Staadpro 2007 International Codes 2007 Complete

STAAD.Pro 2007

INTERNATIONAL DESIGN CODES DAA037810-1/0001

A Bentley Solutions Center www.reiworld.com www.bentley.com/staad

STAAD.Pro 2007 is a suite of proprietary computer programs of Research Engineers, a Bentley Solutions Center . Although every effort has been made to ensure the correctness of these programs, REI will not accept responsibility for any mistake, error or misrepresentation in or as a result of the usage of these programs.

Copyright attribution: ©2008, Bentley Systems, Incorporated. All rights reserved. Trademark attribution: STAAD.Pro, STAAD.foundation, Section Wizard, STAAD.Offshore and QSE 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. RELEASE 2007 Published February, 2008

About STAAD.Pro STAAD.Pro is a general purpose structural analysis and design program with applications primarily in the building industry - commercial buildings, bridges and highway structures, industrial structures, chemical plant structures, dams, retaining walls, turbine foundations, culverts and other embedded structures, etc. The program hence consists of the following facilities to enable this task. 1.

2.

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Graphical model generation utilities as well as text editor based commands for creating the mathematical model. Beam and column members are represented using lines. Walls, slabs and panel type entities are represented using triangular and quadrilateral finite elements. Solid blocks are represented using brick elements. These utilities allow the user to create the geometry, assign properties, orient cross sections as desired, assign materials like steel, concrete, timber, aluminum, specify supports, apply loads explicitly as well as have the program generate loads, design parameters etc. Analysis engines for performing linear elastic and pdelta analysis, finite element analysis, frequency extraction, and dynamic response (spectrum, time history, steady state, etc.). Design engines for code checking and optimization of steel, aluminum a nd timber members. Reinforcement calculations for concrete beams, columns, slabs and shear walls. Design of shear and moment connections for steel members. Result viewing, result verification and report generation tools for examining displacement diagrams, bending moment and shear force diagrams, beam, plate and solid stress contours, etc. Peripheral tools for activities like import and export of data from and to other widely accepted formats, links with other popular softwares for ni che areas like reinforced and prestressed concrete slab design, footing design, steel connection design, etc. A library of exposed functions called OpenSTAAD which allows users to access STAAD.Pro’s internal functions and routines as well as its graphical commands to tap into STAAD’s database and link input and output data to third -party software written using languages like C, C++, VB, VBA, FORTRAN, Java, Delphi, etc. Thus, OpenSTAAD allows users to link in-house or third-party applications with STAAD.Pro.

About the STAAD.Pro Documentation The documentation for STAAD.Pro consists of a set of manuals as described below. These manuals are normally provided only in the electronic format, with perhaps some exceptions such as the Getting Started Manual which may be supplied as a printed book to first time and new-version buyers. All the manuals can be accessed from the Help facilities of STAAD.Pro. Users who wish to obtain a printed copy of the books may contact Research Engineers. REI also supplies the manuals in the PDF format at no cost for those who wish to print them on their own. See the back cover of this book for addresses and phone numbers. Getting Started and Tutorials : This manual contains information on the contents of the STAAD.Pro package, computer system requirements, installation process, copy protection issues and a description on how to run the programs in the package. Tutorials that provide detailed and step-by-step explanation on using the programs are also provided. Examples Manual This book offers examples of various problems that can be solved using the STAAD engine. The examples represent various structural analyses and design problems commonly encountered by structural engineers. Graphical Environment This document contains a detailed description of the Graphical User Interface (GUI) of STAAD.Pro. The topics covered include model generation, structural analysis and design, result verification, and report generation. Technical Reference Manual This manual deals with the theory behind the engineering calculations made by the STAAD engine. It also includes an explanation of the commands available in the STAAD command file. International Design Codes This document contains information on the various Concrete, Steel, and Alu minum design codes, of several countries, that are implemented in STAAD. The documentation for the STAAD.Pro Extension component(s) is available separately.

Table of Contents International Codes Introduction

Section 1

Australian Codes

1A Concrete Design Per AS3600-2001 1A.1 1A.2 1A.3 1A.4 1A.5 1A.6 1A.7 1A.8

Design Operations Section Types for Concrete Design Member Dimensions Design Parameters Slenderness Effects and Analysis Consideration Beam Design Column Design Slab/Wall Design

1B Steel Design Per AS 4100-1998 1B.1 1B.2 1B.3 1B.4 1B.5 1B.6 1B.7 1B.8 1B.9 1B.10

Section 2

General Analysis Methodology Member Property Specifications Built-in Steel Section Library Section Classification Member Resistances Design Parameters Code Checking Member Selection Tabulated Results of Steel Design

British Codes

2A Concrete Design Per BS8100 2A.1 Design Operations 2A.2 Design Parameters 2A.3 Slenderness Effects and Analysis Considerations 2A.4 Member Dimensions 2A.5 Beam Design 2A.6 Column Design 2A.7 Slab Design 2A.8 Shear Wall Design

i

11-1 1-1 1-1 1-1 1-2 1-2 1-3 1-5 1-6

1-9 1-9 1-10 1-10 1-10 1-15 1-15 1-17 1-20 1-20 1-21

22-1 2-1 2-1 2-4 2-4 2-5 2-7 2-8 2-10

2B Steel Design Per BS5950:2000 2B.1 2B.2 2B.3 2B.4 2B.5 2B.6 2B.7 2B.8 2B.9 2B.10 2B.11 2B.12 2B.13

General Analysis Methodology Member Property Specifications Built-in Steel Section Library Member Capacities Design Parameters Design Operations Code Checking Member Selection Tabulated Results of Steel Design Plate Girders Composite Sections Design of Tapered Beams

2B1 Steel Design Per BS5950:1990 2B1.1 2B1.2 2B1.3 2B1.4 2B1.5 2B1.6 2B1.7 2B1.8 2B1.9 2B1.10 2B1.11 2B1.12

General Analysis Methodology Member Property Specifications Built-in Steel Section Library Member Capacities Design Parameters Design Operations Code Checking Member Selection Tabulated Results of Steel Design Plate Girders Composite Sections

2C Design Per BS5400 2C.1 2C.2 2C.3 2C.4 2C.5 2C.6 2C.7

General Comments Shape Limitations Section Class Moment Capacity Shear Capacity Design Parameters Composite Sections

2D Design Per BS8007 2D.1 2D.2 2D.3 2D.4

General Comments Design Process Design Parameters Structural Model

2-23 2-23 2-25 2-25 2-25 2-30 2-34 2-46 2-47 2-48 2-49 2-50 2-51 2-51

2-55 2-55 2-56 2-56 2-56 2-60 2-65 2-73 2-74 2-74 2-75 2-76 2-77

2-79 2-79 2-79 2-80 2-80 2-80 2-81 2-82

2-85 2-85 2-85 2-87 2-87

2D.5

Wood & Armer Moments

2-88

2E Design Per British Cold Formed Steel Code

2-91

2E.1 2E.2 2E.3 2E.4 2E.5

Section 3

General Cross-sectional Properties Design Procedure Design Equations Verification Problem

Canadian Codes

3A Concrete Design Per CSA Standard A 23.3-94 3A.1 3A.2 3A.3 3A.4 3A.5 3A.6 3A.7 3A.8

Design Operations Section Types for Concrete Design Member Dimensions Slenderness Effects and Analysis Consideration Design Parameters Beam Design Column Design Slab/Wall Design

3B Steel Design Per CSA Standard CAN/CSA – S16-01 3B.1 3B.2 3B.3 3B.4 3B.5 3B.6 3B.7 3B.8 3B.9 3B.10 3B.11

General Comments Analysis Methodology Member Property Specifications Built-in Steel Section Library Section Classification Member Resistances Design Parameters Code Checking Member Selection Tabulated Results of Steel Design Verification Problems

3C Design Per Canadian Cold Formed Steel Code 3C.1 3C.2 3C.3

General Cross-Sectional Properties Design Procedure

2-91 2-91 2-92 2-93 2-101

33-1 3-1 3-1 3-1 3-2 3-3 3-4 3-7 3-7

3-9 3-9 3-10 3-10 3-10 3-17 3-17 3-21 3-23 3-24 3-25 3-26

3-41 3-41 3-41 3-42

3D Wood Design Per CSA Standard CAN/CSA-086-01 3D.1 3D.2 3D.3 3D.4 3D.5 3D.6 3D.7 3D.8 3D.9 3D.10

Section 4

General Comments Analysis Methodology Member Property Specifications Built-in Section Library Member Resistance Design Parameters Code Checking Member Selection Tabulated Results of Timber Design Verification Problems

Chinese Codes

4A Concrete Design Per GB50010-2002 4A.1 4A.2 4A.3 4A.4 4A.5 4A.6

Design Operations Section Types for Concrete Design Member Dimensions Design Parameters Beam Design Column Design

4B Steel Design Per GBJ 50017-2003 4B.1 4B.2 4B.3 4B.4 4B.5 4B.6 4B.7 4B.8 4B.9

Section 5

General Analysis Methodology Member Property Specifications Built-in Chinese Steel Section Library Member Capacities Combined Loading Design Parameters Code Checking Member Selection

European Codes

5A Concrete Design Per Eurocode EC2 5A.1 5A.2 5A.3 5A.4 5A.5

Design Operations Eurocode 2 (EC2) National Application Documents Material Properties and Load Factors Columns

3-49 3-49 3-50 3-50 3-50 3-54 3-57 3-59 3-60 3-60 3-61

44-1 4-1 4-1 4-1 4-2 4-2 4-6

4-11 4-11 4-12 4-12 4-12 4-17 4-18 4-18 4-21 4-22

55-1 5-1 5-1 5-2 5-2 5-3

5A.6 5A.7 5A.8

Beams Slabs Design Parameters

5B Steel Design Per Eurocode EC3 5B.1 5B.2 5B.3 5B.3 5B.4

General Description Design Parameters Tabulated Results of Steel Design Worked Examples User’s Examples

5C Timber Design Per EC5 Part 1-1 5C.1 5C.2 5C.3 5C.4

Section 6

General Comments Analysis Methodology Design Parameters Verification Problems

Egyptian Codes

6A Concrete Design Per ECCS205 6A.1 6A.2 6A.3 6A.4 6A.5 6A.6

Design Operations Member Dimensions Design Parameters Slenderness Effects and Analysis Considerations Beam Design Column Design

6B Steel Design Per Egyptian Code # 205 6B.1 6B.2

6B.3 6B.4 6B.5 6B.6

General Comments Allowable Stresses 6B.2.1 Axial Stress 6B.2.2 Bending Stress 6B.2.3 Shear Stress 6B.2.4 Combined Stress Stability Requirements Code Checking Member Selection Tabulated Results of Steel Design

5-3 5-5 5-5

5-9 5-9 5-14 5-19 5-20 5-37

5-45 5-45 5-49 5-58 5-61

66-1 6-1 6-1 6-2 6-3 6-3 6-6

6-9 6-9 6-9 6-10 6-11 6-13 6-13 6-14 6-14 6-15 6-15

Section 7

French Codes

7A Concrete Design Per B A E L 7A.1 7A.2 7A.3 7A.4 7A.5 7A.6 7A.7

Design Operations Design Parameters Slenderness Effects and Analysis Consideration Member Dimensions Beam Design Column Design Slab/Wall Design

7B Steel Design Per the French Code 7B.1 7B.2 7B.3 7B.4 7B.5 7B.6 7B.7 7B.8

Section 8

General Comments Basis Of Methodology Member Capacities Combined Axial Force and Bending Design Parameters Code Checking and Member Selection Tabulated Results of Steel Design Built-in French Steel Section Library

German Codes

8A Concrete Design Per DIN 1045 8A.1 8A.2 8A.3 8A.4 8A.5 8A.6 8A.7 8A.8

Design Operations Section Types for Concrete Design Member Dimensions Slenderness Effects and Analysis Considerations Beam Design Column Design Slab Design Design Parameters

8B Steel Design Per the DIN Code 8B.1 8B.2 8B.3 8B.4 8B.5 8B.6 8B.7 8B.8

General Analysis Methodology Member Property Specifications Built-in German Steel Section Library Member Capacities Combined Loading Design Parameters Code Cecking

77-1 7-1 7-1 7-1 7-2 7-3 7-5 7-5

7-7 7-7 7-8 7-8 7-9 7-9 7-9 7-9 7-12

88-1 8-1 8-1 8-1 8-2 8-3 8-5 8-6 8-7

8-11 8-11 8-12 8-12 8-12 8-17 8-18 8-19 8-21

8B.9

Section 9

Member Selection

Indian Codes

9A Concrete Design Per IS456 9A.1 9A.2 9A.3 9A.4 9A.5 9A.6 9A.7 9A.8 9A.9

Design Operations Section Types for Concrete Design Member Dimensions Design Parameters Slenderness Effects and Analysis Consideration Beam Design Column Design Bar Combination Wall Design in accordance with IS 456-2000

9A1 Concrete Design Per IS13920 9A1.1 9A1.2 9A1.3 9A1.4 9A1.5 9A1.6

Design Operations Section Types for Concrete Design Design Parameters Beam Design Column Design Bar Combination

9B Steel Design Per IS900 9B.1 9B.2 9B.3

9B.4 9B.5 9B.6 9B.7 9B.8 9B.9 9B.10 9B.11 9B.12 9B.13

Design Operations General Comments Allowable Stresses 9B.3.1 Axial Stress 9B.3.2 Bending Stress 9B.3.3 Shear Stress 9B.3.4 Combined Stress Design Parameters Stability Requirements Truss Members Deflection Check Code Checking Member Selection Member Selection by Optimization Tabulated Results of Steel Design Indian Steel Table Column with Lacings and Battens

8-22

99-1 9-1 9-1 9-1 9-2 9-2 9-3 9-7 9-14 9-15

9-27 9-27 9-27 9-28 9-28 9-32 9-43

9-49 9-49 9-50 9-50 9-51 9-52 9-53 9-54 9-54 9-54 9-55 9-55 9-55 9-56 9-56 9-57 9-59 9-67

9C Steel Design Per IS802 9C.1 9C.2

General Comments Allowable Stresses 9C.2.1 Axial Stress 9C.3 Stability Requirements 9C.4 Minimum Thickness Requirement 9C.5 Code Checking 9C.5.1 Design Steps 9C.6 Member Selection 9C.7 Member Selection by Optimization 9C.8 Tabulated Results of Steel Design 9C.9 Parameter Table for IS802 9C.10 Calculation of Net Section Factor 9C.11 Example Problem No. 28

9D Design Per Indian Cold Formed Steel Code 9D.1 9D.2 9D.3

Section 10

General Cross-Sectional Properties Design Procedure

Japanese Codes

10A Concrete Design Per AIJ 10A.1 10A.2 10A.3 10A.4 10A.5 10A.6 10A.7 10A.8

Design Operations Section Types for Concrete Design Member Dimensions Slenderness Effects and Analysis Consideration Beam Design Column Design Slab/Wall Design Design Parameters

10B Steel Design Per AIJ 10B.1 10B.2 10B.3 10B.4 10B.5 10B.6 10B.7 10B.8

General Analysis Methodology Member Property Specifications Built-in Japanese Steel Section Library Member Capacities Combined Loading Design Parameters Code Checking

9-71 9-71 9-71 9-72 9-74 9-76 9-76 9-77 9-78 9-78 9-79 9-81 9-83 9-85

9-93 9-93 9-93 9-94

1010-1 10-1 10-1 10-1 10-2 10-3 10-5 10-7 10-8

10-11 10-11 10-12 10-12 10-12 10-18 10-22 10-23 10-25

10B.9

Section 11

Member Selection

Mexican Codes

11A Concrete Design Per MEX NTC 1987 11A.1 11A.2 11A.3 11A.4 11A.5 11A.6 11A.7 11A.8 11A.9

Design Operations Section Types for Concrete Design Member Dimensions Design Parameters Beam Design Column Design Column Interaction Column Design Output Slab Design

11B Steel Design Per Mexican Code 11B.1 11B.2 11B.3 11B.4 11B.5 11B.6 11B.7 11B.8 11B.9 11B.10 11B.11 11B.12 11B.13

Section 12

General Limit States Design Fundamentals Member End Forces and Moments Section Classification Member in Axial Tension Axial Compression Flexural Design Strength Design for Shear Combined Compression Axial Force and Bending Combined Tension Axial Force and Bending Design Parameters Code Checking and Member Selection Tabulated Results of Steel Design

Russian Codes

12A Concrete Design Per Russian Code 12A.1 12A.2 12A.3 12A.4 12A.5

General Input Data Beams Columns 2D (two dimensional) element (slabs, walls, shells)

12B Steel Design Per Russian Code 12B.1 12B.2 12B.3

General Axial tension members Axial compression members

10-26

1111-1 11-1 11-1 11-2 11-3 11-6 11-10 11-11 11-12 11-13

11-15 11-15 11-16 11-17 11-18 11-18 11-19 11-20 11-22 11-22 11-22 11-23 11-27 11-28

1212-1 12-1 12-3 12-10 12-16 12-21

12-25 12-25 12-26 12-26

12B.4 12B.5 12B.6 12B.7

Section 13

Flexural members Eccentrical compression/tension members Input Data Section selection and check results

South African Codes

13A Concrete Design Per SABS 0100-1 13A.1 13A.2 13A.3 13A.4 13A.5

Design Operations Design Parameters Member Dimensions Beam Design Column Design

13B Steel Design Per SAB Standard SAB0162–1: 1993 13B.1 13B.2 13B.3 13B.4 13B.5 13B.6 13B.7 13B.8 13B.9 13B.10 13B.11

Section 14

General Analysis Methodology Member Property Specifications Built-in Steel Section Library Section Classification Member Resistances Design Parameters Code Checking Member Selection Tabulated Results of Steel Design Verification Problems

American Aluminum Code

14 Design Per American Aluminum Code 14.1 14.2 14.3 14.4 14.5 14.6

General Member Properties Design Procedure Design Parameters Code Checking Member Selection

12-27 12-28 12-29 12-45

1313-1 13-1 13-1 13-3 13-4 13-6

13-9 13-9 13-10 13-10 13-10 13-16 13-16 13-20 13-22 13-24 13-24 13-26

1414-1 14-1 14-1 14-3 14-4 14-8 14-8

Section 15

American Transmission Tower Code

15A Steel Design Per ASCE 10-97 15A.1 15A.2 15A.3 15A.4 15A.5

General Comments Allowable Stresses Per ASCE 10-97 Critical conditions used as criteria to determine Pass/Fail status Design Parameters Code Checking and Member Selection

15B Steel Design Per ASCE Manuals And Reports 15B.1 15B.2 15B.3 15B.4 15B.5

Section 16

General Comments Allowable Stresses Per ASCE (Pub.52) Design Parameters Code Checking and Member Selection Parameter Definition Table

American A.P.I. Code

16 Steel Design Per API 16.1 16.2

16.3 16.4 16.5 16.6 16.7 16.8 16.9 16.10 16.11 16.12 16.13 16.14 16.15 16.16

Design Operations Allowables Per API Code 16.2.1 Tension Stress 16.2.2 Beam Stress Stress due to Compression Bending Stress Combined Compression and Bending Design Parameters Code Checking Member Selection Truss Members Punching Shear Generation of the Geometry File Chord Selection and Qf Parameter External Geometry File Limitations Tabulated Results of Steel Design The Two-Step Process

1515-1 15-1 15-2 15-3 15-3 15-3

15-7 15-7 15-8 15-9 15-9 15-10

1616-1 16-1 16-2 16-2 16-2 16-3 16-3 16-4 16-4 16-7 16-7 16-8 16-8 16-9 16-10 16-11 16-12 16-13 16-14

Introduction This publication has been prepared to provide information pertaining to the various international codes supported by STAAD. These codes are provided as additional codes by Research Engineers. In other words, they do not come with the standard package. Hence, information on only some of the codes presented in this document may be actually pertinent to the individual user's package. Users may locate the information for the appropriate code by referring to the Table of Contents shown on the previ ous few pages. This document is to be used in conjunction with the STAAD Technical Reference Manual and the STAAD Examples Manual. Effort has been made to provide some basic information about the analysis considerations and the logic used in the design ap proach. A brief outline of the factors affecting the design along with references to the corresponding clauses in the codes is also provided. Examples are provided at the appropriate places to facilitate ease of understanding of the usage of the commands a nd design parameters. Users are urged to refer to the Examples Manual for solved problems that use the commands and features of STAAD. Since the STAAD output contains references to the clauses in the code that govern the design, users are urged to consult the documentation of the code of that country for additional details on the design criteria.

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Section 1

Australian Codes

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1-1

Concrete Design Per AS3600 - 2001 Section

1A

1A.1 Design Operations STAAD has the capabilities for performing concrete design based on the Australian code AS3600-2001 Australian Standard-Concrete Structures.

1A.2 Section Types for Concrete Design The following types of cross sections for concrete members can be designed. For Beams

Prismatic (Rectangular & Square)

For Columns

Prismatic (Rectangular, Square and Circular)

1A.3 Member Dimensions Concrete members which will be designed by the program must have certain section properties input under the MEMBER PROPERTY command. The following example shows the required input:

Concrete Design Per AS 3600

1-2

Section 1A

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350. In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350 mm diameter. It is absolutely imperative that the user not provide the cross section area (AX) as an input.

1A.4 Design Parameters The program contains a number of parameters which are needed to perform the design. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 1A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.

1A.5 Slenderness Effects and Analysis Consideration Slenderness effects are extremely important in designing compression members. There are two options by which the slenderness effect can be accommodated. One option is to perform an exact analysis which will take into account the influence of axial loads and variable moment of inertia on member stiffness and fixed end moments, the effect of deflections on moment and forces and the effect of the duration of loads. Another option is to approximately magnify design moments.

Section 1A

STAAD has been written to allow the use of the first option. To perform this type of analysis, use the command PDELTA ANALYSIS instead of PERFORM ANALYSIS. The PDELTA ANALYSIS will accommodate the requirements of the second order analysis described by AS 3600, except for the effects of the duration of the loads. It is felt that this effect may be safely ignored because experts believe that the effects of the duration of loads are negligible in a normal structural configuration. Although ignoring load duration effects is somewhat of an approximation, it must be realized that the evaluation of slenderness effects is also by an approximate method. In this method, additional moments are calculated based on empirical formula and assumptions on sidesway. Considering all of the above information, a PDELTA ANALYSIS, as performed by STAAD may be used for the design of concrete members. However the user must note that to take advantage of this analysis, all the combinations of loading must be provided as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during the P-delta analysis based on the deflections. Also, note that the proper factored loads (like 1.5 for dead load etc.) should be provided by the user. STAAD does not factor the loads automatically.

1A.6 Beam Design Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,. 75,.8,.9 and 1). All of these sections are scanned to determine the design force envelopes.

1-3


1-4

Section 1A

Design for Flexure Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections is designed to resist both of these critical sagging and hogging moments. Currently, design of singly reinforced sections only is permitted. If the section dimensions are inadequate as a singly reinforced section, such a message will be permitted in the output. Flexural design of beams is performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account the changed effective depths of sections calculated on the basis of reinforcement provided after the preliminary design. Final provisions of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per AS 3600. Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the detailer taking into account of other practical consideration), user has the choice of printing reinforcements provided by STAAD at 13 equally spaced sections from which the final detailed drawing can be prepared. Design for Shear Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design is performed at 13 equally spaced sections (0.to 1.) for the maximum shear forces amongst the active load cases and the associated torsional moments. Shear capacity calculation at different sections without the shear reinforcement is based on the actual tensile reinforcement provided by STAAD program. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections.

Section 1A

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE AUSTRALIAN FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEM 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

1A.7 Column Design Columns are designed for axial forces and biaxial moments at the ends. All active load cases are tested to calculate reinforcement. The loading which yields maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. By default, square and rectangular columns are designed with reinforcement distributed on each side equally. That means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by AS 3600 have been taken care of in the column design of STAAD.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE AUSTRALIAN FYMAIN 415 ALL FC 35 ALL

1-5


1-6

Section 1A

CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN

1A.8 Slab/Wall Design To design a slab or wall, it must be modeled using finite elements. The command specifications are in accordance with Chapter 2, and Chapter 6 of the Technical Reference Manual. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Section 3.8 of the Technical Reference Manual). The r einforcement required to resist Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist My moment is denoted as transverse reinforcement. The parameters FYMAIN, FC, MAXMAIN, MINMAIN and CLEAR listed in Table 1A.1 are relevant to slab design. Other parameters mentioned in Table 1A.1 are not applicable to slab design.

Z Y My

X Mx TRANS. My

Mx LONG.

Section 1A

1-7

Example of Input Data for Slab/Wall Design UNIT NEWTON MMS START CONCRETE DESIGN CODE AUSTRALIAN FYMAIN 415 ALL FC 25 ALL CLEAR 40 ALL DESIGN ELEMENT 15 TO 20 END CONCRETE DESIGN

Table 1A.1 Australian Concrete Design-AS 3600- Parameters Parameter Name

Default Value

FYMAIN*

450/mm2

FYSEC* FC** CLEAR

450/mm

2

40 N/mm

2

Description Yield Stress for main reinforcing steel. Yield Stress for secondary reinforcing steel. Concrete Yield Stress.

25 mm

For beam members.

40 mm

For column members

MINMAIN

10 mm

Minimum main reinforcement bar size.

MAXMAIN

60 mm

Maximum main reinforcement bar size.

MINSEC

8 mm

Minimum secondary reinforcement bar size.

MAXSEC

12 mm

Maximum secondary reinforcement bar size.

RATIO

4.0

Maximum percentage of longitudinal reinforcement in columns.

WIDTH

ZD

Width to be used for design. This value defaults to ZD as provided under MEMBER PROPERTIES.

DEPTH

YD

Total depth to be used for design. This value defaults to YD as provided under MEMBER PROPERTIES.


1-8

Section 1A

Table 1A.1 Australian Concrete Design-AS 3600- Parameters Parameter Name

Default Value

TRACK

0.0

Description BEAM DESIGN: For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output. COLUMN DESIGN: With TRACK = 0.0, reinforcement details are printed.

REINF

0.0

Tied column. A value of 1.0 will mean spiral reinforcement.

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. * - applicable values are 250, 400, 450 and 500 as per Table 6.2.1 of the AS 3600-2001 code. ** - applicable values are 20, 25, 32, 40, 50, and 65 as per Clause 6.1.1.1 of the AS 3600-2001 code.

1-9

Steel Design Per AS 4100 - 1998 Section

1B

1B.1 General This section presents some general statements regarding the implementation of the specifications recommended by Standards Australia for structural steel design (AS 4100) in STAAD. The design philosophy and procedural logistics are based on the principles of elastic analysis and limit state method of design. Facilities are available for member selection as well as code checking. The design philosophy embodied in this specification is based on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit-state are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned to resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria as augmented by the designer in specification of allowable member depths, desired section type, or other such parameters. The code checking portion of the program checks whether code requirements for each selected section are met and identifies the governing criteria.

Steel Design Per AS 4100-1998

1-10

Section 1B

The following sections describe the salient features of the STAAD implementation of AS 4100. A detailed description of the design process along with its underlying concepts and assumptions is available in the specification document.

1B.2 Analysis Methodology Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis or P-Delta analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.

1B.3 Member Property Specifications For specification of member properties, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

1B.4 Built-in Steel Section Library The following information is provided for use when the built -in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members. An example of the member property specification in an input file is provided at the end of this section.

Section 1B

A complete listing of the sections available in the built-in steel section library may be obtained by using the tools of the graphical user interface. Following are the descriptions of different types of sections. UB Shapes These shapes are designated in the following way.

20 TO 30 TA ST UB150X14.0 36 TO 46 TA ST UB180X16.1 UC Shapes The designation for the UC shapes is similar to that for the UB shapes.

25 TO 35 TA ST UC100X14.8 23 56 TA ST UC310X96.8 Welded Beams Welded Beams are designated in the following way.

25 TO 35 TA ST WB700X115 23 56 TA ST WB1200X455 Welded Columns Welded Columns are designated in the following way.

25 TO 35 TA ST WC400X114 23 56 TA ST WC400X303

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1-12

Section 1B

Parallel Flange Channels Shown below is the syntax for assigning names of channel sections.

1 TO 5 TA ST PFC75 6 TO 10 TA ST PFC380 Double Channels Back to back double channels, with or without a spacing between them, are available. The letter D in front of the section name will specify a double channel.

11 TA D PFC230 17 TA D C230X75X25 SP 0.5 In the above set of commands, member 11 is a back to back double channel PFC230 with no spacing in between. Member 17 is a double channel PFC300 with a spacing of 0.5 length units between the channels. Angles Two types of specification may be used to describe an angle. The standard angle section is specified as follows:

16 20 TA ST A30X30X6 The above section signifies an angle with legs of length 30mm and a leg thickness of 6 mm. This specification may be used when the local Z axis corresponds to the z-z axis specified in Chapter 2. If the local Y axis corresponds to the z-z axis, type specification "RA" (reverse angle) may be used.

17 21 TA RA A150X150X16

Section 1B

Double Angles Short leg back to back or long leg back to back double angles can be specified by means of input of the words SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose.

33 35 TA SD A65X50X5 SP 0.6 37 39 TA LD A75X50X6 43 TO 47 TA LD A100X75X10 SP 0.75 Tubes (Rectangular or Square Hollow Secti ons) Tubes can be assigned in 2 ways. In the first method, the designation for the tube is as shown below. This method is meant for tubes whose property name is available in the steel table. In these examples, members 1 to 5 consist of a 2X2X0.5 inch size tube section, and members 6 to 10 consist of 10X5X0.1875 inch size tube section. The name is obtained as 10 times the depth, 10 times the width, and 16 times the thickness.

1 TO 5 TA ST TUB20202.5 6 TO 10 TA ST TUB100503.0 In the second method, tubes are specified by their dimensions. For example,

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height of 8 length units, width of 6 length units, and a wall thickness of 0.5 length units. Only code checking, no member selection, will be performed for TUBE sections specified in this latter manner.

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1-14

Section 1B

Pipes (Circular Hollow Sections) Pipes can be assigned in 2 ways. In the first method, the designation for the pipe is as shown below. This method is meant for pipes whose property name is available in th e steel table.

1 TO 5 TA ST PIP180X5 6 TO 10 TA ST PIP273X6.5 In the second method, pipe sections may be provided by specifying the word PIPE followed by the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0 specifies a pipe with outside diameter of 25 length units and inside diameter of 20 length units. Only code checking, no member selection, will be performed on pipes specified in this latter manner.

Sample File Containing Australian Shapes STAAD SPACE UNIT METER KN JOINT COORD 1 0 0 0 11 100 0 0 MEMB INCI 1 1 2 10 UNIT CM MEMBER PROPERTIES AUSTRALIAN * UB SHAPES 1 TA ST UB200X25.4 * UC SHAPES 2 TA ST UC250X89.5 * CHANNELS 3 TA ST PFC125

Section 1B

* DOUBLE CHANNELS 4 TA D PFC200 * ANGLES 5 TA ST A30X30X6 * REVERSE ANGLES 6 TA RA A150X150X16 * DOUBLE ANGLES - SHORT LEGS BACK TO BACK 7 TA SD A65X50X5 SP 0.6 * DOUBLE ANGLES - LONG LEGS BACK TO BACK 8 TA LD A100X75X10 SP 0.75 * TUBES (RECTANGULAR OR SQUARE HOLLOW SECTIONS) 9 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 * PIPES (CIRCULAR HOLLOW SECTIONS) 10 TA ST PIPE OD 25.0 ID 20.0 PRINT MEMB PROP FINI

1B.5 Section Classification The AS 4100 specification allows inelastic deformation of section elements. Thus, local buckling becomes an important criterion. Steel sections are classified as compact, non-compact or slender depending upon their local buckling characteristics. This classification is a function of the geometric properties of the section. The design procedures are different depending on the section class. STAAD determines the section classification for the standard shapes and user specified shapes. Design is performed for all three categories of section as mentioned above.

1B.6 Member Resistances The member resistance is calculated in STAAD according to the procedures outlined in AS 4100. This depends on several factors such as members' unsupported lengths, cross-sectional properties, support conditions and so on. The procedure adopted in STAAD for calculating the member resistance is explained here.

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Section 1B

Axial Tension The criteria governing the capacity of tension members are based on two limit states. Limit State of yielding of the gross section is intended to prevent excessive elongation of the member. The second limit state involves fracture at the section with the minimum effective net area. The user through the use of the parameter NSF (see Table 1B.1) may specify the net section area. STAAD calculates the tension capacity of a member based on these two limit states per Cl.7.1 and Cl.7.2 respectively of AS 4100. Parameters FYLD, FU, Kt and NSF are applicable for these calculations. Axial Compression The compressive strength of members is determined based on Clause 6.1 of the code. It is taken as the lesser of nominal section capacity and nominal member capacity. Nominal section capacity is a function of form factor (Cl.6.2.2), net area of the cross section and yield stress of the material. The user through the use of the parameter NSC (see Table 1B.1) may specify the net section area. Note here, that this parameter is different from that corresponding to tension. The program automatically calculates form factor. Nominal member capacity is a function of nominal section capacity and member slenderness reduction factor (Cl.6.3.3). Here user is required to supply the value of  b (Cl.6.3.3). Table 1B.1 gives the default value of this parameter (named ALB). The effective length for the calculation of compressive strength may be provided through the use of the parameters KY, KZ, LY and LZ (see Table 1B.1). Bending The allowable bending moment of members is determined as the lesser of nominal section capacity and nominal member capacity (ref. Cl.5.1). The nominal section moment capacity is the capacity to resist cross-section yielding or local buckling and is expressed as the product of yield stress of material and effective section modulus (ref. Cl.5.2). The effective section modulus is a function of section type i.e. compact, non -compact or slender. The nominal

Section 1B

member capacity depends on overall flexural -torsional buckling of the member (ref.Cl.5.3). Interaction of axial force and bending The member strength for sections subjected to axial compression and uniaxial or biaxial bending is obtained through the use of interaction equations. Here also the adequacy of a member is examined against both section (ref. Cl.8.3.4) and member capacity (ref.Cl.8.4.5). If the summation of the left hand side of the equations, addressed by the above clauses, exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 1B.1), the member is considered to have FAILed under the loading condition. Shear Shear capacity of cross section is taken as the shear yield capacity. User may refer to Cl.5.11 in this context. Once the capacity is obtained, the ratio of the shear force acting on the cross section to the shear capacity of the section is calculated. If any of the ratios (for both local Y & Z-axes) exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 1B.1), the section is considered to have failed under sh ear.

1B.7 Design Parameters The design parameters outlined in Table 1B.1 may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program and thus allow the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure.

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Section 1B

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 1B.1- Australian Steel Design Parameters Parameter Name

Default Value

Description

KY

1.0

K value for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.

KZ

1.0

K value for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.

LY

Member Length

Length for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.

LZ

Member Length

Length for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.

FYLD

250.0 MPa

Yield strength of steel.

FU

500.0 MPa

Ultimate strength of steel.

NSF

1.0

Net section factor for tension members.

MAIN

0.0

0.0 = Check slenderness ratio against the limits. 1.0 = Suppress the slenderness ratio check. 2.0 = Check slenderness ratio only for column buckling, not for web (See Section 3B.6, Shear)

TRACK

0.0

0.0 = Report only minimum design results. 1.0 = Report design strengths also. 2.0 = Provide full details of design.

DMAX

45.0 in.

Maximum allowable depth (Applicable for member selection)

DMIN

0.0 in.

Minimum required depth (Applicable for member selection)

RATIO

1.0

Permissible ratio of actual load effect to the

Section 1B

1-19

Table 1B.1- Australian Steel Design Parameters Parameter Name

IST

Default Value

Description design strength.

1

Steel type - 1 - SR, 2 - HR, 3 - CF, 4 - LW, 5 - HW

PHI

0.9

Capacity reduction factor

NSC

1.0

Net section factor for compression members = An / Ag (refer cl. 6.2.1)

ALM

1.0

Moment modification factor (refer cl. 5.6.1.1)

ALB

0.0

Member section constant (refer cl. 6.3.3)

KT

1.0

Correction factor for distribution of forces (refer cl. 7.2)

BEAM

0.0

0.0 = design only for end moments and those at locations specified by SECTION command. 1.0 = Perform design for moments at twelfth points along the beam.

UNT

Member Length

Unsupported length in bending compression of the top flange for calculating moment resistance.

UNB

Member Length

Unsupported length in bending compression of the bottom flange for calculating moment resistance.

