Perspective.

RAM Concept

261

Chapter 43






).


• Change Fz to 2 kN/m2 and click OK. This tool will now draw area loads of 2 kN/ m2. 4 Define an area load over the entire slab by clicking four



).


balcony (and then type “c”). In this situation, it is best for the load to match the balcony’s dimensions. You have drawn another 2 kN/m2 load. This load should be highlighted as it is the current selection. If not, select it before proceeding by double-clicking with the selection tool. 3 Choose Edit > Selection Properties, or right-click and

Define the other dead loading:



choose Selection Properties. 4 In the dialog box, change Fz to 3 kN/ m2 and click OK.

There is now a total live load on the balcony of 5 kN/ m2.

Note: You could have drawn the 3 kN/

Figure 43-8 Live (Reducible) Loading: All Loads Plan (with area loads hatching turned on).

m2

load by first changing the area load default properties and then using the tool.




), select the “blanket” load

by fencing the entire area. 7 Right click on the plan and choose Selection Properties

from the popup menu. 8 In the Properties dialog box, change Fz to 1 kN/ m2, and

click OK.

262

RAM Concept



from the popup menu. 11 In the Properties dialog box, change Fz to -1 kN/ m2, and



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Chapter 43


• Set Tendon Spacing to Equal. • Set Spacing to 2 m, and click OK.

Post-tensioning methodology varies from country to country. In Australia, engineers use column and middle strips for post-tensioned flat plate design, and, generally, detail (bonded) tendons in both the column and middle strips.


10 With the Full Span Tendon Panel tool (

• Click at the center of the column at grid intersection B-1. • Click at the center of the column at B-2. • Click at the center of the column at C-2. • Click at the grid intersection C-1. 11 In the Tendon Panel dialog box:

Note: The tutorial in Chapter 49 explains the use of Strip


Wizard to establish an estimate of the number of strands required for the critical band.

• Set Spacing to 2 m,

Note: For use of the tendon parameters layers as an alternative and perhaps quicker means of defining prestressing, please refer to “PT Flat Plate Tutorial: ACI 318-08” on page 239. Define the manual latitude tendons:

• Check Skip start tendon, and click OK. 12 With the Full-Span Tendon Panel tool (

) selected,

draw tendons in the next two panels: • Click at the center of the column at grid intersection A-2. • Click at the center of the column at A-3.

1 Choose Layers > Latitude Prestressing > Latitude


Tendon > Standard Plan. 2 Choose View > Visible Objects (

) selected,



).


3 Click the Drawing Import tab. 4 Click Show All, and then click OK.


Showing the CAD file makes the following instructions easier to follow.

• Uncheck Skip start tendon, and click OK. 14 Turn off Snap Orthogonal (

5 Double click the Full Span Tendon Panel tool (


) to

6 In the Default Tendon Properties dialog box:


• Click at the center of the column at grid intersection B-3. • Click at the center of the column at B-5.

• Set Profile at end 1 to 212 mm. • Set Profile at end 2 to 38 mm, and click OK.

Note: The 25 mm cover to the 19 mm high duct (containing 12.7 mm diameter strand) determines these profiles. ) and Snap Orthogonal

• Click at the center of the column at C-4. • Click at the center of the column at C-3. 16 In the Tendon Panel dialog box:

• Set Auto Connect, and click OK. 17 With the Full-Span Tendon Panel tool (

(

) selected,


).


) selected,






• Click at grid intersection D-2.

• Click at the center of the column at B-2. • Click at the center of the column at B-1. 9 In the Tendon Panel dialog box:

264

) selected,


edit its default properties.


).

• Click at the center of the column at D-3.


• Set Tendon Spacing to Equal. • Set Spacing to 2 m.

RAM Concept

Chapter 43 • Check Skip start tendon, and click OK. 19 With the Full-Span Tendon Panel tool (


) selected,

mm and click OK. 34 With the Selection tool (

draw tendons in the next panel: • Click at the center of the column at grid intersection C-3.

), select all of the tendon segments that terminate over a drop cap, by: • Double clicking at grid intersection A-1.


• Hold the Shift key down and double click at A-3.


• Hold the Shift key down and double click at B-5.







mm and click OK.


Note: Auto-connect will ignore the tendons at the first click because there are already two tendon segments connected at that point. 21 With the Select Connected Tendons tool (

) selected,

double-click the tendon on grid B.

centroid of the 250 mm slab, rather than the centroid of the drop cap. 37 With the Selection tool (






23 In the Properties dialog box, change Strands Per Tendon

to 10, and click OK. 24 With the Select Connected Tendons tool (

Note: This sets the tendon anchorage profile to the


) selected,

double-click the tendon directly above grid B. 25 Hold down shift and double-click the tendon directly

below grid B. 26 Right click on the plan and choose Selection Properties

from the popup menu. 27 In the Properties dialog box, change Strands Per Tendon

to 5, and click OK. The latitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab. 28 With the Selection tool (

), select all of the terminated tendon segments, other than those over a drop cap or within the balcony slab: • Fence the tendon segments that end on grid 1. • Hold the Shift key down and repeat the procedure until you have selected all applicable end tendon segments (tendon segments terminating at grids 2, 3, 4 and 5). 29 Right click on the plan and choose Selection Properties



segment at C-2. 41 Hold down the Shift key, and double click the tendon

segment immediately below (profile point at (9,15.7)). 42 Right click on the plan and choose Selection Properties


mm and click OK.



between D-2 and D-3. 45 Click the Calc Profile tool (

).

The Calc Tendon Profile dialog box appears and reports the current balance load is -5.67 kN/m. If this is not the number then you probably selected only one tendon segment. 46 Click Cancel. 47 With the Selection tool (



).

49 Input the desired balance load as -6 kN/m in the Calc

Tendon Profile dialog box and click Calc.

mm and click OK.

The low point (end 2) adjusts to 126 mm.


), double click the tendon segment above B.8-1 that terminates within the 200 mm balcony slab.






from the popup menu. RAM Concept

265

Chapter 43 52 In the Properties dialog box, set Profile at end 2 to 125


mm and click OK.


Note: These steps first used the Calc Profile tool to determine a low point that produces a similar average uplift in an end span as the adjacent span, and then manually changed the low points for practical reasons. Finally, you need to adjust the tendon that goes through the opening. 53 Turn on Snap Nearest Snapable Point (

Orthogonal (

) and Snap

) selected,

• Click at the center of the column at grid intersection A-1. • Click at the center of the column at B-1. • Click at the center of the column at B-2. • Click at the center of the column at A-2. 4 In the Tendon Panel dialog box:


).




) selected,





• Click at the center of the column at B.8-1.

mm and click OK.



57 Choose the Stretch tool (

).


58 With the one tendon segment selected, stretch the profile

point at grid 3 to the other side of the opening.

Note: The Snap Nearest Snapable Point snaps the cursor to the edge of the opening.



Orthogonal (

) and Snap

).


) selected,

draw tendons in the balcony: • Click at the center of the column at grid intersection B.8-1. • Click at the edge of the slab at 0, 17.8 m. • Click at the tendon profile point at 7.2, 17.1 m.

Note: The snap orthogonal snaps the cursor to 7.2, 17.8 m. • Click at the tendon profile point at 7.2, 17.1 m. 9 In the Tendon Panel dialog box:



mm and Profile at end 2 to 100 mm, and click OK. 12 With the Selection tool ( Figure 43-10 Manual Latitude Tendon: Standard Plan.


Define the longitude tendons:


Longitude Tendon > Standard Plan. remain the same. Strictly speaking, you should adjust Profile at end 1 at columns (to avoid a clash with latitude tendons) but you can ignore for this tutorial.

266


mm, and click OK.

Note: The defaults set up in the Latitude Tendon Plan


), select the two shortest of the half-span (cantilever) tendon segments.

Note: This makes the short tendon segments flat. 15 With the Full-Span Tendon Panel tool (

) selected,


). RAM Concept

Chapter 43 • Click at the center of the column at grid intersection A-2. • Click at the center of the column at B-2. • Click at the center of the column at B-3. • Click at the center of the column at A-3.


) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection C-3. • Click at the center of the column at D-3. • Click at the center of the column at D-4.





• Set Spacing to 2 m. • Check Skip start tendon, and click OK. 17 With the Full-Span Tendon Panel tool (

) selected,











), select the second tendon in

this panel.


26 Hold down shift and select the fifth tendon, and press



) selected,


Delete.


Note: This sequence is anti-clockwise.

) selected,

draw tendons that terminate in this panel: ).


• Click at the profile point at 19, 17.5 m.


• Click at the last tendon profile point at 22, 17.5 m.

• Enter 9.25, 26, and press Enter. • Turn off Snap Orthogonal (

• Type r0,2.1.

Note: The snap orthogonal snaps the cursor to 22, 19.6 m. • Click at the last tendon profile point at 22, 17.5 m.

).


• Set Auto Connect, and click OK.



• Set Auto Connect. • Uncheck Skip Start Tendon, and click OK. 21 With the Full-Span Tendon Panel tool (


) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection B-3. • Click at the center of the column at C-3.


mm, and click OK. 31 With the Select Connected Tendons tool (

) selected,

double-click the tendon on grid 2. 32 Right click on the plan and choose Selection Properties





to 10, and click OK.


• Set Layout to Splayed. • Set Tendon Spacing to Equal.

34 With the Select Connected Tendons tool (

) selected, double-click the tendon directly to the left of grid 2. 35 Hold down shift and double-click the tendon directly to

the right of grid 2.

• Set Spacing to 1.8 m.




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267

Chapter 43 37 In the Properties dialog box, change Strands Per Tendon

to 5, and click OK.


Note: You could cut down the number of steps in moving

The longitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab. 38 With the Selection tool (

), select all of the terminated tendon segments, other than those over a drop cap or within the balcony slab:

the tendon from the opening by using the Utility tool. This combines the selection tool with move and stretch. Refer to “Expanding tool buttons” on page 6 and “Using the Utility tool to move and stretch” on page 20 for further information.

• Fence the tendon segments that end on grid A. • Hold the Shift key down and repeat the procedure until you have selected all applicable end tendon segments (tendon segments terminating at grids B and D). 39 Right click on the plan and choose Selection Properties





Figure 43-11 Manual Longitude Tendon: Standard Plan.

mm, and click OK.

Note: This sets the tendon anchorage profile to the centroid of the 250 mm slab, rather than the centroid of the drop cap. 44 With the Selection tool (




43.5 Create the design strips Design strips are an essential part of RAM Concept because they link finite element analysis with concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for section design. There are two directions called Latitude and Longitude.

mm and click OK. Finally, you need to move the tendon that goes through the opening. 47 With the Selection tool (



Plan.


2 Double click the Span Segment tool (


The Default Span Properties dialog box opens to the Strip Generation properties.

).

49 Click anywhere on the plan, and type r-.5,0. 50 With the Selection tool (



3 Click the General tab. 4 Change Environment to Protected.

).


the moved tendon.

).

Note: This setting often has a significant effect on reinforcement quantities.

Note: The Consider as Post-Tensioned box is already checked in the AS3600 template.

268

RAM Concept

Chapter 43 5 Click the Column Strip tab. 6 Set Cross Section Trimming to Max Rectangle. 7 Change CS Top Cover to 25 mm. 8 Click the Middle Strip tab. 9 Check the Middle Strip uses Column Strip Properties

box. 10 Click OK. 11 Click the Generate Spans tool (


Generate Spans. The Generate Spans dialog box opens with Spans to Generate set to Latitude. Accept the Minimum Span Length as 0.5 meters. 12 Click OK.

The span segments appear in the latitude direction. Figure 43-13 Latitude design strips (with hatching turned on). Some editing is now required.

Concept uses imperfect algorithms that do not always produce acceptable span segments and span segment strips, as shown in Figures 43-14 through 43-17. You can make corrections with a number of tools. You can see this more easily if the strip hatching is turned on. Hatch the strips:


).


click OK. Figure 43-12 Design Strip: Latitude Design Spans Plan.





Generate Strips. The design strips appear in the latitude direction. Figure 43-14 Skewed span segment that snapped to end of wall Straighten a span segment:

1 Select the span segment between the wall and grid D3 (as

shown in Figure 43-14). 2 Turn on Snap to Intersection (

RAM Concept

).

269

Chapter 43 3 Select the Rotate tool (

).


4 Click at the end of the span segment at grid D3. 5 Click at the end of the span segment at the wall.

4 Right-click, and click enter. Regenerate the latitude span strips:




The three edited spans produce improved span strips. There is one more to edit.


).


1 Select the diagonal span strip as shown in Figure 43-15. 2 Select the Orient Span Cross Section tool ( 3 Turn on Snap Orthogonal (

).

).

Figure 43-17 Span segment C-2 to C-3. Draw a Span Boundary Polyline:



or below the first click.

).



The orientation line half way along the span strip is now “vertical”.

3 Click at point B. 4 Right-click, and click enter. 5 Click at point C. 6 Click at point D. 7 Right-click, and click enter. 8 Select the Strip Boundary Polyline tool(

).

9 Click at point E as shown in Figure 43-17. 10 Click at point F, to the right of the opening. 11 Right-click, and click enter. 12 Select the span segment (between grid C2 and C3). 13 Right click on the plan and choose Selection Properties

from the popup menu. 14 In the Properties dialog box, change Span Width Calc to

Manual. 15 Uncheck Detect Supports Automatically. 16 Change Support Width at End 2 from 600 to 610 mm, and Figure 43-16 Design strip with excessive width.

click OK.

Draw a Span Boundary Polyline:

This ensures that the first (design strip) cross section passes through the opening, and hence uses less concrete section.


).


17 Click the Generate Selected Strips tool (

).

strips near Grid 3 (point A in Figure 43-16). 270

RAM Concept

Chapter 43 The edited spans produce improved span strips, as shown in Figure 43-18.

Figure 43-19 Design Strip: Longitude Design Spans Plan.

Figure 43-18 Design Strip: Latitude Design Strips Plan after regeneration. Generate the longitude spans:


Spans Plan.

Straighten a span segment:


).

1 Select the span segment between grid B2 and C2

(highlighted in Figure 43-19).


The defaults set up in the Latitude Design Spans Plan will have remained the same. Since the cover cannot be the same for both directions, change it for the longitudinal direction. • Change CS Top Cover to 41 mm. • Change CS Bottom Cover to 37 mm. • Click OK. 4 Click the Generate Spans tool (

One span segment on grid 2 is slightly skewed due to the column wall detail at C2. Another span segment overlays a wall and is unnecessary since the slab is continuously supported (see “Drawing design strips near walls” on page 113 for discussion).




2 Turn on Snap to Intersection ( 3 Select the Rotate tool (

).


The command line prompts Enter rotation end angle. 6 Enter 90 and press Enter.

The selected span segment is now vertical. Delete the span segment over the wall:

1 Select the span segment that overlays the wall. 2 Press Delete.

• Click the “up-down” orientation button tool ( ).

Generate the longitude strips:

• Click OK.


The spans appear in the longitude direction.

).



RAM Concept

271

Chapter 43 8 Click at point C and D. 9 Right-click, and click enter. 10 Select the Strip Boundary Polyline tool(

).

11 Click at point E as shown in Figure 43-21. 12 Click at point F (the corner of the opening) and point G

(another corner). 13 Right-click, and click enter. 14 Select the span segment between grid B3 and C3. 15 Click the Generate Selected Strips tool (

).


1 Select the diagonal span strip between B-5 and C-4. 2 Select the Orient Span Cross Section tool ( 3 Turn on Snap Orthogonal (

).

).


left or right of the first click. Figure 43-20 Design Strip: Longitude Design Spans Plan after strip generation.

The area to the left of the opening has no design strip. You can use the tools to locate a middle strip in that area.

The orientation line half way along the span strip is now “horizontal”. 5 Click the Generate Selected Strips tool (

).

The new design strips appear, as shown in Figure 43-22.

Figure 43-21 Grid B3-C3 span segment and strips. Edit span segment with Span Boundaries and Strip Boundaries


highlighted line in Figure 43-20).

Figure 43-22 Design Strip: Longitude Design Spans Plan after editing.



Note: Some of the latitude and longitude design strips

3 Change Span Width Calc to Manual, and click OK.

(span segment strips) have different widths either side of a column. You could rationalize these strips such that they have similar widths at the column, especially the cantilever. See the discussion in “Defining strip boundaries manually” on page 102 of Chapter 22, “Defining Design Strips”. In particular, Example 22-2 on page 103 and Example 22-4 on page 104.

4 Select the Span Boundary Polyline tool ( 5 Click at point A as shown in Figure 43-21. 6 Click at point B. 7 Right-click, and click enter.

272

).

RAM Concept

Chapter 43

43.6 Regenerate the mesh



).


box: • Change Cover to CGS to 41 mm (cover to centroid of top reinforcement). • Click OK. 4 Fence the slab with the Punching Shear Check tool.

The presence of design strips can significantly improve the regularity of the finite element mesh. We recommend that once you have completed the design strips, you regenerate the mesh. Regenerate the mesh:


).

2 Enter Element Size of 0.75 m and click Generate.



RAM Concept


273

Chapter 43

43.7 Calculate and view the results After you run the model, you can view the results of the analysis and design calculations. Review Calc Options:

1 Choose > Criteria > Calc Options 2 Review the options, and click OK.

Note: See “Calculating the results” on page 149 of Chapter 28 for more information.


Calculate:

1 Click Calc All (


An error message appears twice concerning a problem with a tendon out of the slab in strip 6C-2.

The problem is that the cross sections are trimmed with the Max Rectangle setting. For span segment 6-2, that setting is causing a problem because of the combination of the drop cap and thinner balcony slab.

2 Click Continue twice to clear the error message.

The source of the tendon error messages must be investigated. Two more errors appear to do with reinforcement detailing. 3 Click Continue twice to clear the reinforcement error

messages.

Edit span segment 6-2:


Spans Plan. 2 Choose View > Visible Objects (

).


Segments, and click OK.


4 Select span segment 6-2.




).

3 Click the Tendons tab. 4 Select the Longitude Tendons layer, check Tendons, and


and click OK.

click OK.

Edit span segment 2-3:





).

3 Check the Numbers box under Latitude Span Segments,

and click OK. 4 Select span segment 2-3. 5 Right click on the plan and choose Selection Properties

from the popup menu. 6 Click the Column Strip tab. 7 Change CS Cross Section Trimming to None. Figure 43-25 Longitude Cross Sections Perspective with longitude tendons visible.

8 Change CS Inter Cross Section Slope Limit to 0. 9 Click the Middle Strip tab. 10 Uncheck the Middle Strip uses Column Strip Properties

box. 11 Change MS Top Cover to 25 mm. 12 Change MS Span Detailer to None, and click OK.

274

RAM Concept

Chapter 43 The above changes are made to eliminate the reinforcement warnings. In a proper design you should investigate this further. Recalculate:

1 Click Calc All (


Concept completes the calculatons without errors.

Note: See “Cross Section Trimming” on page 105 for a thorough explanation of Cross Section trimming.

43.7.1 Design status Look at design status:



Plan. You can see that ten columns have an unreinforced stress ratio (USR) of less than 1.0. Two columns report “OK with SSR” which means stud shear reinforcement is required. One column fails in punching. SSR does not solve the problem. A thickening is required. Concept has noted “Non-standard section” at five column locations. “Non-standard Section” is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three cases: interior, edge and corner. Concept still calculates a stress ratio for nonstandard sections. Refer to “Non-Standard Sections: AS3600, BS8110, EC2 and IS 456” on page 162 of Chapter 29 for more information. Where the unreinforced stress ratio (USR) is less than 1.0, the column’s punching shear is satisfactory without any reinforcement (subject to the comments above concerning “Non-standard section)). Stud shear reinforcement is required where Concept reports “OK with SSR”.



This shows OK for all design strips. This means that there are no violations of code limits for ductility or one-way shear. Note that status does not flag excessive deflections. There are punching shear status results at each column. You can see these more easily on the dedicated punching plan. Figure 43-28 Design Status: Punching Shear Status Plan.

RAM Concept

275

Chapter 43


43.7.3 Deflection

Look at design reinforcement:

Usually you are interested in short-term and long-term deflections. Load history deflections can be used to evaluate both.


Calculate Load History Deflections:


), or choose

Process > Calc Load History Deflections. The Maximum Short Term Load, Sustained Load, and Final Instantaneous Load History Deflection Layers provide contour plans for deflection. View maximum short term load deflection:




This shows all the code-determined reinforcement for each of the design strips. You might choose to view all design reinforcement on the one plan, or you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom) and direction (latitude or longitude). 2 Choose the plans that best convey the results without too

much clutter.

Figure 43-31 Maximum Short Term Load: Deflection Plan.


) to change

Plot Type from Color Contour to Contour. View sustained deflection:




276

RAM Concept

Chapter 43 4 Click first at grid intersection B-3, and then click at grid

intersection D-3. This shows the bending moment shape along the line you have drawn. 5 While pressing the Shift key, click at grid intersection B-

1, and then click at grid intersection B-3. This shows how Mx varies across the panel, and highlights the different column and middle strip moments. See “Section distribution plots” on page 158 for more information.


43.7.4 Bending Moments While it is not necessary to view bending moments, it can be useful, especially for irregular structures. Even though principal moments are important, the default moment contours plans are for Mx (moment about the x-axis) and My. This is because most designers detail reinforcement orthogonally, and the directions are usually the x- and yaxes. You can view moments about any axes, including the principal axes.

Figure 43-33 Ultimate LC: 1.2D + 1.5L Mx Plan showing use of Plot Distribution tool.

It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful.

View the balanced load percentages:

1 Choose Layers > Design Strips > Latitude Design Strips View Factored LC Moments:

Plan

1 Choose Layers > Load Combinations > Ultimate LC:


1.2D + 1.5L > Mx Plan.

).


The Mx contours should be visible.




)


RAM Concept

).

277

Chapter 43

278

RAM Concept

Chapter 44

44 PT Flat Plate Tutorial: BS8110 / TR43 This chapter describes the steps for modeling a posttensioned two-way flat plate with uniform loads. The objective of this tutorial is to build on the skills learned in the Chapter 41 RC tutorial and introduce new steps, such as using a CAD drawing and post-tensioning.

3 Click the Drawing Import tab. 4 Click Show All, and then click OK. Draw the slab area:


( Some tools and methods described in the RC tutorial are not used here. As such, it is highly recommended that you first do the RC tutorial.

) and Snap to Point

).




This is not a particularly “aggressive” design. After you have completed the tutorial, you may wish to make the slab thinner to investigate the ramifications. You could also use this as a reinforced concrete tutorial by making a few adjustments (for example, a thicker slab).

• Choose a Concrete Strength of C32/40. • Set Thickness to 250 mm. • Leave Surface Elevation as 0 and Priority as 1. • Click OK.

BS8110 does not cover post-tensioned flat plates, and refers the designer to “specialist literature”. The Concrete Society prepared Technical Report 43 for this purpose. RAM Concept currently uses the first edition of TR43.




26.05, 8.2 m and 26.05, 8.8 m. Cursor plan coordinates display next to the command prompt.

Note: There are two vertices near each other near B-5 at

5 Complete the polygon by clicking at your starting point


44.1 Import the CAD drawing The CAD file you import is located in your RAM Concept program directory Import the CAD file:



click OK.


Figure 44-1 The slab outline on the Mesh Input: Standard Plan.

1 Choose Layers > Mesh Input > Standard Plan.

Draw the balcony slab area:



).




• Change Thickness to 200 mm. RAM Concept

279

Chapter 44 11 Enter a side dimension of 1.2 m and click OK.

• Change Surface Elevation to -50 mm. • Change the Priority to 2, and click OK. 3 With the Slab Area tool (

) selected, define the six vertices of the balcony outline by clicking at each vertex, and then click at your starting point (or type “c” in the command line and press Return).

Draw the opening:


).






properties.

Figure 44-3 The opening on the Mesh Input: Standard Plan.

2 In the Default Slab Area Properties dialog box: Hatch the slab areas:

• Change Thickness to 500 mm. • Change Surface Elevation to 0, and leave the Priority as 2. • Click OK.


).

The Visible Objects dialog box will appear. 2 Check “Hatching” under “Slab Areas”.








).





) and press


).


• Choose a Concrete Strength of C32/40. • Set Width to 600 mm. • Set Depth/Diameter to 600 mm. 3 Click OK.




the imported drawing.

The selected tool becomes current for that button.


9 Click at the column at B-2.





). ).


• Choose a Concrete Strength of C20/25. 280

RAM Concept


View the mesh:



the centerline. • Place the cursor near 8.825, 26.3 m and it will snap to where the center of the wall intersects the edge of the slab, and click.


• Place the cursor at the center of the column at C-2 (it will snap orthogonally) and click. You have now defined the structure but the element mesh does not yet exist. 6 Go to “Generate the mesh:”, or try the next method. 7 The wall should be highlighted as it is the current


).


) and press down





) to rotate the


).


Figure 44-4 After defining the slab, the Mesh Input: Standard Plan shows the slab areas and opening (hatched), the columns and the wall.

).


Generate the mesh:


).

44.3 Define the loads


1 m. 3 Click Generate.

RAM Concept

RAM Concept calculates the concrete self-weight automatically.

281

Chapter 44 Concept uses superposition of loads. The easiest way to define areas with increased area loads is to draw a “blanket” area load over the entire floor, and then draw the additional loads. There is no limit to the number of loadings than can be specified. Define the typical live load:



).






).





Note: You could have drawn the 3 kN/ m2 load by first changing the area load default properties and then using the tool.










click OK. 282

RAM Concept






RAM Concept

283

Chapter 44



Post-tensioning methodology varies from country to country. In the USA it is common to use the “banding” technique for detailing tendons in two-way slabs. Banding means concentrating the tendons over support points in one direction, and distributing them uniformly in the orthogonal direction. This method is generally used in conjunction with full-panel design strips. That is, column and middle strips are not used.


In the United Kingdom, engineers are directed towards Technical Report 43 (BS8110 does not cover posttensioned flat plates) and that document encourages the use of full panel design strips with the banding technique. This method, with bonded tendons, is used in this tutorial.

• Click at the center of the column at A-3. • Right click, and then click Enter. 9 Turn on Snap Orthogonal (

).


) selected, draw a

tendon along grid D: • Click at the center of the column at grid intersection D-4. • Click at the center of the column at D-3. • Click at the corner of the slab near D-2. • Right click, and then click Enter.

Note: RAM Concept has two layers for tendons called

11 Turn off Snap Orthogonal (

latitude and longitude. Refer to “Using the latitude and longitude prestressing folders” on page 133 for more information.



Note: For use of the tendon parameters layers as an alternative and perhaps quicker means of defining prestressing, please refer to “PT Flat Plate Tutorial: ACI 318-08” on page 239.

). ) to edit its


• Set Strands per Tendon to 20, and click OK. 14 With the Tendon Polyline tool (

) selected, draw a

tendon along grid B: • Click at the center of the column at grid intersection B-1. • Click at the center of the column at B-2. • Click at the center of the column at B-3.

Define the latitude tendons:


• Click at the center of the column at B-5. • Right click, and then click Enter.



).

) selected, draw a



• Click at the center of the column at grid intersection B.8-1.




) to edit its


default properties.




• Set PT System to 12.9mm Bonded.


) selected,


• Set Strands per Tendon to 9. • Set Profile at end 1 to 212 mm. • Set Profile at end 2 to 38 mm, and click OK.



Note: The 25 mm cover to the 19 mm high duct (containing


12.9 mm diameter strand) determines these profiles.

The latitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab.

7 Turn Snap to Intersection (

).


tendon along grid A:

284

) selected, draw a


), select all of the terminated tendon segments, other than those over a drop cap, by:

RAM Concept

Chapter 44 • Double clicking at grid intersection B-1. • Hold the Shift key down and double click at B.81.


Tendon Profile dialog box and click Calc. The low point (end 2) adjusts to 126 mm.

• Hold the Shift key down and double click at C-4.


• Hold the Shift key down and double click at D-2.

tendons between grids 3 and 5.







mm and click OK.

mm and click OK.

Note: These steps first used the Calc Profile tool to


determine a low point that produces a similar average uplift in an end span as the adjacent span, and then manually changed the low points for practical reasons.



mm and click OK.







segment at C-2.







Longitude Tendon > Standard Plan.

mm and click OK.





).

The Calc Tendon Profile dialog box appears and reports the current balance load is -32.4 kN/m. If this is not the number then you probably selected only one tendon segment.



RAM Concept


).


) to




remain the same. Strictly speaking, you should adjust Profile at end 1 at columns (to avoid a clash with latitude tendons) but you can ignore for this tutorial.

).


) selected,

draw tendons in the bottom left panel: • Click at the center of the column at grid intersection A-1.

285

Chapter 44 • Click at the center of the column at B-1.









• Set Spacing to 2 m.

• Set Spacing to 2 m, and click OK.



) selected,


) selected,


draw tendons in the next panel: • Click at the center of the column at grid intersection B-1.







• Click at the center of the column at B-3. 20 In the Tendon Panel dialog box, click OK to accept the



Orthogonal (

) and Snap


) selected,


).



) selected,



Note: This sequence is anti-clockwise. • Click at the center of the column at grid intersection C-3. • Click at the center of the column at D-3. • Enter 9.25, 26, and press Enter. • Turn off Snap Orthogonal (

).




• Uncheck Skip Start Tendon, and click OK.




) selected,



mm and Profile at end 2 to 100 mm, and click OK. 14 With the Selection tool (


• Click at the center of the column at grid intersection B-3. • Click at the center of the column at C-3. • Click at the center of the column at C-4. • Click at the center of the column at B-5.



mm, and click OK.






) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection A-2.


) selected,



286

RAM Concept

Chapter 44 • Click at the center of the column at grid intersection C-3.



The longitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab.

• Click at the center of the column at D-4. • Click at the center of the column at C-4.





Note: Auto-connect will ignore the tendons at the first click because there are already two tendon segments connected at that point. The panel in the top right has too many tendons and some should be deleted. 27 With the Selection tool (

to 5, and click OK.


this panel.



mm and click OK.


Delete. 29 With the Half Span Tendon Panel tool (

) selected,

draw tendons that terminate in this panel:


), select all of the terminated tendon segments over a drop cap, by: • Double clicking at grid intersection A-1. • Hold the Shift key down and double click at A-3.


).




• Type r0,2.1.




Note: The snap orthogonal snaps the cursor to 22, 19.6 m. • Click at the last tendon profile point at 22, 17.5 m. 30 In the Tendon Panel dialog box:


mm, and click OK.




segment at B-2.





mm, and click OK.



) selected,





the right of grid 2. 38 Right click on the plan and choose Selection Properties



), select the tendon segment that passes through the opening. 50 Choose the Move tool (

).




).


the moved tendon.

RAM Concept

287

Chapter 44 55 Repeat for the tendon segment below the moved tendon.

Note: You could cut down the number of steps in moving the tendon from the opening by using the Utility tool. This combines the selection tool with move and stretch. Refer to

“Expanding tool buttons” on page 6 and “Using the Utility tool to move and stretch” on page 20 for further information.


288

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44.5 Create the design strips Design strips are an essential part of RAM Concept because they link finite element analysis with concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for section design. There are two directions called Latitude and Longitude. Generate the latitude spans:


).


Note: Column Strip Width Calc is already set to Full Width. 2 Click the General tab.

Note: Environment is already set to Class 3 - 0.1 mm. Note: The Consider as Post-Tensioned box is already checked in the BS8110 template. 3 Click the Column Strip tab. 4 Set Cross Section Trimming to Max Rectangle. 5 Change CS Top Cover to 25 mm.


Two span segments are skewed. How you treat skewed strips is often a subjective matter, but in this tutorial we suggest one strip is straightened and the other edited in a different manner.

6 Change CS Code Min. Reinforcement Location to Elevated Slab.

Generate the latitude strips:

7 Click OK.

Generate Strips.



Generate Spans.




The Generate Spans dialog box opens with Spans to Generate set to Latitude. Accept the Minimum Span Length as 0.5 meters. 9 Click OK.



Concept uses imperfect algorithms that do not always produce acceptable span segments and span segment strips,

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289

Chapter 44 as shown in Figures 44-14 through 44-16. You can make corrections with a number of tools


You can see this more easily if the strip hatching is turned on.

2 Select the Orient Span Cross Section tool (

1 Select the diagonal span strip as shown in Figure 44-15.


).

).


Hatch the strips:


).



2 Check Hatching under Latitude Span Segment Strips, and click OK.


Figure 44-14 Skewed span segment that snapped to end of wall Straighten a span segment:


shown in Figure 44-14). 2 Turn on Snap to Intersection ( 3 Select the Rotate tool (

).

).

Figure 44-16 Design strip with excessive width. Draw a Span Boundary Polyline:


).





The command line prompts Enter rotation end angle. 6 Enter 180 and press Return.


3 Click to the right of the slab edge (point B). 4 Right-click, and click enter. Regenerate the latitude span strips:


).


Figure 44-15 Diagonal strip that warrants manual improvement.

290

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Chapter 44




).



One span segment on grid 2 is slightly skewed due to the column wall detail at C2. Another span segment overlays a wall and is unnecessary since the slab is continuously supported (see “Drawing design strips near walls” on page 113 for discussion). Straighten a span segment:

The defaults set up in the Latitude Design Spans Plan will have remained the same. Since the cover cannot be the same for both directions, change it for the longitudinal direction.


(highlighted in Figure 44-18). 2 Turn on Snap to Intersection ( 3 Select the Rotate tool (

).

).

• Change CS Top Cover to 41 mm.

4 Click at the end of the span segment at grid B2.

• Change CS Bottom Cover to 37 mm.


• Click OK.





• Set Spans to Generate to Longitude. • Click the “up-down” orientation button tool ( ).

6 Enter 90 and press Return.



Delete.

• Click OK. The spans appear in the longitude direction.



).

).


left or right of the first click. 5 The orientation line half way along the span strip is now

“horizontal”.

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291

Chapter 44 Generate the longitude strips:





44.6 Regenerate the mesh Figure 44-19 Design Strip: Longitude Design Spans Plan. Check for punching shear:


).





).




292

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Chapter 44






Spans Plan.







Calculate:

1 Click Calc All (

).






and click OK.


Recalculate:

1 Click Calc All (




).












RAM Concept

This shows “OK” for all but one design strip. “OK” means that there are no violations of code limits for ductility, flexural stress and one-way shear. Note that status does not flag excessive deflections.

293

Chapter 44 The failure clause shown for design strip 2C-3 is “TR43 6.10.2”. You can look up this clause in TR43 to see that it is the “transfer condition”. It is known as the Initial Service Rule Set in Concept.



It is not surprising that there is a problem in this span as there are 25 strands in half a panel. A solution would be to terminate some strands at grid 3. There are punching shear status results at each column. You can see these more easily on the dedicated punching plan. 2 Choose Layers > Design Status > Punching Shear Status

Plan. Concept has noted “Non-standard section” at six column locations and “OK with SSR” at eight columns. “Non-standard Section” is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three cases: interior, edge and corner. Concept still calculates a stress ratio for non-standard sections. Refer to “Non-Standard Sections: AS3600, BS8110, EC2 and IS 456” on page 162 of Chapter 29 for more information. Where the unreinforced stress ratio (USR) is less than 1.0, the column’s punching shear is satisfactory without any reinforcement (subject to the comments above concerning “Non-standard section)). Stud shear reinforcement is required where Concept reports “OK with SSR”.



This shows all the code-determined reinforcement for each of the design strips. Since the slab is post-tensioned, there is not much reinforcement. You might choose to view all design reinforcement on the one plan, or you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom) and direction (latitude or longitude). 2 Choose the plans that best convey the results without too

much clutter.



294

RAM Concept

Chapter 44 The Reinforcement layer plans show detailed reinforcement. In particular, the top bars are rationalized so that the number is consistent each side of columns.

• Change Max Frame # to 4. • Click OK

Look at detailed top reinforcement:


Figure 44-29 Service Design: Top Stress Plan.




44.7.3 Concrete stresses TR43 has limits for the hypothetical stresses due to flexure and axial loads. The code bases the rules upon “averaging” rather than peak values. Stress contour plots of the net flexural stresses are available in Concept. Most designers will not be interested in these plots because, in following the code, Concept does not use the contours directly in design. What will likely be of interest are the plans that show the concrete stresses plotted along the design strips. These are the average stresses based upon the design strip widths. View top stress plan:

44.7.4 Deflection Usually you are interested in short-term and long-term deflections. Load history deflections can be used to evaluate both. Calculate Load History Deflections:


), or choose

Process > Calc Load History Deflections. The Maximum Short Term Load, Sustained Load, and Final Instantaneous Load History Deflection Layers provide contour plans for deflection.

1 Choose Layers > Rule Set Designs > Service Design > View maximum short term load deflection:

Top Stress Plan. 2 Right click over the plan and choose Plot ( 3 In the Plot Settings dialog box:

RAM Concept

).



295

Chapter 44

44.7.5 Bending Moments While it is not necessary to view bending moments, it can be useful, especially for irregular structures. Even though principal moments are important, the default moment contours plans are for Mx (moment about the x-axis) and My. This is because most designers detail reinforcement orthogonally, and the directions are usually the x- and yaxes. You can view moments about any axes, including the principal axes. It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful. View Factored LC Moments:


1.4D + 1.6L > Mx Plan. The Mx contours should be visible. 2 Turn on Snap Orthogonal (

)

3 Click the Selected Plot Distribution tool ( Figure 44-30 Maximum Short Term Load: Deflection Plan.

).


intersection D-3. 2 Right click over the plan and choose Plot (

) to change








This shows how Mx varies across the panel, and highlights the approximate nature of the TR43 post-tension design method. See “Section distribution plots” on page 158 for more information.


Figure 44-32 Ultimate LC: 1.4D + 1.6 Mx Plan showing use of Plot Distribution tool.

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).


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Chapter 44

298

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Chapter 45

45 PT Flat Plate Tutorial: EC2 / TR43 This chapter describes the steps for modeling a posttensioned two-way flat plate with uniform loads. The objective of this tutorial is to build on the skills learned in the Chapter 41 RC tutorial and introduce new steps, such as using a CAD drawing and post-tensioning.

3 Click the Drawing Import tab. 4 Click Show All, and then click OK. Draw the slab area:


( Some tools and methods described in the RC tutorial are not used here. As such, it is highly recommended that you first do the RC tutorial.

) and Snap to Point

).




This is not a particularly “aggressive” design. After you have completed the tutorial, you may wish to make the slab thinner to investigate the ramifications. You could also use this as a reinforced concrete tutorial by making a few adjustments (for example, a thicker slab).

• Choose a Concrete Strength of C32/40. • Set Thickness to 250 mm. • Leave Surface Elevation as 0 and Priority as 1. • Click OK.

RAM Concept’s EC2 implementation considers the base EC2 code, the UK National Annex and the second edition of the Concrete Society’s Technical Report 43 for posttensioned slab design.




26.05, 8.2 m and 26.05, 8.8 m. Cursor plan coordinates display next to the command prompt.

Note: There are two vertices near each other near B-5 at

5 Complete the polygon by clicking at your starting point


45.1 Import the CAD drawing The CAD file you import is located in your RAM Concept program directory Import the CAD file:



click OK.


Figure 45-1 The slab outline on the Mesh Input: Standard Plan.


Draw the balcony slab area:



).




• Change Thickness to 200 mm. RAM Concept

299

Chapter 45 11 Enter a side dimension of 1.2 m and click OK.

• Change Surface Elevation to -50 mm. • Change the Priority to 2, and click OK. 3 With the Slab Area tool (


Draw the opening:


).






properties.

Figure 45-3 The opening on the Mesh Input: Standard Plan.

2 In the Default Slab Area Properties dialog box: Hatch the slab areas:

• Change Thickness to 500 mm. • Change Surface Elevation to 0, and leave the Priority as 2. • Click OK.


).

The Visible Objects dialog box will appear. 2 Check “Hatching” under “Slab Areas”.








).





) and press


).


• Choose a Concrete Strength of C32/40. • Set Width to 600 mm. • Set Depth/Diameter to 600 mm. 3 Click OK.





The selected tool becomes current for that button.







). ).


• Choose a Concrete Strength of C20/25. 300

RAM Concept


View the mesh:



the centerline. • Place the cursor near 8.825, 26.3 m and it will snap to where the center of the wall intersects the edge of the slab, and click.




).


) and press down





) to rotate the


).


Figure 45-4 After defining the slab, the Mesh Input: Standard Plan shows the slab areas and opening (hatched), the columns and the wall.

).


Generate the mesh:


).




RAM Concept

RAM Concept calculates the concrete self-weight automatically.

301




).






).















click OK. 302

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303

Chapter 45


• Click at the center of the column at A-2. • Click at the center of the column at A-3.


• Right click, and then click Enter. 9 Turn on Snap Orthogonal (

).


) selected, draw a

tendon along grid D: • Click at the center of the column at grid intersection D-4. • Click at the center of the column at D-3.

In the United Kingdom, engineers are directed towards Technical Report 43 and that document encourages the use of full panel design strips with the banding technique. This method, with bonded tendons, is used in this tutorial.

11 Turn off Snap Orthogonal (

Note: RAM Concept has two layers for tendons called


latitude and longitude. Refer to “Using the latitude and longitude prestressing folders” on page 133 for more information.

default properties.



• Right click, and then click Enter. ). ) to edit its



) selected, draw a

tendon along grid B: • Click at the center of the column at grid intersection B-1. • Click at the center of the column at B-2. • Click at the center of the column at B-3. • Click at the center of the column at B-5.



• Right click, and then click Enter. 15 With the Tendon Polyline tool (


) selected, draw a


).





) to edit its


• Set PT System to 12.9mm Bonded.

• Click at the center of the column at C-3. • Click at the center of the column at C-4. • Right click, and then click Enter. 16 With the Select Connected Tendons tool (

) selected,

double-click the tendon on grid B. 17 Right click on the plan and choose Selection Properties



• Set Profile at end 1 to 212 mm.


• Set Profile at end 2 to 38 mm, and click OK.


Note: The 25 mm cover to the 19 mm high duct (containing 12.9 mm diameter strand) determines these profiles. 7 Turn Snap to Intersection (

).


) selected, draw a

tendon along grid A: • Click at the center of the column at grid intersection A-1. 304

• Click at the corner of the slab near D-2.

The latitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab. 19 With the Selection tool (

), select all of the terminated tendon segments, other than those over a drop cap, by: • Double clicking at grid intersection B-1.

RAM Concept

Chapter 45 • Hold the Shift key down and double click at B.81.






• Hold the Shift key down and double click at D-4. 20 Right click on the plan and choose Selection Properties





mm and click OK.



mm and click OK.





mm and click OK.








segment at C-2.








mm and click OK.




).




).



RAM Concept


).


) to


• Set Strands per Tendon to 4, and click OK. 5 With the Full-Span Tendon Panel tool (


remain the same. Strictly speaking, you should adjust Profile at end 1 at columns (to avoid a clash with latitude tendons) but you can ignore for this tutorial.

) selected,

draw tendons in the bottom left panel: • Click at the center of the column at grid intersection A-1. • Click at the center of the column at B-1. • Click at the center of the column at B-2.

305

Chapter 45 • Click at the center of the column at A-2.





• Set Spacing to 2 m.

• Set Spacing to 2 m, and click OK.



) selected,












Orthogonal (

) and Snap

last choices. Alternatively, you could select Auto Connect, but you would have to uncheck Skip Start Tendon. 21 With the Full-Span Tendon Panel tool (

) selected,


).


) selected,




).








) selected,








mm, and click OK.






) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection A-2. • Click at the center of the column at B-2.

306

) selected,




) selected,






RAM Concept

Chapter 45 • Click at the center of the column at D-4. • Click at the center of the column at C-4. 26 In the Tendon Panel dialog box:


Note: Auto-connect will ignore the tendons at the first click because there are already two tendon segments connected at that point. The panel in the top right has too many tendons and some should be deleted. ), select the second tendon in

this panel. 28 Hold down shift and select the fifth tendon, and press

Delete. 29 With the Half Span Tendon Panel tool (

) selected,

• Hold the Shift key down and repeat the procedure until you have selected all applicable end tendon segments (tendon segments terminating at grids B and D). 41 Right click on the plan and choose Selection Properties



), select all of the terminated tendon segments over a drop cap, by: • Double clicking at grid intersection A-1. • Hold the Shift key down and double click at A-3. • Hold the Shift key down and double click at B-5.

draw tendons that terminate in this panel: • Turn on Snap Orthogonal (

), select all of the terminated tendon segments, other than those over a drop cap or within the balcony slab: • Fence the tendon segments that end on grid A.





).




• Type r0,2.1.

mm, and click OK.



Note: The snap orthogonal snaps the cursor to 22, 19.6 m. • Click at the last tendon profile point at 22, 17.5 m. 30 In the Tendon Panel dialog box:



segment at B-2.








mm and click OK.


) selected,






Finally, you need to move the tendon that goes through the opening. 49 With the Selection tool (


).




).


the moved tendon.





to 5, and click OK. The longitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab.

RAM Concept

the tendon from the opening by using the Utility tool. This combines the selection tool with move and stretch. Refer to

307

Chapter 45 “Expanding tool buttons” on page 6 and “Using the Utility tool to move and stretch” on page 20 for further information.


308

RAM Concept

Chapter 45



).


Note: Column Strip Width Calc is already set to Full Width. 2 Click the General tab.

Note: Environment is already set to Normal. Note: The Consider as Post-Tensioned box is already checked in the EC2 template. 3 Click the Column Strip tab.

Note: CS PT Service Design Type is already set to Stress & Crack Width. You may change this to perform only stress checks or only crack width designs.



4 Set Cross Section Trimming to Slab Rectangle.


5 Change CS Top Cover to 25 mm.

Generate Strips.




7 Click OK. 8 Click the Generate Spans tool (






RAM Concept

309







).

).


Hatch the strips:


).








).

).



).









).



310

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Chapter 45




).







).

).





• Click OK.









Delete.




).

).



“horizontal”.

RAM Concept

311








).





).




312

RAM Concept

Chapter 45


The problem is that the cross sections are trimmed with the Slab Rectangle setting. For span segment 6-2, that setting is causing a problem because of the combination of the drop cap and thinner balcony slab. Edit span segment 6-2:




Spans Plan.







Calculate:

1 Click Calc All (

).






and click OK.


Recalculate:

1 Click Calc All (




).











This plan shows many failures due to EC2 section 7.3.


RAM Concept

313

Chapter 45

45.7.2 Stress and Crack Width Designs

Note: Some UK slab designers consider that designing

It is not surprising that there is a problem in this span as there are 25 strands in half a panel. A solution would be to terminate some strands at grid 3 (not done in this tutorial).

slabs according to TR 43 is “deemed to comply” with the EC2 crack width provisions and hence the EC2 crack width calculations need not be checked.We will take that approach here.

There are punching shear status results at each column. You can see these more easily on the dedicated punching plan.

To have Concept use only the TR43 stress limits:

1 Open the Design Strip > Latitude Design Spans plan. 2 Select all of the design spans and edit their properties. 3 On the Column Strip tab in the properties dialog, change

the CS PT Service Design Type to “Stress” and click OK 4 Make the same changes to the Longitude Design Spans Calculate and Review Updated Status:

1 Click Calc All (




Plan. Concept has noted “Non-standard section” at six column locations and “OK with SSR” at eight columns. “Non-standard Section” is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three cases: interior, edge and corner. Concept still calculates a stress ratio for non-standard sections. Refer to “Non-Standard Sections: AS3600, BS8110, EC2 and IS 456” on page 162 of Chapter 29 for more information. Where the unreinforced stress ratio (USR) is less than 1.0, the column’s punching shear is satisfactory without any reinforcement (subject to the comments above concerning “Non-standard section)). Stud shear reinforcement is required where Concept reports “OK with SSR”.


Figure 45-25 Design Status: Updated Status Plan.

This shows “OK” for all but two design strips. “OK” means that there are no violations of code limits for ductility, flexural stress and one-way shear. Note that status does not flag excessive deflections. The failure clause shown for design strip 2C-1 is “TR43 5.8.1”. This is due to a slightly too high tensile stresses at the column face. This can be resolved by adding one more tendon along grid B (not done in this tutorial). The failure clause shown for design strip 2C-3 is “TR43 5.8.2”. You can look up this clause in TR43 to see that it is the “transfer condition”. It is known as the Initial Service Rule Set in Concept.

314


RAM Concept

Chapter 45



The Reinforcement layer plans show detailed reinforcement. In particular, the top bars are rationalized so that the number is consistent each side of columns. Look at detailed top reinforcement:



This shows all the code-determined reinforcement for each of the design strips. Since the slab is post-tensioned, there is not much reinforcement. You might choose to view all design reinforcement on the one plan, or you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom) and direction (latitude or longitude).Choose the plans that best convey the results without too much clutter.


45.7.4 Concrete stresses TR43 has limits for the hypothetical stresses due to flexure and axial loads. The code bases the rules upon “averaging” rather than peak values. Stress contour plots of the net flexural stresses are available in Concept. Most designers will not be interested in these plots because, in following the code, Concept does not use the contours directly in design. What will likely be of interest are the plans that show the concrete stresses plotted along the design strips. These are the average stresses based upon the design strip widths. View top stress plan:

1 Choose Layers > Rule Set Designs > Characteristic

Service Design > Top Stress Plan. 2 Right click over the plan and choose Plot (

).

3 In the Plot Settings dialog box:

• Change Max Frame # to 4. • Click OK


RAM Concept

315

Chapter 45

Figure 45-30 Characteristic Service Design: Top Stress Plan. Figure 45-31 Maximum Short Term Load: Deflection Plan.

To view the Max Demand more easily you can uncheck Max Capacity in the plot options. Similarly, you can view the bottom stress plan at Layers > Rule Set Designs > Characteristic Service Design > Bottom Stress Plan.


) to change

Plot Type from Color Contour to Contour. View sustained deflection:





), or choose





316

RAM Concept

Chapter 45


This shows how Mx varies across the panel, and highlights the approximate nature of the TR43 post-tension design method. See “Section distribution plots” on page 158 for more information.

It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful. View Ultimate LC Moments:


1.25D + 0.9H + 1.5L > Max Mx Plan. The Mx contours should be visible. Let’s modify this plan to show moments for the “Standard” context (full load, with standard load factors) instead of the “Max” context (maximum value for any set of standard or alternate load factors and any load pattern). 2 Right click over the plan and choose Plot (

).

3 In the plot window that opens, the Slab tab should be

active. Change the Context item from “Max” to “Standard”. Click OK.

Figure 45-33 Ultimate LC: 1.25D + 0.9H + 1.5L Max Mx Plan showing use of Plot Distribution tool.

Now let’s draw some section distribution plots.




)


).


intersection D-3.


).


Objects dialog box and click OK. This shows the bending moment shape along the line you have drawn. 7 While pressing the Shift key, click at grid intersection B-



RAM Concept

317

Chapter 45

318

RAM Concept

Chapter 46

46 PT Flat Plate Tutorial: IS 456 : 2000 This chapter describes the steps for modeling a posttensioned two-way flat plate with uniform loads. The objective of this tutorial is to build on the skills learned in the Chapter 41 RC tutorial and introduce new steps, such as using a CAD drawing and post-tensioning. Some tools and methods described in the RC tutorial are not used here. As such, it is highly recommended that you first do the RC tutorial. This is not a particularly “aggressive” design. After you have completed the tutorial, you may wish to make the slab thinner to investigate the ramifications.

Draw the slab area:


(

) and Snap to Point

).




• Choose a Concrete Strength of M40. • Set Thickness to 250 mm. • Leave Surface Elevation as 0 and Priority as 1. • Click OK.











click OK.



).






properties.





RAM Concept

319



Draw the opening:


).











• Click OK.


).




OK.





3 Check “Hatching” under “Slab Openings”, and then click


). Define the column locations and properties:


) and press

down on the left mouse button for one second. A pop-up menu appears. 8 Select the Drop Cap tool from the menu.


).


• Choose a Concrete Strength of 32 MPa. • Set Width to 600 mm. • Set Depth/Diameter to 600 mm, and click OK. 3 Click at the center of all 13 column locations shown on


The selected tool becomes current for that button. Define the wall location and properties:



).





11 Enter a side dimension of 1.2 m and click OK.

).

• Choose a Concrete Strength of 20 MPa. 4 Click OK.

320

RAM Concept


3 Click Generate.

the centerline: • Place the cursor near 8.825, 26.3 m and it will snap to where the center of the wall intersects the edge of the slab, and click. • Place the cursor at the center of the column at C-2 (it will snap orthogonally) and click.

View the mesh:



You have now defined the structure but the element mesh does not yet exist. 6 Go to “Generate the mesh:”, or try the next method. 7 The wall should be highlighted as it is the current


).


) and press down





) to rotate the


).


).



).



1 m.

RAM Concept

321

Chapter 46






).





).








Note: You could have drawn the 3 kN/

Figure 46-8 Live (Reducible) Loading: All Loads Plan (with area loads hatching turned on).

m2

load by first changing the area load default properties and then using the tool.







click OK.

322

RAM Concept






RAM Concept

323

Chapter 46



Post-tensioning methodology varies from country to country. In India, engineers commonly use column and middle strips for post-tensioned flat plate design, and, generally, detail (bonded) tendons in both the column and middle strips.



• Click at the center of the column at grid intersection B-1. • Click at the center of the column at B-2. • Click at the center of the column at C-2. • Click at the grid intersection C-1. 11 In the Tendon Panel dialog box:

Note: The tutorial in Chapter 49 explains the use of Strip


Wizard to establish an estimate of the number of strands required for the critical band.

• Set Spacing to 2 m,

Note: For use of the tendon parameters layers as an alternative and perhaps quicker means of defining prestressing, please refer to “PT Flat Plate Tutorial: ACI 318-08” on page 239. Define the latitude tendons:


) selected,

draw tendons in the next two panels: • Click at the center of the column at grid intersection A-2. • Click at the center of the column at A-3.




) selected,



).





• Uncheck Skip start tendon, and click OK. 14 Turn off Snap Orthogonal (



) to



• Click at the center of the column at grid intersection B-3. • Click at the center of the column at B-5.


Note: The 25 mm cover to the 19 mm high duct (containing 12.7 mm diameter strand) determines these profiles. ) and Snap Orthogonal

• Click at the center of the column at C-4. • Click at the center of the column at C-3. 16 In the Tendon Panel dialog box:

• Set Auto Connect, and click OK. 17 With the Full-Span Tendon Panel tool (

(

) selected,


).


) selected,






• Click at grid intersection D-2.

• Click at the center of the column at B-2. • Click at the center of the column at B-1. 9 In the Tendon Panel dialog box:

324

) selected,




).




RAM Concept

Chapter 46 • Check Skip start tendon, and click OK. 19 With the Full-Span Tendon Panel tool (


) selected,


draw tendons in the next panel: • Click at the center of the column at grid intersection C-3.

), select all of the tendon segments that terminate over a drop cap, by: • Double clicking at grid intersection A-1.











mm and click OK.


Note: Auto-connect will ignore the tendons at the first click because there are already two tendon segments connected at that point. 21 With the Select Connected Tendons tool (

) selected,












) selected,

double-click the tendon directly above grid B. 25 Hold down shift and double-click the tendon directly

below grid B. 26 Right click on the plan and choose Selection Properties



), select all of the terminated tendon segments, other than those over a drop cap or within the balcony slab: • Fence the tendon segments that end on grid 1. • Hold the Shift key down and repeat the procedure until you have selected all applicable end tendon segments (tendon segments terminating at grids 2, 3, 4 and 5). 29 Right click on the plan and choose Selection Properties



segment at C-2. 41 Hold down the Shift button, and double click the tendon

segment immediately below (profile point at (9,15.7)). 42 Right click on the plan and choose Selection Properties


mm and click OK.



between D-2 and D-3. 45 Click the Calc Profile tool (

).

The Calc Tendon Profile dialog box appears and reports the current balance load is -5.27 kN/m. If this is not the number then you probably selected only one tendon segment. 46 Click Cancel. 47 With the Selection tool (



).

49 Input the desired balance load as -5.3 kN/m in the Calc


mm and click OK.



), double click the tendon segment above B.8-1 that terminates within the 200 mm balcony slab.






from the popup menu. RAM Concept

325

Chapter 46 52 In the Properties dialog box, set Profile at end 2 to 125


mm and click OK.


Note: These steps first used the Calc Profile tool to determine a low point that produces a similar average uplift in an end span as the adjacent span, and then manually changed the low points for practical reasons. Finally, you need to adjust the tendon that goes through the opening. 53 Turn on Snap Nearest Snapable Point (

Orthogonal (

) and Snap

) selected,

• Click at the center of the column at grid intersection A-1. • Click at the center of the column at B-1. • Click at the center of the column at B-2. • Click at the center of the column at A-2. 4 In the Tendon Panel dialog box:


).




) selected,






mm and click OK.



57 Choose the Stretch tool (

).


58 With the one tendon segment selected, stretch the profile

point at grid 3 to the other side of the opening.

Note: The Snap Nearest Snapable Point snaps the cursor to the edge of the opening.



Orthogonal (

) and Snap

).


) selected,





mm and Profile at end 2 to 100 mm, and click OK. 12 With the Selection tool ( Figure 46-10 Manual Latitude Tendon: Standard Plan.




Longitude Tendon > Standard Plan. remain the same. Strictly speaking, you should adjust Profile at end 1 at columns (to avoid a clash with latitude tendons) but you can ignore for this tutorial.

326


mm, and click OK.



), select the two shortest of the half-span (cantilever) tendon segments.

Note: This makes the short tendon segments flat. 15 With the Full-Span Tendon Panel tool (

) selected,


). RAM Concept

Chapter 46 • Click at the center of the column at grid intersection A-2. • Click at the center of the column at B-2. • Click at the center of the column at B-3. • Click at the center of the column at A-3.


) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection C-3. • Click at the center of the column at D-3. • Click at the center of the column at D-4.





• Set Spacing to 2 m. • Check Skip start tendon, and click OK. 17 With the Full-Span Tendon Panel tool (

) selected,












this panel.





) selected,


Delete.


Note: This sequence is anti-clockwise.

) selected,

draw tendons that terminate in this panel: ).





• Enter 9.25, 26, and press Enter. • Turn off Snap Orthogonal (

• Type r0,2.1.


).





• Set Auto Connect. • Uncheck Skip Start Tendon, and click OK. 21 With the Full-Span Tendon Panel tool (


) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection B-3. • Click at the center of the column at C-3.



) selected,








• Set Layout to Splayed. • Set Tendon Spacing to Equal.



the right of grid 2.





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327

Chapter 46 37 In the Properties dialog box, change Strands Per Tendon

to 5, and click OK.



The longitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab. 38 With the Selection tool (


the tendon from the opening by using the Utility tool. This combines the selection tool with move and stretch. Refer to “Expanding tool buttons” on page 6 and “Using the Utility tool to move and stretch” on page 20 for further information.







mm, and click OK.





46.5 Create the design strips Design strips are an essential part of RAM Concept because they link finite element analysis with concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for section design. There are two directions called Latitude and Longitude.




Plan.





).




Note: Column Strip Width Calc is already set to Code Slab. 3 Click the General tab.

).


the moved tendon.

).

4 Check the Consider as Post-Tensioned box. 5 Click the Column Strip tab. 6 Set Cross Section Trimming to Max Rectangle. 7 Change CS Top Cover to 25 mm.

328

RAM Concept

Chapter 46 8 Click the Middle Strip tab. 9 Check the Middle Strip uses Column Strip Properties

box. 10 Click OK. 11 Click the Generate Spans tool (





Concept uses imperfect algorithms that do not always produce acceptable span segments and span segment strips, as shown in Figures 46-14 through 46-17. You can make corrections with a number of tools. You can see this more easily if the strip hatching is turned on. Hatch the strips:

1 Choose View > Visible Objects ( Figure 46-12 Design Strip: Latitude Design Spans Plan.

).



click OK.





Generate Strips. The design strips appear in the latitude direction.



shown in Figure 46-14). 2 Turn on Snap to Intersection (

RAM Concept

).

329

Chapter 46 3 Select the Rotate tool (

).


4 Click at the end of the span segment at grid D3. 5 Click at the end of the span segment at the wall.

4 Right-click, and click enter. Regenerate the latitude span strips:




The three edited spans produce improved span strips. There is one more to edit.


).


1 Select the diagonal span strip as shown in Figure 46-15. 2 Select the Orient Span Cross Section tool ( 3 Turn on Snap Orthogonal (

).

).

Figure 46-17 Span segment C-2 to C-3. Draw a Span Boundary Polyline:



or below the first click.

).




3 Click at point B. 4 Right-click, and click enter. 5 Click at point C. 6 Click at point D. 7 Right-click, and click enter. 8 Select the Strip Boundary Polyline tool(

).

9 Click at point E as shown in Figure 46-17. 10 Click at point F, to the right of the opening. 11 Right-click, and click enter. 12 Select the span segment (between grid C2 and C3). 13 Right click on the plan and choose Selection Properties

from the popup menu. 14 In the Properties dialog box, change Span Width Calc to

Manual. 15 Uncheck Detect Supports Automatically. 16 Change Support Width at End 2 from 600 to 610 mm, and Figure 46-16 Design strip with excessive width.

click OK.

Draw a Span Boundary Polyline:

This ensures that the first (design strip) cross section passes through the opening, and hence uses less concrete section.


).


17 Click the Generate Selected Strips tool (

).

strips near Grid 3 (point A in Figure 46-16). 330

RAM Concept

Chapter 46 The edited spans produce improved span strips, as shown in Figure 46-18.




Spans Plan.

Straighten a span segment:


).


(highlighted in Figure 46-19).


The defaults set up in the Latitude Design Spans Plan will have remained the same. Since the cover cannot be the same for both directions, change it for the longitudinal direction. • Change CS Top Cover to 41 mm. • Change CS Bottom Cover to 37 mm. • Click OK. 4 Click the Generate Spans tool (

One span segment on grid 2 is slightly skewed due to the column wall detail at C2. Another span segment overlays a wall and is unnecessary since the slab is continuously supported (see “Drawing design strips near walls” on page 113 for discussion).




2 Turn on Snap to Intersection ( 3 Select the Rotate tool (

).


The command line prompts Enter rotation end angle. 6 Enter 90 and press Enter.


1 Select the span segment that overlays the wall. 2 Press Delete.



• Click OK.


The spans appear in the longitude direction.

).



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331

Chapter 46 8 Click at point C and D. 9 Right-click, and click enter. 10 Select the Strip Boundary Polyline tool(

).

11 Click at point E as shown in Figure 46-21. 12 Click at point F (the corner of the opening) and point G

(another corner). 13 Right-click, and click enter. 14 Select the span segment between grid B3 and C3. 15 Click the Generate Selected Strips tool (

).


1 Select the diagonal span strip between B-5 and C-4. 2 Select the Orient Span Cross Section tool ( 3 Turn on Snap Orthogonal (

).

).


left or right of the first click. Figure 46-20 Design Strip: Longitude Design Spans Plan after strip generation.

The area to the left of the opening has no design strip. You can use the tools to locate a middle strip in that area.

The orientation line half way along the span strip is now “horizontal”. 5 Click the Generate Selected Strips tool (

).

The new design strips appear, as shown in Figure 46-22.

Figure 46-21 Grid B3-C3 span segment and strips. Edit span segment with Span Boundaries and Strip Boundaries


highlighted line in Figure 46-20).

Figure 46-22 Design Strip: Longitude Design Spans Plan after editing.



Note: Some of the latitude and longitude design strips

3 Change Span Width Calc to Manual, and click OK.

(span segment strips) have different widths either side of a column. You could rationalize these strips such that they have similar widths at the column, especially the cantilever. See the discussion in “Defining strip boundaries manually” on page 102 of Chapter 22, “Defining Design Strips”. In particular, Example 22-2 on page 103 and Example 22-4 on page 104.

4 Select the Span Boundary Polyline tool ( 5 Click at point A as shown in Figure 46-21. 6 Click at point B. 7 Right-click, and click enter.

332

).

RAM Concept

Chapter 46

46.6 Regenerate the mesh



).





).




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Chapter 46

46.7 Calculate and view the results After you run the model, you can view the results of the analysis and design calculations. Review Calc Options:

1 Choose > Criteria > Calc Options 2 Review the options, and click OK.

Note: See “Calculating the results” on page 149 of Chapter 28 for more information. Figure 46-26 Rotation and zoom-in of the problem location in Figure 4625.

Calculate:

1 Click Calc All (


An error message appears twice concerning a problem with a tendon out of the slab in strip 6C-2. 2 Click Continue twice to clear the error message.

The source of the tendon error messages must be investigated.



Spans Plan. One more error appears to do with reinforcement detailing. 3 Click Continue to clear the reinforcement error message.

).


Segments, and click OK.



4 Select span segment 6-2. 5 Right click on the plan and choose Selection Properties



).

3 Click the Tendons tab. 4 Select the Longitude Tendons layer, check Tendons, and

click OK. 5 Use the Rotate about X and Y axes tool (



and click OK. Edit span segment 2-3:



).

3 Check the Numbers box under Latitude Span Segments,

and click OK. 4 Select span segment 2-3. 5 Right click on the plan and choose Selection Properties

from the popup menu. 6 Click the Middle Strip tab. Figure 46-25 Longitude Cross Sections Perspective with longitude tendons visible.

7 Uncheck the Middle Strip uses Column Strip Properties

box. 8 Change MS Top Cover to 25 mm. 9 Change MS Span Detailer to None, and click OK.

The above change is made to eliminate the reinforcement warning. In a proper design you should investigate this further.

334

RAM Concept

Chapter 46 Recalculate:

1 Click Calc All (


Concept completes the calculatons without errors.

Note: See “Cross Section Trimming” on page 105 for a thorough explanation of Cross Section trimming.

Where the unreinforced stress ratio (USR) is less than 1.0, the column’s punching shear is satisfactory without any reinforcement (subject to the comments above concerning “Non-standard section)). Stud shear reinforcement is required where Concept reports “OK with SSR”.

Note: Choose > Layers > Design Status > SSR Plan to 46.7.1 Design Status

view the stud shear reinforcement.





This shows OK for all design strips. This means that there are no violations of code limits for ductility or one-way shear. Note that status does not flag excessive deflections.