DFF

None (Mandatory for deflection check)

DJ1

Start Joint of member

Joint No. denoting start point for calculation of “deflection length”

DJ2

End Joint of member

Joint No. denoting end point for calculation of “deflection length”

“Deflection Length”/ Maxm. Allowable local deflection.


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Section 1B

1B.8 Code Checking The purpose of code checking is to check whether the provided section properties of the members are adequate. The adequacy is checked as per AS 4100 requirements. Code checking is done using forces and moments at every twelfth point along the beam. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start joint) and magnitudes of the governing forces and moments are also printed. The extent of detail of the output can be controlled by using the TRACK parameter.

Example of commands for CODE CHECKING: UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 RATIO 0.9 ALL CHECK CODE MEMB 3 4 Code checking cannot be performed on composite and prismatic sections.

1B.9 Member Selection The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a

Section 1B

channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Composite and prismatic sections cannot be selected.

Example of commands for MEMBER SELECTION: UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 RATIO 0.9 ALL SELECT MEMB 3 4

1B.10 Tabulated Results of Steel Design Results of code checking and member selection are presented in a tabular format. The term CRITICAL COND refers to the section of the AS 4100 specification which governs the design.

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Section 1B

Section 2

British Codes

Kjahds;akh

2-1

Concrete Design Per BS8110 Section

2A

2A.1 Design Operations It is strongly recommended that the user should perform new concrete design using the RC Designer Module. The following is provided to allow old STAAD files to be run. STAAD has the capability of performing design of concrete beams, columns and slabs according to BS8110. The 1997 revision of the code is currently implemented. Given the width and depth (or diameter for circular columns) of a section, STAAD will calculate the required reinforcement to resist the forces and moments.

2A.2 Design Parameters The program contains a number of parameters which are needed to perform and control the design to BS8110. These parameters not only act as a method to input required data for code calculations but give the Engineer control over the actual design process. Default values of commonly used parameters for conventional design practice have been chosen as the basis. Table 2A.1 contains a complete list of available parameters with their default values. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

Concrete Design Per BS8110

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Section 2A

Table 2A.1 – British Concrete Design-BS8110-Parameters Parameter Name

Default Value

Description

FYMAIN

*460 N/mm2

Yield Stress for main reinforcement (For slabs, it is for reinforcement in both directions)

FYSEC

*460N/mm2

Yield Stress for secondary reinforcement a. Applicable to shear bars in beams

FC

* 30N/mm2

Concrete Yield Stress / cube strength

MINMAIN

8mm

Minimum main reinforcement bar size Acceptable bar sizes: 6 8 10 12 16 20 25 32 40 50

MINSEC

8mm

Minimum secondary bar size a. Applicable to shear reinforcement in beams

CLEAR

* 20mm

Clearance of reinforcement measured from concrete surface to closest bar perimeter.

50mm

Maximum required reinforcement bar size Acceptable bars are per MINMAIN above.

MAXMAIN SFACE

*0.0

Face of support location at start of beam. (Only applicable for shear - use MEMBER OFFSET for bending )

EFACE

*0.0

Face of support location at end of beam. (NOTE : Both SFACE & EFACE must be positive numbers.)

TRACK

0.0

0.0 = Critical Moment will not be printed with beam design report. Column design gives no detailed results. 1.0 = For beam gives min/max steel % and spacing. For columns gives a detailed table of output with additional moments calculated. 2.0 = Output of TRACK 1.0 List of design sag/hog moments and corresponding required steel area at each section of member

MMAG

1.0

Factor by which column design moments are magnified

NSECTION

10

Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20.

WIDTH

*ZD

Width of concrete member. This value default is as provided as ZD in MEMBER PROPERTIES.

DEPTH

*YD

Depth of concrete member. This value default is as provided as YD in MEMBER PROPERTIES.

Section 2A

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Table 2A.1 – British Concrete Design-BS8110-Parameters Parameter Name BRACE

Default Value 0.0

Description 0.0 = 1.0 = 2.0 = 3.0 =

Column braced in both directions. Column unbraced about local Z direction only Column unbraced about local Y direction only Column unbraced in both Y and Z directions

ELY

1.0

Member length factor about local Y direction for column design.

ELZ

1.0

Member length factor about local Z direction for column design.

SRA

0.0

0.0 = -500 = A=

Orthogonal reinforcement layout without considering torsional moment Mxy -slabs only Orthogonal reinforcement layout with Mxy used to calculate WOOD & ARMER moments for design. Skew angle considered in WOOD & ARMER equations where A is the angle in degrees.

0.0 = No serviceability check performed. 1.0 = Perform serviceability check for beams as if they were continuous. 2.0 = Perform serviceability check for beams as if they were simply supported. 3.0 = Perform serviceability check for beams as if they were cantilever beams. * Provided in current unit system SERV

0.0


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Section 2A

2A.3 Slenderness Effects and Analysis Considerations STAAD provides the user with two methods of accounting for the slenderness effects in the analysis and design of concrete members. The first method is equivalent to the procedure presented in BS8110 Part 1 1985 Section 3.8.2.2 In this section, the code recognizes that additional moments induced by deflection are present and states that these 'secondary' moments are accounted for by the design formula in Section 3.8.3. This is the method used in the design for concrete in STAAD. Alternatively STAAD houses a PDELTA ANALYSIS facility, which allows the effects of these second order moments to be considered in the analysis rather than the design. In a PDELTA analysis, after solving the joint displacements of the structure, the additional moments induced in the structure are calculated. These can be compared to those calculated using the formulation of BS8110.

2A.4 Member Dimensions Concrete members that are to be designed by STAAD must have certain section properties input under the MEMBER PROPERTIES command. The following example demonstrates the required input:

UNIT MM MEMBER PROPERTIES *RECTANGULAR COLUMN 300mm WIDE X 450mm DEEP 1 3 TO 7 9 PRISM YD 450. ZD 300. *CIRCULAR COLUMN 300mm diameter 11 13 PR YD 300. * T-SECTION - FLANGE 1000.X 200.(YD-YB) * - STEM 250(THICK) X 350.(DEEP)

Section 2A

14 PRISM YD 550. ZD 1000. YB 350. ZB 250. In the above input, the first set of members are rectangular (450mm depth x 300mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 300mm diameter. Note that area (AX) is not provided for these members. If shear area areas ( AY & AZ ) are to be considered in analysis, the user may provide them along with YD and ZD. Also note that if moments of inertias are not provided, the program will calculate them from YD and ZD. Finally a T section can be considered by using the third definition above.

2A.5 Beam Design Beam design includes both flexure and shear. For both typ es of beam action, all active beam loadings are scanned to create moment and shear envelopes and locate the critical sections. The total number of sections considered is ten, unless that number is redefined with the NSECTION parameter. From the critical moment values, the required positive and negative bar pattern is developed with cut-off lengths calculated to include required development length. Shear design as per BS8110 clause 3.4.5 has been followed and the procedure includes critical shear values plus torsional moments. From these values, stirrup sizes are calculated with proper spacing. The program will scan from each end of the member and provide a total of two shear regions at each, depending on the change of shear distribution along the beam. If torsion is present, the program will also consider the provisions of BS8110 - Part 2 section 2.4. A table of shear and/or combined torsion is then provided with critical shear. Stirrups not bent up bars are assumed in the design. Table 2A.2 shows a sample output of an actual reinforcement pattern developed by STAAD. The following annotations apply to Table 2A.2

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Section 2A

1) LEVEL 2) 3) 4) 5) 6)

- Serial number of the bar centre which may contain one or more bar groups. HEIGHT - Height of bar level from the soffit of the beam in relation to its local y axis. BAR INFO - Reinforcement bar information specifying number of bars and their size. FROM - Distance from the start of the beam to the start of the reinforcing bar. TO - Distance from the start of the beam to the end of the reinforcing bar. ANCHOR - States whether anchorage, either a hook or (STA,END) continuation, is needed at start (STA) or at the end (END). TABLE 2A.2- ACTUAL DESIGN OUTPUT BEAM

N O. 2

DESIGN

R E S U L T S - FLEXURE

LEN - 3854. mm FY - 460. FC - 30. SIZE - 300. X 600. mm LEVEL

HEIGHT mm

BAR INFO

FROM mm

TO mm

ANCHOR STA END

1 29. 6- 8 MM 0. 3854. YES YES CRITICAL POS MOMENT = 55.31 KN-M AT 1927. mm, LOAD 3 REQD STEEL = 261.mm2, ROW = 0.0014, ROWMX= 0.0400, ROWMN = 0.0013 MAX/MIN/ACTUAL BAR SPACING = 189./ 33./ 40. mm 2 565. 6- 8 MM 0. 3854. YES YES CRITICAL NEG MOMENT = 55.31 KN-M AT 1927. mm, LOAD 4 REQD STEEL = 261.mm2, ROW = 0.0014, ROWMX= 0.0400, ROWMN = 0.0013 MAX/MIN/ACTUAL BAR SPACING = 189./ 33./ 40. mm BEAM

N O. 2

DESIGN

R E S U L T S - SHEAR

PROVIDE SHEAR AND TORSIONAL LINKS AS FOLLOWS FROM - TO SHEAR TORSN LOAD LINK NO. SPACING mm C/C mm kN kNm S T SIZE S T S+T S T S+T END 1 1156 84.4 12 4 2 8 mm 3 5 9 335 199 116 2697 END 2 86.6 12 3 2 8 mm 3 5 9 335 199 116 EXTRA PERIPHERAL LONGITUDINAL TORSION STEEL: 402 mm2 EVENLY DISTRIBUTED * TORSIONAL RIGIDITY SHOULD CONFORM TO CL.2.4.3 - BS8110 *

Section 2A

2A.6 Column Design Columns are designed for axial force and biaxial bending at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement is called the critical load and is displayed. The requirement s of BS8110 Part 1 section 3.8 are followed, with the user having control on the effective length in each direction by using the ELZ and ELY parameters as described in table 2A.1. Bracing conditions are controlled by using the BRACE parameter. The program will then decide whether or not the column is short or slender and whether it requires additional moment calculations. For biaxial bending, the recommendations of 3.8.4.5 of the code are considered. Column design is done for square, rectangular and circular sections. For rectangular and square sections, the reinforcement is always assumed to be arranged symmetrically. This causes slightly conservative results in certain cases. Table 2A.3 shows typical column design results. Using parameter TRACK 1.0, th e detailed output below is obtained. TRACK 0.0 would merely give the bar configuration, required steel area and percentage, column size and critical load case.

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2-8

Section 2A TABLE 2A.3 -COLUMN DESIGN OUTPUT COLUMN

No. 1

DESIGN

RESULTS

FY - 460. FC -30. N/MM2 RECT SIZE - 300. X 600. MM, AREA OF STEEL REQUIRED = 875. SQ. MM. BAR

CONFIGURATION

REINF PCT.

LOAD

8 12 MM 0.486 3 (ARRANGE COLUMN REINFORCEMENTS SYMMETRICALLY)

LOCATION EACH END

BRACED /SHORT in z E.L.z = 4500 mm ( 3.8.1.3 & 5 ) BRACED /SLENDER in y E.L.y = 4500 mm ( 3.8.1.3 & 5 ) END MOMS. MZ1 = 1 MZ2 = 25 MY1 = 53 MY2 = 40 SLENDERNESS MOMTS. KNM: MOMZ = 0 MOMY = 2 DESIGN LOADS KN METER: MOM. = 64 AXIAL LOAD = 84 DESIGNED CAP. KN METER: MOM. = 64 AXIAL CAP.= 187

2A.7 Slab Design Slabs are designed to BS8110 specifications. To design a slab, it must first be modelled using finite elements. The command specifications are in accordance with section 5.51.3 of the Technical Reference Manual. A typical example of element design output is shown in Table 2A.4. The reinforcement required to resist the Mx m oment is denoted as longitudinal reinforcement and the reinforcement required to resist the My moment is denoted as transverse reinforcement ( Fig. 4.1 ). The following parameters are those applicable to slab design: 1. FYMAIN 2. FC 3. CLEAR

- Yield stress for all reinforcing steel - Concrete grade - Distance from the outer surface to the edge of the bar. This is considered the same on both surfaces.

Section 2A

4. SRA

- Parameter which denotes the angle of the required transverse reinforcement relative to the longitudinal reinforcement for the calculation of WOOD & ARMER design moments.

Other parameters, as shown in Table 2A.1 are not applicable. WOOD & ARMER equations. Ref: R H WOOD CONCRETE 1968 (FEBRUARY) If the default value of zero is used for the parameter SRA, the design will be based on the Mx and My moments which are the direct results of STAAD analysis. The SRA parameter (Set Reinforcement Angle) can be manipulated to introduce WOOD & ARMER moments into the design replacing the pure Mx, My moments. These new design moments allow the Mxy moment to be considered when designing the section. Orthogonal or skew reinforcement may be considered. SRA set to -500 will assume an orthogonal layout. If however a skew is to be considered, an angle is given in degrees measured anticlockwise (positive) from the element local x-axis to the reinforcement bar. The resulting Mx* and My* moments are calculated and shown in the design format. The design of the slab considers a fixed bar size of 16mm in both directions with the longitudinal bar being the layer closest to the slab exterior face. Typical output is as follows:

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2-10

Section 2A TABLE 2A.4 -ELEMENT DESIGN OUTPUT ELEMENT DESIGN SUMMARY-BASED ON 16mm BARS MINIMUM AREAS ARE ACTUAL CODE MIN % REQUIREMENTS. PRACTICAL LAYOUTS ARE AS FOLLOWS: FY=460, 6No.16mm BARS AT 150mm C/C = 1206mm2/metre FY=250, 4No.16mm BARS AT 250mm C/C = 804mm2/metre ELEMENT LONG. REINF MOM-X /LOAD TRANS. REINF MOM-Y /LOAD (mm2/m) (kN-m/m) (mm2/m) (kN-m/m) WOOD & ARMER RESOLVED MOMENTS FOR ELEMENT: 13 UNITS: METER KN LOAD MX MY MXY MX* MY*/Ma* ANGLE 1 0.619 0.249 0.000 2.226 1.855 30.000 TOP 1 0.619 0.249 0.000 0.000 0.000 30.000 BOTT 3 0.437 0.184 -0.007 1.586 1.358 30.000 TOP 3 0.437 0.184 -0.007 0.000 0.000 30.000 BOTT 13 TOP : 195. 2.23 / 1 195. 1.86 / 1 BOTT : 195. 0.00 / 3 195. 0.00 / 3

2A.8 Shear Wall Design Purpose Design of shear walls in accordance with BS 8110 has been added to the features of the program. Description The program implements the provisions of BS 8110 for the d esign of shear walls. It performs in -plane shear, compression, as well as in-plane and out-of-plane bending design of reinforcing. The shear wall is modeled by a single or a combination of Surface elements. The use of the Surface element enables the design er to treat the entire wall as one entity. It greatly simplifies the modeling of the wall and adds clarity to the analysis and design output. The results are presented in the context of the entire wall rather than individual finite elements thereby allowin g users to quickly locate required information.

Section 2A

The program reports shear wall design results for each load case/combination for user specified number of sections given by SURFACE DIVISION (default value is 10) command. The shear wall is designed at these horizontal sections. The output includes the required horizontal and vertical distributed reinforcing, the concentrated (in-plane bending) reinforcing and the link required due to out-of-plane shear. General format: START SHEARWALL DESIGN CODE BRITISH FYMAIN f1 FC f2 HMIN f3 HMAX f4 VMIN f5 VMAX f6 EMIN f7 EMAX f8 LMIN f9 LMAX f10 CLEAR f11 TWOLAYERED f12 KSLENDER f13 DESIGN SHEARWALL LIST shearwall-list END

The next table explains parameters used in the shear wall design command block above. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

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Section 2A

SHEAR WALL DESIGN PARAMETERS Parameter Name FYMAIN FC

Default Value

Description

460 Mpa

Yield strength of steel, in current units.

30 Mpa

Compressive strength of concrete, in current units.

HMIN

6

Minimum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

HMAX

36

VMIN

6

VMAX

36

Maximum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Minimum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Maximum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

EMIN

6

Minimum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

EMAX

36

Maximum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

LMIN

6

Minimum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

LMAX

16

Maximum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

CLEAR TWOLAYERED

25 mm 0

Clear concrete cover, in current units. Reinforcement placement mode:

Section 2A

SHEAR WALL DESIGN PARAMETERS Parameter Name

Default Value

Description 0 - single layer, each direction 1 - two layers, each direction

KSLENDER

1.5

Slenderness factor for finding effective height.

The following example starts from the definition of shear wall and ends at the shear wall design. Example

. . SET DIVISION 12 SURFACE INCIDENCES 2 5 37 34 SUR 1 19 16 65 68 SUR 2 11 15 186 165 SUR 3 10 6 138 159 SUR 4 . . . SURFACE PROPERTY 1 TO 4 THI 18 SUPPORTS 1 7 14 20 PINNED 2 TO 5 GEN PIN 6 TO 10 GEN PIN 11 TO 15 GEN PIN 19 TO 16 GEN PIN . .

2-13


2-14

Section 2A

. SURFACE CONSTANTS E 3150 POISSON 0.17 DENSITY 8.68e-005 ALPHA 5.5e-006 . . START SHEARWALL DES CODE BRITISH UNIT NEW MMS FC 25 FYMAIN 460 TWO 1 VMIN 12 HMIN 12 EMIN 12 DESIGN SHEA LIST 1 TO 4 END Notes 1.

2. 3.

Command SET DIVISION 12 indicates that the surface boundary node-to-node segments will be subdivided into 12 fragments prior to finite element mesh generation. Four surfaces are defined by the SURFACE INCIDENCES command. The SUPPORTS command includes the new support generation routine. For instance, the line 2 TO 5 GEN PIN assigns pinned supports to all nodes between nodes 2 and 5. As the node-to-node distances were previously subdivided by the SET DIVISION 12 command, there will be an additional 11 nodes between nodes 2 and 5. As a result, all 13 nodes will be assigned pinned supports. Please note that the additional 11 nodes are not individually accessible to the user. They are created by the program to enable the finite

Section 2A

4.

5.

element mesh generation and to allow applicati on of boundary constraints. Surface thickness and material constants are specified by the SURFACE PROPERTY and SURFACE CONSTANTS, respectively. The shear wall design commands are listed between lines START SHEARWALL DES and END. The CODE command selects the design code that will be the basis for the design. For British code the parameter is BRTISH. The DESIGN SHEARWALL LIST command is followed by a list of previously defined Surface elements intended as shear walls and/or shear wall components.

Technical Overview The program implements provisions of section 3.9 of BS 8110:Part 1:1997 and relevant provisions as referenced therein, for all active load cases. The wall is designed as unbraced reinforced wall. The following steps are performed for each of the horizontal sections of the wall set using the SURFACE DIVISION command (see Description above). Checking of slenderness limit The slenderness checking is done for out-of-plane direction. For out-of-plane direction, the wall is assumed to be simply supported. Hence, the provisions of clause 3.9.3.2.2 and 3.9.4.2 are applicable. The default effective height is 1.5 times the clear height. User can change the effective height. The limit for slenderness is as per table 3.23 for unbraced wall, which is taken as 30. Design for in-plane bending (denoted by Mz in the shear wall force output) Walls are assumed to be cantilever beams fixed at their base and carrying loads to the foundation.

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2-16

Section 2A

Extreme compression fibre to centroid of tension (concentrated) reinforcement distance, d, is taken as 0.8 horizontal length of the wall. Flexural design of the wall is carried out in accordance with the provisions of clause no. 3.4.4. The flexural (concentrated vertical ) reinforcing is located at both ends (edges) of the len gth of the wall. The edge reinforcement is assumed to be distributed over a length of 0.2 times horizontal length on each side. This length is inclusive of the thickness of the wall. Minimum reinforcements are according to table 3.25. Design for in-plane shear (denoted by Fxy in the shear wall force output) Limit on the nominal shear strength, v is calculated as per clause no. 3.4.5.2. Nominal shear strength of concrete is computed as per table 3.8. The design shear stress is computed as per clause no. 3.4.5.12 taking into consideration the effect of axial load. The area of reinforcement is calculated and checked against the minimum area as per clause no. 3.12.7.4. Design for compression and out-of-plane vertical bending (denoted by Fy and My respectively in the shear wall force output) The wall panel is designed as simply supported (at top and bottom), axially loaded with out-of-plane uniform lateral load, with maximum moments and deflections occurring at mid -height. Design is done as per clause no. 3.8.4 for axially loaded column with uni-axial bending. The minimum reinforcement percentage is as per table 3.25. The maximum reinforcement percentage of vertical reinforcement is as per clause no. 3.12.6.3. Links if necessary are calculated as per the provisions of clause 3.12.7.5.

Section 2A

Design for out-of-plane shear (denoted by Qy in the shear wall force output) The out-of-plane shear arises from out-of-plane loading. The design shear stress is calculated as per 3.4.5.2 and shear strength of concrete section is calculated as per table 3.8 considering vertical reinforcement as tension reinforcement. Shear reinforcements in the form of links are computed as per table 3.7 and the provisions of clause 3.12.7.5. Design for out-of-plane horizontal bending (denoted by Mx in the shear wall force output) The horizontal reinforcement already calculated from in -plane shear is checked against the whole section subjected to out -ofplane bending and axial load. The axial load in this case is the in plane shear. The section is again designed as axially loaded column under uni-axial bending as per the provisions of clause 3.8.4. Extra reinforcement in the form of horizontal bars, if necessary, is reported. Shear Wall Design With Opening The Surface element has been enhan ced to allow design of shear walls with rectangular openings. The automatic meshing algorithm has been improved to allow variable divisions along wall and opening(s) edges. Design and output are available for user selected locations. Description Shear walls modeled in STAAD.Pro may include an unlimited number of openings. Due to the presence of openings, the wall may comprise up with different wall panels. 1.

Shear wall set-up Definition of a shear wall starts with a specification of the surface element perimeter nodes, meshing divisions along node-to-node

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2-18

Section 2A

segments, opening(s) corner coordinates, and meshing divisions of four edges of the opening(s).

SURFACE INCIDENCE n1, ..., ni SURFACE s DIVISION sd1, ..., sdj RECOPENING x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 DIVISION od1, ..., odk where: n1, ..., ni - node numbers on the perimeter of the shear wall, s - surface ordinal number, sd1, ..., sdj - number of divisions for each of the node-to-node distance on the surface perimeter, x1 y1 z1 (...) - coordinates of the corners of the opening, od1, ..., odk - divisions along edges of the opening. Note: If the sd1, ..., sdj or the od1, ..., odk list does not include all nodeto-node segments, or if any of the numbers listed equals zero, then the corresponding division number is set to the default value (=10, or as previously input by the SET DIVISION command). Default locations for stress/force output, design, and design output are set as follows:

SURFACE DIVISION X xd SURFACE DIVISION Y yd where: xd yd

- number of divisions along X axis, - number of divisions along Y axis.

Section 2A

2-19

Note: xd and yd represent default numbers of divisions for each edge of the surface where output is requested. The output is provided for sections located between division segments. For example, if the number of divisions = 2, then the output will be produced for only one section (at the center of the edge). 2.

Stress/force output printing Values of internal forces may be printed out for any user -defined section of the wall. The general format of the command is as follows: PRINT SURFACE FORCE (ALONG ) (AT a) (BETWEEN d1, d2) LIST s1, ...,si where:  a

- local axis of the surface element (X or Y), - distance along the   a xis from start of the member to the full cross-section of the wall, d1, d2 - coordinates in the direction orthogonal to , delineating a fragment of the full cross-section for which the output is desired.** s1, ...,si - list of surfaces for output generation ** The range currently is taken in terms of local axis. If the local axis is directed away from the surface, the negative range is to be entered. Note: If command ALONG is omitted, direction Y (default) is assumed. If command AT is omitted, output is provided for all sections along the specified (or default) edge. Number of sections will be determined from the SURFACE DIVISION X or SURFACE


2-20

Section 2A

DIVISION Y input values. If the BETWEEN command is omitted, the output is generated based on full cross-section width. 3.

Definition of wall panels Input syntax for panel definition is as follows:

START PANEL DEFINITION SURFACE i PANEL j ptype x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 END PANEL DEFINITION where: i j ptype x1 y1 z1 (...)

-

ordinal surface number, ordinal panel number, WALL coordinates of the corners of the panel

Note: Design of COLUMN and BEAM panels is currently not available. 4.

Shear wall design The program implements different provisions of design of walls as per code BS 8110. General syntax of the design command is as follows:

START SHEARWALL DESIGN (...) DESIGN SHEARWALL (AT c) LIST s TRACK tr END SHEARWALL DESIGN Parameter TRACK specifies how detailed the design output should be:

Section 2A

0 - indicates a basic set of results data (default), 1 - full design output will be generated. Note: If the command AT is omitted, the design proceeds for all cross sections of the wall or panels, as applicable, defined by the SURFACE DIVISION X or SURFACE DIVISION Y input values. a.

No panel definition. Design is performed for the specified horizontal full cross section, located at a distance c from the origin of the local coordinates system. If opening is found then reinforcement is provided along sides of openings. The area of horizontal and vertical bars provided along edges of openings is equal to that of the respective interrupted bars.

b.

Panels have been defined. Design is performed for all panels, for the cross-section located at a distance c from the start of the panel.

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2-22

Section 2A

2-23

Steel Design Per BS5950:2000 Section

2B

2B.1 General The design philosophy embodied in BS5950:2000 is built around the concept of limit state design, used today in most modern steel design codes. Structures are designed and proportioned taking into consideration the limit states at which they become unfit for their intended use. Two major categories of limit state are recognized serviceability and ultimate. The primary considerations in ultimate limit state design are strength and stability while that in serviceability limit state is deflection. Appropriate safety factors are used so that the chances of limits being surpassed are acceptably remote. In the STAAD implementation of BS5950:2000, members are proportioned to resist the design loads without exceeding the limit states of strength and stability. Accordingly, the most economic section is selected on the basis of the least weight criteria. This procedure is controlled by the designer in specification of allowable member depths, desired section type or other such parameters. The code checking portion of the program checks that code requirements for each selected section are met and identifies the governing criteria. The complete B.S.C. steel tables for both hot rolled and hollow sections are built into the program for use in specifying member properties as well as for the actual design process. See section 2B.4 for information regarding the referencing of these sections. In addition to universal beams, columns, joists, piles, channels, tees, composite sections, beams with cover plates, pipes, tubes and angles, there is a provision for user provided tables.

Steel Design Per BS5950:2000

2-24

Section 2B

STAAD.Pro 2006, has introduced the additional option to design tapered I shaped (wide flange) beams according to Annex G of BS5950. See section 2B.13 for a complete description. Single Angle Sections Angle sections are un-symmetrical and when using BS 5950:2000 table 25 we must consider four axes; two principal, u -u and v-v and two geometric, a-a and b-b. In a TRACK 2.0 design output, the „Buckling Calculations‟ displays results for the „v-v‟, „a-a‟ and „b-b‟ axes. The effective length for the v-v axis, L vv , is taken as the LVV parameter or LY * KY, if not specified. The a -a and b-b axes are determined by which leg of the angle is fixed by the connection and should be specified using the LEG parameter, see section 2B6.6 for more information on the LEG parameter. The effective length in the a-a axis is taken as LY * KY and the effective length in the b-b axis as LZ * KZ. The following diagram shows the axes for angles which have been defined with either an ST or RA specification and is connected by its longer leg, i.e. a-a axis is parallel to the longer leg. Local Y (u-u)

Local Y (v-v) b

a

a b Local Z (u-u)

Local Z (v-v)

b b a a

ST angle and USER table angles

RA angle

Section 2B


2B.3 Member Property Specifications For specification of member properties, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built -in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

2B.4 Built-In Steel Section Library The following information is provided for use when the built -in steel tables are to be referenced for member property specificati on. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members. Almost all BSI steel sections are available for input. A complete listing of the sections available in the built -in steel section library may be obtained by using the tools of the graphical user interface.

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2-26

Section 2B

Following are the descriptions of different types of section s available: Universal Beams, Columns And Piles All rolled universal beams, columns and pile sections are available. The following examples illustrate the designation scheme.

20 TO 30 TA ST UB305X165X54 33 36 TA ST UC356X406X287 100 102 106 TA ST UP305X305X186 Rolled Steel Joists Joist sections may be specified as they are listed in BSI -80 with the weight omitted. In those cases where two joists have the same specifications but different weights, the lighter section should be specified with an "A" at the end.

10 TO 20 TA ST JO152X127 1 2 TA ST JO127X114A Channel Sections All rolled steel channel sections from the BSI table have been incorporated in STAAD. The designation is similar to that of the joists. The same designation scheme as in BSI tables may be used with the weight omitted.

10 TO 15 TA ST CH305X102 55 57 59 61 TA ST CH178X76

Section 2B

2-27

Double Channels Back to back double channels, with or without spacing between them, are available. The letter "D" in front of the section name will specify a double channel, e.g. D CH102X51, D CH203X89 etc.

51 52 53 TA D CH152X89 70 TO 80 TA D CH305X102 SP 5. (specifies a double channel with a spacing of 5 length units) Tee Sections Tee sections are not input by their actual designations, but instead by referring to the universal beam shapes from which they are cut. For example,

54 55 56 TA T UB254X102X22 (tee cut from UB254X102X22) Angles All equal and unequal angles are available for analysis. Two types of specifications may be used to describe an angle section, either a standard, ST specification or reversed angle, RA specification. Note, however, that only angles specified with an RA specification can be designed. The standard angle section is specified as follows:

15 20 25 TA ST UA200X150X18


2-28

Section 2B

This specification may be used when the local STAAD z -axis corresponds to the V-V axis specified in the steel tables. If the local STAAD y-axis corresponds to the V-V axis in the tables, type specification "RA" (reverse angle) may be used.

35 TO 45 TA RA UA200X150X18 Double Angles Short leg back to back or long leg back to back double angles can be specified by inputting the word SD or LD, respectively, in front of the angle size. In case of an equal angle, either LD or SD will serve the purpose. For example,

14 TO 20 TA LD UA200X200X16 SP 1.5 23 27 TA SD UA80X60X6 "SP" denotes spacing between the individual angle sections. Note that if the section is defined from a Double Angle User Table, then the section properties must be defined with an 11 th value which defines the radius of gyration about an individual sections‟ principal v-v axis (See Technical Reference Manual, 5.19 User Steel Table Specification) Pipes (Circular Hollow Sections) To designate circular hollow sections from BSI tables, use PIP followed by the numerical value of diameter and thickness of the section in mm omitting the decimal section of the value provided for diameter. The following example will illustrate the designation.

10 15 TA ST PIP213.2 (specifies a 21.3 mm dia. pipe with 3.2 mm wall thickness)

Section 2B

Circular hollow sections may also be provided by specifying the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0 (specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units) Only code checking and no member selection will be performed if this type of specification is used. Tubes (Rectangular or Square Hollow Sections) Designation of tubes from the BSI steel table is illustrated below: TUB 400 200 12.5 Square/Rectangular shape Height (mm)

Example:

Thickness (mm) Width (mm)

15 TO 25 TA ST TUB160808.0

Tubes, like pipes, can also be input by their dimensions (Height, Width and Thickness) and not by any table designations.

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 (a tube that has a height of 8, a width of 6, and a wa ll thickness of 0.5 length units) Note that only code checking and no member selection is performed for TUBE sections specified this way.

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2-30

Section 2B

2B.5 Member Capacities The basic measure of capacity of a beam is taken as the plastic moment of the section. This is a significant departure from the standard practice followed in BS449, in which the limiting condition was attainment of yield stress at the extreme fibres of a given section. With the introduction of the plastic moment as the basic measure of capacity, careful consideration must be given to the influence of local buckling on moment capacity. To assist this, sections are classified as either Class 1, plastic, Class 2, compact, Class 3, semi-compact or Class 4, slender, which governs the decision whether to use the plastic or the elastic moment capacity. The section classification is a function of the geometric properties of the section. STAAD is capable of determining the section classification for both hot rolled and built up sections. In addition, for slender sections, BS5950 recommends the use of a 'stress reduction factor' to reduce the design strength. This factor is again a function of the geometry of the section and is automatically determined by STAAD for use in the design process. Axial Tension In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of the effective area as outlined in Section 4.6 of the code. STAAD calculates the tension ca pacity of a given member per this procedure, based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value - see Table 2B.1), proceeding with member selection or code check accordingly. BS 5950 does not have any slenderness limitations for tension members. Compression Compression members must be designed so that the compression resistance of the member is greater than the axial compressive load. Compression resistance is determined accordin g to the compressive strength, which is a function of the slenderness of the

Section 2B

gross section, the appropriate design strength and the relevant strut characteristics. Strut characteristics take into account the considerable influence residual rolling and weld ing stresses have on column behaviour. Based on data collected from extensive research, it has been determined that sections such as tubes with low residual stresses and Universal Beams and Columns are of intermediate performance. It has been found that I -shaped sections are less sensitive to imperfections when constrained to fail about an axis parallel to the flanges. These research observations are incorporated in BS5950 through the use of four strut curves together with a selection of tables to indicate which curve to use for a particular case. Compression strength for a particular section is calculated in STAAD according to the procedure outlined in Annex C of BS5950 where compression strength is seen to be a function of the appropriate Robertson constan t ( representing Strut Curve) corresponding Perry factor, limiting slenderness of the member and appropriate design strength. A departure from BS5950:1990, generally compression members are no longer required to be checked for slenderness limitations, however, this option can be included by specifying a MAIN parameter. Note, a slenderness limit of 50 is still applied on double angles checked as battened struts as per clause 4.7.9. Axially Loaded Members With Moments In the case of axially loaded members with moments, the moment capacity of the member must be calculated about both principal axes and all axial forces must be taken into account. If the section is plastic or compact, plastic moment capacities will constitute the basic moment capacities subject to an elastic limitation. The purpose of this elastic limitation is to prevent plasticity at working load. For semi-compact or slender sections, the elastic moment is used. For plastic or compact sections with high shear loads, the plastic modulus has to be reduced to accommodate the shear loads. The STAAD implementation of BS5950 incorporates the procedure outlined in section 4.2.5 and 4.2.6 to calculate the appropriate moment capacities of the section.

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2-32

Section 2B

For members with axial tension and moment, the interaction formula as outlined in section 4.8.2 is applied based on effective tension capacity. For members with axial compression and moment, two principal interaction formulae must be satisfied – Cross Section Capacity check (4.8.3.2) and the Member Buckling Resistance check (4.8.3.3 ). Three types of approach for the member buckling resistance check have been outlined in BS5950:2000 - the simplified approach (4.8.3.3.1), the more exact approach (4.8.3.3.2) and Annex I1 for stocky members. As noted in the code, in cases where neither the major axis nor the minor axis moment approaches zero, the more exact approach may be more conservative than the simplified approach. It has been found, however, that this is not always the case and STAAD therefore performs both checks, comparing the results in order that the more appropriate criteria can be used. Additionally the equivalent moment factors, m x m y and m yx , can be specified by the user or calculated by the program. Members subject to biaxial moments in th e absence of both tensile and compressive axial forces are checked using the appropriate method described above with all axial forces set to zero. STAAD also carries out cross checks for compression only, which for compact/plastic sections may be more crit ical. If this is the case, COMPRESSION will be the critical condition reported despite the presence of moments. Shear Load A member subjected to shear is considered adequate if the shear capacity of the section is greater than the shear load on the member. Shear capacity is calculated in STAAD using the procedure outlined in section 4.2.3, also 4.4.5 and Annex H3 if appropriate, considering the appropriate shear area for the section specified.

Section 2B

Lateral Torsional Buckling Since plastic moment capacity is the basic moment capacity used in BS5950, members are likely to experience relatively large deflections. This effect, coupled with lateral torsional buckling, may result in severe serviceability limit state. Hence, lateral torsional buckling must be considered carefully. The procedure to check for lateral torsional buckling as outlined in section 4.3 has been incorporated in the STAAD implementation of BS5950. According to this procedure, for a member subjected to moments about the major axis, the 'equiva lent uniform moment' on the section must be less than the lateral torsional buckling resistance moment. For calculation of the buckling resistance moment, the procedure outlined in Annex B.2 has been implemented for all sections with the exception of angles. In Annex B.2., the resistance moment is given as a function of the elastic critical moment, Perry coefficient, and limiting equivalent slenderness, which are calculated within the program; and the equivalent moment factor, m LT , which is determined as a function of the loading configuration and the nature of the load (stabilizing, destabilizing, etc). R. H. S Sections - Additional Provisions Rectangular Hollow sections are treated in accordance with S.C.I. recommendations in cases when the plastic axi s is in the flange. In such cases, the following expressions are used to calculate the reduced plastic moduli: Srx = (A*A/4(B-t))(1-n) [ 2D(B-t)/A + n-1 ] for n>= 2t(D-2t)/A Sry = (A*A/4(D-t))(1-n) [ 2B(D-t)/A + n-1 ] for n>= 2t(B-2t)/A

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2-34

Section 2B

2B.6 Design Parameters Available design parameters to be used in conjunction with BS5950 are listed in table 2B.1 along with their default values. The following items should be noted with respect to their use. 1. (PY – Steel Design Strength ) The design parameter PY should only be used when a uniform design strength for an entire structure or a portion thereof is required. Otherwise the value of PY will be set according to the stipulations of BS5950 table 9 in which the design strength is seen as a function of cross sectional thickness for a particular steel grade (SGR parameter) and particular element considered. Generally speaking this option is not required and the program should be allowed to ascertain the appropriate value. 2. (UNL, LY and LZ - Relevant Effective Length) The values supplied for UNL, LY and LZ should be real numbers greater than zero in current units of length. They are supplied along with or instead of UNF, KY and KZ (which are factors, not lengths) to define lateral torsional buckling and compression effective lengths respectively. Please note that both UNL or UNF and LY or KY values are required even though they are often the same values. The former relates to compression flange restraint for lateral torsional buckling while the latter is the unr estrained buckling length for compression checks. 3. (TRACK - Control of Output Formats ) When the TRACK parameter is set to 0.0, 1.0 or 2.0, member capacities will be printed in design related output (code check or member selection) in kilonewtons per square metre. TRACK 4.0 causes the design to carry out a deflection check, usually with a different load list to the main code check. The members that are to be checked must have the parameters, DFF, DJ1 and DJ2 set.

Section 2B

An example of each TRACK setting follows:TRACK 0.0 OUTPUT

STAAD CODE CHECKING - (BSI )

---------------------------

******************************

ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED) MEMBER

TABLE

RESULT/

CRITICAL COND/

FX

MY

RATIO/

LOADING/

MZ

LOCATION

================================================================= 1 ST UB686X254X170

PASS 86.72 C

BS-4.8.3.2 0.00

0.036

3

-22.02

4.50

--------------------------------TRACK 1.0 OUTPUT ---------------------------

STAAD CODE CHECKING - (BSI ) ******************************


TABLE

RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170 PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 CALCULATED CAPACITIES FOR MEMB 1 UNIT - kN,m SECTION CLASS 4 MCZ= 1141.9 MCY= 120.4 PC= 3451.5 PT= 5739.9 MB= 1084.1 PV= 1597.5 BUCKLING CO-EFFICIENTS m AND n :

m = 1.000

n = 1.000

PZ= 5739.90

MRZ= 1141.9

MRY= 120.4

FX/PZ = 0.02

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2-36

Section 2B TRACK 2.0 OUTPUT

STAAD.Pro CODE CHECKING - (BSI )

---------------------------

***************************

ALL UNITS ARE - KN METE (UNLESS OTHERWISE NOTED) MEMBER

TABLE

RESULT/ CRITICAL COND/ FX

MY

RATIO/

LOADING/

MZ

LOCATION

=================================================================== 1 ST UB533X210X92

PASS

BS-4.3.6

0.902

0.00

0.00

585.41

100 0.00

=================================================================== MATERIAL DATA Grade of steel

= S 275

Modulus of elasticity

= 205 kN/mm2

Design Strength (py) = 275 N/mm2 SECTION PROPERTIES (units - cm) Member Length =

325.00

Gross Area = 117.00

Net Area = 117.00 Major axis

Minor axis

Moment of inertia

: 55229.996

2389.000

Plastic modulus

:

2360.000

356.000

Elastic modulus

:

2072.031

Shear Area

:

58.771

228.285 53.843

DESIGN DATA (units - kN,m) BS5950-1/2000 Section Class

: PLASTIC

Moment Capacity

:

649.0

Reduced Moment Capacity :

649.0

97.9

Shear Capacity

969.7

888.4

Major axis

:

Minor axis 94.2

BUCKLING CALCULATIONS (units - kN,m) (axis nomenclature as per design code) LTB Moment Capacity (kNm) and LTB Length (m): 649.00, 0.001 LTB Coefficients & Associated Moments (kNm):

Section 2B mLT = 1.00 : mx = 1.00

: my = 1.00 : myx = 1.00

Mlt = 585.41 : Mx = 585.41 : My = 0.00 : My = 0.00 CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m): CLAUSE

RATIO

LOAD

FX

VY

VZ

MZ

MY

BS-4.2.3-(Y)

0.329

100

-

292.3

-

-

-

BS-4.3.6

0.902

100

-

292.3

-

585.4

-

BS-4.8.3.2

0.814

100

0.0

68.0

0.0

585.4

0.0

BS-4.8.3.3.1

1.027

100

0.0

-

-

585.4

0.0

BS-4.8.3.3.2

0.902

100

0.0

-

-

585.4

0.0

Annex I.1

0.902

100

0.0

-

-

585.4

0.0

Torsion and deflections have not been considered in the design. _________________________

4. (MX, MY, MYX and MLT – Equivalent Moment Factors) The values for the equivalent moment factors can either be specified directly by the user as a positive value between 0.4 and 1.0 for MX, MY and MYX and 0.44 and 1.0 for MLT. The program can be used to calculate the values for the equivalent moment factors by defining the design member with a GROUP command (see the Technical Reference Manual section 5.16 Listing of Members/Elements/Joints by Specification of GROUPS). The nodes along the beam can then be defined as the location of restraint points with J settings. Additionally for the MLT parameter, the joint can be defined as having the upper flange restrained (positive local Y) with the a U setting or the lower flange restrained (negative local Y) with a L setting.

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2-38

Section 2B

For example, consider a series of 5 beam elements as a single continuous member as shown below:

To enable the steel design, the beam n eeds to be defined as a group, called MainBeam: START GROUP DEFINITION MEMBER _MainBeam 11 2 38 12 3 END GROUP DEFINITION Note that this can be done in the GUI by selecting the beams and clicking on the menu option: „Tools | Create New Group…‟ Therefore, this 5 beam member has 6 joints such that: Joint 1 = Node 3 Joint 2 = Node 1 Joint 3 = Node 33

Section 2B

Joint 4 = Node 14 Joint 5 = Node 7 Joint 6 = Node 2 a.

Consider MX, MY and MYX Say that this member has been restrained in its‟ major axis (local Y) only at the ends. In the minor axis (local Z) it has been restrained at the ends and also at node number 33 (joint 3). For local flexural buckling, it has only been restrained at its ends. Hence:For the major axis, local Y axis:MX _MainBeam J1 J6 For the minor axis, local Z axis:MY _ MainBeam J1 J3 J6 For the lateral flexural buckling, local X axis: MYX _ MainBeam J1 J6

b.

Consider MLT Say that this member has been restrained at its‟ ends against lateral torsional buckling and the top flange has been restrained at node number 33 (joint 3) and only the lower flange at node number 7, (joint 5). Hence: MLT _MainBeam J1 T3 L5 J6 To split the beam into two buckling lengths for L y at joint 14:MY _groupname J1 J4 J6

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2-40

Section 2B

5.

(LEG - Table 25 BS5950 for Fastener Control) The slenderness of single and double angle, channel and tee sections are specified in BS 5950 table 25 depending on the connection provided at the end of the member. To define the appropriate connection, a LEG parameter should be assigned to the member. The following table indicates the value of the LEG parameter required to match the BS5950 connection definition: Clause 4.7.10.2 Single Angle

(a) - 2 bolts (b) - 1 bolt

4.7.10.3 Double Angle

(a) - 2 bolts (b) - 1 bolt (c) - 2 bolts (d) - 1 bolt

short leg long leg short leg long leg

LEG 1.0 3.0 0.0 2.0

short leg long leg short leg long leg long leg short leg long leg short leg

3.0 7.0 2.0 6.0 1.0 5.0 0.0 4.0

4.7.10.4 Channels

(a) - 2 or more rows of bolts (b) - 1 row of bolts

1.0 0.0

4.7.10.5 Tee Sections


1.0 0.0

For single angles, the slenderness is calculated for the geometric axes, a-a and b-b as well as the weak v-v axis. The effective lengths of the geometric axes are defined as:La = KY * KY Lb = KZ * LZ

Section 2B

The slenderness calculated for the v-v axis is then used to calculate the compression strength p c for the weaker principal axis (z-z for ST angles or y-y for RA specified angles). The maximum slenderness of the a-a and b-b axes is used to calculate the compression strength p c for the stronger principal axis. Alternatively for single angles where the connection is not known or Table 25 is not appropriate, by setting the LEG parameter to 10, slenderness is calculated for the two principal axes y-y and z-z only. The LVV parameter is not used. For double angles, the LVV parameter is available to comply with note 5 in table 25. In addition, if using double angles from user tables, (Technical Reference Manual section 5.19) an eleventh value, r vv, should be supplied at the end of the ten existing values corresponding to the radius of gyration of the single angle making up the pair. 6. (SWAY – Sway Loadcase) This parameter is used to specify a load case that is to be treated as a sway load case in the context of clause 4.8.3.3.4. This load case would be set up to represent the “k amp M s ” mentioned in this clause and the steel design module would add the forces from this load case to the forces of the other load case it is designed for. Note that the load case specified with this parameter will not be designed as a separate load case. The following is the correct syntax for the parameter:-

SWAY

(load case number)

e.g. SWAY 5 MEM 1 to 10 SWAY 6 _MainBeams

ALL MEMBER (member list) _(group name)

2-41


2-42

Section 2B

Table 2B.1 - British Steel Design – BS5950:2000 - Parameters Parameter Name

Default Value

Description

CODE

BS5950

Design Code to follow. See section 5.47.1 of the Technical Reference Manual.

SGR

AD PY *

0.0

Depth at end/2 Set according to steel grade (SGR)

Steel Grade per BS4360 0.0 = Grade S 275 1.0 = Grade S 355 2.0 = Grade S 460 3.0 = As per GB 1591 – 16 Mn Distance between the reference axis and the axis of restraint. See G.2.3 Design strength of steel

KY

1.0

K factor value in local y - axis. Usually, this is the minor axis.

KZ

1.0

K factor value in local z - axis. Usually, this is the major axis.

LY *

Member Length

Length in local y - axis (current units) to calculate (KY)(LY)/Ryy slenderness ratio.

LZ *

Member Length

Length in local z - axis (current units) to calculate (KZ)(LZ)/Rzz slenderness ratio.

UNF

1.0

UNL *

Member Length

Factor applied to unsupported length for Lateral Torsional Buckling effective length per section 4.3.6.7 of BS5950. Unsupported Length for calculating Lateral Torsional Buckling resistance moment section 4.3.6.7 of BS5950.

NSF

1.0


SBLT

0.0

Identify Section type for section classification 0.0 = Rolled Section 1.0 = Built up Section 2.0 = Cold formed section

MAIN

0.0

Slenderness limit for members with compression forces, effective length/ radius of gyration, for a given axis:0.0 = Slenderness not performed. 1.0 = Main structural member (180) 2.0 = Secondary member. (250) 3.0 = Bracing etc (350)

Section 2B

2-43

Table 2B.1 - British Steel Design – BS5950:2000 - Parameters Parameter Name TRACK

Default Value 0.0

Description 0.0 = 1.0 = 2.0 = 4.0 =

Suppress all member capacity info. Print all member capacities. Print detailed design sheet. Deflection Check (separate check to main select / check code)

BEAM

3.0

0.0 = Design only for end moments or those locations specified by the SECTION command. 1.0 = Calculate forces and moments at 12th points along the member. Establish the location where Mz is the maximum. Use the forces and moments at that location. Clause checks at one location. 2.0 = Same as BEAM = 1.0 but additional checks are carried out for each end. 3.0 = Calculate moments at 12th points along the member. Clause checks at each location including the ends of the member.

LEG

0.0

Valid range from 0 – 7 and 10. See section 2B.6.5 for details. The values correspond to table 25 of BS5950 for fastener conditions.

LVV *

Maximum of Lyy and Lzz (Lyy is a term used by BS5950)

Used in conjunction with LEG for Lvv as per BS5950 table 25 for double angles, note 5.

CB

1.0

DFF

None (Mandatory for deflection check, TRACK 4.0)

DJ1


Joint No. denoting starting point for calculation of "Deflection Length" (See Note 1)

DJ2

End Joint of member

Joint No. denoting end point for calculation of "Deflection Length" (See Note 1)

1.0 = BS5950 per clause B.2.5 (continuous) to calculate Mb. 2.0 = To calculate Mbs (simple) as per Clause 4.7.7 as opposed to Mb. "Deflection Length" / Maxm. allowable local deflection


2-44

Section 2B

Table 2B.1 - British Steel Design – BS5950:2000 - Parameters Parameter Name CAN

Default Value 0

ESTIFF

0.0

WELD

1.0 closed 2.0 open

Description 0 = deflection check based on the principle that maximum deflection occurs within the span between DJ1 and DJ2. 1 = deflection check based on the principle that maximum deflection is of the cantilever type (see note below) Clauses 4.8.3.3.1 and 4.8.3.3.2 0.0 = Fail ratio uses MIN of 4.8.3.3.1, 4.8.3.3.2. and Annex I1 checks. 1.0 = Fail ratio uses MAX of 4.8.3.3.1, 4.8.3.3.2. and Annex I1 checks. Weld Type, see AISC steel design 1.0 = Closed sections. Welding on one side only (except for webs of wide flange and tee sections) 2.0 = Open sections. Welding on both sides (except pipes and tubes)

TB

0.0

0.0 = Elastic stress analysis 1.0 = Plastic stress analysis

PNL *

0.0

SAME**

0.0

Transverse stiffener spacing („a‟ in Annex H1) 0.0 = Infinity Any other value used in the calculations. Controls the sections to try during a SELECT process. 0.0 = Try every section of the same type as original 1.0 = Try only those sections with a similar name as original, e.g. if the original is an HEA 100, then only HEA sections will be selected, even if there are HEM‟s in the same table.

MX

1.0

Equivalent moment factor for major axis flexural buckling as defined in clause 4.8.3.3.4

MY

1.0

Equivalent moment factor for minor axis flexural buckling as defined in clause 4.8.3.3.4

MYX

1.0

Equivalent moment factor for minor axis lateral flexural buckling as defined in clause 4.8.3.3.4

MLT

1.0

Equivalent moment factor for lateral torsional buckling as defined in clause 4.8.3.3.4

SWAY

none

Specifies a load case number to provide the sway loading forces in clause 4.8.3.3.4 (See additional notes)

DMAX *

100.0cm

Maximum allowable depth

Section 2B

Table 2B.1 British Steel Design – BS5950:2000 Parameters Parameter Name

Default Value

DMIN *

0.0cm

RATIO

1.0

Description Minimum allowable depth Permissible ratio of the actual capacities.

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. * current units must be considered. **For angles, if the original section is an equal angle, then the selected section will be an equal angle and vice versa for unequal angles. (note there was an NT parameter in STAAD.Pro 2005 build 1003 which is now automatically calculated during the design as it is load case dependant)

NOTES: 1) When performing the deflection check, the user can choose between two methods. The first method, defined by a value 0 for the CAN parameter, is based on the local displacement. Local displacement is described in section 5.43 of this manual. If the CAN parameter is set to 1, the check will be based on cantilever style deflection. Let (DX1, DY1, DZ1) represent the nodal displacements (in global axes) at the node defined by DJ1 (or in the absence of DJ1, the start node of the member). Similarly, (DX2, DY2, DZ2) represent the deflection values at DJ2 or the end node of the member. Compute Delta = SQRT((DX2-DX1)**2 + (DY2-DY1)**2 + (DZ2-DZ1)**2) Compute Length = distance between DJ1 & DJ2 or, between start node and end node, as the case may be. Then, if CAN is specified a value 1, dff = L/Delta Ratio due to deflection = DFF/dff

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2-46

Section 2B

2) If CAN = 0, deflection length is defined as the length that is used for calculation of local deflections within a member. It may be noted that for most cases the “Deflection Length” will be equal to the length of the member. However, in some situations, the “Deflection Length” may be different. For example, refer to the figure below where a beam has been modeled using four joints and three members. The “Deflection Length” for a ll three members will be equal to the total length of the beam in this case. The parameters DJ1 and DJ2 should be used to model this situation. Also the straight line joining DJ1 and DJ2 is used as the reference line from which local deflections are measur ed. Thus, for all three members here, DJ1 should be "1" and DJ2 should be "4".

3) If DJ1 and DJ2 are not used, "Deflection Length" will default to the member length and local deflections will be measured from original member line. 4) It is important to note that unless a DFF value is specified, STAAD will not perform a deflection check. This is in accordance with the fact that there is no default value for DFF (see Table 2.1). 5) The above parameters may be used in conjunction with other available parameters for steel design.

2B.7 Design Operations STAAD contains a broad set of facilities for the design of structural members as individual components of an analysed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem.

Section 2B

The operations to perform a design are:   

Specify the load cases to be considered in the design; the default is all load cases. Specify design parameter values, if different from the default values. Specify whether to perform code checking or member selection along with the list of members.

These operations may be repeated by the user any number of times depending upon the design requirements.

2B.8 Code Checking The purpose of code checking is to ascertain whether the provided section properties of the members are adequate. The adequacy is checked as per BS5950. Code checking is done using the forces and moments at specific sections of the members. If no sections are specified, the program uses the start and end forces for code checking. When code checking is selected, the program calculates and prints whether the members have passed or failed the checks; the critical condition of BS5950 code (like any of the BS5950 specifications for compression, tension, shear, etc.); the value of the ratio of the critical condition (overstressed for value more than 1.0 or any other specified RATIO value); the governing load case, and the location (distance from the start of the member of forces in the member where the critical condition occurs). Code checking can be done with any type of steel section listed in Section 2B.4 of the STAAD Technical Reference Manual or any of the user defined sections in section 5.19 with two exceptions; GENERAL and ISECTION. In BS5950, these will not be considered for design along with PRISMATIC sections, which are also not acceptable.

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2-48

Section 2B

2B.9 Member Selection STAAD is capable of performing design operation s on specified members. Once an analysis has been performed, the program can select the most economical section, i.e. the lightest section, which fulfills the code requirements for the specified member. The section selected will be of the same type section as originally designated for the member being designed. Member selection can also be constrained by the parameters DMAX and DMIN, which limits the maximum and minimum depth of the members. Member selection can be performed with all the types of steel sections with the same limitations as defined in section 2B.8 CODE CHECKING. Selection of members, whose properties are originally input from a user created table, will be limited to sections in the user table. Member selection cannot be performed on members whose section properties are input as prismatic or as above limitations for code checking.

Section 2B

2B.10 Tabulated Results of Steel Design For code checking or member selection, the program produces the results in a tabulated fashion. The items in the ou tput table are explained as follows: a) MEMBER

refers to the member number for which the design is performed.

b) TABLE

refers to steel section name, which has been checked against the steel code or has been selected. prints whether the member has PASSED or FAILED. If the RESULT is FAIL, there will be an asterisk (*) mark on front of the member.

c) RESULTS

d) CRITICAL COND refers to the section of the BS5950 code which governs the design. e) RATIO

prints the ratio of the actual stresses to allowable stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed.

f) LOADING

provides the load case number, which governed the design.

g) FX, MY, and MZ provide the axial force, moment in local Yaxis and the moment in local z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX, MY and MZ are printed since they are the ones which are of interest, in most cases.

2-49


2-50

Section 2B

h) LOCATION

specifies the actual distan ce from the start of the member to the section where design forces govern.

i) TRACK

If the parameter TRACK is set to 1.0, the program will block out part of the table and will print the allowable bending capacities in compression (MCY & MCZ) and reduced moment capacities (MRY & MRZ), allowable axial capacity in compression (PC) and tension (PT) and shear capacity (PV). TRACK 2.0 will produce the design results as shown in section 2B.9.

2B.11 Plate Girders Sections will be considered for the Plate Girder checks (BS 5950 Section 4.4) if d/t > 70  for „rolled sections‟ or d/t >62  for „welded sections‟. The parameter SBLT should be used to identify sections as rolled or welded; see the parameter list for more information. If the plate girder has intermediate stiffeners, the spacing is set with the PNL parameter. These are then used to check against the code clauses „4.4.3.2 - Minimum web thickness for serviceability‟ and „4.4.3.3 - Minimum web thickness to avoid compression flange buckling‟. The following printout is then included if a TRACK 2.0 output is selected:Shear Buckling check is required: Vb = 1070 kN : qw d

= 900 mm

:

t

=

BS-4.4.3.2 status = PASS

10 mm

: a

=

= 118 N/mm2

200 mm : pyf = 275 N/mm2

: BS -4.4.3.3 status = PASS

The section is then checked for shear buckling resistance using clause „4.4.5.2 - Simplified method‟ and the result is included in the ratio checks.

Section 2B

2B.12 Composite Sections Sections that have been defined as acting compositely with a concrete flange either from a standard database section using the CM option, or from a modified user WIDE FLANGE database with the additional composite parameters, cannot be designed with BS5950:2000.

2B.13 Design of Tapered Beams Design Procedure Sections will be checked as tapered members provided that are defined either as a Tapered I section, e.g.

UNIT CM MEMBER PROPERTY 1 TO 5 TAPERED 100 2.5 75 25 4 25 4 or from a USER table, e.g. START USER TABLE TABLE 1 UNIT CM ISECTION 1000mm_TAPER 100 2.5 75 25 4 25 4 0 0 0 750mm_TAPER 75 2.5 50 25 4 25 4 0 0 0 END

2-51


2-52

Section 2B

The user must specify the effective length of unrestrained compression flange using the parameter UNL. The program compares the resistance of members with the applied load effects, in accordance with BS 5950-1:2000. Code checking is carried out for locations specified by the user via the SECTION command or the BEAM parameter. The results are presented in a form of a PASS/FAIL identifier and a RATIO of load effect to resistance for each member checked. The user ma y choose the degree of detail in the output data by setting the TRACK parameter. The beam is designed is designed as other wide flange beams apart from the Lateral Torsional Buckling check which is replaced by the Annex G.2.2. check. Design Equations A beam defined with tapered properties as defined above will be checked as a regular wide flange (e.g. UB or UC), except that the following is used in place of clause 4.3.6, the lateral torsional buckling check. Check Moment for Taper Members as per clause G.2.2 The following criterion is checked at each defined check position in the length of the member defined by the BEAM parameter.

M xi  M bi (1  Fc / Pc ) Where

Fc M bi

M xi

is the longitudinal compression at the check location ; is the buckling resistance moment M b from 4.3.6 for an equivalent slenderness  TB , see G.2.4.2, based on the appropriate modulus S, S eff, Z or Z e ff of the cross-section at the point i considered; is the moment about the major axis acting at the point i considered;

Section 2B

Pc

is the compression resistance from 4.7.4 for a slenderness  TC , see G.2.3, based on the properties of the minimum depth of cross-section within the segment length L y .

G.2.3 Slenderness TC

TC = y In which:

  1  ( 2 a / hs ) 2 y 2 2  1  (2a / hs )  0.05( / x) 

0.5

 = Ly/ry Where a is the distance between the reference axis and the axis of restraint, hs is the distance between the shear centers of the flanges; Ly is the length of the segment; ry is the radius of gyration for buckling about the minor axis; x torsional index G.2.4.2 Equivalent slenderness TB for Taper members

TB = cntt In which for a two-flange haunch:

  4 a / hs t   2 2  1  (2a / hs )  0.05( / x) 

0.5

Where C is the taper factor, see G.2.5;

2-53


2-54

Section 2B

G.2.5 Taper factor

For an I-section with D ≥ 1.2B and x ≥ 20 the taper factor c should be obtained as follows:

 3  Dmax  c=1+  1 x  9  Dmin  D max D min x

2/3

is the maximum depth of cross -section within the length Ly, see Figure G.3; is the minimum depth of cross-section within the length Ly, see Figure G.3; is the torsional index of the minimum depth cross section, see 4.3.6.8

Otherwise c is taken as 1.0

2-55

Steel Design Per BS5950:1990 Section

2B1

2B1.1 General This code has been withdrawn by the British Stand ards, but has been retained in STAAD.Pro for comparative purposes only. The design philosophy embodied in BS5950 is built around the concept of limit state design, used today in most modern steel design codes. Structures are designed and proportioned taking into consideration the limit states at which they become unfit for their intended use. Two major categories of limit state are recognized serviceability and ultimate. The primary considerations in ultimate limit state design are strength and stability while that in serviceability limit state is deflection. Appropriate safety factors are used so that the chances of limits being surpassed are acceptably remote. In the STAAD implementation of BS5950, members are proportioned to resist the design loads without exceeding the limit states of strength and stability. Accordingly, the most economic section is selected on the basis of the least weight criteria. This procedure is controlled by the designer in specification of allowable member depths, desired section type or other such parameters. The code checking portion of the program checks that code requirements for each selected section are met and identifies the governing criteria. The complete B.S.C. steel tables for both hot rolled and hollow sections are built into the program for use in specifying member properties as well as for the actual design process. See section 2B.4 for information regarding the referencing of these sections. In addition to universal beams, columns, joists, piles, channels,


2-56

Section 2B1

tees, composite sections, beams with cover plates, pipes, tubes and angles, there is a provision for user provided tables.

2B1.2 Analysis Methodology Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis or P-Delta analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.

2B1.3 Member Property Specifications For specification of member properties, the steel section li brary available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built -in steel table. Members properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

2B1.4 Built-In Steel Section Library The following information is provided for use when the built -in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members. Almost all BSI steel sections are available for input. A complete listing of the sections available in the built -in steel section library may be obtained by using the tools of the graphical user interface.

Section 2B1

2-57

Following are the descriptions of different types of sections available: Universal Beams, Columns And Piles All rolled universal beams, columns and pile sections are available. The following examples illustrate the designation scheme.

20 TO 30 TA ST UB305X165X54 33 36 TA ST UC356X406X287 100 102 106 TA ST UP305X305X186 Rolled Steel Joists Joist sections may be specified as they are listed in BSI -80 with the weight omitted. In those cases where two joists have the same specifications but different weights, the lighter section should be specified with an "A" at the end.

10 TO 20 TA ST JO152X127 1 2 TA ST JO127X114A Channel Sections All rolled steel channel sections from the BSI table have been incorporated in STAAD. The designation is similar to that of the joists. The same designation scheme as in BSI tables may be used with the weight omitted.

10 TO 15 TA ST CH305X102 55 57 59 61 TA ST CH178X76 Double Channels Back to back double channels, with or without spacing between them, are available. The letter "D" in front of the section name will specify a double channel, e.g. D CH102X51, D CH203X89 etc.


2-58

Section 2B1

51 52 53 TA D CH152X89 70 TO 80 TA D CH305X102 SP 5. (specifies a double channel with a spacing of 5 length units) Tee Sections Tee sections are not input by their actual designations, but instead by referring to the universal beam shapes from which they are cut. For example,

54 55 56 TA T UB254X102X22 UB254X102X22)

(tee cut from

Angles All equal and unequal angles are available for input. Two types of specifications may be used to describe an angle. The standard angle section is specified as follows:

15 20 25 TA ST UA200X150X18 This specification may be used when the local STAAD z -axis corresponds to the V-V axis specified in the steel tables. If the local STAAD y-axis corresponds to the V-V axis in the tables, type specification "RA" (reverse angle) may be used.

35 TO 45 TA RA UA200X150X18 Double Angles Short leg back to back or long leg back to back double angles can be specified by inputting the word SD or LD, respectively, in front of the angle size. In case of an equal angle, either LD or SD will serve the purpose. For example,

Section 2B1

14 TO 20 TA LD UA200X200X16 SP 1.5 23 27 TA SD UA80X60X6 "SP" denotes spacing between the individual angle sections. Pipes (Circular Hollow Sections) To designate circular hollow sections from BSI tables, use PIP followed by the numerical value of diameter and thickness of the section in mm omitting the decimal section of the value provided for diameter. The following example will illustrate the designation.

10 15 TA ST PIP213.2 (specifies a 21.3 mm dia. pipe with 3.2 mm wall thickness) Circular hollow sections may also be provided by specifying the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0 (specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units) Only code checking and no member selection will be performed if this type of specification is used. Tubes (Rectangular or Square Hollow Sections) Designation of tubes from the BSI steel table is illustrated below: TUB 400 200 12.5 Tube symbol Height (mm)

Thickness (mm) Width (mm)

2-59


2-60

Section 2B1

Example:

15 TO 25 TA ST TUB160808.0

Tubes, like pipes, can also be input by their dimensions (Height, Width and Thickness) and not by any table designations.

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height of 8, a width of 6, and a wall thickness of 0.5 length units. Note that only code checking and no member selection is performed for TUBE sections specified this way.

2B1.5 Member Capacities The basic measure of capacity of a beam is taken as the plastic moment of the section. This is a significant departure from the standard practice followed in BS449, in which the limiting condition was attainment of yield stress at the extreme fibres of a given section. With the introduction of the plastic moment as the basic measure of capacity, careful consideration must be given to the influence of local buckling on moment capacity. To assist this, sections are classified as either plastic, compact, semi-compact or slender, which governs the decision whether to use the plastic or the elastic moment capacity. The section classification is a function of the geometric properties of the section. STAAD is capable of determining the section classification for both hot rolled and built up sections. In addition, for slender sections, BS5950 recommends the use of a 'stress reduction factor' to reduce the design strength. This factor is again a function of the geometry of the section and is automatically determined by STAAD for use in the design process. Axial Tension In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of the effective area as outlined

Section 2B1

in Section 4.6 of the code. STAAD calculates the tension capacity of a given member per this procedure, based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value - see Table 2B.1 ), proceeding with member selection or code check accordingly. BS5950 does not have any slenderness limitations for tension members. Compression Compression members must be designed so that the compression resistance of the member is greater than the axial compressive load. Compression resistance is determined according to the compressive strength which is a function of the slenderness of the gross section, the appropriate design strength and the relevant strut characteristics. Strut characteristics take into account the considerable influence residual rolling and welding stresses have on column behaviour. Based on data collected from extensive research, it has been determined that sections such as tubes with low residual stresses and Universal Beams and Columns are of intermediate performance. It has been found that I -shaped sections are less sensitive to imperfections when constrained to fail about an axis parallel to the flanges. These research observations are incorporated in BS5950 through the use of four strut curves together with a selection of tables to indicate which curve to use for a particular case. Compression strength for a particular section is calculated in STAAD according to the procedure outlined in Appendix C of BS5950 where compression strength is seen to be a function of the appropriate Robertson constant (representing Strut Curve) corresponding Perry factor, limiting slenderness of the member and appropriate design strength. In addition to the compression resistance criteria, compression members are required to satisfy slenderness limitations which are a function of the nature of the use of the member (main load resisting component, bracing member etc). In both the member selection and the code checking process, STAAD immediately does a slenderness check on appropriate members before continuing with the other procedures for determining the adequacy of a given member.

2-61


2-62

Section 2B1

Axially Loaded Members With Moments In the case of axially loaded members with moments, the moment capacity of the member must be calculated about both axes and all axial forces must be taken into account. If the section is plastic or compact, plastic moment capacities will constitute the basic moment capacities subject to an elastic limitation. The purpose of this elastic limitation is to prevent plasticity at working load. For semi-compact or slender sections, the elastic moment is used. For plastic or compact sections with high shear loads, the plastic modulus has to be reduced to accommodate the shear loads. The STAAD implementation of BS5950 incorporates the procedure outlined in section 4.2.5 and 4.2.6 to calculate the appropriate moment capacities of the section. For members with axial tension and moment, the interaction formula as outlined in section 4.8.2 is applied based on effective tension capacity. For members with axial compression and moment , two principal interaction formulae must be satisfied - local capacity check (4.8.3.2) and overall buckling check (section 4.8.3.3). Two types of approach for the overall buckling check have been outlined in BS5950 - the simplified approach and the more exact approach. As noted in the code, in cases where neither the major axis nor the minor axis moment approaches zero, the more exact approach may be more conservative than the simplified approach. It has been found, however, that this is not always the case and STAAD therefore performs both checks, comparing the results in order that the more appropriate criteria be used. Members subject to biaxial moments in the absence of both tensile and compressive axial forces are checked using the appropriate method d escribed above with all axial forces set to zero. STAAD also carries out cross checks for compression only, which for compact/plastic sections may be more critical. If this is the case, COMPRESSION will be the critical condition reported despite the presen ce of moments.

Section 2B1

Shear Load A member subjected to shear is considered adequate if the shear capacity of the section is greater than the shear load on the member. Shear capacity is calculated in STAAD using the procedure outlined in section 4.2.3 and considering the appropriate shear area for the section specified. Lateral Torsional Buckling Since plastic moment capacity is the basic moment capacity used in BS5950, members are likely to experience relatively large deflections. This effect, coupled with la teral torsional buckling, may result in severe serviceability limit state. Hence, lateral torsional buckling must be considered carefully. The procedure to check for lateral torsional buckling as outlined in section 4.3 has been incorporated in the STAAD implementation of BS5950. According to this procedure, for a member subjected to moments about the major axis, the 'equivalent uniform moment' on the section must be less than the lateral torsional buckling resistance moment. For calculation of the bucklin g resistance moment, the procedure outlined in Appendix B.2 has been implemented for all sections with the exception of angles. In Appendix B.2., the resistance moment is given as a function of the elastic critical moment, Perry coefficient, and limiting equivalent slenderness, which are calculated within the program; and the equivalent moment factor, m, and slenderness correction factor, n, which are determined as a function of the loading configuration and the nature of the load ( stabilizing, destabilizing, etc ). The user is allowed to control these values through the parameters CMM & CMN. If CMM is set to -1, the program automatically calculates the coefficient 'm'. Similarly parameter CMN may be used for the calculation of coefficient 'n'. BS5950 recommends the use of tables 15 & 16 for the calculation of coefficient 'n'. The parameter CMN may be set to -1 or -2 to instruct the program to obtain coefficient 'n' from table 15 or 16 respectively. If a positive value is provided for either CMN or CMM, the program will use this value directly in calculations. The default value for each of

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2-64

Section 2B1

these parameters is 1.0 as shown in table 2B.1 of this document. It may be noted that BS5950 recommends the use of either 'm' or 'n' in lateral torsional buckling calculations. If both 'm' and 'n' are set to values less than 1 in error, the program will always reset CMN to 1 and over-ride the provided value. The following table illustrates the use of parameters 'm' and 'n'. PARAMETER CMM

CMN

VALUE ANY POSITIVE VALUE -1 -2 ANY POSITIVE VALUE -1 -2

STAAD ACTION Direct use of this value in calculations. Program calculates 'm' per BS5950 Calculate „m‟ for both axes Direct use of this value in calculations. Program calculates 'n' per BS5950 - Table 15 Program calculates 'n' per BS5950 - Table 16

IMPORTANT NOTE: Note that if negative value options are chosen, lateral restraints should be modelled by nodes and the section command incorporated to find Mo. Failure to use the SECTION 0.5 command will cause the program to reset CMN to 1.0 and over ride any value that may have been provided. In requesting 'n' to be calculated by the program by using a negative CMN value, the member properties must be British ( or British combined with user table sections). If other profiles such as European are being used then 'n' values are reset conservatively to 1.0 by the program. In the case of angles, section 4.3.8 of the code is followed. R. H. S Sections - Additional Provisions Rectangular Hollow sections are treated in accordance with S.C.I. recommendations in cases when the plastic axis is in the flange. In such cases, the following expressions are used to calculate the reduced plastic moduli:

Section 2B1

Srx = (A*A/4(B-t))(1-n) [ 2D(B-t)/A + n-1 ] for n>= 2t(D-2t)/A Sry = (A*A/4(D-t))(1-n) [ 2B(D-t)/A + n-1 ] for n>= 2t(B-2t)/A

2B1.6 Design Parameters Available design parameters to be used in conjunction with BS5950 are listed in table 2B.1 along with their default values. The following items should be noted with respect to their use. 1. (PY - STEEL DESIGN STRENGTH ) The design parameter PY should only be used when a uniform design strength for an entire structure or a portion thereof is required. Otherwise the value of PY will be set according to the stipulations of BS5950 table 7 in which the design strength is seen as a function of cross sectional thickness for a particular steel grade and particular element considered. Generally speaking this option is not required and the program should be allowed to ascertain the appropriate value. 2. (UNL, LY and LZ - relevant EFFECTIVE LENGTHS) The values supplied for UNL, LY and LZ should be real numbers greater than zero in current units of length. They are supplied along with or instead of UNF, KY KZ ( which are factors, not lengths) to define lateral torsional buckling and compression effective lengths respectively. Please note that both UNL or UNF and LY or KY values are required even though they are often the same values. The former relates to compression flange restraint for lateral torsional buckling while the latter is the unrestrained buckling length for compression checks. 3. (CMN and CMM - Lateral torsional buckling coefficients) As per section 2B.7 of this manual CMM and CMN should not both be used in a given design. In such a case the program will reset CMN to 1.0

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2-66

Section 2B1

4. (TRACK - control of output formats ) When the TRACK parameter is set to 1.0 or 2.0, member capacities will be printed in design related output ( code check or member selection ) in kilonewtons per square metre. An example of each follows.