There are punching shear status results at each column. You can see these more easily on the dedicated punching plan. 2 Choose Layers > Design Status > Punching Shear Status

Plan. You can see that seven columns have an unreinforced stress ratio (USR) of less than 1.0. Six columns report “OK with SSR” which means stud shear reinforcement is required. Concept has noted “Non-standard section” at six column locations. “Non-standard Section” is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three cases: interior, edge and corner. Concept still calculates a stress ratio for nonstandard sections. Refer to “Non-Standard Sections: AS3600, BS8110, EC2 and IS 456” on page 162 of Chapter 29 for more information.

RAM Concept


335

Chapter 46 This shows all the code-determined reinforcement for each of the design strips. You might choose to view all design reinforcement on the one plan, or you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom) and direction (latitude or longitude). 2 Choose the plans that best convey the results without too

much clutter.



) to change

Plot Type from Color Contour to Contour. View sustained deflection: Figure 46-30 Design Status: Latitude Bottom Reinforcement Plan.





), or choose





336

RAM Concept

Chapter 46


See “Section distribution plots” on page 158 for more information.

It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful. View Factored LC Moments:


1.5D + 1.5L > Mx Plan. The Mx contours should be visible. 2 Turn on Snap Orthogonal (

)


).


intersection D-3.

Figure 46-33 Ultimate LC: 1.5D + 1.5L Mx Plan showing use of Plot Distribution tool.




Plan

1, and then click at grid intersection B-3. This shows how Mx varies across the panel, and highlights the different column and middle strip moments.

1 Choose Layers > Design Strips > Latitude Design Strips 2 Choose View > Visible Objects (

).


Objects dialog box and click OK. See “Calculating the balanced load percentages” on page 389 for more information.

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337

Chapter 46

338

RAM Concept

Chapter 47

47 PT Flat Plate Tutorial: CSA A23.3-04 This chapter describes the steps for modeling a posttensioned two-way flat plate with uniform loads. The objective of this tutorial is to build on the skills learned in the Chapter 41 RC tutorial and introduce new steps, such as using a CAD drawing and post-tensioning. Some tools and methods described in the RC tutorial are not used here. As such, it is highly recommended that you first do the RC tutorial. This is not a particularly “aggressive” design. After you have completed the tutorial, you may wish to make the slab thinner to investigate the ramifications.

Draw the slab area:


(

) and Snap to Point

).




• Choose a Concrete Strength of 35 MPa. • Set Thickness to 250 mm. • Leave Surface Elevation as 0 and Priority as 1. • Click OK.











click OK.



).






properties.





RAM Concept

339



Draw the opening:


).











• Click OK.


).






), select (by double-clicking) and delete the drop cap at B-2.


6 Click Redraw (



).


) and press




).


• Choose a Concrete Strength of 35 MPa. • Set Width to 600 mm. • Set Depth/Diameter to 600 mm.


3 Click OK.



the imported drawing. The selected tool becomes current for that button. 9 Click at the column at B-2.



A Drop Cap Tool dialog box appears. 10 Enter an angle of zero degrees. 11 Enter a side dimension of 1.2 m and click OK.


). ).


• Choose a Concrete Strength of 25 MPa. 4 Click OK.

340

RAM Concept


View the mesh:

the centerline.


• Place the cursor near 8.825, 26.3 m and it will snap to where the center of the wall intersects the edge of the slab, and click.




).


) and press down

on the left mouse button for one second. A pop-up menu appears. 10 Select the Left Wall tool from the menu. 11 Click at the extreme corner of the slab near D-2. 12 Click at Grid C, near C-2. Figure 47-5 Element: Standard Plan. View the structure:



) to rotate the


).


).

Figure 47-4 After defining the slab, the Mesh Input: Standard Plan shows the slab areas and opening (hatched), the columns and the wall. Figure 47-6 Element: Structure Summary Perspective. Generate the mesh:


).



RAM Concept

47.3 Define the loads RAM Concept calculates the concrete self-weight automatically.

341




).






).















click OK. 342

RAM Concept






RAM Concept

343

Chapter 47



).






) selected, draw a

tendon along grid D: • Click at the center of the column at grid intersection D-4. • Click at the center of the column at D-3. • Click at the corner of the slab near D-2. • Right click, and then click Enter. 11 Turn off Snap Orthogonal (

).


) to edit its



) selected, draw a

tendon along grid B: • Click at the center of the column at grid intersection B-1. • Click at the center of the column at B-2. • Click at the center of the column at B-3.





Latitude Tendon > Standard Plan.






) to edit its

default properties.

• Click at the center of the column at C-2. • Click at the center of the column at C-3. • Click at the center of the column at C-4. • Right click, and then click Enter.



) selected,

• Set PT System to 12.7mm Unbonded.





Note: The 25 mm cover to the 19 mm high duct (containing 12.9 mm diameter strand) determines these profiles. 7 Turn Snap to Intersection (

).


) selected, draw a

tendon along grid A: • Click at the center of the column at grid intersection A-1.

344

) selected, draw a


).



), select all of the terminated tendon segments, other than those over a drop cap, by: • Double clicking at grid intersection B-1.


• Hold the Shift key down and double click at B.81.





RAM Concept

Chapter 47 • Hold the Shift key down and double click at D-4. 20 Right click on the plan and choose Selection Properties




mm and click OK.

mm and click OK.






mm and click OK.







segment at C-2. 29 Right click on the plan and choose Selection Properties





mm and click OK.





).



Note: The defaults set up in the Latitude Tendon Plan remain the same. Strictly speaking, you should adjust Profile at end 1 at columns (to avoid a clash with latitude tendons) but you can ignore for this tutorial. 2 Turn on Snap to Intersection (

).

3 Double click the Full Span Tendon Panel tool ( 4 In the Default Tendon Properties dialog box:


33 Click Cancel.






).

) selected,










RAM Concept


) to




345

Chapter 47 • Check Skip start tendon, and click OK.

• Set Spacing to 2 m, and click OK. 7 With the Full-Span Tendon Panel tool (

) selected,












Orthogonal (

) and Snap

last choices. Alternatively, you could select Auto Connect, but you would have to uncheck Skip Start Tendon. 21 With the Full-Span Tendon Panel tool (

) selected,


).


) selected,




).








) selected,








mm, and click OK.






) selected,

draw tendons in the next panel: • Click at the center of the column at grid intersection A-2. • Click at the center of the column at B-2.


) selected,








346

) selected,



• Click at the center of the column at D-4. • Click at the center of the column at C-4. 26 In the Tendon Panel dialog box:

RAM Concept

Chapter 47 • Set Auto Connect.



Note: Auto-connect will ignore the tendons at the first click because there are already two tendon segments connected at that point. The panel in the top right has too many tendons and some should be deleted. 27 With the Selection tool (


), select all of the terminated tendon segments, other than those over a drop cap or within the balcony slab: • Fence the tendon segments that end on grid A. • Hold the Shift key down and repeat the procedure until you have selected all applicable end tendon segments (tendon segments terminating at grids B and D). 41 Right click on the plan and choose Selection Properties

this panel.




Delete.

mm and click OK.


) selected,

draw tendons that terminate in this panel: • Turn on Snap Orthogonal (




• Type r0,2.1. • Click at the last tendon profile point at 22, 17.5 m.




mm, and click OK.



centroid of the 250 mm slab, rather than the centroid of the drop cap.





segment at B-2.


mm, and click OK.


from the popup menu. ) selected,







to 5, and click OK. The longitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 250 mm slab.

RAM Concept

), select all of the terminated tendon segments over a drop cap, by: • Double clicking at grid intersection A-1.

).






).




).


the moved tendon. 55 Repeat for the tendon segment below the moved tendon.

Note: You could cut down the number of steps in moving the tendon from the opening by using the Utility tool. This combines the selection tool with move and stretch. Refer to

347

Chapter 47 “Expanding tool buttons” on page 6 and “Using the Utility tool to move and stretch” on page 20 for further information.


348

RAM Concept

Chapter 47



).


Note: Column Strip Width Calc is already set to Full Width. 2 Click the General tab. 3 Set the Environment to Full PT - 18.3.2(c).

Note: The Consider as Post-Tensioned box is already


checked in the CAN template. 4 Click the Column Strip tab. 5 Set Cross Section Trimming to Slab Rectangle. 6 Change CS Top Cover to 25 mm.




8 Click OK.

Generate Strips.



Generate Spans.




The Generate Spans dialog box opens with Spans to Generate set to Latitude. Accept the Minimum Span Length as 0.75 meters. 10 Click OK.




RAM Concept

349







).

).


Hatch the strips:


).








).

).



).









).



350

RAM Concept

Chapter 47




).







).

).





• Click OK.









Delete.




).

).



“horizontal”.

RAM Concept

351








).





).



5 Select the punch checks at B.8-1 and C-3. 6 Right click on the plan and choose Selection Properties

from the popup menu. 7 Change the Maximum Search Radius to 2 m. 8 Click OK.


352

RAM Concept

Chapter 47


The problem is that the cross sections are trimmed with the Slab Rectangle setting. For span segment 6-2, that setting is causing a problem because of the combination of the drop cap and thinner balcony slab. Edit span segment 6-2:




Spans Plan.







Calculate:

1 Click Calc All (

).






and click OK.


Recalculate:

1 Click Calc All (




).












RAM Concept

This shows “OK” for all design strips. “OK” means that there are no violations of code limits for ductility, flexural stress and one-way shear. Note that status does not flag excessive deflections.

353

Chapter 47 There are punching shear status results at each column. You can see these more easily on the dedicated punching plan.




Look at design reinforcement:

Plan. Concept has noted “Non-standard section” at six column locations and “OK with SSR” at one column. “Non-standard Section” is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three cases: interior, edge and corner. Concept still calculates a stress ratio for non-standard sections. Where the unreinforced stress ratio (USR) is less than 1.0, the column’s punching shear is satisfactory without any reinforcement (subject to the comments above concerning “Non-standard section)). Stud shear reinforcement is required where Concept reports “OK with SSR”.

Note: Choose > Layers > Design Status > SSR Plan to view the stud shear reinforcement. Figure 47-26 Design Status: Reinforcement Plan.

This shows all the code-determined reinforcement for each of the design strips. Since the slab is post-tensioned, there is not much reinforcement. You might choose to view all design reinforcement on the one plan, or you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom) and direction (latitude or longitude).Choose the plans that best convey the results without too much clutter. The Reinforcement layer plans show detailed reinforcement. In particular, the top bars are rationalized so that the number is consistent each side of columns.


354

RAM Concept

Chapter 47 Look at detailed top reinforcement:


Figure 47-28 Service Design: Top Stress Plan. Figure 47-27 Reinforcement: Top Bars Plan


47.7.3 Concrete stresses CSA A23.3 has limits for the hypothetical stresses due to flexure and axial loads. The code bases the rules upon “averaging” rather than peak values. Stress contour plots of the net flexural stresses are available in Concept. Most designers will not be interested in these plots because, in following the code, Concept does not use the contours directly in design. What will likely be of interest are the plans that show the concrete stresses plotted along the design strips. These are the average stresses based upon the design strip widths.




), or choose

Process > Calc Load History Deflections. View top stress plan:


Top Stress Plan. 2 Right click over the plan and choose Plot ( 3 In the Plot Settings dialog box:

• Change Max Frame # to 4.

The Maximum Short Term Load, Sustained Load, and Final Instantaneous Load History Deflection Layers provide contour plans for deflection.

). View maximum short term load deflection:



• Click OK

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355

Chapter 47

47.7.5 Bending Moments While it is not necessary to view bending moments, it can be useful, especially for irregular structures. Even though principal moments are important, the default moment contours plans are for Mx (moment about the x-axis) and My. This is because most designers detail reinforcement orthogonally, and the directions are usually the x- and yaxes. You can view moments about any axes, including the principal axes. It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful. View Ultimate LC Moments:

1 Choose Layers > Load Combinations > Factored LC:

1.25D + 1.5L + 1.5S > Max Mx Plan. The Mx contours should be visible. Let’s modify this plan to show moments for the “Standard” context (full load, with standard load factors) instead of the “Max” context (maximum value for any set of standard or alternate load factors and any load pattern).



) to change



).

3 In the plot window that opens, the Slab tab should be 1 Choose Layers > Load History Deflections> Sustained

active. Change the Context item from “Max” to “Standard”. Click OK.


Now let’s draw some section distribution plots.



)


).


intersection D-3. This shows the bending moment shape along the line you have drawn. 7 While pressing the Shift key, click at grid intersection B-

1, and then click at grid intersection B-3. This shows how Mx varies across the panel. See “Section distribution plots” on page 158 for more information.


356

RAM Concept




).


Objects dialog box and click OK. See “Calculating the balanced load percentages” on page 389 for more information.

Figure 47-31 Factored LC: 1.25D + 1.5L + 0.5S Max Mx Plan showing use of Plot Distribution tool.

RAM Concept

357

Chapter 47

358

RAM Concept

Chapter 48

48 Mat Foundation Tutorial This chapter will walk you through the steps for modeling a mat foundation, also known as a raft. Alternative metric values and units are identified in square brackets [] next to the US units. The metric values are not exact conversions. The code used is ACI 318-05.


For information on creating a new file, see “Creating and opening files” on page 5. You should ensure that you select “mat foundation” in the new file dialog box.

(

Most mats support columns and walls. You may choose to model the columns and walls but you should be aware that this could affect the mat behavior. In particular, if there are lateral loads then you should be very careful in defining the supports above as having no horizontal restraint. Otherwise, the supports above rather than the soil (springs) below could resist some lateral moment and shear.


A mat need not have columns and walls modeled above. The reasons to model columns and walls above include improving the appearance of the model, and providing snap points for point and line loads. Additionally, a wall above will stiffen the mat in a beneficial way.


4 Click Show All, and then click OK. Draw the slab area:


) and Snap to Point

).



properties. • Choose a Concrete Strength of 4000 psi [25 MPa for AS3600; C25/30 for BS8110 and EC2]. • Set Thickness to 30 inches [750 mm]. • Leave Surface Elevation as 0 and Priority as 1. • Click OK. ) selected, define the four corners of the slab by snapping to the imported drawing’s slab corners.

Note: You can type “c” to close the polygon instead of entering the last point. Define the column locations and properties:


1 Turn on Snap to Center (

).


The CAD file you import is located in your RAM Concept program directory. Import the CAD file:

).


• Choose a Concrete Strength of 5000 psi [32 MPa for AS3600; C32/40 for BS8110 and EC2].

1 Choose File > Import Drawing.

• Set Height to 10 feet [3 m].

2 Select the CAD drawing file mat_tutorial.dwg

• Set Support Set to “Above”.

[mat_tutorial_metric.dwg].

• Set Width to 30 inches [750 mm].

The File Units dialog box appears.

• Set Diameter to 30 inches [750 mm].

3 Select Inches [Millimeters] (the units used in the CAD

• Check “Roller at Far End”.

file) and click OK.

• Uncheck “Fixed Near” and “Fixed Far”. 4 Click OK. 5 Click at the center of all 11 column locations shown on

48.2 Define the structure


To use the CAD file you need to make it visible on the Mesh Input layer.



).

2 Double click on the Wall tool ( Show the drawing on the mesh input layer:


).


• Choose a Concrete Strength of 3000 psi [20 MPa for AS3600; C20/25 for BS8110 and EC2].


• Set Height to 10 feet [3 m].


• Set Support Set to “Above”.

RAM Concept

).

359

Chapter 48 • Set Thickness to 12 inches [300 mm]. • Uncheck “Shear Wall”. • Uncheck “Fixed Near” and “Fixed Far”. 4 Click OK. 5 Define each wall by snapping to the start and end points

of the wall centerlines shown on the CAD drawing. Define the area spring location and properties:

1 Double click on the Quad-Area Spring tool (

).

2 In the Default Area Spring Properties dialog box:

• Set an r-force constant of 0.1 pci [0.00001 N/mm3]. • Set an s-force constant of 0.1 pci [0.00001 N/mm3]. • Set a z-force constant of 250 pci [0.07 N/mm3], and click OK.

Note: You need horizontal springs (r and s) with very small stiffnesses since there are lateral loads. 3 Define an area spring over the entire slab by clicking four

corners of a quadrilateral. This shape need not match the slab’s exact dimensions, but should cover the entire slab. You have now defined the structure but the element mesh does not yet exist.

Figure 48-1 Mesh Input: Standard Plan

Generate the mesh:


).


2 feet [0.7 m]. 3 Click Generate. View the mesh:


You will now see a somewhat random mesh. This will still produce reasonable results, but will significantly improve when you regenerate it later on. View the structure:



) to rotate the

floor.

Figure 48-2 Element: Standard Plan

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4 Choose Edit > Paste.

Mat loads could consist of point, line and area loads for a number of loadings (such as live, other dead, north seismic, east seismic, north wind and east wind). For simplicity, this tutorial will not use area loads (except for the automatic calculation of self-weight) and will adopt loads belonging only to other dead, live, and ultimate seismic east loadings.

This pastes the other dead loads onto the Live (Reducible) Loading: All Loads Plan.


1 Choose Layers > Loadings > Other Dead Loading > All

Loads Plan. 2 Choose View > Visible Objects (

).


Showing the CAD file makes the following instructions easier to follow. 5 Turn on Snap to Intersection (

).

6 Double click the Point Load tool (

).

7 In the Default Point Load Properties dialog box:

• Change Fz to 40 Kips [180 kN], and click OK. 8 Define 40 Kip [180 kN] point loads by snapping to

column centers at the following locations: • A-1

Figure 48-3 Other Dead Loading: All Loads Plan

• A-3 • D-1 • D-3 9 Define the rest of the point loads as shown in Figures 48-

3 and 48-4. 10 Double click the Line Load tool (

).

11 In the Default Line Load Properties dialog box:

• Set Fz to 8 kip/ft [120 kN/m], and click OK. 12 With the Line Load tool (

) selected, draw a Line Load along the centerline of the wall on grid 2. 13 Repeat for the wall at grid “2.5” with a load of 5.5 kip/ft

[80 kN/m].

Note: Draw these loads to the outside face of the intersecting walls. Copy to the live (reducible) loading layer:

For simplicity, use the same loads for other dead and live (reducible) loads 1 With the Selection tool (

), select all of the other dead loads by fencing the entire slab. 2 Choose Edit > Copy.

Figure 48-4 Other Dead Loading: All Loads Plan [METRIC]


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Chapter 48 Define the ultimate seismic east loading:

8 Double click the Line Load tool (

1 Choose Layers > Loadings > Ultimate Seismic East

Line Load Properties dialog box:

Loading > All Loads Plan.

) and in the Default

• Set Fy to -12.8 kip/ft [-174 kN/m].


).

• Click OK.


9 Draw a line load by snapping to the wall intersection


points, as shown in Figure 48-7 and Figure 48-8.



).



Line Load Properties dialog box: • Set the elevation above the slab surface to 360 inches [9000 mm]. • Set Fx to 4.1 kip/ft [60 kN/m].


Line Load Properties dialog box: • Set Fy to (+)12.8 kip/ft [(+)174 kN/m]. • Click OK. 11 Draw a line load by snapping to the wall intersection


• Set all other items in the dialog box to 0. • Click OK. 7 Draw a line load by snapping to the wall intersection


Figure 48-7 East Seismic: All Loads Plan (second set)

Figure 48-5 East Seismic: All Loads Plan

Figure 48-8 East Seismic: All Loads Plan (second set) [METRIC]

Note: The seismic loads are approximations for a fivestorey building. The load elevation is the average floor height (third storey). Figure 48-6 East Seismic: All Loads Plan [METRIC]

Note: The loads in the y-direction cancel the couple about the mat centroid.

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48.4 Create the design strips Design strips are an essential part of RAM Concept because they link finite element analysis with concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for section design. There are two directions called Latitude and Longitude. Draw latitude design strips:

1 Choose Layers > Design Strip > Latitude Design Spans


).

3 The Default Span Properties dialog box opens to the Strip

Generation properties. • Set Column Strip Width Calc to Code Slab (this is the default for the AS3600 template).

Figure 48-9 Generate spans dialog box


• Click the General tab. • Uncheck the Consider as Post-Tensioned box. • Click the Column Strip tab. • Change CS Top Bar and CS Bottom Bar to #8 [N25 for AS3600; T25 for BS8110; H25 for EC2]. • Change CS Top Cover and CS Bottom Cover to 2 inches [50 mm]. • Set the Min. Reinforcement Location to Tension Face. • Click the Middle Strip tab. • Check the Middle Strip uses Column Strip Properties box. • Click OK. 4 Click the Generate Spans tool ( Generate Spans.


5 The Generate Spans dialog box opens with Spans to

Generate set to Latitude (as shown in Figure 48-9). 6 Click OK.


Choosing span segments in a mat is a subjective matter. Concept uses imperfect algorithms that do not always produce acceptable span segments and span segment strips. It is recommended that some span segments in this tutorial are deleted. 7 With the Selection tool (

), select the seven span segments highlighted in red in Figure 48-10 and press Delete.

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Chapter 48 Regenerate the latitude span strips:






Generate Strips.

Generate Strips. The design strips appear in the latitude direction. Hatch the strips:


).

The Visible Objects dialog box will appear. 2 Check Hatching under Latitude Span Segment Strips, and click OK.


Figure 48-12 Latitude design strips after editing and regeneration. Draw longitude design strips:


Spans Plan. 2 Choose View > Visible Objects (

).

3 Click the Drawing Import tab. 4 Click Show All, and then click OK. 5 Double click the Span Segment tool ( Figure 48-11 Latitude design strips (with hatching turned on). Some editing is now required.

).

6 Click the Column Strip tab. 7 Change CS Top Cover and CS Bottom Cover to 3 inches

Two span segments are slightly skewed. How you treat skewed strips is also a subjective matter, but in this tutorial we suggest the span segment strips’ cross sections are manually reoriented.

[75 mm], and click OK. 8 Click the Generate Spans tool (




Edit the cross section orientation:


), select span segments 5-2 and 6-2 as shown in Figure 48-11.


2 Click the Orient Span Cross Section tool (

• Click OK.


).

).

10 The spans appear in the longitude direction, as shown in

4 Click near one of the span segments, and then again

Figure 48-13.

above or below the first click.

Similar to the latitude direction, some editing of the span segments is required.


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choose Selection Properties. 19 In the dialog box:

• Uncheck Detect Supports Automatically. • Uncheck Consider End 2 as Support. • Change Support Width at End 1 to 12 inches [300 mm], and click OK.



), select the span segments over the walls (highlighted in red in Figure 48-13) and press Delete. 12 Turn on Snap to Intersection (

).

13 With the Span Segment tool (

), draw a span segment by clicking at the wall intersections at point A and B in Figure 48-14. 14 Choose Edit > Selection Properties, or right-click and

choose Selection Properties.

Figure 48-14 Manually drawn span segments

15 In the dialog box, change:

• Min Number of Divisions to 0.


• Max Division Spacing to 30 feet [10 m], and click OK.


This span segment has been drawn to assist with Concept’s span segment strip width calculation. 16 Turn on Snap Orthogonal (

Snapable Point (

) and Snap Nearest

).

17 With the Span Segment tool (

), draw a span segment by clicking at the wall intersection at point B and then at point C in Figure 48-14 (it should snap to the visible grid line).

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Generate Strips. The design strips appear in the longitude direction. Two span segments are slightly skewed. We suggest the span segment strips’ cross sections are manually reoriented.

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Figure 48-15 Longitude design strips (with hatching turned on). Some editing is now required. Figure 48-16 Longitude design strips after editing and regeneration Edit the cross section orientation:


), select span segments 9-3 and 12-1 as shown in Figure 48-15.

Note: Many of the latitude and longitude design strips

The orientation line half way along the span strip is now “horizontal”.

(span segment strips) have different widths either side of a column. You could rationalize these strips such that they have similar widths at the column, especially the cantilevers. See the discussion in “Defining strip boundaries manually” on page 102 of Chapter 22, “Defining Design Strips”. In particular, Example 22-2 on page 103 and Example 22-4 on page 104.

Regenerate the longitude span strips:


2 Click the Orient Span Cross Section tool (

).

3 Click near one of the span segments, and then again to the

left or right of first click.


Generate Strips.



).


box: • Change Cover to CGS to 3 inches [60 mm] (cover to centroid of top reinforcement). • Click OK. 4 Fence the slab with the Punching Shear Check tool.

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).

2 Enter Element Size of 2 feet [0.7m] and click Generate.



48.5 Regenerate the mesh The presence of design strips can significantly improve the regularity of the finite element mesh. We recommend that once you have completed the design strips, you regenerate the mesh.

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48.6 Calculate and view the results

Concept has noted “Non-standard section” at the corner column locations.

After you run the model, you can view the results of the analysis and design calculations.

“Non-standard Section” is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three ACI 318-02 cases: interior, edge and corner. Concept still calculates a stress ratio for nonstandard sections. Refer to “Non-Standard Sections: ACI 318 and CSA A23.3” on page 162 of Chapter 29 for more information.


1 Choose > Criteria > Calc Options 2 Review the options. 3 Uncheck “Auto-stabilize structure in x- and y-direc-

tions”, and click OK.

Note: See “General options” on page 150 of Chapter 28 for more information. Calculate:

Click Calc All (


Look at reinforcement and design status:

1 Choose Layers > Design Status > Total Status Plan.

This shows OK for all design strips and punching checks. This means that there are no violations of code limits for ductility, one-way shear, and punching shear. Note that status does not flag excessive deflections.


3 Choose Layers > Design Status > Total Reinforcement

Plan. This shows all the code-determined reinforcement for each of the design strips. The results are, however, too congested to be useful. You can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom), direction (latitude or longitude), and type (flexural or shear). You should decide which plans best convey the results without too much clutter. View Specific Reinforcement:


Reinforcement Plan. Figure 48-19 Design Status: Status Plan.

There are punching shear status results at each column. You can see these more easily on the dedicated punching plan.


).

The Visible Objects dialog box will appear. 3 Check Bar Spacings under Latitude Span Designs, and

click OK.


Plan.

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Figure 48-22 Service LC: Soil Bearing Pressure Plan.

2 Choose Layers > Rule Set Designs > Soil Bearing Design

48.6.1 Bearing stresses

> Max Soil Bearing Pressure Plan.

Maximum bearing stress is a critical consideration when designing a mat. Contour plots of the bearing stresses are available in RAM Concept. These will vary according to the load combination. Note that the minimum and maximum bearing values often occur for different load combinations. The Soil Bearing Design rule set envelopes the maximum and minimum bearing pressures for all load combinations. The maximum bearing pressure plan is probably the most useful for your design. View bearing stress plans:


Soil Bearing Pressure Plan.

Figure 48-23 Soil Bearing Design: Max Soil Bearing Pressure Plan

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49 Strip Wizard Tutorial This chapter walks you through the steps for using Strip Wizard to provide a preliminary design for the slab (grid B) in the PT Flat Plate Tutorial.

7 Click Next to proceed to the Span Data page.

Alternative metric values and units are identified in square brackets [] next to the US units. The metric values are not exact conversions.

49.3 Enter the span data

The codes used are ACI 318-02, AS3600-2001, BS8110:1997, EC2 - 2004 and IS 456.

Enter the span dimensions and data on the Span Data page. (The type of data entered depends on which structural system you chose on the General Parameters page.)

For more information, see “Using Strip Wizard” on page 193.

Set the span data as follows:

1 Set the length of Span 1 and 2 to 30 ft [9 m]. 2 Set the length of Span 3 to 25 ft [7.75 m].

49.1 Start Strip Wizard

3 Set the thickness of all three spans to 10 inches [250 mm].

Note: To set all the values in a column at once, enter the When you choose File > Strip Wizard, the New File dialog automatically opens before the Strip Wizard dialog box is opened. After you create the new RAM Concept file, the Strip Wizard dialog appears.

value in the “Typical” row (first row) of that column. For example, for the step above, you can simply type 10 [250] in the “Typical” row of the “Thickness” column to set the thickness of all three spans to 10 inches [250 mm]. 4 Set the left start width of Span 1 to 11.5 ft [3.5 m].

Start the Strip Wizard:

1 Choose File > Strip Wizard. 2 In the New File dialog box, set the Structure Type to

Elevated and choose the Code. 3 Click OK. 4 The Strip Wizard dialog box appears; click Next to

proceed to the General Parameters page.

5 Set the left start width of Span 2 and 3 to 15 ft [4.5 m]. 6 Set the right start width of Span 1 and 2 to 14 ft [4.25 m]. 7 Set the right start width of Span 3 to 1 ft [0.3 m]. 8 Set the left end width of Spans 1, 2 and 3 to 15 ft [4.5 m]. 9 Set the right end width of Span 1 and 2 to 14 ft [4.25 m]. 10 Set the right end width of Span 3 to 1 ft [0.3 m].

49.2 Set the general parameters On the General Parameters page, you define the structure type, number and type of spans, and concrete mixes. Set the general parameters as follows:

1 Choose Two-Way as the structural system. 2 Check “Post-tensioned”. 3 Set the number of spans to 3. 4 Check “Asymmetric strip”. 5 Set the concrete mix for slabs and beams to 5000 psi [32

MPa for AS3600; C32/40 for BS8110 and EC2; M40 for IS 456]. 6 Set the concrete mix for supports to 5000 psi [32 MPa for

Figure 49-1 The Span Data page.

AS3600; C32/40 for BS8110 and EC2; M40 for IS 456]. 11 Click Next to proceed to the Support Data page.

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49.4 Create the supports below

Set the loads as follows:

1 Set the typical Dead Area Load to 20 psf [1 kN/m2].

Add the four supports in the Supports Below table on the Support Data page.

2 Set the typical Live Area Load to 40 psf [2 kN/m2]. 3 Click Next to proceed to the Post-Tensioning page.

Set the supports below as follows:

Note: You can leave the Dead Line Load and Live Line

1 Set the depth of all four supports below to 24 inches [600

Load fields blank (no need to enter zero).

mm]. 2 Set the width of all four supports below to 24 inches [600

mm].


3 Set the height of all four supports below to 10 ft [3 m]. 4 Leave the bottom and top fixity of all supports below as

“Fixed”.

Enter the post-tensioning parameters on the PostTensioning page.

5 Click Next to proceed to the Drop Caps and Drop Panels Set the post-tensioning as follows:

page.

1 Uncheck the stressing “Start” and “End” check boxes. 2 Set the minimum P/A to 140 psi [1 MPa].

49.5 Add drop caps

3 Set the minimum balance load percentage to 65%. 4 Click Next to proceed to the Reinforcement page.

Enter the dimensions for a drop cap at Supports 2 and 4 in the Drop Caps table (top table) on the Drop Cap and Drop Panels page. Set the drop cap data as follows:

49.8 Specify the reinforcement parameters

1 For Support 2 in the Drop Caps table set the following

values: • Set the thickness to 20 inches [500 mm].

Enter the reinforcement parameters on the Reinforcement page.

• Set the left width to 22.5 inches [600 mm].

Set the reinforcement as follows:

• Set the right width to 22.5 inches [600 mm].

1 Set the top reinforcing bar to #5 [N16 for AS3600; T16

• Set the before length to 22.5 inches [600 mm]. • Set the after length to 22.5 inches [600 mm]. 2 For Support 4 in the Drop Caps table set the following

values: • Set the thickness to 20 inches [500 mm]. • Set the left width to 33 inches [900 mm]. • Set the right width to 12 inches [300 mm].

for BS8110 and IS456; H16 for EC2]. 2 Set the bottom reinforcing bar to #4 [N12 for AS3600;

T12 for BS8110 and IS456; H12 for EC2]. 3 Set the top and bottom reinforcement clear cover to 1

inch [25 mm].

Note: Strip Wizard does not differentiate between cover to tendons and reinforcement bar. 4 Check the Perform punching shear checks box.

• Set the before length to 33 inches [900 mm].

5 Set Cover to CGS to 1.625 inch [41 mm].

• Set the after length to 0 inches [0 mm].

6 Click Next to proceed to the Completion page.

3 Click Next to proceed to the Loads page.

49.9 Complete the Strip Wizard 49.6 Specify the loads Enter the area loads on the Loads page.

372

Completing the Strip Wizard is the final page of the Strip Wizard dialog box. You can save the data you just entered in a Strip Wizard Settings file by clicking Save. When you click Finish, Strip Wizard creates your strip in the open RAM Concept file.

RAM Concept

Chapter 49 Complete the strip:

1 Click Save and name the file in the Save Strip Wizard

File As dialog box that appears. 2 Click Finish.

49.10 Proceed with RAM Concept After you have completed Strip Wizard, you can proceed with RAM Concept. After you have created your strip, generate the mesh (with a 2.5-foot [0.75 m] mesh) and run a calculation analysis. Refer to the relevant manual chapters, or one of the three PT Flat Plate tutorials for further information. View your strip:


Figure 49-5 The completed strip on the ManualLatitude Tendon: Standard Plan.

49.11 Comparison with PT Flat Plate Tutorial The results of the Strip Wizard analysis are similar but not the same as the PT Flat Plate Tutorial. The reasons for different results include: • Strip Wizard does not automatically consider transverse continuity effects. • Increased balcony loads not considered by Strip Wizard. • Strip Wizard automatically modified the drapes in spans 2 and 3 (you can change these if you wish).

Figure 49-2 The completed strip on the Mesh Input: Standard Plan.

• Longitude tendons not considered by Strip Wizard.

49.12 Conclusion

Figure 49-3 The Element: Standard Plan showing the completed strip after the mesh has been generated.

Strip Wizard allows you to perform a preliminary or final design for a strip within a floor. The results are similar to those generated by any strip program, but not as accurate as a RAM Concept model that considers all of the irregularities within a floor.

Figure 49-4 The Element: Standard Plan after calculation and mesh regeneration.

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50 Analysis Notes This chapter provides general information on finite element method (FEM) plate analysis as well as specific information on how RAM Concept calculates analysis results.

50.1 Review of plate behavior In RAM Concept, slab areas are modeled as plates. Engineers have historically used approximate methods for designing plates; these approximate methods assume that the plate behaves in a beam-like manner in two perpendicular directions. Because engineers have used these approximate methods for so long, RAM Concept’s true elastic plate analysis results can sometimes be confusing. This section will review plate analysis theory, so engineers can better understand RAM Concept’s results.

50.1.1 In-plane and out-of-plane behavior Slabs are subject to both in-plane and out-of-plane forces. In-plane forces stretch and shear the slab, but do not cause it to deviate from the plane defined by the slab centroid. For horizontal slabs (like those in RAM Concept), in-plane forces cause stretching, compressing and shearing of the centroid plane in plan view only. Out-of-plane forces cause the slab to bend and twist, moving it perpendicular to the plane defined by the slab centroid. For horizontal slabs (like those in Concept), out-of-plane forces cause the slab to deflect vertically from the original centroid plane. In a horizontal slab that has one continuous centroid elevation, the equilibrium equations of in-plane and out-of-plane forces are totally separate. However, if there is a shift in the centroid, the two sets of forces become interrelated due to equilibrium considerations and must be solved for simultaneously; RAM Concept handles this interrelation automatically. For slabs that are not made of a linear-elastic material, the strains due to the in-plane and out-of-plane forces can no longer be linearly superimposed, so the equilibrium equations of the two force systems become indirectly related through their strains. This interrelation of the two force systems’ strains for non-linear elastic materials can be seen in the simple example of a flat concrete slab that is subject to transverse loads that cause out-of-plane forces and deflections. If a uniform in-plane compression force is applied to the same slab, the slab will have less cracking, smaller out-of-plane displacements and a somewhat different out-of-plane force pattern. Concept’s global analysis of structures assumes that the concrete behaves like a linear-elastic material. However, the following discussion of the in-plane and out-of-plane forces is based purely on equilibrium considerations, and therefore is valid for any material.

Note: “P-delta” effects are not considered. 50.1.2 In-plane behavior In-plane forces can be quantified as an axial stress in two perpendicular directions, along with a shear stress. For a differential element (with no loads applied) the stresses are shown as follows:

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From equilibrium considerations, the variation of the in-plane forces can be shown to be: ∂Fx/∂x + ∂Vxy/∂y = -Px ∂Fy/∂y + ∂Vxy/∂x = -Py where Px and Py are applied loads. If a different set of coordinate axes is used for references, the forces in terms of these new axes have a Mohr’s circle relationship to the forces in terms of the original axes:

Fr = Fx cos2 α + Fy sin2 α + 2Fxy sin α cos α Fs = Fx sin2 α + Fy cos2 α – 2Fxy sin α cos α Vrs = Vxy (cos2 α –sin2 α) + (Fy – Fx) sin α cos α This Mohr’s circle relationship is based on equilibrium considerations, so it is valid for all materials. For every point in the slab there will be a set of two perpendicular “principal axes” where the shearing stresses are zero and the forces in the two perpendicular directions are at their maximum and minimum values. The angle between the principal axes and the x- and y-axes will vary from point to point in the slab.

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50.1.3 Out-of-plane behavior Out-of-plane forces can be quantified as bending moment about two perpendicular axes, a torsional moment and vertical shears on the two perpendicular faces. For a differential element the moments and shears are shown as follows:

From equilibrium considerations, the variation of the out-of-plane forces can be shown to be: ∂Vxz/∂x + ∂Vyz /∂y = -Pz ∂Mx/∂y + ∂Txy/∂x = -Vyz ∂My/∂x + ∂Txy/∂y = -Vxz where Pz is an applied load. If a different set of coordinate axes is used for references, the moment in terms of these new axes have a Mohr’s circle relationship to the forces in terms of the original axes, the shear forces have a simple vector-like relationship:

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Mr = Mx cos2 α + My sin2 α - 2Txy sin α cos α Ms = Mx sin2 α + My cos2 α + 2Txy sin α cos α Trs = Txy (cos2 α –sin2 α) + (Mx – My) sin α cos α

Vrz = Vxz cos α + Vyz sin α Vsz = -Vxz sin α + Vyz cos α Again, these relationships are based on equilibrium considerations, so they are valid for all materials. For every point in the slab there will be a set of two perpendicular “principal axes” where the torsion moments are zero and the bending moments about the two perpendicular directions are at their maximum and minimum values. The angle between the principal axes and the x- and y-axes will vary from point to point in the slab.

50.1.4 Interaction of in-plane and out-of-plane behavior Where the centroid plane of a slab changes elevation, there is an interaction of in-plane and out-of-plane forces. The interaction of the two sets of forces is simple and is defined purely by moment and force equilibrium. A simple centroid step is shown in elevation view below:

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Fx ’ = Fx Vxy’ = Vxy Vxz’ = V xz My’ = My - Fx d Mxy’ = Mxy - Vxy d

50.1.5 RAM Concept plotting and relevant axes RAM Concept can plot its results relative to the x-axis, the y-axis, a specific axis (specified with an angle) or a maximum or minimum axis. The minimum axis is defined as the axis at each and every point that gives the minimum value for the quantity being plotted; the angle of the axis used will vary from point to point in the plot. Similarly the maximum axis is defined as the axis at each and every point that gives the maximum value for the quantity being plotted; the angle of the axis used will vary from point to point in the plot.

50.2 Finite element analysis RAM Concept uses a linear-elastic finite element formulation based on gross section properties for its global analysis.

50.2.1 About finite element analysis Finite element analysis (also known as the finite element method) has become the standard way for engineers to analyze complicated structures. While explaining the theory of the finite element method is beyond the scope of this chapter, engineers using RAM Concept should understand how the parameters they specify affect the program's analysis.

50.2.2 Finite element formulation used in RAM Concept RAM Concept models the slab portion of the structure with triangular or quadrilateral slab elements. These slab elements are based on a formulation by Robert Cook [“Two Hybrid Elements for Analysis of Thick, Thin and Sandwich Plates”, International Journal for Numerical Methods in Engineering, Volume 5, pages 277-288, 1972]. The elements consider both in-plane and bending deformation. Five degrees of freedom are used per node.

50.2.3 Slab element general properties The slab elements used in RAM Concept have the following general properties: • The elements consider both in-plane and out of plane forces.

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Chapter 50 • The elements can (optionally) have different stiffnesses in two orthogonal directions. • The elements consider transverse shear deformations. • The elements consider the relative elevations of adjacent slab elements.

50.3 Orthotropic behavior RAM Concept allows you to specify six stiffness factors that modify the behavior of the slab elements (see description of the orthotropic behavior settings in “Slab area properties” on page 70 and “Beam properties” on page 72 of Chapter 17, “Defining the Structure”). When all of the factors are set to 1.0, the slab element behave as an isotropic material (a material having the same properties in all directions). When the factors are different from each other, the slab elements behave as an orthotropic material (a material having different properties along its three perpendicular axes.) Care must be used when setting these stiffness factors. With certain combinations of factors, the structure can become unstable and the results can become unreliable. Also, the interaction of the stiffness factors may be more complex than it appears upon first inspection. This section gives some guidance to assist in avoiding these issues.

50.3.1 K Factors and Instability When K factors other than 1 are used (either directly, or indirectly by setting the slab or beam Behavior), it is possible that the structure may become unstable or nearly unstable. This is generally not a problem unless the Custom option is used. Interaction of KMrs and KMr or KMs Stiffness Factors

If custom settings are used, and both KMrs and KMr or both KMrs and KMs are reduced, the elements may become unstable and the analysis results may be suspect. For this reason we recommend that these parameters be kept within a limited range: • KMr / KMs > 0.5 or KMrs / KMs > 0.5 • KMs / KMr > 0.5 or KMrs / KMr > 0.5 Similar instabilities can occur with KVrs and KFr/KFs.

50.3.2 Interaction of in-plane and out-of-plane stiffnesses In situations where the centroid of the slab is not at a uniform elevation, the in-plane and out-of-plane stiffnesses of Concept's slab elements will interact. For example, in a T-beam, the axial stiffness of the web and the flanges will interact with their bending stiffnesses (creating a stiffer section than just the web and flange bending stiffnesses added together). In these situations, you may need to modify the in-plane behavior to modify the out-of-plane behavior. For example, if you want to reduce a T-beam bending stiffness by half, you would need to set both KMs and KFr to 0.5.

50.4 Deep beam considerations

50.4.1 Analysis of slab and beam elements RAM Concept assumes that beam elements and slab elements behave the same; unless their “behavior” is specified for the finite elements. The first analysis assumption that Concept makes for slab elements is that “linear sections remain linear”; this is analogous to “plane sections remain plane” in beam theory.

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Figure 50-6 Linear Sections Before Deformation

Figure 50-7 Linear Sections After Deformation

The second analysis assumption that RAM Concept makes for slab elements is that the force and stress patterns in the element are that of a typical slab location. The following table shows the possible slab element forces and their associated stresses. Symbol Force

Related Stress

Fx

Axial force on x-face

Uniform axial stress σx

Fy

Axial force on y-face

Uniform axial stress σy

Vxy

In-plane shear force

Uniform shear stress σxy

Vxz

Transverse shear force on x-face Parabolic (along z-axis) shear stress σxz

Vyz

Transverse shear force on y-face Parabolic (along z-axis) shear stress σyz

Mx

Bending moment about x-axis

Linear (along z-axis) axial stress σy

My

Bending moment about y-axis

Linear (along z-axis) axial stress σx

Txy

Torsional moment

Linear (along z-axis) shear stress σxy

Table 50-4 Relation between force and stress

Figure 50-8 In-Plane Actions (Plan View)

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Figure 50-9 Out-of-Plane Actions (Plan View)

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50.4.2 Analysis and design of deep beams For bending moment and shear Because RAM Concept assumes that deep beams behave like slabs, Concept will assume a linear distribution of bending stress over the deep beam, while the actual stress distribution will be non-linear.

Figure 50-10 RAM Concept Analysis Bending Stresses

Figure 50-11 “True” Bending Stresses

These analysis simplifications are generally not significant and are normally ignored. In design, Concept will not perform any special capacity calculations that are appropriate only for deep beams and Concept will not provide any deep beam detailing information. Concept’s shallow beam calculations will generally be conservative for deep beams. The engineer will need to ensure that the deep beam is laterally stable. The engineer will also need to provide appropriate detailing for the deep beam.

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50.4.3 Analysis and design of deep beams with transverse bending moments Because RAM Concept assumes that deep beams behave like slabs, Concept will over-estimate the stiffness of a deep beam subjected to transverse bending moments. Concept’s analysis will assume that the entire beam is effective in resisting the transverse moment.

Figure 50-12 RAM Concept Analysis Bending/Axial Stresses

Figure 50-13 “True” Bending/Axial Stresses

This over-estimation of the stiffness is generally not significant and is normally ignored. In design, it is important that Concept’s design sections have the appropriate ignore depth settings, so only the portion of the beam that is truly effective is used in the capacity calculations.

Figure 50-14 Before Ignore Depth

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Figure 50-15 After Ignore Depth

50.4.4 Analysis of deep beams with torsion Because RAM Concept assumes that deep beams behave like slabs, Concept will over-estimate the torsional stiffness of deep beams. At the worst case, Concept’s assumptions lead to a torsional stiffness at the deep beam that is proportional to bh3, while the true torsional stiffness is proportional to b3h. Typically Concept’s overestimation is not that great as the slab elements have a transverse shear stiffness that makes the beams more flexible. The larger the number of elements across a deep beam, the smaller the overestimation of torsional stiffness.

Figure 50-16 RAM Concept Analysis Torsion Shear Stresses

Figure 50-17 “True” Torsion Shear Stresses

The torsion in the beam may be necessary for a complete structural load path - for this reason it cannot be ignored. It may be appropriate to reduce the torsional stiffness of the beam (this will modify the structural load path to one that is less

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Chapter 50 dependent upon the beam torsional capacity). Concept provides four options of considering this torsion in design. See “Torsion Considerations” on page 405 for more information.

Note: When the torsion stiffness of a beam has been reduced using a “K-factor”, it is generally recommended to provide a minimum level of torsion stirrups/ligatures/links to ensure that the beam can torsionally crack without precipitating a failure.

50.4.5 Analysis and design of moment transfer through step-beams Because RAM Concept assumes that deep beams behave like slabs, Concept will not consider that a step beam could bend about its longitudinal axis. Concept’s assumption that “linear sections remain linear” prohibits this type of bending and will cause Concept to over-estimate the stiffness of the step-beam for moment transfer.

Figure 50-18 RAM Concept Step-Beam Bending Stresses

Figure 50-19 “True” Step-Beam Bending Stresses

This over-estimation of the stiffness is generally not significant and is normally ignored. However, it is up to the engineer to assure that step-beam has the capacity and detailing to transfer the analyzed moment.

50.5 Wall behavior

50.5.1 Walls above slab RAM Concept considers walls above the slab to act as beams. It appropriately analyzes the influence of these walls on the slab, but it does not report the wall-beam forces nor does it design the wall-beams. Design strips and design sections that cross walls ignore both the capacity of the wall-beam in the cross section and the forces in the wall-beam. Wall-beams interpret some wall properties differently than walls below the slab:

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Chapter 50 Fixed Near = wall has torsional stiffness Fixed Far = (ignored) Shear Wall = beam has axial stiffness Compressible = (ignored) Note that while the prediction of the bending behavior of the slab and beam is accurate, the division of shear between the wall and the slab is not well predicted. For a combined wall-beam / slab section the proportion of the vertical shear force carried by the slab will be between the two extremes: As / Atotal, and Is / Itotal Where As = cross-sectional area of slab in section Atotal = cross-sectional area of slab and wall together Is = moment of inertia of slab Itotal = moment of inertia of slab and wall together

50.6 Post-tensioning loadings

50.6.1 Hyperstatic loading RAM Concept calculates the effects of the hyperstatic loading for all objects (elements, springs, support, design sections, design strip segment cross sections and punching checks) by using the following vector relationship: Fh = Fb - F p where Fh = the hyperstatic forces and moments Fb = the balance loading forces and moments (tendon forces on real structure) Fp = the “primary” forces and moments in the object (forces in object due to PT if the object was not restrained, but still contained tendons – if any) For objects that do not contain tendons (walls, columns, springs, rigid supports, design sections without tendons and design strips without tendons), Fp is zero, so: Fh = Fb For slab elements the calculation of Fp for every element is not performed, as there is no clear definition of Fp for anything except a cross section. Concept’s slab analysis plots assume Fp = Fb (Fh = 0), but these plotted values are NOT used in the slab design and checking. Concept calculates design section and design strip cross section forces (without the assumption of Fp = Fb) as follows: Fh = Fb - F p

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Chapter 50 Concept bases the calculation of Fp on the tendons at each cross section.

Note: Because of this issue, it is incorrect to use Concept’s slab analysis plots for cross-section design values in PT structures. (It is not recommend using slab analysis plots in RC slabs either, but that is because design strips and design sections provide much higher accuracy).

Note: For a more detailed discussion, refer to “Complete Secondary (Hyperstatic) Effects” by A. Bommer; PTI Journal, January 2004, Vol 2 No. 1).

50.7 Self-equilibrium analysis RAM Concept can analyze loadings using a self-equilibrium analysis.

50.7.1 About self-equilibrium analysis Any static loading on a structure, when combined with the structure support reactions (considered as additional loads), is a self-equilibrium loading. In such a loading the total loads upon the structure are in force and moment equilibrium. However, the equilibrium loads still produce moments and forces in the structure. In certain cases, it is desirable to analyze a self-equilibrium loading upon a floor system while ignoring the effects of the floor system supports. We call this type of analysis a self-equilibrium analysis.

50.7.2 Uses of Self-Equilibrium Analyses Load Paths Compatible with Full Building Lateral Analysis

The most common use of self-equilibrium analyses is to ensure that a load path in Concept is consistent with a load path in a lateral analysis performed by a separate program. If a lateral analysis of a building (perhaps using RAM Frame) is performed, and that analysis considers the slab to be part of the lateral load path, the slab - including the slab-column connections - needs to be designed to resist the forces and moments determined in the lateral analysis. This design can be performed using a self-equilibrium analysis. The forces/reactions from all of the supports (above and below the slab) onto the slab are considered as loads to the slab, any forces directly applied to the slab (such as a story-force in a seismic analysis) are also included. The result of this self-equilibrium analysis is a slab load path that is fully consistent with the lateral analysis of the entire building. The distribution of forces (and the displacements) within the slab may not match those in the building lateral analysis, but the distribution of slab forces in Concept is almost always more accurate than those predicted in the fullbuilding analysis. Other Uses

While there are other potential uses of the self-equilibrium analysis, they are rare and not covered in this manual.

50.7.3 Using Self-Equilibrium Analyses Setting the Loading Analysis Type

To have Concept analyze a loading using a self-equilibrium analysis, the loading's analysis type must be changed to “Lateral SE” (lateral self equilibrium). The loading analysis type can be changed in the loading window. See “Changing Analysis” on page 35 of Chapter 10, “Specifying Loadings”.

Note: The term “Lateral SE” is used instead of “Self Equilibrium” to remind users that this analysis type is primarily intended for lateral loadings.

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There is no limit to the type or quantity of loads that can be applied in a self-equilibrium loading. However, the loads applied must be nearly in self-equilibrium. If the loads are out of equilibrium Concept will apply restraints to the slab to ensure that equilibrium can be maintained. The restraint reactions can be viewed in the Calc Log.

Note: See “Importing a database” on page 49 of Chapter 14, “Importing a Database from the RAM Structural System” for information on how to automatically import self-equilibrium lateral loads. Note: Mat/Raft foundations are typically not well suited for self-equilibrium analyses as the soil reactions are not known before the analysis.

50.7.4 Self-Equilibrium Analyses Details “Floating” Stiffness Matrix

If you use self-equilibrium loadings, Concept creates an internal floating stiffness matrix in addition to the regular stiffness matrix. The floating stiffness matrix considers the slab, but not the supports above or below the slab. Concept also adds some minimal supports to the matrix to make it stable. Minimal Supports

The minimal supports that Concept adds to the floating stiffness matrix are located at real support locations, but not at every real support location. Typically, Concept adds three supports to provide full stability, but not to provide any restraint.

Note: Concept gives a warning if there are not at least two support locations where minimal supports can be added. The motivation for adding the minimal supports at the same location as real supports is that these locations are likely to be locations where self-equilibrium loads are applied, so any reactions at these locations can typically be considered as “corrections” to the self-equilibrium loads. Punching Check Reactions

Punching checks consider the loads applied at the punching check location in their reaction calculations. Punching checks are the only “support” that have reactions from self-equilibrium analyses. Displacements

Concept reports all displacements for self-equilibrium loadings as zero. Self-equilibrium loadings have no effect on the displacements calculated for load combinations or rule sets. Pattern Loading

Pattern loading can be used in a self-equilibrium analysis, but it should almost never be used. When used, all patterns should contain a self-equilibrium set of loads.

Note: For an example, see Example 39-1 on page 209 of Chapter 39, “Frequently Asked Questions”.

50.8 Design strip and design section forces

50.8.1 Design section axes and sign convention Design sections have a local coordinate system, with r, s and z axes: • R-axis is collinear with the design section and is positive in the direction from end 1 to end 2. This direction is also referred to as “Lateral”. • S-axis is 90 degrees counter-clockwise to the r-axis (still in the x-y plane) and goes through the “design centroid” (see below). This direction is also referred to as “Axial” 388

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Chapter 50 • Z-axis is parallel to the global z-axis and goes through the “design centroid”. This direction is also referred to as “Vertical” Forces for the design section are considered as the forces that the structure in the positive-s region applies to the structure in the negative-s region. A design section drawn from point B to point A will have the same forces as a design section drawn from point A to point B except that the following two forces will have opposite signs: • Vz (vertical shear on the s-face) • Mz (moment about the z axis)

50.8.2 Design strip segment axes and sign convention Design strip segments have a local coordinate system for each internal cross section. An internal cross section is perpendicular to the design strip segment spine and extends from the left tributary boundary to the right tributary boundary. Each internal cross section is treated exactly like a Design Section with its own r, s and z axes (see above). All of a DSS’s cross sections will have coordinate systems that are parallel, but for certain structure geometries the s-axes of each cross section will not be collinear. This is due to each cross section determining its own “design centroid” (see below).

50.8.3 Design centroids Each design strip (span segment strip) segment cross section and design section and determines its own design centroid location. The location is determined as follows: 1 A final cross section is determined by considering (i) the trimmed cross section for design strip segments, and (ii) the top

and bottom “ignore” depths for design sections. 2 The centroid z-elevation of this final cross section is the design centroid z coordinate. 3 A cross section “core” is determined (see “Concrete “Core” Determination” on page 405). For a T shaped section the core

will be the stem from the bottom of the section to the top of the section. For a rectangular section, the core will be the entire section. 4 The core’s x and y centroid coordinates are the design centroid’s x and y coordinates. 5 You can view the centroid of a design strip segment cross section in the first page of an audit. See Chapter 31, “Using the

Auditor” for more information.

50.8.4 Calculating the forces on the cross section RAM Concept calculates the cross section forces about the design centroid of the cross section (after trimming has been taken into account). For each of the same slab elements that make up the initial concrete cross section (before trimming has been taken into account), the elements’ nodal forces (for all the elements’ nodes on one side of the design section) are transformed to the centroid of the final concrete section and added to the design section forces. For slab elements that contain the end of the design section, only a fraction (proportional to the length of the design section in the element divided by the length across the element along a line collinear with the design section) of the nodal forces are included. Nodal forces are used in place of integrations of slab stresses because slab stress results may have local spikes caused by odd-shaped elements. These local spikes can significantly alter the total integrated value. The nodal forces used by Concept are not affected by the local stress spikes and always give results that will be in equilibrium with the nodal loads.

50.8.5 Calculating the balanced load percentages RAM Concept calculates the percentage of load that is balanced by the post-tensioning within design strips. See “Viewing balanced load percentages” on page 156 for instructions on accessing this information. Each design strip segment reports two values: RAM Concept

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Chapter 50 xx% DL Balanced xx% DL + RLL Balanced The values reported are valid for the last Calc All (tendon changes after that are not reflected). The values are calculated based on the total static moment for the span, for the balanced loadings and the dead and live loadings. For a cantilever span, the effective load is: w = 2M ⁄ L

2

where: M = moment at first cross section L = clear span For a regular span (with supports at both ends), the effective load is: w = 8M ⁄ L

2

where M = (M1 + M2)/2 - M3 M1 = moment at first cross section M2 = moment at last cross section M3 = moment at cross section closest to midway between first and last cross sections L = clear span The percentage is defined as: % = -100 Wb/Wl where Wb = effective load due to balance and transfer balance loadings Wl = effective load due to load combination under consideration (“DL” or “DL + RLL”) There is no possible calculation for design strip segments that are not part of a span. These have an “undefined” balance load percentage. The balance calculation may have some differences from the calculation available in the tendon plans. The difference are due to: • diversion of PT effects • clear span vs total span • moment taken at first and last sections, not at support centerlines In the calculations, “DL” is based on the “dead” loading types, and means: Self Weight + Dead + Dead (transfer) but does NOT include Stressing Dead

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Chapter 50 In the calculations, “RLL” is based on the new loading types, and means: Live (reducible) + Live (unreducible) + Live (storage) + Live (parking) + Live (roof) + Live (reducible)(transfer) + Live (unreducible)(transfer) + Live (storage)(transfer) + Live (roof)(transfer) All of these loadings are reduced per the live load reduction code before addition to the total.

50.8.6 Using the “Don't Reduce Integrated M and V due to Sign Change” option Design sections and span segments contain an option (checkbox) with the label “Don't reduce Integrated M and V due to Sign Change”. If this option is selected, Concept will perform five integrations of the cross section forces for every loading and load pattern: 1. Standard Integration - this is as described in “Calculating the forces on the cross section” on page 389. 2. Max Moment Integration - same as item 1, except that only elements that would increase the integrated bending moment value are considered. 3. Min Moment Integration - same as item 1, except that only elements that would decrease the integrated bending moment value are considered. 4. Max Shear Integration - same as item 1, except that only elements that would increase the integrated vertical shear value are considered. 5. Min Shear Integration - same as item 1, except that only elements that would decrease the integrated vertical shear value are considered. The intent of this option is to allow for safe, conservative designs where cross sections include regions of moment (or shear) with opposite signs that cause the moment (or shear) recorded for the cross section to be less than that for a shorter sub- cross section. The values from the above integrations may not be considered in certain circumstances: • Standard Integration - all values always considered. • Max Moment Integration - bending moment value considered if bending moment is same sign as bending moment in Standard Integration. • Min Moment Integration - bending moment value considered if bending moment is same sign as bending moment in Standard Integration. • Max Shear Integration - vertical shear value considered if vertical shear is same sign as vertical shear in Standard Integration. • Min Shear Integration - vertical shear value considered if vertical shear is same sign as vertical shear in Standard Integration. When the “Don't reduce Integrated M and V due to Sign Change” option is selected, the design forces are always more conservative than when the option is not selected. This option should not be used without due consideration.

Note: These selective integrations are performed independently for each loading. Load(ing) Combinations cross section forces therefore may include (and exclude) forces from different elements in each loading. This adds to the conservatism of the option.

50.9 Result categories in RAM Concept RAM Concept keeps track of 2 categories of results: “standard” and “envelope”.

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50.9.1 Standard results Standard results - loadings

Standard Results for a loading are the results due to the application of all loads of the loading with no patterns considered. These results consists of the results on the Slab tab, the “Standard” context results on the Reaction tab and the “Standard” context results for the Strip tab. Standard results - load combinations

Standard Results for a load combination are the linear combination of loading standard results using the standard load factors. These results consist of the results on the Slab tab, the “Standard” context results on the Reaction tab and the “Standard” context results for the Strip tab.

Note: Standard results also include all of the results for items other than design strip segments, design sections and punching checks. Items such as slab bending moments, column reactions and soil reactions are included in the standard (nonenveloped) results.

Note: For rule set layers, there are no standard results; only envelope results are calculated. 50.9.2 Envelope results Envelope results are kept for only 3 object types - design strip segments, design sections and punching checks. Envelope results fully consider pattern loadings and alternate envelope factors (as well as standard factors). For design strip segments and design sections all of the cross-section forces are calculated, and there are six envelope result sets kept: Max M (forces in place at time of maximum M) Min M (forces in place at time of minimum M) Max V (forces in place at time of maximum V) Min V (forces in place at time of minimum V) Max P (forces in place at time of maximum P) Min P (forces in place at time of minimum P)

Note: “Min” refers to the minimum “signed” value, not the minimum absolute value. For punching checks all the reaction forces are calculated and there are 6 envelope result sets kept: Max Fz (reaction forces at time of maximum Fz reaction) Min Fz (reaction forces at time of minimum Fz reaction) Max Mx (reaction forces at time of maximum Mx reaction) Min Mx (reaction forces at time of minimum Mx reaction) Max My (reaction forces at time of maximum My reaction) Min My (reaction forces at time of minimum My reaction)

50.9.3 How RAM Concept calculates envelope results Envelope Results - Loadings

Envelope results for a loading are determined by comparing the results for the full loading and the results of all of the pattern loadings (considering the pattern factors). Envelope results consist of a subset of results which occur simultaneously with minimum and maximum values of certain resultants.

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Chapter 50 For example, for a design section, all of the pattern results would be compared, and the pattern result with the largest bending moment would become the Max M result for that design section; other design sections’ Max M results might be determined by other patterns. If the loading is not patterned, then all of the envelope results are identical to the standard results. Envelope Results - Load Combinations

Envelope results for a load combination are determined by comparing all the permutations of standard and alternate load factors multiplied by all envelopes for each loading in the load combination. For each location and envelope type, the chosen load factors are those that create the most extreme envelope. In mathematical terms: • There are 2n(p+1) results for n loadings and p patterns. • These 2n(p+1) results are enveloped together. The actual calculations that RAM Concept uses do not consider 2n(p+1) load combinations, but the result of the RAM Concept’s calculations is the same as if it did. Envelope Results - Rule Sets

Envelope results for rule sets are determined by comparing all the envelopes for all of the load combinations that use the rule set. For each location and envelope type, the chosen values are those that occur simultaneously with the most extreme envelope. Envelope results for a loading, load combination or rule set are all the results on the Reaction tab and Strip tab except for those with the “Standard” context. The Standard context for these plots is sometimes referred to as the “standard envelope”, but technically it is not an envelope at all.

Note: RAM Concept’s enveloping finds the critical cases in most regular and complicated models. It would be possible, however, for the six envelopes to miss the critical case. If you believe that a set of forces not included in the envelopes may be critical for the design, you can manually create additional loadings (without patterning) and/or additional load combinations (without alternate load factors) and/or additional rule sets (using a single load combination) to ensure that the force set of concern is considered in the design.

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51 Section Design Notes This chapter explains RAM Concept’s general approach to the analysis and design of cross sections. The specific handling of each code’s requirements are detailed in the chapters that follow.

51.1 General Design Approach

51.1.1 Strip and Section Design – A 3 Step Process RAM Concept performs its design in 3 steps: Step 1: Each Rule set performs its “Phase 1” selection of reinforcement. For most rule sets this is the entire design. Step 1b: The selected reinforcement of all the rule sets is summarized. Step 2: Each Rule set performs its “Phase 2” selection of reinforcement needed in addition to that summarized in step 1b. For most rule sets nothing happens in this step, but for some rule sets –such as shear design and ductility design the summarized step 1 reinforcement needs to be known before the design can be performed. Step 2b: The selected reinforcement of all the rule sets is summarized. Step 3: Each Rule set performs a final check (no reinforcement is added in this step) and final analysis.

51.1.2 Non-prestressed Reinforcement Stress-Strain Curves RAM Concept considers mild steel reinforcement to be a perfectly elastic/plastic material as defined by the modulus of elasticity and the yield stress.

51.1.3 Post-tensioning Material Stress-Strain Curves RAM Concept uses a post-tensioning steel stress-strain curve base on a standard “power formula” that has been used in various forms for 25 years: fp = εp [A + B/{1 + (C εp)D}1/D] ≤ fpu Where A, B, C and D are coefficients chosen to best fit the experimental stress-strain curve data. RAM Concept uses coefficients A, B, C and D based on an analysis of prestressing steel stress-strain curves included a paper by Develapura and Tadros [Develapura, R. K. and Tadros, M. K.,“Critical Assessment of ACI 318 Eq. (18-3) for Prestressing Steel Stress at Ultimate Flexure”, ACI Structural Journal, V. 89, No. 5, September-October 1992, pp. 538-546]. RAM Concept’s values are: A = 0.0311 Ep B = Ep - A C = 0.958 Ep/fpy D = 7.36 These values provide exact correspondence with the recommended parameters for 270 ksi (1860 MPa) strand with fpy of 0.9 fpu. For other prestressing materials, there may be small differences (a few percent) from the theoretical curves in the region between the start of yield and ultimate strength.

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300

300

200 Fp(strain) Fpu Fpy 100

0

0

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51.1.4 Relationship of Bonded Post-tensioning Strains to Cross-Section Strains The strains in a cross section can be determined using the “plane sections remain plane” assumption. However, due to the effects of prestressing and the sequence of construction, the strains in the post-tensioning in a cross section are not equal to the strains in the adjacent concrete. Conceptually, to calculate the strain in a bonded tendon at that corresponds to the adjacent concrete strain is simple: εp = εc + (εpi – εci) Where εp = strain in tendon εc = strain in concrete adjacent to tendon εpi = strain in tendon at time of bonding εci = strain in adjacent concrete at time of bonding (typically negative) RAM Concept uses the following procedure and assumptions when calculating the εpi and εci values for each tendon in each design cross section: • All tendon “long-term losses” (relaxation, elastic shortening, creep and shrinkage) occur before bonding. • The formwork applies an upward force on the concrete exactly the same as the weight of the concrete. The only forces in the concrete are those due to the balance loading. • The concrete strains can be determined using gross section properties and the “initial” concrete modulus.