TRACK 0.0 OUTPUT

STAAD CODE CHECKING - (BSI )

---------------------------

******************************


TABLE

RESULT/ FX

CRITICAL COND/ MY

RATIO/

LOADING/

MZ

LOCATION

================================================================= 1 ST UB686X254X170

PASS 86.72 C

BS-4.8.3.2 0.00

---------------------------------

0.036

3

-22.02

4.50

Section 2B1 TRACK 1.0 OUTPUT ---------------------------


ALL UNITS ARE - KNS METR (UNLESS OTHERWISE NOTED)

MEMBER

TABLE

RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ================================================================= 1 ST UB686X254X170

PASS 86.72 C

BS-4.8.3.2 0.00

0.036 -22.02

3 4.50

CALCULATED CAPACITIES FOR MEMB 1 UNIT - kN,m SECTION CLASS 4 MCZ= 1141.9 MCY= 120.4 PC= 3451.5 PT= 5739.9 MB= 1084.1 PV= 1597.5 BUCKLING CO-EFFICIENTS m AND n :

m = 1.000

n = 1.000

PZ= 5739.90

MRZ= 1141.9

MRY= 120.4

FX/PZ = 0.02

TRACK 2.0 OUTPUT ---------------------------



TABLE

RESULT/ FX

CRITICAL COND/ MY

RATIO/ MZ

LOADING/ LOCATION

================================================================= 1 ST UB686X254X170

PASS BS-4.8.3.2 0.036 3 86.72 C 0.00 -22.02 4.50 ================================================================= MATERIAL DATA Grade of steel Modulus of elasticity Design Strength (py)

= 43 = 205 kN/mm2 = 265 N/mm2

SECTION PROPERTIES (units - cm) Member Length Gross Area Net Area

= 450.00 = 216.60 = 216.60

Moment of inertia Plastic modulus Elastic modulus Shear Area Radius of gyration Effective Length

z-axis : 170147.000 : 5624.000 : 4911.156 : 109.122 : 28.027 : 450.000

Reduced = 232N/mm2

y-axis 6621.000 810.000 517.670 100.470 5.529 450.000

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2-68

Section 2B1 DESIGN DATA (units - kN,m) BS5950/1990 Section Class : SLENDER Squash Load : 5739.90 Axial force/Squash load : 0.015 Slenderness ratio (KL/r) Compression Capacity Tension Capacity Moment Capacity Reduced Moment Capacity Shear Capacity

BUCKLING CALCULATIONS Lateral Torsional Buckling Moment co-efficients m & n : m =1.00

: : : : : :

z-axis 16.1 5036.2 5739.9 1141.9 1141.9 1561.5

y-axis 81.4 3451.5 5739.9 120.4 120.4 1597.5

(units - kN,m) (MB = 1084.1) n =1.00, Effective Length =4.500

CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m): CLAUSE BS-4.7 (C) BS-4.8.3.2 BS-4.8.3.3.1 BS-4.8.3.3.2 BS-4.2.3-(Y) BS-4.3 (LTB)

RATIO 0.025 0.036 0.047 0.026 0.005 0.020

LOAD 3 3 1 1 1 4

FX 86.7 86.7 83.3 83.3 83.3 -86.7

VY 3.2 3.2 7.4 7.4 7.4 3.2

VZ 0.0 0.0 0.0 0.0 0.0 0.0

MZ -22.0 -22.0 -27.6 -27.6 -27.6 22.0

MY 0.0 0.0 0.0 0.0 0.0 0.0

Torsion and deflections have not been considered in the design 5. ( LEG - table 24/28 BS5950 for fastner control ) The LEG parameter follows the requirements of BS5950 table 28. This table concerns the fastner restraint conditions for angles, double angles, tee sections and channels for slenderness. The following values are available: Clause 4.7.10.2

(a) Single Angle, short leg (b) Single Angle, short leg (a) Single Angle, long leg (b) Single Angle, long leg

1.0 0.0 3.0 2.0

Section 2B1

Clause 4.7.10.3

Clause 4.7.10.4 Clause 4.7.10.5

(a) Double angle, short leg 3.0 (b) Double angle, short leg 2.0 (c) Double angle, long leg 1.0 (d) Double angle, long leg 0.0 (a) Double angle, long leg 7.0 (b) Double angle, long leg 6.0 (c) Double angle, short leg 5.0 (d) Double angle, short leg 4.0 (a) Channels, 2 or more rows 1.0 (b) Channels, 1 row 0.0 (a) Tee sections, 2 or more rows 1.0 (b) Tee sections, 1 row 0.0

When defining member properties for single angles, the spec (manual ref: 5.20.1) should be provided as RA and not ST. See fig 1.6 of the Technical Reference Manual. Table 28 may be by-passed in favour of table 24 by using: 10 = Table 24 for equal angles or long legs of unequal angles 11 = Table 24 for short legs of unequal angles For single angles, LY and KY parameters should be provided relative to the raa axis while LZ and KZ are related to rbb. Lvv will be considered as the minimum of the KY*LY and KZ*LZ values. For double angles, the LVV parameter is available to comply with note 5 table 28. In addition, if using double angles from user tables, (Technical Reference Manual section 5.19) an eleventh value, rvv, should be supplied at the end of the ten existing values corresponding to the radius of gyration of the single angle making up the pair.

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2-70

Section 2B1

Table 2B1.1 - British Steel Design – BS5950:1990 - Parameters Parameter Name

Default Value

Description

KY

1.0

K factor value in local y - axis. Usually, this is the minor axis.

KZ

1.0

K factor value in local z - axis. Usually, this is the major axis.

LY *

Member Length

Length in local y - axis (current units) to calculate (KY)(LY)/Ryy slenderness ratio.

LZ *

Member Length

Length in local z - axis (current units) to calculate (KZ)(LZ)/Rzz slenderness ratio.

UNF

1.0

UNL *

Member Length

Factor applied to unsupported length for Lateral Torsional Buckling effective length per section 4.3.7.5 of BS5950. Unsupported Length for calculating Lateral Torsional Buckling resistance moment section 4.3.7.5 of BS5950.

PY *

Set according to steel grade (SGR)

Design Strength of steel

NSF

1.0


SGR

0.0

Steel Grade per BS4360 0.0 = Grade 43 1.0 = Grade 50 2.0 = Grade 55 3.0 = As per GB 1591 – 16 Mn

SBLT

0.0

0.0 = Rolled Section 1.0 = Built up Section

MAIN

1.0

As per BS5950 4.7.3 1.0 = Main structural member (180) 2.0 = Secondary member. (250) 3.0 = Bracing etc (350)

CMM !

1.0

Coefficient m for lateral torsional buckling. (see section 2B.5)

CMN !

1.0

Coefficient n for lateral torsional buckling. (see section 2B.5)

TRACK

0.0

0.0 = Suppress all member capacity info. 1.0 = Print all member capacities. 2.0 = Print detailed design sheet. 4.0 = Deflection Check (separate check to main select / check code)

Section 2B1

2-71

Table 2B1.1 - British Steel Design – BS5950:1990 - Parameters Parameter Name DMAX *

Default Value

Description

100.0cm


DMIN *

0.0cm

Minimum allowable depth

RATIO

1.0

Permissible ratio of the actual capacities.

BEAM

0.0

0.0 = Design only for end moments or those locations specified by the SECTION command. 1.0 = Calculate moments at 12th points along the member and use the maximum Mz value for design. Clause checks at one location 2.0 = Same as BEAM = 1.0 but additional checks are carried out for each end. 3.0 = Calculate moments at 12th points along the member. Clause checks at each location including the ends of the member.

CODE

BS5950

LEG

0.0

LVV *


Design Code to follow. See section 5.47.1 of the Technical Reference Manual. Values range from 0 - 12. See section 2B.6.5 for details. The values correspond to table 24/28 of BS5950 for fastner conditions. Used in conjunction with LEG for Lvv as per BS5950 table 28 for double angles, note 5.

CB

1.0

DFF


DJ1



DJ2

End Joint of member


ESTIFF

0.0

1.0 = BS5950 per clause B.2.5 (continuous) to calculate Mb. 2.0 = To calculate Mbs (simple) as per Clause 4.7.7 as opposed to Mb. "Deflection Length" / Maxm. allowable local deflection

Clauses 4.8.3.3.1 and 4.8.3.3.2 1.0 = Pass if member passes EITHER clause. 1.0 = Pass if member passes BOTH clauses.


2-72

Section 2B1

Table 2B1.1 - British Steel Design – BS5950:1990 - Parameters Parameter Name WELD

Default Value 1.0 closed 2.0 open

Description Weld Type, see AISC steel design 1.0 = Welding on one side only (except for webs of wide flange and tee sections) 2.0 = Welding on both sides (except pipes and tubes)

TB

0.0

2.0 = Elastic stress analysis 3.0 = Plastic stress analysis

PNL *

0.0

SAME **

0.0

Transverse stiffener spacing („a‟ in Appendix H1) 0.0 = Infinity Any other value used in the calculations. Controls the sections to try during a SELECT process. 0.0 = Try every section of the same type as original 1.0 = Try only those sections with a similar name as original, e.g. if the original is an HEA 100, then only HEA sections will be selected, even if there are HEM‟s in the same table.

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. ! CMN & CMM cannot both be provided. * current units must be considered. **For angles, if the original section is an equal angle, then the selected section will be an equal angle and vice versa for unequal angles.

NOTES: 1) "Deflection Length" is defin ed as the length that is used for calculation of local deflections within a member. It may be noted that for most cases the "Deflection Length" will be equal to the length of the member. However, in some situations, the "Deflection Length" may be differen t. For example, refer to the figure below where a beam has been modeled using four joints and three members. Note that the "Deflection Length" for all three members will be equal to the total length of the beam in this case. The parameters DJ1 and DJ2 shou ld be used to model this situation. Also the straight line joining DJ1 and DJ2 is used as the reference line from which local deflections

Section 2B1

are measured. Thus, for all three members here, DJ1 should be "1" and DJ2 should be "4". 1

2 1

3 2

EXAMPLE :

4 3 D

D = Maximum local deflection for members 1, 2 and 3.

PARAMETERS DFF 300. ALL DJ1 1 ALL DJ2 4 ALL

2) If DJ1 and DJ2 are not used, "Deflection Length" will default to the member length and local deflections will be measured from original member line. 3) The above parameters may be used in conjunction with other available parameters for steel design.

2B1.7 Design Operations STAAD contains a broad set of facilities for the design of structural members as individual components of an analysed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are:   

Specify the load cases to be considered in the design. Specify design parameter values, if different from the default values. Specify whether to perform code checking or member selection along with the list of members.

These operations may be repeated by the user any number of times depending upon the design requirements.

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2-74

Section 2B1

2B1.8 Code Checking The purpose of code checking is to ascertain whether the provided section properties of the members are adequate. The adequacy is checked as per BS5950. Code checking is done using the forces and moments at specific sections of the members. If no sections are specified, the program uses the start and end forces for code checking. When code checking is selected, the program calculates and prints whether the members have passed or failed the checks; the critical condition of BS5950 code (like any of the BS5950 specifications for compression, tension , shear, etc.); the value of the ratio of the critical condition (overstressed for value more than 1.0 or any other specified RATIO value); the governing l oad case, and the location (distance from the start of the member of forces in the member where the critical condition occurs). Code checking can be done with any type of steel section listed in Section 2B.4 of the STAAD Technical Reference Manual or any of the user defined sections in section 5.19 with two exceptions ; GENERAL and ISECTION. In BS5950, these will not be considered for design along with PRISMATIC sections which are also not acceptable.

2B1.9 Member Selection STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, i.e. the lightest section, which fulfills the code requirements for the specified member. The section selected will be of th e same type section as originally designated for the member being designed. Member selection can also be constrained by the parameters DMAX and DMIN which limits the maximum and minimum depth of the members.

Section 2B1

Member selection can be performed with all the types of steel sections with the same limitations as defined in section 2B.8 CODE CHECKING. Selection of members, whose properties are originally input from a user created table, will be limited to sections in the user table. Member selection can not be performed on members whose section properties are input as prismatic or as above limitations for code checking.

2B1.10 Tabulated Results of Steel Design For code checking or member selection, the program produces the results in a tabulated fashion. The items in the output table are explained as follows: a) MEMBER

refers to the member number for which the design is performed.

b) TABLE

refers to steel section name which has been checked against the steel code or has been selected. prints whether the member has PASSED or FAILED. If the RESULT is FAIL, there will be an asterisk (*) mark on front of the member.

c) RESULTS

d) CRITICAL COND refers to the section of the BS5950 code which governs the design. e) RATIO

prints the ratio of the actual stresses to allowable stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed.

f) LOADING

provides the load case number which governed the design.

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2-76

Section 2B1

g) FX, MY, and MZ provide the axial force, moment in local Yaxis and the moment in local z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX, MY and MZ are printed since they are the ones which are of interest, in most cases. h) LOCATION

specifies the actual distance from the start of the member to the section where design forces govern.

i) TRACK

If the parameter TRACK is set to 1.0, the program will block out part of the table and will print the allowable bending capacities in compression (MCY & MCZ) and reduced moment capacities (MRY & MRZ), allowable axial capacity in compression (PC) and tension (PT) and shear capacity (PV). TRACK 2.0 will produce the design results as shown in section 2B.9.

2B1.11 Plate Girders Plate girders may be considered for design in BS5950. The "py" used in the calculation of compressive strength is reduced by 20N/mm 2 as per the code if parameter SBLT is set to 1.0. The code requires that for d/t >63E, the interaction checks be modified in order to check for shear buckling of the web. This is considered in STAAD (versions 15.0 and over) following clause 4.4.4.2a and 4.4.4.3 of the code. The shear capacity is found from table 21 of the code and used in clause 4.4.5.3. For plate girders, clauses 4.4.2.2a and 4.4.2.3a are also considered. In order to account for these checks, the output has been modified to show these variations from the more common critical checks. An example is as follows, using TRACK 2.0, showing the bottom part of the output having been modified as follows:

Section 2B1 BS5950 Table 7: d/t > 63E Web Is Checked For Shear Buckling d/t =101.7 qcr=191.9 N/mm2 d*t=14639 mm2 (4.4.5.3)Vcr= 2809.4 kN Flange =COMPACT

Pyf=344 N/mm2 4.4.2.2 a=PASS 4.4.2.3 a=PASS

Flange Ratio 4.4.4.2 (a) =0.20

L= 1

Web Ratio =0.05

L= 1

CRITICAL LOADS FOR EACH CLAUSE CHECK (units- kN,m): CLAUSE BS-4.8.3.3.2 BS-4.2.3-(Y) BS-4.3 (LTB) BS-4.4.5.3 BS-4.4.4.2 a

RATIO LOAD FX 0.177 1 0.0 0.049 1 0.0 0.151 1 0.0 0.053 1 0.0 0.203 1 0.0

VY -150.0 150.0 -150.0 150.0 -150.0

VZ 0.0 0.0 0.0 0.0 0.0

MZ -1125.0 -1125.0 -1125.0 -1125.0 -1125.0

MY 0.0 0.0 0.0 0.0 0.0

2B1.12 Composite Sections The definition of composite sections has been provided for in the standard sections definition - section 5.20.1 of the Technical Reference Manual. This is purely for analysis and for obtaining the right section properties. It uses the American requirement of 18 times depth (CT) as the effective depth. For more control with British sections two new options are available in user provided tables. 1. WIDE FLANGE COMPOSITE: Using the standard definition of I sections in WIDE FLANGE, 4 additional values can now be provided. The first is the width of concrete to the left of centre of the steel web (b1). The second is the concrete width to the right (b2). The third is the concrete depth (d1) to be considered. The last is the modular ratio. The above values are accepted in the program by adding a '-' at the first position on the first line of data. The program now awaits four extra values on line 2 as described above. If () is provided on the second line the program requires another 2 breadths + 1 thickness for the bottom plate.

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2-78

Section 2B1

2. ISECTION: The same is true for ISECTION definition in user table. 3. EXAMPLE INPUT:

UNIT CM WIDE FLANGE C45752 -66.5 44.98 .76 15.24 1.09 21345 645 21.3 34.185 33.223 150 150 30 10 ISECTION PG9144 -92.05 2.15 92.05 42.05 3.66 42.05 3.66 197.9 153.9 1730 40 40 12 1 The larger British sections have been coded as USER TABLES under wide flange and are available on request to any existing user. Please note however that composite design IS NOT available in this portion of STAAD.

2-79

Design Per BS5400

Section

2C

2C.1 General Comments BS5400 is an additional code available from Research Engineers. It does not come as standard with British versions. The British Standard, BS5400 adopts the limit state design philosophy and is applicable to steel, concrete and composite construction. The code is in 10 parts covering various aspects of bridge design. The implementation of part 3, Code of practice for design of steel bridges, in STAAD is restricted in its scope to simply supported spans. It is assumed that the depth remains constant and both construction and composite stages of steel I Sections can be checked. The following sections describe in more detail features of the design process currently available in STAAD.

2C.2 Shape Limitations The capacity of sections could be limited by local buckling if the ratio of flange outstand to thickness is large. In order to preven t this, the code sets limits to the ratio as per clause 9.3.2. In the event of exceeding these limits, the design process will terminate with reference to the clause.

Design Per BS5400

2-80

Section 2C

2C.3 Section Class Sections are further defined as compact or non -compact. In the case of compact sections, the full plastic moment capacity can be attained. In the case of non compact sections, local buckling of elements may occur prior to reaching the full moment capacity and for this reason the extreme fibre stresses are limited to first yield. In STAAD, section types are determined as per clause 9.3.7 and the checks that follow will relate to the type of section considered.

2C.4 Moment Capacity Lateral torsional buckling may occur if a member has unrestrained elements in compression. The code deals with this effect by limiting the compressive stress to a value depending on the slenderness parameter which is a modified form of the ratio Le/Ry. Le is the effective length governed by the provision of lateral restraints satisfying the requirements of clause 9.12.1. Once the allowable compressive stress is determined then the moment capacity appropriate to the section type can be calculated. STAAD takes the effective length as that provided by the user, defaulting to the length of the member during construction stage and as zero, assuming full restraint throughout, for the composite stage. The program then proceeds to calculate the allowable compressive stress based on appendix G7 from which the moment capacity is then determined.

2C.5 Shear Capacity The shear capacity, as outlined in clause is a function of the limiting shear strength, l, which is dependant on the slenderness ratio. STAAD follows the iterative procedure of appendix G8 to determine the limiting shear strength of the web pan el. The shear capacity is then calculated based on the formula given under clause 9.9.2.2.

Section 2C

2C.6 Design Parameters Available design parameters to be used in conjunction with BS5400 are listed in table 2C.1. Depending on the value assigned to the 'WET' parameter, the users can determine the stage under consideration. For a composite design check, taking into consideration the construction stage, two separate analyses are required. In the first, member properties are non-composite and the WET parameter is set to 1.0 . In the second, member properties should be changed to composite and the WET parameter set to 2.0. Member properties for composite or non composite sections should be specified from user provided tables (refer to section 5.19 of the manual for specification of user tables). Rolled sections, composite or non -composite, come under WIDE FLANGE section-type and built-up sections under ISECTION. When specifying composite properties the first parameter is assigned a negative value and four additional parameters provided giving details of the concrete section. See user table examples provided. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 2C.1 - BS5400 Design Parameters Parameter Name UNL*

Default Value Member Length

PY*

Description Unsupported Length for calculating allowable compressive bending stress. Set according to Design Strength of steel SGR

NSF

1.0


SGR*

0.0

Steel Grade per BS4360 0.0 = Grade 43 1.0 = Grade 50 2.0 = Grade 55

SBLT

0.0

0.0 = Rolled Section 1.0 = Built up Section

MAIN

1.0

1.0 = Grade of concrete 30 N/mm2

2-81

Design Per BS5400

2-82

Section 2C

Table 2C.1 - BS5400 Design Parameters Parameter Name

WET

Default Value

Description 2.0 = Grade of concrete 40 N/mm2 3.0 = Grade of concrete 50 N/mm2

0.0

0.0 = Wet stage with no data saved for composite stage. 1.0 = Wet stage with data saved for composite stage. 2.0 = Composite and wet stage combined. 3.0 = Composite stage only.

TRACK

1.0

1.0 = Print all member capacities. 0.0 = suppress all member capacities.

BEAM

0.0

MUST BE CHANGED TO 1.0 FOR ALL RUNS

LY*

Member Length

Length to calculate slenderness ratio for bending about Y-axis.

LZ*

Member Length

Length to calculate slenderness ratio for bending about Z-axis.

KY

1.0

K value for bending about Y-axis. Usually this is minor axis.

KZ

1.0

K value for bending about Z-axis. Usually this is major axis.

STIFF

1.0

Factor of length for panel length in the shear calculation.

* Provided in current unit systems.

2C.7 Composite Sections The definition of composite sections has been provided for in the standard sections definition - section 5.20.1 of the Technical Reference Manual. This is purely for analysis and for obtaining the right section properties. It uses the American requirement of 18 times depth (CT) as the effective depth. For more control with British sections two new options are available in user provided tables.

Section 2C

1. WIDE FLANGE COMPOSITE: Using the standard definition of I sections in WIDE FLANGE, 4 additional values can now be provided. The first is the width of concrete to the left of centre of the steel web (b1). The second is the concrete width to the right (b2). The third is the concrete depth (d1) to be considered. The last is the modular ratio. The above values are accepted in the progr am by adding a '-' at the first position on the first line of data. The program now awaits four extra values on line 2 as described above. If ( ) is provided on the second line the program requires another 2 breadths + 1 thickness for the bottom plate. 2. ISECTION: The same is true for ISECTION definition in user table. 3. EXAMPLE INPUT:

UNIT CM WIDE FLANGE C45752 -66.5 44.98 .76 15.24 1.09 21345 645 21.3 34.185 33.223 150 150 30 10 ISECTION PG9144 -92.05 2.15 92.05 42.05 3.66 42.05 3.66 197.9 153.9 173 0 40 40 12 1 The larger British sections have been coded as USER TABLES under wide flange and are available on request to any existing user. Please note however that composite design IS NOT available in this portion of STAAD.

2-83

Design Per BS5400

2-84

Section 2C

2-85

Design Per BS8007

Section

2D

2D.1 General Comments BS8007 is an additional code available from Research Engineers. It does not come as standard with British versions. STAAD has the capability of performing concrete slab design according to BS8007. BS8007 provides recommendations for the design of reinforced concrete structures containing aqueous liquids. It is recommended that the design of the structure is carried out according to BS8110, unless modified by the recommendations given in BS8007. Please use the following in conjunction with Section 2A of this Manual - BS8110.

2D.2 Design Process The design process is carried out in three stages. 1.

Ultimate Limit States The program is structured so that ultimate design is first carried out in accordance with recommendations given in BS8110. All active design load cases are considered in turn and a tabulated output is printed showing possible reinforcement arrangements. 12, 16 and 20 mm bars are considered with possible spacings from 100,125,150,175 and 200 mm. Within these spacings, the layout providing the closest area of steel is printed under each bar size. Longitudinal and transverse moments together with critical load

Design Per BS8007

2-86

Section 2D

cases for both hogging and sagging moments are also printed. Minimum reinforcement is in any case checked and provided in each direction. WOOD & ARMER moments may also be included in the design. 2.

Serviceability Limit States In the second stage, flexural crack widths under serviceability load cases are calculated. The FIRST and EVERY OTHER OCCURING design load case is considered as a serviceability load case and crack widths are calculated based on bar sizes and spacings proposed at the ultimate limit state check. Crack widths due to longitudinal and transverse moments are calculated directly under bars, midway between and at corners. A tabulated output indicating critical serviceability load cases and moments for top and bottom of the slab is then produced.

3.

Thermal crack widths Finally thermal, crack width calculations are carried out. Through available parameters, the user is able to provide information on the type of slab, temperature range and crack width limits. Surface zone depths are determined based on the type of slab and critical areas of reinforcements are calculat ed and printed in a tabulated form. Four bar sizes are considered and for each, max crack spacing, Smax and crack widths are calculated for the critical reinforcements and printed under each bar size. Maximum bar spacing to limit crack widths to the user's limit is also printed under each bar size.

Section 2D

2D.3 Design Parameters The program contains a number of parameters which are needed to perform and control the design to BS8007. These parameters not only act as a method to input required data for code calculations but give the Engineer control over the actual design process. Default values of commonly used values for conventional design practice have been chosen as the basis. Table 2D.1 contains a complete list of available parameters with their default values.

2D.4 Structural Model Structural slabs that are to be designed to BS8007 must be modelled using finite elements. The manual provides information on the sign convention used in the program for defining elements, (See main manual section 2-6). It is recommended to connect elements in such a way that the positive local z axis points outwards away, from the centre of the container. In this manner the "Top" of elements will consistently fall on the outer surface and internal pressure loads will act in the positive direction of the local z axis. An example of a rectangular tank is provided to demonstrate the above procedure. Element properties are based on the thickness given under ELEMENT PROPERTIES command. The following example demonstrates the required input for a 300 mm slab modelled with 10 elements.

2-87

Design Per BS8007

2-88

Section 2D

UNIT MM ELEMENT PROPERTIES 1 TO 10 THI 300.0

2D.5 Wood & Armer Moments This is controlled by the SRA parameter. If the default value of zero is used, the design will be based on the Mx and My moments which are the direct results of STAAD analysis. The SRA parameter (Set Reinforcement Angle) can be manipulated to introduce WOOD & ARMER moments into the design replacing the pure Mx, My moments. These new design moments allow the Mxy moment to be considered when designing the section. Orthogonal or skew reinforcement may be considered. SRA set to 500 will assume an orthogonal layout. If however a skew is to be considered, an angle is given in degrees, measured between the local element x axis anti-clockwise (positive). The resulting Mx* and My* moments are calculated and shown in the design format.

Section 2D

2-89

Table 2D.1 - BS8007 Design Parameters Parameter Name FYMAIN * FC CLEAR SRA

Default Value

Description

* 460 N/mm2 * 30 N/mm2

Yield for all reinforcing steel

* 20 mm 0.0

SCON

1

TEMP

30°C

CRACK *

0.2 mm

Concrete grade. Distance from the outer surface to the edge of the bar. This is considered the same on both surfaces. Orthogonal reinforcement layout without considering torsional moment Mxy - slabs on -500. orthogonal reinforcement layout with Mxy used to calculate WOOD &ARMER moments for design. A* Skew angle considered in WOOD & ARMER EQUATIONS. A* is any angle in degrees. Parameter which indicates the type of slab ee. ground or suspended as defined in BS8007 1 = Suspended Slab 2 = Ground Slab Temperature range to be considered in thermal crack width calculations Limiting thermal crack width

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. *

Provided in current unit systems

Design Per BS8007

2-90

Section 2D

2-91

Design Per British Cold Formed Steel Code Section

2E

2E.1 General Provisions of BS 5950-5:1998, have been implemented. The program allows design of single (non -composite) members in tension, compression, bending, shear, as well as their combinations. Cold work of forming strengthening effects have been included as an option.

2E.2 Cross-Sectional Properties The user specifies the geometry of the cross-section by selecting one of the section shape designations from the Gross Section Property Tables published in the “The Steel Construction Institute”, (Design of Structures using Cold Formed Steel Sections). The Tables are currently available for the following shapes: 

Channel with Lips



Channel without Lips



Z with Lips

 

Pipe Tube

Shape assignment may be done using the member property pages of the graphical user interface (GUI) or by specifying the section designation symbol in the input file.

Design Per British Cold Formed Steel Code

2-92

Section 2E

The properties listed in the tables are gross section properties. STAAD.Pro uses unreduced section properties in the structure analysis stage. Both unreduced and effective section properties are used in the design stage, as applicable.

2E.3 Design Procedure The following two design modes are available: 1.

Code Checking The program compares the resistance of members with the applied load effects, in accordance with BS 5950-5:1998. Code checking is carried out for locations specified by the user vi a the SECTION command or the BEAM parameter. The results are presented in a form of a PASS/FAIL identifier and a RATIO of load effect to resistance for each member checked. The user may choose the degree of detail in the output data by setting the TRACK parameter.

2.

Member Selection The user may request that the program search the cold formed steel shapes database (BS standard sections) for alternative members that pass the code check and meet the least weight criterion. In addition, a minimum and/or maximum acceptable depth of the member may be specified. The program will then evaluate all database sections of the type initially specified (i.e., channel, angle, etc.) and, if a suitable replacement is found, presents design results for that section. If no section satisfying the depth restrictions or lighter than the initial one can be found, the program leaves the member unchanged, regardless of whether it passes the code check or not.

Section 2E

The program calculates effective section properties in accordance with Section 4 of the subject code. Cross-sectional properties and overall slenderness of members are checked for compliance with 

Clause 6.2.2, Maximum Effective Slenderness Ratio for members in Compression



Clause 4.2, Maximum Flat Width Ratios for Elements in Compression

2E.4 Design Equations Tensile Strength The allowable tensile strength, as calculated in STAAD as per BS5950-5, section 7 is described below. The tensile strength, P t of the member should be determined from clause 7.2.1

Pt  Ae p y Where Ae py

is the net area An determined in accordance with cl.3.5.4 is the design strength

Combined bending and tension As per clause 7.3 of BS 5950-5:1998 members subjected to both axial tension and bending should be proportioned such that the following relationships are satisfied at the ultimate limit state

My Ft M z   1 Pt M cz M cy And

Mz  M cz

1

2-93


2-94

Section 2E

and

My M cy



1

Where Ft Pt

is the applies tensile strength is the tensile capacity determined in accordance with clause 7.2.1 of the subject code M z ,M y ,M cz ,M cy are as defined in clause 6.4.2 of the subject code Compressive Strength The allowable Compressive strength, as calculated in STAAD as per BS5950-5, section 6 is described below For sections symmetrical about both principal axes or closed cross-sections which are not subjected to torsional flexural buckling, the buckling resistance under axial load, Pc, may be obtained from the following equation as per clause 6.2.3 of the subject code

Pc 

PE Pcs

   2  PE Pcs

For Sections symmetrical about a single axis and which are not subject to torsional flexural buckling, the buckling resistance under axial load, Pc, may be obtained from the following equation as per clause 6.2.4 of the subject code

P'c 

M c Pc ( M c  Pc e s )

Where the meanings of the symbols used are indicated in the subject clauses.

Section 2E

Torsional flexural buckling Design of the members which have at least one axis of symmetry, and which are subject to torsional flexural buckling should be done according to the stipulations of the clause 6.3.2 using factored slenderness ratio L E /r in place of actual slenderness ratio while reading Table 10 for the value of Compressive strength(p c ). Where

P    E  PTF



  

1/ 2

when PE > PTF

= 1 , otherwise

Where the meanings of the symbols used are indicated in the subject clause. Combined bending and compression Members subjected to both axial compression and bending should be checked for local capacity and overall buckling Local capacity check as per clause 6.4.2 of the subject code

My Fc M z   1 Pcs M cz M cy Overall buckling check as per clause 6.4.3 of the subject code For Beams not subjected to lateral buckling, the following relationship should be satisfied

Fc  Pc

My Mz  1    Fc  F  Cby M cy 1  c  Cbx M cz 1   P  P Ez   Ey  

For Beams subjected to lateral buckling, the following relationship should be satisfied

2-95


2-96

Section 2E

Fc M z   Pc M b Fc P cs Mz My M cz M cy Mb P Ez P Ey C bz ,C by

My  F  C by M cy 1  c   P  Ey  

1

is the applied axial load is the short strut capacity as per clause 6.2.3 is the applied bending moment about z axis is the applied bending moment about y axis is the moment capacity in bending about the local Z axis in the absence of F c and M y , as per clause 5.2.2 and 5.6 is the moment capacity in bending about the local Y axis, in the absence of F c and M z,as per clause 5.2.2 and 5.6 is the lateral buckling resistance moment as per clause 5.6.2 is the flexural buckling load in compression for bending about the local Z axis is the flexural buckling load in compression for bending about the local Y axis are taken as unity unless their values are specified by the user

The Mcz, Mcy and Mb are calculated from clause numbers 5.2.2 and 5.6 in the manner described herein below. Calculation of moment capacities For restrained beams, the applied moment based on factored loads should not be greater then the bending moment resistance of the section, M c Mcz = Szz  po Mcy = Syy  po 1/ 2   D Y   w s po  1.13  0.0019    py  t  280   

Where M cz is the Moment resistance of the section in z axis M cz is the Moment resistance of the section in z axis po is the limiting stress for bending elements under stress gradient and should not greater then design strength p y

Section 2E

For unrestrained beams the applied moment based on factored loads should not be greater than the smaller of the bending moment resistance of the section , M c , and the buckling resistance moment of the beam, M b Then buckling resistance moment, M b, may be calculated as follows

Mb 

M EMY

 B   B2  M E M Y

 Mc

Where

B 

M Y  (1   ) M E 2

MY

ME 5.6.2.2 

is the yield moment of the section , product of design strength p y and elastic modules of the gross section with respect to the compression flange Zc is the elastic lateral buckling resistance as per clause

is the Perry coefficient

Please refer clause numbers 5.2.2 and 5.6 of the subject code for a detailed discussion regarding the parameters used in the abovementioned equations. Shear Strength The maximum shear stress should not be greater then 0.7  p y as per clause 5.4.2 The average shear stress should not exceed the lesser of the shear yield strength, p v or the shear buckling strength, q cr as stipulated in clause 5.4.3 of the subject code.

2-97


2-98

Section 2E

The parameters are calculated as follows : pv = 0.6  p y 2

 1000t  2 qcr    N / mm D   Pv = A*Min(pv,qcr) Where Pv py t D

is is is is

the the the the

shear capacity in N/mm^2 design strength in N/mm^2 web thickness in mm web depth in mm

Combined bending and Shear For beam webs subjected to both bending and shear stresses the member should be designed to satisfy the following relationship as per the stipulations of clause 5.5.2 of the subject code

 Fv   Pv

2

2

  M       1 M   c

Where Fv M Mc

is the shear force is the bending moment acting at the same section as F v is the moment capacity determined in accordance with 5.2.2

The next table contains the input parameters for specifying values of design variables and selection of design options.

Section 2E

2-99

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. BRITISH COLD FORMED STEEL DESIGN PARAMETERS Parameter Name BEAM

Default Value 1.0

Description When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details. For TRUSS members only start and end locations are designed.

CMZ

1.0

Coefficient of equivalent uniform bending Cb. See BS:59505:1998,5.6. Used for Combined axial load and bending design.

CMY

1.0

Coefficient of equivalent uniform bending Cb. See BS:59505:1998,5.6. Used for Combined axial load and bending design.

CWY

1.0

Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See BS:5950-5:1998,3.4 Values: 0 – effect should not be included 1 – effect should be included

FLX

1

Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See BS:59505:1998, 5.6 Values: 0 – Section not subject to torsional flexural buckling 1 – Section subject to torsional flexural buckling

FU

430 MPa

Ultimate tensile strength of steel in current units.


2-100

Section 2E

BRITISH COLD FORMED STEEL DESIGN PARAMETERS Parameter Name

Default Value

FYLD

250 MPa

Description Yield strength of steel in current units.

KX

1.0

Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

KY

1.0

Effective length factor for overall buckling about the local Yaxis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

KZ

1.0

Effective length factor for overall buckling in the local Zaxis. It is a fraction and is unit-less. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

LX

Member length

Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

LY

Member length

Effective length for overall buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

Section 2E

2-101

BRITISH COLD FORMED STEEL DESIGN PARAMETERS Parameter Name

Default Value

Description

LZ

Member length

Effective length for overall buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

MAIN

0

0 – Check slenderness ratio 0 – Do not check slenderness ratio

NSF

1.0

DMAX

2540.0 cm.

RATIO

1.0

TRACK

0

Net section factor for tension members Maximum allowable depth. It is input in the current units of length. Permissible ratio of actual to allowable stresses This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 0 - Prints only the member number, section name, ratio, and PASS/FAIL status. 1 - Prints the design summary in addition to that printed by TRACK 1 2 - Prints member and material properties in addition to that printed by TRACK 2.

2E.5 Verification Problem In the next few pages are included a verification example for reference purposes.


2-102

Section 2E

Verification Problem-1 In this problem, we have assigned Channel sections with lips to different members. Member numbers 28 to 31 have been assigned section 230CLHS66X16,member numbers 3 TO 6 and 15 TO 19 have been assigned the section 230CLMIL70X30 and member numbers 1, 2, 7 TO 14 have been assigned the section 170CLHS56X18. These members have been designed as per BS 5950 Part 5. Other sections have been assigned from the AISI shapes database (American cold-formed steel) and designed in accordance with that code. The excerpts from the design output for member number 1 are given herein below.

Section 2E

1)

2-103

Bending Check As per Clause 5.2.2.2 of BS 5950 –Part 5 the limiting compressive stress(p o ) for stiffened webs is given by the minimum of 1/ 2  D  Y   po  1.13  0.0019 w  s   p y  t  280   

And p o = Py where Py = Min ( FYLD, 0.84XFU) = 361.2 N/mm 2 1/ 2  170  279.212   po  1.13  0.0019   361.2  1 . 8 280     So that

= 332.727 N/mm 2 The limiting compressive moments in local Y and Z axes will be given by M cz = S zz  po = 27632.4 X 332.727 = 9.19 X 10 6 N-mm M cy = S yy  p o = 27632.4 X 5427.50 = 3.46 X 10 6 N-mm Maximum bending moment about local Z = 2159 N-m at node 7 Maximum bending moment about local Y = 19.755 N-m at node 7 Bending Ratio Z = 2.15 X10 6 / 9.19 X10 6 = 0.235 ……hence verified Bending Ratio Y = 19755.3 / 3.46 X10 6 = 0.0057 ……hence verified Buckling resistance moment M b As per section 5.6.2, The buckling resistance moment

Mb 

M EMY

 B   B2  M E M Y

 Mc


2-104

Section 2E

Where, The Yield moment(M Y ) of section is given by M Y = S zz  p o = 9.19 X 10 6 N-mm The elastic buckling resistance moment(ME ) as per clause 5.6.2.2 is calculated to be 4.649 X10 6 N-mm

B  And,

B 

M Y  (1   ) M E 2 , so that

9.19  10 6  (1  0.0)4.649  10 6 2 = 2.325 X 10 10

Which gives

Mb 

4.649  10 6  9.19  10 6 2.325  1010  (2.325  1010 ) 2  4.649  10 6  9.19  10 6

= 9.98 X 10 6 N-mm

2)

Compression Check The Axial force induced in member# 1 is 3436.75 N The elastic flexural buckling load P E = 1.185 X 10 6 N The short strut capacity (Pcs ) is given by A e ff X py = 457.698 * 344 = 157448 N Perry Coefficient () = 0.02074

  [Pcs + (1+ )  PE ]  0.5 Pc  Buckling resistance

= 683512.45 N

PE Pcs

   2  PE Pcs

= 153782 N

Section 2E

For Channel section(being singly symmetric) as per clause 6.2.4

P'c  Buckling resistance

M c Pc ( M c  Pc e s )

Where The limiting compressive moment(M c ) in the relevant direction = 9.19 X 10 6 N-mm,as calculated above And the distance(e s ) of the geometric neutral axis of the gross cross section and that of the effective cross section = 38.24 m So that,

9.19  10 6  153782 Pc = 9.19  10 6  153782  38.24 = 93788.7 N

3436.75  0.0366 Compression ratio = 93788.7 ……hence verified 3)

Axial Compression and Bending Local capacity check as per clause 6.4.2

My Fc M z   1 Pcs M cz M cy



3436.75 2.15  10 6 19755.3   457.698  379.212 9.19  10 6 1.81  10 6 = 0.26

Over all buckling check : 6.4.3

Fc  Pc

My Mz  1    Fc  F c  Cby M cy 1   Cbx M cz 1   P   PEz  Ey  

= 0.2773

……hence verified

2-105


2-106

Section 2E

4)

Shear Check as per clause 5.4.2 and 5.4.3 pv = 0.6  p y = 0.6  379.212 = 227.52 N/mm 2 2

 1000t  2 qcr    N / mm D    1000  1.8  qcr     170  = 112.11 N/mm 2 2

P v = A*Min(p v,q cr ) = 112.11 N/mm 2 Shear resistance Y = 33579.4 N Shear resistance Z = 21148.6 N

5627.72  0.1675 Shear Ratio Y = 33579.4

Shear Ratio Z =

5)


67.114  0.0031 21148 .6


Shear Check with Bending as per clause 5.5.2

 Fv  P Shear with bending on Z =  v

2

  Mz      M cz

2

   1 

6  5627.72   2.15  10     6  33579.4   9.19  10 = 2

2

   =

…… hence verified

0.08327

2

 Fv   M y   1     M  P  cy  Shear with bending on Y =  v  2 2  67.114   19755.3      6  3.46  10  = =  21148.6  2

0.000….426


Section 2E

2-107

Input File: STAAD SPACE SET ECHO OFF INPUT WIDTH 79 UNIT FEET KIP JOINT COORDINATES 1 0 5 0; 2 0 5 10; 3 10 5 0; 4 10 5 10; 5 5 5 0; 6 5 5 10; 7 0 5 2; 8 0 5 4; 9 0 5 6; 10 0 5 8; 11 10 5 2; 12 10 5 4; 13 10 5 6; 14 10 5 8; 15 5 5 2; 16 5 5 4; 17 5 5 6; 18 5 5 8; 19 10 0 0; 20 10 0 10; 21 0 0 10; 22 0 0 0; MEMBER INCIDENCES 1 1 7; 2 3 11; 3 1 5; 4 2 6; 5 5 3; 6 6 4; 7 7 8; 8 8 9; 9 9 10; 10 10 2; 11 11 12; 12 12 13; 13 13 14; 14 14 4; 15 5 15; 16 15 16; 17 16 17; 18 17 18; 19 18 6; 20 7 15; 21 15 11; 22 8 16; 23 16 12; 24 9 17; 25 17 13; 26 10 18; 27 18 14; 28 1 22; 29 2 21; 30 3 19; 31 4 20; 32 1 21; 33 21 4; 34 4 19; 35 19 1; 36 2 20; 37 20 3; 38 3 22; 39 22 2; MEMBER PROPERTY COLDFORMED AMERICAN 32 TO 39 TABLE ST 3LU3X060 20 TO 27 TABLE ST 3HU3X075 MEMBER PROPERTY COLDFORMED BRITISH 28 TO 31 TABLE ST 230CLHS66X16 3 TO 6 15 TO 19 TABLE ST 230CLMIL70X30 1 2 7 TO 14 TABLE ST 170CLHS56X18 UNIT MMS PRINT MEMBER PROPERTIES LIST 32 20 28 3 1 SUPPORTS 19 TO 22 PINNED UNIT FEET DEFINE MATERIAL START ISOTROPIC STEEL E 4.176e+006 POISSON 0.3 DENSITY 0.489024 ALPHA 6.5e-006 DAMP 0.03 END DEFINE MATERIAL


2-108

Section 2E

CONSTANTS BETA 90 MEMB 20 TO 27 MATERIAL STEEL MEMB 1 TO 39 MEMBER TENSION 32 TO 39 UNIT FEET KIP LOAD 1 VERTICAL AND HORIZONTAL MEMBER LOAD 3 TO 6 20 TO 27 UNI GY -0.3 0 5 JOINT LOAD 1 2 FX 0.6 2 4 FZ -0.6 PERFORM ANALYSIS PRINT STATICS CHECK UNIT KGS CM PRINT JOINT DISP LIST 1 4 16 PRINT SUPPORT REACTIONS PRINT MEMBER FORCES LIST 3 24 28 UNIT KIP INCH PARAMETER 1 CODE AISI FYLD 55 ALL CWY 1 ALL BEAM 1 ALL TRACK 2 ALL CHECK CODE MEMB 20 21 PARAMETER 2 CODE BS5950 COLD TRACK 2 MEMB 1 TO 19 28 TO 31 CHECK CODE MEMB 1 2 FINISH

Section 2E

Output File: **************************************************** * * * STAAD.Pro * * Version Bld * * Proprietary Program of * * * * Date= * * Time= * * * * USER ID: * **************************************************** 1. STAAD SPACE 2. SET ECHO OFF MEMBER PROPERTIES. UNIT - CM ----------------MEMB PROFILE AX/ AY 32

ST

3LU3X060

20

ST

3HU3X075

28

ST

230CLHS66X16

3

ST

230CLMIL70X30

1

ST

170CLHS56X18

IZ/ AZ

IY/ SZ

IX/ SY

2.26 1.51 4.91 1.24 8.78 5.40

21.81 1.51 63.15 2.40 663.30 2.94

5.17 4.05 40.66 10.63 42.82 60.93

0.02 1.93 0.06 9.59 0.18 9.29

11.40 6.72 5.23 3.00

868.90 3.84 224.50 1.89

66.93 80.13 20.49 27.96

0.36 14.15 0.06 5.43

************ END OF DATA FROM INTERNAL STORAGE ************ **START ITERATION NO.

2

**NOTE-Tension/Compression converged after

2 iterations, Case=

STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. VERTICAL AND HORIZONTAL ***TOTAL APPLIED LOAD SUMMATION FORCE-X SUMMATION FORCE-Y SUMMATION FORCE-Z

( KIP = = =

FEET ) SUMMARY (LOADING 1.20 -18.00 -1.20

1 )

SUMMATION OF MOMENTS AROUND THE ORIGINMX= 84.00 MY= 12.00 MZ= ***TOTAL REACTION LOAD( KIP SUMMATION FORCE-X = SUMMATION FORCE-Y = SUMMATION FORCE-Z =

-96.00

FEET ) SUMMARY (LOADING -1.20 18.00 1.20

1 )

SUMMATION OF MOMENTS AROUND THE ORIGINMX= -84.00 MY= -12.00 MZ= MAXIMUM DISPLACEMENTS ( INCH /RADIANS) (LOADING MAXIMUMS AT NODE X = 1.56266E-02 1 Y = -4.80071E-01 16 Z = -1.74873E-02 4 RX= -8.28375E-03 6 RY= -2.10910E-05 14 RZ= -8.31623E-03 7

96.00 1)

************ END OF DATA FROM INTERNAL STORAGE ************

1 1

2-109


2-110

Section 2E JOINT DISPLACEMENT (CM -----------------JOINT

LOAD

1 4 16

1 1 1

X-TRANS

RADIANS)

Y-TRANS

0.0397 0.0305 0.0352

-0.0184 -0.0185 -1.2194

STRUCTURE TYPE = SPACE

Z-TRANS

X-ROTAN

-0.0339 -0.0444 -0.0392

Y-ROTAN

0.0074 -0.0074 0.0025

Z-ROTAN

0.0000 0.0000 0.0000

-0.0027 0.0025 0.0000

************** END OF LATEST ANALYSIS RESULT ************** SUPPORT REACTIONS -UNIT KGS CM STRUCTURE TYPE = SPACE ----------------JOINT 19 20 21 22

LOAD

FORCE-X

FORCE-Y

FORCE-Z

MOM-X

MOM-Y

MOM Z

1 1 1 1

-447.32 -447.10 174.26 175.85

2312.64 2041.85 1768.33 2041.85

85.08 186.39 187.79 85.05

0.00 0.00 0.00 0.00

0.00 0.00 0.00 0.00

0.00 0.00 0.00 0.00

************** END OF LATEST ANALYSIS RESULT ************** MEMBER END FORCES STRUCTURE TYPE = SPACE ----------------ALL UNITS ARE -- KGS CM (LOCAL ) MEMBER

LOAD

JT

AXIAL

SHEAR-Y

SHEAR-Z

TORSION

MOM-Y

MOM-Z

3

1

1 5

669.42 -669.42

1448.06 -767.67

2.70 -2.70

-1.68 1.68

-215.75 -196.10

61582.12 107256.50

24

1

9 17

-0.63 0.63

-0.06 0.06

-285.30 -395.09

-0.04 0.04

-0.08 -8366.18

1.04 -9.62

28

1

1 22

2155.98 -2155.98

-404.11 404.11

-85.05 85.05

0.00 0.00

12961.01 0.00

-61586.40 0.00

************** END OF LATEST ANALYSIS RESULT ************** STAAD.Pro CODE CHECKING - (AISI) *********************** UNITS ARE: IN, KIP, KIP-IN, KSI |-----------------------------------------------------------------------------| | MEMBER# 20 SECTION: 3HU3X075 LEN: 60.00 GOV.LOC: 60.00 | | STATUS: PASS RATIO = 0.285 GOV.MODE: Bend + Compress GOV.LOAD: 1 | | | | RESISTANCES: AX.TENS: 0.00 ECC.TENS: 0.00 COMPRESS: 7.51 | | BEND. Z: 28.21 BEND. Y: 30.98 SHEAR Z: 11.76 SHEAR Y: 5.88 | | | | FYLD: 55.00 COLD WORK FYLD: 55.71 FU: 58.00 A: 0.76 AE: 0.76 | | IZ: 1.5173E+00 IZE: 1.5173E+00 IY: 9.7684E-01 IYE: 9.7684E-01 | | SZE_T: 6.4841E-01 SZE_C: 6.4841E-01 SYE_T: 5.8539E-01 SYE_C: 7.3374E-01 | |-----------------------------------------------------------------------------|

|-----------------------------------------------------------------------------| | MEMBER# 21 SECTION: 3HU3X075 LEN: 60.00 GOV.LOC: 0.00 | | STATUS: PASS RATIO = 0.285 GOV.MODE: Bend + Compress GOV.LOAD: 1 | | | | RESISTANCES: AX.TENS: 0.00 ECC.TENS: 0.00 COMPRESS: 7.51 | | BEND. Z: 28.21 BEND. Y: 30.98 SHEAR Z: 11.76 SHEAR Y: 5.88 | | | | FYLD: 55.00 COLD WORK FYLD: 55.71 FU: 58.00 A: 0.76 AE: 0.76 | | IZ: 1.5173E+00 IZE: 1.5173E+00 IY: 9.7684E-01 IYE: 9.7684E-01 | | SZE_T: 1.0115E+00 SZE_C: 1.0115E+00 SYE_T: 7.3374E-01 SYE_C: 5.8539E-01 | |-----------------------------------------------------------------------------|

Section 2E

STAAD/Pro CODE CHECKING - (BS5950-5-v1.0) *********************** UNITS : MM, KN, KNM, MPA ------------------------------------------------------------------------------| MEMBER# 1 SECTION: 170CLHS56X18 LEN: 609.60 LOCATION: 609.60 | | STATUS: PASS RATIO = 0.277 GOV.MODE: Bend + Compress GOV.LOAD: 1 | |-------------------------------------------------------------------------|

MATERIAL DATA: Yield strength of steel: 379.21 N/mm2 Ultimate tensile strength: 430.00 N/mm2

SECTION PROPERTIES:(units - cm) Section Name: 170CLHS56X18 Member Length: 60.96 Gross Area(Ag): 5.46 Net Area (Ae): 4.58 z-z axis y-y axis Moment of inertia (I) : 237.68 21.99 Moment of inertia (Ie): 236.04 19.44 Elastic modulus (Zet): 27.91 5.21 Elastic modulus (Zec): 27.63 10.41

DESIGN DATA: Tension Capacity (Pt): Compression Capacity (Pc): Moment Capacity (Mc): Shear Capacity (Pc):

z-z axis 0.00 93.79 9.19 21.15

y-y axis 3.46 33.58

EACH CLAUSE CHECK UNDER CRITICAL LOAD : CLAUSE BS-6.3

COMBINATION Compression ratio - Axial

RATIO 0.037

BS-6.4

Bend-Compression ratio

0.277

BS-5.1

Bending Ratio - Z

0.235

BS-5.1

Bending Ratio - Y

0.006

BS-5.1

Biaxial Bending Ratio

0.241

BS-5.4

Shear Ratio - Z

0.168

BS-5.4

Shear Ratio - Y

0.003

BS-5.5.2

Bending -Z & Shear - Y Ratio

0.083

BS-5.5.2

Bending -Y & Shear - Z Ratio

0.000

2-111


2-112

Section 2E ------------------------------------------------------------------------------| MEMBER# 2 SECTION: 170CLHS56X18 LEN: 609.60 LOCATION: 609.60 | | STATUS: PASS RATIO = 0.282 GOV.MODE: Bend + Compress GOV.LOAD: 1 | |-------------------------------------------------------------------------| MATERIAL DATA: Yield strength of steel: 379.21 N/mm2 Ultimate tensile strength: 430.00 N/mm2 SECTION PROPERTIES:(units - cm) Section Name: 170CLHS56X18 Member Length: 60.96 Gross Area(Ag): 5.46 Net Area (Ae): 4.58 z-z axis y-y axis Moment of inertia (I) : 237.68 21.99 Moment of inertia (Ie): 236.04 21.99 Elastic modulus (Zet): 27.91 14.20 Elastic modulus (Zec): 27.63 5.43 DESIGN DATA: Tension Capacity (Pt): Compression Capacity (Pc): Moment Capacity (Mc): Shear Capacity (Pc):

z-z axis 0.00 93.79 9.19 21.15

y-y axis 1.81 33.58

EACH CLAUSE CHECK UNDER CRITICAL LOAD : CLAUSE BS-6.3

COMBINATION Compression ratio - Axial

RATIO 0.037

BS-6.4

Bend-Compression ratio

0.282

BS-5.1

Bending Ratio - Z

0.235

BS-5.1

Bending Ratio - Y

0.010

BS-5.1

Biaxial Bending Ratio

0.245

BS-5.4

Shear Ratio - Z

0.168

BS-5.4

Shear Ratio - Y

0.003

BS-5.5.2

Bending -Z & Shear - Y Ratio

0.083

BS-5.5.2

Bending -Y & Shear - Z Ratio

0.000

*********** END OF THE STAAD.Pro RUN ***********

Section 3 Canadian Codes

Aksf;ldkjasd

3-1

Concrete Design Per CSA Standard A23.3-94 Section

3A

3A.1 Design Operations STAAD can perform design of concrete beams, columns and slabs according to CSA STANDARD A23.3-94. Given the dimensions of a section, STAAD will calculate the required reinforcement necessary to resist the various input loads.


Prismatic (Rectangular, Square & Tee)

For Columns


For Slabs

4-noded Plate Elements


Concrete Design Per CSA Standard A23.3-94

3-2 Section 3A

UNIT MM MEMBER PROPERTIES 1 3 TO 7 9 PRISM YD 450. ZD 300. 11 14 PR YD 300. In the above input, the first set of members are rectangular (450mm depth and 300mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with a 300mm diameter.

3A.4 Slenderness Effects and Analysis Considerations STAAD provides the user with two methods of accounting for the slenderness effect in the analysis and design of concrete members. The first method is equivalent to the procedure presented in CSA STANDARD A23.3-94 Clause 10.13. STAAD accounts for the secondary moments, due to axial loads and deflections, when the PDELTA ANALYSIS command is used. After solving for the joint displacements of the structure, the program calculates the additional moments induced in the structure due to the P-Delta effect. Therefore, by performing a PDELTA ANALYSIS, member forces are calculated which will require no user modification before beginning member design. The second method by which STAAD allows the user to account for the slenderness effect is through user suppl ied moment magnification factors (see the parameter MMAG in Table 3A.1). Here the user approximates the additional moment by supplying a factor by which moments will be multiplied before beginning member design. This second procedure allows slenderness to be considered in accordance with Clause 10.14 of the code. It should be noted that STAAD does not factor loads automatically for concrete design. All the proper factored loads must be provided by the user before the ANALYSIS specification.

Section 3A

3-3

While performing a PDELTA ANALYSIS, all load cases must be defined as primary load cases. If the effects of separate load cases are to be combined, it should be done either by using the REPEAT LOAD command or by specifying the load information of these individual loading cases under one single load case. Usage of the LOAD COMBINATION command will yield incorrect results for PDELTA ANALYSIS.

3A.5 Design Parameters The program contains a number of parameters which are needed to perform design per CSA STANDARD A23.3-94. These parameters not only act as a method to input required data for code calculations but give the engineer control over the actual design process. Default values, which are commonly used numbers in conventional design practice, have been used for simplici ty. Table 3A.1 contains a list of available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 3A.1 - Canadian Concrete Design -CSA-A23.3-94 Parameters Parameter Name FYMAIN FYSEC

Default Value

Description

400N/mm2 400 N/mm

2

2

Yield Stress for main reinforcing steel. Yield Stress for secondary reinforcing steel.

FC

30 N/mm

CLT

40mm

Clear cover to reinforcing bar at top of cross section.

CLB

40mm

Clear cover to reinforcing bar at bottom of cross section.

CLS

40mm

Clear cover to reinforcing bar along the side of the cross section.

MINMAIN

Number 10 bar

Specified compressive strength of concrete.

Minimum main reinforcement bar size


3-4 Section 3A Table 3A.1 - Canadian Concrete Design -CSA-A23.3-94 Parameters Parameter Name

Default Value

Description

MINSEC

Number 10 bar

Minimum secondary (stirrup) reinforcement bar size.

MAXMAIN

Number 55 bar


SFACE

0.0

Distance of face of support from start node of beam. Used for shear and torsion calculation.

EFACE

0.0 Face of Support

Distance of face of support from end node of beam. Used for shear and torsion calculation. (Note: Both SFACE and EFACE are input as positive numbers).

REINF

0.0

Tied Column. A value of 1.0 will mean spiral.

TRACK

0.0

For TRACK = 0.0, Critical Moment will not be printed out with beam design report. For TRACK=1.0, moments will be printed.

MMAG

1.0

A factor by which the column design moments will be magnified.

NSECTION

12

Number of equally-spaced sections to be considered in finding critical moments for beam design.

WIDTH

ZD

DEPTH

YD

Width of the concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES. Depth of the concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.

3A.6 Beam Design Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are scanned to create moment a nd shear envelopes, and locate critical sections. The total number of sections considered is thirteen (start, end and 11 intermediate), unless that number is redefined with the NSECTION parameter. Design for Flexure Design for flexure is performed per the rules of Chapter 2 of CSA Standard A23.3-94. Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress

Section 3A

at the top face) moments are calculated for all active load cases at each of the thirteen sections. Each of these sections are designed to resist the critical sagging and hogging moments. Currently, design of singly reinforced sections only is permitted. If the section dimensions are inadequate as a singly reinforced section, such a message will be printed in the output. Flexural design of beams is performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account the changed effective depths of sections calculated on the basis of reinforcement provided after the preliminary design. Final provision of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per CSA Standard A23.3-94. Although exact curtailment lengths are not mentioned explicitly in the design output (which finally will be more or less guided by the detailer taking into account other practical considerations), the user has the choice of printing reinforcements provided by STAAD at 13 equally spaced sections from which the final detailed drawing can be prepared. The following annotations apply to the output for Beam Design. 1) LEVEL

- Serial number of bar level which may contain one or more bar group.

2) HEIGHT

- Height of bar level from the bottom of beam.

3) BAR INFOrmation - Reinforcement bar information specifying number of bars and size. 4) FROM

- Distance from the start of the beam to the start of the rebar.

5) TO

- Distance from the start of the beam to the end of the rebar.

3-5


3-6 Section 3A

6) ANCHOR (STA,END)

- States whether anchorage, either a hook or continuation, is needed at start (STA) or at the end (END) of the bar.

Design for Shear and Torsion Design for shear and torsion is performed per the rules of Chapter 4 of CSA Standard A23.3-94. Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design is performed at the start and end sections. The location along the member span for design is chosen as the effective depth + SFACE at the start, and effective depth + EFACE at the end. The load case which gives rise to the highest stirrup area for shear & torsion is chosen as the critical one. The calculations are performed assuming 2-legged stirrups will be provided. The additional longitudinal steel area r equired for torsion is reported. The stirrups are assumed to be U-shaped for beams with no torsion, and closed hoops for beams subjected to torsion.

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE CANADA FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

Section 3A

3A.7 Column Design Column design is performed per the rules of Chapters 7 & 8 of the CSA Standard A23.3-94. Columns are designed for axial force and biaxial moments at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. For rectangular and square sections, the reinforcement is always assumed to be equally distributed on each side. That means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE CANADIAN FYMAIN 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN

3A.8 Slab/Wall Design To design a slab or wall, it must be modeled using finite elements. The commands for specifying elements are in accordance with the relevant sections of the Technical Reference Manual. Elements are designed for the moments Mx and My using the same principles as those for beams in flexure. The width of the beam is assumed to be unity for this purpose. These moments are obtained from the element force output (see the relevant sections of the

3-7


3-8 Section 3A

Technical Reference Manual). The reinforcement required to resist Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist My moment is denoted as transverse reinforcement. The effective depth is calculated assuming #10 bars are provided. The parameters FYMAIN, FC, CLT and CLB listed in Table 3A.1 are relevant to sla b design. Other parameters mentioned in Table 3A.1 are not applicable to slab design. The output consists only of area of steel required. Actual bar arrangement is not calculated because an element most likely represents just a fraction of the total slab area.

Z Y My

X Mx TRANS. My

Mx LONG.

Example of Input Data for Slab/Wall Design UNIT NEWTON MMS START CONCRETE DESIGN CODE CANADA FYMAIN 415 ALL FC 35 ALL CLB 40 ALL DESIGN ELEMENT 15 TO 20 END CONCRETE DESIGN

3-9

Steel Design Per CSA Standard CAN/CSA-S16-01 Section

3B

3B.1 General Comments The design of structural steel members in accordance with the specification CAN/CSA S16-01 Limit States Design of Steel Structures is now implemented. This code supercedes the previous edition of the code CAN/CSA – S16.1-94. The design philosophy embodied in this specification is based on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit-state are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned t o resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria as augmented by the designer in specification of allowable member depths, desired section type, or other such parameters. The code checking portion of the program checks whether code requirements for each selected section are met and identifies the governing criteria.

Steel Design Per CSA Standard CAN/CSA-S16-01

3-10 Section 3B

The following sections describe the salient features of the STAAD implementation of CAN/CSA-S16-01. A detailed description of the design process along with its underlying concepts and assumptions is available in the specification document.


3B.3 Member Property Specifications For specification of member properties, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built -in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

3B.4 Built-in Steel Section Library The following information is provided for use when the built -in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members.

Section 3B

Almost all Canadian steel sections are available for input. A complete listing of the sections available in the built -in steel section library may be obtained by using the tools of the graphical user interface. Following is the description of the different types of sections available: Welded Wide Flanges (WW shapes) Welded wide flange shapes listed in the CSA steel tables can be designated using the same scheme used by CSA. The following example illustrates the specification of welded wide flange shapes.

100 TO 150 TA ST WW400X444 34 35 TA ST WW900X347 Wide Flanges (W shapes) Designation of wide flanges in STAAD is the same as that in CSA tables. For example,

10 TO 75 95 TO 105 TA ST W460X106 100 TO 200 TA ST W610X101 S, M, HP shapes In addition to welded wide flanges and regular wide flanges, other I shaped sections like S, M and HP shapes are also available. The designation scheme is identical to that listed in the CSA tables. While specifying the sections, it should be remembered that the portion after the decimal point should be omitted. Thus, M310X17.6 should be specified as M310X17 and S180X22.8 should be specified as S180X22. Examples illustrating specifications of these shapes are provided below.

3-11


3-12 Section 3B

10 TO 20 BY 2 TA ST S510X98 45 TO 55 TA ST M150X6 88 90 96 TA ST HP310X79 Channel Sections (C & MC shapes) C and MC shapes are designated as shown in the following example. As in S, M and HP sections, the portion after the decimal point must be omitted in section designations. Thus, MC250X42.4 should be designated as MC250X42.

55 TO 90 TA ST C250X30 30 TO 45 TA ST MC200X33 Double Channels Back to back double channels, with or without spacing between them, are specified by preceding the section designation by the letter D. For example, a back to back double channel section C200X28 without any spacing in between should be specified as:

100 TO 120 TA D C200X28 If a spacing of 2.5 length units is used, the specification should be as follows:

100 TO 120 TA D C200X28 SP 2.5 Note that the specification SP after the section designation is used for providing the spacing. The spacing should always be provided in the current length unit.

Section 3B

Angles To specify angles, the angle name is preceded by the letter L. Thus, a 200X200 angle with a 25mm thickness is designated as L200X200X25. The following examples illustrate angle specifications.

75 TO 95 TA ST L100X100X8 33 34 35 TA ST L200X100X20 Note that the above specification is for “standard” angles. In this specification, the local z-axis (see Fig. 2.6 in the Technical Reference Manual) corresponds to the Y‟-Y‟ axis shown in the CSA table. Another common practice of specifying angles assumes the local y-axis to correspond to the Y‟-Y‟ axis. To specify angles in accordance with this convention, the reverse angle designation facility has been provided. A reverse angle may be specified by substituting the word ST with the word RA. Refer to the following example for details.

10 TO 15 TA RA L55X35X4 The local axis systems for STANDARD and REVERSE angles is shown in Fig. 2.6 of the STAAD Technical Reference manual. Double Angles To specify double angles, the specification ST should be substituted with LD (for long leg back to back) or SD (short leg back to back). For equal angles, either SD or LD will serve the purpose. Spacing between angles may be provided by using the word SP followed by the value of spacing (in current length unit) after section designation.

25 35 45 TA LD L150X100X16 80 TO 90 TA SD L125X75X6 SP 2.5

3-13


3-14 Section 3B

The second example above describes a double angle section consisting of 125X75X6 angles with a spacing of 2.5 length units. Tees Tee sections obtained by cutting W sections may be specified by using the T specification instead of ST before the name of the W shape. For example:

100 TO 120 TA T W200X42 will describe a T section cut from a W200X42 section. Rectangular Hollow Sections These sections may be specified in two possible ways. Those sections listed in the CSA tables may be specified as follows.

55 TO 75 TA ST TUB80X60X4

TUB 80 X 60 X 4 Tube Symbol

Height (in) X 10

Thickness (in) X16

Width (in.) X10

In addition, any tube section may be specified by using the DT(for depth), WT(for width), and TH(for thickness) specifications.

Section 3B

For example:

100 TO 200 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 will describe a tube with a depth of 8 in., width of 6 in. and a wall thickness of 0.5 inches. Note that the values of depth, width and thickness must be provided in current length unit. Circular Hollow Sections Sections listed in the CSA tables may be provided as follows:

15 TO 25 TA ST PIP33X2.5 PIP 33 X 2.5 Pipe Symbol

Thickness (mm) (Upto first decimal place only) Diameter (mm) without decimal point

In addition to sections listed in the CSA tables, circular hollow sections may be specified by using the OD (outside diameter) and ID (inside diameter) specifications. For example:

70 TO 90 TA ST PIPE OD 10.0 ID 9.0 will describe a pipe with an outside diameter of 10 length units and inside diameter of 9.0 length units. Note that the values of outside and inside diameters must be provided in terms of current length unit.

3-15


3-16 Section 3B

Sample input file to demonstrate usage of Canadian shapes STAAD SPACE UNIT METER KNS JOINT COORD 1 0 0 0 17 160 0 0 MEMBER INCIDENCES 1 1 2 16 UNIT CM MEMBER PROPERTIES CANADIAN * W SHAPES 1 TA ST W250X18 * WW SHAPES 2 TA ST WW700X185 * S SHAPES 3 TA ST S200X27 * M SHAPES 4 TA ST M130X28 * HP SHAPES 5 TA ST HP310X132 * MC CHANNELS 6 TA ST MC150X17 * C CHANNELS 7 TA ST C180X18 * DOUBLE CHANNELS 8 TA D C250X37 SP 1.0 * ANGLES 9 TA ST L55X35X5 * REVERSE ANGLES 10 TA RA L90X75X5 * DOUBLE ANGLES, LONG LEG BACK TO BACK 11 TA LD L100X90X6 SP 2.0 * DOUBLE ANGLES, SHORT LEG BACK TO BACK 12 TA SD L125X75X6 SP 2.5 * TUBES 13 TA ST TUB120807

Section 3B

* TUBES 14 TA ST TUBE DT 16.0 WT 8.0 TH 0.8 * PIPES 15 TA ST PIP273X6.3 * PIPES 16 TA ST PIPE OD 16.0 ID 13.0 PRINT MEMBER PROPERTIES FINISH

3B.5 Section Classification The CSA specification allows inelastic deformation of section elements. Thus, local buckling becomes an important criterion. Steel sections are classified as plastic (Class 1), compact (Class 2), non compact (Class 3) or slender element (Class 4) sections depending upon their local buckling characteristics (See Clause 11.2 and Table 1 of CAN/CSA-S16-01). This classification is a function of the geometric properties of the section. The design procedures are different depending on the section class. STAAD determines the section classification for the standard shapes and user specified shapes. Design is performed for sections that fall into the category of Class 1,2 or 3 sections only. Class 4 sect ions are not designed by STAAD.

3B.6 Member Resistances The member resistances are calculated in STAAD according to the procedures outlined in section 13 of the specification. These depend on several factors such as members unsupported lengths, cross-sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Note that the program automatically takes into consideration appropriate resistance factors to calculate member resistances. Explained here is the procedure adopted i n STAAD for calculating the member resistances.

3-17


3-18 Section 3B

Axial Tension The criteria governing the capacity of tension members is based on two limit states. The limit state of yielding in the gross section is intended to prevent excessive elongation of the member. The second limit state involves fracture at the section with the minimum effective net area. The net section area may be specified by the user through the use of the parameter NSF (see Table 3B.1). STAAD calculates the tension capacity of a member based on these two limits states per Cl.13.2 of CAN/CSA-S16-01. Parameters FYLD, FU and NSF are applicable for these calculations. Axial Compression The compressive resistance of columns is determined based on Clause 13.3 of the code. The equations presented in th is section of the code assume that the compressive resistance is a function of the compressive strength of the gross section (Gross section Area times the Yield Strength) as well as the slenderness factor (KL/r ratios). The effective length for the calcula tion of compression resistance may be provided through the use of the parameters KX, KY, KZ, LX, LY and LZ (see Table 3B.1). Some of the aspects of the axial compression capacity calculations are : 1) For frame members not subjected to any bending, and for truss members, the axial compression capacity in general column flexural buckling is calculated from Cl.13.3.1 using the slenderness ratios for the local Y-Y and Z-Z axis. The parameters KY, LY, KZ and LZ are applicable for this. 2) For single angles, which ar e frame members not subjected to any bending or truss members, the axial compression capacity in general column flexural buckling and local buckling of thin legs is calculated using the rules of the AISC - LRFD code, 2 nd ed., 1994. The reason for this is that the Canadian code doesn‟t provide any clear guidelines for calculating this value. The parameters KY, LY, KZ and LZ are applicable for this. 3) The axial compression capacity is also calculated by taking flexural-torsional buckling into account. The rules of Appendix D, page 1-109 of CAN/CSA-S16-01are used for this

Section 3B

purpose. Parameters KX and LX may be used to provide the effective length factor and effective length value for flexural torsional buckling. Flexural-torsional buckling capacity is computed for single channels, single angles, Tees and Double angles. 4) The variable “n” in Cl.13.3.1 is assumed as 2.24 for WWF shapes and 1.34 for all other shapes. 5) While computing the general column flexural buckling capacity of sections with axial compression + bendin g, the special provisions of 13.8.1(a), 13.8.1(b) and 13.8.1(c) are applied. For example, Lambda = 0 for 13.8.1(a), K=1 for 13.8.1(b), etc.) Bending The laterally unsupported length of the compression flange for the purpose of computing the factored momen t resistance is specified in STAAD with the help of the parameter UNL. If UNL is less than one tenth the member length (member length is the distance between the joints of the member), the member is treated as being continuously laterally supported. In this case, the moment resistance is computed from Clause 13.5 of the code. If UNL is greater than or equal to one tenth the member length, its value is used as the laterally unsupported length. The equations of Clause 13.6 of the code are used to arrive at th e moment of resistance of laterally unsupported members. Some of the aspects of the bending capacity calculations are : 1) The weak axis bending capacity of all sections except single angles is calculated as For Class 1 & 2 sections, Phi*Py*Fy For Class 3 sections, Phi*Sy*Fy where Phi = Resistance factor = 0.9 Py = Plastic section modulus about the local Y axis Sy = Elastic section modulus about the local Y axis Fy = Yield stress of steel

3-19


3-20 Section 3B

2) For single angles, the bending capacities are calculated for the principal axes. The specifications of Section 5, page 6-283 of AISC-LRFD 1994, 2 nd ed., are used for this purpose because the Canadian code doesn‟t provide any clear guidelines for calculating this value. 3) For calculating the bending capacity about the Z-Z axis of singly symmetric shapes such as Tees and Double angles, CAN/CSA-S16-01 stipulates in Clause 13.6(d), page 1-31, that a rational method, such as that given in SSRC‟s Guide to Stability Design Criteria of Metal Structures, be used. Instead, STAAD uses the rules of Section 2c, page 6-55 of AISC-LRFD 1994, 2 nd ed. Axial compression and bending The member strength for sections subjected to axial compression and uniaxial or biaxial bending is obtained through the use of interaction equations. In these equations, the additional bending caused by the action of the axial load is accounted for by using amplification factors. Clause 13.8 of the code provides the equations for this purpose. If the summation of the left hand side of these equations exceed 1.0 or th e allowable value provided using the RATIO parameter (see Table 3B.1), the member is considered to have FAILed under the loading condition. Axial tension and bending Members subjected to axial tension and bending are also designed using interaction equations. Clause 13.9 of the code is used to perform these checks. The actual RATIO is determined as the value of the left hand side of the critical equation. Shear The shear resistance of the cross section is determined using the equations of Clause 13.4 of the code. Once this is obtained, the ratio of the shear force acting on the cross section to the shear resistance of the section is calculated. If any of the ratios (for both local Y & Z axes) exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the section is

Section 3B

3-21

considered to have failed under shear. The code also requires that the slenderness ratio of the web be within a certain limit (See Cl.13.4.1.3, page 1-29 of CAN/CSA-S16-01). Checks for safety in shear are performed only if this value is within the allowable limit. Users may by-pass this limitation by specifying a value of 2.0 for the MAIN parameter.