51.1.5 Unbonded Post-tensioning Stress-Strain Curves –General Theory RAM Concept’s treatment of the effect of cross section strains on ultimate unbonded tendon stresses is loosely based on a paper by Naaman, Burns, French, Gable and Mattock [Naaman, A. E. et. al, “Stresses in Unbonded Prestressing Tendons at Ultimate: Recommendation”, ACI Structural Journal, V. 99, No. 4, July-August 2002, pp. 518-529]. In the paper the authors, who are members of the Subcommittee of Stresses in Unbonded Tendons of Joint ASCE-ACI committee 423, Prestressed Concrete, recommend code modifications for ACI 318. The paper provides an equation for estimating tendon stresses at ultimate bending strength of a cross section. The proposed equation is shown to have a correlation with test results that is 2.5 times better than the ACI equations 18-4 and 18-5. The equation is:

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Chapter 51 fps = fse + Ωu Ep εcu(dp/c – 1)(L1/L2) ≤ 0.80fpu where fps = tendon stress at ultimate bending strength fse = effective prestress in prestressed reinforcement Ep = elastic modulus of prestressed reinforcement εcu = failure strain of concrete (typically assumed as 0.003) dp = distance from extreme compression fiber to centroid of prestressed reinforcement. c = depth of neutral axis at ultimate strength L = span under consideration L1 = sum of lengths of loaded spans L2 = total length of tendon between anchorages Ωu = K(dp/L) where K = 3 for uniform or third point loadings and 1.5 for midspan loading fpu = specified tensile strength of prestressed tendons It can be shown that: ∆ε p ≈ ε cu ( d p ⁄ c – 1 ) where ∆εp = change in strain in concrete adjacent to the tendon from effective prestress level to ultimate bending With this substitution (and the one for Ωu) the equation becomes: fps = fse + K(dp/L) Ep ∆εp (L1/L2) ≤ 0.80fpu L can both realistically and conservatively be assumed to equal L1 as it is unlikely for two spans to simultaneously have large inelastic deformations. This simplifies the equation further to: fps = fse + Ep (Kdp /L2) ∆εp ≤ 0.80fpu It is obvious that in the above equations that (Kdp /L2) is a strain reduction factor that accounts for the distribution of the localized strain over the length of the tendon. The numerator is a consideration of the length of the yielding (high strain) region, while the denominator is a consideration of the length over which this strain is distributed.

51.1.6 Unbonded Post-tensioning Stress-Strain Curves – Program Implementation RAM Concept assumes that unbonded post-tensioning stresses are not affected by service loading. For ultimate strength considerations, RAM Concept treats unbonded tendons as partially bonded tendons: fps = F(εpse + k ∆εp) ≤ flimit where fps = tendon stress at ultimate bending strength F() = post-tensioning material stress strain curve (described above)

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Chapter 51 εpse = strain in tendon at effective prestress level ∆εp = change in strain in concrete adjacent to the tendon from effective prestress level to ultimate bending k = strain reduction factor, taken as 0.1 flimit = limit stress as defined by the effective code For ACI 318-99, flimit is defined by equations 18-4 and 18-5. In the calculation of ρp used in the ACI equations, RAM Concept assumes the tendons are placed on the more beneficial side of the tendon centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section). For AS 3600-2001, flimit is defined by section 8.1.6. In the calculation of befdp used in the AS equations, RAM Concept assumes the tendons are placed on the more beneficial side of the tendon centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section).

51.1.7 Tendons – External Load or Internal Force? Tendons need to be considered as an external load for some purposes and as an internal force for other purposes. It is important that the tendon treatment be consistent throughout a calculation. RAM Concept always considers tendons as internal forces in strength calculations. The full force of the tendon is an internal force, while any hyperstatic effects generated by the tendons are considered as external forces. The balance loading should never be included in load combinations used for strength calculations, while the hyperstatic loading should always be included (as an external load) in strength calculations. Concept always considers the initial prestress in tendons as external forces in service calculations. Changes in the tendons stress (from effective stress levels) – if any – are considered as internal forces. For example if a bonded tendon is stressed with a final effective stress of 175 ksi (1207 N/mm2), but applying the service loadings to the structure results in a stress increase to 185 ksi (1276 N/mm2), then Concept will consider the 10 ksi (69 N/mm2)stress change as an internal force, while the 175 ksi (1207 N/mm2) initial stress is assumed to be considered in the applied loads. For this reason, the balance loading should always be included in load combinations used for service calculations, The hyperstatic loading should never be included in service calculations.

51.1.8 Tendons – inclusion of force vector on a cross section Tendons are excluded from a cross section if they cross the section at an angle of less than 15 degrees (i.e. if they are nearly parallel to the cross section).

51.1.9 Tendons – calculation of number of ducts The calculation of number of tendon ducts for Code bar spacing rules uses the following: • an integral number of ducts is calculated from the area of prestressing steel and the specified A ps / duct • the number is then modified by the vector component of the tendon This is true regardless of the angle of the tendon to the cross section, so long as the tendon is considered in the cross section (see Section 51.1.8).

51.1.10 Concrete Stress-Strain Curves RAM Concept uses a parabolic-plastic stress-strain curve for concrete based on the Portland Cement Association’s parabolic stress-strain curve [see PCA’s Notes on ACI 318-99 Building Code Requirements for Structural Concrete, Figure 6-8]. This curve is used for both strength and service cross section analyses. The curve is totally defined by two parameters: f’c = Concrete Cylinder Strength

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Chapter 51 Ec = Concrete Elastic Modulus (tangent at zero strain) A third parameter, the strain at which the concrete behavior changes from parabolic to linear, is calculated: ε0 = 2 (0.85 f’c)/ Ec For εc < 0 (tension) fc = 0 For 0 < εc < ε0 (parabolic range) fc = 0.85 f’c [2(εc/ε0) – (εc/ε0)2] For ε c ≥ ε 0

(plastic range)

fc = 0.85 f’c 4000

3000 Fc(strain) 0.85fc ⋅

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0.002

0.003

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51.1.11 Creep and Shrinkage Effects RAM Concept considers creep and shrinkage in any cross section by modifying the concrete stress strain curves to be: σ = f((ε - εcs)/kc) where: σ = stress in concrete kc = concrete creep factor (typically 3.35 = 2.35 + 1.0) ε = strain in cross section εcs = shrinkage strain f()= concrete material short-term stress-strain curve This modified concrete stress-strain curve is only used in the ECR calcs. It is never used for gross-section or cracked-section stress predictions.

Note: ACI 209 reports the value of 3.35 as an average creep value. RAM Concept files adopt this value as a default.

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51.1.12 Cracked Section Analyses RAM Concept performs cracked section analyses by iteratively solving for a cross section strain (top strain and bottom strain) that results in the cross section bending moment and axial force being equal to the applied moment and axial force. In the cracked section analyses, Concept considers concrete to have no tension strength. Since concrete obviously does have some tension strength, Concept’s assumption is equivalent to considering that the concrete has been previously cracked by some other loading condition. Concept’s assumption is conservative. This pre-cracked assumption is used to determine the cracked cross section stresses and the cracked moment of inertia. This assumption does not effect the ECR calculations as Branson’s formula does not consider the cracked moment of inertia unless the cross section stresses exceed the modulus of rupture. When a cross section with no concrete tension strains is analyzed with a cracked section analysis, Concept’s analysis methods result in a transformed section analysis. The parameters considered in a Rule Set’s cracked section analysis are • For ECR (Effective Curvature Ratio) Calcs Only - The creep coefficient as specified in the Load History / ECR tab of the Calc Options dialog. This coefficient is the value of (total strain under constant stress) / (initial strain under same stress); a typical value is 3.35 (1.0 for initial strain and 2.35 for creep strain) • For ECR Calcs Only - The shrinkage strain as specified in the Calc Options dialog. • The standard instantaneous concrete stress-strain curve as defined above. • All mild steel reinforcement (from all rule sets) in each cross section – this is the value reported by the Design Status area of steel plots, which will often be somewhat less than the value of the detailed reinforcement (number of bars and lengths). • The displacement of concrete by reinforcement is not considered. • The tendon stress strain curve for the type of rule set (see “Tendons – External Load or Internal Force?” on page 398). Cracked section analysis is not available for rule sets – such as Minimum Design – that do not inherently have a tendon stress-strain curve type associated with them.

51.1.13 Branson’s Stress Ratio The most common method for determining an effective moment of inertia in concrete members is Branson’s Formula: Ie = (Mcr/Ma)4 Ig + [1 – (Mcr/Ma)4] Icr where Ie = the effective moment of inertia Ig = the gross concrete moment of inertia Icr = the cracked concrete moment of inertia Mcr = the gross cross section cracking moment Ma = the applied moment As Branson’s formula does not consider axial forces which may be present (especially in post-tensioned structures), we have modified it to consider axial forces: Ie = (fcr/fa)4 Ig + [1 – (fcr/fa)4] Icr where fcr = the concrete flexural tensile strength fa = the cross-section tensile fiber stress (based on gross section properties)

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Chapter 51 If there is no axial force, then this formulation is identical to Branson’s formula. If there are axial forces, this formulation is a reasonable (but not theoretically identical) extrapolation of Branson’s formula. We call the value (fcr/fa)4 “Branson’s Stress Ratio”. Its value is always limited to be less than or equal to 1.0. Note that you will more commonly see Branson’s formula used with a power of 3 instead of 4. The power of 3 is appropriate when a peak moment in a span is used to determine an effective moment of inertia for the entire span. The power of 4 is appropriate for determining a local effective moment of inertia using local section forces [Branson, Dan E., “Instantaneous and Time-Dependent Deflections of Simple and Continuous Reinforced Concrete Beams”, Report #7, Part 1, Alabama Highway Research Department, Bureau of Public Roads, August 1963, pp.1-78].

51.1.14 Eurocode 2 Cracking Distribution Stress Ratio The Eurocode 2 method for determining a distribution coefficient similar to Branson’s stress ratio is given in Eurocode 2 equation 7.19: M c r 2 SR = β  ------- M - a where β = a coefficient taking account for the duration of loading = 1.0 for a short-term loading (characteristic or frequent service rule set) = 0.5 for sustained loads (quasi-permanent service rule set) Mcr = the gross cross section cracking moment Ma = the applied moment This stress ratio is only the right hand side of equation 7.19 as we use this ratio to modify the uncracked results. In Eurocode 2 this stress ratio is subtracted from unity to be applied to the cracked results. As this formula does not consider axial forces which may be present (especially in post-tensioned structures), we have modified it to consider axial forces: f cr 2 SR = β  ---- f - a where fcr = the concrete flexural tensile strength fa = the cross-section tensile fiber stress (based on gross section properties) If there is no axial force, then this formulation is identical to the eq. 7.19 formulation. If there are axial forces, this formulation is a reasonable (but not theoretically identical) extrapolation of the Eurocode formula. This value is always limited to be less than or equal to 1.0

51.1.15 Calculation of Effective Curvature Ratio RAM Concept calculates an “effective curvature ratio” at every cross section: ECR = Ce / Cg Where ECR = the effective curvature ratio Ce = the effective cross section curvature (see calc below)

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Ce is calculated by the approximate formula: Ce = (kc BSR Cg) + ((1 – BSR) Cccs) where kc = the concrete material creep factor (often 3.35) = total strain / elastic strain BSR = Branson’s Stress Ratio or Eurocode 2 Stress Ratio (see “Branson’s Stress Ratio” on page 400 or “Eurocode 2 Cracking Distribution Stress Ratio on page 349) Cccs = the cross section curvature considering cracking, creep and shrinkage (see “Cracked Section Analyses” on page 400) Note that if gross-section stresses are kept below the concrete tensile strength, then the effective curvature ratio will be equal to the concrete material creep factor (kc). If post-tensioning is considered as an internal force (not an external load) for the active design rules, then the gross-section calculations are performed with the post-tensioning primary forces added to the calculated cross section forces. It is unusual, but possible, for the ECR value to be less than the concrete material creep factor (kc). These cases occur if the amount of reinforcement is so large that the cracked stiffness (including concrete creep) is greater than the gross stiffness (including concrete creep).

51.1.16 Use of ECR ECR values are defined for curvatures of cross sections - we need to be able to transform them into a span deflection multiplier for convenient design use. The deflection of a span is proportional to the elastic energy in the span. Considering only bending energy of the gross section: ∆ g = k ∫ ( M ) ( M ⁄ EI )dl Considering the ECR as “softener” of the gross section stiffness, this equation becomes: ∆ ec r = k ∫ ( M ) ( ECR ) ( M ⁄ EI )dl From these two equations we can create a span deflection multiplier for convenient design use: Deflection Multiplier = ∆ecr / ∆g Deflection Multiplier =

k ∫ ( M ) ( ECR ) ( M ⁄ EI )dl ⁄ k ∫ ( M ) ( M ⁄ EI )dl

Deflection Multiplier =

∫ ( M ) ( ECR) ( M ⁄ EI )dl ⁄ ∫ ( M ) ( M ⁄ EI )dl

Note that this multiplier will likely be conservative for indeterminate structures as the bending moments in the structure will become rearranged (stiffer sections will attract more moment) in a manner that will reduce ∆ecr.

Note: The deflection multiplier will always be less than the maximum ECR value in the span. Note: The L.T. deflection plot uses this integral.

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51.1.17 Crack Width Predictions Unless the design code in use specifies a calculation for estimating crack widths, RAM Concept estimates crack widths based on a paper by Frosch [Frosch, R. J.,“Another Look at Cracking and Crack Control in Reinforced Concrete”, ACI Structural Journal, V. 96, No. 3, May-June 1999, pp. 437-442]. In cracked concrete, with the concrete assumed to carry only small tension stress, the crack width can be calculated as: w c = εc s c where: wc = crack width εc = cross section strain at crack elevation sc = crack spacing The cross section strain (εc) at the crack elevation can be easily calculated in a cracked-section analysis using the “plane sections remain plane” assumption. The crack spacing (sc) is more difficult to predict. For reinforcement with no bond to the concrete, the crack spacing can be shown to be: h ≤ sc ≤ 2 h where: h = height of the tension zone For reinforcement with “no-slip” with the concrete, the crack spacing can be shown to be: d * ≤ sc ≤ 2 d * where: d* = distance from crack to centroid of nearest reinforcement

=

2

2

(c + (sb ⁄ 2 ) )

for a single layer of reinforcement

where: c = perpendicular (shortest) distance from concrete face to reinforcement centroid sb = spacing of reinforcement For deformed bars without special coatings (such as epoxy), Frosch has shown that: sc = 2 d * leads to reasonable predictions of the maximum crack width. RAM Concept uses this assumption, but limits d* to a maximum value of h (the crack height); this limiting value typically only controls in slabs without bonded reinforcement. The final equation RAM Concept uses for crack width calculation can be written as: wc = 2 ε c d*

(d* ≤ h)

For multiple bars and layers of reinforcement, the reinforcement can be optimally placed such that:

d* =

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2

( c i + ( s i ⁄ 2 ) ) for all reinforcement i

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w = Σs i where: ci = perpendicular (shortest) distance from concrete face to reinforcement i centroid si = length along on concrete tension face allocated to reinforcement i w = width of concrete tension face RAM Concept iteratively solves for d* (to within 1 mm), using all bonded reinforcement that when considered minimizes the value of d*. When using bonded post-tensioning, each duct is considered as a reinforcing bar equivalent. Unbonded and external post-tensioning are ignored. Tendons at an angle of less than 45 degrees to the cross section are ignored also.

51.1.18 “Cracking Moment” Used in Design Calculations Many design codes require that cross sections have a minimum moment capacity of at least some factor (often 1.2) times the cracking load of the cross section. The cracking load is derived as follows: fcr = (ML + MB)/S – (PL + PB)/A where: fcr = the cracking stress ML = the bending moment due to applied loads at time of cracking MB = the bending moment due to the balance loading (same sign as ML) S = the section modulus for the direction of bending (Z in some communities) PL = the axial compression due to applied loads at time of cracking PB = the axial compression due to the balance loading A = the section area Solving for ML results in: ML = (fcr + (PL + PB)/A)S - MB Assuming that PL is zero: ML = (fcr + PB/A)S - MB Replacing MB with MP + MH and PB with PP + PH: ML = (fcr + (PP + PH)/A)S – (MP + MH) where: MP = the “primary” post-tensioning bending moment MH = the hyperstatic post-tensioning bending moment PP = the “primary” post-tensioning axial compression PH = the hyperstatic post-tensioning axial compression (typically negative) Multiplying by 1.2 to get “1.2 times the cracking load”: 1.2 ML = 1.2 (fcr + (PP + PH)/A) S – 1.2 (MP + MH) 404

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Chapter 51 To get the design bending moment, we add in the hyperstatic bending moment: MD = 1.2 ML + MH = 1.2 (fcr + (PP + PH)/A) S – 1.2 (MP + MH) + MH Simplifying: MD = 1.2 (fcr +(PP + PH)/A) S – 1.2 MP – 0.2 MH It is common and usually conservative to assume that PH is zero: MD = 1.2 (fcr +PP/A) S – 1.2 MP – 0.2 MH It is common (although not technically correct) to ignore the 0.2 MH, giving the final design moment equation: MD = 1.2 (fcr + PP/A) S – 1.2 M P

51.1.19 Concrete “Core” Determination • The “core” of the cross section is used in various calculations. • Refer to “About shear core” on page 105 of Chapter 22, “Defining Design Strips” for explanation of the core calculation. • Tendon ducts in this core are investigated. • Ducts are assumed to have the same heights as their widths and are assumed to be rectangular in shape. For all standard ducts, these assumptions give a conservative approximation of overlapping. • Ducts are assumed to be centered on the prestressing steel that they contain (this is not true in the real structure, but this assumption rarely has any impact on the calculation result). • Any horizontal line across the core is investigated to determine the maximum total width of duct across the shear area. Bonded duct widths and unbonded duct widths are multiplied by factors that differ for each code. For example, in BS 8110, 2/3 of bonded duct widths are considered, and full unbonded duct widths are considered. For ACI, the factors are zero, so the duct width is never excluded. • The web width is equal to the core width minus the maximum total width of duct across the shear area.

51.1.20 Torsion Considerations RAM Concept can consider torsion on a cross section in four different ways, depending upon the properties of the design strip segment or the design section. The four approaches are: The methods considered are: • Beam • Considers torsion by designing with code beam torsion equations. • As Shear • Assumes torsion is carried entirely by varying shear across the cross-section “core” length L. • The shear force per unit length is v = 6 T / L2 • The design shear force is Vd = V +/- 6 T / L • As Bending • Considers torsion by adding the torsion to the bending moment and designing bending for the combined total Md = M +/- T. • Wood-Armer • Refer to “Wood-Armer Torsion Design” on page 406. • None • Torsion is not considered in any way. RAM Concept

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51.1.21 Wood-Armer Torsion Design This new torsion design option allows the designer to use the “Wood-Armer” approach to handle twisting moments in slabs. To provide this torsion design options, a new cross section analysis quantity, Absolute Twist, is calculated. You can plot Absolute Twist, as shown in Figure 30-5 of Chapter 30, “Plotting Results”. When you choose the Wood-Armer torsion design, every set of design forces is converted into two sets of design forces, identical to the original except with the design moments changed to: Md = M + AT, and Md = M - AT where AT = absolute twist The Wood-Armer method (as originally developed by Wood and Armer) was intended to be applied at every point in the slab; Concept’s implementation is an extrapolation of the method for use in cross sections. The Wood-Armer method is NOT applicable to beams, and is not recommended for strips containing beams. References

• Wood, R. H., “The Reinforcement of Slabs in Accordance with a Pre-Determined Field of Moments,” Concrete, vol. 2, pp. 69-76, February 1968. • Armer, G. S. T., “Discussion,” Concrete, vol. 2, pp. 319-320, August 1968.

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52 Live Load Reduction Notes This chapter details RAM Concept’s implementation of live load reduction.

52.1 Live Load Reduction for Loadings, Load Combinations and Rule Sets RAM Concept individually applies live load reduction to each loading of each column, punching check, design strip segment and design section. For example, the reduction factor for a column may be different for a Live (Reducible) Loading than for a Live (Storage) Loading.

52.1.1 Loadings While RAM Concept calculates the live load reductions per loading (and per member), the reductions do not affect the loading analysis. The analysis results that Concept displays for loadings are never reduced by live load reduction.

52.1.2 Load Combinations and Rule Sets When RAM Concept combines loadings into load combinations, it considers the live load reduction of each loading added to the load combination. The analysis results that Concept displays for load combinations are always reduced by live load reduction. Similarly when Concept envelopes load combinations into Rule Sets, it considers live load reduction as all of the load combinations being enveloped have already been modified by the reduction factors. The analysis results that Concept displays for rule sets are always reduced by live load reduction.

Note: Remember that Concept only reduces live load on columns, punching checks, design strip segments and design sections.

Note: See “Viewing live load reduction results” on page 157 for more information.

52.2 Tributary Area Calculations When a loading on a structure is uniform, it is common to assign to each structural member a “tributary area” that the member (alone) supports. This assignment is typically performed by a simplistic visual analysis. The assigned area is not truly supported by only the member to which it is assigned. The effects of the (true) uniform loading on the member are similar to the effects if the entire load of the tributary area was applied to the member. Most design codes use the tributary area as the primary parameter in the live load reduction calculations. RAM Concept calculates tributary areas by applying a unit uniform load to the entire slab and analyzing the flow of the vertical forces. The tributary areas for the following members are calculated from the unit load as follows: Columns - the vertical reaction, but not less than zero. Walls - (not currently reduced). Punching Checks - the vertical reaction, but not less than zero. Design Strip Segments - the absolute value of the difference between the vertical shears at both ends. When multiple segments make up a span, the segments combined tributary areas are used in calculations. Design Sections - the absolute value of the shear. With the above calculations, it is possible (but not common) for the sum of the tributary areas of walls and columns to exceed the total floor area. This happens when one or more of the support reactions are negative. RAM Concept

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52.3 Influence Area Calculations ASCE-7 and IBC 2003 use an “influence area” instead of a tributary area in their live load reduction calculations. The influence area is defined as the “floor area over which the influence surface for structural effects is significantly different from zero”. Influence areas are not calculated when BS 6399 or AS/NZ 1170.1 are used. RAM Concept uses heuristic methods to calculate influence areas. These methods tend to define areas that are similar to those of that engineers would produce visually, but the methods do not calculate areas that are exactly the same as an engineer might calculate manually. Concept's influence areas can be shown on the plans so you can inspect the areas that Concept is using in its live load reduction calculations. Per ASCE-7 and IBC 2003, Concept limits the influence areas to be no larger than the following multiple of the tributary area: Tributary Area

Multiple

Columns

4

Punching Checks

4

Beam Design Strips

2

Slab Design Strips

1

Figure 52-1 Maximum multiple of influence area to tributary

52.3.1 Example of Influence Areas Figure 52-2 through Figure 52-6 shows RAM Concept's influence areas and the influence areas commonly used by engineers for a few slab conditions. Some engineers might (erroneously) suggest that the tributary area of the column in Figure 52-2 is 600 square feet, but continuity effects would obviously increase that value. The results show that the tributary area is actually 952 square feet.

Figure 52-2 Slab layout with dimensions in feet from center of column to centerline of walls. An engineer would typically deem the influence area to be 2400 square feet.

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Figure 52-3 Column and punching check influence areas as calculated by RAM Concept

Figure 52-4 Design strip segments

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Figure 52-5 Design strip segment influence areas as calculated by RAM Concept

Figure 52-6 Column and punching check influence areas for an irregular floor.

52.4 ASCE-7 2002 Live Load Reduction ASCE-7 live load reduction is specified in code section 4.8. Live load effects on members with influence areas of less than 400 square feet are not modified by live load reduction. ASCE-7 requires that live loads in excess of 100 psf and live loads from passenger car garages shall not be reduced, except that members supporting two or more floors may be reduced up to 20% per code sections 4.8.2 and 4.8.3. These two load types must be drawn on a “Live (storage)” loading to be considered appropriately. ASCE-7 requires that live loads of 100 psf or less in public assembly occupancies cannot be reduced per section 4.8.4. These loads must be drawn on a “Live (unreducible)” loading to be considered appropriately The tributary area of one-way slabs is not limited per section 4.8.5. However, if you limit the design strip width to 1.5 times the span length, and the behavior is that of a one-way slab, then the requirements of this code section will be met.

Note: ASCE-7 actually defines an “application factor” not a “reduction factor” (reduction factor = 1 - application factor). 410

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52.5 ASCE-7 2010 Live Load Reduction ASCE-7 live load reduction is specified in code section 4.7. Live load effects on members with influence areas of less than 400 square feet are not modified by live load reduction. ASCE-7 requires that live loads in excess of 100 psf and live loads from passenger car garages shall not be reduced, except that members supporting two or more floors may be reduced up to 20% per code sections 4.7.3 and 4.7.4. These two load types must be drawn on a “Live (storage)” loading to be considered appropriately. ASCE-7 requires that live loads of 100 psf or less in public assembly occupancies cannot be reduced per section 4.7.5. These loads must be drawn on a “Live (unreducible)” loading to be considered appropriately The tributary area of one-way slabs is not limited per section 4.7.6. However, if you limit the design strip width to 1.5 times the span length, and the behavior is that of a one-way slab, then the requirements of this code section will be met.

Note: ASCE-7 actually defines an “application factor” not a “reduction factor” (reduction factor = 1 - application factor).

52.6 IBC 2003 Live Load Reduction IBC 2003 live load reduction is specified in code section 1607.9. Live load effects on members with influence areas of less than 400 square feet are not modified by live load reduction. IBC 2003 requires that live loads in excess of 100 psf and live loads from passenger car garages shall not be reduced, except that members supporting two or more floors may be reduced up to 20% per code sections 1607.9.1.1 and 1607.9.1.2. These two load types must be drawn on a “Live (storage)” loading to be considered appropriately. IBC 2003 requires that live loads of 100 psf or less in public assembly occupancies cannot be reduced per section 1607.9.1.3. These loads must be drawn on a “Live (unreducible)” loading to be considered appropriately. The reduction of live loads for one-way slabs is not permitted per section 1607.9.1.4. RAM Concept will never reduce oneway slab loads if IBC 2003 is selected.

Note: IBC 2003 actually defines an “application factor” not a “reduction factor” (reduction factor = 1 - application factor).

52.7 IBC 2006 Live Load Reduction IBC 2006 live load reduction is specified in code section 1607.9. Live load effects on members with influence areas of less than 400 square feet are not modified by live load reduction. IBC 2006 requires that live loads in excess of 100 psf and live loads from passenger car garages shall not be reduced, except that members supporting two or more floors may be reduced up to 20% per code sections 1607.9.1.1 and 1607.9.1.2. These two load types must be drawn on a “Live (storage)” loading to be considered appropriately. IBC 2006 requires that live loads of 100 psf or less in public assembly occupancies cannot be reduced per section 1607.9.1.3. These loads must be drawn on a “Live (unreducible)” loading to be considered appropriately. The reduction of live loads for one-way slabs is not permitted per section 1607.9.1.4. RAM Concept will never reduce oneway slab loads if IBC 2006 is selected.


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52.8 IBC 2009 Live Load Reduction IBC 2009 live load reduction is specified in code section 1607.9. Live load effects on members with influence areas of less than 400 square feet are not modified by live load reduction. IBC 2009 requires that live loads in excess of 100 psf and live loads from passenger car garages shall not be reduced, except that members supporting two or more floors may be reduced up to 20% per code sections 1607.9.1.2 and 1607.9.1.3. These two load types must be drawn on a “Live (storage)” loading to be considered appropriately. IBC 2009 requires that live loads of 100 psf and at areas where fixed seats are located in Group A occupancies cannot be reduced per section 1607.9.1.4. These loads must be drawn on a “Live (unreducible)” loading to be considered appropriately. The tributary area of one-way slabs is limited by section 1607.9.1.1.


52.9 UBC 1997 Live Load Reduction UBC 1997 live load reduction is specified in code section 1607.5. Live load effects on members with tributary areas of 150 square feet or less are not modified by live load reduction. Equation (7-2) [R = 23.1 (1 + D/L)] is not considered in live load reduction calculations. This value needs to be calculated and set by the user in the maximum reduction property. UBC 1997 requires that storage loads in excess of 100 psf shall not be reduced, except that live loads on columns may be reduced up to 20%. These loads must be drawn on a Live (Storage) loading to be considered appropriately. UBC 1997 requires that other live loads in excess of 100 psf or in places of public assembly occupancies cannot be reduced. These loads must be drawn on a Live (Unreducible) loading to be considered appropriately. UBC 1997 can be used as IBC 2003 alternate live load reduction in accordance with IBC section 1607.9.2. Because minimum parking loads in UBC 1997 are higher than IBC 2003 minimum parking loads, it may not be appropriate to apply UBC 1997 parking garage reduction provisions to IBC 2003 loadings. For this reason, parking garage loads should be drawn on a Live (Storage) loading and thus will get a maximum 20% reduction on columns and no live load reduction on other members.

52.10 AS/NZS 1170.1-2002 Live Load Reduction AS/NZS 1170.1 live load reduction is specified in code section 3.4.2. When using AS/NZS 1170.1 to perform live load reduction, only live loadings with the “Live (Reducible)” type are reduced. Live (Storage) loadings are assumed to have loads greater than 5 kPa and are therefore not reducible per 3.4.2(ii). Loading effects on one-way slabs are not reduced per 3.4.2(v). For other member types, the reduction is calculated per the formula in 3.4.2(b).

Note: Section 3.4.2 actually defines an “application factor” not a “reduction factor” (reduction factor = 1 - application factor).

52.11 BS 6399-1:1996 Live Load Reduction BS 6399 live load reduction is specified in code sections 6.1 through 6.3.

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Chapter 52 Only live loadings with the “Live (Reducible)” type are reduced. For columns, the Table 2 and Table 3 values from the code are calculated and the greater of the two reductions is used. For other members, the Table 3 values are used. For columns, the moment and shear values are reduced by the same reduction factor as the axial force values; this is different from what is specified in the note in Section 6.2 of BS 6399. This does not affect any design in RAM Concept (or the RAM Structural System), but it does affect the reported column reaction values. Live load reduction is not used for one-way and two-ways slabs.

52.12 IS 875 (Part 2) - 1987 Live Load Reduction IS 875 live load reduction is specified in code section 3.2. For columns, only live loadings with the “Live (Reducible)” type are reduced. For beams, both “Live (Reducible)” and “Live (Storage)” loadings are reduced. For columns, the table in section 3.2.1 is implemented. The 5 kN/m2 provisions in section 3.2.1.1 are not implemented. For columns, the moment and shear values are reduced by the same reduction factor as the axial force values. For beams, the reductions in section 3.2.2 are implemented. The limitations of subsections “a” through “d” are not implemented as all loads on a “Live (Reducible)” or “Live (Storage)” loading layer are assumed to be reducible. Live load reduction is not used for one-way slabs, two-way slabs and punching checks.

52.13 Eurocode 1-2002 (UK Annex) Live Load Reduction Eurocode 1 live load reduction is specified in code clause 6.3.1.2(10-11) and UK NA 2.5-2.6. Only live loadings with the “Live (Reducible)” type are reduced. For columns, equation NA.1 and NA.2 values from the UK National Annex are calculated and the greater of the two reductions is used. For other members, equation NA.1 values are used.

Note: Eurocode 1 actually defines an “application factor” not a “reduction factor” (reduction factor = 1 - application factor).

52.14 National Building Code of Canada 2005 Live Load Reduction NBC 2005 live load reduction is specified in code clause 4.1.5.9. Only live loadings with the “Live (Reducible)” , “Live (Storage)”, and Live (Parking) types are reduced. Live (Reducible) loads are reduced in accordance with 4.1.5.9 2), and Live (Storage) and Live (Parking) types are reduced in accordance with 4.1.5.9 3).

52.15 Mat Foundations In the design of mat foundations supporting columns (and/or walls) supporting levels above, the live load reductions need to be applied to the loads instead of the member forces. The loads need to be reduced instead of the member forces for two

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Chapter 52 reasons: 1) there is a clear understanding of the tributary area for the loads while (in most cases) there is not a clear understanding of the tributary area for the design strips; and 2) the zero-tension soil reaction iterations need to be performed with the reduced loads. For mat foundations, the live load reduction code should always be set to “None”. Otherwise the live loads may be reduced twice. Mat foundation loads that are imported from the RAM Structural System will be automatically reduced appropriately (by the RAM Structural System). User-drawn loads will need to be reduced manually.

52.16 Special Member Considerations

52.16.1 Columns Above the Slab Columns above the slab will have zero tributary area and zero influence area assigned to them in the automated area calculations. If you want to have live load reduction applied to columns above the slab you will need to manually specify the areas to use.

52.16.2 Columns Above and Below the Slab When the reactions for columns above and below the slab are reported together, the live load reduction for the column below the slab is used. Because of this, the separate reported reactions for the column below and the column above will not necessarily sum to the reported reaction for the column above and below.

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53 Reinforcement Notes This chapter provides information on how RAM Concept utilizes span detailing, calculates reinforcement development lengths and lays out and details reinforcement.

contraflexure, assumed to be 20% of a continuous span's length (hence the factor of 5 applied to Lc). Span Detailing is controlled via the span segment dialog. See Section 22.5 of Chapter 22, “Defining Design Strips”.

53.1 Span detailing “Span Detailing” is the process of determining the peak reinforcement requirements in a region (normally support or mid-span) and then extending the reinforcement based upon code or user defined rules. Code based span detailing are rules prescribed by the applicable building code. The detailed reinforcement for these spans can be non-symmetrical depending upon whether or not the span is continuous. The Code span detailing option uses the applicable code rules for continuous and end spans (as well as cantilevers), where applicable. Concept's Code span detailing generally implements some, but not all, of the specified detailing rules for a code. Refer to the code span detailing sections for further information (Sections 53.1.3, 53.1.4, 53.1.6 and 53.1.7 on page 416). User defined span detailing rules are controlled via the following screen accessed via Criteria > Detailing Rules.

Figure 53-2 Span segment dialog box

53.1.1 About Concept’s detailing calculations Two sets of design results are calculated in Concept - With span detailing and Without span detailing. Without span detailing simply considers the results without extending any reinforcement for span detailing. This is termed the raw reinforcement. Figure 53-1 Span Detailing Parameters (Criteria > Detailing Rules)

A, B, and C represent different sets of reinforcement used to detail rebar in the support region. E, F, and G represent different sets of reinforcement used to detail rebar in the span region. Each set of reinforcement has an associated “fraction” which is the amount of the peak reinforcement quantity to assign to that set. The sum of the three fractions should always be between 0 and 1. The R1, R2 values represent factors to be multiplied by the span length to arrive at a set's desired bar lengths. Span detailing in accordance with user rules is always symmetrical in a span (but not in a cantilever). The “R1” value is applied to the cantilever such that the cantilever is assumed to be that portion of a full span up to the point of

RAM Concept

With Span Detailing considers the results considering the detailed reinforcement as a minimum requirement. Some other modifications to the “span detailed” summary diagram are done. The developed requirements are removed from inside the support regions (there is still the requirement that the reinforcement is developed at the face of the support). Also, for cantilevers, the span detailed requirements are removed from the last cross section to the end of the span. Also, in the summary reinforcement, at the end of each pass an assumed amount of developed reinforcement is calculated from the AsRaw requirements and the length available for development, and applied as a minimum AsDev requirement in each cross section.

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53.1.2 Span detailing assumptions The following general assumptions are made when performing span detailing: • The peak reinforcement in each region is determined by taking the maximum reinforcement demand in every cross section over the following regions: • Support - from support to 0.15L into the span • Span - from 0.35L to 0.65L • For a cantilever, the entire span is considered to be in the support region, and none of the span is considered to be in the span region • For a span with no supports defined, the entire span is considered to be in the span region, and none of the span is considered to be in the support region • Bar length calculations either consider the span length to center of support, or the clear span length depending upon the code rules (see specific code sections for more details: sections 53.1.3, 53.1.4, 53.1.6 and 53.1.7). • Bar length calculations consider the support width as necessary (see specific code section for more details) • At the supports, the lengths of the adjacent span's bar sets are considered in order to keep the detailed bars centered on the supports as much as possible. If an adjacent span has different fractions than the one being detailed, the bar length for this span is determined by selecting the longer of the following length fractions: • the span length and length fraction corresponding to this bar set • the span length and length fraction of any adjacent span bar set whose fraction overlaps this bar set's fraction The span detailing is performed in pass 0 before the main design steps begin. The following outlines the pass 0 process: 1 Any user defined reinforcement is removed from the

cross sections in the span. 2 A normal pass 1 is designed on the span (with the user

The pass 0 summarized span detailed design requirements are used as the starting point for the pass 2 span detailed design.

53.1.3 ACI 318-99, 318-02, 318-05, 318-08, 318-11 Code Span Detailing Rules RC Beams and One-Way Slabs Rule 12.12.3 is implemented in support regions. For this provision, the inflection point is assumed to be 30% of the clear span from the face of support. ACI 12.11.1 is implemented in span regions. RC Two-Way Slabs Figure 13.3.8 (without drop panels) is implemented in support and span regions. PT Beams, One-Way Slabs, and Two-Way Slabs Rule 18.9.4.2 is implemented in support regions. Rule 18.9.4.1 is implemented in span regions.

53.1.4 AS 3600 - 2001 Code Span Detailing Rules RC and PT Beams Rule 8.1.8.6 (a) and (b) is implemented in support and span regions. RC and PT One-Way Slabs Figure 9.1.3.2 is implemented in support and span regions. RC and PT Two-Way Slabs Figure 9.1.3.4 is implemented in support and span regions.

53.1.5 AS 3600 - 2009 Code Span Detailing Rules RC and PT Beams Rule 8.1.10.6 (a) and (b) is implemented in support and span regions. RC and PT One-Way Slabs Figure 9.1.3.2 is implemented in support and span regions. RC and PT Two-Way Slabs Figure 9.1.3.4 is implemented in support and span regions.

defined reinforcement removed). 3 From the resulting design, the peak reinforcement in each

region (support and span) is detailed according to the user specified or code span detailing rules. 4 The user defined reinforcement is subtracted from the

step 3 requirements, which results in the final pass 0 “span detailed” requirements. The resulting pass 0 design can be approximate if the subtracted user defined reinforcement does not have the same properties as the program designed reinforcement at that location. The final designed reinforcement for each cross section, which will be determined in future passes, will always be accurate.

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53.1.6 BS 8110 - 1997 Code Span Detailing Rules RC Beams and Slabs, PT Beams and One-Way Slabs Figures 3.24 and 3.25 are implemented in support and span regions. PT Two-Way Slabs TR-43 rule 6.10.6 is implemented in support and span regions.

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Chapter 53

53.1.7 IS 456 - 2000 Code Span Detailing Rules RC and PT Beams and One-Way Slabs Rule 26.2.3.4 is implemented in support regions. For this provision, the inflection point is assumed to be 30% of the clear span from the face of support. Rule 26.2.3.3 is implemented in span regions. RC and PT Two-Way Slabs Figure 16 (without drop panel) is implemented in support and span regions.

53.1.8 EC2 Code Span Detailing Rules RC Beams and Slabs, PT Beams and One-Way Slabs Figures 8 and 10 from Chapter 10 of The Concrete Centre publication “How to Design Concrete Structures using Eurocode 2” are implemented in support and span regions. PT Two-Way Slabs TR-43 rule 5.8.8 is implemented in support and span regions.

53.2 Development lengths / anchorage

• For AS 3600, the desired extension length, D, is used to satisfy provision 8.1.8.1 (2001) or 8.1.10.1 (2009) requiring use of a shifted moment diagram for design. While this implementation is not in strict compliance with the Code provisions near the ends of a member, it meets the design intent away from the ends. • For a user defined bar, the effective development for any point along the bar is calculated in accordance with the following diagram. This approach is not used for AS 3600 - see section 53.2.2 on page page 418 for more details. • The end of any user defined bar that is close to a slab edge such that it could not be extended will use a desired extension length of zero. • For any length less than the additional extension length, the effective development is zero. • For any length greater than or equal to the desired additional extension length, but less than the full development length, the effective percentage development is (provided length)/(full development length) x 100%. This is accomplished by considering a fraction of each bar developed. • For any length greater than the full development length, the effective development is 100%.

Note: The term development length is used in this chapter. In some countries, the term anchorage is used rather than development length. This section presents an overview of the development length calculations performed in RAM Concept. Development length calculations in Concept can be treated as per Code Rules, or development lengths can be specified by the user for a particular reinforcing bar as a multiple of the bar diameter. The general implementation used for calculating development lengths is: • The clear spacing of the bars will be detailed to be greater than twice the minimum cover. This is the responsibility of the user, and is not checked by Concept.

Figure 53-3 Effective development at any point along a bar. (This does not apply to AS3600 - see Figure 53-4)

• When laying out program-designed bars, Concept uses the first option in the following list that fits in the slab: • Straight bar end with full development length and full extension length.

• Each Code has a desired extension length beyond the theoretical cutoff point of the reinforcement.

• Straight bar end with full development length and partial (or no) extension length.

• The desired extension length for ACI 318, BS 8110, and IS 456 is the maximum of d (effective depth) or 12 times the diameter of the bar. This is required primarily because diagonal tension cracks in a flexural member without transverse shear reinforcement may shift the location of the calculated tensile stress in a bar approximately d (effective depth) towards a point of zero moment. Refer to ACI 318 12.10.3, BS 8110 3.12.9.1, and IS 456 26.2.3.1.

• 90 degree hook bar end with 90 degree hook development length

RAM Concept

• 180 degree hook bar end with 180 degree hook development length • Anchored bar end with no development length • If the end of a bar is closer to a slab edge than the specified end cover, the bar will automatically be labeled “anchored” in Concept and considered to be fully developed.

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Chapter 53 • Development lengths of bars in compression are not considered. Tension development lengths are used in all locations where development of reinforcement is required, regardless of the actual stresses on the reinforcing bar.

• Lightweight aggregate concrete factor:(12.5.3.5) • 1.3 for concrete density < 120 pcf • 1.0 for concrete density > 120 pcf • Epoxy-coated reinforcement factor = 1.2(12.5.3.6) • The following factors / provisions are not used:

53.2.1 ACI 318-99, 318-02, 318-05, 318-08, 318-11 Development Lengths Basic straight tension development length is calculated using equation 12-1. The following factors are used in this equation: α = reinforcement location factor • “concrete below” is taken as the depth from the rebar center to the bottom of the concrete section • 1.3 for concrete below > 12 inches • 1.0 for concrete below < 12 inches β = coating factor • 1.5 for epoxy coated bars with cover (to center of bar) less than 3db (spacing is not calculated) • 1.2 for all other epoxy coated bars • 1.0 for uncoated bars

Note: the product αβ is never taken as greater than 1.7. γ = reinforcement size factor • 0.8 for #6 and smaller bars • 1.0 for #7 and larger bars λ = lightweight aggregate concrete factor • 1.3 for concrete density < 120 pcf • 1.0 for concrete density > 120 pcf c = cover dimension, vertical distance from the center of the bar to the nearest concrete surface (spacing is not considered) The term (c + Ktr)/db is never taken greater than 2.5 Ktr = conservatively assumed to be zero For development of standard hooks, basic tension development length is calculated in accordance with the following equation:

• Concrete cover (12.5.3.2) and Ties or stirrups (12.5.3.3) In accordance with ACI 318 12.10.3, the extension length used for this Code is the maximum of 12 db or the effective depth of the member, taken as the maximum vertical distance from the center of the reinforcing bar to the farthest concrete surface.

53.2.2 AS 3600 Development Lengths • For a user defined bar, the effective development for any point along the bar is calculated in accordance with Figure 53-4. • The end of any user defined bar that is close to a slab edge such that it could not be extended will use a desired extension length of zero. For other situations, the desired extension length is D, the overall depth of the member • For any length less than the desired extension length D, the effective development is zero. • For any length greater than or equal to the additional extension length, but less than the full development length, the effective percentage development is (provided length - desired extension length) / (full development length) x 100%. This is accomplished by considering a fraction of each bar developed. • For a program designed bar, when the bar is detailed the bar will be extended the full development length plus the desired extension length. If a bar is unable to be extended this full desired length, Concept will attempt to extend the bar just the straight development length, then the 90 degree hook development length, and the 180 degree hook development length. If there is not enough extension space to satisfy any of these conditions, an “anchor” will be placed at the end of the bar and it will be considered fully developed from that point.

1200d b -----------------fc The following factors are used to modify this basic length: • Bar yield strength factor = fy / 60 where fy is in ksi (12.5.3.1) 418

Figure 53-4 Effective development at any point along a bar for the undisplaced moment diagram (for AS3600 ONLY)

RAM Concept

Chapter 53 AS 3600-2001

AS 3600-2009

Basic straight tension development length is calculated using equation 13.1.2.1(a). The following factors are used in this equation:

Basic straight tension development length is calculated using equation 13.1.2.2. The following factors are used in this equation:

k1 = reinforcement location factor

k1 = reinforcement location factor

• “concrete below” is taken as the depth from the bar center to the bottom of the concrete section

• “concrete below” is taken as the depth from the bar center to the bottom of the concrete section

• 1.25 for concrete below > 300 mm

• 1.3 for concrete below > 300 mm

• 1.0 for concrete below < 300 mm

• 1.0 for concrete below < 300 mm

• k2 = 2.4 (conservatively)

• k2 = (132 - db)/100

• fsy = yield stress of bar

• fsy = yield stress of bar

• Ab = cross sectional area of reinforcing bar

• cd = assumed to be the vertical clear cover, implying that the minimum bar clear spacing is greater than or equal to twice the clear cover

• 2a + db = twice the vertical distance from the nearest concrete surface to the center of the bar In addition, the following factors (from ACI 318) are applied:

In addition, the following factors are applied: • coating factor • 1.5 for epoxy coated bars

• coating factor • 1.5 for epoxy coated bars with cover (to center of bar) less than 3db (spacing is not calculated)

• 1.0 for uncoated bars • lightweight aggregate concrete factor:

• 1.2 for all other epoxy coated bars

• 1.3 for concrete density < 2100 kg/m3

• 1.0 for uncoated bars

• 1.0 for concrete density > 2100 kg/m3

• lightweight aggregate concrete factor: • 1.3 for concrete density < 1900 kg/m3 • 1.0 for concrete density > 1900 kg/m3 For development of standard hooks, basic tension development length is calculated as half the straight tension development length in accordance with Clause 13.1.2.4. In accordance with 8.1.8.1, the extension length used for this Code is the overall depth of the section. This extension is applied in addition to the required development length. Concept applies the extension length to satisfy the Code provision requiring the displacement of the bending moment envelopes by a distance D. There are some noteworthy differences between Concept's approach and the Code provision:

For development of standard hooks, basic tension development length is calculated as half the straight tension development length in accordance with Clause 13.1.2.6. In accordance with 8.1.10.1, the extension length used for this Code is the overall depth of the section. This extension is applied in addition to the required development length.

53.2.3 BS 8110-1997 Development Lengths Basic straight tension development length is calculated using combined equations 48 and 49. fy ⋅ d b The resulting equation is: l d = ------------------------------------γm ⋅ 4 ⋅ β ⋅ fc u

• In most circumstances, extending the bar by a distance D beyond the required development length will satisfy the intent of the Code.

where:

• Near the ends of members, where the displaced moment diagram would cause an increased design moment, Concept will design for the unmodified moment diagram, but will still ensure proper development is satisfied.

db = diameter of the bar

RAM Concept

fy = yield stress of the bar

γ m = material strength reduction factor

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Chapter 53 β = 0.5 (assumed Type 2 bars with minimum links in beams)

Note: If any bars other than Type 2 deformed bar are used or if minimum links in accordance with Table 3.7 are not provided, the development lengths will need to be specified manually. Table 3.27 can assist with this.

For high strength deformed bars, the bond stress can be increased by 60 percent. This increase is assumed for any bar with fy > 250 N/mm2. In addition, the following factors (from ACI 318) are applied: • coating factor

In addition, the following factors (from ACI 318) are applied:

• 1.5 for epoxy coated bars with cover (to center of bar) less than 3db (spacing is not calculated)

• coating factor • 1.5 for epoxy coated bars with cover (to center of bar) less than 3db (spacing is not calculated) • 1.2 for all other epoxy coated bars

• 1.2 for all other epoxy coated bars • 1.0 for uncoated bars • lightweight aggregate concrete factor: • 1.3 for concrete density < 1900 kg/m3

• 1.0 for uncoated bars

• 1.0 for concrete density > 1900 kg/m3

• lightweight aggregate concrete factor: • 1.3 for concrete density < 1900 kg/m3 • 1.0 for concrete density > 1900 kg/m3 For development of hooks, the internal bend radius is assumed to be 2db for bar diameters less than or equal to 18mm and 3.5db for bar diameters greater than 18mm. For 90 degree hooks, the effective anchorage of the hook is 4 times the internal bend radius but not to exceed 12db in accordance with 3.12.8.23 (b) For 180 degree hooks, the effective anchorage of the hook is 8 times the internal bend radius but not to exceed 24db in accordance with 3.12.8.23 (a) In accordance with 3.12.9.1, the extension length used for this Code is the maximum of 12 db or the effective depth of the member, taken as the maximum vertical distance from the center of the reinforcing bar to the farthest concrete surface.

53.2.4 IS 456-2000 Development Lengths Basic straight tension development length is calculated using clause 26.2.1: fy ⋅ φ l d = --------------4 ⋅ τ bd

For development of hooks, the internal bend radius is assumed to be 2db for bars with yield stress less than or equal to 250 N/mm2 and 4db for bars with yield stress greater than 250 N/mm2. For 90 degree hooks, the effective anchorage of the hook is 8 times the diameter of the bar in accordance with 26.2.2.1 (1). For 180 degree hooks, the effective anchorage of the hook is 16 times the diameter of the bar in accordance with 26.2.2.1 (2). In accordance with 3.12.9.1, the extension length used for this Code is the maximum of 12 db or the effective depth of the member, taken as the maximum vertical distance from the center of the reinforcing bar to the farthest concrete surface.

53.2.5 EC2 Development Lengths Basic anchorage length is calculated using clause 8.4.3: σ sd ⋅ φ l b, rqd = ---------------4 ⋅ f bd where:

where:

f yk σ sd = design yield stress of the bar = -----γm

fy = yield stress of the bar

φ = diameter of the bar

φ = diameter of the bar

f b d = ultimate bond stress given by equation 8.2

τ bd = design bond stress given in Table 26.2.1.1

The design anchorage length is calculated in accordance with 8.4.4:

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l bd = α 1 α 2 α 3 α 4 α 5 l b, rqd ≥ l b, min

Concept considers all of the spans' and all of the design sections' designs when laying out program reinforcement. Concept's layout algorithm uses 5 steps as follows:

where:

Step 1 Divide reinforcement requirements into groups.

α1 = bar shape factor from Table 8.1 α2 = concrete factor from Table 8.1 α3 = 1.0 (tranverse reinforcement not considered)

Concept divides all the span and section reinforcement requirements into similar groups by considering the following characteristics: • Span Direction - latitude or longitude • Slab Face - top or bottom

α4 = 1.0 (transverse reinforcement not considered)

• Reinforcement Elevation - the absolute elevation of the reinforcement

α5 = 1.0 (transverse pressure not considered)

• Reinforcement Orientation - the plan view orientation of the reinforcement (always perpendicular to the cross sections)

l b, m in ≥ max { 0.3l b, rqd, 10φ, 100mm } For beams, the minimum cover cd is assumed to be 25 mm. As such, the minimum clear spacing between bars should be detailed as 50 mm. For slabs, the minimum cover cd for straight bars is calculated as the minimum vertical clear cover to the nearest concrete surface. For bent bars the cover cd is calculated as 5 times the bar diameter. The minimum clear spacing between bent bars should thus be detailed as 10 times the bar diameter. Anchorage length for bent bars is determined using Figure 8.1(a) and using the minimum bend diameters from Table 8.1N(a) A concrete density factor calculated in accordance with equation 11.1 is applied to the calculation of fbd in equation 8.2. In addition, the following factor (from ACI 318) are applied: • coating factor • 1.5 for epoxy coated bars with cover (to center of bar) less than 3db (spacing is not calculated) • 1.2 for all other epoxy coated bars • 1.0 for uncoated bars

Requirements with all similar characteristics are grouped together for further processing. Step 2 Find regions of overlapping and nearby requirement For each requirement group, Concept then finds requirements in a region that may be able to be satisfied by the same reinforcement callout. Step 3 Create preliminary callouts for each region For each region's requirements, Concept creates an optimal set of reinforcement callouts considering the cost factors specified in the General tab of the Calc Options dialog. These preliminary callouts do not consider development lengths. Step 4 Consider development lengths For each preliminary callout, Concept investigates all of the related cross sections and determines (considering the area of developed reinforcement and the total area of reinforcement required at each cross section) the necessary extension of the bar beyond the related cross sections. If the required bar extension cannot be provided (due to a slab edge or bar end cover requirements), reduced extensions using 90-degree or 180-degree hooks are investigated. If the hooks will not provide the adequate development, “anchors” will be placed at the end of the bar.

Note: Any bar that is required to extend to within the end 53.3 How RAM Concept lays out program reinforcement

cover distance of a slab edge will be given an “anchor” end condition. Step 5 Convert to concentrated program reinforcement

Note: This section describes Concept's layout of longitudinal program reinforcement. Neither transverse reinforcement nor SSR are considered here.

RAM Concept

As a final step, Concept converts the bar callouts (including development lengths and bar end conditions) into concentrated program reinforcement.

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Chapter 53 See also “Reinforcement layout and detailing parameters” on page 151 of Chapter 28, “Calculating Results”.

53.4 How Concept details user and program reinforcement Concept generates individual bars from concentrated and distributed user reinforcement. This facilitates the consideration of the individual bars in its cross section and span design calculations. Also, the generation of individual bars allows Concept to display program or user reinforcement in perspective drawings. The bars are still tagged as “user” since they are generated directly from user reinforcement. Concept also generates individual bars from its concentrated design reinforcement. These program individual bars are for display purposes only and are not used in calculations. The concentrated and distributed reinforcement is detailed into individual bars in 5 steps as follows: Step 1 Create a preliminary layout of bars Using the shape of the reinforcement region (rectangle or parallelogram for concentrated, and polygon for distributed), the reinforcement orientation and the spacing/quantity of bars, Concept determines a preliminary layout of parallel bar locations. For Concentrated bars, the first and last bars from the edge are always inset by a half bar spacing distance. Step 2 Determine the elevation of the bars

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Each concentrated or distributed reinforcement callout has an elevation reference point. For Concentrated reinforcement, the elevation reference point is the location where the (symbolic) bar and the extent arrow intersect. For distributed reinforcement, the elevation reference point is shown as a circle in the center of the (symbolic) bar. The elevation of the surface and soffit of the slab are determined at the elevation reference point and this information along with the reinforcement elevation reference (absolute, above surface, above soffit, top cover or bottom cover) and elevation values determines the absolute elevation of the bars that the callout creates. See Figures 53-5 and 53-6. Step 3 Determine the slab shape at the bar elevation For each bar elevation, Concept determines the shape of the slab. This shape may be one contiguous shape or it may be comprised of multiple separate shapes. Step 4 Trim the preliminary layout of bars with the elevation slab shape The preliminary layout of bars is trimmed by the slab shape determined in step 3. Additionally, the required end cover (as defined in the General tab of the Calc Options dialog) may shorten a bar further. This trimming may convert a single bar into multiple bars, or may eliminate a bar altogether. Note that bars with “anchor” ends do not consider the required end cover. They are only trimmed by the slab shape at the bar elevation. Step 5 Convert the trimmed bar locations to individual bars Lastly, Concept converts the trimmed preliminary layout of bars into individual bars. This conversion sets the individual bars generated from “user” reinforcement to be

RAM Concept

Chapter 53 “user” bars and those generated by “program” reinforcement to be “program” bars.

Note: The detailing of user reinforcement takes place before the design calculations and the detailing of program reinforcement takes place after the design calculations.

At locations of complicated geometry (such as multiple beams in a single span design, or curved beams), Concept may not be able to create an appropriate representation of the reinforcement required by the design calculations. The correct design quantities can always be viewed in the Section Design plots of the Design Status layer.

Note: Reinforcement required for torsion should always have 2 legs selected in the design spans. Otherwise Concept's design will show a correct overall quantity of reinforcement, but will not show a correct selection of closed and open ties.

Note: Transverse reinforcement required by design sections is NOT shown on the Reinforcement layer. This is another reason why design spans are preferable to design sections.

Figure 53-5 Stepped one-way slab with two reinforcement objects identical except for the respective location of the elevation reference point.

53.6 Example 1: reinforcement results The introduction of the reinforcement layer and reinforcement detailing makes Concept much more powerful and complicated. The following example shows the effect, for a two span slab supported by walls, of: • using the span detailer set to code in design strips, and • different plot options • using Reinforcement Layout and Detailing Parameters in the General tab of the Calc Options tab • two different rule sets: strength and code minimum

53.6.1 Strength (only) calculations This section shows results where only the strength rule set is considered. Design Status layer

Figure 53-6 Reinforcement bars detailed by Concept from Figure 53-5

The following figure shows the effect of code detailing on the reinforcement for the design status layer.

53.5 How Concept treats transverse reinforcement and individual transverse bars Concept generates transverse reinforcement and individual transverse bars from the results of its shear and torsion calculations. This generated reinforcement is for display purposes only - it is not used in calculations and cannot be changed to “user” reinforcement. RAM Concept

Figure 53-7 Design Status: Reinforcement Plan

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Chapter 53 Note that with code detailing: • the top bars are longer • some bottom bars are continuous

Note: The “no detailing” example is very similar to results obtained with version 2.1.

Reinforcement layer

The following figure shows the effect of code detailing on the reinforcement on the reinforcement layer. Figure 53-9 Reinforcement: Standard Plan with the Bar Length Cost parameter set to 3.

Design Status layer with plot: Bottom without span detailing:

For this plot, the design strips' span detailer setting of code has no effect.

Figure 53-8 Reinforcement: Standard Plan

Note that: • these program bars are rationalized such that the number of top bars is consistent either side of a support • these program bars could be changed to User bars • individual bars can be shown via the visible objects • Concept details the top bars at the right hand support with a 90 degree bend

Figure 53-10 Plot on Design Status layer: Bottom [without span detailing]

Note: See Section 30.6 of Chapter 30, “Plotting Results” for more information about reinforcement plotting.

Effect of Reinforcement Layout and Detailing Parameters

The Reinforcement Layout and Detailing Parameters affect the reinforcement bar layout, Figure 53-9 exhibits different reinforcement results from Figure 53-8 when changes are made to one parameter (in this case, the Bar Length Cost parameter is 3 rather than 1). See “Reinforcement layout and detailing parameters” on page 151 of Chapter 28, “Calculating Results”.

Design Status layer with plot: Bottom with span detailing:

The span detailing plot uses “skyline” plotting.

Figure 53-11 Plot on Design Status layer: Bottom [with span detailing]

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Chapter 53 Note that the design strips' span detailer setting of code produces more reinforcement.

Note that the minimum designer has increased the bottom bars in the left hand span for the no detailing case. See Figure 53-8. Design Status layer with plot: Bottom without span detailing:

Design Status layer with plot: Bottom (Developed) with span detailing:

This plot is exactly the same as “Bottom without span detailing” (that is, the Raw reinforcement) because this example uses just the Strength Rule Set and all such reinforcement must be developed.

For this plot, the design strips' span detailer setting of code has no effect.

Figure 53-14 Plot on Design Status layer: Bottom [WITHOUT span detailing]

Figure 53-12 Plot on Design Status layer: Bottom (Developed) WITH Span Detailing

Design Status layer with plot: Bottom with span detailing:

The span detailing plot uses “skyline” plotting.

53.6.2 Code Minimum and Strength calculations This section shows results where both the Code Minimum and Strength rule sets are considered. Reinforcement layer

The following figure shows the reinforcement for minimum and strength. Figure 53-15 Plot on Design Status layer: Bottom [WITH span detailing]

Note that the design strips' span detailer setting of code produces more reinforcement.

Figure 53-13 Reinforcement: Standard Plan

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Chapter 53 Design Status layer with plot: Bottom (Developed) without span detailing:

This plot is different from “Bottom without span detailing” (that is, the Raw reinforcement) because the Minimum reinforcement is not required to be developed.

reinforcement at the end supports is not developed, and so the plotted value is zero. Additionally, portions of the raw reinforcement are now assumed to be developed because the span detailing process for the design status layer considers that continuous bars, whether they are required to be developed or not, become at least partially developed.

Figure 53-16 Plot on Design Status layer: Bottom (Developed) WITHOUT span detailing Design Status layer with plot: Bottom (Developed) with span detailing:

Figure 53-17 Plot on Design Status layer: Bottom (Developed) WITH span detailing

This plot is different from “Bottom with span detailing” (that is, the Raw reinforcement) because the Minimum

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54 ACI 318-99 Design This chapter details RAM Concept’s implementation of ACI 318-99. The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules

54.1 ACI 318-99 default loadings This section provides information on the loadings that RAM Concept creates by default when you start a new ACI 318-99 file. As the purpose and use of most of the loadings are self-explanatory, only items that are particularly noteworthy are discussed here.

54.1.1 Temporary Construction (At Stressing) Loading This loading type describes a temporary loading that is present during construction when the contractor stresses the tendons. As it is a temporary load, it is generally only included in the Initial Service Load Combination. If a permanent load is present at stressing, you should define the load on the Temporary Construction (At Stressing) loading layer as well as the appropriate permanent loading layer. Alternatively, you can include a permanent loading present at stressing with appropriate use of load factors.

54.2 ACI 318-99 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new ACI 318-99 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from ACI 31899, unless noted otherwise. RAM Concept uses loading types to determine the appropriate factors in some load combinations.

Note: Some load combinations in mat (raft) files are of the Lateral Group type and use a “Zero-Tension” analysis. Since a load combination using a “Zero-Tension” analysis does NOT use Alternate Envelope Factors, then such load combinations in mat files have been expanded into multiple load combinations. See Chapter 11, “Specifying Load Combinations” for further description.

54.2.1 All Dead LC This load combination sums all of the dead loadings, with a load factor of 1.0, that act simultaneously in the standard service condition. This load combination is for information only - it is not used by RAM Concept for design purposes.

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54.2.2 Initial Service LC This load combination is intended for checking requirements upon application of prestress. The load factors used are: Balance Loading: 1.13 (std & alt) (this includes a 13% increase for long-term losses, which have normally not occurred at this stage)

Note: Although elastic shortening produces a short-term loss, in RAM Concept elastic shortening losses are considered part of the long term loss lump sum. Self-Dead Loading: 1.0 (std & alt) Temporary Construction Loading (At Stressing): 1.0 (std & alt)

54.2.3 Service LC: D + L + Lr This load combination is intended for checking the serviceability limit state. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt)

54.2.4 Service LC: D + L + S This load combination is intended for checking the serviceability limit state. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 1.0 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

54.2.5 Sustained Service LC This load combination is intended for checking the serviceability limit state. For the purpose of this load combination, 100% of the Live (Storage) Loading and 50% of all other live loading is assumed to be permanent loading. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std & alt) Live (Unreducible) Loading: 0.5 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 0.5 (std & alt)

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Chapter 54 Live (Roof) Loading: 0.5 (std & alt)

54.2.6 DL + 0.25LL LC This load combination is intended for checking the requirements of UBC section 1918.9.2.2. This load combination is used by the DL + 0.25LL Design Rule Set. The load factors used are: Dead Loading: 1.0 (std & alt) Live Loading: 0.25 (std) & 0.0 (alt)

54.2.7 Factored LC: 1.4D + 1.7L + 1.7S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.4 (std) and 0.9 (alt) Live Loading: 1.7 (std) and 0.0 (alt) Snow Loading: 1.7 (std) and 0.0 (alt)

54.2.8 Service Wind LC: D + L + Lr + W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std & alt) Service Wind Loading: 1.0 (std & alt)

54.2.9 Service Wind LC: D + L + S + W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 1.0 (std & alt) Live (Unreducible) Loading: 1.0 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 1.0 (std & alt) Service Wind Loading: 1.0 (std & alt)

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54.2.10 Service Wind LC: 0.6D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 0.6 (std & alt) Service Wind Loading: 1.0 (std & alt)

54.2.11 Service Seismic LC: D + L + Lr + 0.7E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. It is currently only generated for mat foundations. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std & alt) Ultimate Seismic Loading: 0.7 (std & alt)

54.2.12 Service Seismic LC: D + L + S + 0.7E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. It is currently only generated for mat foundations. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 1.0 (std & alt) Live (Unreducible) Loading: 1.0 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 1.0 (std & alt) Snow Loading: 1.0 (std & alt) Ultimate Seismic Loading: 0.7 (std & alt)

54.2.13 Service Seismic LC: 0.6D + 0.7E This load combination is intended for checking the serviceability limit state with applied seismic loads. It is currently only generated for mat foundations. This load combination is taken from IBC 2000 section 1605.3.1. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 0.6 (std & alt) Ultimate Seismic Loading: 0.7 (std & alt)

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54.2.14 Factored Wind LC: 1.05D + 1.28L + 1.28S + 1.6W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.05 (std) & 0.9 (alt) Live Loading: 1.28 (std) & 0.0 (alt) Snow Loading: 1.28 (std) & 0.0 (alt) Service Wind Loading: 1.6 (std & alt)

Note: Since directionality factors were introduced in ASCE 7-98, the wind portion of the “Factored Wind LC: 1.05D + 1.28L + 1.28S + 1.6W” load combination has been increased to 1.6 to account for this effect. The need for this change is described in detail in ACI-02 9.2.1(b) and commentary. If directionality factors are not applied to the wind loads, the wind factors may be reduced in accordance with the original ACI 318-99 combinations. 54.2.15 Factored Seismic LC: 1.2D + f1L + 0.7S + E This load combination is intended for checking the strength limit state with applied seismic and live loads. This load combination is taken from IBC 2000 section 1605.2.1. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.7 (std) & 0.0 (alt) Ultimate Seismic Loading: 1.0 (std & alt)

54.3 ACI318-99 / ASCE-7 / IBC 2003 live load factors It is recommended that, in order to get the appropriate factors, you draw: • assembly loads (or live loads in excess of 100 psf) on a Live (Unreducible) layer

54.4 ACI 318-99 material behaviors This section explains how RAM Concept models the concrete, non-prestressed reinforcement and prestressed reinforcement when using ACI 318-99.

54.4.1 Concrete Behavior You define the concrete elastic modulus in the materials window. You can choose to use code equation 8.5.1 with or without the inclusion of W c, an equation from another code, or a specified value.

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Chapter 54 When you directly specify values, there must be two elastic modulus values: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions When the ACI code equation 8.5.1 (w/ Wc) is selected the following values are used: E ci = w c E c = wc

1.5

1.5

33 f ci 33 f c

When the ACI code equation 8.5.1 (no Wc) is selected the following values are used: E ci = 57000 f ci E c = 57000 f c Where fci = cylinder strength at stressing fc = 28 day cylinder strength For calculations based on the gross section, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses the stress strain curves are described in “Concrete Stress-Strain Curves” on page 398 of Chapter 51, “Section Design Notes”. The strength stress-strain curves are truncated at a strain of 0.003. The other stress-strain curves have no limit strain.

54.4.2 (Non-prestressed) Reinforcement Behavior This material is described in “Non-prestressed Reinforcement Stress-Strain Curves” on page 395 of Chapter 51, “Section Design Notes”.

54.4.3 Bonded Prestressed Reinforcement Behavior This material is described in “Post-tensioning Material Stress-Strain Curves” on page 395, and “Relationship of Bonded Post-tensioning Strains to Cross-Section Strains” on page 396, of Chapter 51, “Section Design Notes”.

54.4.4 Unbonded Prestressed Reinforcement Behavior For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For DL + 0.25LL strength conditions, RAM Concept assumes that unbonded tendons have no stress. For ultimate resistance moment calculations, RAM Concept’s general approach to unbonded tendon stress-strain curves is detailed in “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397 of Chapter 51, “Section Design Notes”. For ACI 318-99, the maximum unbonded tendon stress, flimit, is defined by equations 18-4 and 18-5. In the calculation of ρp, RAM Concept assumes the tendons are placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section). 432

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54.5 ACI 318-99 code rule selection The following explains how RAM Concept decides which ACI 318-99 code rules to apply based on the design strip segment or design section properties, combined with the active design rules for the rule set under consideration.

54.5.1 Minimum Reinforcement • The structural system (as defined in the design section or design strip segment) is considered (beam, one-way slab, twoway slab). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The placement of the reinforcement is based on the “min. reinforcement location” selection for the design strip segment or design section: • Elevated Slab – Reinforcement is at top near supports and bottom near midspan. • Mat Foundation – Reinforcement is at bottom near supports and top near midspan. • Tension Face – Reinforcement location is determined by the design moment envelope for the rule set (reinforcement may be required on both faces). • Top – Reinforcement is always located at the top of slab (Engineer discretion advised) • Bottom – Reinforcement is always located at the bottom of slab (Engineer discretion advised) • None – No reinforcement is provided (Engineer discretion advised) • Section 18.9.3.2 is not applied (here), as that is a service reinforcement requirement, not a minimum reinforcement requirement (see “Service” on page 434). • Section 18.8.3 is not applied to two-way slabs with bonded post-tensioning, even though the code technically requires it. • Code Rules are applied as shown in the following table Design System

RC

PT

Beam

10.5.1

18.8.3, 18.9.2

One-Way Slab

7.12

18.8.3, 18.9.2

Two-Way Slab

7.12

18.9.3.3 (at supports only)

Table 54-1 Minimum reinforcement rule mapping

54.5.2 Initial Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • Code Rules are applied as shown in the following table Design System

RC

PT

Beam

(none)

18.4.1a, 18.4.1b

One-Way Slab

(none)

18.4.1a, 18.4.1b

Two-Way Slab

(none)

18.4.1a, 18.4.1b

Table 54-2 Initial service rule mapping

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54.5.3 Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.6.4

18.4.2b, 18.4.2c

One-Way Slab

10.6.4

18.4.2b, 18.4.2c

Two-Way Slab

(none)

18.4.2b, 18.4.2c, 18.9.3.2

Table 54-3 Service rule mapping

54.5.4 Sustained Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

(none)

18.4.2a

One-Way Slab

(none)

18.4.2a

Two-Way Slab

(none)

18.4.2a

Table 54-4 Sustained service rule mapping

54.5.5 Strength • Tendons are considered as an internal section force (and the hyperstatic loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • See “Torsion Considerations” on page 405 for how torsion is implemented. • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7

One-Way Slab

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7

Two-Way Slab

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7

Table 54-5 Strength rule mapping

Note: * - 11.6 is applied only if “beam” torsion is selected (see torsion design notes)

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54.5.6 Ductility • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The longitudinal reinforcement from all other designs (except other ductility) is considered to be in place before ductility reinforcement is added. • The bending moments sign (or signs) is determined by the moment envelope for the rule set layer (ductility could be required for both positive and negative moments). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.3.3

18.8.1

One-Way Slab

10.3.3

18.8.1

Two-Way Slab

10.3.3

18.8.1

Table 54-6 Ductility rule mapping

54.5.7 UBC DL + 0.25 LL • UBC section 1918.9.2.2 is implemented. • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • Unbonded tendons are assumed to have no stress. • A strength reduction factor (φ) of 1.0 is used in the ACI calculations. • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

(none)

11.4, 18.7 (φ=1)

One-Way Slab

(none)

11.4, 18.7 (φ=1)

Two-Way Slab

(none)

(none)

Table 54-7 UBC DL + 0.25LL rule mapping

54.6 ACI 318-99 code implementation

54.6.1 Section 7.12 Shrinkage and Temperature Reinforcement • 7.12.2.1 and 7.12.2.2 are implemented • The gross area of concrete after taking into account the “ignore top depth” and the “ignore bottom depth” is used to determine the reinforcement specified in 7.12.2.1. • For members that contain rebar with different yield stresses, the ratios of 7.12.2.1(a) or 7.12.2.1(c) will be satisfied for whichever provides the least amount of reinforcement. In the calculation of 7.12.2.1(c) only reinforcement with fy = 60,000 psi will be used in the calculation. • Ratio is limited to a lower bound of 0.0014 in accordance with 7.12.2.1

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Chapter 54 • The specified bar size is used to determine the required reinforcement for satisfying the maximum spacing in 7.12.2.2. The number of bars is not rounded up to the next whole number in this calculation, but will be rounded up to the next whole number in the reinforcement summary. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations. • For the “elevated slab” and “mat foundation” minimum reinforcement patterns, an inflection point ratio of 0.2113 is assumed. • Post-tensioning is ignored.

54.6.2 Section 10.2 Factored Moment Resistance (Non prestressed) • Reinforcement areas are not deducted from the concrete area. • Strain compatibility design is used • RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See “Ductility” on page 435 for more information on applying ductility requirements. • Post-tensioning Tendon forces are ignored • Axial forces (loads) on the section are either considered or ignored based on the settings in the design section of design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. • At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. • User Es values are used • For sections with multiple values of f’c, the f’c of each concrete block is used appropriately. • For cross sections with very small moments, the amount of reinforcement calculated by RAM Concept may exceed the amount necessary. This is because RAM Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement RAM Concept selects is that necessary for axial force equilibrium in the cross section.

54.6.3 Section 10.3.3 Ductility (Non prestressed) • The strain distribution used in section 10.2 calculations is used (see “Section 10.2 Factored Moment Resistance (Non prestressed)” on page 436 for details). • The neutral axis depth is limited to: (0.75) * (0.003 /(0.003 + εy)) * d where εy = maximum reinforcement yield strain of all reinforcement in the cross section in tension d = depth of tensile reinforcement centroid (excluding PT) • Due to very large bar covers or other unusual conditions, the “compression” bar will be considered when determining “d” if the “compression” bar is in tension. • For details on how the neutral axis depth limit is related to the code criterion, see “Unified Design Recommendations for Reinforced....” by Antoine Naaman in ACI Structural Journal, pp 200-210, Vol 89, no.2, April-March 1992

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54.6.4 Section 10.5.1 Minimum Reinforcement of Flexural Members (Non Prestressed) • Equation 10-3 and the 200 bwd/fy criteria are implemented • Equation 10-3 is calculated using the maximum fc’, minimum fy, and maximum d (of all bars on the appropriate face). • bw is taken the core width (see “Concrete “Core” Determination” on page 405). If the core width is zero (there is no core), then bw is taken as the width of the section. • The bending strength of the section is designed to be at least 1.2 Mcr. This will only control in odd circumstances such as where the specified cover is extremely large. • Post-tensioning is ignored.

54.6.5 Section 10.6.4 Minimum Reinforcement of Flexural Members (Non Prestressed) • Equation 10-5 and the 12(36/fs) criteria are implemented • A cracked section analysis is performed to calculate the stress in the reinforcement. • Iteration is used to find the minimum number of bars that meets the criteria. A non-integral number of bars may be used. • The section width used to determine the spacing is the width of the solid areas of the extreme tension face. For beams with stems in tension, this will typically be the sum of the stem widths. • The spacing is considered as the width divided by the number of bars. An additional bar is not added to make the width start and end with a bar. • Post-tensioning is ignored (except as it naturally affects the cracked section calculations). • RAM Concept may use more reinforcement than “necessary” in two circumstances: • The reinforcement is necessary for equilibrium in the cracked section analysis. • Compression reinforcement added later in the design process lowers the reinforcement demands.

54.6.6 Section 11.3 Shear Resistance of Beams (Non Prestressed) • See “Concrete “Core” Determination” on page 405. • For sections with multiple values of f’c, the minimum f’c is used • Equations 11-5, 11-13, 11-15 are implemented. • Section 11.1.2 is implemented (but optional 11.1.2.1 is not). • Sections 11.5.2, 11.5.4.3 and 11.5.6.9 are implemented. • Lightweight concrete is not considered. • A minimum reinforcement criterion of section 11.5.5 is implemented; if the member is a slab, then this requirement is waived per 11.5.5.1a. • Axial Compression (or Tension) is not considered • If “beam” torsion design is selected, see “Section 11.6 Beam Torsion” on page 438 for further requirements.

54.6.7 Section 11.4 Shear Resistance of Beams (Prestressed) • See “Concrete “Core” Determination” on page 405. • For sections with multiple values of f’c, the minimum f’c is used • If stirrups are provided, the depth of the section is considered to be the larger of 0.8 h or the actual tension reinforcing depth; otherwise the depth is considered to be the tension reinforcement depth. • Lightweight concrete is not considered. • Equation 11-9 is used if the 40% criterion of section 11.4.1 is met; otherwise equation 11-5 is used. When equation 11-5 is used, both the tension mild steel and the PT in the tension zone is used to determine ρw.

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Chapter 54 • Equations 11-13 and 11-15 are implemented. • Section 11.1.2 is implemented (but optional 11.1.2.1 is not). • Sections 11.5.2, 11.5.4.1, 11.5.4.3 and 11.5.6.9 are implemented. • A minimum reinforcement criterion of section 11.5.5 is implemented; if the member is a slab, then this requirement is waived per 11.5.5.1a. • Axial Compression (or Tension) is not considered • If “beam” torsion design is selected, see “Section 11.6 Beam Torsion” on page 438 for further requirements. • No check is made to ensure that the structure is post-tensioned.

54.6.8 Section 11.6 Beam Torsion • Only the “core” of a cross section is used for torsion design. • If the core consists of multiple ribs, then the torsion calculations are performed for an average rib: • rib width = total core width / num ribs • with ultimate forces scaled down by the number of ribs (/ num ribs) and capacity and reinforcement scaled back up by the number of ribs (* num ribs). • To get a more detailed and exact calculation, use a separate design section or design strip for each rib. • The side cover is assumed to be equal to the lesser of the top cover and the bottom cover. • Acp and pcp only consider the cross section “core”. • Ao is assumed to be equal to 0.85 Aoh per 11.6.3.6. • θ in equations 11-21 and 11-22 is always taken as 45°. • The balance loading axial force and the entire cross section area are used to determine fcp. • The minimum f’c of the cross section is used in the unusual situation where a cross section contains multiple concrete mixes. • Torsion reinforcement is limited to 60 ksi per 11.6.3.4. • Longitudinal Reinforcement: • By rearranging code equations 11-21 and 11-22, the longitudinal reinforcement can be calculated as follows: A 1 f y 1 = T n ( p h ⁄ 2A 0 ) cot θ • By rearranging code equation 11-24, the minimum longitudinal reinforcement can be calculated as follows: A 1 f y 1 = 5 ⋅ f′c ⋅ A cp – ( 25psi ) ⋅ p h ⋅ b w • Longitudinal Reinforcement is designed in Pass 1. • Longitudinal Reinforcement is added to the bending reinforcement and reported as being due to both designs: • Transverse Reinforcement: • Transverse reinforcement is designed in Pass 2. • Stirrups/links are assumed to be closed hoops. RAM Concept will report the reinforcement in terms of the number of legs specified (by the user), but the calculations assume a hoop shape. The link detailing reported by RAM Concept will be difficult to decipher if the number of legs specified by the user is not 2. • Section 11.6.3.1 (equation 11-18) is implemented such that shear capacity is reduced by torsion. For very high torsions, this can make shear capacity negative. • The spacing of transverse reinforcement is determined by 11.6.6.1. • The area of transverse reinforcement is determined by 11.6.3.6

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Chapter 54 • Minimum transverse reinforcement is determined by 11.6.5.1 and 11.6.5.2 • Torsional longitudinal reinforcement is considered along with other longitudinal reinforcement when determining effective depths and other bending parameters that affect shear design.

54.6.9 Chapter 13 (Two-way slab systems) • With the exception of span detailing, this chapter is not used for reinforcement design calculations, specifically: Section 13.5.3.2 (Unbalanced moment transfer)

• This section is not considered.

54.6.10 Section 18.4.1a Initial (at stressing) Compressive Stress Limit • 0.6 f’ci is the limiting value. • For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. • For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. • No check is made to ensure that the structure is post-tensioned.

54.6.11 Section 18.4.1b Initial (at stressing) Tensile Stress Limit • 3 f′ci is the limiting value. • For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. • For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. • The limiting stress is reported, but reinforcement per section 18.4.1 is added to resist the total tensile force if necessary, so no section will fail this criterion. • Bonded tendons that are at an angle (vertical or horizontal) to the cross section will only have their component perpendicular to the cross section considered. • Usable reinforcing stresses are limited to 0.6fy and 30,000 psi. • No check is made to ensure that the structure is post-tensioned. • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

54.6.12 Section 18.4.2a Sustained Compressive Stress Limit • 0.45 f’c is the limiting value. • Gross-section, linear-elastic stress calculations are used. • For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. • For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. • No check is made to ensure that the structure is post-tensioned.

54.6.13 Section 18.4.2b Service Compressive Stress Limit • 0.60 f’c is the limiting value. • Gross-section, linear-elastic stress calculations are used. • For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. • For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. • No check is made to ensure that the structure is post-tensioned.

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54.6.14 Section 18.4.2c Service Tensile Stress Limit • 6 f′c is the limiting value. • Gross-section, linear-elastic stress calculations are used. • For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. • For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. • No check is made to ensure that the structure is post-tensioned.

54.6.15 Section 18.7 Design Flexural Resistance (Prestressed) • See “Section 10.2 Factored Moment Resistance (Non prestressed)” on page 436. Note that if axial forces are included in the design (per the design span or design section setting), then the diversion of post-tensioning forces into supports will cause a hyperstatic (secondary) tension in many design sections, as is appropriate. • Post-tensioning Tendons are included. • Bonded tendon strains are calculated using strain compatibility (see detailed description “Relationship of Bonded Posttensioning Strains to Cross-Section Strains” on page 396). • If a tendon is not perpendicular (in plan) to the cross section under consideration, then vector components of the cross section strains and the tendon stresses are used. • Unbonded tendon stresses are calculated using a strain reduction factor (see detailed description “Unbonded Posttensioning Stress-Strain Curves – Program Implementation” on page 397). • If tendon centroid is closer to the extreme compression fiber than the compression reinforcement, a solution may not be possible.

54.6.16 Section 18.8.1 Ductility (Prestressed) • The strain distribution used in section 18.7 calculations is used (see “Section 18.7 Design Flexural Resistance (Prestressed)” on page 440 for details). • The neutral axis depth is limited to: (0.36/0.85) * d where d = depth of tensile reinforcement centroid • To be rational (instead of literally following the code), “d” is taken as the depth of the total tension reinforcement, not just the depth of the PT • For details on how the neutral axis depth limit is related to the code criterion, see “Unified Design Recommendations for Reinforced....” by Antoine Naaman in ACI Structural Journal, pp 200-210, Vol 89, no.2, April-March 1992

54.6.17 Section 18.8.3 Cracking Moment • For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. • For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. It is assumed that these regions will contain the peak moments and hence the first part of a span to crack; • This criterion is not applied to bonded two-way slabs, even though the code technically requires it. • The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. • See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment.

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Chapter 54 • Modulus of rupture (fcr) is 7.5 f′c times the lightweight concrete factor. The maximum f’c for the cross section is used. • Lightweight concrete factor is assumed to be Wc / 145 pcf ≤1.0. The maximum Wc for the cross section is used. • The “twice that required” criterion is not checked.

54.6.18 Section 18.9.2 Minimum Reinforcement - One Way • For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. • For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. • For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is always applied. • See “Minimum Reinforcement” on page 433 for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. • This criterion is never applied to two-way slabs. For strict adherence to ACI 318-99 this criterion should be applied to two-way slabs that do not have a uniform thickness. Under IBC 2000 and ACI 318-02 this criterion need not be used for any two-way slabs. • User defined reinforcement on the appropriate face and bonded post tensioning that is on the tension side of the centroid is counted toward this requirement. Vector components are taken of reinforcement or bonded post-tensioning that is not orthogonal to the cross section. • No check is made to ensure that the structure is post-tensioned.

54.6.19 Section 18.9.3.2 Midspan Two Way Minimum Reinforcement • For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is inside of L/3 of the support. • For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location closer than L/6 from a support. • For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is never applied. • See “Minimum Reinforcement” above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. • For strict adherence to ACI 318-99 this criterion should only be used for two-way slabs of uniform thickness (RAM Concept uses it for all slabs declared as “two-way”; section 18.9.2 should be used for two-way slabs that do not have a uniform thickness. Under ACI 318-02 and IBC 2000 it is acceptable to use this criterion for all two-way slabs.) • Gross-section, linear-elastic stress calculations are used. • For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. • For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are calculated and reported. • If 2 f′c is exceeded the entire tensile load, Nc, is taken by bonded reinforcement. • User defined reinforcement on the appropriate face and bonded post-tensioning that is in the tension zone is counted toward the requirement. Vector components are taken of reinforcement and bonded post-tensioning that are not orthogonal to the cross section. Usable bonded tendon stresses are limited to the minimum of (fpy-fse), (0.5 fpy) and 30 ksi. • Reinforcing bar stresses are limited to the minimum of (0.5 fpy) and 30 ksi. • The reinforcement is only provided where stresses exceed 2 f′c , the minimum length requirements of 18.9.4.1 are not considered. • No check is made to ensure that the structure is post-tensioned.

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54.6.20 Section 18.9.3.3 Support Two Way Minimum Reinforcement • For span segment strips, this criteria is only applied at the face of support. • For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. • For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location further than L/6 from a support. • For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is never applied. • See “Minimum Reinforcement” above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. • For strict adherence to ACI 318-99 this criterion should only be used for two-way slabs of uniform thickness (RAM Concept uses it for all slabs declared as “two-way”; section 18.9.2 should be used for two-way slabs that do not have a uniform thickness. Under ACI 318-02 and IBC 2000 it is acceptable to use this criterion for all two-way slabs.) • Acf is calculated as the maximum of the cross section area and the cross section depth times the span length. This will not always exactly match the code requirement • The location of bonded reinforcement (the 1.5 h requirement) is not checked. • The number of bars (“4 bars or wires”) is not checked. • User defined reinforcement on the appropriate face and bonded post-tensioning that is on the appropriate side of the centroid is counted toward the requirement. Vector components are taken of reinforcement and bonded post-tensioning that is not orthogonal to the cross section. • No check is made to ensure that the structure is post-tensioned.

54.6.21 Punching Shear Design Refer to Chapter 66, “Punching Shear Design Notes”.

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55 ACI 318-02 Design This appendix details RAM Concept’s implementation of ACI 318-02. The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules



55.2 ACI 318-02 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new ACI 318-02 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from ACI 318-02 / IBC 2003, unless noted otherwise. The load and strength reduction factors changed significantly in the ACI 318-02 code. In general, the load factors were reduced and are now in agreement with the strength design of other materials. The strength reduction factors were generally reduced in order to provide similar design results as the previous code (ACI 318-99). RAM Concept uses loading types to determine the appropriate factors in some load combinations. The factor on “L” in ACI 318-02 equations (9-3), (9-4), and (9-5) will be equal to 0.5 for Live (Reducible) Loading, 1.0 for Live (Unreducible) Loading, 1.0 for Live (Storage) Loading, and 1.0 for Live (Parking) Loading.


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55.2.2 Initial Service LC This load combination is intended for checking requirements upon application of prestress. The load factors used are: Balance Loading: 1.13 (std & alt) (this includes an 13% increase for long-term losses, which have normally not occurred at this stage)


55.2.3 Service LC: D + L + Lr This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt)

55.2.4 Service LC: D + L + S This load combination is intended for checking the serviceability limit state. This load combination is taken from IBC 2003. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 1.0 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

55.2.5 Sustained Service LC This load combination is intended for checking the serviceability limit state. For the purpose of this load combination, 100% of the Live (Storage) Loading and 50% of all other live loading is assumed to be permanent loading. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std & alt) Live (Unreducible) Loading: 0.5 (std & alt) 444

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Chapter 55 Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 0.5 (std & alt) Live (Roof) Loading: 0.5 (std & alt)

55.2.6 Factored LC: 1.4D This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.4 (std) and 0.9 (alt)

55.2.7 Factored LC: 1.2D + 1.6L + 0.5Lr This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live (Reducible) Loading: 1.6 (std) and 0.0 (alt) Live (Unreducible) Loading: 1.6 (std) and 0.0 (alt) Live (Storage) Loading: 1.6 (std) and 0.0 (alt) Live (Parking) Loading: 1.6 (std) and 0.0 (alt) Live (Roof) Loading: 0.5 (std) and 0.0 (alt)

55.2.8 Factored LC: 1.2D + f1L+ 1.6Lr This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live (Reducible) Loading: 0.5 (std) and 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) and 0.0 (alt) Live (Storage) Loading: 1.0 (std) and 0.0 (alt) Live (Parking) Loading: 1.0 (std) and 0.0 (alt) Live (Roof) Loading: 1.6 (std) and 0.0 (alt)

55.2.9 Factored LC: 1.2D + 1.6L + 0.5S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live (Reducible) Loading: 1.6(std) and 0.0 (alt) Live (Unreducible) Loading: 1.6 (std) and 0.0 (alt)

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Chapter 55 Live (Storage) Loading: 1.6 (std) and 0.0 (alt) Live (Parking) Loading: 1.6 (std) and 0.0 (alt) Snow Loading: 0.5 (std) and 0.0 (alt)

55.2.10 Factored LC: 1.2D + f1L+ 1.6S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live (Reducible) Loading: 0.5 (std) and 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) and 0.0 (alt) Live (Storage) Loading: 1.0 (std) and 0.0 (alt) Live (Parking) Loading: 1.0 (std) and 0.0 (alt) Snow Loading: 1.6 (std) and 0.0 (alt)

55.2.11 Service Wind LC: D + L + Lr + W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std & alt) Service Wind Loading: 1.0 (std & alt)

55.2.12 Service Wind LC: D + L + S + W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 1.0 (std & alt) Live (Unreducible) Loading: 1.0 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 1.0 (std & alt) Service Wind Loading: 1.0 (std & alt)

55.2.13 Service Wind LC: 0.6D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) 446

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Chapter 55 Dead Loading: 0.6 (std & alt) Service Wind Loading: 1.0 (std & alt)

55.2.14 Service Seismic LC: D + L + Lr + 0.7E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std & alt) Ultimate Seismic Loading: 0.7 (std & alt)

55.2.15 Service Seismic LC: D + L + S + 0.7E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 1.0 (std & alt) Live (Unreducible) Loading: 1.0 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 1.0 (std & alt) Snow Loading: 1.0 (std & alt) Ultimate Seismic Loading: 0.7 (std & alt)

55.2.16 Service Seismic LC: 0.6D + 0.7E This load combination is intended for checking the serviceability limit state with applied seismic loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 0.6 (std & alt) Ultimate Seismic Loading: 0.7 (std & alt)

55.2.17 Factored Wind LC: 1.2D + f1L+ 0.5Lr + 1.6W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt)

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Chapter 55 Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Service Wind Loading: 1.6 (std & alt)

55.2.18 Factored Wind LC: 1.2D + f1L+ 0.5S + 1.6W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.5 (std) & 0.0 (alt) Service Wind Loading: 1.6 (std & alt)

55.2.19 Factored Wind LC: 1.2D + 1.6Lr + 0.8W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std & alt) Live (Roof) Loading: 1.6 (std & alt) Service Wind Loading: 0.8 (std & alt)

55.2.20 Factored Wind LC: 1.2D + 1.6S + 0.8W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std & alt) Snow Loading: 1.6 (std & alt) Service Wind Loading: 0.8 (std & alt)

55.2.21 Factored Seismic LC: 1.2D + f1L+ f2S + E This load combination is intended for checking the strength limit state with applied seismic and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt)

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Chapter 55 Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.7 (std) & 0.0 (alt) Ultimate Seismic Loading: 1.0 (std & alt)



55.4.1 Concrete Behavior You define the concrete elastic modulus in the materials window. You can choose to use code equation 8.5.1 with or without the inclusion of W c, an equation from another code, or a specified value. When you directly specify values, there must be two elastic modulus values: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions When the ACI code equation 8.5.1 (w/ Wc) is selected the following values are used: E ci = w c E c = wc

1.5

1.5

33 f ci 33 f c

When the ACI code equation 8.5.1 (no Wc) is selected the following values are used: E ci = 57000 f ci E c = 57000 f c Where fci = cylinder strength at stressing

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Chapter 55 fc = 28 day cylinder strength For calculations based on the gross section, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses the stress strain curves are described in “Concrete Stress-Strain Curves” on page 398 of Chapter 51, “Section Design Notes”. The strength stress-strain curves are truncated at a strain of 0.003. The other stress-strain curves have no limit strain.

55.4.2 Nonprestressed Reinforcement Behavior This material is described in “Non-prestressed Reinforcement Stress-Strain Curves” on page 395 of Chapter 51, “Section Design Notes”.


55.4.4 Unbonded Prestressed Reinforcement Behavior For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For ultimate resistance moment calculations, RAM Concept’s general approach to unbonded tendon stress-strain curves is detailed in “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397 of Chapter 51, “Section Design Notes”. For ACI 318-02, the maximum unbonded tendon stress, flimit, is defined by equations 18-4 and 18-5. In the calculation of ρp, RAM Concept assumes that the tendons are placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section).


55.5.1 Code Minimum Reinforcement • The structural system (as defined in the design section or design strip segment) is considered (beam, one-way slab, twoway slab). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The placement of the reinforcement is based on the “min. reinforcement location” selection for the design strip segment or design section: • Elevated Slab – Reinforcement is at top near supports and bottom near midspan. • Mat Foundation – Reinforcement is at bottom near supports and top near midspan. • Tension Face – Reinforcement location is determined by the design moment envelope for the rule set (reinforcement may be required on both faces). • Top – Reinforcement is always located at the top of slab (Engineer discretion advised) • Bottom – Reinforcement is always located at the bottom of slab (Engineer discretion advised)

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Chapter 55 • None – No reinforcement is provided (Engineer discretion advised) • Section 18.9.3.2 is not applied (here), as that is a service reinforcement requirement, not a minimum reinforcement requirement (see “Service” on page 452). • Section 18.8.2 is not applied to two-way slabs with bonded post-tensioning, even though the code technically requires it. • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.5.1

18.8.2, 18.9.2

One-Way Slab

7.12

18.8.2, 18.9.2

Two-Way Slab

7.12



55.5.2 User Minimum Reinforcement RAM Concept allows you to specify minimum reinforcement ratios for each span segment. About User-Specified Minimum Reinforcement Ratios

Each span segment has four user-specified reinforcement ratio values: • Column Strip Top Reinforcement • Column Strip Bottom Reinforcement • Middle Strip Top Reinforcement • Middle Strip Bottom Reinforcement Concept’s User Minimum Reinforcement rule set uses these values to design reinforcement at each cross section. These values are not included in the reinforcement calculated for other rule sets. For example, the bending strength reinforcement reported in the Strength Rule Set is not in addition to the reinforcement in the User Minimum Reinforcement rule set. User Minimum Reinforcement Calculations

Concept’s User Minimum Reinforcement calculations are based on the gross area of the cross section (after trimming) and the user-specified ratios. For example: columnStripTopAs = (cross section Ac)(column strip top reinforcement ratio) Requirements

The User Minimum Reinforcement rule set will not design reinforcement unless this rule set is used by at least on load combination. Old Files

Pre-Concept 2.0 files require rebuilding of the load combinations and rule sets to have the User Minimum Reinforcement rule set added. See “Rebuilding load combinations” on page 39of Chapter 11, “Specifying Load Combinations” for further information.

55.5.3 Initial Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces).

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Chapter 55 • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

(none)

18.4.1a, 18.4.1b

One-Way Slab

(none)

18.4.1a, 18.4.1b

Two-Way Slab

(none)

18.4.1a, 18.4.1b


55.5.4 Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • The design strip segment or design section property “Environment” is used to determine the class of post-tensioned members as follows: Protected: Class C Normal: Class T Corrosive: Class U Very Corrosive: Class U • Code Rules are applied as shown in the following table. Design System RC

PT Class U

PT Class T

PT Class C

Beam

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

One-Way Slab

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

Two-Way Slab

(none)

18.3.3, 18.4.2b, (not applicable) (not applicable) 18.9.3.2



RC

PT

Beam

(none)

18.4.2a

One-Way Slab

(none)

18.4.2a

Two-Way Slab

(none)

18.4.2a


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RC

PT

Beam

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7

One-Way Slab

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7

Two-Way Slab

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7


Note: * - 11.6 is applied only if “beam” torsion is selected (see torsion design notes) 55.5.7 Ductility • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The longitudinal reinforcement from all other designs (except other ductility) is considered to be in place before ductility reinforcement is added. • The bending moments sign (or signs) is determined by the moment envelope for the rule set layer (ductility could be required for both positive and negative moments). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.3.5

(none)

One-Way Slab

10.3.5

(none)

Two-Way Slab

10.3.5

(none)



55.6.1 Section 7.12 Shrinkage and Temperature Reinforcement 7.12.2.1 and 7.12.2.2 are implemented. The gross area of concrete after taking into account the “ignore top depth” and the “ignore bottom depth” is used to determine the reinforcement specified in 7.12.2.1. For members that contain rebar with different yield stresses, the ratios of 7.12.2.1(a) or 7.12.2.1(c) will be satisfied for whichever provides the least amount of reinforcement. In the calculation of 7.12.2.1(c) only reinforcement with fy = 60,000 psi will be used in the calculation. Ratio is limited to a lower bound of 0.0014 in accordance with 7.12.2.1

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Chapter 55 The specified bar size is used to determine the required reinforcement for satisfying the maximum spacing in 7.12.2.2. The number of bars is not rounded up to the next whole number in this calculation, but will be rounded up to the next whole number in the reinforcement summary. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations. In one-way slabs, a maximum spacing of 3h is utilized in accordance with 10.5.4. In “critical” span locations in two-way slabs, a maximum spacing of 2h is utilized in accordance with 13.3.2. For cantilever span (as determined by the declaration of supports in the design strip segment), the “critical” span locations are those within L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), the “critical” span locations are those within L/6 of a support or midspan location. In other span locations in two-way slabs, a maximum spacing of 5h is utilized. For the “elevated slab” and “mat foundation” minimum reinforcement patterns, an inflection point ratio of 0.2113 is assumed. Post-tensioning is ignored. Reinforcement in Fig. R7.12.3 is not implemented.

55.6.2 Section 10.2 Factored Moment Resistance (Non prestressed) There is a significant difference in the strength design of axial/flexural members according to the 318-02 Code. Axial/flexural members are classified as “compression controlled” or “tension controlled” in accordance with 10.3.3 and 10.3.4 depending upon the tensile strain in the extreme tension reinforcement at the ultimate strain conditions (when the concrete compressive strain reaches 0.003). When the tensile strain is sufficiently large as to provide ample ductility, the section is defined as “tension controlled” and a strength reduction factor of 0.9 is used. When the tensile strain is at or below the balanced strain condition, the member is defined as “compression controlled” and a strength reduction factor of 0.65 is used. Between these tensile strain values a linear transition between 0.65 and 0.9 is used. RAM Concept uses the ratio of neutral axis depth to the depth of the resultant tensile force (rather than the depth of the extreme tension steel) to calculate the strength reduction factor. For singly reinforced sections, the results will be identical to using the depth of the extreme tension steel. For sections with multiple layers of reinforcement (including post-tensioning), this implementation will provide a smoother transition and will be conservative. In determining the compression-controlled strain limit, Concept uses the maximum of 0.002 and fy / Es. The tension-controlled strain limit is 0.005. Reinforcement areas are not deducted from the concrete area. Strain compatibility design is used. Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an over-reinforced section. See “Ductility” on page 453 for more information on applying ductility requirements. Post-tensioning Tendon forces are ignored Axial forces (loads) on the section are either considered or ignored based on the settings in the design section of design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. User Es values are used For sections with multiple values of f ’c, the f ’c of each concrete block is used appropriately.

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Chapter 55 For cross sections with very small moments, the amount of reinforcement calculated by Concept may exceed the amount necessary. This is because Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement Concept selects is that necessary for axial force equilibrium in the cross section.

55.6.3 Section 10.3.5 Ductility (Non prestressed) The strain distribution used in section 10.2 calculations is used (see “Section 10.2 Factored Moment Resistance (Non prestressed)” on page 454 for details). The ratio of neutral axis depth to the depth of the resultant tensile force is limited such that the section strain at the location of the resultant tensile force is a minimum of 0.004. Application of this section is limited to cross sections with net axial load (compression) less than 0.10fc’Ag, in accordance with section 10.3.5.

55.6.4 Section 10.5.1 Minimum Reinforcement of Flexural Members (Non Prestressed) Equation 10-3 and the 200 bwd/fy criteria are implemented. Equation 10-3 is calculated using the maximum fc', minimum fy, and maximum d (of all bars on the appropriate face). bw is taken the core width (see “Concrete “Core” Determination” on page 405). If the core width is zero (there is no core), then bw is taken as the width of the section. The bending strength of the section is designed to be at least 1.2 Mcr. This will only control in odd circumstances such as where the specified cover is extremely large. Post-tensioning is ignored. A spacing limit of 3h is utilized in accordance with 10.5.4. For typically sized beams, this limit will not control the amount of reinforcement. The provisions of section 10.5.2 are not implemented.

55.6.5 Section 10.6.4 Minimum Reinforcement of Flexural Members (Non Prestressed) Equation 10-4 and the 12(36/fs) criteria are implemented A cracked section analysis is performed to calculate the stress in the reinforcement. Iteration is used to find the minimum number of bars that meets the criteria. A non-integral number of bars may be used. The section width used to determine the spacing is the width of the solid areas of the extreme tension face. For beams with stems in tension, this will typically be the sum of the stem widths. The spacing is considered as the width divided by the number of bars. An additional bar is not added to make the width start and end with a bar. Post-tensioning is ignored (except as it naturally affects the cracked section calculations). RAM Concept may use more reinforcement than “necessary” in two circumstances: • The reinforcement is necessary for equilibrium in the cracked section analysis. • Compression reinforcement added later in the design process lowers the reinforcement demands.

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55.6.6 Section 11.3 Shear Resistance of Beams (Non Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c, the minimum f ’c is used. Equations 11-5, 11-13 (including 50bws/fy), 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.5.2, 11.5.4.1, 11.5.4.3 and 11.5.6.9 are implemented. Lightweight concrete is not considered. A minimum reinforcement criterion of section 11.5.5 is implemented; if the member is a slab, then this requirement is waived per 11.5.5.1a. Axial tension and compression are considered in accordance with sections 11.3.2.2 and 11.3.2.3. If “beam” torsion design is selected, see “Section 11.6 Beam Torsion” on page 456 for further requirements.

55.6.7 Section 11.4 Shear Resistance of Beams (Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c , the minimum f ’c is used If stirrups are provided, the depth of the section is considered to be the larger of 0.8 h or the actual tension reinforcing depth; otherwise the depth is considered to be the tension reinforcement depth. Lightweight concrete is not considered. Equation 11-9 is used to determine the shear capacity. Equations 11-13 (including 50bws/fy) and 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.5.2, 11.5.4.1, 11.5.4.3 and 11.5.6.9 are implemented. A minimum reinforcement criterion of section 11.5.5 is implemented; if the member is a slab, then this requirement is waived per 11.5.5.1a. Axial Compression (or Tension) is not considered If “beam” torsion design is selected, see “Section 11.6 Beam Torsion” on page 456 for further requirements. No check is made to ensure that the structure is post-tensioned.

55.6.8 Section 11.6 Beam Torsion Only the “core” of a cross section is used for torsion design. If the core consists of multiple ribs, then the torsion calculations are performed for an average rib: • rib width = total core width / num ribs • with ultimate forces scaled down by the number of ribs (/ num ribs) and capacity and reinforcement scaled back up by the number of ribs (* num ribs). • To get a more detailed and exact calculation, use a separate design section or design strip for each rib. The side cover is assumed to be equal to the greater of the top cover and the bottom cover.

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Chapter 55 Acp and pcp only consider the cross section “core”. Ao is assumed to be equal to 0.85 Aoh per 11.6.3.6. θ in equations 11-21 and 11-22 is always taken as 45°. The balance loading axial force and the entire cross section area are used to determine fcp. For nonprestressed members, axial force is accounted for according to section 11.6.1(c). The minimum f ’c of the cross section is used in the unusual situation where a cross section contains multiple concrete mixes. Torsion reinforcement is limited to 60 ksi per 11.6.3.4. Longitudinal Reinforcement: • By rearranging code equations 11-21 and 11-22, the longitudinal reinforcement can be calculated as follows: A 1 f y 1 = T n ( p h ⁄ 2A 0 ) cot θ • By rearranging code equation 11-24, the minimum longitudinal reinforcement can be calculated as follows: · At A 1 f y1 = 5 ⋅ f′c ⋅ A cp –  ------ ⋅ p h ⋅ f yv  s Longitudinal Reinforcement is designed in Pass 1. Longitudinal Reinforcement is added to the bending reinforcement and reported as being due to both designs. Transverse Reinforcement: • Transverse reinforcement is designed in Pass 2. • Stirrups/links are assumed to be closed hoops. RAM Concept will report the reinforcement in terms of the number of legs specified (by the user), but the calculations assume a hoop shape. The link detailing reported by RAM Concept will be difficult to decipher if the number of legs specified by the user is not 2. Section 11.6.3.1 (equation 11-18) is implemented such that shear capacity is reduced by torsion. For very high torsions, this can make shear capacity negative. The spacing of transverse reinforcement is determined by 11.6.6.1. The area of transverse reinforcement is determined by 11.6.3.6 Minimum transverse reinforcement is determined by 11.6.5.1 and 11.6.5.2 Torsional longitudinal reinforcement is considered along with other longitudinal reinforcement when determining effective depths and other bending parameters that affect shear design.

55.6.9 Chapter 13 (Two-way slab systems) With the exception of span detailing, this chapter is not used for reinforcement design calculations, specifically: Section 13.5.3.2 (Unbalanced moment transfer)

This section is not considered.

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55.6.10 Section 18.3.3 Service Tensile Stress Limit A cross-section is defined as Class U, Class T, or Class C using the design strip segment or design section property “Environment”. The limiting tensile stress values are outlined in the following table. Class U

Class T

Class C

Assumed behavior Uncracked

Transition between uncracked and cracked

Cracked

Section properties for stress calculation

Gross section

Cracked section

Tensile stress limit ft ≤ 7.5 fc′

7.5 fc′ < ft ≤ 12 fc′

No limit

Deflection calcula- Gross section tion

Consider effects of crack- Consider ing effects of cracking

Crack control

No requirement

No requirement

10.6.4 / 18.4.4

Computation of fs for crack control

Not applicable

Not applicable

Cracked section analysis

Gross section

Table 55-7

If a design strip or section is defined as Class C, but the gross tensile stresses are within the Class T limits, the provisions of 10.6.4/18.4.4 will not be applied. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. No check is made to ensure that the structure is post-tensioned.

55.6.11 Section 18.4.1a Initial (at stressing) Compressive Stress Limit 0.6 f ’ci is the limiting value. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. No check is made to ensure that the structure is post-tensioned.

55.6.12 Section 18.4.1b Initial (at stressing) Tensile Stress Limit 3 f′ci is the limiting value. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. The limiting stress is reported, but reinforcement per section 18.4.1 is added to resist the total tensile force if necessary, so no section will fail this criterion. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. Usable reinforcing stresses are limited to 0.6fy and 30,000 psi.

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Chapter 55 No check is made to ensure that the structure is post-tensioned.

55.6.13 Section 18.4.2a Sustained Compressive Stress Limit 0.45 f ’c is the limiting value. Gross-section, linear-elastic stress calculations are used. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. No check is made to ensure that the structure is post-tensioned.

55.6.14 Section 18.4.2b Service Compressive Stress Limit 0.60 f ’c is the limiting value. Gross-section, linear-elastic stress calculations are used. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. No check is made to ensure that the structure is post-tensioned.

55.6.15 Section 18.4.4 Reinforcement Spacing Limits for Class C Members The provisions of section 10.6.4 are utilized, modified by the provisions of 18.4.4. See “Section 10.6.4 Minimum Reinforcement of Flexural Members (Non Prestressed)” on page 455. The following procedure is used to determine the maximum bar spacing: • The maximum fs in the cross section is determined, including all bonded tendons in the tension zone and all bar positions. • For bonded PT in tension zone, an effectively reinforced width is calculated: 540 432 2 w i = min  --------------- – 2.5cci, --------------- ⋅ --- ⋅ numberofducts  maxf s maxf s 3 • This width is subtracted from the total tension face width, and the rebar spacing is calculated using the remaining width. • A stress limit is calculated using re-arranged equation (10-4) and compared with the fs calculated in the first step. • Rebar is added and all steps are repeated until fs is within the calculated stress limit. If tendons are used to reduce the required tension face reinforcement width, the tendon ∆fps will be limited to 36 ksi in accordance with 18.4.4.3. Rebar will be added until this limit is met. If any tendon wi or any required bar spacing is negative the bar or tendon is deemed ineffective for controlling crack width and is ignored. In the unusual circumstance where no bars or tendons are in the tension zone, no rebar will be added.

55.6.16 Section 18.7 Design Flexural Resistance (Prestressed) See “Section 10.2 Factored Moment Resistance (Non prestressed)” on page 454. Note that if axial forces are included in the design (per the design span or design section setting), then the diversion of post-tensioning forces into supports will cause a hyperstatic (secondary) tension in many design sections, as is appropriate.

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Chapter 55 Post-tensioning Tendons are included. Bonded tendon strains are calculated using strain compatibility (see detailed description “Relationship of Bonded Posttensioning Strains to Cross-Section Strains” on page 396). If a tendon is not perpendicular (in plan) to the cross section under consideration, then vector components of the cross section strains and the tendon stresses are used. Unbonded tendon stresses are calculated using a strain reduction factor (see detailed description “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397). If tendon centroid is closer to the extreme compression fiber than the compression reinforcement, a solution may not be possible.

55.6.17 Section 18.8.2 Cracking Moment For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. It is assumed that these regions will contain the peak moments and hence the first part of a span to crack; This criterion is not applied to bonded two-way slabs, even though the code technically requires it. The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment. Modulus of rupture (fcr) is 7.5 f′c times the lightweight concrete factor. The maximum f ’c for the cross section is used. Lightweight concrete factor is assumed to be Wc / 145 pcf ≤1.0. The maximum Wc for the cross section is used. The “twice that required” criterion is not checked.

55.6.18 Section 18.9.2 Minimum Reinforcement - One Way For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is always applied. See “Minimum Reinforcement” above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. This criterion is never applied to two-way slabs. For strict adherence to ACI 318-99 this criterion should be applied to twoway slabs that do not have a uniform thickness. Under IBC 2003 and ACI 318-02 this criterion need not be used for any twoway slabs. User defined reinforcement on the appropriate face and bonded post tensioning that is on the tension side of the centroid is counted toward this requirement. Vector components are taken of reinforcement or bonded post-tensioning that is not orthogonal to the cross section. No check is made to ensure that the structure is post-tensioned.

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55.6.19 Section 18.9.3.2 Midspan Two Way Minimum Reinforcement For span segment strips, this criteria is only applied when the span ratio is in the middle one-third of the span. For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is always applied. Gross-section, linear-elastic stress calculations are used. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are calculated and reported. If 2 f′c is exceeded the entire tensile load, Nc, is taken by bonded reinforcement. User defined reinforcement on the appropriate face and bonded post-tensioning that is in the tension zone is counted toward the requirement. Vector components are taken of reinforcement and bonded post-tensioning that are not orthogonal to the cross section. Usable bonded tendon stresses are limited to the minimum of (fpy – fse), (0.5 fpy) and 30 ksi. Reinforcing bar stresses are limited to the minimum of (0.5 fpy) and 30 ksi. The reinforcement is only provided where stresses exceed 2 f′c , the minimum length requirements of 18.9.4.1 are not considered. No check is made to ensure that the structure is post-tensioned.

55.6.20 Section 18.9.3.3 Support Two Way Minimum Reinforcement For span segment strips, this criteria is only applied to the first cross section at a support if the span ratio is less than L/6. See “Minimum Reinforcement” above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. Acf is calculated as the maximum of the cross section area and the cross section depth times the span length. This will not always exactly match the code requirement User defined reinforcement on the appropriate face and bonded post-tensioning that is on the appropriate side of the centroid is counted toward the requirement. Vector components are taken of reinforcement and bonded post-tensioning that is not orthogonal to the cross section. The location of bonded reinforcement (the 1.5 h requirement) is not checked. The number of bars (“4 bars or wires”) is not checked. No check is made to ensure that the structure is post-tensioned.


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56.2 ACI 318-05 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new ACI 318-05 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from ACI 318-05 / IBC 2006, unless noted otherwise. Concept uses loading types to determine the appropriate factors in some load combinations. The factor on “L” in ACI 31805 equations (9-3), (9-4), and (9-5) will be equal to 0.5 for Live (Reducible) Loading, 1.0 for Live (Unreducible) Loading, 1.0 for Live (Storage) Loading, and 1.0 for Live (Parking) Loading. For the default Load History specification, RAM Concept uses the “Service LC: D + L” combination for the maximum load case. This load combination does not contain any roof loads. For floors that contain roof loads, a more appropriate load combination will need to be specified for the maximum load history step.


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56.2.3 Service LC: D + L This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt)

56.2.4 Service LC: D + Lr This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Roof) Loading: 1.0 (std) & 0.0 (alt)

56.2.5 Service LC: D + S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Snow Loading: 1.0 (std) & 0.0 (alt)

56.2.6 Service LC: D + 0.75L + 0.75Lr This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.75 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.75 (std) & 0.0 (alt) 464

RAM Concept

Chapter 56 Live (Storage) Loading: 0.75 (std) & 0.0 (alt) Live (Roof) Loading: 0.75 (std) & 0.0 (alt)

56.2.7 Service LC: D + 0.75L + 0.75S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.75 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.75 (std) & 0.0 (alt) Live (Storage) Loading: 0.75 (std) & 0.0 (alt) Snow Loading: 0.75 (std) & 0.0 (alt)

56.2.8 Sustained Service LC This load combination is intended for checking the serviceability limit state. For the purpose of this load combination, 100% of the Live (Storage) Loading and 50% of all other live loading is assumed to be permanent loading. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std & alt) Live (Unreducible) Loading: 0.5 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Roof) Loading: 0.5 (std & alt)


56.2.10 Factored LC: 1.2D + 1.6L + 0.5Lr This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live (Reducible) Loading: 1.6 (std) and 0.0 (alt) Live (Unreducible) Loading: 1.6 (std) and 0.0 (alt) Live (Storage) Loading: 1.6 (std) and 0.0 (alt) Live (Parking) Loading: 1.6 (std) and 0.0 (alt)

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Chapter 56 Live (Roof) Loading: 0.5 (std) and 0.0 (alt)


56.2.12 Factored LC: 1.2D + 1.6L + 0.5S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live (Reducible) Loading: 1.6(std) and 0.0 (alt) Live (Unreducible) Loading: 1.6 (std) and 0.0 (alt) Live (Storage) Loading: 1.6 (std) and 0.0 (alt) Live (Parking) Loading: 1.6 (std) and 0.0 (alt) Snow Loading: 0.5 (std) and 0.0 (alt)


56.2.14 Service Wind LC: D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) 466

RAM Concept


56.2.15 Service Wind LC: D + 0.75L + 0.75Lr + 0.75W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 0.75 (std & alt) Service Wind Loading: 0.75 (std & alt)

56.2.16 Service Wind LC: D + 0.75L + 0.75S + 0.75W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.75 (std & alt) Live (Unreducible) Loading: 0.75 (std & alt) Live (Storage) Loading: 0.75 (std & alt) Live (Parking) Loading: 0.75 (std & alt) Snow Loading: 0.75 (std & alt) Service Wind Loading: 0.75 (std & alt)

56.2.17 Service Wind LC: 0.6D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 0.6 (std & alt) Service Wind Loading: 1.0 (std & alt)

56.2.18 Service Seismic LC: D + 0.7E This load combination is intended for checking the serviceability limit state with applied seismic loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Ultimate Seismic Loading: 0.7 (std & alt)

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Chapter 56

56.2.19 Service Seismic LC: D + 0.75L + 0.75Lr + 0.525E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 0.75 (std & alt) Ultimate Seismic Loading: 0.525 (std & alt)

56.2.20 Service Seismic LC: D + 0.75L + 0.75S + 0.525E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.75 (std & alt) Live (Unreducible) Loading: 0.75 (std & alt) Live (Storage) Loading: 0.75 (std & alt) Live (Parking) Loading: 0.75 (std & alt) Snow Loading: 0.75 (std & alt) Ultimate Seismic Loading: 0.525 (std & alt)


56.2.22 Factored Wind LC: 1.2D + f1L+ 0.5Lr + 1.6W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Service Wind Loading: 1.6 (std & alt) 468

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56.2.26 Factored Seismic LC: 1.2D + f1L+ f2S + E This load combination is intended for checking the strength limit state with applied seismic and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) RAM Concept

469

Chapter 56 Snow Loading: 0.7 (std) & 0.0 (alt) Ultimate Seismic Loading: 1.0 (std & alt)




1.5

1.5

33 f ci 33 f c

When the ACI code equation 8.5.1 (no Wc) is selected the following values are used: E ci = 57000 f ci E c = 57000 f c Where fci = cylinder strength at stressing fc = 28 day cylinder strength For calculations based on the gross section, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses the stress strain curves are described in “Concrete Stress-Strain Curves” on page 398 of Chapter 51, “Section Design Notes”. The strength stress-strain curves are truncated at a strain of 0.003. The other stress-strain curves have no limit strain.

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56.5.1 Code Minimum Reinforcement • The structural system (as defined in the design section or design strip segment) is considered (beam, one-way slab, twoway slab). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The placement of the reinforcement is based on the “min. reinforcement location” selection for the design strip segment or design section: • Elevated Slab – Reinforcement is at top near supports and bottom near midspan. • Mat Foundation – Reinforcement is at bottom near supports and top near midspan. • Tension Face – Reinforcement location is determined by the design moment envelope for the rule set (reinforcement may be required on both faces). • Top – Reinforcement is always located at the top of slab (Engineer discretion advised) • Bottom – Reinforcement is always located at the bottom of slab (Engineer discretion advised) • None – No reinforcement is provided (Engineer discretion advised) • Section 18.9.3.2 is not applied (here), as that is a service reinforcement requirement, not a minimum reinforcement requirement (see “Service” on page 473). • Section 18.8.2 is not applied to two-way slabs with bonded post-tensioning, even though the code technically requires it.

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RC

PT

Beam

10.5.1

18.8.2, 18.9.2

One-Way Slab

7.12

18.8.2, 18.9.2

Two-Way Slab

7.12









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RC

PT

Beam

(none)

18.4.1a, 18.4.1b

One-Way Slab

(none)

18.4.1a, 18.4.1b

Two-Way Slab

(none)

18.4.1a, 18.4.1b



PT Class U

PT Class T

PT Class C

Beam

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

One-Way Slab

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

Two-Way Slab

(none)




RC

PT

Beam

(none)

18.4.2a

One-Way Slab

(none)

18.4.2a

Two-Way Slab

(none)

18.4.2a


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RC

PT

Beam

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7

One-Way Slab

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7

Two-Way Slab

10.2, 11.3, 11.6*

11.4, 11.6*, 18.7



RC

PT

Beam

10.3.5

(none)

One-Way Slab

10.3.5

(none)

Two-Way Slab

10.3.5

(none)




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56.6.2 Section 10.2 Factored Moment Resistance (Non prestressed) There is a significant difference in the strength design of axial/flexural members according to the 318-05 Code. Axial/flexural members are classified as “compression controlled” or “tension controlled” in accordance with 10.3.3 and 10.3.4 depending upon the tensile strain in the extreme tension reinforcement at the ultimate strain conditions (when the concrete compressive strain reaches 0.003). When the tensile strain is sufficiently large as to provide ample ductility, the section is defined as “tension controlled” and a strength reduction factor of 0.9 is used. When the tensile strain is at or below the balanced strain condition, the member is defined as “compression controlled” and a strength reduction factor of 0.65 is used. Between these tensile strain values a linear transition between 0.65 and 0.9 is used. RAM Concept uses the ratio of neutral axis depth to the depth of the resultant tensile force (rather than the depth of the extreme tension steel) to calculate the strength reduction factor. For singly reinforced sections, the results will be identical to using the depth of the extreme tension steel. For sections with multiple layers of reinforcement (including post-tensioning), this implementation will provide a smoother transition and will be conservative. In determining the compression-controlled strain limit, RAM Concept uses the maximum of 0.002 and fy / Es. The tension-controlled strain limit is 0.005. Reinforcement areas are not deducted from the concrete area. Strain compatibility design is used. RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See “Ductility” on page 474 for more information on applying ductility requirements. Post-tensioning Tendon forces are ignored Axial forces (loads) on the section are either considered or ignored based on the settings in the design section of design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. User Es values are used For sections with multiple values of f ’c , the f ’c of each concrete block is used appropriately.

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Chapter 56 For cross sections with very small moments, the amount of reinforcement calculated by RAM Concept may exceed the amount necessary. This is because RAM Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement RAM Concept selects is that necessary for axial force equilibrium in the cross section.



56.6.5 Section 10.6.4 Minimum Reinforcement of Flexural Members (Non Prestressed) Equation 10-4 and the 12(40,000/fs) criteria are implemented A cracked section analysis is performed to calculate the stress in the reinforcement. Iteration is used to find the minimum number of bars that meets the criteria. A non-integral number of bars may be used. The section width used to determine the spacing is the width of the solid areas of the extreme tension face. For beams with stems in tension, this will typically be the sum of the stem widths. The spacing is considered as the width divided by the number of bars. An additional bar is not added to make the width start and end with a bar. Post-tensioning is ignored (except as it naturally affects the cracked section calculations). RAM Concept may use more reinforcement than “necessary” in two circumstances: • The reinforcement is necessary for equilibrium in the cracked section analysis. • Compression reinforcement added later in the design process lowers the reinforcement demands.

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Chapter 56

56.6.6 Section 11.3 Shear Resistance of Beams (Non Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c , the minimum f ’c is used. Equations 11-5, 11-13 (including 50bws/fy), 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.5.2, 11.5.4.1, 11.5.4.3 and 11.5.6.9 are implemented. Lightweight concrete is not considered. A minimum reinforcement criterion of section 11.5.5 is implemented; if the member is a slab, then this requirement is waived per 11.5.5.1a. Axial tension and compression are considered in accordance with sections 11.3.2.2 and 11.3.2.3. If “beam” torsion design is selected, see “Section 11.6 Beam Torsion” on page 477 for further requirements.

56.6.7 Section 11.4 Shear Resistance of Beams (Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c , the minimum f ’c is used If stirrups are provided, the depth of the section is considered to be the larger of 0.8 h or the actual tension reinforcing depth; otherwise the depth is considered to be the tension reinforcement depth. Lightweight concrete is not considered. Equation 11-9 is used to determine the shear capacity. Equations 11-13 (including 50bws/fy) and 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.5.2, 11.5.4.1, 11.5.4.3 and 11.5.6.9 are implemented. A minimum reinforcement criterion of section 11.5.5 is implemented; if the member is a slab, then this requirement is waived per 11.5.5.1a. Axial Compression (or Tension) is not considered If “beam” torsion design is selected, see “Section 11.6 Beam Torsion” on page 477 for further requirements. No check is made to ensure that the structure is post-tensioned.


RAM Concept

477




478

RAM Concept

Chapter 56


Class T

Class C



Cracked


Gross section

Cracked section


7.5 fc′ < ft ≤ 12 fc′

No limit



Crack control

No requirement

No requirement

10.6.4 / 18.4.4


Not applicable

Not applicable


Gross section

Table 56-7

Note: All post-tensioned two-way slabs are considered as Class U with ft <= 6 root fc' If a design strip or section is defined as Class C, but the gross tensile stresses are within the Class T limits, the provisions of 10.6.4/18.4.4 will not be applied. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. No check is made to ensure that the structure is post-tensioned.


56.6.12 Section 18.4.1b Initial (at stressing) Tensile Stress Limit 3 f′ci is the limiting value. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. The limiting stress is reported, but reinforcement per section 18.4.1 is added to resist the total tensile force if necessary, so no section will fail this criterion. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

RAM Concept

479

Chapter 56 Usable reinforcing stresses are limited to 0.6fy and 30,000 psi. No check is made to ensure that the structure is post-tensioned.



56.6.15 Section 18.4.4 Reinforcement Spacing Limits for Class C Members The provisions of section 10.6.4 are utilized, modified by the provisions of 18.4.4. See “Section 10.6.4 Minimum Reinforcement of Flexural Members (Non Prestressed)” on page 476. The following procedure is used to determine the maximum bar spacing: • The maximum fs in the cross section is determined, including all bonded tendons in the tension zone and all bar positions. • For bonded PT in tension zone, an effectively reinforced width is calculated: 600000 480000 2 w i = min  ------------------ – 2.5cci, ------------------ ⋅ --- ⋅ numberofducts  maxf s maxf s  3 • This width is subtracted from the total tension face width, and the rebar spacing is calculated using the remaining width. • A stress limit is calculated using re-arranged equation (10-4) and compared with the fs calculated in the first step. • Rebar is added and all steps are repeated until fs is within the calculated stress limit. If tendons are used to reduce the required tension face reinforcement width, the tendon ∆fps will be limited to 36 ksi in accordance with 18.4.4.3. Rebar will be added until this limit is met. If any tendon wi or any required bar spacing is negative the bar or tendon is deemed ineffective for controlling crack width and is ignored. In the unusual circumstance where no bars or tendons are in the tension zone, no rebar will be added.

480

RAM Concept

Chapter 56

56.6.16 Section 18.7 Design Flexural Resistance (Prestressed) See “Section 10.2 Factored Moment Resistance (Non prestressed)” on page 475. Note that if axial forces are included in the design (per the design span or design section setting), then the diversion of post-tensioning forces into supports will cause a hyperstatic (secondary) tension in many design sections, as is appropriate. Post-tensioning Tendons are included. Bonded tendon strains are calculated using strain compatibility (see detailed description “Relationship of Bonded Posttensioning Strains to Cross-Section Strains” on page 396). If a tendon is not perpendicular (in plan) to the cross section under consideration, then vector components of the cross section strains and the tendon stresses are used. Unbonded tendon stresses are calculated using a strain reduction factor (see detailed description “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397). If tendon centroid is closer to the extreme compression fiber than the compression reinforcement, a solution may not be possible.

56.6.17 Section 18.8.2 Cracking Moment For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. It is assumed that these regions will contain the peak moments and hence the first part of a span to crack; This criterion is not applied to bonded two-way slabs, even though the code technically requires it. The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment. Modulus of rupture (fcr) is 7.5 f′c times the lightweight concrete factor. The maximum f ’c for the cross section is used. Lightweight concrete factor is assumed to be Wc / 145 pcf ≤1.0. The maximum Wc for the cross section is used. The “twice that required” criterion is not checked.

56.6.18 Section 18.9.2 Minimum Reinforcement - One Way For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is always applied. See “Minimum Reinforcement” above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. This criterion is never applied to two-way slabs. For strict adherence to ACI 318-99 this criterion should be applied to twoway slabs that do not have a uniform thickness. Under IBC 2003 and ACI 318-02 this criterion need not be used for any twoway slabs.

RAM Concept

481

Chapter 56 User defined reinforcement on the appropriate face and bonded post tensioning that is on the tension side of the centroid is counted toward this requirement. Vector components are taken of reinforcement or bonded post-tensioning that is not orthogonal to the cross section. No check is made to ensure that the structure is post-tensioned.




482

RAM Concept

Chapter 57




57.2 ACI 318-08 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new ACI 318-08 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from ACI 318-08 / IBC 2009, unless noted otherwise. Concept uses loading types to determine the appropriate factors in some load combinations. The factor on “L” in ACI 31808 equations (9-3), (9-4), and (9-5) will be equal to 0.5 for Live (Reducible) Loading, 1.0 for Live (Unreducible) Loading, 1.0 for Live (Storage) Loading, and 1.0 for Live (Parking) Loading. For the default Load History specification, RAM Concept uses the “Service LC: D + L” combination for the maximum load case. This load combination does not contain any roof loads. For floors that contain roof loads, a more appropriate load combination will need to be specified for the maximum load history step.


RAM Concept

483

Chapter 57








RAM Concept






RAM Concept

485





57.2.14 Service Wind LC: D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) 486

RAM Concept


57.2.15 Service Wind LC: D + 0.75L + 0.75Lr + 0.75W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 0.75 (std & alt) Service Wind Loading: 0.75 (std & alt)

57.2.16 Service Wind LC: D + 0.75L + 0.75S + 0.75W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.75 (std & alt) Live (Unreducible) Loading: 0.75 (std & alt) Live (Storage) Loading: 0.75 (std & alt) Live (Parking) Loading: 0.75 (std & alt) Snow Loading: 0.75 (std & alt) Service Wind Loading: 0.75 (std & alt)

57.2.17 Service Wind LC: 0.6D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 0.6 (std & alt) Service Wind Loading: 1.0 (std & alt)


RAM Concept

487

Chapter 57




57.2.22 Factored Wind LC: 1.2D + f1L+ 0.5Lr + 1.6W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Service Wind Loading: 1.6 (std & alt) 488

RAM Concept

Chapter 57





489


57.2.27 Factored Seismic LC: 0.9D + E This load combination is intended for checking the strength limit state with applied seismic loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 0.9 (std & alt) Ultimate Seismic Loading: 1.0 (std & alt)




1.5

1.5

33 f ci 33 f c

When the ACI code equation 8.5.1 (no Wc) is selected the following values are used: E ci = 57000 f ci E c = 57000 f c Where fci = cylinder strength at stressing 490

RAM Concept







RAM Concept

491

Chapter 57 • None – No reinforcement is provided (Engineer discretion advised) • Section 18.9.3.2 is not applied (here), as that is a service reinforcement requirement, not a minimum reinforcement requirement (see “Service” on page 493). • Section 18.8.2 is is only applied to cross sections with bonded tendons, including two-way slabs. • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.5.1

18.8.2 (bonded), 18.9.2

One-Way Slab

7.12

18.8.2 (bonded), 18.9.2

Two-Way Slab

7.12

18.8.2 (bonded) 18.9.3.3 (at supports only)







57.5.3 Initial Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC).

492

RAM Concept

Chapter 57 • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

(none)

18.4.1a, 18.4.1c

One-Way Slab

(none)

18.4.1a, 18.4.1c

Two-Way Slab

(none)

18.4.1a, 18.4.1c



PT Class U

PT Class T

PT Class C

Beam

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

One-Way Slab

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

Two-Way Slab

(none)




RC

PT

Beam

(none)

18.4.2a

One-Way Slab

(none)

18.4.2a

Two-Way Slab

(none)

18.4.2a


RAM Concept

493

Chapter 57


RC

PT

Beam

10.2, 11.2, 11.5*

11.3, 11.5*, 18.7

One-Way Slab

10.2, 11.2, 11.5*

11.3, 11.5*, 18.7

Two-Way Slab

10.2, 11.2, 11.5*

11.3, 11.5*, 18.7



RC

PT

Beam

10.3.5

(none)

One-Way Slab

10.3.5

(none)

Two-Way Slab

10.3.5

(none)




494

RAM Concept


57.6.2 Section 10.2 Factored Moment Resistance (Non prestressed) Axial/flexural members are classified as “compression controlled” or “tension controlled” in accordance with 10.3.3 and 10.3.4 depending upon the tensile strain in the extreme tension reinforcement at the ultimate strain conditions (when the concrete compressive strain reaches 0.003). When the tensile strain is sufficiently large as to provide ample ductility, the section is defined as “tension controlled” and a strength reduction factor of 0.9 is used. When the tensile strain is at or below the balanced strain condition, the member is defined as “compression controlled” and a strength reduction factor of 0.65 is used. Between these tensile strain values a linear transition between 0.65 and 0.9 is used. RAM Concept uses the ratio of neutral axis depth to the depth of the resultant tensile force (rather than the depth of the extreme tension steel) to calculate the strength reduction factor. For singly reinforced sections, the results will be identical to using the depth of the extreme tension steel. For sections with multiple layers of reinforcement (including post-tensioning), this implementation will provide a smoother transition and will be conservative. In determining the compression-controlled strain limit, RAM Concept uses the maximum of 0.002 and fy / Es. The tension-controlled strain limit is 0.005. Reinforcement areas are not deducted from the concrete area. Strain compatibility design is used. RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See “Ductility” on page 494 for more information on applying ductility requirements. Post-tensioning Tendon forces are ignored Axial forces (loads) on the section are either considered or ignored based on the settings in the design section of design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. User Es values are used For sections with multiple values of f ’c , the f ’c of each concrete block is used appropriately.