3B.7 Design Parameters The design parameters outlined in Table 3B.1 may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program and thus allow the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Canadian Steel Design Parameters Parameter Name

Default Value

Description

KT

1.0

K value for flexural torsional buckling.

KY

1.0

K value for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.

KZ

1.0

K value for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.

LT

Member Length

Length for flexural torsional buckling.

LY

Member Length

Length for general column flexural buckling about the local Y-axis. Used to calculate slenderness ratio.


3-22 Section 3B Canadian Steel Design Parameters Parameter Name LZ

Default Value Member Length

Description Length for general column flexural buckling about the local Z-axis. Used to calculate slenderness ratio.

FYLD

300.0 MPa


FU

345.0 MPa

Ultimate strength of steel.

NSF

1.0


UNT

Member Length

Unsupported length in bending compression of the top flange for calculating moment resistance.

UNB

Member Length

Unsupported length in bending compression of the bottom flange for calculating moment resistance.

MAIN

0.0

0.0 = Check slenderness ratio against the limits. 1.1 = Suppress the slenderness ratio check. 2.0 = Check slenderness ratio only for column buckling, not for web (See Section 3B.6, Shear)

CB

1.0

Greater than 0.0 and less than 2.5 : Value of Omega_2 (Cl.13.6) to be used for calculation. Equal to 0.0 : Calculate Omega_2

CMY

1.0

1.0 = Do not calculate Omega-1 for local Y axis. 2.0 = Calculate Omega-1 for local Y axis. Used in Cl.13.8.4 of code

CMZ

1.0

1.0 = Do not calculate Omega-1 for local Z axis. 2.0 = Calculate Omega-1 for local Z axis. Used in Cl.13.8.4 of code

TRACK

0.0

0.0 = Report only minimum design results. 1.0 = Report design strengths also. 2.0 = Provide full details of design.

DMAX

45.0 in.

Maximum allowable depth (Applicable for member selection)

DMIN

0.0 in.

Minimum required depth (Applicable for member selection)

RATIO

1.0

Permissible ratio of actual load effect to the design strength.

Section 3B

3-23

Canadian Steel Design Parameters Parameter Name BEAM

Default Value 0.0

Description 0.0 = design only for end moments and those at locations specified by SECTION command. 1.0 = Perform design for moments at twelfth points along the beam.

DFF

None(Mandatory for deflection check)

DJ1


Joint No. denoting start point for calculation of “deflection length”

DJ2

End Joint of member

Joint No. denoting end point for calculation of “deflection length”

“Deflection Length”/Maxm. Allowable local deflection.

3B.8 Code Checking The purpose of code checking is to check whether the provi ded section properties of the members are adequate. The adequacy is checked as per the CAN/CSA-S16-01 requirements. Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam. When no sections are specified and the BEAM parameter is set to zero (default), design will be based on member start and end forces only. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start joint) and magnitudes of the governing forces and moments are also printed. The extent of detail of the output can be controlled by using the TRACK parameter.


3-24 Section 3B

Example of commands for CODE CHECKING:

UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 UNL 15 MEMB 3 4 RATIO 0.9 ALL CHECK CODE MEMB 3 4

3B.9 Member Selection The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a chann el will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Member selection cannot be performed on TUBES, PIPES or members listed as PRISMATIC.

Section 3B

Example of commands for MEMBER SELECTION:

UNIT NEWTON METER PARAMETER FYLD 330E6 MEMB 3 4 NSF 0.85 ALL KY 1.2 MEMB 3 4 UNL 15 MEMB 3 4 RATIO 0.9 ALL SELECT MEMB 3 4

3B.10 Tabulated Results of Steel Design Results of code checking and member selecti on are presented in a tabular format. The term CRITICAL COND refers to the section of the CAN/CSA-S16-01 specification which governed the design. If the TRACK parameter is set to 1.0, factored member resistances will be printed. Following is a description of some of the items printed. CR TR VR MRZ MRY

= = = = =

Factored Factored Factored Factored Factored

compressive resistance tensile resistance shear resistance moment resistance (about z-axis) moment resistance (about y-axis)

Further details can be obtained by setting TRACK to 2.0. CR1 = CAPACITY (C r ) PER 13.8.2(a) CR2 = CAPACITY (C r ) PER 13.8.2(b) CRZ = SEE 13.8.2(b) for uniaxial bending (called C RX in that Clause) CTORFLX = Capacity in accordance with 13.8.2(c)

3-25


3-26 Section 3B

3B.11 Verification Problems In the next few pages are included 3 verification examples for reference purposes. Since the S16-01 code is similar in many respects to the previous edition of the code (CAN/CSA S16.1 -94), the solved examples of the 1994 edition of the CISC Handbook have been used as reference material for these examples.

Section 3B

3-27

Verification Problem No. 1 TITLE

Steel beam with uniform load, wide flange section.

TYPE

Static analysis, 3D beam element.

REFERENCE: CAN/CSA-S16.1-94, National Standard of Canada, Limit States Design of Steel Structures. The Canadian Standards Association, 1994 with CISC (Canadian Institute of Steel Construction) handbook. CISC Example 1 page 5_91. PROBLEM:

Find the interaction ratio, beam resistance and beam deflection.

GIVEN:

E = 200000 MPa (STEEL). Fy = 300 Mpa CSA G40.21-M Beam has a 8.0 m span; Ky is 1.0, Kz 1.0, unsupported length 1.0 m Allowable Live Load deflection, L/300 = 8000/300 = 27 mm Factored Uniform Load IS 7 kN/m DEAD, 15 kN/m LIVE. Steel section is W410X54.

SOLUTION COMPARISON: CAN/CSA-S16 Interaction Ratio

Beam Resistance

Beam Deflection

(kN*m)

(mm)

REFERENCE

0.88

284

21

STAAD.Pro

0.883

283.20

20.81


3-28 Section 3B

**************************************************** * * * STAAD.Pro * * Version Bld * * Proprietary Program of * * Research Engineers, Intl. * * Date= * * Time= * * * * USER ID: * ****************************************************

1. 3. 4. 5. 7. 8. 9. 10. 11. 13. 14. 16. 17. 18. 20. 21. 22. 24. 25. 26. 27. 29. 30. 31. 33. 34. 36.

STAAD SPACE VERIFICATION CISC 1994 HANDBOOK EXAMPLE PAGE 5-91 * CISC EXAMPLE 1 PAGE 5-91, LIMIT STATES DESIGN, CSA-S16.1-94 * SIMPLY SUPPORTED BEAM WITH UNIFORM LOAD * LIVE LOAD DEFLECTION OF L/300 UNIT MMS KN JOINT COORDINATES 1 0 0 0; 2 8000 0 0 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTY CANADIAN 1 TABLE ST W410X54 CONSTANTS E STEEL ALL POISSON 0.3 ALL SUPPORTS 1 PINNED 2 FIXED BUT MY MZ UNIT METER KN LOAD 1 DEAD MEMBER LOAD 1 UNI GY -7 LOAD 2 LIVE MEMBER LOAD 1 UNI GY -15 LOAD COMB 3 1.25DL + 1.5 LL 1 1.25 2 1.5 PERFORM ANALYSIS P R O B L E M S T A T I S T I C S -----------------------------------

NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 5 DOF TOTAL PRIMARY LOAD CASES = 2, TOTAL DEGREES OF FREEDOM = SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS REQRD/AVAIL. DISK SPACE = 12.0/ 19641.6 MB

37. LOAD LIST 2

2 5

Section 3B 38. PRINT SECTION DISPLACEMENTS MEMBER SECTION DISPLACEMENTS ---------------------------UNIT =INCHES FOR FPS AND CM FOR METRICS/SI SYSTEM MEMB

LOAD

1

2

GLOBAL X,Y,Z DISPL FROM START TO END JOINTS AT 1/12TH PTS 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

MAX LOCAL

DISP =

0.0000 -1.0528 -1.8086 -2.0812 -1.8086 -1.0528 0.0000

2.08115

AT

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 400.00

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 LOAD

-0.5471 -1.4824 -2.0120 -2.0120 -1.4824 -0.5471 2

0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

L/DISP=

************ END OF SECT DISPL RESULTS ***********

40. 41. 42. 43. 44. 45. 46. 47.

LOAD LIST 3 PARAMETER CODE CANADIAN TRACK 2 ALL UNL 1 ALL FYLD 300000 ALL BEAM 1 ALL CHECK CODE ALL STAAD.PRO CODE CHECKING - (CAN/CSA-S16-01) ******************************************

ALL UNITS ARE - KNS

MET

(UNLESS OTHERWISE NOTED)

MEMBER

TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1 ST

W410X54

(CANADIAN SECTIONS) CSA-13.8.2+ 0.883 0.00 -250.00

PASS 0.00 C

3 4.00

MEMBER PROPERTIES (UNIT = CM) ----------------------------CROSS SECTION AREA = 6.84E+01 IZ = 1.86E+04 SZ = 9.26E+02 IY = 1.02E+03 SY = 1.15E+02

MEMBER LENGTH = PZ = 1.05E+03 PY = 1.77E+02

8.00E+02

MATERIAL PROPERTIES (UNIT = MPA) -------------------------------FYLD = 300.0

FU = 345.0

SECTION CAPACITIES (UNIT - KN,M) --------------------------------CR1 = 1.846E+03 CR2 = 2.732E+02 CRZ = 1.570E+03 CTORFLX = 2.732E+02 TENSILE CAPACITY = 1.805E+03 COMPRESSIVE CAPACITY = 2.732E+02 FACTORED MOMENT RESISTANCE : MRY = 4.778E+01 MRZ = 2.832E+02 FACTORED SHEAR RESISTANCE : VRY = 5.379E+02 VRZ = 4.604E+02

384

3-29


3-30 Section 3B

MISCELLANEOUS INFORMATION -------------------------NET SECTION FACTOR FOR TENSION = 1.000 KL/RY = 207.170 KL/RZ = 48.447 ALLOWABLE KL/R = 300.000 UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 1.000 OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00 SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 0.000E+00 SLENDERNESS RATIO OF WEB (H/W) = 5.08E+01 48. STEEL TAKE OFF ALL STEEL TAKE-OFF -------------PROFILE

LENGTH(METE)

WEIGHT(KN

)

In Steel Takeoff the density of steel is assumed for members with no density. ST W410X54 8.00 4.203 PRISMATIC STEEL 0.00 0.000 ---------------TOTAL = 4.203 ************ END OF DATA FROM INTERNAL STORAGE ************

49. FINISH

Section 3B

Verification Problem No. 2 TITLE:

Steel beam/column, wide flange section.

TYPE:

Static Analysis, 3D beam element.

REFERENCE: CAN/CSA-S16.1-94, National Standard of Canada, Limit States Design of Steel Structures. The Canadian Standards Association, 1994 with CISC (Canadian Institute of Steel Construction) handbook. CISC Handbook Example, Page 4_106. PROBLEM:

Find the interaction ratio, beam and column resistance.

3-31


3-32 Section 3B

GIVEN:

E = 200000 MPa (STEEL). Fy = 300 MPa CSA G40.21-M Beam/Column has a 3.7 m span, Ky is 1.0, Kz 1.0 factored axial load is 2000 kN and end moments of 200 kN*m and 300 kN*m Steel section is W310X129

SOLUTION COMPARISON: CAN/CSA-S16 Interaction

Beam Resistance

Ratio

(kN*m)

Column Resistance (kN)

REFERENCE

0.96

583

3800

STAAD.Pro

0.98

584

3820

Section 3B


1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29.

STAAD SPACE VERIFICATION CISC 1994 HANDBOOK EXAMPLE PAGE 4-106 * * COMPRESSION + MAJOR AXIS BENDING * UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 0 3.7 0 * MEMBER INCIDENCES 1 1 2 * MEMBER PROPERTY CANADIAN 1 TABLE ST W310X129 * CONSTANTS E STEEL ALL POISSON STEEL ALL * SUPPORTS 1 FIXED BUT MX MZ 2 FIXED BUT FY MY MZ * LOAD 1 FACTORED LOAD JOINT LOAD 2 FY -2000 2 MZ 200 1 MZ 300 * PDELTA 3 ANALYSIS P R O B L E M S T A T I S T I C S -----------------------------------

NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 5 DOF TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS REQRD/AVAIL. DISK SPACE = 12.0/ 19641.2 MB ++ Adjusting Displacements ++ Adjusting Displacements ++ Adjusting Displacements

8:54:35 8:54:35 8:54:35

2 5

3-33


3-34 Section 3B

31. PRINT MEMBER FORCES MEMBER END FORCES ----------------ALL UNITS ARE -- KN MEMBER

LOAD

1

STRUCTURE TYPE = SPACE METE

JT

AXIAL

SHEAR-Y

SHEAR-Z

TORSION

MOM-Y

MOM-Z

1 2

2000.00 -2000.00

135.14 -135.14

0.00 0.00

0.00 0.00

0.00 0.00

300.00 200.00

1

************** END OF LATEST ANALYSIS RESULT **************

33. 34. 35. 36. 37. 38. 39.

PARAMETER CODE CANADIAN TRACK 2 ALL FYLD 300000 ALL LY 3.7 ALL LZ 3.7 ALL CHECK CODE ALL STAAD.PRO CODE CHECKING - (CAN/CSA-S16-01) ******************************************

ALL UNITS ARE - KNS MEMBER

MET


TABLE

RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1 ST

W310X129

(CANADIAN SECTIONS) CSA-13.8.2C 0.980 0.00 300.00

PASS 2000.00 C

1 0.00



3.70E+02


FU = 345.0

SECTION CAPACITIES (UNIT - KN,M) --------------------------------CR1 = 4.459E+03 CR2 = 3.820E+03 CRZ = 4.296E+03 CTORFLX = 3.820E+03 TENSILE CAPACITY = 4.359E+03 COMPRESSIVE CAPACITY = 3.820E+03 FACTORED MOMENT RESISTANCE : MRY = 2.672E+02 MRZ = 5.840E+02 FACTORED SHEAR RESISTANCE : VRY = 7.419E+02 VRZ = 1.505E+03

Section 3B MISCELLANEOUS INFORMATION -------------------------NET SECTION FACTOR FOR TENSION = 1.000 KL/RY = 47.477 KL/RZ = 27.094 ALLOWABLE KL/R = 200.000 UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 3.700 OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00 SHEAR FORCE (KNS) : Y AXIS = 1.351E+02 Z AXIS = 0.000E+00 SLENDERNESS RATIO OF WEB (H/W) = 2.12E+01

40. STEEL MEMBER TAKE OFF ALL STEEL TAKE-OFF -------------PROFILE

LENGTH(METE)

WEIGHT(KN

)

In Steel Takeoff the density of steel is assumed for members with no density. ST W310X129 PRISMATIC STEEL

3.70 0.00

MEMBER

LENGTH (METE)

1

PROFILE ST

W310X129

4.694 0.000 ---------------TOTAL = 4.694 WEIGHT (KN ) 3.70

4.694


42. FINISH

3-35


3-36 Section 3B

Verification Problem No. 3 TITLE:

Steel beam/column, wide flange section.

TYPE:

Static Analysis, 3D beam element.

REFERENCE: CAN/CSA-S16.1-94, National Standard of Canada, Limit States Design of Steel Structures. The Canadian Standards Association, 1994 with CISC (Canadian Institute of Steel Construction) handbook. CISC Handbook Example, Page 4_108. PROBLEM:

Find the interaction ratio, beam and column resistance.

Section 3B

GIVEN:

3-37

E = 200000 MPa (STEEL). Fy = 300 MPa CSA G40.21-M Beam/Column has a 3.7 m span, Ky is 1.0, Kz 1.0, Lu = 3.7 m factored axial load is 2000 kN and end moments of 200 kN*m and 300 kN*m in the strong axis and 100 kN*m at each end in the weak axis. Steel section is W310X143.

SOLUTION COMPARISON: CAN/CSA-S16 Interaction

Beam Resistance

Ratio

(kN*m) weak

strong 653

REFERENCE

0.998

300

STAAD.Pro

1.00

299

650

Column Resistance (kN) 4200 4222


3-38 Section 3B


1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31.

STAAD SPACE VERIFICATION CISC 1994 HANDBOOK EXAMPLE PAGE 4-108 * * ( COMPRESSION + BIAXIAL BENDING ) * UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 0 3.7 0 * MEMBER INCIDENCES 1 1 2 * MEMBER PROPERTY CANADIAN 1 TABLE ST W310X143 * CONSTANTS E STEEL ALL POISSON STEEL ALL * SUPPORTS 1 FIXED BUT MX MZ 2 FIXED BUT FY MX MY MZ * LOAD 1 FACTORED LOAD JOINT LOAD 2 FY -2000 2 MZ 200 2 MX 100 1 MZ 300 1 MX 100 * PERFORM ANALYSIS P R O B L E M S T A T I S T I C S -----------------------------------

NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 6 DOF TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS REQRD/AVAIL. DISK SPACE = 12.0/ 19641.2 MB

2 6

Section 3B

33. 34. 35. 36. 37. 38. 39. 40.

PARAMETER CODE CANADIAN CMY 2 ALL CMZ 2 ALL CB 1 ALL TRACK 2 ALL FYLD 300000 ALL CHECK CODE ALL STAAD.PRO CODE CHECKING - (CAN/CSA-S16-01) ******************************************

ALL UNITS ARE - KNS MEMBER

MET


RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= *

1 ST

TABLE

W310X143 FAIL 2000.00 C

(CANADIAN SECTIONS) CSA-13.8.2A 1.000 -100.00 300.00

1 0.00



3.70E+02


FU = 345.0

SECTION CAPACITIES (UNIT - KN,M) --------------------------------CR1 = 4.912E+03 CR2 = 4.222E+03 CRZ = 4.737E+03 CTORFLX = 4.222E+03 TENSILE CAPACITY = 4.802E+03 COMPRESSIVE CAPACITY = 4.912E+03 FACTORED MOMENT RESISTANCE : MRY = 2.987E+02 MRZ = 6.504E+02 FACTORED SHEAR RESISTANCE : VRY = 8.037E+02 VRZ = 1.678E+03 MISCELLANEOUS INFORMATION -------------------------NET SECTION FACTOR FOR TENSION = 1.000 KL/RY = 47.077 KL/RZ = 26.802 ALLOWABLE KL/R = 200.000 UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 3.700 OMEGA-1 (Y-AXIS) = 0.40 OMEGA-1 (Z-AXIS) = 0.40 OMEGA-2 = 1.00 SHEAR FORCE (KNS) : Y AXIS = 1.351E+02 Z AXIS = 5.405E+01 SLENDERNESS RATIO OF WEB (H/W) = 1.98E+01

3-39


3-40 Section 3B

41. STEEL MEMBER TAKE OFF ALL STEEL TAKE-OFF -------------PROFILE

LENGTH(METE)

WEIGHT(KN

)

In Steel Takeoff the density of steel is assumed for members with no density. ST W310X143 3.70 5.171 PRISMATIC STEEL 0.00 0.000 ---------------TOTAL = 5.171 MEMBER 1

PROFILE ST

W310X143

LENGTH (METE)

WEIGHT (KN ) 3.70

5.171


42. FINISH

3-41

Design Per Canadian Cold Formed Steel Code Section

3C

3C.1 General Provisions of CSA S136-94, including revisions dated May, 1995, have been implemented. The program allows design of single (non-composite) members in tension, compression, bending, shear, as well as their combinations. For laterally supported members in bending, the Initiation of Yielding method has been used. Cold work of forming strengthening effects have been included as an option.

3C.2 Cross-Sectional Properties The user specifies the geometry of the cross-section by selecting one of the section shape designations from the Gross Section Property Tables published in the "Cold-Formed Steel Design Manual", AISI, 1996 Edition. The Tables are currently available for the following shapes: 

Channel with Lips






Angle with Lips



Angle without Lips



Z with Lips



Z without Lips



Hat

Design Per Canadian Cold Fomed Steel Code

3-42 Section 3C

Shape selection may be done using the member property pages of the graphical user interface (GUI) or by specifying the section designation symbol in the input file. The properties listed in the tables are gross section properties. STAAD.Pro uses unreduced section properties in the structure analysis stage. Both unreduced and effective section properties are used in the design stage, as applicable.

3C.3 Design Procedure The following two design modes are available: 1.

Code Checking The program compares the resistance of members with the applied load effects, in accordance with CSA 136. Code checking is carried out for locations specified by the user via the SECTION command or the BEAM parameter. The results are presented in a form of a PASS/FAIL identifier and a RATIO of load effect to resistance for each member checked. The user may choose the degree of detail in the output data by setting the TRACK parameter.

2.

Member Selection The user may request that the program search the cold formed steel shapes database (AISI standard sections) for alternative members that pass the code check and meet the least weight criterion. In addition, a minimum and/or maximum acceptable depth of the member may be specified. The program will then evaluate all database sections of the type initially specified (i.e., channel, angle, etc.) and, if a suitable replacement is found, present design results for that section. If no section satisfying the d epth restrictions or lighter than the initial one can be found, the program leaves the member unchanged, regardless of whether it passes the code check or not.

Section 3C

The program calculates effective section properties in accordance with Clauses 5.6.2.1 through 3 and 5.6.2.6 through 8. Crosssectional properties and overall slenderness of members are checked for compliance with 

Clause 5.3, Maximum Effective Slenderness Ratio for members in Compression



Clause 5.4, Maximum Flat Width Ratios for Elements in Compression



Clause 5.5, Maximum Section Depths.

The program will check member strength in accordance with Clause 6 of the Standard as follows: a.

Resistance factors listed in Clauses 6.2 (a), (b), and (e) are used, as applicable.

b.

Members in tension Resistance is calculated in accordance with Clauses 6.3.1 and 6.3.2.

c.

Members in bending and shear Resistance calculations are based on Clauses: a. 6.4.1 General, b. 6.4.2 and 6.4.2.1 Laterally Supported Members, compressive limit stress based on Initiation of Yielding, c. 6.4.3 Laterally Unsupported Members, d. 6.4.4 Channels and Z-Shaped Members with Unstiffened Flanges - additional limitations, e. 6.4.5 Shear in Webs, f. 6.4.6 Combined Bending and Shear in Webs.

3-43


3-44 Section 3C

a.

Members in compression Resistance calculations are based on Clauses: a. 6.6.1.1, 6.6.1.2 (a) and (d), and 6.6.1.3 General, b. 6.6.2 Sections Not Subject to Torsional -Flexural Buckling, c. 6.6.3 Singly Symmetric Sections, d. 6.6.4 Point-Symmetric Sections, e. 6.6.5 Cylindrical Tubular Sections.

b.

Members in compression and bending Resistance calculations are based on Clause 6.7.1, Singly and Doubly Symmetric Sections. Input for the coefficients of uniform bending must be provided by the user. The following table contains the input parameters for specifying values of design variables and selection of design options.

CANADIAN COLD FORMED STEEL DESIGN PARAMETERS Parameter Name BEAM

Default Value 1.0

Description When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details). If neither the BEAM parameter nor any SECTION command is specified, STAAD will terminate the run and ask the user to provide one of those 2 commands. This rule is not enforced for TRUSS members.

Section 3C

CANADIAN COLD FORMED STEEL DESIGN PARAMETERS Default Value

Description

CMZ

1.0

Coefficient of equivalent uniform bending z. See CSA 136, 6.7.2. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CMY

0.0

Coefficient of equivalent uniform bending y. See CSA 136, 6.7.2. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CWY

0

Parameter Name

Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See CSA 136, 5.2. Values: 0 – effect should not be included 1 – effect should be included

DMAX

1000.0

DMIN

0.0

Minimum depth required for the section during member selection. This value must be provided in the current units.

1

Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See CSA 136, 6.6.2

FLX

Maximum depth permissible for the section during member selection. This value must be provided in the current units.

Values: 0 – Section subject to torsional flexural buckling and restraint not provided 1 – restraint provided or unnecessary FU

450 MPa


FYLD

350 MPa

Yield strength of steel in current units.

3-45


3-46 Section 3C CANADIAN COLD FORMED STEEL DESIGN PARAMETERS Default Value

Description

KT

1.0

Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

KY

1.0

Effective length factor for overall column buckling about the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

KZ

1.0

Effective length factor for overall column buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

LT

Member length

Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

LY

Member length

Effective length for overall column buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

Parameter Name

Section 3C

CANADIAN COLD FORMED STEEL DESIGN PARAMETERS Default Value

Description

Member length

Effective length for overall column buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

1.0

Net section factor for tension members, See CSA 136, 6.3.1.

STIFF

Member length

Spacing in the longitudinal direction of shear stiffeners for stiffened flat webs. It is input in the current units of length. See section CSA 136, 6.4.5

TRACK

0

This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are:

Parameter Name LZ

NSF

0 - Prints only the member number, section name, ratio, and PASS/FAIL status. 1 - Prints the design summary in addition to that printed by TRACK 1 2 - Prints member and material properties in addition to that printed by TRACK 2. TSA

1

Specifies whether bearing and intermediate transverse stiffeners satisfy the requirements of CSA 136, 6.5. If true, the program uses the more liberal set of interaction equations in 6.4.6. Values: 0 – stiffeners do not comply with 6.5 1 – stiffeners comply with 6.5

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

3-47


3-48 Section 3C

3-49

Wood Design Per CSA Standard CAN/CSA-086-01 Section

3D

3D.1 General Comments The Canadian Wood Design facility in STAAD is based on CSA086-01. A timber section library consisting of Sawn and Glulam timber is available for member property specification. The design philosophy of this specification is based on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit-state are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for the entire structure under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, the code checking portion of the program checks whether code requirements for each selected section are met and identifies the governing criteria. The following sections describe the salient features of the STAAD implementation of CSA086-01. A detailed description of the design process along with its underlying concepts and assumptions is available in the specification document. Analysis Methodology Member Property Specifications Built-in Section Library Member Resistances

Design Per Canadian Timber Code

3-50 Section 3D

Design Parameters Code Checking Member Selection Tabulated Results of Timber Design Verification Examples

3D.2 Analysis Methodology Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and using appropriate load factors to create necessary loading situations.

3D.3 Member Property Specifications For specification of member properties, for Sawn timber the timber section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in timber table. For Glulam timber, member properties can be specified using the YD(depth) and ZD(width) specifications and selecting Combination and Species specifications from the built -in table. The assignment is done with the help of the PRISMATIC option which is explained in STAAD‟s Technical Reference Manual.

3D.4 Built-in Section Library The following information is provided for use when the built -in timber tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for m ember design.

Section 3D

3-51

Following are the description of the different types of species combination available: Douglas Fir-Larch The following example illustrates the specification of Douglas Fir Larch species combination.

100 TO 150 TABLE ST DFL_SelStr_2X2_BM

DFL_SelStr_2X2_BM Species Combination Grade

Size classification Nominal size

Hem-Fir Designation of Hem-Fir species combination in STAAD is as follows.

100 TO 150 TABLE ST Hem-Fir_SelStr_2X10_BM Northern Species Designation of Northern species combination in STAAD is as follows.

100 TO 150 TABLE ST Northern_SelStr_3X12_BM Spruce-Pine-Fir Designation of Spruce-Pine-Fir species combination in STAAD is as follows.

100 TO 150 TABLE ST SPF_SelStr_3X8_BM


3-52 Section 3D

Glu Laminated timber Designation of Glu-lam timber in STAAD involves defining the material, specifying the dimensions, and associating the material with the member through the CONSTANTS command.

UNIT CM KN DEFINE MATERIAL START ISOTROPIC GLT_D.Fir-L-24f-EX E 51611.7 POISSON 0.15 DENSITY 2.5e-005 ALPHA 1.2e-011 END DEFINE MATERIAL MEMBER PROPERTY TIMBER CANADIAN 1 PRIS YD 12 ZD 6 CONSTANTS MATERIAL GLT_D.Fir-L-24f-EX MEMB 1 GLT_D.Fir-L-24f-EX

Timber type Species

Grade

Section 3D

Sample input file to demonstrate usage of Canadian timber STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER UNIT FEET POUND JOINT COORDINATES 1 0 0 0; 2 6 0 0; 3 12 0 0; 4 18 0 0; 5 24 0 0; 6 6 3 0; 7 12 6 0; 8 18 3 0; MEMBER INCIDENCES 1 1 2; 2 2 3; 3 3 4; 4 4 5; 5 1 6; 6 6 7; 7 7 8; 8 8 5; 9 2 6; 10 3 7; 11 4 8; 12 6 3; 13 3 8; UNIT FEET POUND DEFINE MATERIAL START ISOTROPIC SPF_SelStr_4X10_BM E 1224 POISSON 0.15 DENSITY 25 ALPHA 5.5e-006 END DEFINE MATERIAL MEMBER PROPERTY tim can 1 TO 4 9 TO 11 TABLE ST SPF_SelStr_4X10_BM 5 TO 8 12 13 TABLE ST SPF_SelStr_4X10_BM CONSTANTS MATERIAL SPF_SelStr_4X10_BM memb 1 TO 4 9 TO 11 MATERIAL SPF_SelStr_4X10_BM memb 5 TO 8 12 13 PRINT MEMBER PROPERTIES FINISH

3-53


3-54 Section 3D

3D.5 Member Resistance The member resistances are calculated in STAAD according to the procedures outlined in section 5 (for sawn lumber) and 6(for Glulam) of CSA086-01. These depend on several adjustment factors as fol lows 1. KD = Load duration factor (Clause 4.3.2.2-CSA086-01, Table 4.3.2.2) 2. KH = System factor (Clause 5.4.4 and 6.4.3 and Table 5.4.4 -CSA086-01) 3. K_T = Treatment factor (Clause 5.4.3 and 6.4.4 -CSA08601) 4. KSB = Service condition factor applicable to Bending at extreme fibre (Table 5.4.2 and 6.4.2 -CSA086-01) 5. KSV = Service condition factor applicable to longitudinal shear (Table 5.4.2 and 6.4.2 CSA086-01) 6. KSC = Service condition factor applicable to Compression parallel to the grain (Table 5.4.2 and 6.4.2 CSA086-01) 7. K_SCP = Service condition factor applicable to Compression perpendicular to the grain (Table 5.4.2 and 6.4.2 CSA086 -01) 8. KSE = Service condition factor applicable to modulus of elasticity (Table 5.4.2 and 6.4.2 CSA086-01) 9. KST = Service condition factor applicable to tension parallel to the grain (Table 5.4.2 and 6.4.2 CSA086-01) 10. KZB = Size factor applicable to bending (Clause 5.4.5 and Table 5.4.5 -CSA086-01) 11. KZV = size factor applicable to shear(Clause 5.4.5 and Table 5.4.5 -CSA086-01) 12. KZT = size factor applicable to tension parallel to grain (Clause 5.4.5 and Table 5.4.5 -CSA086-01) 13. KZCP = size factor applicable to compression perpendicular to grain (Clause 5.4.5 and Table 5.4.5 -CSA086-01) 14. K_ZC = size factor applicable to compression parallel to grain (Clause 5.4.5 and Table 5.4.5 -CSA086-01) 15. CHIX = Curvature factor (Clause 6.5.6.5.2-CSA086-01)

Section 3D

16. CV = shear load coefficient (Table 6.5.7.4A- CSA086-01) 17. KN = Notch factor(Clause 5.5.5.4-CSA086-01) The user has to give all these factors a s input according to the classification of timber and stress grade. Explained here is the procedure adopted in STAAD for calculating the member resistances. Axial Tension i.

For Sawn timber The criterion governing the capacity of tension members is based on one limit state. The limit state involves fracture at the section with the minimum effective net area. The net section area may be specified by the user through the use of the parameter NSF (see Table 3B.1). STAAD calculates the tension capacity of a member based on this limit state per Clause 5.5.9 of CSA086-01.

ii.

For Glulam timber The design of glulam tension members differs from sawn timber since CSA 086-01 assigns different specified strength for gross and net section. The specified strength at net s ection is slightly higher than the strength of the gross section. Therefore, Glulam tension members are designed based on two limit states. The first one is the limit state of yielding in the gross section. The second limit state involves fracture at the section with the minimum effective net area. The net section area may be specified by the user through the use of the parameter NSF (see Table 3B.1). STAAD calculates the tension capacity of a member based on these two limits states per Clause.6.5.11 of CSA086-01.

Axial Compression The compressive resistance of columns is determined based on Clause.5.5.6 and Clause.6.5.8.4 of CSA086-01. The equations presented in this section of the code assume that the compressive

3-55


3-56 Section 3D

resistance is a function of the compressive strength of the gross section (Gross section Area times the Yield Strength) as well as the slenderness factor (Kc). The effective length for the calculation of compression resistance may be provided through the use of the parameters KX, KY, KZ, LX, LY and LZ (see Table 3B.1). Bending The bending resistance of Sawn members are determined based on Clause 5.5.4 of CSA086-01 and for glulam members are determined based on Clause 6.5.6.5 of CSA086-01. The allowable stress in bending is multiplied by Later al stability factor, KL to take in account whether lateral support is provided at points of bearing to prevent lateral displacement and rotation Axial compression and bending The member strength for sections subjected to axial compression and uni-axial or biaxial bending is obtained through the use of interaction equations. Clause 5.5.10 and 6.5.12 of the code provides the equations for this purpose. If the summation of the left hand side of these equations exceeds 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the member is considered to have FAILed under the loading condition. Axial tension and bending The member strength for sections subjected to axial tension and uniaxial or biaxial bending is obtained through the use of interaction equations. Clause 5.5.10 and 6.5.12 of the code provides the equations for this purpose. If the summation of the left hand side of these equations exceeds 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the member is considered to have FAILed under the loading condition.

Section 3D

Shear The shear resistance of the cross section is determined using the equations of Clause 5.5.5 and 6.5.7.2 of the code. Once this is obtained, the ratio of the shear force acting on the cross section to the shear resistance of the section is calculated. If any of the ratios (for both local Y & Z axes) exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the section is considered to have failed under shear.