RAM Concept

495





496

RAM Concept

Chapter 57

57.6.6 Section 11.2 Shear Resistance of Beams (Non Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c , the minimum f ’c is used. Equations 11-5, 11-13 (including 50bws/fy), 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.4.2, 11.4.5.1, 11.4.5.3 and 11.4.7.9 are implemented. Lightweight concrete is considered. A minimum reinforcement criterion of section 11.4.6 is implemented; if the member is a slab, then this requirement is waived per 11.4.6.1a. Axial tension and compression are considered in accordance with sections 11.2.2.2 and 11.2.2.3. If “beam” torsion design is selected, see “Section 11.5 Beam Torsion” on page 497 for further requirements.

57.6.7 Section 11.3 Shear Resistance of Beams (Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c , the minimum f ’c is used If stirrups are provided, the depth of the section is considered to be the larger of 0.8 h or the actual tension reinforcing depth; otherwise the depth is considered to be the tension reinforcement depth. Lightweight concrete is considered. Equation 11-9 is used to determine the shear capacity. Equations 11-13 (including 50bws/fy) and 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.4.2, 11.4.5.1, 11.4.5.3 and 11.4.7.9 are implemented. A minimum reinforcement criterion of section 11.4.6 is implemented; if the member is a slab, then this requirement is waived per 11.4.6.1a. Axial Compression (or Tension) is not considered If “beam” torsion design is selected, see “Section 11.5 Beam Torsion” on page 497 for further requirements. No check is made to ensure that the structure is post-tensioned.


RAM Concept

497




498

RAM Concept

Chapter 57


Class T

Class C



Cracked


Gross section

Cracked section


7.5 fc′ < ft ≤ 12 fc′

No limit



Crack control

No requirement

No requirement

10.6.4 / 18.4.4


Not applicable

Not applicable


Gross section

Table 57-7



57.6.12 Section 18.4.1c Initial (at stressing) Tensile Stress Limit 3 f′ci is the limiting value. The simply supported stress limit is not considered. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. The limiting stress is reported, but reinforcement per section 18.4.1 is added to resist the total tensile force if necessary, so no section will fail this criterion. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

RAM Concept

499





500

RAM Concept

Chapter 57


57.6.17 Section 18.8.2 Cracking Moment This criterion is only applied to cross sections containing bonded tendons. For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. It is assumed that these regions will contain the peak moments and hence the first part of a span to crack; This criterion is not applied to bonded two-way slabs, even though the code technically requires it. The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment. Modulus of rupture (fcr) is 7.5 f′c times the lightweight concrete factor. The maximum f ’c for the cross section is used. Lightweight concrete factor is assumed to be Wc / 145 pcf ≤1.0. The maximum Wc for the cross section is used. The “twice that required” criterion is not checked.

57.6.18 Section 18.9.2 Minimum Reinforcement - One Way For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is always applied. See “Minimum Reinforcement” above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. This criterion is never applied to two-way slabs.

RAM Concept

501





502

RAM Concept

Chapter 58




58.2 ACI 318-11 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new ACI 318-11 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from ACI 318-11 /ASCE 7-10 unless noted otherwise. Concept uses loading types to determine the appropriate factors in some load combinations. The factor on “L” in ACI 31811 equations (9-3), (9-4), and (9-5) will be equal to 0.5 for Live (Reducible) Loading, 1.0 for Live (Unreducible) Loading, 1.0 for Live (Storage) Loading, and 1.0 for Live (Parking) Loading. For the default Load History specification, RAM Concept uses the “Service LC: D + L” combination for the maximum load case. This load combination does not contain any roof loads. For floors that contain roof loads, a more appropriate load combination will need to be specified for the maximum load history step.


RAM Concept

503

Chapter 58








RAM Concept






RAM Concept

505





58.2.14 Service Wind LC: D + 0.6W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) 506

RAM Concept

Chapter 58 Dead Loading: 1.0 (std & alt) Ultimate Wind Loading: 0.6 (std & alt)

58.2.15 Service Wind LC: D + 0.75L + 0.75Lr + 0.45W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 0.75 (std & alt) Ultimate Wind Loading: 0.45 (std & alt)

58.2.16 Service Wind LC: D + 0.75L + 0.75S + 0.45W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.75 (std & alt) Live (Unreducible) Loading: 0.75 (std & alt) Live (Storage) Loading: 0.75 (std & alt) Live (Parking) Loading: 0.75 (std & alt) Snow Loading: 0.75 (std & alt) Ultimate Wind Loading: 0.45 (std & alt)

58.2.17 Service Wind LC: 0.6D + 0.6W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 0.6 (std & alt) Ultimate Wind Loading: 0.6 (std & alt)


RAM Concept

507

Chapter 58




58.2.22 Factored Wind LC: 1.2D + f1L+ 0.5Lr + W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Ultimate Wind Loading: 1.0 (std & alt) 508

RAM Concept

Chapter 58

58.2.23 Factored Wind LC: 1.2D + f1L+ 0.5S + W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.5 (std) & 0.0 (alt) Ultimate Wind Loading: 1.0 (std & alt)

58.2.24 Factored Wind LC: 1.2D + 1.6Lr + 0.5W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std & alt) Live (Roof) Loading: 1.6 (std & alt) Ultimate Wind Loading: 0.5 (std & alt)

58.2.25 Factored Wind LC: 1.2D + 1.6S + 0.5W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std & alt) Snow Loading: 1.6 (std & alt) Ultimate Wind Loading: 0.5 (std & alt)


509


58.2.27 Factored Seismic LC: 0.9D + E This load combination is intended for checking the strength limit state with applied seismic loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 0.9 (std & alt) Ultimate Seismic Loading: 1.0 (std & alt)

58.3 ACI318-11 / ASCE-7 / live load factors It is recommended that, in order to get the appropriate factors, you draw: • assembly loads (or live loads in excess of 100 psf) on a Live (Unreducible) layer



1.5

1.5

33 f ci 33 f c

When the ACI code equation 8.5.1 (no Wc) is selected the following values are used: E ci = 57000 f ci E c = 57000 f c Where fci = cylinder strength at stressing 510

RAM Concept







RAM Concept

511

Chapter 58 • None – No reinforcement is provided (Engineer discretion advised) • Section 18.9.3.2 is not applied (here), as that is a service reinforcement requirement, not a minimum reinforcement requirement (see “Service” on page 513). • Section 18.8.2 is is only applied to cross sections with bonded tendons, including two-way slabs. • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.5.1

18.8.2 (bonded), 18.9.2

One-Way Slab

7.12

18.8.2 (bonded), 18.9.2

Two-Way Slab

7.12

18.8.2 (bonded) 18.9.3.3 (at supports only)








512

RAM Concept


RC

PT

Beam

(none)

18.4.1a, 18.4.1c

One-Way Slab

(none)

18.4.1a, 18.4.1c

Two-Way Slab

(none)

18.4.1a, 18.4.1c



PT Class U

PT Class T

PT Class C

Beam

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

One-Way Slab

10.6.4

18.3.3, 18.4.2b 18.3.3, 18.4.2b 10.6.4, 18.4.4

Two-Way Slab

(none)




RC

PT

Beam

(none)

18.4.2a

One-Way Slab

(none)

18.4.2a

Two-Way Slab

(none)

18.4.2a


RAM Concept

513

Chapter 58


RC

PT

Beam

10.2, 11.2, 11.5*

11.3, 11.5*, 18.7

One-Way Slab

10.2, 11.2, 11.5*

11.3, 11.5*, 18.7

Two-Way Slab

10.2, 11.2, 11.5*

11.3, 11.5*, 18.7



RC

PT

Beam

10.3.5

(none)

One-Way Slab

10.3.5

(none)

Two-Way Slab

10.3.5

(none)




514

RAM Concept


58.6.2 Section 10.2 Factored Moment Resistance (Non prestressed) Axial/flexural members are classified as “compression controlled” or “tension controlled” in accordance with 10.3.3 and 10.3.4 depending upon the tensile strain in the extreme tension reinforcement at the ultimate strain conditions (when the concrete compressive strain reaches 0.003). When the tensile strain is sufficiently large as to provide ample ductility, the section is defined as “tension controlled” and a strength reduction factor of 0.9 is used. When the tensile strain is at or below the balanced strain condition, the member is defined as “compression controlled” and a strength reduction factor of 0.65 is used. Between these tensile strain values a linear transition between 0.65 and 0.9 is used. RAM Concept uses the ratio of neutral axis depth to the depth of the resultant tensile force (rather than the depth of the extreme tension steel) to calculate the strength reduction factor. For singly reinforced sections, the results will be identical to using the depth of the extreme tension steel. For sections with multiple layers of reinforcement (including post-tensioning), this implementation will provide a smoother transition and will be conservative. In determining the compression-controlled strain limit, RAM Concept uses the maximum of 0.002 and fy / Es. The tension-controlled strain limit is 0.005. Reinforcement areas are not deducted from the concrete area. Strain compatibility design is used. RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See “Ductility” on page 514 for more information on applying ductility requirements. Post-tensioning Tendon forces are ignored Axial forces (loads) on the section are either considered or ignored based on the settings in the design section of design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. User Es values are used For sections with multiple values of f ’c , the f ’c of each concrete block is used appropriately.

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516

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58.6.6 Section 11.2 Shear Resistance of Beams (Non Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c , the minimum f ’c is used. Equations 11-5, 11-13 (including 50bws/fy), 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.4.2, 11.4.5.1, 11.4.5.3 and 11.4.7.9 are implemented. Lightweight concrete is considered. A minimum reinforcement criterion of section 11.4.6 is implemented; if the member is a slab, then this requirement is waived per 11.4.6.1a. Axial tension and compression are considered in accordance with sections 11.2.2.2 and 11.2.2.3. If “beam” torsion design is selected, see “Section 11.5 Beam Torsion” on page 517 for further requirements.

58.6.7 Section 11.3 Shear Resistance of Beams (Prestressed) See “Concrete “Core” Determination” on page 405. For sections with multiple values of f ’c , the minimum f ’c is used If stirrups are provided, the depth of the section is considered to be the larger of 0.8 h or the actual tension reinforcing depth; otherwise the depth is considered to be the tension reinforcement depth. Lightweight concrete is considered. Equation 11-9 is used to determine the shear capacity. Equations 11-13 (including 50bws/fy) and 11-15 are implemented. Section 11.1.2 is implemented (but optional 11.1.2.1 is not). Sections 11.4.2, 11.4.5.1, 11.4.5.3 and 11.4.7.9 are implemented. A minimum reinforcement criterion of section 11.4.6 is implemented; if the member is a slab, then this requirement is waived per 11.4.6.1a. Axial Compression (or Tension) is not considered If “beam” torsion design is selected, see “Section 11.5 Beam Torsion” on page 517 for further requirements. No check is made to ensure that the structure is post-tensioned.


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517




518

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Chapter 58


Class T

Class C



Cracked


Gross section

Cracked section


7.5 fc′ < ft ≤ 12 fc′

No limit



Crack control

No requirement

No requirement

10.6.4 / 18.4.4


Not applicable

Not applicable


Gross section

Table 58-7



58.6.12 Section 18.4.1c Initial (at stressing) Tensile Stress Limit 3 f′ci is the limiting value. The simply supported stress limit is not considered. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. The limiting stress is reported, but reinforcement per section 18.4.1 is added to resist the total tensile force if necessary, so no section will fail this criterion. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

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520

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58.6.17 Section 18.8.2 Cracking Moment This criterion is only applied to cross sections containing bonded tendons. For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. It is assumed that these regions will contain the peak moments and hence the first part of a span to crack; This criterion is not applied to bonded two-way slabs, even though the code technically requires it. The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment. Modulus of rupture (fcr) is 7.5 f′c times the lightweight concrete factor. The maximum f ’c for the cross section is used. Lightweight concrete factor is assumed to be Wc / 145 pcf ≤1.0. The maximum Wc for the cross section is used. The “twice that required” criterion is not checked.

58.6.18 Section 18.9.2 Minimum Reinforcement - One Way For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. For a span with no supports (as determined by the declaration of supports in the design strip segment), this criterion is always applied. See “Minimum Reinforcement” above for details regarding which slab/beam face (top or bottom) that the reinforcement will have the reinforcement added. This criterion is never applied to two-way slabs.

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522

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Chapter 59

59 AS 3600-2001 Design This chapter details RAM Concept’s implementation of AS 3600-2001. The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules

59.1 AS 3600-2001 default loadings This section provides information on the loadings that RAM Concept creates by default when you start a new AS 3600-2001 file. As the purpose and use of most of the loadings are self-explanatory, only items that are particularly noteworthy are discussed here.


59.1.2 Snow Loading For generation of load combinations, this loading type describes the design snow load for a particular floor or roof, which generally consists of the ground snow load modified by any necessary factors to adjust for roof snow loads, roof shape coefficients, drifting, etc.

59.2 AS 3600-2001 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new AS 3600-2001 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from AS/NZS 1170.0, unless noted otherwise. Concept uses loading types to determine the appropriate factors in some load combinations. For the short-term case the factor ψ will be equal to 1.0 for Live (Unreducible) and Live (Storage) and 0.7 for all other live loadings. For the long-term and combination cases, the factor ψ will be equal to 0.6 for Live (Unreducible) and Live (Storage), 0.4 for Live (Reducible), and 0.0 for Live (Roof).

Note: Some load combinations in mat (raft) files are of the Lateral Group type and use a “Zero-Tension” analysis. Since a load combination using a “Zero-Tension” analysis does NOT use Alternate Envelope Factors, then such load combinations in mat files have been expanded into multiple load combinations. See Chapter 11, “Specifying Load Combinations” for further description. RAM Concept

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Note: Although elastic shortening produces a short-term loss, in RAM Concept elastic shortening losses are considered part of the long term loss lump sum. Self-Dead Loading: 0.8 (std) & 1.15 (alt) Temporary Construction Loading (At Stressing): 0.8 (std) & 1.15 (alt)

59.2.3 Service LC: D + ψ L This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.7 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 0.7 (std) & 0.0 (alt) Live (Roof) Loading: 0.7 (std) & 0.0 (alt)

59.2.4 Service LC: D + ψ L + S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

59.2.5 Max Service LC: D + L This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt)

524

RAM Concept

Chapter 59 Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt)

59.2.6 Ultimate LC: 1.35D This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.35 (std) and 0.9 (alt)

59.2.7 Ultimate LC: 1.2D + 1.5L This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live Loading: 1.5 (std) & 0.0 (alt)

59.2.8 Ultimate LC: 1.2D + ψ L + S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

59.2.9 Service Wind LC: D + ψ L + W This load combination is intended for checking the serviceability limit state with applied wind and live loads. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Service Wind Loading: 1.0 (std & alt)

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59.2.10 Service Seismic LC: D + ψ L + E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Service Seismic Loading: 1.0 (std & alt)

59.2.11 Ultimate Wind LC: 1.2D + ψ L + W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Ultimate Wind Loading: 1.0 (std & alt)

59.2.12 Ultimate Seismic LC: D + ψ L + E This load combination is intended for checking the strength limit state with applied seismic and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.3 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.3 (std) & 0.0 (alt) Ultimate Seismic Loading: 1.0 (std & alt)

59.2.13 Sustained Service LC This load combination is intended for use in load history deflection calculations. The long-term factors from AS/NZS 1170.0:2002 Table 4.1 are used. The load factors used are: Balance Loading: 1.0 (std & alt) 526

RAM Concept

Chapter 59 Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std & alt) Live (Unreducible) Loading: 0.6 (std & alt) Live (Storage) Loading: 0.6 (std & alt) Live (Parking) Loading: 0.4 (std & alt)

59.3 AS3600 / AS/NZS 1170.1 live load factors It is recommended that, in order to get the appropriate factors, you draw: • assembly loads on a Live (Unreducible) layer • roof loads used for floor type activities on a Live (Reducible) layer or Live (Unreducible) layer

59.4 AS 3600-2001 material behaviours This section explains how RAM Concept models the concrete, non-prestressed reinforcement and prestressed reinforcement when using AS 3600-2001.

59.4.1 Concrete Behavior You define the concrete elastic modulus in the materials window. You can choose to use code equation 6.1.2, an equation from another code, or a specified value. When you directly specify values, there must be two elastic modulus values: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions When the AS 3600-2001 code section 6.1.2 is selected the following values are used: E ci = ρ Ec = ρ

1.5

1.5

0.043 f cm i

0.043 f c m

Where fcmi = mean value of cylinder strength at stressing fcm = mean value of 28 day cylinder strength For calculations based on the gross section, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses the stress strain curves are described in “Concrete Stress-Strain Curves” on page 398 of Chapter 51, “Section Design Notes”. The strength stress-strain curves are truncated at a strain of 0.003. The other stress-strain curves have no limit strain.

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59.4.2 (Non-prestressed) Reinforcement Behaviour This material is described in “Non-prestressed Reinforcement Stress-Strain Curves” on page 395 of Chapter 51, “Section Design Notes”.


59.4.4 Unbonded Prestressed Reinforcement Behavior For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For ultimate resistance moment calculations, RAM Concept’s general approach to unbonded tendon stress-strain curves is detailed in “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397 of Chapter 51, “Section Design Notes”. For AS 3600-2001, the maximum unbonded tendon stress, flimit, is defined by section 8.1.6. In the calculation of befdp, RAM Concept assumes the tendons are placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section).

59.5 AS 3600-2001 code rule selection The following explains how RAM Concept decides which AS 3600-2001 code rules to apply based on the design strip segment or design section properties, combined with the active design rules for the rule set under consideration. Amendments #1 and #2 are included in RAM Concept’s implementation. However, the rules pertaining to Class L reinforcement are not included in RAM Concept.

59.5.1 Code Minimum Reinforcement • The structural system (as defined in the design section or design strip segment) is considered (beam, one-way slab, twoway slab). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The placement of the reinforcement is based on the “min. reinforcement location” selection for the design strip segment or design section: • Elevated Slab – Reinforcement is at top near supports and bottom near midspan. • Mat Foundation – Reinforcement is at bottom near supports and top near midspan. • Tension Face – Reinforcement location is determined by the design moment envelope for the rule set (reinforcement may be required on both faces). • Top – Reinforcement is always located at the top of slab (Engineer discretion advised) • Bottom – Reinforcement is always located at the bottom of slab (Engineer discretion advised) • None – No reinforcement is provided (Engineer discretion advised)

528

RAM Concept


RC

PT

Beam

8.1.4, 9.4.3.2

8.1.4, 9.4.3.2

One-Way Slab

8.1.4, 9.4.3.2

8.1.4, 9.4.3.2

Two-Way Slab

8.1.4, 9.4.3.2

8.1.4, 9.4.3.2








RAM Concept

529


RC

PT

Beam

(none)

8.1.4.2

One-Way Slab

(none)

8.1.4.2

Two-Way Slab

(none)

8.1.4.2



RC

PT

Beam

8.6.1 (portions)

8.6.2

One-Way Slab

9.4.1 (portions)

9.4.2

Two-Way Slab

9.4.1 (portions)

9.4.2


59.5.5 Max Service • This is intended for service load combinations where ψ = 1.0. • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

8.6.1 (portions)

(none)

One-Way Slab

9.4.1 (portions)

(none)

Two-Way Slab

9.4.1 (portions)

(none)

Table 59-4 Maximum service rule mapping

59.5.6 Strength • Tendons are considered as an internal section force (and the hyperstatic loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • See “Torsion Considerations” on page 405 for an explanation how torsion is implemented.

530

RAM Concept


RC

PT

Beam

8.1, 8.2, 8.3*

8.1, 8.2, 8.3*

One-Way Slab

8.1, 8.2, 8.3*

8.1, 8.2, 8.3*

Two-Way Slab

8.1, 8.2, 8.3*

8.1, 8.2, 8.3*



RC

PT

Beam

8.1.3

8.1.3

One-Way Slab

8.1.3

8.1.3

Two-Way Slab

8.1.3

8.1.3


59.6 AS 3600-2001 code implementation Note: Class L reinforcement provisions are not included in RAM Concept’s implementation

59.6.1 Concrete Modulus of Elasticity • The modulus of elasticity for concrete is calculated per 6.1.2(a). • The value of fcm in the calculation is taken from Table C6.1.2. Linear interpolation is used between the table values. Values outside the range of the table are interpolated conservatively (if f’c < 20 MPa, fcm = 1.2 f’c; if f’c > 50 MPa, fcm = f’c + 6.5 MPa). • This calculation must be selected in the Materials window to be used.

59.6.2 Concrete Flexural Tensile Strength • The flexural tensile strength for concrete is calculated per 6.1.1.2(a).

59.6.3 Unbonded Post-Tensioning Stress-Strain Curves • The bonded post-tensioning stress-strain curves are used, but altered as detailed below. • For service level (elastic) analysis, unbonded tendon stresses are assumed to be independent of section strains. • The tendon stress is never reduced below σp.ef. RAM Concept

531

Chapter 59 • The tendon stress is never exceeds fpy. • The tendon stress is limited by code section 8.1.6 equation (a) or (b) as appropriate.

Note: The program does not consider section 19.3.5 which states that unbonded tendons should only be used on grade; the engineer needs to take this into account before starting the design.

59.6.4 Section 8.1 Strength of Beams in Bending • Reinforcement areas are not deducted from the concrete area. • Strain compatibility design is used. See “General Design Approach” on page 395 for a description of RAM Concept’s strain compatibility design. • See “Concrete Stress-Strain Curves” on page 398 and for tendon, concrete and mild steel reinforcement stress strain curves • User Es values are used • For sections with multiple values of f’c, the f’c of each concrete block is used appropriately. • RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See “Ductility” on page 531 for applying ductility requirements. • If the section or strip is declared as not being post-tensioned, then post-tensioning Tendon forces are ignored • Axial forces (loads) on the section are either considered or ignored based on the settings in the design section or design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. • At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. • For cross sections with very small moments, the amount of reinforcement calculated by RAM Concept may exceed the amount necessary. This is because RAM Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement RAM Concept selects is that necessary for axial force equilibrium in the cross section. • The diversion of post-tensioning forces into supports (and other regions of the structure) will cause a hyperstatic (secondary) tension in many cross sections, as is appropriate. • RAM Concept does not consider section 19.3.5 which states that unbonded tendons should only be used on grade; the engineer needs to take this into account before starting the design. • Section 8.1.8 (Detailing of flexural reinforcement and tendons) is not implemented. • The standard strength reduction factor (φ) of 0.8 is used.

59.6.5 8.1.4 Minimum Flexural Strength • Cross sections within 1/6 span from supports or 1/6 span from midspan are considered “at critical sections”. • If the design section is not declared as post-tensioned in the design section or design strip segment, then the P/Ag and Pe terms of 8.1.4.1 are assumed to be zero (even if the cross section includes tendons). • The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. • See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the “cracking load”.

59.6.6 8.1.4.2 Transfer Compressive Stress Limits • The second clause in 8.1.4.2 is implemented.

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Chapter 59 • The cross section is analyzed as cracked. This analysis is somewhat more conservative than the gross section calculation suggested in the code. • The concrete compressive stresses are limited to 0.5 fcp. • If the limit stress is exceeded then reinforcement is added as required to limit the concrete stress; depending on the bending moment and axial forces, either compression reinforcement, tension reinforcement or both will be added. • For sections with multiple concrete strengths, the section limiting stress is reported as the smallest (absolute value) stress limit of all of the individual concrete areas.

59.6.7 Section 8.1.3 Ductility of Beams in Bending • See “General Design Approach” on page 395 for general information on cross section calculations. • The neutral axis depth (ku) is limited to 0.4 per section 8.1.3. Reinforcement is added to minimise the neutral axis depth. • If the reinforcing bar covers are such that the compression bar is outside of the 0.4 d zone, then a solution may not be possible. • In certain circumstances it may not be possible to simultaneously provide positive moment ductility and negative moment ductility. This most commonly happens if there is a large post-tensioning tendon near the center of the cross section.

59.6.8 Section 8.2 Shear Design • See “Concrete “Core” Determination” on page 405 for the web width (bw) calculations. • Half of the width of bonded ducts and all of the width of unbonded ducts that are located in the shear core are deducted from the bw width to determine the bv width. Where ducts are at different elevations within the core, the elevation with the maximum effective duct width is used to determine bv. • If the section is declared as “post-tensioned”, d0 is taken as the maximum of the depth of all tension reinforcement or 0.8D. No check is made to verify that the structure actually is post-tensioned. • If the section is not post-tensioned d0 is taken as the maximum depth of all tension reinforcement. • Ast is taken as the area of longitudinal reinforcement (excluding PT) that is in the tension zone for the cross section forces under consideration. • The vertical component of inclined prestressing tendons, Pv, is ignored (taken as zero). • Flexure-shear Vuc is calculated per 8.2.7.2 (a) (for non-prestressed members the Apt and V0 evaluate to zero). • V0 is calculated as M0/(M*/V*) for both determinate and indeterminate structures. • β2 is taken as 1.0 (no axial force considered). • β3 is taken as 1.0. • Apt is taken as the sum of all post-tensioning (bonded and unbonded) in the tension zone. Vector components of the tendon areas are used for tendons that are not perpendicular to the design section. • Web-shear Vuc is calculated per 8.2.7.2 (b) (for both prestressed and non-prestressed members). The calculation is performed at the centroid of the member, but the net web width (bv) is used to determine the shear stress at the centroid. The balance analysis prestressing forces and the gross section properties are used to determine the axial stress at the centroid. • Vus is calculated per 8.2.10 (a). • No increases of capacity are considered for sections or loads close to supports. • If “beam torsion” is selected, torsion design is also performed (see “Section 8.3 Beam Torsion Design” on page 534). Maximum shear capacity is reduced by section 8.3.3. If torsion reinforcement is required, then Section 8.3.4(b) is used to reduce available shear capacity. • Stirrup spacings are reduced by a factor of 0.8 per 8.2.12.4(c).

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59.6.9 Section 8.3 Beam Torsion Design • Section 8.3 is followed. • Torsion reinforcement is not provided if the requirements of 8.3.4(a)(i) are met [T* < 0.25 φ Tuc]. The requirements of 8.3.4(a)(ii) and (iii) are conservatively ignored. • All torsion is assumed to be taken by the “core”. See “Concrete “Core” Determination” on page 405 for calculation of the core. • Where the core consists of multiple ribs, the calculations are based on an average rib (and then factored up by the number of ribs). • Section 8.3.3 is used to reduce the maximum shear capacity. • In calculating At and ut, the side cover to the centroid of the longitudinal bar is assumed to be the maximum of the top cover and bottom cover to the centroid of their respective longitudinal bars. • Longitudinal torsion reinforcement in the compression zone is not reduced by the flexural compression force [8.3.6(a) is used for both tension and compression faces] • Torsion capacity is not reported; instead shear capacity is reduced by the fitments, etc. that are used to provide the required torsion capacity. • When shear acts simultaneously with torsion, Section 8.3.4(b) is considered when designing the transverse closed ties. • Transverse closed ties (Asw) are provided for the lesser of T* and Tu,max. If T* is greater than Tu,max, then the section will be reported as failing sections 8.2 and 8.3. The minimum requirements of 8.3.7(a) are also met. • Longitudinal reinforcement is provided based on the Asw value calculated for the lesser of T* and Tu,max. • Closed tie spacings are reduced by a factor of 0.8 per 8.2.12.4(c), even if the cross section is in pure torsion (no shear).

59.6.10 Section 8.6.1 RC Beam Crack Control If there are no tension stresses in the cross section, no reinforcement is provided. The cross section is considered as a “tension member” if both faces are in tension based on gross section stresses for the cross section forces being considered. (The code uses the term “primarily tension”.). User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. Section (a) - This section is not implemented here. Clause 8.1.4.1 is implemented in the minimum reinforcement design. Section (b) – This section is always used in the service design, but never used in the max service design. • Reinforcement is added on each face in tension to limit maximum spacing to 300 mm. All bars on the appropriate face (including fractional components for bars at an angle to the cross section) are considered for spacing requirements. A fractional number of bars and spaces may be used. • Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. Section (c) – This section is used if the cross section is a tension member and the environment is not protected. • For the service design: • Reinforcement is added both faces to keep the reinforcement stresses within the limits of Table 8.6.1(A). • The maximum diameter of all reinforcement assigned to a particular face is used in Table 8.6.1(A). • For the max service design: • Reinforcement is added both faces to keep the reinforcement stresses less than 0.8 fsy. Section (d) – This section is used if the cross section is not a tension member and the environment is not protected. • For the service design: 534

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Chapter 59 • Reinforcement is added both faces to keep the reinforcement stresses within the limits of Table 8.6.1(A) or Table 8.6.1(B), whichever is larger. • The maximum diameter of all reinforcement assigned to a particular face is used in Table 8.6.1(A). • The bar spacing for Table 8.6.1(B) is calculated using all bars on the appropriate face (including fractional components for bars at an angle to the cross section). Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. A fractional number of bars and number of spaces may be used. • For the max service design: • Reinforcement is added to both faces to keep the reinforcement stresses less than 0.8 fsy.

59.6.11 Section 8.6.2 PT Beam Crack Control • If the tensile stress in the concrete does not exceed 0.25 f′c then there is no need for crack control reinforcement and none of the following applies. • Section (a) with the 0.6 f′c limit is ignored because it does not give any guidance on how much reinforcement is necessary. Section (b) is always used instead. • Reinforcement is added to try to keep mild steel stress changes on the tension face within the 200 MPa as the moment changes from decompression to service level. • In extremely rare circumstances (where the service reinforcement stress in compression, even though the concrete stress exceeds 0.25 f′c ) this criterion is skipped as adding reinforcement will reduce the compression (increase the tension) making it impossible to satisfy the criterion by increasing the reinforcement. • The decompression reinforcement stress is calculated using gross section strains, while the service reinforcement stress is calculated using cracked section strains. • Reinforcement is also added if necessary to provide a centre-to-centre reinforcement spacing of 200 mm or less. • For this requirement, each bonded tendon duct that is in the tension zone (based on gross-section stresses) is considered to be equivalent to a single mild steel bar (even if it is far from the tension face). In the spacing calculation, all effective tendon ducts are assumed to be optimally positioned to minimize the number of mild steel bars required – the plan layout of the ducts is ignored. • A fractional number of bars and number of spaces may be specified to meet the spacing requirement. • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

59.6.12 Section 9.1 Strength of Slabs in Bending • Section 8.1 is used for calculating the bending strength of slabs. Any reinforcement required is reported as being due to 8.1. See “Section 8.1 Strength of Beams in Bending” above for details on the 8.1 implementation.

59.6.13 Section 9.4.1 RC Slab Crack Control User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. Section (a) –This section is not implemented here. Clause 9.1.1 is implemented in the minimum reinforcement design via clause 8.1.4.1. Section (b) – This section is always used in the service design, but never used in the max service design. • Reinforcement is added to limit maximum spacing to 300 mm or two times the cross section depth. All bars on the appropriate face (including fractional components for bars at an angle to the cross section) are considered for spacing requirements. A fraction number of bars and number of spaces may be used.

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Chapter 59 • Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. Section (c) – This section is only used for service design, but is not used in protected environments. • Reinforcement is added both faces to keep the reinforcement stresses within the limits of Table 9.4.1(A) or Table 9.4.1(B), whichever is larger. • The maximum diameter of all reinforcement assigned to a particular face is used in Table 9.4.1(A). • The bar spacing for Table 9.4.1(B) is calculated using all bars on the appropriate face (including fractional components for bars at an angle to the cross section). Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. A fractional number of bars and number of spaces may be used. Section (d) – This section is only used for max service design, but is not used in protected environments. • Reinforcement is added to both faces to keep the reinforcement stresses less than 0.8 fsy.

59.6.14 Section 9.4.2 PT Slab Crack Control • If the tensile stress in the concrete does not exceed 0.25 f′c then there is no need for crack control reinforcement and none of the following applies. • Section (a) with the 0.5 f ′c limit is ignored because it does not give any guidance on how much reinforcement is necessary. Section (b) is always used instead. • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. • Reinforcement is added to try to keep mild steel stress changes on the tension face within the 150 MPa as the moment changes from decompression to service level. In extremely rare circumstances (where the service reinforcement stress in compression, even though the concrete stress exceeds 0.25 f′c ) this criterion is skipped. • The decompression reinforcement stress is calculated by determining gross section decompression cross-section strains and applying the strains to the reinforcement. • Reinforcement is also added if necessary to provide a centre-to-centre reinforcement spacing of 500 mm or less. For this requirement, each bonded tendon duct (that is in the tension zone based on gross section stresses) is considered to be equivalent to a single mild steel bar (even if it is far from the tension face). In the spacing calculation, all bonded tendon ducts are assumed to be optimally positioned to minimize the number of mild steel bars required. A fractional number of bars and number of spaces may be specified to meet the spacing requirement.

59.6.15 Section 9.4.3.2 Shrinkage and Temperature • This criterion is applied as part of the minimum reinforcement designer as it is independent of the magnitude of forces upon a cross section. • This criterion is applied to both beams and slabs, although its application to beams is not required by AS 3600. • The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. • Reinforcement may be applied to both faces if the cross section is subject to both positive and negative moments and the “tension face” reinforcement location is chosen. • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. • The amount of reinforcement provided is equal to 0.75 (per 9.4.3.2(b)) times the amount specified by either 9.4.3.4(a)(i), 9.4.3.4(b)(i), or 9.4.3.4(c). • For “protected” environments, the amount of reinforcement provided is: A s = (0.75)(1.75 – 2.5 σcp)(Ag)/1000 • For “normal” environments, the amount of reinforcement provided is: A s = (0.75)(3.5 – 2.5 σcp)(Ag)/1000

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Chapter 59 • For “corrosive” or “very corrosive” environments, the amount of reinforcement provided is: As = (0.75)(6.0 – 2.5 σcp)(Ag)/1000 • For non-PT design strips and design sections, σcp is taken as zero.


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Chapter 59

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Chapter 60

60 AS 3600-2009 Design This chapter details RAM Concept’s implementation of AS 3600-2009. The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules

60.1 AS 3600-2009 default loadings This section provides information on the loadings that RAM Concept creates by default when you start a new AS 3600-2009 file. As the purpose and use of most of the loadings are self-explanatory, only items that are particularly noteworthy are discussed here.


60.1.2 Snow Loading For generation of load combinations, this loading type describes the design snow load for a particular floor or roof, which generally consists of the ground snow load modified by any necessary factors to adjust for roof, snow loads, roof shape coefficients, drifting, etc.

60.2 AS 3600-2009 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new AS 3600-2009 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from AS/NZS 1170.0:2002 including the latest Amendment 3 (2011) incorporating the new earthquake combination factors, unless noted otherwise. Concept uses loading types to determine the appropriate factors in some load combinations. For the short-term case the factor ψ will be equal to 1.0 for Live (Unreducible) and Live (Storage) and 0.7 for all other live loadings. For the long-term and combination cases, the factor ψ will be equal to 0.6 for Live (Unreducible) and Live (Storage), 0.4 for Live (Reducible),

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Chapter 60 and 0.0 for Live (Roof). In the case of seismic load combinations ψ will be equal to 0.3 for Live (Reducible) or Parking loads.




Note: Although elastic shortening produces a short-term loss, in RAM Concept elastic shortening losses are considered part of the long term loss lump sum. Self-Dead Loading: 0.8 (std) & 1.15 (alt) Temporary Construction Loading (At Stressing): 0.8 (std) & 1.15 (alt)

60.2.3 Service LC: D + ψ L This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.7 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 0.7 (std) & 0.0 (alt) Live (Roof) Loading: 0.7 (std) & 0.0 (alt)

60.2.4 Service LC: D + ψ L + S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt)

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Chapter 60 Snow Loading: 1.0 (std) & 0.0 (alt)

60.2.5 Max Service LC: D + L This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt)

60.2.6 Ultimate LC: 1.35D This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.35 (std) and 0.9 (alt)

60.2.7 Ultimate LC: 1.2D + 1.5L This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) and 0.9 (alt) Live Loading: 1.5 (std) & 0.0 (alt)

60.2.8 Ultimate LC: 1.2D + ψ L + S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

60.2.9 Service Wind LC: D + ψ L + W This load combination is intended for checking the serviceability limit state with applied wind and live loads. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt)

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Chapter 60 Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Service Wind Loading: 1.0 (std & alt)

60.2.10 Service Seismic LC: D + ψ L + E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Service Seismic Loading: 1.0 (std & alt)

60.2.11 Ultimate Wind LC: 1.2D + ψ L + W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std) & 0.9 (alt) Live (Reducible) Loading: 0.4 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.4 (std) & 0.0 (alt) Ultimate Wind Loading: 1.0 (std & alt)

60.2.12 Ultimate Seismic LC: D + ψ L + E This load combination is intended for checking the strength limit state with applied seismic and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.3 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.6 (std) & 0.0 (alt) Live (Parking) Loading: 0.3 (std) & 0.0 (alt) Ultimate Seismic Loading: 1.0 (std & alt)

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60.2.13 Sustained Service LC This load combination is intended for use in load history deflection calculations. The long-term factors from AS/NZS 1170.0:2002 Table 4.1 are used. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.4 (std & alt) Live (Unreducible) Loading: 0.6 (std & alt) Live (Storage) Loading: 0.6 (std & alt) Live (Parking) Loading: 0.4 (std & alt)

60.3 AS3600 / AS/NZS 1170.1 live load factors It is recommended that, in order to get the appropriate factors, you draw: • assembly loads on a Live (Unreducible) layer • roof loads used for floor type activities on a Live (Reducible) layer or Live (Unreducible) layer

60.4 AS 3600-2009 material behaviors This section explains how RAM Concept models the concrete, non-prestressed reinforcement and prestressed reinforcement when using AS 3600-2009.

60.4.1 Concrete Behavior You define the concrete elastic modulus in the materials window. You can choose to use code equation 3.1.2, an equation from another code, or a specified value. When you directly specify values, there must be two elastic modulus values: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions When the AS 3600-2009 code section 3.1.2 is selected the following values are used: E ci = ρ

1.5

0.043 f cm i when f c mi ≤ 40MPa

E ci = ρ

1.5

0.024 f cm i + 0.12 when f c mi > 40MPa

Ec = ρ

1.5

E ci = ρ

0.043 f c m when f c m ≤ 40MPa

1.5

0.024 f cm + 0.12 when f c m > 40MPa

Where fcmi = mean value of cylinder strength at stressing

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Chapter 60 fcm = mean value of 28 day cylinder strength For calculations based on the gross section, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses the stress strain curves are described in “Concrete Stress-Strain Curves” on page 398 of Chapter 51, “Section Design Notes”. The strength stress-strain curves are truncated at a strain of 0.003. The other stress-strain curves have no limit strain.

60.4.2 (Non-prestressed) Reinforcement Behaviour This material is described in “Non-prestressed Reinforcement Stress-Strain Curves” on page 395 of Chapter 51, “Section Design Notes”.


60.4.4 Unbonded Prestressed Reinforcement Behavior For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For ultimate resistance moment calculations, RAM Concept’s general approach to unbonded tendon stress-strain curves is detailed in “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397 of Chapter 51, “Section Design Notes”. For AS 3600-2009, the maximum unbonded tendon stress, flimit, is defined by section 8.1.8. In the calculation of befdp, RAM Concept assumes the tendons are placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section).

60.5 AS 3600-2009 code rule selection The following explains how RAM Concept decides which AS 3600-2009 code rules to apply based on the design strip segment or design section properties, combined with the active design rules for the rule set under consideration. Amendments #1 and #2 are included in RAM Concept’s implementation. However, the rules pertaining to Class L reinforcement are not included in RAM Concept.

60.5.1 Code Minimum Reinforcement • The structural system (as defined in the design section or design strip segment) is considered (beam, one-way slab, twoway slab). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The placement of the reinforcement is based on the “min. reinforcement location” selection for the design strip segment or design section: • Elevated Slab – Reinforcement is at top near supports and bottom near midspan. • Mat Foundation – Reinforcement is at bottom near supports and top near midspan. • Tension Face – Reinforcement location is determined by the design moment envelope for the rule set (reinforcement may be required on both faces). • Top – Reinforcement is always located at the top of slab (Engineer discretion advised)

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Chapter 60 • Bottom – Reinforcement is always located at the bottom of slab (Engineer discretion advised) • None – No reinforcement is provided (Engineer discretion advised) • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

8.1.6, 9.4.3.2

8.1.6, 9.4.3.2

One-Way Slab

8.1.6, 9.4.3.2

8.1.6, 9.4.3.2

Two-Way Slab

8.1.6, 9.4.3.2

8.1.6, 9.4.3.2








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RC

PT

Beam

(none)

8.1.6.2

One-Way Slab

(none)

8.1.6.2

Two-Way Slab

(none)

8.1.6.2



RC

PT

Beam

8.6.1 (portions)

8.6.2

One-Way Slab

9.4.1 (portions)

9.4.2

Two-Way Slab

9.4.1 (portions)

9.4.2


60.5.5 Max Service • This is intended for service load combinations where ψ = 1.0. • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

8.6.1 (portions)

(none)

One-Way Slab

9.4.1 (portions)

(none)

Two-Way Slab

9.4.1 (portions)

(none)

Table 60-4 Maximum service rule mapping

60.5.6 Strength • Tendons are considered as an internal section force (and the hyperstatic loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • See “Torsion Considerations” on page 405 for an explanation how torsion is implemented.

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RC

PT

Beam

8.1, 8.2, 8.3*

8.1, 8.2, 8.3*

One-Way Slab

8.1, 8.2, 8.3*

8.1, 8.2, 8.3*

Two-Way Slab

8.1, 8.2, 8.3*

8.1, 8.2, 8.3*



RC

PT

Beam

8.1.5

8.1.5

One-Way Slab

8.1.5

8.1.5

Two-Way Slab

8.1.5

8.1.5


60.6 AS 3600-2009 code implementation Note: Class L reinforcement provisions are not included in RAM Concept’s implementation

60.6.1 Concrete Modulus of Elasticity • The modulus of elasticity for concrete is calculated per 3.1.2(a). • The value of fcm in the calculation is taken from Table 3.1.2. Linear interpolation is used between the table values. Values outside the range of the table are interpolated conservatively (if f’c < 20 MPa, fcm = 1.2 f’c; if f’c > 50 MPa, fcm = f’c + 6.5 MPa). • This calculation must be selected in the Materials window to be used.

60.6.2 Concrete Flexural Tensile Strength • The flexural tensile strength for concrete is calculated per 3.1.1.3 as function of f'c (using the alternative option due to absence of data).

60.6.3 Unbonded Post-Tensioning Stress-Strain Curves • The bonded post-tensioning stress-strain curves are used, but altered as detailed below. • For service level (elastic) analysis, unbonded tendon stresses are assumed to be independent of section strains.

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Chapter 60 • The tendon stress is never reduced below σp.ef. • The tendon stress is never exceeds fpy. • The tendon stress is limited by code section 8.1.8 equation (a) or (b) as appropriate.

Note: The program does not consider section 17.3.5 which states that unbonded tendons should only be used on grade; the engineer needs to take this into account before starting the design.

60.6.4 Section 8.1 Strength of Beams in Bending • Reinforcement areas are not deducted from the concrete area. • Strain compatibility design is used. See “General Design Approach” on page 395 for a description of RAM Concept’s strain compatibility design. • See “Concrete Stress-Strain Curves” on page 398 and for tendon, concrete and mild steel reinforcement stress strain curves • User Es values are used • For sections with multiple values of f’c, the f’c of each concrete block is used appropriately. • RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See “Ductility” on page 547 for applying ductility requirements. • If the section or strip is declared as not being post-tensioned, then post-tensioning Tendon forces are ignored • Axial forces (loads) on the section are either considered or ignored based on the settings in the design section or design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. • At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. • For cross sections with very small moments, the amount of reinforcement calculated by RAM Concept may exceed the amount necessary. This is because RAM Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement RAM Concept selects is that necessary for axial force equilibrium in the cross section. • The diversion of post-tensioning forces into supports (and other regions of the structure) will cause a hyperstatic (secondary) tension in many cross sections, as is appropriate. • RAM Concept does not consider section 17.3.5, which states that unbonded tendons should only be used on grade; the engineer needs to take this into account before starting the design. • Section 8.1.10 (Detailing of flexural reinforcement and tendons) is not implemented. • The standard capacity reduction factor (φ) of 0.8 is used.

60.6.5 8.1.6 Minimum Flexural Strength • Cross sections within 1/6 span from supports or 1/6 span from midspan are considered “at critical sections”. • If the design section is not declared as post-tensioned in the design section or design strip segment, then the Pe/Ag and Pee terms of 8.1.6.1 are assumed to be zero (even if the cross section includes tendons), where Pe is the total effective prestress force considered. • Cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. • See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the “cracking load”.

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60.6.6 8.1.6.2 Transfer Compressive Stress Limits • The second clause in 8.1.6.2 is implemented. • The cross section is analyzed as cracked. This analysis is somewhat more conservative than the gross section calculation suggested in the code. • The concrete compressive stresses are limited to 0.5 fcp for all cases (conservative side). • If the limit stress is exceeded then reinforcement is added as required to limit the concrete stress; depending on the bending moment and axial forces, either compression reinforcement, tension reinforcement or both will be added. • For sections with multiple concrete strengths, the section limiting stress is reported as the smallest (absolute value) stress limit of all of the individual concrete areas.

60.6.7 Section 8.1.5 Ductility of Beams in Bending • See “General Design Approach” on page 395 for general information on cross section calculations. • The neutral axis depth (kou) is limited to 0.36 and M* < 0.6Mu per section 8.1.5. Reinforcement is added to minimise the neutral axis depth. Where M* is the design bending moment at a cross section and Mu is the ultimate strength in bending moment of the cross section. It is important to note that the neutral axis depth is obtained without considering the axial force. • If the reinforcing bar covers are such that the compression bar is outside of the 0.36 d zone, then a solution may not be possible. • In certain circumstances it may not be possible to simultaneously provide positive moment ductility and negative moment ductility. This most commonly happens if there is a large post-tensioning tendon near the center of the cross section.

60.6.8 Section 8.2 Shear Design • See “Concrete “Core” Determination” on page 405 for the web width (bw) calculations. • Half of the width of bonded ducts and all of the width of unbonded ducts that are located in the shear core are deducted from the bw width to determine the bv width. Where ducts are at different elevations within the core, the elevation with the maximum effective duct width is used to determine bv. • If the section is declared as “post-tensioned”, d0 is taken as the maximum of the depth of all tension reinforcement or 0.8D. No check is made to verify that the structure actually is post-tensioned. • If the section is not post-tensioned d0 is taken as the maximum depth of all tension reinforcement. • Ast is taken as the area of longitudinal reinforcement (excluding PT) that is in the tension zone for the cross section forces under consideration. • The vertical component of inclined prestressing tendons, Pv, is ignored (taken as zero). • Flexure-shear Vuc is calculated per 8.2.7.2 (a) (for non-prestressed members the Apt and V0 evaluate to zero). • V0 is calculated as M0/(M*/V*) for both determinate and indeterminate structures. • β2 is taken as 1.0 (no axial force considered). • β3 is taken as 1.0. • Apt is taken as the sum of all post-tensioning (bonded and unbonded) in the tension zone. Vector components of the tendon areas are used for tendons that are not perpendicular to the design section. • Web-shear Vuc is calculated per 8.2.7.2 (b) (for both prestressed and non-prestressed members). The calculation is performed at the centroid of the member, but the net web width (bv) is used to determine the shear stress at the centroid. The balance analysis prestressing forces and the gross section properties are used to determine the axial stress at the centroid. • Vus is calculated per 8.2.10 (a). • No increases of capacity are considered for sections or loads close to supports. • If “beam torsion” is selected, torsion design is also performed (see “Section 8.3 Beam Torsion Design” on page 550). Maximum shear capacity is reduced by section 8.3.3. If torsion reinforcement is required, then Section 8.3.4(b) is used to define the extra transverse and longitudinal reinforcement required in addition to any other reinforcement.

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Chapter 60 • The stirrup spacing is no longer multiplied by 0.8 when the hook is in tension zone as Section 8.2.12.4 of the former AS 3600-2001 Specification was deleted in the current version (AS 3600-2009).

60.6.9 Section 8.3 Beam Torsion Design • Section 8.3 is followed. • Torsion reinforcement is not provided if the requirements of 8.3.4(a)(i) are met [T* < 0.25 φ Tuc]. The requirements of 8.3.4(a)(ii) and (iii) are conservatively ignored. • All torsion is assumed to be taken by the “core”. See “Concrete “Core” Determination” on page 405 for calculation of the core. • Where the core consists of multiple ribs, the calculations are based on an average rib (and then factored up by the number of ribs). • Section 8.3.3 is used to reduce the maximum shear capacity. • In calculating At and ut, the side cover to the centroid of the longitudinal bar is assumed to be the maximum of the top cover and bottom cover to the centroid of their respective longitudinal bars. • Longitudinal torsion reinforcement in the compression zone is not reduced by the flexural compression force [8.3.6(a) is used for both tension and compression faces] • Torsion capacity is reported. • Section 8.3.4(b) is considered when designing the transverse closed ties. • Transverse closed ties (Asw) are provided for the lesser of T* and Tu,max. If T* is greater than Tu,max, then the section will be reported as failing sections 8.2 and 8.3. The minimum requirements of 8.3.7(b) are also met. • Longitudinal reinforcement is provided based on the Asw value calculated for the lesser of T* and Tu,max. • Closed tie spacings are reduced by a factor of 0.8 per 8.2.12.4(c), even if the cross section is in pure torsion (no shear).

60.6.10 Section 8.6.1 RC Beam Crack Control If there are no tension stresses in the cross section, no reinforcement is provided. The cross section is considered as a “tension member” if both faces are in tension based on gross section stresses for the cross section forces being considered. (The code uses the term “primarily tension”.). User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. Section (a) - This section is not implemented here. Clause 8.1.6.1 is implemented in the minimum reinforcement design. Section (b) – This section is always used in the service design, but never used in the max service design. • Reinforcement is added on each face in tension to limit maximum spacing to 300 mm. All bars on the appropriate face (including fractional components for bars at an angle to the cross section) are considered for spacing requirements. A fractional number of bars and spaces may be used. • Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. Section (c) – This section is used if the cross section is a tension member and the environment is not protected. • For the service design: • Reinforcement is added both faces to keep the reinforcement stresses within the limits of Table 8.6.1(A). • The maximum diameter of all reinforcement assigned to a particular face is used in Table 8.6.1(A). • For the max service design: • Reinforcement is added both faces to keep the reinforcement stresses less than 0.8 fsy. 550

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Chapter 60 Section (d) – This section is used if the cross section is not a tension member and the environment is not protected. • For the service design: • Reinforcement is added both faces to keep the reinforcement stresses within the limits of Table 8.6.1(A) or Table 8.6.1(B), whichever is larger. • The maximum diameter of all reinforcement assigned to a particular face is used in Table 8.6.1(A). • The bar spacing for Table 8.6.1(B) is calculated using all bars on the appropriate face (including fractional components for bars at an angle to the cross section). Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. A fractional number of bars and number of spaces may be used. • For the max service design: • Reinforcement is added to both faces to keep the reinforcement stresses less than 0.8 fsy.

60.6.11 Section 8.6.2 PT Beam Crack Control • If the tensile stress in the concrete does not exceed 0.25 f′c then there is no need for crack control reinforcement and none of the following applies. • Section (a) with the 0.6 f′c limit is ignored because it does not give any guidance on how much reinforcement is necessary. Section (b) is always used instead. • Reinforcement is added to try to keep mild steel stress changes on the tension face within the values given in Table 8.6.2 as the moment changes from decompression to service level. • In extremely rare circumstances (where the service reinforcement stress in compression, even though the concrete stress exceeds 0.25 f′c ) this criterion is skipped as adding reinforcement will reduce the compression (increase the tension) making it impossible to satisfy the criterion by increasing the reinforcement. • The decompression reinforcement stress is calculated using gross section strains, while the service reinforcement stress is calculated using cracked section strains. • Reinforcement is also added if necessary to provide a centre-to-centre reinforcement spacing of 300 mm or less. • For this requirement, each bonded tendon duct that is in the tension zone (based on gross-section stresses) is considered to be equivalent to a single mild steel bar (even if it is far from the tension face). In the spacing calculation, all effective tendon ducts are assumed to be optimally positioned to minimize the number of mild steel bars required – the plan layout of the ducts is ignored. • A fractional number of bars and number of spaces may be specified to meet the spacing requirement. • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

60.6.12 Section 9.1 Strength of Slabs in Bending • Section 8.1 is used for calculating the bending strength of slabs. Any reinforcement required is reported as being due to 8.1. See “Section 8.1 Strength of Beams in Bending” above for details on the 8.1 implementation.

60.6.13 Section 9.4.1 RC Slab Crack Control User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. Section (a) –This section is not implemented here. Clause 9.1.1 is implemented in the minimum reinforcement design via clause 8.1.6.1. Section (b) – This section is always used in the service design, but never used in the max service design.

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Chapter 60 • Reinforcement is added to limit maximum spacing to 300 mm or two times the cross section depth. All bars on the appropriate face (including fractional components for bars at an angle to the cross section) are considered for spacing requirements. A fraction number of bars and number of spaces may be used. • Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. Section (c) – This section is only used for service design, but is not used in protected environments. • Reinforcement is added both faces to keep the reinforcement stresses within the limits of Table 9.4.1(A) or Table 9.4.1(B), whichever is larger. • The maximum diameter of all reinforcement assigned to a particular face is used in Table 9.4.1(A). • The bar spacing for Table 9.4.1(B) is calculated using all bars on the appropriate face (including fractional components for bars at an angle to the cross section). Bars with a diameter of less than half the diameter of the maximum bar diameter on the face being considered are converted to an equivalent number of hypothetical bars with a diameter of half the maximum bar diameter. This conversion is based upon area. A fractional number of bars and number of spaces may be used. Section (d) – This section is only used for max service design, but is not used in protected environments. • Reinforcement is added to both faces to keep the reinforcement stresses less than 0.8 fsy.

60.6.14 Section 9.4.2 PT Slab Crack Control • If the tensile stress in the concrete does not exceed 0.25 f′c then there is no need for crack control reinforcement and none of the following applies. • Section (a) with the 0.6 f ′c limit is ignored because it does not give any guidance on how much reinforcement is necessary. Section (b) is always used instead. • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. • Reinforcement is added to try to keep mild steel stress changes on the tension face within the values given in Table 9.4.2 as the moment changes from decompression to service level. In extremely rare circumstances (where the service reinforcement stress in compression, even though the concrete stress exceeds 0.25 f′c ) this criterion is skipped. • The decompression reinforcement stress is calculated by determining gross section decompression cross-section strains and applying the strains to the reinforcement. • Reinforcement is also added if necessary to provide a centre-to-centre reinforcement spacing not exceeding 300 mm or two times the cross section depth. For this requirement, each bonded tendon duct (that is in the tension zone based on gross section stresses) is considered to be equivalent to a single mild steel bar (even if it is far from the tension face). In the spacing calculation, all bonded tendon ducts are assumed to be optimally positioned to minimize the number of mild steel bars required. A fractional number of bars and number of spaces may be specified to meet the spacing requirement.

60.6.15 Section 9.4.3.2 Shrinkage and Temperature • This criterion is applied as part of the minimum reinforcement designer as it is independent of the magnitude of forces upon a cross section. • This criterion is applied to both beams and slabs, although its application to beams is not required by AS 3600. • The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. • Reinforcement may be applied to both faces if the cross section is subject to both positive and negative moments and the “tension face” reinforcement location is chosen. • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. • The amount of reinforcement provided is equal to 0.75 (per 9.4.3.2(b)) times the amount specified by either 9.4.3.4(a)(i), 9.4.3.4(b)(i), or 9.4.3.4(c). 552

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Chapter 60 • For “protected” environments, the amount of reinforcement provided is: A s = (0.75)(1.75 – 2.5 σcp)(Ag)/1000 • For “normal” environments, the amount of reinforcement provided is: A s = (0.75)(3.5 – 2.5 σcp)(Ag)/1000 • For “corrosive” or “very corrosive” environments, the amount of reinforcement provided is: As = (0.75)(6.0 – 2.5 σcp)(Ag)/1000 • For non-PT design strips and design sections, σcp is taken as zero.

60.6.16 Punching Shear Design Refer to Chapter 66, “Punching Shear Design Notes” (no change with respect tot he former code).

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Chapter 60

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Chapter 61

61 BS 8110: 1997 Design This chapter details RAM Concept’s implementation of BS8110: 1997 and Technical Report 43 (known as TR 43). The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules

61.1 BS 8110 / TR 43 default loadings This section provides information on the loadings that RAM Concept creates by default when you start a new BS 8110 file. As the purpose and use of most of the loadings are self-explanatory, only items that are particularly noteworthy are discussed here.

61.1.1 Default Pattern Loading Factors To fulfill the requirements of considering “Adverse” and “Beneficial” loadings required in code section 2.4.3.1, RAM Concept uses pattern loading factors. For dead loadings, RAM Concept uses pattern factors of 1.0 and 1.0/1.4, or 0.71. For live loadings, RAM Concept uses Pattern factors of 1.0 and 0. See “About load pattern” on page 36 for further information. The applied dead load pattern factors have the side effect that the self-weight is patterned in the Initial Service LC which can cause conservative calculations for the Initial Service Design. If problems are experienced with this design, a separate model and investigation can be used without the dead load pattern factors to investigate the Initial Service Design.


61.2 BS 8110 / TR 43 Default Load Combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new BS 8110 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from BS8110-1: 1997, unless noted otherwise.


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Chapter 61




61.2.3 Service LC: D + L + S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

61.2.4 Ultimate LC: 1.4D + 1.6L + 1.6S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.4 (std) & 1.0 (alt) Live Loading: 1.6 (std) & 0.0 (alt) Snow Loading: 1.6 (std) & 0.0 (alt)

61.2.5 Service Wind LC: D + L + S + W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat / raft foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std & alt) Snow Loading: 1.0 (std & alt) Service Wind Loading: 1.0 (std & alt)

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Chapter 61

61.2.6 Service Wind LC: D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat / raft foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Service Wind Loading: 1.0 (std & alt)

61.2.7 Ultimate Wind LC: 1.2D + 1.2L + 1.2S + 1.2W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std & alt) Live Loading: 1.2 (std & alt) Snow Loading: 1.2 (std & alt) Service Wind Loading: 1.2 (std & alt)

61.2.8 Ultimate Wind LC: D + 1.4W This load combination is intended for checking the strength limit state with applied wind loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.0 (std) & 1.4 (alt) Service Wind Loading: 1.4 (std & alt)

61.2.9 Accident LC This load combination is intended to fulfill the requirements of code section 2.4.3.2 and TR 43 section 6.10.4. The load factors used are: Dead Loading: 1.05 (std) and 1.0 (alt) Live Loading: 0.35 (std) (this is 1.05/3) and 0.0 (alt) This load combination is used by the Accident Design Rule Set.

61.2.10 Sustained Service LC This load combination is intended for use in load history deflection calculations. For the purpose of this load combination, 100% of the Live (Storage) Loading and 50% of all other live loading is assumed to be permanent loading. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std & alt) Live (Unreducible) Loading: 0.5 (std & alt)

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Chapter 61 Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 0.5 (std & alt) Live (Roof) Loading: 0.5 (std & alt)

61.3 BS 8110 / BS 6399-1 live load factors It is recommended that, in order to get the appropriate factors, you draw: • assembly loads on a Live (Unreducible) layer

61.4 BS 8110/TR43 material behaviours This section explains how RAM Concept models the concrete, non-prestressed reinforcement and prestressed reinforcement when using BS 8110 / TR 43.

61.4.1 Concrete Behaviour This elastic modulus of concrete is defined by the user in the materials window. The user can choose to use the code equation of BS8110 Figure 2.1, an equation from another code, or a specified value. When values are directly specified, two elastic modulus values must be specified: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions When the BS 8110 code equation is selected the following values are used: E ci = 5500 ( f cui ⁄ 1.5 ) E c = 5500 ( f cu ⁄ 1.5 ) Where fcui = cube strength at stressing fcu = 28 day cube strength For calculations based on the “concrete section”, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses four different stress strain curves are used. All four stress-strain curves are paraboliclinear curves as detailed in. The transition strain from the parabolic to the linear curve is at 2fc/Ec, where fc is the peak stress and Ec is the elastic modulus at zero strain. For initial stress conditions, the peak stress in the stress strain curve is 0.67fcui . For service stress conditions, the peak stress in the stress-strain curve is 0.67fcu. For strength conditions, the peak stress in the stress-strain curve is

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Chapter 61 0.67fcu / 1.5 For accident (localised damage) strength conditions, the peak stress in the stress-strain curve is 0.67fcu / 1.3. The strength stress-strain curves are truncated at a strain of 0.0035. The other stress-strain curves have no limit strain. For ECR calculations, the maximum tension stress in concrete is assumed to be 0.6 f cu . For service design crack width calculations and for service design cracked stress analyses, a tension stiffened concrete stress strain curve is used:

Use of this curve is similar, but not technically equivalent, to the provisions of BS 8110-2:1985 Figure 3.1. A comparison of the stress diagrams for the Code provision and the Concept implementation are shown below:

Figure 3.1 provision

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Chapter 61 Concept implementation Since Concept’s crack width design does a cracked stress analysis (with a non tension stiffened concrete stress strain curve) for the 0.8 fy provision, the concrete and rebar stress results for members on which a crack width design is done will represent the range of results between the tension stiffened and the non tension stiffened concrete stress strain curve. Concrete and rebar stress results for all other members will represent use the tension stiffened concrete stress strain curve only.

61.4.2 (Untensioned) Reinforcement Behaviour Untensioned reinforcement is modeled as a perfectly elastic/plastic material, as is shown in code figure 2.2. The elastic modulus is that specified by the user in the materials window instead of the code-specified 200,000 N/mm2. For strength considerations, a γ m of 1.05 is used (Amendment 1 and 2). For strength considerations, a γ m of 1.15 is used (Amendment 3). For all other considerations (including accident strength) a γ m of 1.0 is used.

61.4.3 Bonded Prestressed Reinforcement Behaviour Prestressed reinforcement is modeled as using a power formula. The curve is defined by four parameters: Eps = the elastic modulus at zero strain (from materials window) Fpy = the “yield” stress of the reinforcement (from materials window) Fpu = the ultimate stress of the reinforcement (from materials window) γ m = partial safety factor for materials These four parameters are used to calculate the three parameters needed for the power formula, as described in Chapter 51, “Section Design Notes”. The three parameters are: E ps' = E ps F py' = F py ⁄ γm F pu' = F pu ⁄ γm For strength considerations, a γ m of 1.05 is used (Amendment 1 and 2). For strength considerations, a γ m of 1.15 is used (Amendment 3). For all other considerations (including accident strength) a γ m of 1.0 is used.

61.4.4 Unbonded Prestressed Reinforcement Behaviour For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For “accident” strength conditions, RAM Concept assumes that unbonded tendons have no stress. For ultimate resistance moment calculations, RAM Concept's general approach to unbonded tendon stress-strain curves is detailed in Chapter 51, “Section Design Notes”. For BS 8110-1997, the maximum unbonded tendon stress (fpb, called flimit in Chapter 51, “Section Design Notes”) is defined by equation 52 and 0.7fpu.

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Chapter 61 When equation 52 is used in a cross section that contains multiple tendons, the following terms are used in the calculation: l / d = length of an individual tendon divided by its depth fpu Aps = sum of all the individual tendons' fpu multiplied by the vector component of their Aps. fcu bd = minimum concrete cube strength multiplied by the compression face width and the depth to the centroid of the vector component tendon area For BS 8110: 1997, the value used as a strain reduction factor for unbonded tendons is: k = 5d / L where L = length of the unbonded tendon. d = depth of the post-tensioning tendon (measured from furthest concrete face) This is equivalent to assuming a neutral axis depth of 0.5 d and “zone of inelasticity” of ten times this length [see BS 8110 code text that accompanies equation 52]. In equation 52, RAM Concept needs to determine “d” and “b”. RAM Concept assumes that each tendon is placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section). This assumption typically has no impact on the ultimate stress in the tendon as when the tendon is on the “wrong” side of the cross section centroid, the stress in the tendon is less than fpb, due to the small tension strains (possibly compression strains) in the cross section at the tendon elevation. The tendon length “l” in equation 52 is (conservatively) not modified to assume multiple simultaneous inelastic zones.

61.5 BS 8110 / TR 43 code rule selection The following explains how RAM Concept decides which BS 8110 / TR 43 code rules to apply based on the design strip segment or design section properties, combined with the active design rules for the rule set under consideration.


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RC

PT - bonded tendons

PT - unbonded tendons

Beam

3.12.5, 3.12.11.2.4

4.12.2

3.12.5, 3.12.11.2.4, 4.12.2, TR43/6.10.6

One-Way Slab

3.12.5, 3.12.11.2.7

4.12.2

3.12.5, 3.12.11.2.7, 4.12.2, TR43 / 6.10.6

Two-Way Slab

3.12.5, 3.12.11.2.7

TR43 / 6.10.6

TR43 / 6.10.6







61.5.3 Initial Service (“Transfer”) • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC).

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RC

PT

Beam

(none)

4.3.5.1 4.3.5.2

One-Way Slab

(none)

4.3.5.1 4.3.5.2

Two-Way Slab

(none)

4.3.5.1 4.3.5.2


61.5.4 Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • The design strip segment or design section property “Environment” is used to determine the class of post-tensioned members as follows: Protected: Class 3 (0.2 mm crack) Normal: Class 3 (0.1 mm crack) Corrosive: Class 2 Very Corrosive: Class 1 • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

3.12.11.2.1

3.12.11.2.1 4.3.4.2 4.3.4.3 / TR 43

One-Way Slab

3.12.11.2.1

3.12.11.2.1 4.3.4.2 4.3.4.3 / TR 43

Two-Way Slab

3.12.11.2.1

4.3.4.2 4.3.4.3 / TR 43


61.5.5 Strength • Tendons are considered as an internal section force (and the hyperstatic loading is assumed to be included in the load factors). RAM Concept

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Chapter 61 • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • See “Torsion Considerations” on page 405 for how torsion is implemented. • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

3.4.4

4.3.7

3.4.5

4.3.8

3.4.5.13*

4.3.9*

3.4.4

4.3.7

3.4.5

4.4.1 / 4.3.8

3.4.5.13*

4.3.9*

3.4.4

4.3.7

3.4.5

4.4.1 / 4.3.8

3.4.5.13*

4.3.9*

One-Way Slab

Two-Way Slab


Note: * - 3.4.5.13 and 4.3.9 are applied only if “beam” torsion is selected (see torsion design notes) 61.5.6 Ductility • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The longitudinal reinforcement from all other designs (except other ductility) is considered to be in place before ductility reinforcement is added. • The bending moments sign (or signs) is determined by the moment envelope for the rule set layer (ductility could be required for both positive and negative moments). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

3.2.2.1

4.2.3.1

One-Way Slab

3.2.2.1

4.2.3.1

Two-Way Slab

3.2.2.1

4.2.3.1


61.5.7 Accident • Strength calculations in accordance with code sections 2.4.3.2, 2.4.4.2 and TR 43 section 6.10.4 are performed if appropriate. • Unbonded post-tensioning tendons are assumed to have zero stress. • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces).

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Chapter 61 • Reduced γ m factors are used in the strength calculations. For concrete in flexure, γ m = 1.3 and for reinforcement, γm = 1.0. Note that for shear reinforcement calculations, the “0.95fyv“ (Amendment 1 and 2) or “0.87fyv“ (Amendment 3) values are changed to “1.0fyv”. • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

(none)

4.3.7 4.3.8 4.3.9* (reduced γ m )

One-Way Slab

(none)

4.3.7 4.3.8 4.3.9* (reduced γ m )

Two-Way Slab

(none)

(none)

Table 61-6 Accident rule mapping

Note: * - 4.3.9 is applied only if “beam” torsion is selected (see torsion design notes)

61.6 BS8110 / TR43 code implementation

61.6.1 Section 3.2.2.1 Redistribution of moments (Ductility Check) Included code sections - 3.2.2.1 (item b). Excluded code sections - 3.2.2.1 (rest). RAM Concept does not currently redistribute moments, but applies “Condition 2” as a limit to the neutral axis depth, thereby ensuring ductility. The neutral axis depth is limited to 0.6 times the effective depth.

61.6.2 Section 3.4.4 Design resistance moment of beams Included code sections - 3.4.4.1. Excluded code sections - 3.4.4.2 through 3.4.4.5 (these are optional simplifications of section 3.4.4.1). Items a, b, c, d and e of section 3.4.4.1 are followed. The optional 0.1fcu clause at the end of section 3.4.4.1 is not followed Strain compatibility design is used. The maximum compressive strain is 0.0035. The simplified stress block of Figure 3.3 is not used. See the Materials section for the material stress strain curves ( γ m = 1.5 for concrete; γm = 1.05 for reinforcement (Amendment 1 and 2), γ m = 1.15 for reinforcement (Amendment 3)). Reinforcement areas are not deducted from the concrete area. Post-tensioning Tendon forces are ignored. For cross sections with multiple concrete mixes, the stress-strain curve of each concrete block is used appropriately.

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Chapter 61 Axial forces (loads) on the section are either considered or ignored based on the settings in the design section or design span under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design span properties) is necessary to ensure a safe design. RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See Ductility in the previous section for applying ductility requirements. For cross sections with very small moments, the amount of reinforcement calculated by RAM Concept may exceed the amount necessary. This is because RAM Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement RAM Concept selects is that necessary for axial force equilibrium in the cross section.

61.6.3 Section 3.4.5 Design shear resistance of beams Included code sections - 3.4.5.1 to 3.4.5.4, 3.4.5.5 (partial), 3.4.5.12 Excluded code sections - 3.4.5.5 (partial), 3.4.5.6 - 3.4.5.11, 3.4.5.13 (considered separately) See “Concrete “Core” Determination” on page 405 for calculation of bv. vc is calculated per Note 2 of Table 3.8, including the fcu modifier term. Longitudinal reinforcement designed by Minimum, Service and Strength designers is considered in the determination of As used in the calculation of vc. 100As / bvd is taken as 0.15 minimum, to follow the “=0.15” in table 3.8. For cross sections with multiple concrete mixes, the minimum fcu is used. The effective depth is determined by a cracked section analysis using the bending moment and axial force in place at time of the shear being investigated. If all of the reinforcement in the cross section is in compression, then the effective depth is calculated as the distance from the compression-most face to the furthest active reinforcement (in this case 100As / bvd is taken as 0.15). vc’ is calculated as the minimum of Equation 6a and Equation 6b, but never less than zero. fyv is limited to 460 N/mm2 (Amendment 1 and 2) or 500 N/mm2 (Amendment 3). Links are provided per Table 3.7 Links are only provided in the regions required by calculation, not the whole length of the beam. Maximum allowed shear stress is the smaller of 5 N/mm2 and 0.8 f cu . Spacing of links along the span is 0.75 d. The spacing across the span is not considered. Bent up bars and regions close to supports are not considered. Bottom loaded beams are not considered. The anchorage of longitudinal bars is not checked. Net axial forces are considered if the “Consider Net Axial…” checkbox is checked.

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61.6.4 Section 3.4.5.13 Torsion Included code sections - 2.4.1, 2.4.2, 2.4.4 (part) to 2.4.8 Excluded code sections - 2.4.3, 2.4.4 (part), 2.4.9, 2.4.10

Note: All code references in this section refer to BS 8110, Part 2 Only the “core” of a cross section is used for torsion design. See “Concrete “Core” Determination” on page 405. Torsional shear stress vt is calculated using section 2.4.4.1 equation 2. Maximum combined shear stress vtu is calculated by Table 2.3, note 2 including the y1 modification factor and compared to vt. Any remaining capacity is used to calculate maximum remaining shear capacity. Shear and torsion reinforcement is provided in accordance with Table 2.4. Area of torsion links and longitudinal reinforcement is calculated in accordance with section 2.4.7. Maximum spacing of links is the least of x1, y1 /2 or 200 mm. If torsion design is selected, at least minimum links will be provided at all locations.

Note: Assume γ in equations in table 2.3, note 2 is a misprint, and should instead be . 61.6.5 Section 3.5.4 Resistance moment of solid slabs Included code sections - 3.5.4 Excluded code sections - none See section 3.4.4 for additional details.

61.6.6 Section 3.5.5 Shear resistance of solid slabs Included code sections - 3.5.5.1 to 3.5.5.3 Excluded code sections - none Section 3.4.5 for is used to determine the shear resistance of solid slabs, except that Table 3.16 (with bv determined using the “shear core”) is used in place of Table 3.7.

61.6.7 Section 3.12.5 Minimum areas of reinforcement in members

Note: This section is not used for post-tensioned members that are primarily bonded. Refer to “Determination of Bonded vs. Unbonded Cross Sections” on page 570 for discussion. Included code sections - 3.12.5.1 through 3.12.5.3 Excluded code sections - 3.12.5.4 Reinforcement is provided per Table 3.25, assuming that sections are rectangular and subject to flexure. Reinforcement is provided such that: 2

A s f y ≥ ( 0.0013 ) ( 460N ⁄ mm )A c 2

A s f y ≥ ( 0.0013 ) ( 500N ⁄ mm )A c

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Chapter 61 A s ≥ ( 0.0013 )A c For sections that are not declared as post-tensioned, all post-tensioned reinforcement is ignored. For post-tensioned beams and post-tensioned one-way slabs, bonded post-tensioning that is on the tension-most side of the cross section centroid, or is within 10% of the cross section depth of the centroid elevation, is considered to be equivalent to un-tensioned 460 N/mm2 reinforcement for Amendment 1 and 2, and 500 N/mm2 reinforcement for Amendment 3, and will reduce the amount of un-tensioned reinforcement necessary. Bonded tendons at an angle to the cross section will have vector components of their reinforcement areas considered toward the requirement. This interpretation is somewhat more conservative than a literal reading of the code requirements. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

Note: This section is never used for post-tensioned two-way slabs. 61.6.8 Section 3.12.11.2.1 Bar spacing For all RC structures, and PT beams and one-way slabs, crack checks are performed per Part 2, 3.8.2 and crack widths are limited to 0.3 mm. This crack width design supersedes the other requirements in this section. RAM Concept’s implementation of the crack width calculations are detailed in “Part 2, Section 3.8.3”. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations.

61.6.9 Section 3.12.11.2.4 Beam Bar spacing

Note: This section is not used for post-tensioned beams that are primarily bonded. Refer to “Determination of Bonded vs. Unbonded Cross Sections” on page 570 for discussion. In beams, the clear distance between bars is limited to 300 mm. This code section is applied even though it is not required as crack widths are controlled per 3.12.11.2.1. In post-tensioned beams, bonded (grouted) post-tensioning ducts that are on the tension side of the cross section centroid, or are within 10% of the cross section depth of the centroid elevation are considered as equivalent to an un-tensioned bar. These ducts are assumed to be optimally placed for spacing purposes - their plan locations are ignored. This implementation is somewhat more conservative than a literal reading of the code requirements. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations.

61.6.10 Section 3.12.11.2.7 Slab Bar spacing

Note: This section is not used for post-tensioned slabs that are primarily bonded. Refer to “Determination of Bonded vs. Unbonded Cross Sections” on page 570 for discussion. In RC slabs and PT one-way slabs, the clear distance between bars is limited to the smaller of 750 mm or 3 d. This code section is applied even though it is not required as crack widths are controlled per 3.12.11.2.1. In one-way slabs, bonded (grouted) post-tensioning ducts that are on the tension side of the cross section centroid, or are within 10% of the cross section depth of the centroid elevation are considered as equivalent to an un-tensioned bar. These ducts are assumed to be optimally placed for spacing purposes - their plan locations are ignored. This implementation is somewhat more conservative than a literal reading of the code requirements.

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Chapter 61 User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations.

61.6.11 Section 4.2.3.1 Redistribution of Moments (Ductility Check) RAM Concept does not currently redistribute moments, but applies item “c” as a limit to the neutral axis depth, thereby ensuring ductility. The neutral axis depth is limited to 0.5 times the effective depth.

61.6.12 Section 4.3.4.2 Compressive stresses in concrete For beams and one-way slabs, compressive stresses in concrete, based on the concrete section, are limited to 0.33fcu. The increase to 0.40fcu for certain portions of continuous members is not implemented. For beams and one-way slabs, compressive stresses in concrete, based on the concrete sections, at the concrete section centroid are limited to 0.25fcu. Two-way slab compressive stresses in concrete, based on the concrete sections, at the concrete section centroid are limited to 0.24fcu in the support zone and 0.33fcu in the span zone [TR 43 Table 2]. For sections with multiple concrete mixes, the minimum fcu is used to determine the limit stress and the peak stress reported may be approximate. No check is made to ensure the cross section is post-tensioned.

Note: Assume the

in TR 43 table 2 for compressive stresses is a misprint.

61.6.13 Section 4.3.4.3 Flexural tension stresses in concrete The interaction of the BS 8110 requirements, the TR 43 requirements, the different classes and the use of bonded and unbonded tendons makes describing the service tensile stress limits and requirements in text form very confusing. In some circumstances, BS 8110 and TR 43 conflict, while in other circumstances neither one explicitly considers a particular configuration. Our implementation of these requirements is detailed in the table below. For each combination of tendon type, structure type and class, two limit stresses and a reinforcement calculation are listed. The first limit stress is the maximum stress allowed if no supplemental un-tensioned reinforcement is used. The second limit stress is the absolute maximum stress allowed. The reinforcement calculation details how to calculate the required supplemental reinforcement when stresses exceed the first stress limit.

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Tendons Member Type

Class

Tension limit Absolute without sup- tension plementary limit reinforcement

Reinforcement calculation

Bonded

Beam

1

0

0

4.3.4.3 (c)

Bonded

Beam

2

0.36 f cu

0.36 f cu

4.3.4.3 (c)

Bonded

Beam

3 / 0.1 mm Tables 4.2 / 4.3 0.25fcu

4.3.4.3 (c)

Bonded

Beam

3 / 0.2 mm Tables 4.2 / 4.3 0.25fcu

4.3.4.3 (c)

Bonded

One-way

1

0

0

4.3.4.3 (c)

Bonded

One-way

2

0.36 f cu

0.36 f cu

4.3.4.3 (c)

Bonded

One-way

3 / 0.1 mm Tables 4.2 / 4.3 0.25fcu

4.3.4.3 (c)

Bonded

One-way

3 / 0.2 mm Tables 4.2 / 4.3 0.25fcu

4.3.4.3 (c)

Bonded

Two-way

All

TR 43 Table 2

TR 43 Table 2 TR 43, 6.10.5

Unbonded Beam

1

0

0

TR 43, 6.10.5

Unbonded Beam

2

0

0.36 f cu

TR 43, 6.10.5

Unbonded Beam

3 / 0.1 mm 0

Tables 4.2 / 4.3*

TR 43, 6.10.5

Unbonded Beam

3 / 0.2 mm 0

Tables 4.2 / 4.3*

TR 43, 6.10.5

Unbonded One-way

1

0

0

TR 43, 6.10.5

Unbonded One-way

2

0

0.36 f cu

TR 43, 6.10.5

Unbonded One-way

3 / 0.1 mm 0

Tables 4.2 / 4.3*

TR 43, 6.10.5

Unbonded One-way

3 / 0.2 mm 0

Tables 4.2 / 4.3*

TR 43, 6.10.5

Unbonded Two-way

All

TR 43 Table 2 TR 43, 6.10.5

TR 43 Table 2

Table 61-7 Flexural tension limit rule mapping

Note: * - When Tables 4.2/4.3 are used with unbonded tendons, the values for “grouted post-tensioned tendons” and a 0.1mm crack width are used.

61.6.14 Determination of Bonded vs. Unbonded Cross Sections For the purposes of this section, a cross section is considered as being “with bonded tendons” if the majority of the tendons in the cross section (based on vector-component areas) are bonded. Cross sections that do not qualify as “with bonded tendons” are considered as being “with unbonded tendons”. A cross section without tendons is therefore considered as being “with unbonded tendons”.

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61.6.15 Calculation of Supplemental Untensioned Reinforcement Supplemental reinforcement is calculated when the “unreinforced” stress limits are exceeded, even for the structure types and classes where it is not anticipated by BS 8110. For example, if a class 1 beam has tension stresses exceeding 0 N/mm2, it will be marked as having failed the 4.3.4.3 criterion; supplemental reinforcement will still be calculated for the class 1 beam even though the reinforcement cannot solve the failure.

61.6.16 Calculation of Supplemental Reinforcement Per 4.3.4.3(c) The calculation of supplemental reinforcement per 4.3.4.3(c) is as follows: Stress Difference = Actual Stress - Supplemental Reinforcement Limit Stress As = Act [(Stress Difference) / (400 N/mm2)] where Act = cross-sectional area of the concrete in the tension zone User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

61.6.17 Calculation of Supplemental Reinforcement Per TR 43, 6.10.5 0.625A sfy = F1 for support regions of two-way slabs 0.625(Asfy + Apsfp) = F1 for span regions of two-way slabs 0.625(Asfy + Apsfp) = F1 for all regions of beams and one-way slabs where F1 = tensile force in concrete As = area of un-tensioned reinforcement added fy = yield strength of un-tensioned reinforcement Aps = vector component area of bonded (grouted) tendons in tension zone fp = tendon yield stress - tendon effective stress It is possible that the added un-tensioned reinforcement will not be in the tension zone if a very large concrete cover is specified.

Note: For span regions of two-way slabs, and all regions of one-way slabs, this implementation is somewhat different from a literal code interpretation as it considers the possibility of a mix of bonded and unbonded tendons in a cross section. It also may require additional un-tensioned reinforcement for a cross section with bonded tendons, which the code does not require. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. For sections with multiple concrete mixes, the minimum fcu is used to determine the limit stresses and the peak stress reported may be approximate. No check is made to ensure the cross section is post-tensioned.

61.6.18 Section 4.3.5.1 Design compressive stresses (Transfer) For beams and one-way slabs, compressive stresses in concrete, based on the concrete section, are limited to 0.5fci.

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Chapter 61 For beams and one-way slabs, compressive stresses in concrete, based on the concrete sections, at the concrete section centroid are limited to 0.4fci. For two-way slabs, compressive stresses in concrete, based on the concrete section, are limited to 0.24fci in the support region and 0.33fci in the span region [TR 43, 6.10.2]. For sections with multiple concrete mixes, the minimum fci is used to determine the limit stress and the peak stress reported may be approximate. No check is made to ensure the cross section is post-tensioned

Note: Assume the

in TR 43 table 2 for compressive stresses is a misprint.

61.6.19 Section 4.3.5.2 Design tensile stresses in flexure (Transfer) For beams and one-way slabs, tensile stresses in concrete, based on the concrete section, are limited to: Class 1: 1 N/mm2 Class 2: 0.36 f ci . Class 3: 0.36 f ci . For Class 2 and 3 beams and one-way slabs, where the stresses above are exceeded, bonded reinforcement is provided as follows [TR 43, 6.10.2/6.10.5]: As = Fi / (0.625fy) For two-way slabs without supplemental untensioned reinforcement, tensile stresses in concrete, based on the concrete section, are limited to 0 in the support region and 0.15 f ci in the span region [TR 43, 6.10.2]. For two-way slabs with supplemental untensioned reinforcement, tensile stresses in concrete, based on the concrete section, are limited to 0.45 f ci . Bonded reinforcement is provided as follows [TR 43, 6.10.2/6.10.5]: As = Fi / (0.625fy) For sections with multiple concrete mixes, the minimum fci is used to determine the limit stress and the peak stress reported may be approximate. No check is made to ensure the cross section is post-tensioned. Two way slabs can never exceed 0.45 f ci , while there is no limit for beam and one-way slabs that are class 2 or 3.

Note: Clause 4.3.5.2 is unclear on this stress limit for Class 2, as it states that additional reinforcement should be provided “if necessary”. This is interpreted as reinforcement is only necessary if the tensile stress exceeds 0.36 f ci (since this stress is less than the cracking stress). Hence the stress may exceed this limit if the additional reinforcement is provided.

61.6.20 Section 4.3.7 Ultimate limit state for beams in flexure Included code sections - 4.3.7.1, 4.2.7.2, 4.3.7.3 (partial) Excluded code sections - 4.3.7.3 (partial), 4.3.7.4 See section 3.4.4 for general approach. Note that if axial forces are included in the design (per the design span or design section setting), then the diversion of post-tensioning forces into supports will cause a hyperstatic (secondary) tension in many design sections, as is appropriate. Post-tensioning Tendons are included. See “Post-tensioning Material Stress-Strain Curves” on page 395 for tendon stressstrain curves. Bonded tendon strains are calculated using strain compatibility. 572

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Chapter 61 If a tendon is not perpendicular (in plan) to the cross section under consideration, then vector components of the cross section strains and the tendon stresses are used. Unbonded tendon stresses are calculated using a strain reduction factor approach (see detailed description in “Unbonded Post-tensioning Stress-Strain Curves –General Theory” on page 396). If tendon centroid is closer to the extreme compression fiber than the compression reinforcement, a solution may not be possible. Equation 51 and Table 4.4 are not used.

61.6.21 Section 4.3.8 Design shear resistance of beams Included code sections - 4.3.8.1 to 4.3.8.8, 4.3.8.10 Excluded code sections - 4.3.8.9 Vco is calculated per equation 54. The flange/web intersection is not checked. Vcr is calculated per equation 55 The value of Vc is used as shown in the following table. Moment

Vc Implementation

M < Mo

Vc = Vco Vc = (stress)bvh

M > Mo

Vc = min (Vco, Vcr)

and tension is on the Vc = (stress)bvh “tension” face * M > Mo

Vc = min (Vco, Vcr)

and no tension on the “tension” face *

Vc = (stress)bvh d = dt (assumed) As = 0 (none in “tension zone”) Aps = 0 (none in “tension zone”)

Table 61-8 Vc rule mapping

Note: * The calculation of Mo uses only 80% of the stress due to prestress. This can produce the rare case where the section is in reality uncracked and has a tension face different to that calculated with Mo. For the unusual case of M > Mo and the section is actually uncracked (when considering the full prestress force) the conservative assumptions of column four are made. “d” is defined as the depth to the centroid of the tension force in the tension zone (including rebar and post-tensioning). This is slightly different (and likely more rational) than the distance from the extreme compression fibre to the centroid of the tendons as defined in the code. “dt” is defined as the maximum depth to any longitudinal mild reinforcement, or the depth to the centroid of the tendons, whichever is greater. The vertical tendon force component is ignored. For sections with multiple concrete mixes, the minimum fcu is used in calculations.

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Chapter 61 Longitudinal reinforcement designed by Minimum, Service and Strength designers is considered in the determination of As used in the calculation of vc. bv is adjusted by considering any tendons in the shear core. The full width of unbonded tendons is deducted, and two-thirds of the width of bonded tendons is deducted from bv. For cross sections with multiple tendons, the fpu and fpe values used in the calculations are averaged. vc is calculated per Note 2 of Table 3.8, including the fcu modifier term, with (Aps + A s) used in place of As. See section 3.4.5 for detail of the implementation of this table. When unbonded tendons are used, the value of vc is reduced by a factor of 0.9 [TR 43, 6.11.1]. Shear reinforcement is calculated per 4.3.8.6 to 4.3.8.8. Link spacing is calculated per 4.3.8.10, with lateral spacing requirements ignored. The “web thickness” used in the calculations is the same as the shear core width - this may be incorrect if the core width is made up of multiple webs. In such cases, multiple design sections or design strips can be used; each containing only one web. Links are only provided in the regions required by calculation, not the whole length of the beam.

61.6.22 Section 4.3.9 Torsion See section 3.4.5.13 for details.

61.6.23 Section 4.4.1 / 4.3.8 Slabs (shear) One-way shear (not punching shear) design of prestressed slabs is calculated per section 4.3.8 with one exception. Links are not required unless V is greater than or equal to V c.

61.6.24 Section 4.12.2 Limitation on area of prestressing tendons Un-stressed reinforcement is added to provide an ultimate moment capacity greater than the cracking moment. The cracking is assumed to be top (hogging moment) or bottom (sagging moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. Only sections within 1/6 of the span length from supports or 1/6 of the span length from midspan are checked, as these are considered as the likely locations of first cracking of concrete. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment (note that the 1.2 factor is not used in BS 8110) The cracking stress is 0.6 f cu . For cross sections with multiple concrete mixes, the maximum fcu for the cross section is used.

61.6.25 Part 2, Section 3.8.3 Assessment of Crack Widths Un-tensioned reinforcement is added to ensure that the reinforcement stresses remain below 0.8fy. Crack widths are calculated per BS 8110 Part 2, equation 12. A concrete stress strain curve that approximates tension stiffening is used - see discussion on “Concrete Behaviour” on page 558. Creep is not considered. Un-tensioned reinforcement is added to keep crack widths at or below 0.3mm (per 3.2.4.2). This criterion is applied to two-way slabs, but equation 12 will not provide accurate crack width predictions for two way slabs when wide design strip segments or wide design sections are used.

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Chapter 61 The crack-limiting capabilities of appropriately placed bonded post-tensioning tendons are considered, and the balance loading will be considered if included in the load combinations. In determining the effectiveness of bonded tendons, equation 12 can be manipulated as follows: Crack width = (3acrεm) / [1+2(acr - cmin) / (h-x)] = εm s c sc = 3acr / [1+2(acr - cmin) / (h-x)] = crack spacing RAM Concept assumes the maximum crack spacing is 3(h-x). RAM Concept assumes that each bar and bonded tendon is placed horizontally to give the same crack spacing. Bars and tendons that - due to their elevation - cannot provide the crack spacing are ignored. sc = 3acr / [1+2(acr - cmin) / ht ] where ht = (h-x) = height of tension zone sc = 3acr ht / [ht +2(acr - cmin) ] sc [ht +2(acr - cmin) ] = 3acr ht sc ht +2scacr - 2sccmin = 3acr ht sc ht - 2sccmin = 3acr ht - 2scacr sc ht - 2sccmin = acr (3ht - 2sc) acr = (sc ht - 2sccmin) / (3ht - 2sc) However, a cr = 2

2

2

sb + c min , where sb = half the horizontal spacing between reinforcement

2

s b + c m in = ( s c h t – 2s c c m in ) ⁄ ( 3h t – 2sc ) 2

2

2

s b + c min = ( s c h t – 2s c c m in ) ⁄ ( 3h t – 2sc ) 2

2

2

s b = ( sc h t – 2s c c min ) ⁄ ( 3h t – 2s c ) – c m in sb =

2

2

2

2

( sc h t – 2s c c m in ) ⁄ ( 3h t – 2s c ) – c m in

2

Using this final equation, RAM Concept determines a spacing for each bar or bonded tendon that is effective in controlling cracking. RAM Concept iteratively determines the sc that gives the sbs that sum to the tension face width. For bonded tendons, the cover cmin is assumed to be the cover to the centroid of the tendon, and the “bar” diameter is assumed to be zero. Both of these assumptions are conservative.

61.6.26 TR 43 / Section 6.10.6 Minimum un-tensioned reinforcement

Note: This section is not used for post-tensioned beams or one-way slabs that are primarily bonded. Refer to “Determination of Bonded vs. Unbonded Cross Sections” on page 570 for discussion. For post-tensioned beams and one-way slabs the requirements of 3.12.5 and 3.12.11.2 are also applied. (Note that “Table 3.27” in TR 43 refers to the 1985 BS 8110 - this table has been renumbered 3.25 in the 1997 edition). This interpretation is somewhat more conservative than a literal reading of the code requirements. For post-tensioned two-way slabs with bonded or unbonded tendons, un-tensioned reinforcement is provided in support regions as follows: RAM Concept

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Chapter 61 As = 0.00075A c. For span segment strips, this criteria is only applied to the first cross section at a support if the span ratio is less than 0.2. For design sections, this criteria is applied when the span ratio is less than 0.2. The 300mm spacing requirement is not checked. The recommendations for slab edge reinforcement are not implemented. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

61.6.27 Punching shear design EC2 (EN 1992-2004) punching design is used instead of BS8110. Refer to Chapter 66, “Punching Shear Design Notes”.

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Chapter 62

62 IS 456 : 2000 / IS 1343 : 1980 Design This chapter details RAM Concept’s implementation of IS 456 : 2000 / IS 1343 : 1980. The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules

62.1 IS 456 / IS 1343 default loadings This section provides information on the loadings that RAM Concept creates by default when you start a new IS 456 file. As the purpose and use of most of the loadings are self-explanatory, only items that are particularly noteworthy are discussed here.


62.2 IS 456 Default Load Combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new IS 456 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from IS 456 : 2000 unless noted otherwise.



62.2.2 Initial Service LC This load combination is intended for checking requirements upon application of prestress. The load factors used are:

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Chapter 62 Balance Loading: 1.15 (std & alt) (this includes a 15% increase for long-term losses, which have normally not occurred at this stage)


62.2.3 Service LC: D + L + S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

62.2.4 Ultimate LC: 1.5D + 1.5L + 1.5S This load combination is intended for checking the strength limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.5 (std) & 1.0 (alt) Live Loading: 1.5 (std) & 0.0 (alt) Snow Loading: 1.5 (std) & 0.0 (alt)

62.2.5 Service Wind LC: D + 0.8L + 0.8S + 0.8W This load combination is intended for checking the serviceability limit state with applied wind and live loads. It is currently only generated for mat / raft foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 0.8 (std & alt) Snow Loading: 0.8 (std & alt) Service Wind Loading: 0.8 (std & alt)

62.2.6 Service Wind LC: D + W This load combination is intended for checking the serviceability limit state with applied wind loads. It is currently only generated for mat / raft foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Service Wind Loading: 1.0 (std & alt)

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62.2.7 Ultimate Wind LC: 1.2D + 1.2L + 1.2S + 1.2W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std & alt) Live Loading: 1.2 (std & alt) Snow Loading: 1.2 (std & alt) Service Wind Loading: 1.2 (std & alt)

62.2.8 Ultimate Wind LC: 0.9D + 1.5W This load combination is intended for checking the strength limit state with applied wind loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 0.9 (std) & 1.5 (alt) Service Wind Loading: 1.5 (std & alt)

62.2.9 Service Seismic LC: D + 0.8L + 0.2S + 0.8E This load combination is intended for checking the serviceability limit state with applied seismic and live loads. It is currently only generated for mat / raft foundations. Only the live load percentages specified in Table 8 of IS 1893 (Part 1): 2002 are applied. 25% of the Live (Unreducible) and Live (Reducible) loads are applied, and 50% of the Live (Storage) loads are applied. No Live (Roof) loads are applied. These percentages are incorporated into the following combinations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.2 (std & alt) [0.25(0.8)] Live (Reducible) Loading: 0.2 (std & alt) [0.25(0.8)] Live (Storage) Loading: 0.4 (std & alt) [0.5(0.8)] Live (Parking) Loading: 0.2 (std & alt) [0.25(0.8)] Snow Loading: 0.2 (std & alt) [0.25(0.8)] Service Seismic Loading: 0.8 (std & alt)

62.2.10 Service Seismic LC: D + E This load combination is intended for checking the serviceability limit state with applied seismic loads. It is currently only generated for mat / raft foundations. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Service Seismic Loading: 1.0 (std & alt)

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62.2.11 Ultimate Seismic LC: 1.2D + 1.2L + 0.3S + 1.2E This load combination is intended for checking the strength limit state with applied seismic and live loads. Only the live load percentages specified in Table 8 of IS 1893 (Part 1): 2002 are applied. 25% of the Live (Unreducible) and Live (Reducible) loads are applied, and 50% of the Live (Storage) loads are applied. No Live (Roof) loads are applied. These percentages are incorporated into the following combinations. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.2 (std & alt) Live (Reducible) Loading: 0.3 (std & alt) [0.25(1.2)] Live (Reducible) Loading: 0.3 (std & alt) [0.25(1.2)] Live (Storage) Loading: 0.6 (std & alt) [0.5(1.2)] Live (Parking) Loading: 0.3 (std & alt) [0.25(1.2)] Snow Loading: 0.3 (std & alt) [0.25(1.2)] Service Seismic Loading: 1.2 (std & alt)

62.2.12 Ultimate Seismic LC: 0.9D + 1.5E This load combination is intended for checking the strength limit state with applied seismic loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 0.9 (std) & 1.5 (alt) Service Seismic Loading: 1.5 (std & alt)

62.2.13 Sustained Service LC This load combination is intended for use in load history deflection calculations. For the purpose of this load combination, 100% of the Live (Storage) Loading and 50% of all other live loading is assumed to be permanent loading. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std & alt) Live (Unreducible) Loading: 0.5 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 0.5 (std & alt) Live (Roof) Loading: 0.5 (std & alt)

62.3 IS 875 (Part 2) live load factors It is recommended that, in order to get the appropriate factors, you draw: • car park loads on a Live (Storage) layer • assembly loads on a Live (Unreducible) layer

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Chapter 62 • storage loads on a Live (Storage) layer if you would like their effects to be reducible for beams (only), and on a Live (Unreducible) layer if you do not want their effects to be reduced for any member.

Note: If you draw car park loads on a Live (Storage) layer, however, RAM Concept applies a (conservative) load factor of 2.76 in the LT Uncracked Deflection LC.

62.4 IS 456 material behaviours This section explains how RAM Concept models the concrete, non-prestressed reinforcement and prestressed reinforcement when using IS 456/1343.

62.4.1 Concrete Behaviour This elastic modulus of concrete is defined by the user in the materials window. The user can choose to use the code equation of clause 6.2.3.1, an equation from another code, or a specified value. When values are directly specified, two elastic modulus values must be specified: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions When the IS 456 code equation is selected the following values are used: E ci = 5000 f cu i E c = 5000 f c u Where fcui = cube strength at stressing fcu = 28 day cube strength For calculations based on the “concrete section”, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses three different stress strain curves are used. All three stress-strain curves are paraboliclinear curves as detailed in IS456 Fig 21. The transition strain from the parabolic to the linear curve is at 0.002. For initial stress conditions, the peak stress in the stress strain curve is 0.67fcui . For service stress conditions, the peak stress in the stress-strain curve is 0.67fcu. For strength conditions, the peak stress in the stress-strain curve is 0.67fcu / 1.5 The strength stress-strain curves are truncated at a strain of 0.0035. The other stress-strain curves have no limit strain.

Note: Calculations on the gross cross-section always use the Ec values calculated above, while the cracked cross-section strain analyses use the stress strain curve of IS 456 Fig 21. The elastic modulus for these two conditions will therefore be different for most concrete strengths. This may have an effect on initial concrete strains and ECR calculations. For service design crack width calculations and for service design cracked stress analyses, a tension stiffened concrete stress strain curve is used:

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Use of this curve is similar, but not technically equivalent, to the provisions of IS 456 Annex F, Fig. 28. A comparison of the stress diagrams for the Code provision and the Concept implementation are shown below:

Fig. 28 Provision

Concept Implementation Since Concept’s crack width design does a cracked stress analysis (with a non tension stiffened concrete stress strain curve) for the 0.8 fy provision, the concrete and rebar stress results for members on which a crack width design is done will

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Chapter 62 represent the range of results between the tension stiffened and the non tension stiffened concrete stress strain curve. Concrete and rebar stress results for all other members will represent use the tension stiffened concrete stress strain curve only.

62.4.2 (Untensioned) Reinforcement Behaviour Untensioned reinforcement with a yield stress less than or equal to 250 N/mm2 is modeled as a perfectly elastic/plastic material as is shown in code figure 23B. All other untensioned reinforcement uses the Cold Worked Deformed Bar curve as is shown in code figure 23A. The elastic modulus is that specified by the user in the materials window instead of the codespecified 200,000 N/mm2. For strength considerations, a γ m of 1.15 is used. For all other considerations a γ m of 1.0 is used.

62.4.3 Bonded Prestressed Reinforcement Behaviour Prestressed reinforcement is modeled as using a power formula. The curve is defined by four parameters: Eps = the elastic modulus at zero strain (from materials window) Fpy = the “yield” stress of the reinforcement (from materials window) Fpu = the ultimate stress of the reinforcement (from materials window) γ m = partial safety factor for materials These four parameters are used to calculate the three parameters needed for the power formula, as described in Chapter 51, “Section Design Notes”. The three parameters are: E ps' = E ps F py' = F py ⁄ γm F pu' = F pu ⁄ γm For strength considerations, a γ m of 1.15 is used. For all other considerations a γ m of 1.0 is used. This curve is similar but slightly different than the Stress Relieved Curve as shown in IS : 1343 - 1980 Figure 5A for normal prestressing materials, assuming this curve depicts strain percentage and not actual strains.

62.4.4 Unbonded Prestressed Reinforcement Behaviour For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For ultimate resistance moment calculations, RAM Concept's general approach to unbonded tendon stress-strain curves is detailed in Chapter 51, “Section Design Notes”. For IS 456-2000, the maximum unbonded tendon stress (called flimit in Chapter 51, “Section Design Notes”) is defined by IS 1343-1980 Appendix B, Table 12. For IS 1343: 1980, the value used as a strain reduction factor for unbonded tendons is 0.1. RAM Concept assumes that each tendon is placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section). This assumption typically has no impact on the ultimate stress in the tendon as when the tendon is on the “wrong” side of the cross section

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Chapter 62 centroid, the stress in the tendon is less than fpb, due to the small tension strains (possibly compression strains) in the cross section at the tendon elevation.

62.5 IS 456 code rule selection The following explains how RAM Concept decides which IS456 code rules to apply based on the design strip segment or design section properties, combined with the active design rules for the rule set under consideration.


• Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

26.5.1.1 (456)

18.6.3.3 (1343)

One-Way Slab

26.5.2.1 (456)

18.6.3.3 (1343)

Two-Way Slab

26.5.2.1 (456)

18.6.3.3 (1343)

31.7.1 (456)

31.7.1 (456)



Each span segment has four user-specified reinforcement ratio values: • Column Strip Top Reinforcement • Column Strip Bottom Reinforcement • Middle Strip Top Reinforcement • Middle Strip Bottom Reinforcement

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Chapter 62 Concept’s User Minimum Reinforcement rule set uses these values to design reinforcement at each cross section. These values are not included in the reinforcement calculated for other rule sets. For example, the bending strength reinforcement reported in the Strength Rule Set is not in addition to the reinforcement in the User Minimum Reinforcement rule set. User Minimum Reinforcement Calculations



Pre-Concept 2.0 files require rebuilding of the load combinations and rule sets to have the User Minimum Reinforcement rule set added. See “Rebuilding load combinations” on page 39 of Chapter 11, “Specifying Load Combinations” for further information.

62.5.3 Initial Service (“Transfer”) • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

(none)

22.8.2.1 (1343) 22.8.2.2 (1343)

One-Way Slab

(none)

22.8.2.1 (1343) 22.8.2.2 (1343)

Two-Way Slab

(none)

22.8.2.1 (1343) 22.8.2.2 (1343)


62.5.4 Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • The design strip segment or design section property “Environment” is used to determine the “Type” of post-tensioned members as follows: Protected: Type 3 (0.2 mm crack) Normal: Type 3 (0.1 mm crack)

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Chapter 62 Corrosive: Type 2 Very Corrosive: Type 1 • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

26.3.3/Annex F (456) 22.7.1 (1343) 22.8.1.1 (1343) 22.8.1.2 (1343) 26.3.3/Annex F (456) (except Type 1)

One-Way Slab


Two-Way Slab



Note: Crack width design is done on all post-tensioned members except Type 1. This is required by IS 1343 11.3.2 and IS 456 26.3.3. Since the spacing provisions of 26.3.3 are not specifically applied, detailed crack width design is performed for all members in accordance with 26.3.3. Crack width design is not required for Type 1 members as by definition they have no tensile stresses, and thus no cracking. See code implementation for additional information.

62.5.5 Strength • Tendons are considered as an internal section force (and the hyperstatic loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • See “Torsion Considerations” on page 405 for how torsion is implemented.

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RC

PT

Beam

38 (456)

22.1 (1343)

40 (456)

22.4 (1343)

41 (456)

22.5 (1343)

26.5.1.5 - 26.5.1.7 (456) 18.6.3.2c (1343) One-Way Slab

38 (456)

22.1 (1343)

40 (456)

22.4 (1343)

41 (456)

22.5 (1343)

26.5.1.5 - 26.5.1.7 (456) 18.6.3.2c (1343) Two-Way Slab

38 (456)

22.1 (1343)

40 (456)

22.4 (1343)

41 (456)

22.5 (1343)

26.5.1.5 - 26.5.1.7 (456) 18.6.3.2c (1343) Table 62-4 Strength rule mapping

Note: * - IS 456 Clause 41 and IS 1343 Clause 22.5 are applied only if “beam” torsion is selected (see torsion design notes) 62.5.6 Ductility • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The longitudinal reinforcement from all other designs (except other ductility) is considered to be in place before ductility reinforcement is added. • The bending moments sign (or signs) is determined by the moment envelope for the rule set layer (ductility could be required for both positive and negative moments). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

37.1.1d (456)

21.1.1d (1343)

38.1f (456) One-Way Slab

37.1.1d (456)

21.1.1d (1343)

38.1f (456) Two-Way Slab

37.1.1d (456)

21.1.1d (1343)

38.1f (456) Table 62-5 Ductility rule mapping

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62.6 IS 456 code implementation

62.6.1 Section 26.5.1.1 Included code sections - item a. Excluded code sections - item b. The 0.85bd/fy criterion is implemented b is taken the core width (see “Concrete “Core” Determination” on page 405). If the core width is zero (there is no core), then b is taken as the width of the section. Post-tensioning is ignored. This provision is applied to beams only. The provisions of item b (Maximum reinforcement) are not considered. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

62.6.2 Section 26.5.2.1 Reinforcement is provided in accordance with 0.12 percent requirement. This assumes that high strength deformed bars have been provided. Post-tensioning is ignored. This provision is applied to slabs only. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

62.6.3 Section 31.7.1 The spacing between bars is limited to a maximum of 2 times the slab thickness. This provision is applied to slabs only. If the member is designated as post-tensioned, bonded (grouted) post-tensioning ducts that are on the tension side of the cross section centroid, or are within 10% of the cross section depth of the centroid elevation are considered as equivalent to an un-tensioned bar. These ducts are assumed to be optimally placed for spacing purposes - their plan locations are ignored. This implementation is somewhat more conservative than a literal reading of the code requirements. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations.

62.6.4 Section 37 / 38 Redistribution of moments (Ductility Check) Included code sections - 37.1.1 (item d), 38.1 (item f). Excluded code sections - 37 (rest), 38 (rest). RAM Concept does not currently redistribute moments, but applies 37.1.1 (item d) as a limit to the neutral axis depth, thereby ensuring ductility. The neutral axis depth is limited to 0.6 times the effective depth.

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Chapter 62 0.0035 The neutral axis depth is further limited to ----------------------------- in accordance with 38.1 item f; εy 0.0055 + -----γm where ε y = maximum reinforcement yield strain of all reinforcement in the cross section in tension.

62.6.5 Section 38 Design resistance moment of beams Included code sections - 38.1. Excluded code sections - none. Items a, b, c, d and e of section 38.1 are followed. Item f is applied under “Ductility” design. Strain compatibility design is used. The maximum compressive strain is 0.0035. See the Materials section for the material stress strain curves ( γ m = 1.5 for concrete; γm = 1.15 for reinforcement). Reinforcement areas are not deducted from the concrete area. Post-tensioning Tendon forces are ignored. For cross sections with multiple concrete mixes, the stress-strain curve of each concrete block is used appropriately. Axial forces (loads) on the section are either considered or ignored based on the settings in the design section or design span under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design span properties) is necessary to ensure a safe design. RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See Ductility in the previous section for applying ductility requirements. For cross sections with very small moments, the amount of reinforcement calculated by Concept may exceed the amount necessary. This is because Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement Concept selects is that necessary for axial force equilibrium in the cross section.

62.6.6 Section 40 Design shear resistance Included code sections - 40.1 (partial), 40.2, 40.3, 40.4, 26.5.1.5, 26.5.1.6 Excluded code sections - 40.1.1, 40.5 See “Concrete “Core” Determination” on page 405 for calculation of b. τ c is calculated per Table 19, using the equation in SP 24 (1983). Longitudinal reinforcement designed by Minimum, Service and Strength designers is considered in the determination of As used in the calculation of τ c . 100As / bd is taken as 0.15 minimum and 3.0 as a maximum in accordance with the “<=0.15” and “3.00 and above” in table 19. vc is calculated per the equation in SP:24 - 1983 to calculate values from Table 19. RAM Concept

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Chapter 62 For one-way shear in slabs, the design shear strength is increased by the depth factor in accordance with 40.2.1.1 For cross sections with multiple concrete mixes, the minimum fcu is used. The effective depth is determined by a cracked section analysis using the bending moment and axial force in place at time of the shear being investigated. If all of the reinforcement in the cross section is in compression, then the effective depth is calculated as the distance from the compression-most face to the furthest active reinforcement (in this case 100As / bd is taken as 0.15). fy is limited to 415 N/mm2. Stirrups are provided per 26.5.1.5, 26.5.1.6, and 40.4 In beams, at least minimum stirrups will be provided at all locations. Maximum allowable shear stress is determined in accordance with Table 20. Slabs use 1/2 the values in Table 20 in accordance with 40.2.3.1. Maximum spacing of stirrups along the span is the smaller of 0.75 d and 300 mm. The spacing across the span is not considered. Bent up bars and regions close to supports are not considered. The anchorage of longitudinal bars is not checked. Enhanced shear strength close to supports is not considered. Beams of varying depth are not considered. Net axial compression is considered per 40.2.2 if the “Consider Net Axial…” checkbox is checked. Bottom loaded beams are not considered.

62.6.7 Section 41 Torsion Included code sections - 41.1, 41.3, 41.4, 26.5.1.5, 26.5.1.6, 26.5.1.7 Excluded code sections - 41.2 Only the “core” of a cross section is used for torsion design. See “Concrete “Core” Determination” on page 405. If the core consists of multiple ribs, then the torsion calculations are performed for an average rib: • rib width = total core width / num ribs • with ultimate forces scaled down by the number of ribs (/ num ribs) and capacity and reinforcement scaled back up by the number of ribs (* num ribs). • code provisions are not applicable to multiple ribs, so to get a more exact calculation, use a separate design section or design strip for each rib. Equivalent shear Ve is calculated per clause 41.3.1. Equivalent bending moment Me1 is calculated per clause 41.4.2. Shear and torsion reinforcement is provided in accordance with clause 26.5.1.6 and 26.5.1.7. Area of torsion reinforcement and longitudinal reinforcement is calculated in accordance with clause 41.4. Maximum spacing of links is the least of x1, (x1 + y1)/4 or 300 mm. If torsion design is selected, at least minimum stirrups will be provided at all locations.

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62.6.8 Annex F Assessment of Crack Widths Un-tensioned reinforcement is added to ensure that the reinforcement stresses remain below 0.8fy. Crack widths are calculated per Annex F. A concrete stress strain curve that approximates tension stiffening is used - see discussion on “Concrete Behaviour” on page 581. Creep is not considered. Un-tensioned reinforcement is added to keep crack widths at or below the following limits: Environment: • Protected - 0.3 mm • Normal - 0.3 mm • Corrosive - 0.2 mm • Very corrosive - 0.1 mm These limits are specified in IS 456 clause 35.3.2. They are applied to post-tensioned members as well (except type 1) even though they do not match the limiting crack width values for Type 3 in Table 8. This results in a crack width limit design to 0.3 mm for Type 3 members and a crack width limit design to 0.2 mm for Type 2 members. This crack width design is required by IS 1343 11.3.2 and IS 456 26.3.3 since bar spacing limits have not been specifically applied. This criterion is applied to two-way slabs, but will not provide accurate crack width predictions for two way slabs when wide design strip segments or wide design sections are used. The crack-limiting capabilities of appropriately placed bonded post-tensioning tendons are considered, and the balance loading will be considered if included in the load combinations. In determining the effectiveness of bonded tendons, the equation can be manipulated as follows: Crack width = (3acrεm) / [1+2(acr - cmin) / (h-x)] = εm s c sc = 3acr / [1+2(acr - cmin) / (h-x)] = crack spacing Concept assumes the maximum crack spacing is 3(h-x). Concept assumes that each bar and bonded tendon is placed horizontally to give the same crack spacing. Bars and tendons that - due to their elevation - cannot provide the crack spacing are ignored. sc = 3acr / [1+2(acr - cmin) / ht] where ht = (h-x) = height of tension zone sc = 3acr ht / [ht +2(acr - cmin)] sc [ht +2(acr - cmin)] = 3acr ht sc ht +2scacr - 2sccmin = 3acr ht sc ht - 2sccmin = 3acr ht - 2scacr sc ht - 2sccmin = acr (3ht - 2sc) acr = (sc ht - 2sccmin) / (3ht - 2sc) However, a cr =

2

2

sb + c min , where sb = half the horizontal spacing between reinforcement.

Using this final equation, Concept determines a spacing for each bar or bonded tendon that is effective in controlling cracking. Concept iteratively determines the sc that gives the sbs that sum to the tension face width. For bonded tendons, the cover cmin is assumed to be the cover to the centroid of the tendon, and the “bar” diameter is assumed to be zero. Both of these assumptions are conservative.

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62.7 IS 1343 code implementation

62.7.1 Section 18.6.3.2c Minimum transverse reinforcement When the depth of the web is more than 4 times the thickness of the web, 0.1 percent reinforcement is provided in accordance with 18.6.3.2c. The spacing limit related to the clear depth of the web is not implemented. This spacing, however, should normally be comparable to the maximum spacing of 0.75 dt applied in other shear provisions.

62.7.2 Section 18.6.3.3 Minimum longitudinal reinforcement Reinforcement is provided in accordance with 0.15 percent requirement. This assumes that high strength deformed bars have been provided. Any bonded or unbonded tendon areas are applied to this provision before calculating any required untensioned reinforcement. Only tendons on the tension side (as determined by the minimum reinforcement setting) or within 10% of the cross section depth are used. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

62.7.3 Section 18.6.3.3 Limitation on area of prestressing tendons Un-stressed reinforcement is added to provide an ultimate moment capacity greater than the cracking moment. The cracking is assumed to be top (hogging moment) or bottom (sagging moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. Only sections within 1/6 of the span length from supports or 1/6 of the span length from midspan are checked, as these are considered as the likely locations of first cracking of concrete. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment (note that the 1.2 factor is not used in IS 1343)

62.7.4 Section 21.1.1 Redistribution of moments (Ductility Check) RAM Concept does not currently redistribute moments, but applies item “d” as a limit to the neutral axis depth, thereby ensuring ductility. The neutral axis depth is limited to 0.5 times the effective depth.

62.7.5 Section 22.1 Ultimate limit state for beams in flexure See section 38 for general approach. Note that if axial forces are included in the design (per the design span or design section setting), then the diversion of posttensioning forces into supports will cause a hyperstatic (secondary) tension in many design sections, as is appropriate. Post-tensioning Tendons are included. See “Post-tensioning Material Stress-Strain Curves” on page 395 for tendon stress-strain curves. Bonded tendon strains are calculated using strain compatibility. If a tendon is not perpendicular (in plan) to the cross section under consideration, then vector components of the cross section strains and the tendon stresses are used.

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Chapter 62 Unbonded tendon stresses are calculated using a strain reduction factor approach (see detailed description in “Unbonded Post-tensioning Stress-Strain Curves –General Theory” on page 396). If tendon centroid is closer to the extreme compression fiber than the compression reinforcement, a solution may not be possible.

62.7.6 Section 22.4 Design shear resistance of beams Vco is calculated per section 22.4.1. The flange/web intersection is not checked. Vcr is calculated per section 22.4.2. The value of Vc is used as shown in the following table. Moment

Vc Implementation

M < Mo

Vc = Vco Vc = (stress)bh

M > Mo

Vc = min (Vco, Vcr)

and tension is on the Vc = (stress)bh “tension” face * M > Mo

Vc = min (Vco, Vcr)

and no tension on the “tension” face *

Vc = (stress)bh d = dt (assumed) As = 0 (none in “tension zone”) Aps = 0 (none in “tension zone”)

Table 62-6 Vc rule mapping

Note: * The calculation of Mo uses only 80% of the stress due to prestress. This can produce the rare case where the section is in reality uncracked and has a tension face different to that calculated with Mo. For the unusual case of M > Mo and the section is actually uncracked (when considering the full prestress force) the conservative assumptions of column four are made. “d” is defined as the depth to the centroid of the tension force in the tension zone (including rebar and post-tensioning). This is slightly different (and likely more rational) than the distance from the extreme compression fibre to the centroid of the tendons as defined in the code. “dt” is defined as the maximum depth to any longitudinal mild reinforcement, or the depth to the centroid of the tendons, whichever is greater. The vertical tendon force component is ignored. For sections with multiple concrete mixes, the minimum fcu is used in calculations. Longitudinal reinforcement designed by Minimum, Service and Strength designers is considered in the determination of Ap used in the calculation of vc. b is adjusted by considering any tendons in the shear core. The full width of unbonded tendons is deducted, and two-thirds of the width of bonded tendons is deducted from b. For cross sections with multiple tendons, the fpu and fpe values used in the calculations are averaged. Longitudinal unstressed reinforcement is converted into equivalent area of prestressed reinforcement to determine Ap used in Table 6. RAM Concept

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Chapter 62 When calculating fpe/fpu, fpe is taken as the effective prestressing force divided by the equivalent area of prestressing steel. vc is calculated per the equation in SP : 24 - 1983 to calculate values from Table 6. For slabs, Table 6 values are modified by IS 456 40.2.1.1 as appropriate. Maximum shear stress is in accordance with Table 7. For slabs, this value is adjusted in accordance with IS 456 40.2.3.1. Shear reinforcement is calculated per 22.4.3. Minimum shear reinforcement is provided at all locations in beams. Minimum reinforcement is provided in slabs when Vu > Vc. The “web thickness” used in the calculations is the same as the shear core width - this may be incorrect if the core width is made up of multiple webs. In such cases, multiple design sections or design strips can be used; each containing only one web.

62.7.7 Section 22.5 Torsion Included code sections - 22.5.1, 22.5.3.1, 22.5.3.2, 22.5.4, 22.5.5 (item a and b) Excluded code sections - 22.5.2, 22.5.3.3, 22.5.5 (item c and d) Only the “core of a cross section is used for torsion design. See “Concrete “Core” Determination” on page 405. If the core consists of multiple ribs, then the torsion calculations are performed for an average rib: • rib width = total core width / num ribs • with ultimate forces scaled down by the number of ribs (/ num ribs) and capacity and reinforcement scaled back up by the number of ribs (* num ribs). • code provisions are not applicable to multiple ribs, so to get a more exact calculation, use a separate design section or design strip for each rib. Equivalent bending moment Me1 and Me2 are calculated per sections 22.5.3.1 and 22.5.3.2. Transverse bending moment Me3 is calculated and reported in the auditor per 22.5.3.3, but no transverse bending design is performed. Shear and torsion reinforcement is provided in accordance with sections 22.5.4.1, 22.5.4.2, 22.5.4.3 and 22.5.4.4. In the shear equation for Av in section 22.5.4.3, “dt” is substituted for “dl” to align this equation with the shear equation in 22.4.3.2 when no torsion is present. This change may not be conservative, but is consistent with the publication mentioned in the note below. Distribution of torsion reinforcement is calculated in accordance with section 22.5.5. Maximum spacing of torsion stirrups is the least of x1, (x1 + y1)/4 or 200 mm. If torsion design is selected, at least minimum stirrups will be provided at all locations.

Note: There is a typographical error in the code section 22.5.4.2 for the calculation of Ve1. The term in the numerator should be ec, not e as shown in the code. Also, equation for Tc in section 22.5.4.1 is typographically incorrect. Refer to publications “Design of Prestressed Concrete Beams Subjected to Combined Bending, Shear, and Torsion” by Rangan and Hall, ACI Journal March 1975 and “Strength of Rectangular Prestressed Concrete Beams in Combined Torsion, Bending, and Shear” by Rangan and Hall, ACI Journal April 1973 for details.

62.7.8 Section 22.7.1 Flexural tension stresses in concrete Hypothetical flexural tensile stress limits are taken from section 22.7.1.

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Chapter 62 For type 2 members, the temporary service loads adjustment is not taken. For bonded and unbonded cross sections, Type 3 hypothetical flexural tensile stress limits are taken from Table 8 as “Grouted post-tensioned tendons”. The values in Table 8 are multiplied by the Depth Factors in Fig. 6 as necessary. For each section, two limit stresses are calculated. The first limit stress is the maximum stress allowed if no supplemental un-tensioned reinforcement is used. The second limit stress is the absolute maximum stress allowed. The supplemental untensioned reinforcement is calculated in accordance with the Note under Table 8. Cross sections “with unbonded tendons” (see “Determination of Bonded vs. Unbonded Cross Sections” on page 595) are classified as “other members” when calculating supplemental reinforcement.

Note: When calculating supplemental reinforcement per the Note under Table 8, the additional reinforcement is calculated as a percentage of the cross-sectional area of the concrete in the tension zone as is done in BS 8110. This is different than a literal reading of the IS 1343 code.


62.7.10 Calculation of Supplemental Untensioned Reinforcement Supplemental reinforcement is calculated when the “unreinforced” stress limits are exceeded, even for the structure types where it is not anticipated by IS 1343. For example, if a type 1 beam has tension stresses exceeding 0 N/mm2, it will be marked as having failed the 22.7 criterion; supplemental reinforcement will still be calculated for the type 1 beam even though the reinforcement cannot solve the failure. The calculation of supplemental reinforcement per Note, Table 8 is as follows: Stress Difference = Actual Stress - Supplemental Reinforcement Limit Stress As = Act [(Stress Difference) / (100 * σ )] where Act = cross-sectional area of the concrete in the tension zone and σ = 3 N/mm2 for unbonded cross sections and 4 N/mm2 for bonded cross sections User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

62.7.11 Section 22.8.1 Design compressive stresses Compressive stresses in concrete based on the concrete section are limited to the values in Fig. 7 for Zone I. Zone II values are never applied. Direct compression stresses at the section centroid are limited to 0.8 times the value determined from Fig. 7.

62.7.12 Section 22.8.2 Design compressive stresses (Transfer) Compressive stresses in concrete based on the cracked concrete section at transfer of prestress are limited to the values in Fig. 8 for post-tensioned work. If the limit stress is exceeded then reinforcement is added as required to limit the concrete stress; depending on the bending moment and axial forces, either compression reinforcement, tension reinforcement or both will be added. RAM Concept

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Chapter 62 For sections with multiple concrete strengths, the section limiting stress is reported as the smallest (absolute value) stress limit of all of the individual concrete areas. The average of the top and bottom concrete stress in the cracked section is limited to the direct compressive stress limit of 0.8 times the value from Fig. 8.

62.7.13 Punching shear design Refer to Chapter 66, “Punching Shear Design Notes”.

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63 EN 1992-1-1:2004 (Eurocode 2) With TR43 Design This chapter details RAM Concept’s implementation of Eurocode 2 (EC2):2004. This section describes two implementations of the code: • EC2 with the UK National Annex in conjunction with the TR-43 document for PT provisions • EC2 with the option to input the National Annex parameters The version that is utilized by RAM Concept is controlled using the Code selection. Selecting Eurocode 2-2004 (UK Annex) will activate the UK Annex option (with TR-43), while selecting Eurocode 2-2004 will activate the EC2 code with input National Annex parameters. When Eurocode 2-2004 is active, the annex factors are accessed through the Criteria->EC2 Annex menu item.

Figure 63-1 EC2 Annex dialog

The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules

63.1 EC2 default loadings This section provides information on the loadings that RAM Concept creates by default when you start a new EC2 file. As the purpose and use of most of the loadings are self-explanatory, only items that are particularly noteworthy are discussed

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Chapter 63 here. It is important to note that the user may create his or her own load combinations where the default loadings do not comply with the particular national Codes.

63.1.1 Temporary Construction (At Stressing) Loading This loading type describes a temporary loading that is present during construction when the contractor stresses the tendons. As it is a temporary load, it is generally only included in the Initial Service Load Combination. If a permanent load is present at stressing, it should be defined on the Temporary Construction (At Stressing) loading layer as well as the appropriate permanent loading layer. Alternatively, you can include a permanent loading present at stressing with appropriate use of load factors.

63.1.2 Snow Loading For generation of load combinations, this loading type describes the design snow load for a particular floor or roof, which generally consists of the ground snow load modified by any necessary factors to adjust for roof snow loads, roof shape coefficients, drifting, etc. RAM Concept uses the factors from Eurocode 0, Table A1.1 for sites located at altitude H less than or equal to 1000 m a.s.l.

63.1.3 Live (Parking) Loading For generation of load combinations, this loading type describes the load for Category F, traffic areas with vehicle weight less than or equal to 30 kN.

63.2 EC2 Default Load Combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new Eurocode 2 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from the Eurocode unless noted otherwise.


63.2.2 Dead + Balance LC This load combination sums all of the dead loadings with the balance loads, with a load factor of 1.0, that act simultaneously in the standard service condition. This load combination is for information only - it is not used by RAM Concept for design purposes.


Note: Although elastic shortening produces a short-term loss, in RAM Concept elastic shortening losses are considered part of the long term loss lump sum. Self-Dead Loading: 1.0 (std & alt) 598

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Chapter 63 Temporary Construction Loading (At Stressing): 1.0 (std & alt)

63.2.4 Characteristic Service LC: D + L + 0.5S This load combination is intended for checking the characteristic serviceability limit state. It conservatively does not consider combination factors for live loads, even though the Code technically permits ψ0 to be applied to all accompanying variable actions. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.5 (std) & 0.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.5 Characteristic Service Snow LC: D + ψ0L + S This load combination is intended for checking the characteristic serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.7 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.7 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 0.7 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.6 Frequent Service LC: D + ψ1L This load combination is intended for checking the frequent serviceability limit state. It conservatively applies ψ1 to all live loads, even though the Code technically permits ψ2 to be applied to accompanying variable actions. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.7 (std) & 0.0 (alt) Live (Storage) Loading: 0.9 (std) & 0.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.7 Frequent Service Snow LC: D + ψ2L + 0.2S This load combination is intended for checking the frequent serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) RAM Concept

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Chapter 63 Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.3 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.8 (std) & 0.0 (alt) Live (Parking) Loading: 0.6 (std) & 0.0 (alt) Snow Loading: 0.2 (std) & 0.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.8 Quasi-Permanent Service LC: D + ψ2L This load combination is intended for checking the quasi-permanent serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.3 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.8 (std) & 0.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.9 Ultimate LC: γG,sup D + 0.9H + γQi ψ0L + γQi ψ0S This load combination is intended for checking the strength limit state in accordance with Exp. (6.10a) in Table A1.2 (B). The load factors used are: Hyperstatic Loading: 0.9 (std) & 1.1 (alt) Dead Loading: 1.35 (std) & 1.0 (alt) Live (Reducible) Loading: 1.05 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.05 (std) & 0.0 (alt) Live (Storage) Loading: 1.5 (std) & 0.0 (alt) Live (Parking) Loading: 1.05 (std) & 0.0 (alt) Live (Roof) Loading: 1.05 (std) & 0.0 (alt) (Only included in BS EN 1990:2002 UK National Annex) Snow Loading: 0.75 (std) & 0.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.10 Ultimate LC: γG,sup ξ D + 0.9H + γQi ψ0L + γQ1 S This load combination is intended for checking the strength limit state in accordance with Exp. (6.10b) in Table A1.2 (B). The load factors used are: Hyperstatic Loading: 0.9 (std) & 1.1 (alt) Dead Loading: 1.25 (std) & 1.0 (alt)

(BS EN 1990:2002 UK National Annex, ξ = 0.925)

Dead Loading: 1.15 (std) & 1.0 (alt)

(Eurocode 0, ξ = 0.85)

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Chapter 63 Live (Reducible) Loading: 1.05 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.05 (std) & 0.0 (alt) Live (Storage) Loading: 1.5 (std) & 0.0 (alt) Live (Parking) Loading: 1.05 (std) & 0.0 (alt) Snow Loading: 1.5 (std) & 0.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.11 Ultimate LC: γG,sup ξ D + 0.9H + γQ1 L + γQi ψ0S This load combination is intended for checking the strength limit state in accordance with Exp. (6.10b) in Table A1.2 (B). It conservatively applies a factor of 1.5 to all live loads, even though the Code technically permits ψ0 to be applied to accompanying variable actions. The load factors used are: Hyperstatic Loading: 0.9 (std) & 1.1 (alt) Dead Loading: 1.25 (std) & 1.0 (alt)



(Eurocode 0, ξ= 0.85)

Live (Reducible) Loading: 1.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.5 (std) & 0.0 (alt) Live (Parking) Loading: 1.5 (std) & 0.0 (alt) Live (Roof) Loading: 1.5 (std) & 0.0 (alt) Snow Loading: 0.75 (std) & 0.0 (alt)

Note: Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.12 Accident LC This load combination is intended for checking the accident limit state. The load factors used are: Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std & alt) Snow Loading: 1.0 (std & alt)

63.2.13 Characteristic Service Wind LC: D + ψ0L + ψ0S + W This load combination is intended for checking the characteristic serviceability limit state with wind. It considers wind as the leading action and applies ψ0 to accompanying variable actions. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.7 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.7 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt)

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Chapter 63 Live (Parking) Loading: 0.7 (std) & 0.0 (alt) Snow Loading: 0.5 (std) & 0.0 (alt) Wind-Service Loading: 1.0 (std) & -1.0 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.14 Characteristic Service Wind LC: D + ψ0L + S + ψ0W This load combination is intended for checking the characteristic serviceability limit state with wind. It considers snow as the leading action and applies ψ0 to accompanying variable actions. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.7 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.7 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 0.7 (std) & 0.0 (alt) Snow Loading: 1.0 (std) & 0.0 (alt) Wind-Service Loading: 0.5 (std) & -0.5 (alt) (BS EN 1990:2002 UK National Annex) Wind-Service Loading: 0.6 (std) & -0.6 (alt) (Eurocode 0)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.15 Characteristic Service Wind LC: D + L + ψ0S + ψ0W This load combination is intended for checking the characteristic serviceability limit state with wind. It considers wind and snow as the accompanying actions and treats all live loads as leading actions. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 1.0 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.0 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.5 (std) & 0.0 (alt) Wind-Service Loading: 0.5 (std) & -0.5 (alt) (BS EN 1990:2002 UK National Annex) Wind-Service Loading: 0.6 (std) & -0.6 (alt) (Eurocode 0)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.16 Frequent Service Wind LC: D + ψ2L + ψ1W This load combination is intended for checking the frequent serviceability limit state with wind.