3D.6 Design Parameters The design parameters outlined in Table below may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program and thus allows the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Canadian Timber design parameters Parameter Name Nsf KX KY KZ LX

Default Value

Description

1.0 1.0 1.0 1.0 Member length

Net section factor for tension members K value for flexural torsional buckling K value in local Y-axis, usually minor axis K value in local Z-axis, usually major axis Length for flexural torsional buckling

3-57


3-58 Section 3D

Canadian Timber design parameters Parameter Name LY LZ

Default Value

Description

Member length Member length

Length in local Y axis for slenderness value KL/r Length in local Z axis for slenderness value KL/r Load Duration Factor [Clause.4.3.2, Table 4.3.2] System Factor [Clause 5.4.4/6.4.3, Table 5.4.4] Treatment Factor [Clause 5.4.3/6.4.4] Service Condition Factor for Bending at Extreme Fibre Applicable for bending at extreme fibre [Table 5.4.2 and 6.4.2] Service Condition Factor for Shear, Applicable for longitudinal shear [Table 5.4.2 and 6.4.2] Service Condition Factor for Compression, Applicable for compression parallel to grain [Table 5.4.2 and 6.4.2] Service Condition Factor for Modulus of Elasticity, Applicable for modulus of elasticity [Table 5.4.2 and 6.4.2] Service Condition Factor for Tension, Applicable for tension parallel to grain [Table 5.4.2 and 6.4.2] Size Factor for Bending, Applicable for bending [Clause.5.4.5 and Table 5.4.5] Size Factor for Shear [Clause 5.4.5 and Table 5.4.5]

KD

1.0

KH

1.0

K_T

1.0

KSB

1.0

KSV

1.0

KSC

1.0

KSE

1.0

KST

1.0

KZB

1.0

KZV

1.0

Section 3D

Canadian Timber design parameters Parameter Name

Default Value

KZT

1.0

KZCP

1.0

K_ZC

1.0

CV KN

1.0 1.0

K_SCP

1.0

CHIX

1.0

RATIO

1.0

Description Size Factor for Tension, Applicable for tension parallel to grain [Clause 5.4.5 and Table 5.4.5] Size Factor for Compression, Applicable for compression perpendicular to grain [Clause .5.4.5 and Table 5.4.5] Size Factor for Compression, Applicable for compression parallel to grain [Clause 5.4.5 and Table 5.4.5] Shear Load Coefficient [Table 6.5.7.4A] Notch Factor [Clause 5.4.7.2.2] Service Condition Factor for Compression, Applicable for compression perpendicular to grain [Clause 5.4.2 and Table 6.4.2] Curvature Factor for Compression [Clause 6.5.6.5.2] Permissible Ratio of Actual to Allowable Value

3D.7 Code Checking The purpose of code checking is to check whether the provided section properties of the members are adequate. The adequacy is checked as per the CSA086-01 requirements. Code checking is done using forces and moments at specified sections of the members. The code checking output labels th e members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start joint) and magnitudes of the governing forces and moments are also printed.

3-59


3-60 Section 3D

PARAMETER CODE TIMBER CAN KD 0.99 ALL KH 0.99 ALL K_T 0.99 ALL KSB 0.99 ALL KSV 0.99 ALL KSC 0.99 ALL KSE 0.99 ALL KST 0.99 ALL KZB 0.99 ALL KZV 0.99 ALL KZT 0.99 ALL KZCP 0.99 ALL K_ZC 0.99 ALL CV 0.99 ALL KN 0.99 ALL K_SCP 0.99 ALL CHIX 0.99 ALL RATIO 0.99 ALL CHECK CODE ALL FINISH

3D.8 Member Selection Member selection based CSA086-2001 is not available.

3D.9 Tabulated Results of Timber Design Results of code checking and member selection are presented in a tabular format. The term CRITICAL COND refers to the section of the CSA086-01 specification, which governed the design.

Section 3D

Pu = Actual Load in Compression Tu = Actual Load in Tension Muy = Ultimate moment in y direction Muz = Ultimate moment in z direction V = Ultimate shear force SLENDERNESS_Y = Actual Slenderness ratio in y direction SLENDERNESS_Z = Actual Slenderness ratio in z direction PY = Factored Compressive capacity in y direction PZ = Factored Compressive capacity in z direction T = Factored tensile capacity MY = Factored moment of resistance in y direction MZ = Factored moment of resistance in z direction V = Factored shear resistance SLENDERNESS = Allowable slenderness ratio

3D.10 Verification Problems In the next few pages are included 6 verification examples for reference purposes.

3-61


3-62 Section 3D

Verification Problem: 1 Objective: - To determine the Canadian Glulam section column in axial compression. Column is effectively pinned at both ends and braced at mid-height in all direction.. Design Code: - Canadian wood design code (CSA:086-01) Reference: - Example 4, page 116, Canadian Wood Design Manual, 2001 Given: - Length = 9000mm Comparison: Solution Theory STAAD Difference

Design Strength (kN) 295 293.739 -0.427 %

Input: STAAD PLANE EXAMPLE FOR GLULAM DESIGN INPUT FILE: GLULAMCOLUMN.STD START JOB INFORMATION ENGINEER DATE 10-JUN-05 END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 0 9 0; MEMBER INCIDENCES 1 1 2; UNIT INCHES KIP DEFINE MATERIAL START ISOTROPIC GLT_SPRUCE-PINE-12C-E E 9.7 POISSON 0.15 DENSITY 1.44676e-005 ALPHA 5.5e-006 END DEFINE MATERIAL UNIT FEET POUND

Section 3D MEMBER PROPERTY TIMBER CANADIAN 1 PRIS YD 0.748031 ZD 0.574147 UNIT INCHES KIP CONSTANTS MATERIAL GLT_SPRUCE-PINE-12C-E MEMB 1 SUPPORTS 1 PINNED UNIT METER KN LOAD 1 LOADTYPE None TITLE LOAD CASE 1 JOINT LOAD 2 FY -214 PERFORM ANALYSIS PARAMETER CODE TIMBER CANADIAN KY 0.5 ALL KZ 0.5 ALL CHECK CODE ALL FINISH

Relevant portion of Output:-

ALL UNITS ARE - KN MEMBER

STAAD.Pro CODE CHECKING - (S086) *********************** METE (UNLESS OTHERWISE NOTED)

TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1 175.00X228.00 CANADIAN GLULAM GRADE:GLT_SPRUCE-PINE-12C-E PASS CL.5.5.10/6.5 0.728 1 214.00 C 0.00 0.00 0.0000 |--------------------------------------------------------------------------| | LEZ = 4500.000 LEY = 4500.000 LUZ = 9000.000 LUY = 9000.000mm | | | | KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 | | KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 | | KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.000 CHIX = 1.000 | | CV = 1.000 KN = 1.000 | | | | ACTUAL LOADS : (KN-m) | | Pu = 214.000 | | Tu = 0.000 | | Muy = 0.000 | | Muz = 0.000 | | V = 0.000 | | SLENDERNESS_Y = 19.737 | | SLENDERNESS_Z = 25.714 | | ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) | | PY = 413.943 | | PZ = 293.793 | | T = 0.000 | | MY = 0.000 | | MZ = 0.000 | | V = 0.000 | | SLENDERNESS = 50.000 | |--------------------------------------------------------------------------| 37. FINISH

3-63


3-64 Section 3D

Verification Problem: 2 Objective: - To determine the bending capacity of a Canadian Glulam section single span floor beam. The compression edge assumed fully supported. Design Code: - Canadian wood design code (CSA:086-01) Reference: - Example 2, page 59, Canadian Wood Design Manual, 2001 Given: - Length =7500mm, Beam Spacing = 5000mm, Standard load condition, Dry service condition, Untreated Comparison: Solution

Theory STAAD Difference

Design Strength in bending (kNm) 208 208.323 0.155 %

Design Strength in shear (kN) 101 100.776 -0.221 %

Input: STAAD PLANE EXAMPLE FOR GLULAM DESIGN INPUT FILE: glulamBEAM.STD START JOB INFORMATION ENGINEER DATE 10-JUN-05 END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 7.5 0 0 MEMBER INCIDENCES 112 UNIT INCHES KIP

Section 3D

DEFINE MATERIAL START ISOTROPIC GLT_SPRUCE-PINE-12C-E E 9.7 POISSON 0.15 DENSITY 1.44676E-005 ALPHA 5.5E-006 ISOTROPIC GLT_D.FIR-L-20F-E E 12.4 POISSON 0.15 DENSITY 1.44676E-005 ALPHA 5.5E-006 ISOTROPIC CONCRETE E 3150 POISSON 0.17 DENSITY 8.68E-005 ALPHA 5.5E-006 DAMP 0.05 END DEFINE MATERIAL UNIT FEET POUND MEMBER PROPERTY TIMBER CANADIAN 1 PRIS YD 2.11942 ZD 0.426508 UNIT INCHES KIP CONSTANTS MATERIAL GLT_D.FIR-L-20F-E MEMB 1 SUPPORTS 1 2 PINNED UNIT METER KN LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 MEMBER LOAD 1 UNI GY -27.1 PERFORM ANALYSIS PARAMETER CODE TIMBER CANADIAN CHECK CODE ALL FINISH

3-65


3-66 Section 3D

Relevant portion of Output:-

STAAD.Pro CODE CHECKING - (S086) *********************** ALL UNITS ARE - KN MEMBER

METE (UNLESS OTHERWISE NOTED)

RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1

TABLE

130.00X646.00 CANADIAN GLULAM GRADE:GLT_D.FIR-L-20F-E FAIL CL.5.5.5/6.5. 1.008 1 0.00 T 0.00 0.00 0.0000

|--------------------------------------------------------------------------| | LEZ = 7500.000 LEY = 7500.000 LUZ = 7500.000 LUY = 7500.000mm | | | | KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 | | KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 | | KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.000 CHIX = 1.000 | | CV = 1.000 KN = 1.000 | | | | ACTUAL LOADS : (KN-m) | | Pu = 0.000 | | Tu = 0.000 | | Muy = 0.000 | | Muz = 0.000 | | V = 101.625 | | SLENDERNESS_Y = 16.932 | | SLENDERNESS_Z = 1.529 | | ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) | | PY = 0.000 | | PZ = 0.000 | | T = 0.000 | | MY = 41.923 | | MZ = 208.323 | | V = 100.776 | | SLENDERNESS = 50.000 | |--------------------------------------------------------------------------| 46. FINISH

Section 3D

Verification Problem: 3 Objective: - To determine the capacity of a Canadian Glulam section in axial tension. Design Code: - Canadian wood design code (CSA:086-01) Reference: - Example 3, page 158, Canadian Wood Design Manual, 2001 Given: - Dry service condition, Untreated Comparison: Solution Theory STAAD Difference

Design Strength in Tension (kN) 257 256.636 -0.141 %

Input: STAAD PLANE EXAMPLE FOR GLULAM DESIGN INPUT FILE: glulamTENSION.STD START JOB INFORMATION ENGINEER DATE 10-JUN-05 END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 0 9 0 MEMBER INCIDENCES 112 UNIT INCHES KIP DEFINE MATERIAL START ISOTROPIC GLT_SPRUCE-PINE-14T-E E 10.7 POISSON 0.15 DENSITY 1.44676E-005

3-67


3-68 Section 3D

ALPHA 5.5E-006 ISOTROPIC CONCRETE E 3150 POISSON 0.17 DENSITY 8.68E-005 ALPHA 5.5E-006 DAMP 0.05 END DEFINE MATERIAL UNIT FEET POUND MEMBER PROPERTY TIMBER CANADIAN 1 PRIS YD 0.872702 ZD 0.262467 UNIT INCHES KIP CONSTANTS MATERIAL GLT_SPRUCE-PINE-14T-E MEMB 1 SUPPORTS 1 PINNED UNIT METER KN LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 JOINT LOAD 2 FY 250 PERFORM ANALYSIS PRINT STATICS CHECK PARAMETER CODE TIMBER CANADIAN KY 0.5 ALL KZ 0.5 ALL CHECK CODE ALL FINISH

Section 3D

Relevant portion of Output:STAAD.Pro CODE CHECKING - (S086) *********************** ALL UNITS ARE - KN


MEMBER

TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1

80.00X266.00 CANADIAN GLULAM GRADE:GLT_SPRUCE-PINE-14T-E PASS CL.5.5.10/6.5 0.974 1 250.00 T 0.00 0.00 0.0000

|--------------------------------------------------------------------------| | LEZ = 4500.000 LEY = 4500.000 LUZ = 9000.000 LUY = 9000.000mm | | | | KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 | | KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 | | KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.000 CHIX = 1.000 | | CV = 1.000 KN = 1.000 | | | | ACTUAL LOADS : (KN-m) | | Pu = 0.000 | | Tu = -250.000 | | Muy = 0.000 | | Muz = 0.000 | | V = 0.000 | | ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) | | PY = 0.000 | | PZ = 0.000 | | T = 256.636 | | MY = 0.000 | | MZ = 0.000 | | V = 0.000 | |--------------------------------------------------------------------------|

3-69


3-70 Section 3D

Verification Problem: 4 Objective: - To determine the Canadian Sawn section column in axial compression. Column is effectively pinned at both ends. Design Code: - Canadian wood design code (CSA:086-01) Reference: - Example 2, page 113, Canadian Wood Design Manual, 2001 Given: - Unbraced Length = 5000mm Comparison: Solution Theory STAAD Difference

Design Strength (kN) 130 129.223 -0.597 %

Input: STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER INPUT FILE: sawn_ lumber_ COLUMN.STD START JOB INFORMATION ENGINEER DATE 08-JUN-05 END JOB INFORMATION UNIT FEET POUND JOINT COORDINATES 1 0 0 0; 2 0 16.4042 0 MEMBER INCIDENCES 112 DEFINE MATERIAL START ISOTROPIC DFL_NO2_8X8_POST E 1.368E+006 POISSON 0.15 DENSITY 25 ALPHA 5.5E-006 END DEFINE MATERIAL UNIT METER KN CONSTANTS

Section 3D

MATERIAL DFL_NO2_8X8_POST MEMB 1 UNIT FEET POUND MEMBER PROPERTY TIMBER CANADIAN 1 TABLE ST DFL_NO2_8X8_POST SUPPORTS 1 PINNED UNIT METER KN LOAD 1 DEAD+LIVE LOAD JOINT LOAD 2 FY -114 PERFORM ANALYSIS PRINT STATICS CHECK PARAMETER CODE TIMBER CANADIAN KSC 0.91 ALL K_ZC 1.05 ALL CHECK CODE FINISH

Relevant portion of Output:STAAD.Pro CODE CHECKING - (S086) *********************** ALL UNITS ARE - KN MEMBER


TABLE

RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1 ST DFL_NO2_8X8_POST PASS CL.5.5.10/6.5.12 0.882 1 114.00 C 0.00 0.00 0.0000 |--------------------------------------------------------------------------| | LEZ = 5000.000 LEY = 5000.000 LUZ = 5000.000 LUY = 5000.000mm | | | | KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 | | KSC = 0.910 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 | | KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.050 CHIX = 1.000 | | CV = 1.000 KN = 1.000 | | | | ACTUAL LOADS : (KN-m) | | Pu = 114.000 | | Tu = 0.000 | | Muy = 0.000 | | Muz = 0.000 | | V = 0.000 | | SLENDERNESS_Y = 26.178 | | SLENDERNESS_Z = 26.178 | | ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) | | PY = 129.223 | | PZ = 129.223 | | T = 0.000 | | MY = 0.000 | | MZ = 0.000 | | V = 0.000 | | SLENDERNESS = 50.000 | |--------------------------------------------------------------------------|

3-71


3-72 Section 3D

Verification Problem: 5 Objective: - To determine the bending capacity of a Canadian sawn section single span floor beam. Design Code: - Canadian wood design code (CSA:086-01) Reference: - Example 1, page 58, Canadian Wood Design Manual, 2001 Given: - Length =6000mm, Beam Spacing = 3000mm, Standard load condition, Dry service condition, Untreated Comparison: Solution Theory STAAD Difference

Design Strength in bending (kN-m) 79.8 79.732 -0.085 %

Design Strength in shear (kN) 46.1 46.170 No

Input: STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER: SAWN_LUMBER_BEAM.STD START JOB INFORMATION ENGINEER DATE 08-JUN-05 END JOB INFORMATION UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 6 0 0; 3 3 0 0; MEMBER INCIDENCES 1 1 3; 2 3 2; UNIT FEET POUND DEFINE MATERIAL START ISOTROPIC DFL_NO1_10X16_BM E 1.728e+006 POISSON 0.15 DENSITY 25 ALPHA 5.5e-006 END DEFINE MATERIAL UNIT METER KN CONSTANTS

Section 3D

MATERIAL DFL_NO1_10X16_BM MEMB 1 2 UNIT FEET POUND MEMBER PROPERTY TIMBER CANADIAN 1 2 TABLE ST DFL_NO1_10X16_BM SUPPORTS 1 2 FIXED UNIT METER KN LOAD 1 DEAD+LIVE LOAD MEMBER LOAD 1 2 UNI GY -16.4 PERFORM ANALYSIS PARAMETER CODE TIMBER CANADIAN KD 1.0 ALL K_T 1.0 ALL KSB 1.0 ALL KZB 0.90 ALL KZV 0.90 ALL K_ZC 1.05 ALL CHECK CODE ALL FINISH Relevant portion of Output:ALL UNITS ARE - KN MEMBER

TABLE


RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 2 ST DFL_NO1_10X16_BM FAIL CL.5.5.5/6.5.6 1.066 1 0.00 T 0.00 49.20 3.0000 |--------------------------------------------------------------------------| | LEZ = 3000.000 LEY = 3000.000 LUZ = 3000.000 LUY = 3000.000mm | | | | KD = 1.000 KH = 1.000 KT = 1.000 KSB = 1.000 KSV = 1.000 | | KSC = 1.000 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 0.900 | | KZV = 0.900 KZT = 1.000 KZCP = 1.000 K_ZC = 1.050 CHIX = 1.000 | | CV = 1.000 KN = 1.000 | | | | ACTUAL LOADS : (KN-m) | | Pu = 0.000 | | Tu = 0.000 | | Muy = 0.000 | | Muz = 49.200 | | V = -49.200 | | SLENDERNESS_Y = 4.511 | | SLENDERNESS_Z = 2.158 | | ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) | | PY = 0.000 | | PZ = 0.000 | | T = 0.000 | | MY = 79.800 | | MZ = 79.732 | | V = 46.170 | | SLENDERNESS = 50.000 | |--------------------------------------------------------------------------|

3-73


3-74 Section 3D

Verification Problem: 6 Objective: - To determine the capacity of a Canadian Sawn section in axial tension. Design Code: - Canadian wood design code (CSA:086-01) Reference: - Example 2, page 158, Canadian Wood Design Manual, 2001 Given: - Dry service condition, Untreated Comparison: Solution Theory STAAD Difference

Design Strength in Tension (kN) 185 184.338 -0.357%

Input: STAAD PLANE EXAMPLE FOR DIMENSIONAL LUMBER SAWN_LUMBER_TENSION.STD START JOB INFORMATION ENGINEER DATE 08-JUN-05 END JOB INFORMATION UNIT FEET POUND JOINT COORDINATES 1 0 0 0; 2 0 16.4042 0; MEMBER INCIDENCES 1 1 2; DEFINE MATERIAL START ISOTROPIC DFL_NO1_6X8_BM E 1.728e+006 POISSON 0.15 DENSITY 25 ALPHA 5.5e-006 END DEFINE MATERIAL UNIT METER KN CONSTANTS MATERIAL DFL_NO1_6X8_BM MEMB 1

Section 3D

UNIT FEET POUND MEMBER PROPERTY TIMBER CANADIAN 1 TABLE ST DFL_NO1_6X8_BM SUPPORTS 1 PINNED UNIT METER KN LOAD 1 DEAD+LIVE LOAD JOINT LOAD 2 FY 144 PERFORM ANALYSIS PRINT STATICS CHECK PARAMETER CODE TIMBER CANADIAN KH 1.1 ALL KSC 0.91 ALL K_ZC 1.05 ALL CHECK CODE ALL FINISH Relevant portion of Output:STAAD.Pro CODE CHECKING - (S086) ***********************

ALL UNITS ARE - KN


MEMBER

TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= 1 ST DFL_NO1_6X8_BM PASS 144.00 T

CL.5.5.10/6.5.12 0.00

0.781 0.00 0.0000

1

|--------------------------------------------------------------------------| | LEZ = 5000.000 LEY = 5000.000 LUZ = 5000.000 LUY = 5000.000mm | | | | KD = 1.000 KH = 1.100 KT = 1.000 KSB = 1.000 KSV = 1.000 | | KSC = 0.910 K_SCP = 1.000 KSE = 1.000 KST = 1.000 KZB = 1.000 | | KZV = 1.000 KZT = 1.000 KZCP = 1.000 K_ZC = 1.050 CHIX = 1.000 | | CV = 1.000 KN = 1.000 | | | | ACTUAL LOADS : (KN-m) | | Pu = 0.000 | | Tu = -144.000 | | Muy = 0.000 | | Muz = 0.000 | | V = 0.000 | | ALLOWABLE CAPACITIES OF THE SECTION: (KN-m) | | PY = 0.000 | | PZ = 0.000 | | T = 184.338 | | MY = 0.000 | | MZ = 0.000 | | V = 0.000 | |--------------------------------------------------------------------------|

3-75


3-76 Section 3D

Section 4

Chinese Codes

Kjahds;akh

4-1

Concrete Design Per GB50010-2002

Section

4A

4A.1 Design Operations STAAD has the capabilities for performing concrete design per GB50010-2002. It can calculate the reinforcement needed for sections assigned through the PRISMATIC attribute. The concrete design calculations are based on the limit state method of GB50010-2002.


Prismatic (Rectangular, Square, Tee and Trapezoidal)

For Columns




4-2

Section 4A

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350. 14 TO 16 PRIS YD 400. ZD 750. YB 300. ZB 200 . will be done accordingly. In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350 mm diameter. The third set numbers in the above example represents a T-shape with 750 mm flange width, 200 width, 400 mm overall depth and 100 mm flange depth (See section 6.20.2). The program will determine whether the section is rectangular, flanged or circular and the beam or column design

4A.4 Design Parameters The program contains a number of parameters which are needed to perform design as per GB50010-2002. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 9A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton befor e performing the concrete design. Please note as per GB50010-2002, STAAD supports Characteristic Values of Concrete Strength and Design Value of Strength of Steel Bar only as per Table 4.1.4 and Table 4.2.3-1 respectively.

4A.5 Beam Design Beams are designed for flexure, shear and torsion. If required the effect the axial force may be taken into consideration. For all

Section 4A

these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,.75,.8,.9 and 1). All of these sections are scanned to determine the design force envelopes. Design for Flexure Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections are designed to resist both of these critical sagging and hogging moments. Where ever the rectangular section is inadequate as singly reinforced section, doubly reinforced section is tried. However, presently the flanged section is designed only as singly reinforced section under sagging moment. It may also be noted all flanged sections are automatically designed as rectangular section under hogging moment as the flange of the beam is ineffective under hogging moment. Flexural design of beams are performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account of the changed effective depths of sections calculated on the basis of reinforcement provide after the preliminary design. Final provision of flexural reinforcements is made then. Efforts have been made to meet th e guideline for the reinforcement detailing as per GB50010 -2002 Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the detailer taking into account of other practical considera tion), user has the choice of printing reinforcements provided by STAAD at 11 equally spaced sections from which the final detail drawing can be prepared.

4-3


4-4

Section 4A

Design for Shear Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design are performed at 11 equally spaced sections (0.to 1.) for the maximum shear forces amongst the active load cases and the associated torsional moments. Shear capacity calculation at different sections without the shear reinforcement is based on the actual tensile reinforcement provided by STAAD program. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections. Beam Design Output The default design output of the beam contains flexural and shear reinforcement provided at 5 equally spaced (0,.25,.5,.75 and 1.) sections along the length of the beam. User has option to get a more detail output. All beam design outputs are given in IS units. An example of rectangular beam design output with the default output option (TRACK 0.0) is presented below:

Section 4A

============================================================================ B E A M N O. 12 D E S I G N R E S U L T S C20 LENGTH: 4000.0 mm

HRB400 (Main) SIZE:

HRB400 (Sec.)

250.0 mm X 350.0 mm

COVER: 30.0 mm

DESIGN LOAD SUMMARY (KN MET) ---------------------------------------------------------------------------SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR (in mm) | P MZ MX Load Case | VY MX Load Case ---------------------------------------------------------------------------0.0 | 0.00 0.00 0.00 4 | 29.64 1.23 4 | 0.00 -25.68 1.23 4 | 400.0 | 0.00 0.00 0.00 4 | 27.97 1.23 4 | 0.00 -16.05 1.23 4 | 800.0 | 0.00 0.00 0.00 4 | 25.12 1.23 4 | 0.00 -7.17 1.23 4 | 1200.0 | 0.00 0.97 0.49 5 | 21.11 1.23 4 | 0.00 -0.14 1.32 6 | 1600.0 | 0.00 6.77 1.23 4 | 15.93 1.23 4 | 0.00 0.00 0.00 4 | 2000.0 | 0.00 11.06 1.23 4 | 9.59 1.23 4 | 0.00 0.00 0.00 4 | 2400.0 | 0.00 13.04 1.23 4 | 2.08 1.23 4 | 0.00 0.00 0.00 4 | 2800.0 | 0.00 12.45 1.23 4 | -5.43 1.23 4 | 0.00 0.00 0.00 4 | 3200.0 | 0.00 9.55 1.23 4 | -11.77 1.23 4 | 0.00 0.00 0.00 4 | 3600.0 | 0.00 4.73 1.23 4 | -16.95 1.23 4 | 0.00 0.00 0.00 4 | 4000.0 | 0.00 0.00 0.00 4 | -25.48 1.23 4 | 0.00 -17.36 1.23 4 | ---------------------------------------------------------------------------SUMMARY OF REINF. AREA (Sq.mm) ---------------------------------------------------------------------------SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ---------------------------------------------------------------------------TOP 259.04 161.29 0.00 0.00 176.31 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) BOTTOM 0.00 160.78 160.78 160.78 0.00 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) ---------------------------------------------------------------------------SUMMARY OF PROVIDED REINF. AREA ---------------------------------------------------------------------------SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ---------------------------------------------------------------------------TOP 4-10Ø 3-10Ø 2-10Ø 2-10Ø 3-10Ø REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) BOTTOM REINF.

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

SHEAR 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø REINF. @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c ---------------------------------------------------------------------------============================================================================

4-5


4-6

Section 4A

4A.6 Column Design Columns are designed for axial forces and biaxial moments at the ends. All active load cases are tested to calculate reinforcement. The loading which yield maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. By default, square and rectangular columns and designed with reinforcement distributed on each side equally for the sections under biaxial moments and with reinforcement distributed equally in two faces for sections under uniaxial moment. User may change the default arrangement of the reinforcement with the help of the parameter RFACE (see Table 4A.1). Depending upon the member lengths, section dimensions and effective length coefficients specified by the user STAAD automatically determine the criterion (short or long) of the column design. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by GB50010-2002 have been taken care of in the column design of STAAD. Column Design Output Default column design output (TRACK 0.0) contains the reinforcement provided by STAAD and the capacity of the section. With the option TRACK 1.0, the output contains intermediate results such as the design forces, effective length coefficients, additional moments etc. A special output TRACK 9.0 is introduced to obtain the details of section capacity calculations. All design output is given in SI units. An example of a long column design output (with option TRACK 1.0) is given below.

Section 4A

============================================================================ C O L U M N No. 1 D E S I G N R E S U L T S C20 LENGTH:

3000.0 mm

HRB400 (Main) CROSS SECTION:

** GUIDING LOAD CASE:

5

HRB400 (Sec.)

250.0 mm dia.

COVER: 40.0 mm

BRACED LONG COLUMN

DESIGN FORCES (KNS-MET) ----------------------DESIGN AXIAL FORCE (Pu)

:

62.0

INITIAL MOMENTS MOMENTS DUE TO MINIMUM ECC.

: :

About Z 2.21 1.24

About Y 32.29 1.24

SLENDERNESS RATIOS MOMENTS DUE TO SLENDERNESS EFFECT MOMENT REDUCTION FACTORS ADDITION MOMENTS (Maz and May)

: : : :

12.00 1.12 1.00 1.12

12.00 1.12 1.00 1.12

TOTAL DESIGN MOMENTS

:

3.32

33.40

REQD. STEEL AREA : 1822.71 Sq.mm. MAIN REINFORCEMENT : Provide 17 - 12 dia. (3.92%, 1922.65 Sq.mm.) (Equally distributed) TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c SECTION CAPACITY (KNS-MET) -------------------------Puz : 992.70 Muz1 :

36.87

Muy1 :

36.87

INTERACTION RATIO: 1.00 ============================================================================

4-7


4-8

Section 4A

Table 4A.1 Chinese Concrete Design GB50010-2002 Parameters Parameter Name

Default Value

Description

FYMAIN

210 N/mm2

Yield Stress for main reinforcing steel.

FYSEC

210 N/mm2

Yield Stress for secondary reinforcing steel.

FC

15 N/mm2

Concrete Yield Stress.

CLEAR

25 mm 40 mm

For beam members. For column members

MINMAIN

10 mm


MAXMAIN

60 mm


MINSEC

8 mm


MAXSEC

12 mm


BRACING

0.0

BEAM DESIGN A value of 1.0 means the effect of axial force will be taken into account for beam design. COLUMN DESIGN A value of 1.0 means the column is unbraced about major axis. A value of 2.0 means the column is unbraced about minor axis. A value of 3.0 means the column is unbraced about both axis.

RATIO

4.0


Section 4A

4-9

Table 4A.1 Chinese Concrete Design GB50010-2002 Parameters Parameter Name RFACE

Default Value 4.0

Description A value of 4.0 means longitudinal reinforcement in column is arranged equally along 4 faces. A value of 2.0 invokes 2 faced distribution about major axis. A value of 3.0 invokes 2 faced distribution about minor axis.

WIDTH

ZD


DEPTH

YD


TRACK

0.0

BEAM DESIGN: For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output. COLUMN DESIGN: With TRACK = 0.0, reinforcement details are printed. With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output. With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.

REINF

0.0



4-10

Section 4A

Table 4A.1 Chinese Concrete Design GB50010-2002 Parameters Parameter Name

Default Value

Description

ELZ

1.0

Ratio of effective length to actual length of column about major axis.

ELY

1.0

Ratio of effective length to actual length of column about minor axis.


4-11

Steel Design Per GBJ 50017-2003 Section

4B

4B.1 General This section presents some gen eral statements regarding the implementation in STAAD of the National Standard of the People‟s Republic of China specifications for Design of Steel Structures (GB50017-2003). The design philosophy and procedural logistics are based on the principles of lim it state design method. Facilities are available for member selection as well as code checking. The following sections describe the salient features of the design approach. Members are proportioned to resist the design loads without exceedance of the capacities. The most economical section is selected on the basis of the least weight criteria. The code checking part of the program also checks the slenderness requirements and the stability criteria. It is generally assumed that the user will take care of th e detailing requirements like flange buckling, web crippling etc. Users are recommended to adopt the following steps in performing the steel design: 1. Specify the geometry and factored loads. Perform the analysis. 2. Specify the design parameter values if different from the default values. 3. Specify whether to perform code checking or member selection.

Steel Design Per GBJ 50017-33

4-12

Section 4B

4B.2 Analysis Methodology Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis, P-Delta analysis or Non-linear analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.

4B.3 Member Property Specifications For specification of member properties, the steel section libra ry available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built -in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, r efer to the STAAD Program Technical Reference manual.

4B.4 Built-in Chinese Steel Section Library The following information is provided for use when the built -in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members. An example of the member property specification in an input file is provided at the end of this section. A complete listing of the sections available in the built -in steel section library may be obtained by using the tools of the graphical user interface.

Section 4B

Following are the descriptions of different types of sections. I Shapes I shaped sections are designated in the following way.

1 TO 5 15 16 TABLE ST I22B H Shapes H shaped sections are designated in the following way.

6 TO 8 TABLE ST HW250X250 T Shapes T shaped sections are designated in the following way.

24 25 33 to 36 TABLE ST TM244X300 Channels Channels are specified in the following way.

29 30 TABLE ST CH25A Double Channels Back to back double channels, with or without a spacing between them, are available. The letter D in front of the section name will specify a double channel.

11 TABLE D CH22B 17 TABLE D CH40C SP 0.15

4-13


4-14

Section 4B

In the above set of commands, member 11 is a back to back double channel CH22B with no spacing in between. Member 17 is a double channel CH40C with a spacing of 0.15 length units between the channels. Angles Two types of specifications may be used to describe an angle. The standard angle section is specified as follows:

19 TABLE ST L100X100X7 Two types of specifications may be used to describe an angle. The standard angle section is specified as follows:

27 TABLE RA L40X25X3 The above section signifies an angle with legs of length 40mm and 25mm and a leg thickness of 3 mm. This specification may be used when the local Z axis corresponds to the z -z axis specified in Chapter 2. If the local Y axis corresponds to the z -z axis, type specification "RA" (reverse angle) may be used. Double Angles Short leg back to back or long leg back to back double angles can be specified by means of input of the words SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose.

22 32 20 28

TABLE TABLE TABLE TABLE

LD L56X36X3 SD L45X28X4 LD L56X36X3 SP 0.15 SD L56X36X4 SP 0.15

Section 4B

Tubes (Rectangular or Square Hollow Sections) Tubes can be assigned in 2 ways. In the first method, the designation for the tube is as shown below. This method is meant for tubes whose property name is available in the steel table. In these examples, member 12 consist of a 10X6X0.3 cm size tube section,

12 TABLE ST TUB100603.0 In the second method, tubes are specified by their dimensions. For example,

13 TABLE ST TUBE TH 0.15 WT 0.8 DT 0.6

is a tube that has a height of 0.6 length units, width of 0.6 length units, and a wall thickness of 0.15 length un its. Pipes (Circular Hollow Sections) Pipes can be assigned in 2 ways. In the first method, the designation for the pipe is as shown below. This method is meant for pipes whose property name is available in the steel table.

21 31 TABLE ST PIP203X6.5 In the second method, pipe sections may be provided by specifying the word PIPE followed by the outside and inside diameters of the section. For example,

9 10 14 18 23 26 TABLE ST PIPE OD 0.6 ID 0.55 specifies a pipe with outside diameter of 0.6 length units and inside diameter of .55 length units.

4-15


4-16

Section 4B

Sample File Containing Chinese Shapes

STAAD SPACE START JOB INFORMATION ENGINEER DATE 04-Aug-05 END JOB INFORMATION UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 4 0 0; 3 9 0 0; 4 0 0 4; 5 4 0 4; 6 0 0 8; 7 4 0 8; 8 9 0 8; 9 0 3.5 0; 10 4 3.5 0; 11 9 3.5 0; 12 0 3.5 4; 13 4 3.5 4; 14 0 3.5 8; 15 4 3.5 8; 16 9 3.5 8; 17 0 7 0; 18 4 7 0; 19 9 7 0; 20 0 7 4; 21 4 7 4; 22 0 7 8; 23 4 7 8; 24 9 7 8; MEMBER INCIDENCES 1 1 9; 2 2 10; 3 3 11; 4 4 12; 5 5 13; 6 6 14; 7 7 15; 8 8 16; 9 9 17; 10 10 18; 11 11 19; 12 12 20; 13 13 21; 14 14 22; 15 15 23; 16 16 24; 17 9 10; 18 10 11; 19 12 13; 20 14 15; 21 15 16; 22 17 18; 23 18 19; 24 20 21; 25 22 23; 26 23 24; 27 9 12; 28 12 14; 29 10 13; 30 13 15; 31 11 16; 32 17 20; 33 20 22; 34 18 21; 35 21 23; 36 19 24; MEMBER PROPERTY CHINESE *I SHAPES 1 TO 5 15 16 TABLE ST I22B *H SHAPES 6 TO 8 TABLE ST HW250X250 *T SHAPES 24 25 33 to 36 TABLE ST TM244X300 *CHANNELS 29 30 TABLE ST CH25A *DOUBLE CHANNELS 11 TABLE D CH22B 17 TABLE D CH40C SP 0.15 *ANGLES 19 TABLE ST L100X100X7 *DOUBLE ANGLES 27 TABLE RA L40X25X3 22 TABLE LD L56X36X3 32 TABLE SD L45X28X4 20 TABLE LD L56X36X3 SP 0.15

Section 4B

28 TABLE SD L56X36X4 SP 0.15 *TUBES 12 TABLE ST TUB100603.0 13 TABLE ST TUBE TH 0.15 WT 0.8 DT 0.6 *PIPES 21 31 TABLE ST PIP203X6.5 9 10 14 18 23 26 TABLE ST PIPE OD 0.6 ID 0.55 PRINT MEMBER PROPERTIES FINISH

4B.5 Member Capacities The basic measure of member capacities are the allowable stresses on the member under various conditions of applied loading such as allowable tensile stress, allowable compressive stress etc. These depend on several factors such as cross sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Explained here is the procedure adopted in STAAD for calculating such capacities. Allowable stress for Axial Tension In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of allowable tensile stresses provided in Table 3.4.1-1 of the code. STAAD calculates the tension capacity of a given member per this allowable stress value and a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value, see Table 1) and proceeds with member selection or code checking. Allowable stress for Axial Compression The allowable stress for members in compression is determined according to Table 3.4.1-1. Compressive resistance is a function of the slenderness of the cross-section (Kl/r ratio) and the user may control the slenderness value by modifying parameters such as

4-17


4-18

Section 4B

KY, LY, KZ and LZ. The provisions of Section 5 are used to check the adequacy of sections in compression. Allowable stress for Bending and Shear Sections subjected to bending moments and shear forces are to be designed according to the provisions of section 4. The permissible bending compressive and tensile stresses are dependent on such factors as outstanding legs and thickness of flanges, unsupporte d length of the compression flange (UNL, defaults to member length) etc. Shear capacities are calculated according to Table 3.4.1-1 and Section 4 and are a function of web depth, web thickness etc. Users may use a value of 1.0 or 2.0 for the TRACK parameter to obtain a listing of the bending and shear capacities. Allowable stress for Combined Loading For members experiencing combined loading (axial force, bending and shear), applicable interaction formulas are checked at different locations of the member for all modeled loading situations. The procedure of Section 5 is implemented for combined axial load and bending.