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Chapter 63 The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.3 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.6 (std) & 0.0 (alt) Live (Storage) Loading: 0.8 (std) & 0.0 (alt) Wind-Service Loading: 0.2 (std) & -0.2 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.17 Ultimate Wind LC: γG,sup D + 0.9H + γQi ψ0L + γQi ψ0S + γQi ψ0W This load combination is intended for checking the strength limit state in accordance with Exp. (6.10a) in Table A1.2 (B). The load factors used are: Hyperstatic Loading: 0.9 (std) & 1.1 (alt) Dead Loading: 1.35 (std) & 1.0 (alt) Live (Reducible) Loading: 1.05 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.05 (std) & 0.0 (alt) Live (Storage) Loading: 1.5 (std) & 0.0 (alt) Live (Parking) Loading: 1.5 (std) & 0.0 (alt) Live (Roof) Loading: 1.05 (std) & 0.0 (alt) ) (Only included in BS EN 1990:2002 UK National Annex) Snow Loading: 0.75 (std) & 0.0 (alt) Wind-Service Loading: 0.75 (std) & -0.75 (alt) (BS EN 1990:2002 UK National Annex) Wind-Service Loading: 0.90 (std) & -0.90 (alt) (Eurocode 0)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.18 Ultimate Wind LC: γG,sup ξ D + 0.9H + γQ1 L + γQi ψ0S + γQi ψ0W This load combination is intended for checking the strength limit state in accordance with Exp. (6.10b) in Table A1.2 (B). The wind and snow loads are treated as accompanying actions and all live loads are treated as the leading actions. The load factors used are: Hyperstatic Loading: 0.9 (std) & 1.1 (alt) Dead Loading: 1.25 (std) & 1.0 (alt)

(BS EN 1990:2002 UK National Annex, ξ= 0.925)


(Eurocode 0, ξ= 0.85)

Live (Reducible) Loading: 1.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.5 (std) & 0.0 (alt) Live (Parking) Loading: 1.5 (std) & 0.0 (alt) Live (Roof) Loading: 1.5 (std) & 0.0 (alt)

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Chapter 63 Snow Loading: 0.75 (std) & 0.0 (alt) Wind-Service Loading: 0.75 (std) & -0.75 (alt) (BS EN 1990:2002 UK National Annex) Wind-Service Loading: 0.90 (std) & -0.90 (alt) (Eurocode 0)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.19 Ultimate Wind LC: γG,sup ξ D + 0.9H + γQi ψ0 L + γQ1S + γQi ψ0W This load combination is intended for checking the strength limit state in accordance with Exp. (6.10b) in Table A1.2 (B). The wind and live loads are treated as accompanying actions and snow loads are treated as the leading actions. The load factors used are: Hyperstatic Loading: 0.9 (std) & 1.1 (alt) Dead Loading: 1.25 (std) & 1.0 (alt)

(BS EN 1990:2002, ξ = 0.925)



Live (Reducible) Loading: 1.05 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.05 (std) & 0.0 (alt) Live (Storage) Loading: 1.5 (std) & 0.0 (alt) Live (Parking) Loading: 1.05 (std) & 0.0 (alt) Snow Loading: 1.5 (std) & 0.0 (alt) Wind-Service Loading: 0.75 (std) & -0.75 (alt) (BS EN 1990:2002 UK National Annex) Wind-Service Loading: 0.90 (std) & -0.90 (alt) (Eurocode 0)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used 63.2.20 Ultimate Wind LC: γG,sup ξ D + 0.9H + γQi ψ0 L + γQi ψ0S + γQ1W This load combination is intended for checking the strength limit state in accordance with Exp. (6.10b) in Table A1.2 (B). The wind load is treated as the leading action and all other variable loads are treated as accompanying actions. The load factors used are: Hyperstatic Loading: 0.9 (std) & 1.1 (alt) Dead Loading: 1.25 (std) & 1.0 (alt)




Live (Reducible) Loading: 1.05 (std) & 0.0 (alt) Live (Unreducible) Loading: 1.05 (std) & 0.0 (alt) Live (Storage) Loading: 1.5 (std) & 0.0 (alt) Live (Parking) Loading: 1.05 (std) & 0.0 (alt) Snow Loading: 0.75 (std) & 0.0 (alt) Wind-Service Loading: 1.5 (std) & -1.5 (alt)

Note: For mats / rafts this combination is broken into several combinations as no alternate factors are used

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63.2.21 Equilibrium Wind LC: 0.9D + γQ1W This load combination is intended for checking the equilibrium limit state in accordance with Exp. (6.10) in Table A1.2 (A). The wind load is treated as the leading action and all other variable loads are assumed to be favorable. This combination is only generated for mat foundations. The load factors used are: Balance Loading: 1.0 Dead Loading: 0.9 Wind-Service Loading: 1.5

63.3 Eurocode 1 Part 1-1 (UK National Annex) Live Load Reduction It is recommended that, in order to get the appropriate factors, you draw: • Domestic, residential, and office (Category A and B) loads on a Live (Reducible) layer • Assembly (Category C and D) loads on a Live (Unreducible) layer • Car park loads (Category F) on a Live (Parking) layer • Storage loads(Category E) on a Live (Storage) layer. • Roof loads (Category H) on a Live (Roof) layer

Note: Live load reduction will conservatively not be considered on Assembly loads in Category C and D. However it is necessary to assign the loads to the Live (Unreducible) type to get the appropriate factors in the load combinations.

63.4 EC2 Material behaviors This section explains how RAM Concept models the concrete, non-prestressed reinforcement and prestressed reinforcement when using Eurocode 2. The partial safety factors for the different materials will be defined by the used Annex. The BS EN 1990:2002 has fixed values and the Generic version allows the user to specify their values.

63.4.1 Concrete Behavior This elastic modulus of concrete is defined by the user in the materials window. The user can choose to use the code equation in table 3.1, an equation from another code, or a specified value. When values are directly specified, two elastic modulus values must be specified: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions

When the EC2 code equation is selected the following values are used: Eci = 22,000[(fcki + 8)/10]0.3 MPa (fcki in MPa) Ec = 22,000[(fck + 8)/10]0.3 MPa (fck in MPa) Where

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Chapter 63 fcki = characteristic cylinder strength at stressing fck = 28 day characteristic cylinder strength For calculations based on the “concrete section”, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses three different stress strain curves are used. All three stress-strain curves are paraboliclinear curves as detailed in clause 3.1.7. The transition strain is at εc2. For initial stress conditions, the peak stress in the stress strain curve is 0.85fcki . For service stress conditions, the peak stress in the stress-strain curve is 0.85fck. For strength conditions, the peak stress in the stress-strain curve is 0.85fck / γc,ult (γc,ult = 1.5 for BS EN 1990:2002 UK National Annex). For accident strength conditions, the peak stress in the stress-strain curve is 0.85fck/ γc,acc (γc,acc = 1.2 for BS EN 1990:2002 UK National Annex). The strength stress-strain curves are truncated at a strain of εcu2 or εc2 depending upon the eccentricity of the net axial force on the cross section. The other stress-strain curves have no limit strain.

Note: Calculations on the gross cross-section always use the Ec values calculated above, while the cracked cross-section strain analyses use the stress strain curve of Figure 3.3. The elastic modulus for these two conditions will therefore be different for most concrete strengths. This may have an effect on initial concrete strains and ECR calculations.

63.4.2 (Untensioned) Reinforcement Behavior Untensioned reinforcement is modeled as a perfectly elastic/plastic material, as is shown in code figure 3.8. The elastic modulus is that specified by the user in the materials window. For strength considerations, the program uses γs,ult (γs,ult = 1.15 for BS EN 1990:2002 UK National Annex). For other considerations (accident or serviceability), γs,acc and γs,serv are used (γs,acc = γs,serv = 1.0 for BS EN 1990:2002 UK National Annex).

63.4.3 Bonded Prestressed Reinforcement Behavior Prestressed reinforcement is modeled as using a power formula. The curve is defined by four parameters: Eps = the elastic modulus at zero strain (from materials window) Fpy = the “yield” stress of the reinforcement (from materials window) Fpu = the ultimate stress of the reinforcement (from materials window) γm = partial safety factor for materials These four parameters are used to calculate the three parameters needed for the power formula, as described in “Posttensioning Material Stress-Strain Curves” on page 395. The three parameters are: Eps’ = Eps Fpy’ = Fpy / γm Fpu’ = Fpu / γm For strength considerations, γs,ult is used (γs,ult = 1.15 for BS EN 1990:2002 UK National Annex).

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Chapter 63 For other considerations (accident or serviceability), γs,acc and γs,serv are used (γs,acc = γs,serv = 1.0 for BS EN 1990:2002 UK National Annex).

63.4.4 Unbonded Prestressed Reinforcement Behavior For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For accident strength conditions, RAM Concept assumes that unbonded tendons have no stress. For ultimate resistance moment calculations, RAM Concept's general approach to unbonded tendon stress-strain curves is detailed in Chapter 41, “Section Design Notes”. For Eurocode 2:2004, the maximum unbonded tendon stress (fpb, called flimit in “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397) is defined by the equation in TR-43 clause 5.8.5.5 for both BS EN 1990:2002 and the generic annex implementations. Since Concept uses the tendon length instead of the distance in function of the neutral axis depth, the approach may be considered as a lower bound solution and thus a load factor of 1.0 is used. When this equation is used in a cross section that contains multiple tendons, the following terms are used in the calculation: l / d = length of an individual tendon divided by its depth fpuAps = sum of all the individual tendons’ fpu multiplied by the vector component of their Aps fckbd = minimum concrete characteristic cylinder strength multiplied by the compression face width and the depth to the centroid of the vector component tendon area For Eurocode 2:2004, the value used as a strain reduction factor for unbonded tendons is k = 5d/L Where L = length of the unbonded tendon d = depth of the post-tensioning tendon (measured from the furthest concrete face) This is equivalent to assuming a neutral axis depth of 0.5 d and a “zone of inelasticity” of 10 times this length. RAM Concept assumes that each tendon is placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section). This assumption typically has no impact on the ultimate stress in the tendon as when the tendon is on the “wrong” side of the cross section centroid, the stress in the tendon is less than fpb, due to the small tension strains (possibly compression strains) in the cross section at the tendon elevation.

63.5 EC2 code rule selection The following explains how RAM Concept decides EC2 code rules to apply based on the design strip segment or design section properties, combined with the active design rules for the rule set under consideration.

63.5.1 Code Minimum Reinforcement • The structural system (as defined in the design section or design strip segment) is considered (beam, one-way slab, twoway slab). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The placement of the reinforcement is based on the “min. reinforcement location” selection for the design strip segment or design section: • Elevated Slab – Reinforcement is at top near supports and bottom near midspan. • Mat Foundation – Reinforcement is at bottom near supports and top near midspan.

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Chapter 63 • Tension Face – Reinforcement location is determined by the design moment envelope for the rule set (reinforcement may be required on both faces). • Top – Reinforcement is always located at the top of slab (Engineer discretion advised) • Bottom – Reinforcement is always located at the bottom of slab (Engineer discretion advised) • None – No reinforcement is provided (Engineer discretion advised) • Code Rules are applied as shown in the following table. Design System RC

PT

UK National Annex

Beam

9.2.1.1 TR-43 5.8.8

One-Way Slab

9.3.1.1 TR-43 5.8.8

Two-Way Slab

9.3.1.1 TR-43 5.8.8

Generic National Annex

Beam

9.2.1.1 9.2.1.1(1) and unbonded PT Beams 9.2.1.1(4)

One-Way Slab

9.3.1.1 9.3.1.1

One-Way Slab

9.3.1.1 9.3.1.1





The User Minimum Reinforcement rule set will not design reinforcement unless this rule set is used by at least one load combination.

608

RAM Concept

Chapter 63 Old Files

Pre-Concept 2.0 files require rebuilding of the load combinations and rule sets to have the User Minimum Reinforcement rule set added. See “Rebuilding load combinations” on page 33 of Chapter 11, “Specifying Load Combinations” for further information.

63.5.3 Initial Service (“Transfer”) • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

(none)

5.10.2.2 / TR-43 5.8.2

One-Way Slab

(none)

5.10.2.2 / TR-43 5.8.2

Two-Way Slab

(none)

5.10.2.2 / TR-43 5.8.2

UK National Annex


All Systems

(none)

5.10.2.2


63.5.4 Characteristic Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • The design strip segment or design section property “Environment” is used to determine the exposure category of members as follows: Protected: X0, XC1 Normal: XC2, XC3, XC4 Corrosive, Very Corrosive: XD1, XD2, XS1, XS2, XS3

RAM Concept

609

Chapter 63 • Code Rules are applied as shown in the following table: Design System

RC

Bonded PT

Unbonded PT

7.2 (2)

7.2 (2)

7.2(5)1

7.2 (5)

7.2 (5)1

7.2 (2)

7.2 (2)

7.2 (5)

7.2 (5)1

7.2 (2)

7.2 (2)

7.2(5)1

7.2 (5)

7.2 (5)1

TR-43 5.8.12 (Table 4)

TR-43 5.8.12 (Table 4)

TR-43 5.8.72

UK National Annex

Beam

One-Way Slab

Two-Way Slab

7.2(5)1

TR-43 5.8.72 Generic National Annex

All systems

7.2 (2)

7.2 (2)

7.2 (2)

7.2 (5)

7.2 (5)

7.2 (5)

Table 63-3 Characteristic service rule mapping

Note: 1 - for PT members 7.2(5) is only performed where “crack width” design is requested. Note: 2 - TR-43 5.8.1/5.8.7 hypothetical stress limit design is only performed where “stress” design is requested. 63.5.5 Frequent Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • The design strip segment or design section property “Environment” is used to determine the exposure category of members as follows: • Protected: X0, XC1 • Normal: XC2, XC3, XC4 • Corrosive, Very Corrosive: XD1, XD2, XS1, XS2, XS3

610

RAM Concept

Chapter 63 • Code Rules are applied as shown in the following table: Design System

RC

Bonded PT

Unbonded PT

7.31

TR-43 5.8.12

TR-43 5.8.12

TR-43 5.8.72

7.31

TR-43 5.8.12

TR-43 5.8.12

TR-43 5.8.72

7.31

TR-43 5.8.12 (Table 5)

TR-43 5.8.12 (Table 5)

TR-43 5.8.72

UK National Annex

Beam

(none)

One-Way Slab

Two-Way Slab

(none)

(none)

TR-43 5.8.72 Generic National Annex

All Systems

(none)

7.3

(none)

Table 63-4 Frequent service rule mapping

Note: 1 - for PT members 7.3 is only performed where “crack width” design is requested. Note: 2 - TR-43 5.8.1/5.8.7 hypothetical stress limit design is only performed where “stress” design is requested. 63.5.6 Quasi-Permanent Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • The design strip segment or design section property “Environment” is used to determine the exposure category of members as follows: • Protected: X0, XC1 • Normal: XC2, XC3, XC4 • Corrosive, Very Corrosive: XD1, XD2, XS1, XS2, XS3 • Code Rules are applied as shown in the following table: Design System

RC

Bonded PT

Unbonded PT

7.32

7.31

7.32

7.3

UK National Annex

All systems

7.3


All systems

7.3

Table 63-5 Quasi-Permanent service rule mapping

Note: 1- for Unbonded PT members, 7.3 is only performed where “crack width” design is requested. Note: 2- for Bonded PT members, only the decompression design is applied for the appropriate exposure. RAM Concept

611

Chapter 63


RC

PT

UK National Annex

All types

6.1

6.1 / TR-43 5.8.5

6.2

6.2 / TR-43 5.9

6.3

6.3


All types

6.1

6.1

6.2

6.2

6.3

6.3


63.5.8 Ductility • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The longitudinal reinforcement from all other designs (except other ductility) is considered to be in place before ductility reinforcement is added. • The bending moments sign (or signs) is determined by the moment envelope for the rule set layer (ductility could be required for both positive and negative moments). • Code Rules are applied as shown in the following table. Design System

RC

PT

All Systems

5.5

5.5


63.5.9 Accident • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces). • Reduced γm factors are used in the strength calculations. For reinforcement γm = 1.0 (BS EN 1990:2002). • Reinforcement location is determined by the Min. Reinforcement Location setting. • The minimum tensile force that an internal tie is capable of resisting varies between the BS EN 1990-2002 and the Generic version, which uses the Eurocode general recommendation.

612

RAM Concept


RC

PT

All Types

9.10

9.10

Table 63-8 Accident rule mapping

63.6 EC2 code implementation

63.6.1 Section 5.5 Redistribution of moments (Ductility Check) Included code sections – (4) Excluded code sections – (1), (2), (3), (5), (6) RAM Concept does not currently redistribute moments, but applies 5.5(4) as a limit to the neutral axis depth, thereby ensuring ductility. The neutral axis depth is limited to: (1.0 – k1)/k2 * effective depth for fck ≤ 50 MPa (1.0 – k3)/k4 * effective depth for fck > 50 MPa where k1, k2, k3, and k4 are taken from the curent National Annex. Only k1 and k3 may be modified in the Generic version.

63.6.2 Section 5.10.2.2 Limitation of Concrete Stress (Transfer) Included code sections – (5). Excluded code sections – (1), (2), (3), (4). The compressive stresses in the concrete, based on the cracked section, are limited to 0.6fcki.

63.6.3 Section 6.1 Design resistance moment Included code sections – (1), (2), (3), (7) Excluded code sections – (4), (5), (8) Strain compatibility design is used. The maximum compressive strain is εcu2. See the Materials section for the material stress strain curves. Reinforcement areas are not deducted from the concrete area. For span segments or design sections not designated as “post-tensioned”, post-tensioning tendon forces are ignored. For cross sections with multiple concrete mixes, the stress-strain curve of each concrete block is used appropriately. Axial forces (loads) on the section are either considered or ignored based on the settings in the design section or design span under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, RAM Concept

613

Chapter 63 then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design span properties) is necessary to ensure a safe design. RAM Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an overreinforced section. See Ductility in the previous section for applying ductility requirements. For cross sections with very small moments, the amount of reinforcement calculated by RAM Concept may exceed the amount necessary. This is because RAM Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement RAM Concept selects is that necessary for axial force equilibrium in the cross section. A tension design is performed for longitudinal torsion tension required by the torsion model. This design assumes the design yield stress of the reinforcement and the calculated reinforcement is in addition to other requirements for flexure. Tension demand on a particular face is reduced by the minimum expected value of the compression chord on that face due to flexure.

63.6.4 Section 6.2 Design shear resistance Included code sections – 6.2.1(1)(partial), 6.2.1(2), 6.2.1(3), 6.2.1(4), 6.2.1(5), 6.2.1(6), 6.2.1(7), 6.2.2(1), 6.2.2(2), 6.2.2(5), 6.2.3(1), 6.2.3(2), 6.2.3(3), 6.2.3(6) Excluded code sections – 6.2.1(1)(partial), 6.2.1(8), 6.2.1(9), 6.2.2(3), 6.2.2(4), 6.2.2(6), 6.2.2(7), 6.2.3(4), 6.2.3(5), 6.2.3(7), 6.2.3(8), 6.2.4 (all), 6.2.5 (all) See “Concrete “Core” Determination” on page 260 for calculation of b. VRd,c is calculated using equation 6.2. For PT members uncracked in bending only equation 6.4 is used. For PT members that are cracked in bending, the minimum of equation 6.2 and 6.4 is used. Longitudinal untensioned tension reinforcement designed in Pass 1 and, if the member is PT, the area of bonded tendons in the tension zone is included in the determination of Asl used in the calculation of VRd,c. bw,nom is the width of the shear core, less the width of the tendon ducts in accordance with 6.2.3(6). Bonded tendons are considered to be grouted metal ducts. Any bonded ducts with diameter less than or equal to bw/8 are not considered in the deduction. bw,nom is used in all shear calculations, including ρw For cross sections with multiple concrete mixes, the minimum fck is used. The effective depth is determined by a cracked section analysis using the bending moment and axial force in place at time of the shear being investigated. The effective depth is calculated as the distance from the compression most face to the resultant tension force. For cross sections with no reinforcement in tension, a “column style” effective depth is determined from the compression most face to the maximum depth of any reinforcement. If the member is declared PT, the primary axial force contribution to σ cp in the calculation of equation 6.2.a, 6.2.b, and 6.4 is multiplied by γP,fav. The primary axial force contribution to σcp used in equation 6.11 is multiplied by either γP,fav or γP,unfav, whichever results in the lowest value of αcw. The “shift rule” required by 6.2.2(5) and 9.2.1.3 is performed for all members (with and without shear reinforcement) by attempting to extend the reinforcement beyond the required development length by 1.125 times the effective depth. This is calculated using eq. 9.2 and using z = 0.9d and cot θ = 2.5. Additional tension reinforcement in accordance with 6.2.3(7) is assumed to be accounted for using this provision. In normal circumstances, this will be the case because the horizontal shift required by 6.2.2(5) is related to the magnitude of the vertical shift performed according to 6.2.3(7). In all beams at least minimum links will be provided. Links are provided in accordance with 6.2.3 and 9.2.2. The angle is calculated as the minimum value that can satisfy the requirement that VEd ≤ VRd,max , within the range specified in 6.2.3(2). Minimum density of shear reinforcement is determined in accordance with 9.2.2(5). Maximum shear reinforcement spacing along the span is determined by 9.2.2(6).

614

RAM Concept

Chapter 63 The shear reinforcement spacing across the span is not considered. Bent up bars and regions close to supports are not considered. Net axial force is considered if the “Consider Net Axial…” checkbox is checked.

63.6.5 Section 6.3 Torsion Included code sections – 6.3.1(part), 6.3.2 Excluded code sections – 6.3.1(part), 6.3.3 Only the “core” of a cross section is used for torsion design. See “Concrete “Core” Determination” on page 260. If the core consists of multiple ribs, then the torsion calculations are performed for an average rib: • rib width = total core width / num ribs • with ultimate forces scaled down by the number of ribs (/ num ribs) and capacity and reinforcement scaled back up by the number of ribs (* num ribs). • code provisions are not applicable to multiple ribs, so to get a more exact calculation, use a separate design section or design strip for each rib. Torsion truss properties are calculated in accordance with 6.3.2(1). Link dimensions are determined from the location of specified cover to longitudinal design bars and do not explicitly account for the location of user reinforcement. The truss wall thickness, tef,i is limited by: • A/u per 6.3.2(1) • bw/2 • h/2 • horizontal spacing between outermost horizontal bars • vertical spacing between outermost horizontal bars The above limitations effectively create a truss wall with a longitudinal bar located at the center of the wall or outside the center of the wall (which is considered to be conservative). In these calculations RAM Concept assumes that the side cover to the longitudinal bars is the maximum of the top and bottom cover. If the interaction equation 6.31 is satisfied, only minimum reinforcement is provided. If equation 6.31 is not satisfied, equation 6.29 is used to calculate a maximum shear capacity by deducting the torsion portion of the interaction capacity. This equation is used to iteratively solve for the smallest value of theta that can satisfy the interaction equation 6.29. This theta is then used in all subsequent shear and torsion calculations. Maximum spacing of links is calculated in accordance with 9.2.3(3). Minimum torsion reinforcement is provided in accordance with 9.2.3(2). Minimum longitudinal tension reinforcement is calculated in accordance with equation 6.28. The tension demand on a particular face is reduced by the minimum expected compression chord force. If torsion design is selected and the torsion is greater than zero, at least minimum links will be provided.

63.6.6 7.2 Stress Limitation For all RC and PT members: • For the characteristic combination of loads, the compressive stress in the concrete based upon the cracked section is limited to k1 fck in accordance with 7.2(2). The value of k1 = 0.6 is used for the UK National Annex. Un-tensioned reinforcement is added to keep the concrete stresses within the prescribed limits.

RAM Concept

615

Chapter 63 • For the quasi-permanent combination of loads, the compressive stress in the concrete based on the cracked section is limited to k2 fck in accordance with 7.2(3). The value of k2 = 0.45 is used for the UK Annex. Un-tensioned reinforcement is designed to keep the concrete stresses within the prescribed limits. For all RC members and for PT members where crack width design is requested: • For the characteristic combination of loads, un-tensioned reinforcement is added to ensure that the reinforcement stresses remain below k3 fyk in accordance with 7.2(5). The value of k3 = 0.8 is used for the UK Annex.

63.6.7 7.3.1 Assessment of Crack Widths Crack widths are calculated per 7.3.4. Cracked equilibrium strains are calculated assuming that concrete has no tensile strength. Creep is not considered. Un-tensioned reinforcement is added to keep crack widths at or below the required limits. The design strip segment or design section property “Environment” is used to determine the exposure category of members as follows: • Protected: X0, XC1 • Normal: XC2, XC3, XC4 • Corrosive, Very Corrosive: XD1, XD2, XS1, XS2, XS3 UK National Annex crack width limits are in accordance with Table NA.4 of the applied National Annex. This criterion is applied to two-way slabs and other wide cross sections, but will not provide accurate crack width predictions for these wide cross sections when reinforcement is not spaced according to the varying stress patterns across the section. For narrower cross sections with a uniform stress pattern, the bonded reinforcement should be spaced uniformly. For this reason it may not be appropriate to do a “crack width” only design on full panel strip widths. The crack-limiting capabilities of appropriately placed bonded tendons are considered, and the balance loading will be considered if included in the load combinations. Bonded tendons are only considered effective if the average spacing of the bonded tendons and un-tensioned reinforcement within hc,eff is less than or equal to 300 mm in accordance with 7.3.2(3). Crack width = sr,max(εsm- εcm) εsm- εcm = [σs - kt (fct,eff/ρp,eff) (1 + αe ρp,eff)] / Es ≥ 0.6 σs / Es Concept uses a rearranged form of this equation, which utilizes strains instead of stresses εsm- εcm = σs / Es - kt[ (fct,eff/(ρp,eff Es) + (fct,eff/Ecm)] ≥ 0.6 σs / Es σs

=

kt =

tension stress in un-tensioned reinforcement from a cracked section analysis, or maximum differential bonded tendon stress from tendon stress level at zero strain in the concrete at the same level 0.6 for frequent service design 0.4 for quasi-permanent service design

fct,eff = fctm ρp,eff = (As + ξ12 Ap’)/Ac,eff As =

area of un-tensioned reinforcement within depth hc,eff

Ap’ =

area of bonded tendons within depth hc,eff

Ac,eff = area of concrete within depth hc,eff hc,eff = minimum of 2.5(h-d), (h-x)/3, or h/2 d=

616

depth to the outermost layer of reinforcement

RAM Concept

Chapter 63 ξ1 =

√ [ ξ (ϕs/ϕp)]

ξ=

0.5 for fck ≤ C50/60 0.25 for fck ≤ C70/85 Linearly interpolated between C50/60 and C70/85

ϕs =

largest diameter of reinforcement contained within depth hc,eff

ϕp =

1.6Ap’

αe =

Es/Ecm

sr,max = k3c + k1k2k4ϕeq /ρp,eff = crack spacing (eq. 7.11) k3 =

3.4 (Eurocode recommendation and BS EN 1990:2002, UK Annex, 7.3.4 (3))

c=

average cover to reinforcement, weighted by bar/tendon units

k1 =

0.8 for un-tensioned reinforcement 1.6 for bonded tendons averaged for cross sections containing both tendons and un-tensioned reinforcement, weighted by bar/tendon units

k2 =

0.5 for bending (compression strain on one face) (ε1 + ε2) / 2 ε1 for tension (tension strain on both faces)

k4 =

0.425 (Eurocode recommendation and BS EN 1990:2002, UK Annex, 7.3.4 (3))

ϕeq =

n1ϕ12 + n2ϕ22 + niϕi2 / (n1ϕ1 + n2ϕ2 + niϕi)

If the bonded reinforcement within hc,eff is less than or equal to 5(c+ ϕeq /2), RAM Concept uses equation 7.11 for sr,max. If a larger spacing exists, RAM Concept uses a crack spacing of 1.3(h-x) in accordance with equation 7.14. RAM Concept always assumes the maximum crack spacing is 1.3(h-x). For bonded PT systems, decompression is checked for exposure class XC2, XC3, and XC4 for the quasi-permanent load combination and for exposure class XD and XS for the frequent load combination. For the decompression checks, a check is made that the entire bonded tendon lies within 25mm of concrete in compression, using cracked section properties. For the purposes of this check the tendon is assumed to be round with a diameter equal to the “width” specified in the material properties.

63.6.8 Section 9.2.1.1 Beam Minimum Reinforcement Included code sections – (1), (4) Excluded code sections – (2), (3) This section applies only to beams. bt is taken as the width on the tension face. d is taken as the depth from the compression face (as determined from the “Code Min. Reinforcement Location” setting) to the centroid of reinforcement located closest to the tension face. In PT beams the tendon locations are included in this calculation. For cross sections with multiple concrete mixes, the maximum fck is used. See “Code Minimum Reinforcement ” on page 607 for details regarding which face (top or bottom) that the reinforcement will be added to. For RC beams, post-tensioning is ignored.

RAM Concept

617

Chapter 63 For PT beams, bonded post-tensioning that is on the tension-most side of the cross section centroid, or is within 10% of the cross section depth of the centroid elevation, is considered as un-tensioned reinforcement. For AsFy requirements, tendon (fpy – fse) is utilized as the available yield stress. Bonded tendons at an angle to the cross section will have vector components of their reinforcement areas applied toward these requirements. For unbonded PT beams, un-tensioned reinforcement is added to provide an ultimate moment capacity greater than 1.15 times the cracking moment. The cracking is assumed to be top (hogging moment) or bottom (sagging moment) based upon the “Min. Reinforcement Pattern” selected in the design strip segment or design section. Only sections within 1/6 of the span length from supports or 1/6 of the span length from midspan are checked, as these are considered as the likely locations of first cracking of concrete. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment (note that a 1.15 factor is used in EC2). The cracking stress is taken as fctm,fl in accordance with EC2 clause 3.1.8. For cross sections with multiple concrete mixes, the maximum fck for the cross section is used.

63.6.9 Section 9.3.1.1 RC Slab Minimum Reinforcement Included code sections – (1), (3) Excluded code sections – (2), (4) This section applies only to one-way slabs and two-way slabs. d is taken as the depth from the compression face (as determined from the “Code Min. Reinforcement Location” setting) to the centroid of reinforcement located closest to the tension face. In PT slabs the tendon locations are included in this calculation. For cross sections with multiple concrete mixes, the maximum fck is used. See “Code Minimum Reinforcement ” on page 607 for details regarding which face (top or bottom) that the reinforcement will be added to. For RC slabs, post-tensioning is ignored. For PT slabs, bonded post-tensioning that is on the tension-most side of the cross section centroid, or is within 10% of the cross section depth of the centroid elevation, is considered as un-tensioned reinforcement. For AsFy requirements, tendon (fpy – fse) is utilized as the available yield stress. Bonded tendons at an angle to the cross section will have vector components of their reinforcement areas applied toward these requirements. The maximum spacing between bars is limited to the minimum of 400mm or 3h. For two-way slabs in column strips in the first cross section in a support region, the spacing between bars is limited to the minimum of 250 mm or 2h. In post-tensioned slabs, bonded (grouted) post-tensioning ducts that are on the tension side of the cross section centroid, or are within 10% of the cross section depth of the centroid elevation are considered as equivalent to an un-tensioned bar. These ducts are assumed to be optimally placed for spacing purposes – their plan locations are ignored. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations.

63.6.10 Section 9.10 Tying Systems for Accidental Design Situations Each cross section is considered to act as a portion of an internal tie. Reinforcement at each cross section is placed on the tension face in accordance with the force envelopes for the Accident Rule set. Peripheral ties are not explicitly calculated by RAM Concept. 618

RAM Concept

Chapter 63 Tie force requirements are determined in accordance with the applied National Annex clause 9.10.2.3 (3). The Generic version uses the recommended value. The number of stories is conservatively assumed to be 10 or more, resulting in Ft = 60. lr is calculated as this cross section’s span length plus the larger adjacent span length. For design sections we calculate this value as twice this cross section’s span length. An equivalent uniform span load (force/length) is calculated representing (gk + qk) times the width of the span. This uniform span load is calculated as follows: • For span segments, the total span shear is calculated as the difference in shears at each end of the span. This value is calculated twice, once with the minimum V envelope at the span start and the maximum V envelope at the span end and once with the maximum V envelope at the span start and the minimum V envelope at the span end. The maximum of the differences in these values is used as the total span shear. The uniform span load is then calculated as the total span shear divided by the span length. • For design sections, the total span shear is calculated as the twice the maximum span shear, extrapolated from the cross section shear using the design section span ratio. The uniform span load is then calculated as the total span shear divided by the span length. For regions of low shear near mid-span where extrapolation may not be appropriate, we calculate the uniform span load from the moment at the cross section as M/al2 where a = (1/24 – α/2) and α is the span ratio from this cross section to mid-span. Tie requirements are considered as minimum requirements, not in addition to other requirements. The design yield stress of bonded tendons located anywhere in the cross section are applied toward the tie requirements. Vector components are used for tendons that are not perpendicular to the cross section.


63.6.12 TR-43 5.8.1 PT Service Stresses (Only for BS) This section applies to post-tensioned beams, one-way slabs, and two-way slabs. This section of TR43 defines hypothetical stress limits for comparison with gross section stresses. The design strip segment or design section property “Environment” is used to determine the exposure category of members as follows: • Protected: X0, XC1 • Normal: XC2, XC3, XC4 • Corrosive, Very Corrosive: XD1, XD2, XS1, XS2, XS3 For bonded beams and one way slabs, it is assumed that the hypothetical tensile stresses in Table 3 exist at the limiting crack width values given in Eurocode 2. For exposure class XD or XS, a limiting crack width value of 0.1mm is assumed for the determination of hypothetical tensile stresses. The recommended design strip property setting “PT Service Design Type” is either “Stress” or “Stress and Crack Width”. “Crack Width” only is not explicitly permitted by TR43. The supplemental reinforcement for bonded beams and one way slabs in accordance with TR43 5.8.1 is calculated as follows: Stress Difference = Actual Stress - Supplemental Reinforcement Limit Stress As = Act [(Stress Difference) / (400 N/mm2)] where Act = cross-sectional area of the concrete in the tension zone RAM Concept

619

Chapter 63 User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. For unbonded beam and one way slabs, for members with tension stresses supplemental reinforcement is always provided in accordance with TR43 5.8.7. TR43 does not provide an absolute tensile stress limit for exceeding the Table 3 values. As such, RAM Concept uses the Table 3 values as absolute limits and therefore does not permit enhancing the stresses by adding un-tensioned reinforcement. The recommended design strip property setting “PT Service Design Type” is either “Stress” or “Stress and Crack Width”. “Crack Width” only is not explicitly permitted by TR43. For two way slabs, for members with tension stresses supplemental reinforcement is always provided in accordance with TR43 5.8.7. Table 4 or Table 5 values are used depending upon whether or not full panel width strips are used (average stresses) or column/middle strips are used (‘design strip’ stresses). In determination of using ‘with bonded reinforcement’ limits the average spacing of the bonded reinforcement on the tension face is checked (using bonded tendons in the tension zone). If the bonded reinforcement spacing limit is greater than 500 mm at the time when the limits are being determined, the ‘without bonded reinforcement’ limits are used. Since the reinforcement in the service design is left in the cross section from force envelope to envelope, it is possible that an envelope will use the ‘without bonded reinforcement’ limits while the subsequent envelope will use ‘with bonded reinforcement’ limits due to the reinforcement added in the previous envelope. Where full panel width strips are used, the recommended design strip property setting “PT Service Design Type” is either “Stress” or “Stress and Crack Width”. “Crack Width” only is not explicitly permitted by TR43. In the case where column/middle strips are used the recommended setting is “Stress” or “Stress and Crack Width” or “Crack Width” as TR43 explicitly permits the stress limits in Table 5 to be exceeded where explicit crack width checks are performed. Tension limit without supplemental reinforcement

Absolute Tension Limit

Supplemental Reinforcement Calculation

Load Combination

0.2

Hypothetical Crack Width (used to determine stress limits) (mm) 0.2

1.65fctm

0.3fck

5.8.1

Frequent1,2

XC2, XC3, XC4

0.2

0.2

1.65fctm

0.3fck

5.8.1

Frequent1,2, Quasi-

XD or XS

0.2

0.1

1.35fctm

0.3fck

5.8.1

Unbonded Beam, One Way Slab

All

0.3

-

0

1.35fctm

5.8.7

Bonded Two Way Slab, Full Panel Width

X0, XC1

0.2

-

0(support) 0.9fctm(span)

0.9fctm

5.8.7

Permanent1 Characteristic2,

XC2, XC3, XC4

0.2

-


0.9fctm

5.8.7

Frequent1 Characteristic2,

XD or XS

0.2

-


0.9fctm

5.8.7

Permanent3 Characteristic2,

X0, XC1

0.2

-

1.2fctm

5.8.7

Frequent1,3 Frequent1,2

XC2, XC3, XC4

0.2

-

0(support) 1.2fctm(span) 0(support) 1.2fctm(span)

1.2fctm

5.8.7

XD or XS

0.2

-

1.2fctm

5.8.7

Unbonded Two Way Slab, Full Panel Width

All

0.3

-

0(support) 1.2fctm(span) 0(support) 0.3fctm(span)

0.9fctm

5.8.7

Unbonded Two Way Slab, Column/Middle Strips

All

0.3

-

1.2fctm

5.8.7

Member Type

Exposure Class

Code Design Crack Width (mm)

Bonded Beam, One Way Slab

X0, XC1

Bonded Two Way Slab, Column/Middle Strips

620


Permanent3 Frequent1,2,3 Frequent2, Quasi-

Frequent1, Quasi-

Frequent1,2, QuasiPermanent3 Frequent1,2,3 Characteristic2, QuasiPermanent1 Frequent2, QuasiPermanent1

RAM Concept

Chapter 63

Note: 1 - Used for crack width design (when requested by user) Note: 2 - Used for hypothetical stress checks (when requested by user) Note: 3 - Used for decompression check (when crack width design is requested by user) 63.6.13 TR-43 5.8.2 PT Initial Service (transfer) Stresses (Only for BS) This section applies to post-tensioned beams, one-way slabs, and two-way slabs. For beams and one-way slabs, where the flexural tensile stresses exceed 0.72fctm additional un-tensioned reinforcement is designed in accordance with 5.8.7. Compressive stresses are limited to the values in 5.8.2. For two-way slabs, the flexural compressive and tensile stresses are limited to the values in Table 5 for column/middle strip design, or Table 4 for full panel width design, where fck is replaced with fcki. For sections with multiple concrete mixes, the minimum fck is used to determine the limit stress and the peak stress reported may be approximate.

63.6.14 TR-43 5.8.3 PT Crack Control (Only for BS) This section applies to post-tensioned beams, one-way slabs, and two-way slabs. “Code” crack width limits are determined in accordance with Table NA.4 of the UK National Annex. See 7.3.1 Assessment of Crack Widths for additional information.

63.6.15 TR-43 5.8.5 PT Ultimate Limit State (Only for BS) This section applies to post-tensioned beams, one-way slabs, and two-way slabs. The equation for fpb is used to limit unbonded tendon stress. See “Unbonded Prestressed Reinforcement Behavior” for more information.

63.6.16 TR-43 5.8.7 PT Un-tensioned Reinforcement (Only for BS) This section applies to unbonded post-tensioned beams and one-way slabs, and to all post-tensioned two-way slabs. 0.625(Asfy + Apsfp) = F1 where F1 = tensile force in concrete As = area of un-tensioned reinforcement added fy = yield strength of un-tensioned reinforcement Aps = vector component area of bonded (grouted) tendons in tension zone fp = tendon yield stress - tendon effective stress It is possible that the added un-tensioned reinforcement will not be in the tension zone if a very large concrete cover is specified. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.

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Chapter 63 No check is made to ensure the cross section is post-tensioned.

63.6.17 TR-43 5.8.8 PT Minimum Reinforcement (Only for BS)

Note: There are no minimum un-tensioned reinforcement requirements for post-tensioned beams or one-way slabs that are primarily bonded. Refer to ““Determination of Bonded vs. Unbonded Cross Sections” on page 619 for discussion. For primarily unbonded post-tensioned beams and one-way slabs the requirements of 9.2.1.1 or 9.3.1.1 are applied as appropriate. For post-tensioned two-way slabs in column strips, un-tensioned reinforcement is provided in support regions as follows: As = 0.00075A ct. Act = sum of cross sectional area of column strip and adjacent middle strips(generated from the same span segment) For span segment strips, this criteria is only applied to the first cross section at a support if the span ratio is less than 0.2. For design sections, this criterion is applied when the span ratio is less than 0.2. The 300mm spacing requirement is not checked. The requirement that this reinforcement be concentrated between lines that are 1.5 times the slab depth is not checked. User defined reinforcement and bonded tendons that are at an angle to the cross section will only have the component perpendicular to the cross section considered. For post-tensioned two-way slabs, minimum reinforcement consisting of un-tensioned reinforcement and bonded tendons is provided as follows: As = 0.001Ac Ac = area of cross section For span segment strips, this criteria is only applied to the first cross section at a support if the span ratio is less than 0.2. For design sections, this criteria is applied when the span ratio is less than 0.2. The spacing of this reinforcement is limited to 500 mm. Bonded (grouted) post-tensioning ducts that are on the tension side of the cross section centroid, or are within 10% of the cross section depth of the centroid elevation are considered as equivalent to an un-tensioned bar. These ducts are assumed to be optimally placed for spacing purposes – their plan locations are ignored. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations. The recommendations for slab edge reinforcement are not implemented.

63.6.18 TR-43 5.9 Shear Strength (Only for BS) The values of σcp calculated in accordance with Eurocode 2, Clause 6.2 are modified by the appropriate safety factor γp,fav or γp,unfav as appropriate. The contribution of the vertical component of the tendon is not considered in one-way shear calculations.

622

RAM Concept

Chapter 64

64 CSA A23.3-04 Design This appendix details RAM Concept’s implementation of the Canadian Standard CSA A23.3-04. The six sections outline the following: • Default loadings • Default load combinations • Live load factors • Material behaviors • How code rules are selected for cross section design • Implementation of code rules

64.1 CSA A23.3-04 default loadings This section provides information on the loadings that RAM Concept creates by default when you start a new CSA A23.3-04 file. As the purpose and use of most of the loadings are self-explanatory, only items that are particularly noteworthy are discussed here.


64.1.2 Snow Loading For generation of load combinations, this loading type describes the design snow load for a particular floor or roof, which generally consists of the ground snow load modified by any necessary factors to adjust for roof snow loads, roof shape coefficients, drifting, etc. The importance factor should not be included in this loading, as it is addressed in the load combination factors.

64.2 CSA A23.3-04 default load combinations This section provides information on the default load combinations (technically, loading combinations) that RAM Concept creates when you start a new CSA A23.3-04 file. The purpose and origin of each load combination are given. You can remove or modify any of these load combinations. You can also add load combinations. The load combinations are from the National Building Code of Canada 2005 unless noted otherwise. The assumed importance factors for the default load combinations belong to the Normal Category. Importance factors are included in the load combinations, not the loadings. The corresponding load combinations will be generated incorporating

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Chapter 64 the appropriate importance factor for the “normal” category. For importance categories other than “normal”, the corresponding load combinations will need to be generated manually.

Note: Some load combinations in mat (raft) files are of the Lateral Group type and use a “Zero-Tension” analysis. Since a load combination using a “Zero-Tension” analysis does NOT use Alternate Envelope Factors, then such load combinations in mat files have been expanded into multiple load combinations. In some cases, the assumption that all gravity loads act in the same direction have been used to keep the number of load combinations to a minimum. See Chapter 11, “Specifying Load Combinations” for further description.




64.2.3 Service LC: D + L + 0.45S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.45 (std) & 0.0 (alt)

64.2.4 Service Snow LC: D + 0.5L + 0.9S This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 0.5 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Snow Loading: 0.9 (std) & 0.0 (alt)

624

RAM Concept

Chapter 64

64.2.5 Service Wind LC: D + 0.5L + 0.45S + 0.75W This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 0.5 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Snow Loading: 0.45 (std) & 0.0 (alt) Service Wind Loading: 0.75 (std) & -0.75 (alt)

64.2.6 Service Wind LC: D + L + 0.45S + 0.3W This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live Loading: 1.0 (std) & 0.0 (alt) Snow Loading: 0.45 (std) & 0.0 (alt) Service Wind Loading: 0.3 (std) & -0.3 (alt)

64.2.7 Service Wind LC: D + 0.5L + 0.9S + 0.3W This load combination is intended for checking the serviceability limit state. The load factors used are: Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Parking) Loading: 0.5 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Snow Loading: 0.9 (std) & 0.0 (alt) Service Wind Loading: 0.3 (std) & -0.3 (alt)

64.2.8 Sustained Service LC This load combination is intended for checking the serviceability limit state. For the purpose of this load combination, 100% of the Live (Storage) Loading and 50% of all other live loading is assumed to be permanent loading. The load factors used are:

RAM Concept

625

Chapter 64 Balance Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std & alt) Live (Unreducible) Loading: 0.5 (std & alt) Live (Storage) Loading: 1.0 (std & alt) Live (Parking) Loading: 1.0 (std & alt) Live (Roof) Loading: 0.5 (std & alt)

64.2.9 Factored LC: 1.4D This load combination is intended for checking the ultimate limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.4 (std) and 0.9 (alt)

64.2.10 Factored LC: 1.25D + 1.5L + 0.5S This load combination is intended for checking the ultimate limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.25 (std) and 0.9 (alt) Live (Reducible) Loading: 1.5 (std) and 0.0 (alt) Live (Unreducible) Loading: 1.5 (std) and 0.0 (alt) Live (Storage) Loading: 1.5 (std) and 0.0 (alt) Live (Parking) Loading: 1.5 (st) and 0.0 (alt) Live (Roof) Loading: 1.5 (std) and 0.0 (alt) Snow Loading: 0.5 (std) and 0.0 (alt)

64.2.11 Factored LC: 1.25D + 0.5L + 1.5S This load combination is intended for checking the ultimate limit state. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.25 (std) and 0.9 (alt) Live (Reducible) Loading: 0.5 (std) and 0.0 (alt) Live (Unreducible) Loading: 0.5 (std) and 0.0 (alt) Live (Storage) Loading: 1.0 (std) and 0.0 (alt) Live (Parking) Loading: 0.5 (st) and 0.0 (alt) Live (Roof) Loading: 0.5 (std) and 0.0 (alt) Snow Loading: 1.5 (std) and 0.0 (alt)

626

RAM Concept

Chapter 64

64.2.12 Factored Wind LC: 1.25D + 0.5L+ 0.5S + 1.4W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.25 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Live (Parking) Loading: 0.5 (std) & 0.0 (alt) Snow Loading: 0.5 (std) & 0.0 (alt) Service Wind Loading: 1.4 (std) & -1.4 (alt)

64.2.13 Factored Wind LC: 1.25D + 1.5L + 0.5S + 0.4W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.25 (std & alt) Live Loading: 1.5 (std) & 0.0 (alt) Snow Loading: 0.5 (std) & 0.0 (alt) Service Wind Loading: 0.4 (std) & -0.4 (alt)

64.2.14 Factored Wind LC: 1.25D + 0.5L+ 1.5S + 0.4W This load combination is intended for checking the strength limit state with applied wind and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.25 (std) & 0.9 (alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Live (Parking) Loading: 0.5 (std) & 0.0 (alt) Snow Loading: 1.5 (std) & 0.0 (alt) Service Wind Loading: 0.4 (std) & -0.4 (alt)

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Chapter 64

64.2.15 Factored Seismic LC: D + 0.5L+ 0.25S + E This load combination is intended for checking the strength limit state with applied seismic and live loads. The load factors used are: Hyperstatic Loading: 1.0 (std & alt) Dead Loading: 1.0 (std & alt) Live (Reducible) Loading: 0.5 (std) & 0.0 (alt) Live (Unreducible) Loading: 0.5 (std) & 0.0 (alt) Live (Storage) Loading: 1.0 (std) & 0.0 (alt) Live (Roof) Loading: 0.5 (std) & 0.0 (alt) Live (Parking) Loading: 0.5 (std) & 0.0 (alt) Snow Loading: 0.25 (std) & 0.0 (alt) Ultimate Seismic Loading: 1.0 (std) & -1.0 (alt)

64.3 CSA A23.3-04/NBC 2005 live load factors It is recommended that, in order to get the appropriate factors, you draw: • assembly loads less than 4.8 kPa (or important live loads) on a Live (Unreducible) layer • assembly loads of 4.8 kPa or more, manufacturing, retail stores, garages, or footbridge on Live (Parking) layer • storage areas, and equipment areas and service rooms referred to in Table 4.1.5.3 on Live (Storage) layer • live loads other than those covered by clause 4.1.5.9 sentences 1) and 2) on a Live (Reducible) layer

64.4 CSA A23.3-04 material behaviors This section explains how RAM Concept models the concrete, non-prestressed reinforcement and prestressed reinforcement when using CSA A23.3-04.

64.4.1 Concrete Behavior You define the concrete elastic modulus in the materials window. You can choose to use code equation 8.6.2.2 or a specified value. When you directly specify values, there must be two elastic modulus values: Eci = value for initial service (transfer) cross section analyses Ec = value for all other conditions When the CSA code equation 8.6.2.2 is selected the following values are used: γc  E c i = [ 3300 f ci + 6900 ]  ---------- 2300- E c = wc

628

1.5

33 f c

RAM Concept

Chapter 64 Where fci = cylinder strength at stressing (MPa) fc = 28 day cylinder strength (MPa) γc = density of concrete (kg/m3) For calculations based on the gross section, concrete is assumed to be a perfectly linear-elastic material with no stress or strain limits. For detailed cross section analyses the stress strain curves are described in “Concrete Stress-Strain Curves” on page 398 of Chapter 51, “Section Design Notes”. The strength stress-strain curves are truncated at a strain of 0.0035. The other stress-strain curves have no limit strain.



64.4.4 Unbonded Prestressed Reinforcement Behavior For service conditions, RAM Concept assumes that unbonded tendon stresses are not affected by cross section strains. For ultimate resistance moment calculations, RAM Concept’s general approach to unbonded tendon stress-strain curves is detailed in “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397 of Chapter 51, “Section Design Notes”. For CSA A23.3-04, the maximum unbonded tendon stress, flimit, is defined by equation 18-2. In the calculation of (dp-cy), RAM Concept assumes that the tendons are placed on the more beneficial side of the cross section centroid (the same limiting stress value is used for both positive and negative moment capacity calculations at each cross section).

64.5 CSA A23.3-04 code rule selection The following explains how RAM Concept decides which CSA A23.3-04 code rules to apply based on the design strip segment or design section properties, combined with the active design rules for the rule set under consideration.

64.5.1 Code Minimum Reinforcement • The structural system (as defined in the design section or design strip segment) is considered (beam, one-way slab, twoway slab). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The placement of the reinforcement is based on the “min. reinforcement location” selection for the design strip segment or design section: • Elevated Slab – Reinforcement is at top near supports and bottom near midspan. • Mat Foundation – Reinforcement is at bottom near supports and top near midspan.

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Chapter 64 • Tension Face – Reinforcement location is determined by the design moment envelope for the rule set (reinforcement may be required on both faces). • Top – Reinforcement is always located at the top of slab (Engineer discretion advised) • Bottom – Reinforcement is always located at the bottom of slab (Engineer discretion advised) • None – No reinforcement is provided (Engineer discretion advised) • Code Rules are applied as shown in the following table. Design System

RC

PT

Beam

10.5.1

18.7

One-Way Slab

7.8

18.7

Two-Way Slab

7.8

(none)








630

RAM Concept


RC

PT

Beam

(none)

18.3.1.1 and 18.3.1.3

One-Way Slab

(none)

18.3.1.1 and 18.3.1.3

Two-Way Slab

(none)

18.3.1.1 and 18.3.1.3


Note: 18.3.1.1(c) is not considered. 18.3.1.1(b) is considered in all cases for tension. 64.5.4 Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (reinforcement may be required on both faces). • The design strip segment or design section property “Environment” is used to determine the exposure category of members as follows: Protected: Partial PT/RC, interior exposure Normal: Partial PT/RC, exterior exposure Corrosive: Full PT, 18.3.2(c) Very Corrosive: Full PT, 18.3.2(d) • Code Rules are applied as shown in the following table. Design System RC

Partial PT

Full PT 18.3.2(c)

Full PT 18.3.2(d)

Beam

10.6.1

18.8.1, 18.8.3

18.8.1, 18.3.2(c)

18.8.1, 18.3.2(d)

One-Way Slab

10.6.1

18.8.1, 18.8.3

18.8.1, 18.3.2(c)

18.8.1, 18.3.2(d)

Two-Way Slab

(none)

(not applicable) 18.8.1, 18.3.2(d)

18.8.1, 18.3.2(d)


64.5.5 Sustained Service • Tendons are considered as an external load (and the balance loading is assumed to be included in the load factors). • The reinforcement type (as defined in the design section or design strip segment) is considered (PT or RC). • The stress levels in the structure are determined by the moment envelope for the rule set (failure could occur on both faces).

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631


RC

PT

Beam

(none)

18.3.2a

One-Way Slab

(none)

18.3.2a

Two-Way Slab

(none)

18.3.2a



RC

PT

Beam

10.1, 11.3*

18.6, 11.3*

One-Way Slab

10.1, 11.3*

18.6, 11.3*

Two-Way Slab

10.1, 11.3*

18.6, 11.3*



RC

PT

Beam

10.5.2

(none)

One-Way Slab

10.5.2

(none)

Two-Way Slab

10.5.2

(none)


632

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Chapter 64

64.6 CSA A23.3-04 code implementation

64.6.1 Section 7.8 Minimum Reinforcement in Slabs 7.8.1 and 7.8.3 are implemented. The gross area of concrete after taking into account the “ignore top depth” and the “ignore bottom depth” is used to determine the reinforcement specified in 7.8.1. The specified bar size is used to determine the required reinforcement for satisfying the maximum spacing in 7.8.3. The number of bars is not rounded up to the next whole number in this calculation, but will be rounded up to the next whole number in the reinforcement summary. User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations. In one-way slabs, a maximum spacing of 5h is utilized in accordance with 7.8.3. In “critical” span locations in two-way slabs, a maximum spacing of 2h is utilized in accordance with 13.10.4. For cantilever span (as determined by the declaration of supports in the design strip segment), the “critical” span locations are those within L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), the “critical” span locations are those within L/6 of a support or midspan location. For determining if the section is within the band defined by bb for the negative minimum reinforcement, the distance of 1.5 times the section height is compared with the distance to the nearest support face. In other span locations in two-way slabs, a maximum spacing of 5h is utilized. For the “elevated slab” and “mat foundation” minimum reinforcement patterns, an inflection point ratio of 0.2113 is assumed. Post-tensioning is ignored.

64.6.2 Section 10.1 Factored Moment Resistance Included code sections - 10.1, 10.3, 10.5, 10.6 Excluded code sections - 10.2, 10.4, 10.7 Strain compatibility design is used. Reinforcement areas are not deducted from the concrete area. See “Concrete Behavior” on page 628 for the material stress strain curves. φc = 0.65 for concrete; φs = 0.85 for reinforcement. Concept’s design may exceed the maximum amount of allowed reinforcement, and therefore may create an over-reinforced section. See “Ductility” on page 632 for more information on applying ductility requirements. For span segments or design sections not designated as “post-tensioned”, post-tensioning tendon forces are ignored. Axial forces (loads) on the section are either considered or ignored based on the settings in the design section of design strip segment under consideration. If axial forces are chosen to be included, the cross section is designed to provide the required moment simultaneously with the given axial force. At “T”, “L” and “Z” beams, the beam stem and flanges may have significant tension and compression forces (at different elevations) that are required for moment equilibrium. If a cross section crosses the entire beam, these forces will largely cancel (while increasing the bending moment). However, if a cross section extends only part way across a flanged beam, then the section may have significant axial forces that are required for moment equilibrium; designing for the axial loads (by selecting the appropriate design section or design strip segment properties) is necessary to ensure a safe design. User Es values are used

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Chapter 64 For sections with multiple values of fc’, the fc’ of each concrete block is used appropriately. For cross sections with very small moments, the amount of reinforcement calculated by Concept may exceed the amount necessary. This is because Concept will not allow cross sections to have strains greater than 20%, which would be necessary to create a smaller compression zone. The reinforcement Concept selects is that necessary for axial force equilibrium in the cross section. The shear and torsion tension forces are included in the flexural/axial design. In slabs, more longitudinal reinforcement than is required might be provided in order to eliminate the use of tranverse reinforcement. See “Section 11.3 Shear and Torsion Tension” on page 635 for additional information. For sections declared as “post-tensioned”, bonded tendon strains are calculated using strain compatiblity (see detailed description “Relationship of Bonded Post-tensioning Strains to Cross-Section Strains” on page 396. Unbonded tendon stresses are calculated using a strain reduction factor (see detailed description “Unbonded Post-tensioning Stress-Strain Curves – Program Implementation” on page 397). If a tendon is not perpendicular (in plan) to the cross section under consideration, then vector components of the cross section strains and the tendon stresses are used.

64.6.3 Section 10.5.1 Minimum Reinforcement in Beams (Non prestressed) 10.5.1.1 is implemented for beams, which considers the bending strength of the section designed to be at least 1.2Mcr. 10.5.1.3 is not considered. Post-tensioning is ignored.

64.6.4 Section 10.5.2 Redistribution of Moments - Ductility Check (Non prestressed) RAM Concept does not currently redistribute moments, but applies equation 10-5 as a limit to the neutral axis depth, thereby ensuring ductility. Although the current standard does not state an upper limit for the axial compression for ductility checks, a limit of 0.1Agfc’ is applied.

64.6.5 Section 10.6.1 Beams and One-way Slabs - Crack Control Equation 10-6 is implemented. A cracked section analysis is performed to calculate the stress in the reinforcement. Iteration is used to find the minimum number of bars thta meet the criteria. A non-integral number of bars may be used. The section width used to determine the spacing is the width of the extreme tension face. For beams with webs in tension, this will typically be the sum of the web widths. The spacing is considered as the tension face width divided by the number of bars. An additional bar is not added to make the width start and end with a bar. RAM Concept may use more reinforcement than “necessary” in two circumstances: • The reinforcement is necessary for equilibrium in the cracked section analysis • Compression reinforcement added later in the design process lowers the reinforcement demands

64.6.6 Section 10.5.1 Minimum Reinforcement of Flexural Members (Non Prestressed) Equation 10-3 and the 200 bwd/fy criteria are implemented. Equation 10-3 is calculated using the maximum fc', minimum fy, and maximum d (of all bars on the appropriate face). bw is taken the core width (see “Concrete “Core” Determination” on page 405). If the core width is zero (there is no core), then bw is taken as the width of the section. The bending strength of the section is designed to be at least 1.2 Mcr. This will only control in odd circumstances such as where the specified cover is extremely large.

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RAM Concept

Chapter 64 Post-tensioning is ignored. A spacing limit of 3h is utilized in accordance with 10.5.4. For typically sized beams, this limit will not control the amount of reinforcement. The provisions of section 10.5.2 are not implemented.

64.6.7 Section 10.6.1 Minimum Reinforcement of Flexural Members (Non Prestressed) Equation 10-6 is implemented A cracked section analysis is performed to calculate the stress in the reinforcement. Iteration is used to find the minimum number of bars that meets the criteria. A non-integral number of bars may be used. The section width used to determine the spacing is the width of the solid areas of the extreme tension face. For beams with stems in tension, this will typically be the sum of the stem widths. The spacing is considered as the width divided by the number of bars. An additional bar is not added to make the width start and end with a bar. Post-tensioning is ignored (except as it naturally affects the cracked section calculations). RAM Concept may use more reinforcement than “necessary” in two circumstances: • The reinforcement is necessary for equilibrium in the cracked section analysis. • Compression reinforcement added later in the design process lowers the reinforcement demands.

64.6.8 Section 11.3 Shear and Torsion Tension Included code sections - 11.3.9.2, 11.3.9.3, 11.3.9.5, 11.3.10.6 The longitudinal reinforcement is designed including the additional tension forces caused by shear and torsion in accordance with 11.3.9. The calculation is performed iteratively to find the strain at mid-depth of the cross section, εx using cracked section analysis. The shear tension is calculated using the shear terms of equations 11-14 and 11-15 and ignoring the vertical component of prestressing. The calculated tension forces are modified in accordance with clauses 11.3.9.4 and 11.3.9.5, using a full reduction at the face of support and linearly reducing it to 0 over a distance of dv cot θ. The distance dv is conservatively taken as 0.72h for this calculation. In continuous spans the shear tension forces are set to zero at the face of support in accordance with 11.3.9.4 while at the end of discontinous spans the calculated shear tension is applied at the location of the design bar on the tension face. Shear tension forces are combined with torsion tension forces using equation 11-21. In slabs, the design is performed to limit the strain at mid-depth εx to the maximum value that would not require transverse reinforcement. If transverse reinforcement is required, the design is performed such that εx is limited to 0.001. In the calculation of longitudinal strain εx , no material strength reduction factors are applied.

64.6.9 Section 11.3 Shear Resistance of Beams Included code sections - 11.2.8, 11.2.9, 11.2.10.2, 11.3.1, 11.3.3, 11.3.4, 11.3.5.1, 11.3.6.4, 11.3.8.1, 11.3.8.3, 11.3.10 Excluded code sections - 11.3.2, 11.3.5.2, 11.3.8.2 See “Concrete “Core” Determination” on page 405.

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Chapter 64 For sections with multiple values of f ’c, the minimum f ’c is used. In beams, transverse reinforcement consists of transverse reinforcement perpendicular to the axis of the member. General equation 11-4 is used for all cases but vertical component of effective prestress force (Vp) is conservatively not included in the calculations. In the determination of the effective concrete web width, the width of the shear core is considered, less the widths specified in accordance with 11.2.10.2. Lightweight concrete is considered. Minimum reinforcement is provided in accordance with 11.2.8 and equation 11-1. The effective depth for shear is taken as the greater of 0.9d or 0.72h, where d is the distance from the extreme compression fiber to the resultant tension force. The maximum spacing limits of 11.3.8.1 are applied. If “beam” torsion design is selected, see “Section 11.3 Torsion Design” on page 636

64.6.10 Section 11.3 Torsion Design Included code sections - 11.2.9.1, 6.3.2 Excluded code sections - 11.2.9.2 Only the “core” of a cross section is used for torsion design. See “Concrete “Core” Determination” on page 405. If the core consists of multiple ribs, then the torsion calculations are performed for an average rib: • rib width = total core width / num ribs • with ultimate forces scaled down by the number of ribs (/ num ribs) and capacity and reinforcement scaled back up by the number of ribs (* num ribs). • To get a more detailed and exact calculation, use a separate design section or design strip for each rib. The side cover is assumed to be equal to the greater of the top cover and the bottom cover. Torsion properties are calculated in accordance with 11.3.10. Torsion reinforcement consists of longitudinal reinforcement and closed ties perpendicular to the axis of the member according to 11.2.6(a). Acp and pcp only consider the cross section “core”. Ao is assumed to be equal to 0.85 Aoh per 11.3.6. 11.3.10.4 equation 11-19 is implemented such that the torsion demand reduces the shear capacity. For very high torsions, this can make the shear capacity negative. The longitudinal torsion tension demand is satisfied by calculating a torsion tension in accordance with equation 11-21, incorporating it with the shear tension and then adding these forces to the section forces and then performing a bending/axial desing in Pass 1. Transverse Reinforcement: • Transverse reinforcement is designed in Pass 2. • Stirrups/links are assumed to be closed hoops. RAM Concept will report the reinforcement in terms of the number of legs specified (by the user), but the calculations assume a hoop shape. The link detailing reported by RAM Concept will be difficult to decipher if the number of legs specified by the user is not 2. The area of transverse reinforcement is determined by equation 11-17.

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Chapter 64 Torsional and shear longitudinal reinforcement is considered along with other longitudinal reinforcement when determining effective depths and other bending parameters that affect shear design.

64.6.11 Chapter 13 (Two-way slab systems) With the exception of span detailing, this chapter is not used for reinforcement design calculations, specifically: Section 13.10.2 (Unbalanced moment transfer)


64.6.12 Section 18.3.1.1a Initial (at stressing) Compressive Stress Limit 0.6 f ’ci is the limiting value. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. No check is made to ensure that the structure is post-tensioned.

64.6.13 Section 18.3.1.1b Initial (at stressing) Tensile Stress Limit 0.25λ f′ ci is the limiting value. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported. The limiting stress is reported, but reinforcement per section 18.3.1.3 is added to resist the total tensile force if necessary, so no section will fail this criterion. User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered. No check is made to ensure that the structure is post-tensioned.


64.6.15 Section 18.3.2b Service Compressive Stress Limit 0.60 f ’c is the limiting value. Gross-section, linear-elastic stress calculations are used. For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported.

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Chapter 64 No check is made to ensure that the structure is post-tensioned.

64.6.16 Section 18.7 Cracking Moment For a cantilever span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is outside of L/3 of the support. For a regular span (as determined by the declaration of supports in the design strip segment), this criterion is ignored if the section location is in one of the two regions between L/6 and L/3 from a support. It is assumed that these regions will contain the peak moments and hence the first part of a span to crack; This criterion is not applied to two-way slabs. The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section. See ““Cracking Moment” Used in Design Calculations” on page 404 for a theoretical discussion of the cracking moment. Modulus of rupture (fcr) is 0.6λ f′c times the lightweight concrete factor. The maximum f ’c for the cross section is used.

64.6.17 Section 18.8.2 Minimum Bonded Reinforcement The minimum bonded reinforcement is provided in accordance with the following table.

Member Type

Tensile Stress

Tensile Stress

σ ≤ 0.5λ f c ′

σ > 0.5λ f c ′

Type of tendon

Type of tendon

Bonded

Unbonded

Bonded

Unbonded

Beam

0

0.004A

0.003A

0.005A

One-way slab

0

0.003A

0.002A

0.004A

Two-way negative moment regions

0

0.006hln

0.0045hln

0.0075hln

Two-way postitive moment regions >

0

0.004A

0.003A

0.005A

0

0

-

-

0.2λ f c ′ Two-way positive moment regions <

0.2λ f c ′ Table 64-7

For sections with multiple concrete strengths, the minimum concrete strength is used to determine the limiting stress. For sections with multiple concrete strengths, approximate extreme fiber stresses and centroid stresses are reported.

64.6.18 Section 18.8.3 Minimum Reinforcement of Flexural Members (Prestressed) Equation 10-6 is implemented A cracked section analysis is performed to calculate the stress in the reinforcement.

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Chapter 64 Iteration is used to find the minimum number of bars and bonded tendon ducts that meets the criteria. A non-integral number of bars may be used. The section width used to determine the spacing is the width of the solid areas of the extreme tension face. For beams with stems in tension, this will typically be the sum of the stem widths. The spacing is considered as the width divided by the number of bars and bonded tendon ducts. An additional bar is not added to make the width start and end with a bar. fs in bonded tendons is calculated as the difference between the stress in the bonded tendon due to the specified load moment and the decompression moment. RAM Concept may use more reinforcement than “necessary” in two circumstances: • The reinforcement is necessary for equilibrium in the cracked section analysis. • Compression reinforcement added later in the design process lowers the reinforcement demands. No check is made to ensure that the structure is post-tensioned. Reinforcing bar stresses are limited to the minimum of (0.5 fpy) and 30 ksi. No check is made to ensure that the structure is post-tensioned.


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65 Load History Deflections The calculation of concrete floor deflections is complicated. There are many issues to consider, and even with adequate consideration and calculation, any deflection prediction should only be considered an estimate. Deflections are affected by: • member size (section properties) • concrete modulus of elasticity • reinforcement (unstressed and post-tensioning) • applied loads • load history • cracking • shrinkage • creep • dynamic effects (vibrations) Historically, designers have usually calculated deflections of concrete members using elastic methods with modifications made for some of the factors listed above. Most post-tensioned floors have been designed to minimize cracking and so elastic deflection calculation methods have generally been acceptable. The increasing usage of partial prestress methods has made deflection calculations more important for post-tensioned design. Reinforced floors usually undergo more extensive cracking than post-tensioned floors, which is one reason why they need more concrete section, and more consideration of deflection issues. More aggressive designs (that is, with shallower or thinner concrete sections) require a more rigorous analysis to determine that the deflection limit states are satisfactory. The aggressive designer must, however, have a thorough understanding of the methods and issues to ensure satisfactory deflections. In particular, if the designer pushes the floor design “to the limit” then problems may occur due to issues that are unforeseen or not considered by Concept. These include: • poor placement of reinforcement (less effective depth resulting in more cracking) • vibrations (dynamic effects are not considered by Concept)

65.1 About RAM Concept’s load history deflection calculations RAM Concept analyzes the concrete floor using a linear elastic global analysis. All deflection contour plans are representative of the linear elastic analysis and the particular load combination’s std load factors. The load history deflection calculations perform detailed calculations on the cross sections including the effects of cracking, creep, shrinkage, tension stiffening, and load history and then uses the results to modify the element stiffness in the linear elastic global analysis to calculate deflection contours considering the various effects. Dynamic effects are not considered. In order to calculate load history deflections the load history must first be specified by the user. This is done in the “Load History” criteria page.

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Each load history step represents an applied load combination for a specified duration of time. Each load history step is solved in sequence, taking into consideration the effects from all previous load history steps. For instantaneous load steps the duration can be specified as zero. The specified sequence of load steps makes up the entire load history. The total age at the end of each load history step is reported as a read only value in the table. In order to calculate load history results, span segments and design sections must be specified such that each finite element with significant stress is covered by the tributary of a design strip cross section or design section oriented appropriately for the element stress. For one-way slabs, this could be achieved by defining span segments in the spanning direction only. For two-way slabs, span segments should be specified in orthogonal directions to cover the entire slab. Since the load history deflection detailed calculations are carried out on the cross sections and subsequently used to adjust element stiffness, omission of span segments or design sections in highly stressed regions will result in an inaccurate and potentially unconservative prediction of deflections. RAM Concept’s load history deflection calculations do not directly consider the effects from specified patterns, from live load reduction, or from alternate load factors. Since the load history calculations can be time consuming, they are performed separately from other calculations in RAM Concept. They are invoked using the Calc Load History Deflections ( ) command. The button will only be active if load steps are specified in the Load History criteria page and if the current load history results are out of date.

Results The results for each load history step are available in the load history folder on the report tree. The results stored on each load history step represent the state of the structure at the end of the load history step. Additional load history steps can be added at any desired interval in order to calcuate results at any particular age of interest.

65.2 The load history deflection calculation process Load history deflections are calculated using a mult-step process summarized below. For each load history step, the process is performed separately for the instaneous change in loads at the beginning of the load history step and the sustained changes over the duration of the load history step, in which the loads are assumed to remain constant: 1 Solve cross section forces 2 For each cross section, calculate curvatures including long term effects and prior load history:

• Gross cross section curvature (using gross section properties) • Uncracked cross section curvature (using uncracked transformed section properties) • Cracked cross section curvature (using cracked transformed section properties) • Creep cross section curvature (takes into account cracking history of the cross section) 3 Using the calculated curvatures and the tension stiffening model, calculate an “average” curvature for each cross section. 4 For each element in the structure, use the average calculated curvatures for the tributary cross sections to set stiffness

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Chapter 65 5 Re-analyze the structure with the adjusted element stiffnesses and check for convergence. Convergence is measured by the

deflection difference between two iterations as measured at a key node. 6 Repeat 1-5 for each load history step until convergence.

65.3 Load history calculations on the cross section Load history deflections utilize detailed time-dependent curvature calculations on the cross section. Influence of creep, shrinkage, cracking, and load history effects are included. Additional information on the detailed cross section calculations was presented by Hirsch [Hirsch, J.,“Accurate Long-Term Deflection Prediction in Flat Slabs Using Linear Elastic Global Analysis”, 24th Biennial Conference of the Concrete Institute of Australia, Sydney, Australia, 2009, 11 pp.].

65.3.1 Material Stress Strain Curves Generally the service level material stress-strain curves for concrete, reinforcement, and post-tensioning are utilized in the load history deflection calculations. The concrete stress-strain curves designated in the IS 456 and EC2 standards are not dependent upon the modulus of elasticity of the concrete. Since this a desirable attribute in deflection calculations and the user may want to define a custom modulus of elasticity that will be taken into account in the load history calculations, the PCA concrete stress-strain curve in the section “Concrete Stress-Strain Curves” on page 398 is utilized in the load history calculations for these standards.

65.3.2 Creep Creep strains occur over time and a number of models are available to predict the percentage of total creep as a function of time. The creep model presented in ACI 209R-92 is utilized in RAM Concept’s load history calculations. The creep value input in the Load History / ECR tab of the Calc Options dialog should represent the final ultimate creep value and should take into account concrete mix, environmental considerations, etc. and can reflect any considerations required by regional building codes. The ACI model is only used to predict the percentage of total creep as a function of time. The modification factor γla to account for initial load application times other than 7 days is automatically included in RAM Concept’s load history calculations and should not be incorporated into the input creep value. Creep strains are assumed to be a linear factor of the initial load induced elastic strain for a particular load. In order to consider loads that are applied at different times, the assumption is made that creep strains of like or opposing signs can be superimposed. These assumptions are likely reasonable for the normal range of service loads. An ageing coefficient χ is used as a modifier of creep to account for the rate of application loading, its effect on the creep and the variation of concrete strength over the time period. While the rigorous calculation of the coefficient is rather involved, this value can normally be taken as 0.8 with little loss in accuracy.

65.3.3 Shrinkage Shrinkage strains occur over time and a number of models are available to predict the percentage of total shrinkage as a function of time. The shrinkage model presented in ACI 209R-92 for moist curing is utilized in RAM Concept’s load history calculations. The shrinkage value input in the Load History / ECR tab of the Calc Options dialog should represent the final ultimate shrinkage and should take into account concrete mix, environmental considerations, etc. and can reflect any considerations required by regional building codes. The ACI model is only used to predict the percentage of total shrinkage as a function of time. The modification factor γcp to account for moist curing durations other than 7 days is automatically included in RAM Concept’s load history calculations and should not be incorporated into the input shrinkage value.

65.3.4 Cracking When a flexural load or shrinkage causes the applied tensile stresses to exceed the cracking stress, the stress is relieved at that location and a redistribution of stress occurs with a resulting increase in cross section curvature. As load increases, the

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Chapter 65 number of cracks also increases. In the cross section calculations, at the crack locations the concrete is assumed to carry no tension. In the regions between the cracks the bonded tension reinforcement transfers tension back into the concrete. This phenomenon is normally referred to as tension stiffening. In a partially cracked concrete member the mean curvature over a region lies between the uncracked curvature and the curvature at the crack locations. A number of models exist for predicting the tension stiffening behavior. The tension stiffening model presented in the Eurocode 2-2004 is utilized in RAM Concept’s load history calculations utilizing a long term β factor. See “Eurocode 2 Cracking Distribution Stress Ratio” on page 401 for additional information. The modulus of rupture for the design Code in use is used for the concrete flexural tension strength in the tension stiffening equation. In general, external restraint to shrinkage shortening can increase the cracking in the floor, thus increasing deflections. Failure to account for this effect can result in underestimation of deflection values. A crude means of accounting for this is through the “Shrinkage Restraint %” value in the Load History / ECR tab of the Calc Options dialog. This percentage is multiplied by the input free shrinkage strain value (as a function of time) to determine a hypothetical tension strain. This hypothetical tension strain is combined with the load induced strains which is then used to determine a hypothetical tension stress from the concrete stress strain curve. This hypothetical tension stress is used in the tension stiffening calculation. These stresses are not used in the cross section curvature calculations. As such, increasing this percentage will generally increase the amount of cracking predicted and used in the tension stiffening interpolation, but will not affect the calculated curvatures directly.

65.3.5 Load History The tension stiffening model generally predicts the response for instantaneous loads, so some extensions are necessary to account for the effects of the load history on the member. • Creep and shrinkage strains are included in the calculated uncracked and cracked cross section curvatures. • Creep strains for the cracked curvature calculations consider the actual cracking history of the cross section. • While calculating cracked section curvatures, creep is only applied to portions of strain change in compression. • Once a cross section is determined to be cracked during a particular load history step iteration, it is assumed to be cracked for all future iterations and load history steps. • The mean curvature calculated for any loading level is assumed to be proportional to the mean curvature calculated at the peak loading level.

65.4 Element stiffness adjustments The element stiffness in a particular iteration is adjusted based upon the influence of the cross sections (from either design sections or span segment strips) that have tributaries that intersect the element. In the instance where multiple cross sections cover an element at various angles, a weighted average and vector components squared of each cross section is used to determine the cross section’s influence on the element stiffness. The axial and flexural element stiffness for each element in the model is adjusted based upon the ratio of the calculated gross curvature to the calculated mean curvature. For most normal situations, it will be possible to calculate equilibrium for the mean curvature and for cross section curvatures predominately caused by loading the gross and mean curvatures will have the same sign. Unusual cases are handled as follows: • For the case where equilibrium cannot be achieved in a cross section calculation, a warning is logged in the calc log and the mean curvature is set to be 50 times the gross curvature. This is normally caused by inadequate reinforcement specified in the cross section without performing design, or an unexpected load combination is selected. This can sometimes occur as a normal part of the calculation process, where cracking in a highly stresses region shifts force to a less stressed region that does not have enough reinforcement to achieve equilibrium. In this case, this “softening” will effectively shift load back to the region that is designed to take it, and will predict both locations to be cracked. • For the case where the mean curvature is opposite in sign from the gross curvature, the mean curvature is set to be 2 times the gross curvature. This will normally be caused by shrinkage strains larger in magnitude than the load induced strains, often times in regions of low bending. As a result, this modification will many times have little effect on the deflection calculations. No warning is issued for this situation. 644

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65.5 Why are load history deflection results different from Long Term Deflection results plotted for the strip? Because the methodology is entirely different, the results between the load history calculations will sometimes differ from the long-term deflections plotted on the strip. It is common for the load history deflections to be larger or smaller than the strip based long-term deflections. Some of the primary differences are outlined here. Several aspects of load history deflections that can cause them to be larger than strip based long-term deflections are: • Redistribution of forces is considered, which can lead to a more realistic prediction of cracking in the structure. Cracking in one region can lead to increased forces in adjacent regions (either laterally or along the span) which can in turn lead to additional cracking throughout the structure. • Stresses induced in the uncracked concrete due to shrinkage being restrained by the reinforcement or by specifying a Shrinkage Restraint % are considered in the cracking and tension stiffening calculations. Several aspects of load history deflections that can cause them to be smaller than strip based long-term deflections are: • Compression reinforcement is always considered, whether the cross section is actually cracked or not. Uncracked transformed properties are used where the cross section is not cracked. • Load history is taken into consideration. If the maximum load is not sustained through the duration of the calculation, the load history calculations will take this into consideration.

65.6 Advice on drawing cross sections In order to get good deflection predictions, it is necessary to define reasonable cross sections. This includes defining cross sections that cover all regions of significant stress. Cross sections can be defined by drawing span segments and generating span segment strips or by drawing design sections. When drawing design sections it is important to pay attention to the “tributary length” property to ensure proper element coverage. It is also advisable in structures that are cracking sensitive (like RC structures) to define cross sections that are not too wide in regions of steep moment gradient. An example of recommended usage would be using column and middle strips in a reinforced concrete two-way slab. Making the cross sections too wide could, due to stress averaging, cause the cracking prediction for the cross section to be unconservative and result in underestimation of deflections. Another example is cross sections with significant axial forces due to bending caused by eccentric element stiffness. For example, a T beam with separate cross sections for the web and the flanges. In this case, a large portion of the bending behavior will be captured through eccentric axial forces in the cross sections. However, since RAM Concept’s load history calculations rely on cross section curvatures and not axial strains to make element stiffness adjustments, this portion of the bending behavior will not be captured in the load history analysis. This will generally result in an underestimation of deflections. Therefore, drawing spans and cross sections in this manner is highly discouraged. A good approach is to utilize a reasonable effective flange in the T beam cross section, which will minimize the axial forces on the cross sections due to bending. One way to accomplish this is to select Code T-beam for the Column Strip Width Calc of the Span Segment.

65.7 A final word of caution Due to the unpredictable nature and variability of early age shrinkage and cracking, it is not possible to accurately estimate deflections in the early ages (30-90 days). As such, load history deflection results for ages less than 90 days should be used with extreme caution. When evaluating differential deflections between long-term deflections and early age deflections (such as at time of installation of partitions), a generally conservative approach could be to compare the long-term load history deflections with the deflection results for the load combination (linear elastic results) in place at time of application of partitions (which would not include the effects of shrinkage, creep, and cracking).

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Additionally, deflection calculations can be somewhat sensitive to finite element mesh size. For best results using load history calculations, at least 12 elements per bay are recommended with a cross section spacing approximately equal to the resulting element size.

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Chapter 66

66 Punching Shear Design Notes Ensuring that a slab will not fail in punching shear is one of the most important tasks in slab design. This chapter gives an overview of punching shear design and advice on using RAM Concept’s punching shear design capabilities.

66.1 Punching shear overview

66.1.1 What is a “punching shear” failure? Large support reactions (or any load) applied over a small area of a slab can cause the slab to fail near the perimeter of the support in shear-like failure. This “punching shear” is different from “beam shear” because the failure location is around a perimeter instead of along a line across the slab. Bending moment reactions applied along with the reaction force tend to lower the amount of load that can be supported without a punching failure. Local thickenings of a slab may increase the punching shear resistance, or may just move the punching shear failure location to a perimeter outside of the thickened area. Punching shear failures are usually brittle and sudden.

66.1.2 How are forces really transferred in a punching zone? The transfer of forces in a punching zone is extremely complex, and the load path changes with increased cracking in the zone. There are no simple general models to predict the behavior of the punching zone. Three-dimensional truss behavior is probably the simplest model that can be applied to a punching zone, but even this model is too complex for design purposes.

66.1.3 How do the building codes handle punching shear? All building codes approach punching shear by replacing the actual complicated punching behavior by relatively simple models that do not reflect the actual behavior of the punching zone. The only reason that these simple models lead to safe designs is that they have been calibrated with test results for the standard interior, edge and corner column cases. It should always be remembered that for situations other than the standard interior, edge and corner cases, the building code models might produce results that are illogical and possibly unsafe.

66.2 How does RAM Concept handle punching shear? In RAM Concept, any slab-column connection can be designed for punching shear considerations. Concept performs the following steps in the analysis and design of a slab-column connection for punching shear:

66.2.1 Step 1: Determine the force envelopes to be checked Concept uses envelopes of the reactions on the column to calculate the force envelopes for determining the critical case. The forces are enveloped about the punch check axes and the following cases are considered: Max Fz, Min Fz, Max M r, Min Mr, Max Ms, Min Ms. The controlling envelope can be displayed by checking “controlling criteria” in the visible objects menu under “Punching Checks” on any plan that displays the Rule Set Design Layers or Design Status Layer. Loads applied inside the critical sections

Any loads that are applied within the critical section shape could be excluded from the punching reaction since they do not contribute to the forces passing through the critical section. Concept calculates the punching reaction by summing the column above and below reactions with any point loads applied within the column shape. The column shape is used for this

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Chapter 66 calculation (instead of the critical section shape) as it guarantees a single set of punching reactions for each punching check. Line and area loads are not considered in this summation. Punching Reactions for Lateral SE Loads

Loads of analysis type Lateral SE are appropriately included in the punching reactions. These loads are typically applied at the column/wall locations and normally consist of at least an applied out of plane concentrated force with a set of orthogonally applied moments. These forces typically represent the total joint forces applied from the supports to the slab for the given lateral loading. The correct punching reaction for this type of loading is simply the loading itself. Since Concept internally removes the column and wall supports in the Lateral SE loading analysis, the resulting punching reaction will be the summation of any loads applied within the column shape. Contribution from the Vertical Component of Prestress

Some building codes allow the vertical component of prestress to be considered in the punching calculations. This is normally accomplished by adding the contribution of the vertical prestress to the capacity at the critical section, or by subtracting the vertical prestress component from the punching reaction. Concept can approximate this effect using the Calc Option Include Tendon Component in Punch Check Reaction. If this option is selected, after the tendons have been converted into equivalent concentrated balance loads Concept will modify (normally reduce) the punching reaction by any concentrated forces located within the column shape.

Note: Due to the fact that the tendons are idealized as concentrated balance forces as well as the fact that Concept uses the column shape instead of the critical section shape, this calculation is approximate. When using this option, it is extremely important to make sure that the Concept model tendon plan locations and profile shapes match the final design and field placement in order to obtain accurate results. As such, this option should be used with extreme caution.

66.2.2 Step 2: Determine the “column” critical sections Concept investigates the slab geometry within the punching zone radius specified to find likely failure locations. Concept’s critical section calculations correctly consider slab thicknesses, but make simplifying assumptions about the elevations of the slab regions. In certain situations this can result in improper location of critical sections. In areas of varying thickness, Concept's punching calculations assume that the thickenings protrude toward the load application. For example, in an elevated slab shear caps are assumed to be located below the slab, and in a mat/raft foundation plinths are assumed to be located above the mat/raft. If this is not the case, Concept may not locate the critical sections appropriately. See the example in Figure 66-1.

C

Analyzed correctly

B

A

Concept considers failure planes A and C, but should consider A and B

Figure 66-1 Shortcoming of Concept’s consideration of failure planes

The location at some distance (usually a function of effective depth “d”) from the face of the column is considered to be a likely failure area. The location at some distance from a change in section thickness is also considered to be a likely failure area. If the slab edge/hole treatment is set to Sector Voids, then any slab edge or hole found within the punching zone radius creates a sector or zone that offers no resistance to punching.

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Chapter 66 If the slab edge/hole treatment is set to Failure Planes, then Concept investigates a number of critical sections including sections that connect to edges or openings (which provide no punching resistance) in attempts to find the most critical section. If the slab edge/hole treatment is set to Ignore Edges, then the location of the critical sections is not affected by the holes, but any part of a section intersecting a hole will be considered to provide no punching resistance. It is recommended that Ignore Edges is only used if the Sector Voids and Failure Planes treatments do not produce desired critical sections.

Figure 66-2 Failure plane results for the three different slab edge / hole treatments

Concept tries to connect the likely failure locations together to determine logical potentially critical sections. The method that Concept uses tends to find the appropriate sections, but does not always find them. You should always visually inspect the locations of the critical sections that Concept has checked to see if they are appropriate (this is usually accomplished by a simple visual review of the Design Status: Punching Shear Status Plan).

66.2.3 Step 3: Determine the code-model stresses on the column sections Please refer to the specific code section for the description of the code model and calculation of punching demand.

66.2.4 Step 4: Determine the code-allowable stresses on the column sections Please refer to the specific code section for the description of the calculation of punching capacity in accordance with the code model.

66.2.5 Step 5: Design stud shear reinforcement (SSR) if necessary If any of the calculated column critical sections have a higher demand than capacity (and thus unreinforced stress ratio (USR) > 1.0), the user may choose to have Concept design SSR to strengthen the column, if possible. This is done by selecting the “Design SSR if necessary” option on the punch check properties. The SSR design is carried out on any sections with an USR > 1.0: 1 Check the maximum section stress against the allowable maximum stress - some codes use this provision to prevent highly

stressed sections from being reinforced. Please refer to the specific Code section for a detailed description of how each handles this check. 2 Install Initial Rails - some initial rails are installed with an arbitrary length. The initial rails are installed to satisfy the

maximum transverse spacing requirement of the active Code at the face of the column or support. 3 Extend the Rails - the rails are iteratively extended until all cutoff section stresses are within the Code-allowable stresses

for unreinforced sections. A cutoff section is one at the Code specified offset distance outside the zone reinforced with SSR.

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Chapter 66 4 Check the calculated/designed stud spacing resulting from the current rail layout. If the spacing doesn't work, rails are

added and the design is restarted at step 2.

Note: In punch checks containing slab edges, it is possible for Concept to extend the rails to a distance within the punch check radius, but points projected perpendicular to the slab edge would be outside the punch check radius. In this case Concept may not find the most critical cutoff sections. This can normally be rectified by increasing the punch check radius. The Engineer should inspect cutoff sections for appropriateness and adjust punch check properties as necessary.

66.2.6 Step 6: Summarize the Results Finally, the results are summarized. Direct summarizing of SSR designs is not possible for a number of reasons (for example, two independent designs might have rails of different lengths, and therefore different depths which would dictate a different stud spacing). Therefore, if more than one design rule specifies punching shear design, the force envelopes from each design rule are combined into a single force envelope, then a summary design is carried out for this combined force envelope as outlined above. For each resulting critical section the calculated stress is divided by the code allowable stress to determine an unreinforced stress ratio (USR). If the column contains SSR reinforcement, Concept also reports a reinforced strength ratio (RSR), which is the punching demand over the strengthened capacity. If one or more of the potentially critical sections does not fit the standard conditions, then the column is tagged with a Nonstandard Section label in which case the engineer should review the applicability of the code design equations to the critical section labeled nonstandard.

66.3 Using Concept's results to specify stud shear reinforcement (SSR) systems Typical values specified for an SSR System include number and arrangement of rails at the column or support, first stud spacing, typical stud spacing, stud diameter, and rail height in addition to the typical stud properties. Most of the properties required to specify an SSR System are available by plotting the SSR under visible objects > Punch Checks. The overall height of the rails is not reported by Concept but can be easily determined from the geometry. Generally, the height of the rails should be dimensioned to be as close as possible to the structural member's outer surfaces (while observing necessary cover and other Code requirements). Concept's strength calculations assume that each individual shear stud rail has a single effective depth, calculated as the thinnest effective depth of any slab area intersected by the shear stud rail. A punching design may have shear stud rails with multiple depths at a column or support. For the Ancon Shearfix system design, the input covers are used to calculate a physical rail depth and used to generate the Ancon part numbers shown in the punching report.

66.4 Column connection type RAM Concept calculates the allowable shear stress for each potentially critical section based on the applicable code equations. The allowable stresses are dependent upon the column connection type.

Note: Column connection type is not used in AS3600. 66.4.1 About Connection Type Concept determines whether a column is “interior”, “edge” or “corner” based on the Connection Type property of the punching check. If the connection type property is set to Auto, then Concept assigns a connection type. Concept attempts to determine the connection type using the total angle of voids within a punching check radius. A void angle is defined as the angle between tangent lines to any void contained within the punching check, or the angle between the intersection points of slab edges and the punching check perimeter.

650

RAM Concept

Chapter 66 Concept assigns the connections as follows: • if the total angle of the voids is greater than 180 degrees: corner • if the total angle of the voids is less than 180, but greater than 90 degrees: edge • otherwise: interior Due to the possible complex geometries, Concept will not always assign the appropriate connection type, so we advise you to use discretion when using the “Auto” setting. The connection type assigned by Concept can be viewed on a plan by checking the “Column Condition” box under “Punching checks” on any plan that displays Rule Set Design Layers, or the Design Status Layer. For connections that don't neatly fit into one of the categories, it is conservative to select an option that has more slab edges (i.e., if a connection appears to be somewhere between an edge and a corner, it is conservative to select “corner” for connection type).

66.5 ACI 318/CSA A23.3 Punching Shear Design The ACI/CSA Punching Shear Model

The ACI/CSA punching shear analysis and design approach uses the ACI 318 or CSA A23.3 provisions for the basis of the implementation. A critical section is defined at d/2 from the periphery of the area of application of force. These critical sections are arranged to minimize bod. For slab edges located within the punching check, additional critical sections will be generated by projecting perpendicular lines from the original section to the slab edges. Additionally, a set of sections will be generated for each basic slab shape (column, drop cap, etc.). Maximum overhang (from the originating shape) can be limited as a function of d as specified by the user. For ACI by default no limit is used. For CSA A23.3 the limit is 1.0d in accordance with clause 13.3.3.3. To calculate the section stresses, an elastic distribution of stresses caused by the eccentricity between the load/reaction and the critical section centroid is superimposed with the shear stresses caused by the concentric loading to calculate a linearly varying stress distribution on the section. Where there are eccentricities in two orthogonal directions, they are considered simultaneously. γ v for each section is calculated about the principal axes for that section. For column sections, the length/width ratios used to calculate γ v are unmodified. For cutoff sections, the length/width ratios are modified in accordance with ACI 421.1R99.

66.5.1 Calculation of punching resistance for the unreinforced section This section discusses the calculation of punching resistance for an unreinforced section. Critical section properties and equations for the calculation of actual stresses Notation

A = area of one side of the critical section, in2 bo = total length of the critical section, in. b1 = width of the critical section measured in the direction of the span for which moments are determined, in. b2 = width of the critical section measured in the direction perpendicular to b1, in. d = distance from extreme compression fiber to centroid of longitudinal tension reinforcement, as outlined in ACI 318, in. Ixx = moment of inertia for bending about the x-axis for the entire critical section, in4

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Chapter 66 Ixx = moment of inertia contribution about the x-axis for an individual side of the critical section, calculated with respect to the centroid of the critical section, in4 Iyy = moment of inertia for bending about the y-axis for the entire critical section, in4 Iyy = moment of inertia contribution about the y-axis for an individual side of the critical section, calculated with respect to the centroid of the critical section, in4 Ixy = product of inertia for the entire critical section, in4 Ixy = product of inertia contribution for an individual side of the critical section, calculated with respect to the centroid of the critical section, in4 L = length of one side of the critical section, in. Mox = joint reaction (moments from columns above and below) about the x-axis at the centroid of the column utilizing a “right-hand rule” for sign convention, kip-in Moy = Joint reaction (moments from columns above and below) about the y-axis at the centroid of the column utilizing a “right-hand rule” for sign convention, kip-in Mux =

column reaction, moment about the x-axis at the centroid of the critical section, kip-in

Muy =

column reaction, moment about the y-axis at the centroid of the critical section, kip-in

vu =

shear stress located at some point on the critical section, ksi

Vu =

axial column reaction, located at the centroid of the column with an upward column reaction being positive, kips

x = x-coordinate of the centroid of the entire critical section, in. xside = x-coordinate of the centroid of a side of the critical section, in. xcol = x-coordinate of the centroid of the column, in. xpoint = x-coordinate of the point at which you are calculating stresses, in. y = y-coordinate of the centroid of the entire critical section, in. yside = y-coordinate of the centroid of a side of the critical section, in. ycol = y-coordinate of the centroid of the column, in. ypoint = y-coordinate of the point at which you are calculating stresses, in. γ vx = fraction of unbalanced moment about the x-axis transferred by eccentricity of shear, in accordance with ACI 318 γ vy =

fraction of unbalanced moment about the y-axis transferred by eccentricity of shear, in accordance with ACI 318

θ = angle between a side of the critical section and the positive x-axis Equations for calculation of shear stress

The equations presented are derived from basic mechanics of materials. A similar formulation can be found in the article “Design of Stud Shear Reinforcement for Slabs” by Ghali & Elgabry, ACI Structural Journal, May-June 1990. The values of γ vx and γ vy are always calculated about the principal axes of the critical section.

652

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Chapter 66

vu =

a) −

(x

(

)[

y po int − y ⋅ γ vx ⋅ M ux ⋅ Iyy + γ vy ⋅ M uy ⋅ I xy Vu + 2 bo d I xx I yy − I xy

)[

− x ⋅ γ vy ⋅ M uy ⋅ Ixx + γ vx ⋅ M ux ⋅ I xy

po int

I xx I yy − I xy

]

]

2

b) M ux = M ox + Vu ⋅ ( ycol − y )

c) M uy = M oy − Vu ⋅ ( xcol − x )

d) I xx =

e) I = yy

n

∑I

xx

sides =1

n

∑I

yy

sides =1

f) I = xy

n

∑I

xy

sides =1

3 g) I = dL (sin 2 θ ) + Ld ( y − y ) 2 xx side 12

3 h) I = dL (cos 2 θ ) + Ld ( x − x ) 2 yy side 12

3

i) I = dL (sin θ ⋅ cos θ ) + Ld ( x − x )( y − y ) xy side side 12

j)

γ v = 1−

1 2 b1 1+ 3 b2

Note: Equation a) is based upon standard strength of materials equations for bending in an asymmetric section. If the moments are applied about one or more axis of symmetry, then Ixy = 0 and equation a) reduces to the more familiar:

vu =

Vu γ vx ⋅ M ux ⋅ ( y po int − y ) γ vy ⋅ M uy ⋅ ( x po int − x ) + − bo d Ix Iy

ACI 318 equations for calculation of allowable shear stress

The allowable shear stress is calculated by selecting the appropriate equation from ACI-318 (11-33), (11-34), (11-35), or (11-36). Equation 11-33 controls in non-prestressed concrete zones with large column aspect ratios. As the aspect ratio of the column gets larger, the allowable punching shear stress approaches the allowable one-way shear stress.

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Chapter 66 Equation 11-34 is intended to correlate the allowable shear stress in non-prestressed zones with the ratio bo/d. This equation generally controls in thinner slabs with large columns or at critical sections outside column caps. ′

Equation 11-35 is the upper bound of allowable shear stress for non-prestressed zones, 4 f c . Equation 11-36 is for application to prestressed punching zones. In order to qualify as prestressed, a zone must meet the following criterion: 1 The effective prestress, fpc at the column shall not be less than 125 psi. The effective prestress is calculated by averaging

the precompression in all the elements within the punching check radius. This could result in non-prestressed equations being used in drop caps of prestressed slabs where the precompression drops below 125 psi in the cap. Additionally, if large restraining elements are used (i.e., shear walls) that divert the prestressing force in a region, the non-prestressed equations would correctly be used where the average precompression is below 125 psi. 2 f’c shall not be taken greater than 5000 psi. If a concrete strength is input greater than 5000 psi, a maximum f’c of 5000 psi

will be used in prestressed punching zones, but the allowable shear stress will still be calculated using equation 11-36. 3 The column must not be located near a slab edge or large opening.

If any of the above conditions are not met, equations 11-33 through 11-35 are applied. For the ACI 318-08 and ACI 318-11 standards, lightweight concrete is considered.

Note: These equation numbers are from the ACI 318-02 and ACI 318-05 standards. ACI 318 Maximum Reinforced Section Stress

The reinforced shear stresses vu on the column sections are limited to a maximum of φv n , where vn = 6 f′c per ACI 31805 11.12.3.2. This limit can be raised to vn = 8 f′c by using the suggestion in ACI 421.1R-99 of a higher limit for vn. The higher limit is also applied to all sections in the ACI 318-08 and ACI 318-11 standards. Sections with unreinforced stresses larger than these values cannot be successfully reinforced with SSR. ACI 318 Calculation of Punching Resistance with SSR

Where SSR is used the punching resistance is calculated as follows: vn = vc + vs

(11-2)

where v c = 2 f′c

(11.12.3.1 ACI 318-99, ACI 318-02, ACI 318-05)

or v c = 3 f′c vs = Av fyvdaveRail / (bosd)

(ACI 318-08, 318-11, ACI 421.1R-99 suggestion for higher vc) (11-15)

Note: This equation has been extended from ACI equation 11-15 to approximately account for the situation where different rails at a column have different heights due to geometrical irregularities. Av = area in one peripheral line of stud shear reinforcement daveRail = the average effective depth of the slab containing the rails vs,min = 2 f′c

654

(11.11.5.1 ACI 318-08, ACI 318-11)

RAM Concept

Chapter 66 ACI 318 Miscellaneous Provisions

The spacing to the first stud is calculated as 0.4 d in accordance with ACI 421.1R-99 equation 3.12. This spacing is rounded down to the nearest 1/8 in. for US units or 5 mm for metric units. The maximum typical stud spacing for ACI 318-99, ACI 318-02, and ACI 318-05 is 0.5 d, but can be increased to 0.75 d when v u ⁄ φ is less than or equal to 6 f′c by using the suggestion in ACI 421.1R-99 for a higher limit for spacing. The maximum typical stud spacing for ACI 318-08 and ACI 318-11 is 0.75 d when v u ⁄ φ is less than or equal to 6 f′c and 0.5 d otherwise. The maximum tangential spacing of rails at the face of the column is limited to 2d in accordance with ACI 421.1R-99 appendix A.2 and ACI 318-02 11.12.3.3. Tangential spacing requirements are not checked at locations other than the face of the column/support. The SSR is extended until the cutoff section stresses are within the allowable limit of 2 f′c per ACI 318-02 11.12.6.2(b). For cutoff sections outside the original column perimeter sections, γ v is adjusted in accordance with ACI 421.1R-99 Appendix B. CSA A23.3 equations for calculation of allowable shear stress

The allowable shear stress is calculated by selecting the appropriate equation from CSA A23.3 (13-5), (13-6), (13-7), or (185). Equation 13-5 controls in non-prestressed concrete zones with large column aspect ratios. As the aspect ratio of the column gets larger, the allowable punching shear stress approaches the allowable one-way shear stress. Equation 13-6 is intended to correlate the allowable shear stress in non-prestressed zones with the ratio bo/d. This equation generally controls in thinner slabs with large columns or at critical sections outside column caps. Equation 13-7 is the upper bound of allowable shear stress for non-prestressed zones. Equation 18-5 is for application to prestressed punching zones. In order to qualify as prestressed, a zone must meet the following criterion: 1 The effective prestress, fpc at the column shall not be less than 0.8 MPa. The effective prestress is calculated by averaging

the precompression in all the elements within the punching check radius. This could result in non-prestressed equations being used in drop caps of prestressed slabs where the precompression drops below 0.8 MPa in the cap. Additionally, if large restraining elements are used (i.e., shear walls) that divert the prestressing force in a region, the non-prestressed equations would correctly be used where the average precompression is below 0.8 MPa. 2 The column must not be located near a slab edge or large opening.

If any of the above conditions are not met, equations 13-5 through 13-7 are applied. CSA A23.3 Maximum Reinforced Section Stress

The reinforced shear stresses on the column sections are limited to a maximum of 0.75λφ c f′c per CSA A23.3 13.3.8.2. CSA A23.3 Calculation of Punching Resistance with SSR

Where SSR is used the punching resistance is calculated as follows: vr = vc + vs

(13.3.7.3)

where v c = 0.28λφ c f′c

(13.3.8.3)

and

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Chapter 66 vs = φsAvs fyvdaveRail / (bosd)

(13-11)

Note: This equation has been extended from CSA equation 13-11 to approximately account for the situation where different rails at a column have different heights due to geometrical irregularities. Avs = area in one peripheral line of stud shear reinforcement daveRail = the average effective depth of the slab containing the rails CSA A23.3 Miscellaneous Provisions

The spacing to the first stud is calculated as 0.4 d in accordance with clause 13.3.8.6. This spacing is rounded down to the nearest 5 mm. The maximum typical stud spacing is 0.5d or 0.75d in accordance with clause 13.3.8.6. The maximum tangential spacing of rails at the face of the column is limited to 2d. Tangential spacing requirements are not checked at locations other than the face of the column/support. The SSR is extended until the cutoff section stresses are within the allowable limit of 0.19λφ c f′c per CSA A23.3 13.3.7.4. For cutoff sections outside the original column perimeter sections, γv is adjusted in accordance with ACI 421.1R99 Appendix B. The minimum rail length is 2 d in accordance with 13.3.7.4.

66.6 AS 3600-2001 Punching Shear Design The AS 3600 Punching Shear Model

The critical section for punching shear is assumed to be at dom/2 from the face of the loaded area or support, where dom represents the mean value of do, averaged around the critical perimeter. Based on the derivation of the code equations, dom is not meant to include the thickness of beams. Concept uses a heuristic method for determining the critical section thickness in regions of differing slab/beam thicknesses around the punching check. The critical section thicknesses can be inspected by turning them on using “visible objects”. The AS 3600 model for punching shear assumes that the shear force V* is distributed evenly around the critical section creating a uniform average shear stress of v = V*/udom. The unbalanced moment, Mv* is resisted by a 3-component mechanism: 1 Difference in yield moments at the front and back faces of the slab strips. 2 Eccentricity of the uniform shear stresses v from the centroid of the support or load. 3 Torsional moment on the side faces (torsion strips).

In the model, the torsional moment in #3 is resolved into a maximum shear stress and added to the uniform average shear stress v. The proportion of Mv* contributing to the torsional moment in #3 is actually variable, but is assumed to be constant to simplify the model. The value of Mv* is taken at the centre of the column/support. Design Equations

The resulting shear capacity Vuo where Mv* is zero (as well as on slab strip faces) is calculated per AS 3600 clause 9.2.3a: V uo = ud om ( f c v + 0.3σ cp ) Rearranged to view in terms of limiting stress, this equation becomes: V∗ ------------- ≤ f cv + 0.3σ cp ud o m 656

RAM Concept

Chapter 66 Where Mv* is not zero, the model results in the following design equation in AS 3600 clause 9.2.4a when there are no closed ties in the torsion strips and no spandrel beams: V uo V u = ------------------------------------------- uM v∗  1 +  ----------------------  8V∗ ad om This expression sets an upper limit on the combination of Mv* and V* that can be resisted by the concrete. This equation can be rearranged to view in terms of limiting stresses: M v∗ V∗ ---------------- + ------------- ≤ f c v + 0.3σ cp 2 ud om 8ad o m The code allows for increasing the punching capacity by placing a minimum quantity of closed ties in the torsion strips. Concept provides check box items to include calculation based upon the presence of these minimum closed ties in accordance with AS 3600 clause 9.2.4b. Concept does not calculate the quantities of minimum ties required by this clause, which must be calculated and included by the Engineer. When the minimum quantity of closed ties is present in the torsion strips, the equation in clause 9.2.4b is used: 1.2V uo V u = ---------------------------------------- uM v∗  1.0 +  ---------------  2V∗ a 2 This expression can also be re-arranged to view in terms of limiting stresses: M v∗ V∗ ----------------------- + -------------------- ≤ f c v + 0.3σ cp 2 1.2ud om 2.4a d om In scenarios where the shear to moment ratio is small and/or torsion strip width to effective depth is small, it is possible for the AS 3600 equations to calculate a lower strength with ties than without. Concept does not calculate shear capacity using the beam provisions of clause 9.2.4c and 9.2.4d. Calculation of Maximum and Allowable Shear Stress and Corresponding Stress Ratio

The allowable shear stress calculated is: f c v + 0.3σ cp , where ′ ′ 2 f c v = 0.17  1 + ----- f c ≤ 0.34 f c  β  h

and σ cp is the average prestress in the punching check region. If σ cp results in tension it reduces the allowable stress. The reported allowable shear stresses are multiplied by Φ = 0.7 . For each set of enveloped force reactions, a maximum unreinforced shear stress is calculated as follows: 1 The maximum unreinforced shear stress on the slab strip face is calculated. 2 The maximum unreinforced shear stress on the torsion strip due to combined shear and bending is calculated for bending

about the r-axis, using the closed ties provisions if selected by the user. 3 The maximum unreinforced shear stress on the torsion strip due to combined shear and bending is calculated for bending

about the s-axis, using the closed ties provisions if selected by the user. The absolute maximum shear stress from above is reported as the maximum unreinforced shear stress for that force envelope. The unreinforced stress ratio for each force envelope is the maximum unreinforced stress/allowable stress.

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Chapter 66 Calculation of Punching Resistance with SSR

The SSR is used to resist direct shear stresses, but not torsion stresses. Where SSR is provided the punching resistance is calculated as follows: 1 The following operations are performed individually on each face: 2 A minimum number of rails are installed based upon a maximum transverse rail spacing of 2dom. The rails are installed

at the allowable maximum spacing. The length of each rail is a minimum of 2.5d. 3 The number of strips used for strength is calculated, up to a total of 4 (2 slab and 2 torsion strips). This is accomplished by

determining how many faces contain parts of the critical section. If there is no part of the critical section on a particular face, this face will not be used for strength design but will get rails placed, if possible, using the maximum transverse spacing requirement. 4 The perimeter length of the face is calculated both as a slab strip and a torsion strip. The length of the torsion strip is simply

the appropriate width of the critical section. The length of the slab strip is calculated as the length remaining after any torsion strip lengths have been deducted. If the torsion strip is broken up with holes/openings, it is possible that the slab strip length will be less than or equal to zero. In this event no design will be reported and the status will be reported as “Failed”. 5 The average effective depth of the slabs containing the existing rails is calculated. 6 The number of additional rails required is calculated and added, if necessary, and step 4 and 5 are repeated until a satis-

factory solution is found. The strength equations used in the calculation of SSR are as follows: For slab strips: V u = V uo ( 1 + K s ) where 1 d u K s = --------- A vs f vy  ---  ---  s   b V uo and Avs = cross sectional area of one peripheral line of studs in the strip b = width of the strip fvy = yield stress of the studs in the strip d = average effective depth of the slab containing the shear stud rails u = perimeter length of the critical section For torsion strips: Vu o V u = --------------------------------------------uM v∗ 1 --------------- + ----------------------1 + K t 8V∗ ad om where 1 d u K t = --------- A vt f vy  ---  ---  s   a Vu o and a = width of the strip

658

RAM Concept

Chapter 66 The maximum punching shear force which can be transferred to the column is taken as the smaller of these two values of ΦV u : where V ≤ ΦV u Φ = 0.7 Maximum Reinforced Strength

The maximum strength of the reinforced slab/column connection is given as: Vumax = 0.2fc’udom thus giving the following 2 conditions that must be satisfied: In the slab strip, Vuo (1+Kt) < 0.2udom fc’ In the torsion strip, Vuo (1+Ks) < 0.2udom fc’ Miscellaneous Provisions

The spacing to the first stud is calculated as 0.35 d. This spacing is rounded down to the nearest 5 mm for metric units (or 1/8 inch for US units). The maximum typical stud spacing is 0.75 d. In seismic applications, the Engineer can limit the typical spacing to a smaller value by specifying the typical stud spacing directly. A minimum quantity of SSR reinforcement is provided as follows: In the slab strip, 0.35bs A vs = ---------------f vy In the torsion strip, 0.35as A vs = ---------------f vy When SSR reinforcement is required, the minimum quantity of reinforcement is required on all strength strips.

66.7 EN 1992-2004 Punching Shear Design The EN 1992-2004 Punching Shear Model

The punching shear analysis and design approach uses the EC2 provisions for the basis of the implementation. Some condition specific EC2 provisions were generalized using CEB-FIP 90. The implementation also implements suggestions in TR-43 regarding treatment of precompression in the shear strength equations. A control perimeter (u1) is defined at 2d from the periphery of area of application of force. This control perimeter is constructed so as to minimize its length. The corners of the perimeter are rounded.

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659

Chapter 66 For slab edges located within the punching check, additional control perimeters will be generated by projecting perpendicular lines from the original control perimeter to the slab edges. Additionally, control perimeters will be generated for each basic slab shape, cap, etc. This could result in a number of basic control perimeters. To calculate the perimeter stresses, a plastic distribution of stresses caused by the eccentricity between the load/reaction and the control perimeter is superimposed with the shear stresses caused by the concentric loading to calculate a complete stress distribution on the perimeter. Where there are eccentricities in two orthogonal directions, they are considered simultaneously. The k factor in EC2 equation 6.39 is applied to the unbalanced moment after the column forces are transformed to the plastic neutral axis of the control perimeter. EC2 clause 6.4.3(3) requires the calculation of a β factor on the basic control perimeter. The same β factor is then applied to all subsequent perimeter calculations. This simplification is made due to the complexity in the plastic section calculations. Concept does not make this assumption, but instead calculates and applies an appropriate β factor for each perimeter calculated. This is in accordance with the approach for the cutoff section in CEB-FIP 90.

66.7.1 Calculation of punching resistance for the unreinforced section Control Perimeter Section Properties and Equations for the Calculation of Actual Stresses

Before any calculations are performed, the following manipulations are carried out on the reactions at the column center: 1 The column reactions are transformed to the control perimeter elastic centroid. 2 k factors are calculated using ratios about the column principal axes. 3 The reactions are rotated to the column principal axes and multiplied by appropriate k factors. 4 The reactions are rotated to the control perimeter elastic principal axes.

σ b + σd

σb + σ c

area a

area c

σa + σc

area d

σa + σd

area b

Figure 66-3 EN 1992-2004 control perimeter

The remainder of the calculations are carried out about the elastic principal axes of the control perimeter. Since a plastic stress distribution is used, if the “punching” area of the control perimeter on each side of the elastic neutral axes is not equal, the magnitudes must vary to maintain vertical equilibrium. This is handled by using multiplication factors representing the ratio of stress on one side of the principal axis over the stress on the other side. These factors are represented in the following form: Area a α x = --------------Area b Area c α y = --------------Area d

660

RAM Concept

Chapter 66 The stresses in each quadrant (considering bending about each axis separately) can then be represented as: σb = –αxσa

Equation 1

σd = –αyσc

Equation 2

Two simultaneous equations can then be set up and solved for the state of stress around the critical section: Mox = unbalanced moment about the principal x-axis of the critical section (after adjustment by k) Moy = unbalanced moment about the principal y-axis of the critical section (after adjustment by k) d = effective depth at location in critical section

Substituting equations 1 and 2 and collecting terms,

These terms can be envisioned as plastic section moduli and each term has units of cubic length. Due to the interaction of α in the above equations and the equations below, these values are only valid for the axes about which they are calculated. Equation 3 and 4 then become:

We can then use equations 1 and 2 to solve for σ b and σ d .

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661

Chapter 66 The stress in any given “quadrant” of the critical section is then solved for as:

Calculation of Allowable Stress

The punching resistance for an unreinforced section is calculated as follows: 1 --3

v Rd ,c = C Rd ,c k ( 100ρ 1 f ck ) + k 1 σ cp ≤ v min + k 1 σ c p

(6.47)

where 0.18 C Rd ,c = ---------γc 200 k = 1 + --------- ≤ 2.0d d

d in mm

ρ1 =

relates to bonded tension steel in y and z directions (this value is input directly by the user as a

ρ ly + ρ lz ≤ 0.02

punching check property) fck = characteristic compressive cylinder strength of concrete at 28 days k1 = 0.1 σ cp = ( σ c y + σ c z ) ⁄ 2 average compression in the punching check region. Calculation of Punching Resistance with SSR

Where SSR is used the punching resistance is calculated as follows: v Rd ,cs = 0.75v Rd ,c + [ 1.5 ( d sw ⁄ s r )A sw f ywd ] ⁄ u i d i

(6.52)

dsw = average effective depth of slab containing shear reinforcement sr = radial spacing of shear reinforcement Asw = area of one peripheral line of shear reinforcement di = the average effective depth of the perimeter under consideration fywd = effective design strength of the shear reinforcement = f yk ⁄ γ s di = the average effective depth of the perimeter under consideration

Note: Because the head sizes of SSR are typically selected to ensure 100% development of the stem, the yield strength of the SSR reinforcement is used without adjustment for effective depth, d. If the Engineer needs to make reductions to the effective yield strength of the studs due to depth issues these modifications can be made by specifying a reduced yield stress in the “SSR Systems” on the “Materials” page. Limitation of Punching Stress at the Perimeter of the Column or Loaded Area

At the perimeter of the column face the maximum shear stress is limited to: vEd = vRd,max

662

(6.53)

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Chapter 66 where v Ed = βV Ed ⁄ ( u 0 d ) vRd,max = 0.5 v fcd β = maximum beta from calculated control perimeters, u1 v = 0.6[1 - fck/250] fck in N/mm2 fcd = design value of concrete compressive strength u0 = length of column or loaded area periphery u0 is further limited as follows: Edge columns: u0 < 6d

Note: This simplification for edge columns was necessary due to difficulty in calculating the code equation for irregular situations. This provision is not in strict compliance with the code and should be reviewed by the Engineer as necessary. Corner columns: u0 < 3d Miscellaneous Provisions

The control perimeter at which shear reinforcement is not required is calculated using eq. 6.47. The outermost perimeter of shear reinforcement is placed not greater than 1.5d within this perimeter. The spacing to the first stud is calculated as 0.5 d. The maximum typical stud spacing is 0.75 d. The maximum transverse rail spacing is 1.5 d within the first control perimeter and 2.0 d outside the first control perimeter. A minimum quantity of SSR reinforcement is provided in accordance with EC2 equation 9.11: A sw ,m in ≥ ( 0.08 f c k s r s t ) ⁄ 1.5f yk where st is assumed to be < 2d (Final rail layout should be confirmed/adjusted to be in agreement with this assumption)

Note: EC2 has special provisions for column bases. These provisions are not implemented in Concept (the provisions above are applied to all punching checks). For slabs without prestress, this will always be conservative. For slabs with prestress, the Engineer will need to evaluate the validity of the results.

66.8 Sign convention The equations presented require the use of the “right-hand rule” sign convention. While RAM Concept allows you to set your own sign conventions for reactions, it will internally apply the correct signs to the equations.

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Figure 66-4 Positive moment reactions derived from the “right-hand rule” sign convention.

Concept reports the reactions applied from the column to the slab. The reactions are the forces and moments that would need to be applied to the column joint in order to keep the system in equilibrium if the columns were removed. This can be envisioned by removing the column from the structure and replacing it with the reported reactions applied at the column centroid. Refer to Figure 66-5 for clarification.

Figure 66-5 Column reaction sign conventions

66.9 Advice on the selection of punching check properties Maximum Search Radius - This radius defines the circular area around a column that RAM Concept will investigate in its search for potential failure locations. A punching zone radius that is set to be a very large distance will always be conservative. However, having a very large radius has two detrimental effects. First, RAM Concept will need to review a larger area of the slab, and hence will take longer to check the column. More importantly, slab holes and slab edges that are

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Chapter 66 far from the column will be considered in determining the potentially critical sections which may result in a smaller critical section than is appropriate. Cover to CGS - This is the distance from the top of slab to the centroid elevation of the top reinforcement. In general this is the distance from the top of the slab to the bottom of the top bar (or the top of the bar under the top bar). This distance is subtracted from the slab thickness to determine the “d” distance. Angle - The plan angle about which punching reactions are enveloped. For some codes this also defines the angle about which the punching calculations are performed. In general, this should either be set to the angle of the column or (if the column is at a slab edge) the angle of the slab edge. The “Align Punch Check Axis with Rectangular Columns” checkbox can be used to automatically set the angle. Edge/Hole Treatment - See Figure 66-2. Connection Type - Corner, edge, interior or auto. Refer to “About Connection Type” on page 650.

66.10 Miscellaneous information Effect of precompression

For post-tensioned slabs, the allowable calculated by Concept may be smaller than that calculated by 2D frame programs, because Concept uses an effective prestress value that is an average for the punching zone. This punching zone average will reflect a lower effective prestress in column capitals and other thickened areas.

66.11 Some final words of advice RAM Concept is not infallible in its determination of potentially critical sections; for unusual geometries Concept may not check the appropriate section and/or may check inappropriate sections that give higher than appropriate stress ratios. The engineer must review Concept’s selection of potentially critical sections, and must use engineering judgment to decide if Concept’s selections are appropriate and if the application of the code model is appropriate.

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Chapter 67

67 Vibration Analysis Notes Structures undergo vibrations that may upset the occupants of the structure or disturb sensitive equipment. While there are a number of sources of excitation that cause vibration, one common source of excitation is footsteps of the structure occupants. This chapter gives an overview of vibration analysis and advice on using RAM Concept’s vibration and footfall analysis capabilities. Vibration options are available through the Calc Options dialog and the analysis is invoked using the Calc vibration analysis (

) command.

67.1 Dynamic Characteristics of Structures A complete discussion of dynamic behavior of structures is outside the scope of this chapter and can be found in strucutral dynamics textbooks. Some basic understanding of vibrations and structural dynamics is assumed.

67.1.1 Free Vibration Free vibration of undamped structures occurs when the structure is displaced to an initial displacement, released and then allowed to vibrate freely. It is related only to the stiffness and mass in the structure. The preferred vibration patterns of the structure are referred to as the natural modes of vibration. Each mode of vibration has a characteristic deflected shape and an associated vibration frequency. If an undamped structure is initially displaced to a natural mode shape and then released, the structure will undergo simple harmonic motion (displacement vs. time curve has a sinusoidal shape). The mode shape with the lowest natural frequency is referred to as the fundamental mode of vibration. Floor structures may have many very closely spaced natural modes of vibration, with only small parts of the structure participating in each one. To capture the complete dynamic response, it is necessary to calculate enough modes to include all modes with natural frequencies of interest, which generally include modes with frequencies up to about 12-15 Hz for resonant response analysis and up to about 2 times the fundamental mode of vibration for impulsive response.

Figure 67-1 Fundamental mode shape Number of modes

RAM Concept allows the user to input the number of mode shapes to be calculated. The frequencies of the mode shapes can be viewed in the text tables and the number of mode shapes calculated increased as necessary. Dynamic concrete modulus factor

RAM Concept allows input of a dynamic concrete modulus factor which represents the ratio of dynamic modulus to the static modulus. The dynamic modulus of elasticity of concrete (small strains for short durations) is generally higher than the RAM Concept

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Chapter 67 static modulus of elasticity. The dynamic modulus affects the stiffness of the structure and thus factors into the calculation of the natural frequencies and mode shapes. The default factor in RAM Concept is 1.2. Stiffness matrix

RAM Concept also allows selection of the stiffness matrix to use in the calculation of frequencies and mode shapes. If one of the load history stiffness matrices is used (for example to account for cracking), the load history analysis must be run after selecting the load history step to use for stiffness matrix and prior to the vibration calculations.

Note: Since the load history calculations use stiffness adjustments to account for long-term effects, it is not recommended to use a load history step that has any prior load history steps with any significant duration as this can underestimate the short term stiffness. Mass

The structure self-mass is always considered automatically in the analysis, which can be adjusted by setting the “Density for Loads” property in the concrete material properties. In some cases there is additional mass permanently in place that should be considered in the analysis of the frequencies and mode shapes. This additional mass can be drawn on the additional mass layer located under the Vibrations folder. This layer allows the user to define area loads, line loads, and point loads that will be converted to mass for vibration analysis purposes.

67.1.2 Damping Real structures have some level of damping which tends to reduce the vibratory response over time. The higher the damping, the faster the vibration will decay and the less likely vibrations will cause adverse affects. Damping is often defined as a fraction of critical damping, which is the level of damping that would be necessary to prevent oscillation altogether. In RAM Concept a constant damping ratio is used in the calculation of all modes. Typical damping ratios for concrete structures range from about 0.01 to 0.02 (1% to 2% of critical) for bare concrete floors, and 0.02 to 0.035 (2% to 3.5% of critical) for concrete floors with typical fit out.

67.1.3 Resonant vs. Impulsive Response In structures with modes that have lower natural frequences (less than approximately 4 times the maximum footstep frequency) it is possible for the dynamic response to build up (increase) over time. This is caused by a phenomenon know as resonance and occurs when the frequency of the excitation closely matches the natural frequency of a vibration mode of the structure. Resonance is most likely to occur when the walking frequency matches the natural frequency of the structure, but it is also possible when any of the first four harmonics of the walking frequency (fw , 2fw , 3fw,,4fw) match the natural frequency (fn ). Resonance at higher harmonics is much less likely. In structures whose fundamental mode of vibration has a natural frequency larger than about 12-15Hz, the dynamic response of each footfall tends to dissipate almost entirely before the next footfall. This type of response is referred to as impulsive because a buildup of response due to resonance is not likely in this frequency range.

67.2 Resonant Footfall Response RAM Concept calculates the footfall response of structures using assumed dynamic loadings that were derived from a large number of experimentally measured footfall force time histories. These studies also showed that normal walking rates range from about 1.5 to 2.5 steps per second. The first four harmonics of the specified range of walking frequencies are considered. From these harmonics, a set of critical walking frequencies are determined that would coincide with the natural frequencies of the structure and thus promote resonance. The response must be calculated for each of these critical walking frequencies as it is otherwise not possible to determine which frequency is most critical.

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Chapter 67 The assumed periodic footfall function can be separated into any number of harmonic components using a Fourier series. RAM Concept uses 4 harmonic components in this evaluation.

p( t) =

n

∑

j=1

Wκ sin  j2π - t  ------T 

where W = weight of the individual walking κ = dynamic load factor (refer to “A Design Guide for Footfall Induced Vibration of Structures” for a detailed discussion) j = harmonic number n = total number of harmonic components considered T = period of the footfall This relationship is demonstrated graphically below for a walking frequency of 1.5 Hz:

Figure 67-2 Assumed footfall forcing function built up from harmonic components

In the resonant analysis, a maximum natural frequency to use in the analysis can be input into RAM Concept. Only modes of vibration with natural frequencies less than or equal to the input value will be used in the resonant response analysis.

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67.2.1 Resonant Simplified (fast) Analysis RAM Concept’s Simplified (fast) Analysis is based upon a method in the Concrete Centre’s design guide for vibrations[Willford, M.R. and Young, P., “A Design Guide for Footfall Induced Vibration of Structures”, Concrete Centre, 2006]. This method predicts the total buildup that is possible under harmonic loading under a limited number of cycles. It is performed for each harmonic individually, and finds the peak acceleration, but provides no information about the phase of the different harmonic results. The results from the different harmonics are combined using a square root of sum of squares (SRSS) technique. This method is designated the default analysis method in RAM Concept due to its fast computation time and relative accuracy of results.

Note: Because the simplified method only calculates accelerations and response factors, velocity envelope results will not include a contribution from the resonant response analysis. If impulsive response calculations are performed, the velocity envelopes will only include the results from the impulsive analysis, which can be misleading. If velocity performance criteria are being used with resonant response analyis, Modal Analysis should be used instead of the Simplified Analysis.

67.2.2 Resonant Modal Analysis RAM Concept’s Modal Analysis is based upon a classical mode superposition method, also referred to as modal analysis. In this approach individual (uncoupled) modal equations are solved to determine the individual modal responses which are then superimposed to obtain the total response. This approach results in a complete time history for the total response and calculates accelerations and velocities. This analysis is performed for each harmonic individually to facilitate combination of the response factors. Since a complete time history for each harmonic results is known the results can be combined using direct algebraic summation. This method can be computationally time consuming. This analysis requires a duration and time interval to be used in the calculations. The recommendation is to select a duration that will include a minimum of approximately 30 cycles of excitation, and a time interval that is at least 10 times shorter than the shortest harmonic excitation period. For most problems with normal footstep frequencies, a 20 second duration with a 0.01 second time interval will provide good results.

67.2.3 RMS Values for Resonant Response The resonant response analyses result in peak accelerations and velocities, which are often not used in evaluation of vibration performance criteria because they are not representative of the vibration as a whole. A measure of the average response amplitude is the root mean square, or RMS values which are generally evaluated over a certain time period. The RMS method involves squaring the velocity or acceleration at each time instant, finding the average of the squared values over the evaluation period, then taking the square root of this average. For simple harmonic motion the RMS value is equal to 1/ 2 or 70.7% of the peak value. In the calculation of RMS values in RAM Concept, the RMS value is always taken as 1/ 2 of the peak value.

67.2.4 Calculation of Response Factor The response factor is a multiplier on the level of vibration at the threshold of human perception. Thus, a response factor of 1 would represent a level of vibration that is just at the threshold of human perception, and a response factor of 2 would represent twice the perceivable level.. People are more sensitive to vibration at some frequencies than at others. The base curves for human perceivability are taken from BS 6472. Since vibrations can contain a range of frequencies, the response factor in RAM Concept is calculated individually for each harmonic excitation frequency by taking a baseline acceleration ( a RM S = 1) from the curve for that frequency, then combined using square root of sum of squares (SRSS). For resonant response, the response factor is always calculated using accelerations.

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67.3 Impulsive Footfall Response The most critical response in this type of analysis is for the largest footfall rate, and thus the impulsive analysis can be performed on just the largest footfall rate in the range (the footfall rate still affects the magnitude of the impulse). The analysis is based upon a method in the Concrete Centre’s design guide for vibrations[Willford, M.R. and Young, P., “A Design Guide for Footfall Induced Vibration of Structures”, Concrete Centre, 2006]. The method calculates a complete time history velocity curve, from which a time history acceleration curve can be derived. All modes with natural frequencies up to twice the fundamental frequency are considered in the analysis.

67.3.1 RMS Values for Impulsive Response The impulsive response analyses result in peak accelerations and velocities, which are often not used in evaluation of vibration performance criteria because they are not representative of the vibration as a whole. A measure of the average response amplitude is the root mean square, or RMS values which are generally evaluated over a certain time period. The RMS method involves evaluating the response over a period of one footfall:

v RMS =

1T --- ∫ v ( t ) 2 dt T0

67.3.2 Calculation of Response Factor The response factor is a multiplier on the level of vibration at the threshold of human perception. Thus, a response factor of 1 would represent a level of vibration that is just at the threshold of human perception, and a response factor of 2 would represent twice the perceivable level. People are more sensitive to vibration at some frequencies than at others. The base curves for human perceivability are taken from BS 6472. Since the methods used in RAM Concept combine the results of the different modes of vibration, the baseline velocity value ( v RMS = 1) is taken from the curve using the frequency of the fundamental mode of vibration.

67.4 Evaluating Vibration Performance and Interpreting Results

67.4.1 Excitation and Response Node Options There are a number of different combinations of excitation and response nodes available for analysis. For excitation nodes, the following options are available. Excitation at All Nodes

This option treats every node in the model as an excitation node. Excitation at Critical Nodes

This option first does a preliminary analysis on every node in the structure, calculating results at only the excitation point and using the simplified (fast) analysis to find a response factor at each node. Then, only nodes with a calculated response factor greater than or equal to the entered Excitation response factor threshold are excited in the primary analysis. Excitation at Specified Nodes

Excitation area polygons can be drawn on the Excitation Areas Plan (on the Vibration Layer). Only the nodes of any elements intersected by the drawn excitation area polygons are considered as excitation nodes. This option works in conjunction with other excitation area options. For example, if an excitation area is drawn and “Excitation at Critical Nodes” is specified, only nodes that both intersect the excitation area and have a preliminary response factor greater than or equal to RAM Concept

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Chapter 67 the Excitation response factor threshold will be excited. If no excitation areas are drawn, every node is considered as an excitation node. Response at All DOF at All Nodes

When using Modal Analysis, this option calculates the response at all DOF (lateral, angular, vertical) at all nodes. Since the lateral and angular components are rarely critical for floor vibrations and calculating these components increases the run time, using this option is not normally recommended. Response at Vertical DOF at All Nodes

This option calculates the response at only the vertical DOF at every node. As each node is being considered as an excitation node, the response at all other nodes in the structure is calculated and enveloped. Response at Vertical DOF at Only Excited Node

This option calculates the response at only the vertical DOF at the excited node only. As each node is being considered as an excitation node, the response is calculated at the excitation node and is not calculated at any other node.

67.4.2 Recommendations for Analysis Options The default setting is to use the resonant simplified (fast) calculation with all nodes considered as an excitation node and the response calculated at the vertical DOF at the excited node only. This is generally the fastest combination to get reasonable results calculated for the entire floor. This combination generally captures the most critical effects in each region, but doesn’t well pick up the extent of the response in each critical region. This is because the worst case response at some nodes near the critical nodes would be from excitation of the nearby critical node and not from self-excitation. However, the default setting is very recommended for daily design use for structures that are not vibrationally sensitive. In order to better pick up the critical effects of the entire region, the “Response Nodes” setting could be changed to Vertical DOF at all nodes, but there will normally be a considerable increase in runtime. For structures that are vibrationally sensitive or if a higher degree of accuracy is desired, the modal analysis method is recommended. Because this method is computationally expensive, it is generally necessary to use it in conjunction with other settings to speed up the calculation time. One such example is to use the simplified method to evaluate the floor as a whole, then excite and evaluate a subset of the structure using modal analysis. This can be accomplished by using the “Critical Nodes” option and setting the Excitation response factor threshold to avoid exciting non-critical nodes, by drawing excitation areas to take advantage of known areas of excitation like corridors and hallways, or a combination of the two.

Note: If the “Critical nodes” or excitation areas are drawn in conjunction with the “Vertical DOF at only excited node” option, there will not be any response calculated at some nodes. In order to get a response at particular node it must either be considered as an excitation node (with associated response calculated) or as a response node while another node is considered as an excitation node (by using the “Vertical DOF at all nodes” setting for Response Nodes).

67.4.3 Velocity and Acceleration Contour Plots RAM Concept calculates and displays contour plots for velocity, acceleration, and response factors. These plots represent the envelope at each node of all the calculated cases which include resonant response calculations (for each critical excitation frequency) and the impulsive response calculation for the critical (maximum) excitation frequency. These contour plots can be used to evaluate performance criteria and indicate the worst case vibration response at each location.

67.4.4 Evaluation of Response Factor Plots The response factor represents a multiple of the level of vibration that is barely perceivable to a human. A response factor of 1 indicates a vibration that is just perceivable, a response factor of 2 represents twice that, and so on. The baseline curve that represents R=1 that is used in RAM Concept is from BS 6472 and is consistent with the ISO standard 2631-2. The curve is reproduced below. Like the velocity and acceleration plots, the response factor contour plots represent enveloped results of all the different analyses at each node. As such, the response factor contours are often used for evaluation of performance

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Chapter 67 criteria. The following table lists some common response factor limits mentioned in BS 6472 and ISO 2631-2 for some different environments. Environment

Response Factor Limit

Description of Use

Workshops, Office

8-10

Perceptible vibration, suitable for non-sensitive areas.

Residential

4-8

Possible perceptible vibration, suitable for sleep areas in most cases.

Operating rooms

1-4

Near the threshold of perception, suitable for sensitive sleep areas and in most instances for microscopes to 100x and other low sensitivity equipment.

Sensitive Equipment rooms

0.0625-1

Suitable for senstive equipment, electron microsopes, etc.

Table 67-1 Recommended response factor limits for various environments

Figure 67-3 Vibration base curve for RMS acceleration (response factor = 1)

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