4B.6 Combined Loading For members experiencing combined loading (axial force, bending and shear), applicable interaction formulas are checked at different locations of the member for all modeled loading situations. The procedure of Section 5 is implemented for combined axial load and bending.

4B.7 Design Parameters The user is allowed complete control over the design process through the use of parameters mentioned in Table 4B.1 of this chapter. These parameters communicate design decisions from the engineer to the program.

Section 4B

4-19

The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements of an analysis, some or all of these parameter values may have to be changed to exactly model the physical structure. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 4B.1 Chinese Steel Design Parameters Parameter Reference Definition Name (GB50017-2003) Length in local Y axis for Ly slenderness value KL/r Length in local Z axis for Lz slenderness value KL/r Maximum Dmax allowable depth Minimum Dmin required depth K value in local Ky Y-axis, usually minor axis K value in local Kz Z-axis, usually major axis Net section factor for Nsf tension members

Default Value

Remarks

0

Default is selected beam's length

0

Default is selected beam's length

100 cm

-

0 cm

-

1

-

1

-

1

-

Main

Flag for controlling slenderness check

-

-

Track

Track parameter

-

0

0 = Check for slenderness. 1 = Do not check for slenderness 0 = Suppress critical member stress. 1 = Print all critical member stress. 2 = Print expanded output.


4-20

Section 4B

Table 4B.1 Chinese Steel Design Parameters Parameter Reference Definition Name (GB50017-2003) Permissible ratio of actual Ratio to allowable stress

Beam

Beam parameter

Grade

Grade of steel

Compression Tension

Pfy

Pfz

Allowable KL/r value in compression Allowable KL/r value in tension Plasticity adaptation factor Y direction Plasticity adaptation factor Z direction

Default Value

Remarks

1

0 = Perform design at ends and those locations specified in the section command. 1 = Perform design at ends and 1/12th section locations along member length. The Following values represent the various grades of steel. Q235 - 1 Q345 - 2 Q390 - 3 Q420 - 4

-

1

Clause 3.4.1

1

-

150

-

-

300

-

Table - 5.2.1

1.2

-

Table - 5.2.1

1.05

-

Section 4B

Table 4B.1 Chinese Steel Design Parameters Parameter Reference Definition Name (GB50017-2003)

Default Value

Remarks Stability factor for axial compression members shall be selected from appendix –C based on its slenderness ratio, yield strength, classification of the section in Table 5.1.2-1 and Table 5.1.2-2 Stability factor for axial compression members shall be selected from appendix –C based on its slenderness ratio, yield strength, classification of the section in Table 5.1.2-1 and Table 5.1.2-2

Sfy

Stability factor for Y direction

Appendix-C

1

Sfz

Stability factor for Z direction

Appendix-C

1

Appendix-B

1

-

Appendix-B

0

-

SBY SBZ

Overall Stability factor for Y direction Overall Stability factor for Z direction

4-21

4B.8 Code Checking The purpose of code checking is to check whether the provided section properties of the members are adequate. The adequacy is checked per the GB50017-2003 requirements. Code checking is done using forces an d moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam, and the maximum moment about the major axis is used.


4-22

Section 4B

When no sections are specified and the BEAM parameter is set to zero (default), design will be based on member start and end forces. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from start joint) and magnitudes of the governing forces and moments are also printed.

4B.9 Member Selection The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table.

Sample Input data for Steel Design UNIT METER PARAMETER CODE CHINESE NSF 0.85 ALL GRADE 3.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL

Section 5 European Codes

5-1

Concrete Design Per Eurocode EC2 Section

5A

5A.1 Design Operations STAAD provides a comprehensive set of national codes for the design of concrete structures. In general, all the available codes, including EC2, follow the same procedur e for the design of the concrete members. The main steps in performing a design operation are: 1. 2. 3.

Selecting the applicable load cases to be considered in the design process. Providing appropriate parameter values if different from the default values. Perform the design for the member as appropriate.

These operations can be repeated by the user any number of times depending on the design requirements. The parameters referred to above provide the user with the ability to allocate specific design properties to individual members considered in the design operation.

5A.2 Eurocode 2 (EC2) Eurocode 2, Design of concrete structures, Part 1, General rules and rules for buildings, provides design rules applicable to plain, reinforced or prestressed concrete used in buildings and civil engineering works. It is based on the limit state philosophy common to modern standards.

Concrete Design Per Eurocode EC2

5-2

Section 5A

The objective of this method of design is to ensure that possibility of failure is reduced to a negligible level. This is achieved throu gh application of factors to both the applied loads and the material properties. The code also provides guidelines on the global method of analysis to be used for calculating internal member forces and moments. STAAD provides a number of methods for analys is, allowing Geometric Nonlinearity as well as P-Delta effects to be considered.

5A.3 National Application Documents Various authorities of the CEN member countries have prepared National Application Documents to be used with EC2. These documents provide alternative factors for loads and may also provide supplements to the rules in EC2. The current version of EC2 implemented in STAAD adheres to the factors and rules provided in EC2 and has not been modified by any National Application Documents.

5A.4 Material Properties and Load Factors Design resistances are obtained by dividing the characteristic yield strengths, as given in table 2.3 of EC2, by the material partial safety factors  c for concrete and  s for reinforcements. The magnitude in STAAD is 1.5 for concrete and 1.15 for reinforcements. Material coefficients in STAAD take the following default values unless replaced by user's numerical values provided in the input file. Modulus of Elasticity Shear Modulus Poisson's Ratio Unit weight

E = 21.71 KN/mm 2 G = E / 2 (1 + v) v = 0.25  = 23.56 KN/m 3

Section 5A

The magnitude of design loads is dependent on  F, the partial safety factor for the action under consideration. In STAAD the user is allowed total control in providing applicable values for the factors and their use in various load combinations.

5A.5 Columns Columns are designed for axial compressive loads and possible moments at the ends of the member. If a particular load case causes tension in the column being designed that load case is ignored, the design proceeds with a warning message given to that affect. All active load cases will be considered in the design and reinforcements are assumed symmetrically arranged in the cross section. The maximum reinforcement calculated after all design load cases have been considered is then reported as the critical required area of reinforcement. Slender columns are also covered in the design process, the program will make due allowance for the additional moment that has to be considered in the design. Please note that sway type structures are not directly covered in the current implementation of EC2. This effect, however, can be catered for by the P-DELTA analysis option.

5A.6 Beams Beams are designed for flexure, shear and torsion. For all these actions active load cases are scanned to create appropriate envelopes for the design process. Maximum torsional moment is also identified and incorporated in the design.

5-3


5-4

Section 5A

Design for flexure Reinforcement for both positive and negative moments is calculated on the basis of the section properties provided by the user. If the required reinforcement exceeds the maximum allowable then the section size is inadequate and a massage to that effect is given in the output. Parabolic-rectangular stress distribution for the concrete section is adopted and as moment redistribution is not available in STAAD analysis, the limit for N.A to depth ratio is set according to clause 2.5.3.4.2 (5) of the code. If required, compression reinforcement will be provided in order to satisfy the above limits. It is important to know that beams are designed for the flexural moment MZ only. The moment MY is not considered in the design at all. Design for Shear Shear reinforcement design is based on the standard method mentioned in clause 4.3.2.4.3 where it is assumed the notional strut inclination is constant. Depending on the shear distribution within the member it may be possible that nominal shear reinforcement will be su fficient to cater for the design shear forces. If this is not the case an attempt is made to identify regions where nominal reinforcement is insufficient and appropriate reinforcement is then calculated to cover the excess design shear force. The maximum shear force that can be carried without crushing the concrete is also checked and if exceeded, a message to revise the section size is given in the output file. Design for Torsion Torsional moments arising as a result of equilibrium requirements need to be designed for at the ultimate limit state. Reinforcement for torsional moments consists of stirrups combined with longitudinal bars. The combined magnitude of shear stress arising from shear forces and torsional moments are checked in order to establish whether the section size is adequate. If section size is

Section 5A

inadequate a massage is given in the output file, otherwise, full design is carried out and both shear links and longitudinal bars required are calculated and, where necessary, links are combined with the shear force links and printed in a tabulated manner in the output file.

5A.7 Slabs Slabs can only be designed for if finite elements are used to represent them in the model of the structure. In the main the design follows the same procedure as for flexure except that shear forces are assumed to be resisted without the provision of shear reinforcements. In cases where this may not be the case users must ensure that necessary checks are carried out. The output for the slab design refers to longitudinal reinforcements, which coincides with the local x direction of the element, and, transverse reinforcement, which coincides with the local y direction of the element. Also, reference is made to 'TOP' and BOTT' reinforcement which relates to the element's 'TOP' and 'BOTTOM' as determined from the connectivity of the element. This may not coincide with the slab's actual top and bottom and, if desired, users must ensure this through the numbering scheme of the elements (see figure 1.13 in the STAAD Technical Reference Manual). The design of the slab considers a fixed bar size of 16mm in both directions with the longitudinal bar being the layer closest to the slab exterior faces.

5A.8 Design Parameters Design parameters communicate specific design decisions to the program. They are set to default values to begin with and may be altered to suite the particular structure. Depending on the model being designed, the user may have to change some or all of the parameter default values. Some parameters are unit depend ent and when altered, the new setting must be compatible with the active "unit" specification. Table 5A.1 lists all the relevant EC2 parameters together with description and default values.

5-5


5-6

Section 5A

Note: Once a parameter is specified, its value stays at that speci fied number till it is specified again. This is the way STAAD works for all codes.

Table 5A.1 – Concrete Design Parameters-EC2 Parameter Name

Default Value

Description

FYMAIN

*460 N/mm2

Yield Stress for main reinforcement (For slabs, it is for reinforcement in both directions)

FYSEC

*460N/mm2

Yield Stress for secondary reinforcement. Applicable to shear bars in beams

FC

* 30N/mm

2


MINMAIN

8mm

Minimum main reinforcement bar size Acceptable bar sizes: 6 8 10 12 16 20 25 32 40 50

MINSEC

8mm


CLEAR

* 20mm

Clearance of reinforcement measured from concrete surface to closest bar perimeter.

50mm


SFACE

*0.0

Face of support location at start of beam. (Only applicable for shear - use MEMBER OFFSET for bending )

EFACE

*0.0

Face of support location at end of beam. (NOTE: Both SFACE & EFACE must be positive numbers.)

TRACK

0.0


MMAG

1.0

Factor by which column design moments are magnified

MAXMAIN

Section 5A

5-7

10

Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20.

WIDTH

*ZD


DEPTH

*YD


BRACE

0.0

0.0 = Column braced in both directions. 1.0 = Column unbraced about local Z direction only 2.0 = Column unbraced about local Y direction only 3.0 = Column unbraced in both Y and Z directions

ELY

1.0


ELZ

1.0


SRA

0.0

0.0 =

NSECTION

-500 = A= SERV

0.0

* Provided in current unit system

Orthogonal reinforcement layout without considering torsional moment Mxy -slabs only Orthogonal reinforcement layout with Mxy used to calculate WOOD & ARMER moments for design. Skew angle considered in WOOD & ARMER equations where A is the angle in degrees.

0.0 = No serviceability check performed. 1.0 = Perform serviceability check for beams as if they were continuous. 2.0 = Perform serviceability check for beams as if they were simply supported. 3.0 = Perform serviceability check for beams as if they were cantilever beams.


5-8

Section 5A

5-9

Steel Design Per Eurocode EC3 Section

5B

5B.1 General Description Introduction The design of structural steel members in accordance with the specification Eurocode 3: Design of steel structures – part 1-1: General Rules and rules for buildings has been implemented. Two versions of the code are currently implemented, the EC3_94/1 and BS EN 1993-1-1:2005. To access the EC3_94/1 edition, specify the commands: PARAMETERS CODE EC3 Or PARAMETERS CODE EURO To access the BS EN 1993-1-1:2005 edition, specify the commands: PARAMETERS CODE EC3 BS

Steel Design Per Eurocode EC3

5-10

Section 5B

The main steps in performing a design operation are: 1. Selecting the applicable load cases to be considered in the design process. 2. Providing appropriate parameter values if different from the default values. 3. Specify whether to perform code-checking and/or member selection. These operations can be repeated by the user any number of times depending on the design requirements. The parameters, referred to above, provide the user with the ability to allocate specific design properties to ind ividual members considered in the design operation. Eurocode (EC3) Eurocode 3, Design of steel structures, Part 1.1 General rules and rules for buildings (EC3) provides design rules applicable to structural steel used in buildings and civil engineering works. It is based on the limit states philosophy common to modern standards. The objective of this method of design is to ensure that possibility of failure is reduced to a negligible level. This is achieved through application of factors to both the applied loads and the material properties. The code also provides guidelines on the global method of analysis to be used for calculating internal member forces and moments. STAAD uses the elastic method of analysis which may be used in all cases. Also there are three types of framing referred to in EC3. These are “Simple”, “Continuous”, and “Semi -continuous” which reflect the ability of the joints in developing moments. In STAAD, only “Simple” and “Continuous” joint types can be assumed when carrying out global analysis.

Section 5B

Axes convention in STAAD and EC3 By default, STAAD defines the major axis of the cross -section as zz and the minor axis as yy. A special case where zz is the minor axis and yy is the major axis is available if the “SET Z UP” command is used and is discussed in the Technical Reference Manual. The longitudinal axis of the member is defined as x and joins the start joint of the member to the end with the same positive direction. EC3, however, defines the principal cross-section axes in reverse to that of STAAD, but the longitudinal axis is defined in the same way. Both of these axes definitions follow the orthogonal right hand rule. See figure below. Users must bear this difference in mind when examining the code check output from STAAD.

STAAD Figure 1

EC3 Axes Convention in STAAD and EC3.

National Application Documents Various authorities of the CEN member countries have prepared National Application Documents to be used wi th EC3. These documents provide alternative factors for loads and may also provide supplements to the rules in EC3. The current version of EC3 implemented in STAAD adheres to the factors and rules provided in EC3 and have not been modified by any National Application Documents.

5-11


5-12

Section 5B

Section Classification The occurrence of local buckling of the compression elements of a cross-section prevents the development of full section capacity. It is therefore imperative to establish this possibility prior to determining the section capacities. Cross sections are classified in accordance with their geometrical properties and the stress pattern on the compression elements. For each load case considered in the design process, STAAD determines the section class and calculate s the capacities accordingly. Material Properties and Load Factors Design resistances are obtained by dividing the characteristic yield strength, as given in table 3.1, by the material partial safety factor g m. The magnitude of g m in STAAD is 1.1 which is applicable to all section types. Material coefficients in STAAD take the following default values unless replaced by user‟s numerical values provided in the input file. Modulus of Elasticity Shear Modulus Poisson‟s Ratio Unit weight

E = 205 N/mm 2 G = E / 2 (1+v) v = 0.3 r = 76.8 KN/m 3

The magnitude of design loads is dependent on g f , the partial safety factor for the action under consideration. In STAAD, the user is allowed total control in providing applicabl e values for the factors and their use in various load combinations. Axially Loaded Members For members subject to tension loads only, tension capacity is calculated based on yield strength, material factor g m and crosssectional area of the member with possible reduction due to bolt holes. When bolt holes need to be considered in the capacity calculations, the value used for g m is 1.2 and the yield strength is replaced with the ultimate tensile strength of the material. The

Section 5B

tension capacity is then taken as the smaller of the full section capacity and the reduced one. For members subject to compression only, cross-section resistance as well as buckling resistance must be checked. The latter is often more critical as it is influenced by a number of factors including the section type and member unbraced length. Beams The main requirement for a beam is to have sufficient cross section resistance to the applied bending moment and shear force. Also the possibility of lateral-torsional buckling must be taken into consideration when the full length of the member is not laterally restrained. The bending capacity is primarily a function of the section type and the material yield strength. There are four classes of cross sections defined in EC3. Class 1 and 2 secti ons can both attain full plastic capacity with the exception that the class 2 sections cannot sustain sufficient rotation required for plastic analysis of the model. Class 3 sections, due to local buckling, cannot develop plastic moment capacity and the yield stress is limited to the extreme compression fiber of the section. The elastic section modulus is used to determine the moment capacity. Class 4 sections do suffer from local buckling and explicit allowance must be made for the reduction in section properties before the moment capacity can be determined. Further, because of interaction between shear force and bending moment, the moment resistance of the cross-section may be reduced. This, however, does not occur unless the value of applied shear forces exceeds 50% of the plastic shear capacity of the section. In such cases the web is assumed to resist the applied shear force as well as contributing towards the moment resistance of the cross -section.

5-13


5-14

Section 5B

The plastic shear capacity is calculated using the a ppropriate shear fy area for the section and the yield strength in shear, taken as . 3 As mentioned earlier, lateral-torsional buckling must also be considered whenever the full length of the member is not laterally restrained. The buckling capacity is dependent on the section type as well as the unrestrained length, restraint conditions and type of applied loading. Axially Loaded Members With Moments The bending resistance of members subject to coexistent axial load is reduced by the presence of the axial load. The presence of large shear, as mentioned above, can also reduce the bending resistance of the section under consideration. If the shear load is large enough to cause a reduction in bending resistance, then the reduction due to sh ear has to be taken into account before calculating the effect of the axial load on the bending resistance of the section. Generally, EC3 requires checking cross-section resistance for local capacity and also checking the overall buckling capacity of the member. In the case of members subject to axial tension and bending, there is provision to take the stabilizing effect of the tension load into consideration. This is achieved by modifying the extreme compression fiber stress and calculating an effective applied moment for the section. This is then checked against the lateral-torsional buckling resistance of the section.

5B.2 Design Parameters Introduction Design parameters communicate specific design decisions to the program. They are set to default values to begin with and may be altered to suite the particular structure.

Section 5B

5-15

Depending on the model being designed, the user may have to change some or all of the parameter default values. Some parameters are unit dependent and when altered, the new setting must be compatible with the active “unit” specification. Table 5B.1 lists all the relevant EC3 parameters together with description and default values. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 5B.1 – Steel Design Parameters EC3 Parameter Name

Default

Definition

Value

KY

1.0

K factor in local y axis.

KZ

1.0

K factor in local z axis.

LY

Member Length

LZ

Member Length

UNL

Member Length

Compression length in local y axis, Slenderness ratio = (KY)*(LY)/(Ryy) Compression length in local z axis, Slenderness ratio = (KZ)*(LZ)/(Rzz)

PY

Yield Strength

Unrestraint length of member used in calculating the lateral-torsional resistance moment of the member. The yield strength default value is set based on the default value of the “SGR” parameter.

NSF

1.0

Net tension factor for tension capacity calculation.

SGR

0.0

Steel grade as per table 3.1 in EC3. 0.0 = Fe 360 510

SBLT

0.0

CMM

1.0

1.0 = Fe 430

2.0 = Fe

Indicates if the section is rolled or built-up. 0.0 = Rolled

1.0 = Built-up.

Indicates type of loading on member. Can take a value from 1 to 6. Refer to Table 5B.2 for more information on its use.

CMN

1.0

Indicates the level of End-Restraint.

1.0 1.0 = No fixity

0.5 = Full fixity

0.7 = One end free and other end fixed


5-16

Section 5B

Table 5B.1 – Steel Design Parameters EC3 Parameter

Default

Definition

Name

Value

DMAX

100.0 cm

DMIN

0

Minimum required depth for the member.

RATIO

1

Permissible ratio of loading to capacity.

BEAM

0

Indicates the number of sections to be checked for during the design.

Maximum allowable depth for the member.

0 = Check the end sections only or the locations specified by the SECTION command. 1 = Consider 13 sections along the member and select the maximum Mz location for the design check. 2 = Same as BEAM = 1.0 but checks the end sections of the member as well. 3 = Consider 13 sections along the member and design check every section. CODE

Undefined

TRACK

0

User must specify EC3. Controls the level of descriptivity of output. 0 = Minimum 1 = Intermediate 2 = Maximum 4 = option 4 for performing a deflection check

UNF

1.0

Unsupported buckling length as a factor of the beam length

LEG

0.0

Connection type

LVV


FU

Buckling length for angle about its principle axis Ultimate tensile strength of steel

DFF


DJ1


DJ2

End Joint of member

Deflection limit Joint No. denoting starting point for calculation of "Deflection Length" Joint No. denoting end point for calculation of "Deflection Length"

Section 5B

Notes: 1.

LEG - Table 25 BS5950 for Fastener Control The slenderness of single and double angle, channel and tee sections are specified in BS 5950 table 25 depending on the connection provided at the end of the member. To define the appropriate connection, a LEG parameter should be assigned to the member. The following table indicates the value of the LEG parameter required to match the BS5950 connection definition: Clause 4.7.10.2 Single Angle

(a) - 2 bolts (b) - 1 bolt

4.7.10.3 Double Angle

(a) - 2 bolts (b) - 1 bolt (c) - 2 bolts (d) - 1 bolt

short leg long leg short leg long leg

LEG 1.0 3.0 0.0 2.0

short leg long leg short leg long leg long leg short leg long leg short leg

3.0 7.0 2.0 6.0 1.0 5.0 0.0 4.0

4.7.10.4 Channels


1.0 0.0

4.7.10.5 Tee Sections


1.0 0.0

5-17


5-18

Section 5B

For single angles, the slenderness is calculated for the geometric axes, a-a and b-b as well as the weak v-v axis. The effective lengths of the geometric axes are defined as:La = KY * KY Lb = KZ * LZ The slenderness calculated for the v-v axis is then used to calculate the compression strength p c for the weaker principal axis (z-z for ST angles or y-y for RA specified angles). The maximum slenderness of the a-a and b-b axes is used to calculate the compression strength p c for the stronger principal axis. Alternatively for single angles where the connection is not known or Table 25 is not appropriate, by setting the LEG parameter to 10, slenderness is calculated for the two principal axes y-y and z-z only. The LVV parameter is not used. For double angles, the LVV parameter is available to comply with note 5 in table 25. In addition, if using double angles from user tables, (Technical Reference Manual section 5.19) an eleventh value, r vv, should be supplied at the end of the ten existing values corresponding to the radius of gyration of the single angle making up the pair. 2. BEAM Ensure that the “BEAM” parameter is set to either 1 or 2 while performing code checking for members susceptible to Lateral Torsional Buckling.

Section 5B

Table 5B.2

5B.3 Tabulated Results of Steel Design A design performed to the new Eurocode 3 standard is displayed in the output file (*.ANL) with the following header: STAAD.PRO CODE CHECKING - (BS EN 1993-1-1:2005) ************************** PROGRAM CODE REVISION V1.1 BS_EC3_2005/1

5-19


5-20

Section 5B

The equivalent header for a code check (or member selection) to the older standard is displayed thus:STAAD.PRO CODE CHECKING - (DD ENV) *********************** PROGRAM CODE REVISION V1.14_EC3_94/1

5B.4 Worked Examples Example 1: Restrained simply supported beam. The figure below shows a simply supported beam spanning 7 meters and assumed to be fully restrained laterally. Fe 430 steel is assumed and the beam will be checked to the clauses of EC3 currently implemented in STAAD.

Unfactored Loading Permanent Load: UDL including selfweight assume

20 KN/m

Variable Load: UDL load assume

25 KN/m

Partial safety factor for permanent load (ULS) 1.35 Partial safety factor for variable load (ULS) 1.5

Factored Load :

1.35 X 15 + 1.5 X 25 = 64.5 KN/m

Section 5B

64.5 KN/m

Try 457 X 191 X 82UB. h = 460.2 mm

d = 407.9mm

t w = 9.9 mm

b = 191.3 mm

t f = 16.0 mm

A = 104.5cm 2

l y = 37103 cm 4

W pl.y = 1833 cm 3

A v = 48.13 cm 2

Grade Fe 430 F y = 275 N/mm 2 Section Classification Outstand Flanges in Compression, limit for rolled section c/t = 10e = 9.2 c/t ratio for the selected section is 95.65/16 = 5.9 < 9.2 Flange is therefore a class 1 element. Web with N.A. at mid depth, limit for rolled section d/t w = 72e = 66.6 d/ t w ratio for the selected section is 407.9/9.9 = 41.2 < 66.6 Web is therefore a class 1 element. Section is class 1

5-21


5-22

Section 5B

Shear Resistance Maximum design shear force (64.5 X 7) / 2 = 225.7 KN Plastic shear resistance V pl.Rd = (A v / gM0) (f y / 3 ) = (4813 / 1.1) (275 / 1.732) / 1000 = 694.7 KN Maximum design shear force = 225.7 KN < 694.7 KN Therefore shear resistance is satisfactory. Moment Resistance Maximum design moment at mid-span of beam (wl 2 / 8) = 395 Knm Maximum resistance of section M c.Rd = ( W pl.y fy ) / gM0 = (1833 X 10 3 X 275) / (1.1 X 10 6 ) = 458.2KNm Maximum design moment = 395 KNm < 458.2 KNm Therefore moment resistance is satisfactory.

Lateral Torsional Buckling As it is assumed that the full length of member is restrained laterally there is no need to check for Lateral Torsional Buckling of the member.

457 X 191 X 82 UB In Fe 430 Steel is satisfactory.

Section 5B

Example 2: Unrestrained simply supported beam. Figure 2 shows a simply supported beam spanning 5 meters and assumed to be laterally unrestrained. Fe 430 steel is assumed and the beam will be checked to the clauses of EC3 currently implemented in STAAD.

5m

Unfactored Loading Permanent Load: UDL including selfweight assume

15 KN/m

Variable Load: UDL load assume

20 KN/m

Partial safety factor for permanent load (ULS) Partial safety factor for variable load (ULS)

1.35 1.5

Factored Load :

1.35 X 15 + 1.5 X 20 = 50.3 KN/m

50.3 KN/m

5m

5-23


5-24

Section 5B

Try 457 X 191 X 82 UB. h = 460.2 mm

d = 407.9 mm

t w = 9.9 mm

b = 191.3 mm

t f = 16.0 mm

A = 104.5 cm 2

l y = 37103cm 4

W pl.y = 1833cm 3

A v = 48.13cm 2

Grade Fe 430f y = 275 N/mm 2 Section Classification Outstand Flanges in compression, limit for rolled section c/t = 10e = 9.2 c/t ratio for the selected section is 95.65/16 = 5.9 < 9.2 Flange is therefore a class 1 element. Web with N.A. at mid depth, limit for rolled section d/t w = 72e = 66.6 d/ t w ratio for the selected section is 407.9/9.9 = 41.2 < 66.6 Web is therefore a class 1 element. Section is class 1

Shear Resistance Maximum design shear force Plastic shear resistance

(50.3 X 5) / 2 = 120.8 KN

V pl.Rd = (A v / gM0) (f y / 3 ) = (4813 / 1.1) (275 / 1.732) / 1000 = 694.7 KN

Maximum design shear force = 120.8 KN < 694.7 KN Therefore shear resistance is satisfactory.

Section 5B

Moment Resistance Maximum design moment at mid-span of beam (wl 2 / 8) = 157.2 KNm Maximum resistance of section M c.Rd = ( W pl.y fy ) / gM0 = (1833 X 10 3 X 275) / (1.1 X 10 6 ) = 458.2KNm Maximum design moment = 157.2 KNm < 458.2 KNm Therefore moment resistance is satisfactory.

Lateral Torsional Buckling Buckling resistance moment M b.Rd = X LT b w W Pl. y fy / gM1 b w = 1 for Class 1 or Class 2 sections. X LT =

f LT

1 f LT  [f

2

LT

 l 2 LT ]0.5

= 0.5 [1 + a LT ( l LT – 0.2 ) + l 2 LT ]

a LT = 0.21 for rolled sections. l LT

= [ l LT / l 1 ] [bw ] 0.5

l1

= 93.9e

l LT is the geometrical slenderness ratio for lateral -torsional buckling. l LT =

L/i LT (C1 )

0.5

[1  (L/a LT ) 2 /25.66]

a LT = ( I w / l t )

0.5

5-25


5-26

Section 5B

lw

= l zh s 2 / 4

hs

= h - tf

i LT = [l z I w / W pl.y 2 ] 0.25 C 1 is a factor depending on transverse loading type. For the selected section: hs

= 460.2 – 16.0

=

444.2 mm

lw

= 1871 X 44.42 2 / 4

=

922934.6 cm 6

i LT = [1871 X 922934.6 / (1833 2 ) ] 0.25 = a LT = ( 922934.6 / 69.2 )

0.5

=

4.76 cm

115.4 cm

C 1 = 1.132 (From EC3 Table F.1.2) l LT =

l1

500/4.76 1.132 [1  (500/115.4) 2 /25.66]0.25 0.5

= 86.06

= 93.9 (235 / 275) 0.5

86.8

l LT = 86.06 / 86.8 f LT

0.99

= 0.5 [1 + 0.21 (0.99 – 0.2) + 0.99 2 ]

X LT = 1 / { 1.07 + [ 1.07 2 – 0.992 ]

0.5

}

1.07 0.67

M b.Rd = 0.67 X 1 X 1833 X 10 3 X 275 / 1.1 X 10 6 M b.Rd = 307.0 KNm

Maximum design moment = 157.2 KNm < 307.0 KNm Therefore buckling resistance moment is satisfactory.

Section 5B

Example 3: Axially Loaded Column. Figure 3 shows a pinned end column 5m long subject to a factored load of 3500 kN. Fe 430 steel is assumed and the column will be checked to the clauses of EC3 currently implemented in STAAD. 3500 KN

5m

3500 KN Try 305 X 305 X 158 UC h = 327.2 mm

d = 246.6 mm

t w = 15.7 mm

b = 310.6 mm

t f = 25.0 mm

A = 210.2 cm 2

i y = 13.9 cm

i z = 7.89 cm

fy = 275 N/ mm 2

Section Classification Outstand flanges in compression, limit for rolled section c/t = 10e = 9.2 c/t ratio for the selected section is 155.3/25 = 6.21 < 9.2 Flange is therefore a class 1 element.

5-27


5-28

Section 5B

Web with N.A. at mid depth, limit for rolled section d/t w = 33e = 30.5 d/ t w ratio for the selected section is 246.6/15.7 = 15.7 < 30.5 Web is therefore a class 1 element. Section is class 1 Compressive resistance Design compression resistan ce of the cross-section, N c.Rd = ( A fy ) / gM0 N c.Rd = ( 210.2 X 10 2 X 275 ) / ( 1.1 X 10 3 ) N c.Rd = 5255 KN Applied design load N Sd = 3500 KN < 5255 Therefore compression resistance is satisfactory . Buckling resistance The design buckling resistance of the member N b.Rd = Xb A Af y / gM0 b A = 1 for class 1, 2 or 3 cross-sections. X is a reduction factor for the relevant buckling mode. 1

X =

_2

f  [f  l ]0.5 2

_

_2

f = 0.5 [ 1 + a ( l – 0.2) + l ] a is an imperfection factor. _

l = [ l / l 1 ] [ bA ] 0.5

l is the slenderness for the relevant buckling mode.

Section 5B

l 1 = 93.9 e From table 5.5.3 for buckling about y-y-axis, a is 0.34. From table 5.5.3 for buckling about z-z axis, a is 0.49. l y = 500 / 13.9 l y = 35.97 lz = 500 / 7.89 lz = 63.37 Consider buckling about the y-y axis. _

l y = [ l y / l 1 ] [bA ] 0.5

l 1 = 93.9 X 0.924 = 86.8 _

l y = [35.9 / 86.8 ] = 0.41 _

f y = 0.5 [1 + a y ( l y – 0.2) + l 2 y ] f y = 0.5 [1 + 0.34 (0.41 – 0.2) + 0.41 2 ] f y = 0.62 1

Xy = f y  [f

2

_2

y

l

= 0.5

1 0.62  [0.622  0.412 ]0.5

y]

X y = 0.92 but cannot be greater than 1, therefore X y = 0.92. N b.Rdy = X y Afy / gM0 = (0.92 X 275 X 201.2 X 10 2 ) / (1.1 X 10 3 ) = 4627KN

5-29


5-30

Section 5B

Consider buckling about the z-z axis. _

l z = [ l z / l 1 ] [bA ] 0.5

l 1 = 93.9 X 0.924 = 86.8 _

l z = [63.37 / 86.8 ] = 0.73 _2

_

fz = 0.5 [1 + a z ( l z – 0.2) + l z ] fz = 0.5 [1 + 0.49 (0.73 – 0.2) + 0.73 2 ] fz = 0.89 Xz =

1

=

_2

f z  [f 2 z  l

z]

0 .5

1 0.89  [0.892  0.732 ]0.5

X z = 0.71 but cannot be greater than 1, therefore X z = 0.71. N b.Rdz = X z Afz / gM0 = (0.71 X 275 X 201.2 X 10 2 ) / (1.1 X 10 3 ) = 3571KN 3400 KN design load is less than 3571 KN, therefore section is satisfactory.

Section 5B

Example 4: Column subject to axial load and bending The figure below shows a pinned end column 5m long subject to a factored load of 1500 KN and factored bending moment of 250 KNm about the major axis. Fe 430 steel is assumed and the column will be checked to the clauses of EC3 currently implemented in STAAD.

Try 305 X 305 X 137 UC h = 320.5 mm

d = 246.6 mm

t w = 13.8 mm

b = 308.7mm

t f = 21.7 mm

A = 174.6cm 2

W pl.y = 2298cm 3

W el.y = 2049 cm 3

A v = 50.6 cm 2

i y = 13.7 cm

i z = 7.82 cm

f y = 275 N/mm 2

5-31


5-32

Section 5B

Section classification

Section by inspection is class 1.

Shear Resistance Maximum design shear force 250 / 5 = 50 KN Plastic shear resistance V pl.Rd = ( A v / gM0 ) ( f y / 3 ) = (5060 / 1.1) (275 / 1.732) / 1000 = 730 KN Design shear force is less than 730 KN. Shear resistance is satisfactory. Moment Resistance Design bending moment must not exceed the reduced plastic resistance moment of the section given by the following equations. M Ny.Rd = Mpl.y.Rd ( 1 – n ) / ( 1 – 0.5 a ) a = ( A – 2bt f ) / A but „a‟ must not exceed 0.5. n = N sd / Npl.Rd If „n‟ does not exceed „a‟ then M Ny.Rd = Mpl.y.Rd a = ( 17460 – 2 X 308.7 X 21.7 ) / 17460 a = 0.232 N pl.Rd = ( 275 X 17460 ) ( 1.1 X 1000 ) = 4365 KN n = 1500 / 4365 = 0.343

Section 5B

5-33

M pl.y.Rd = ( 275 X 2298 ) / ( 1.1 X 1000 ) = 574.5 KN M Ny.Rd = 574.5 ( 1 – 0.343 ) / ( 1 – 0.5 X 0.232 ) M Ny.Rd = 426.97 KNm

The design bending moment is less than the reduced moment capacity. The section therefore has sufficient moment resistance. Flexural Buckling and Bending Check Members subject to axial load and bending must satisfy: K y M y.sd N sd + X min Af y /gM1 Wpl.y f y /gM1

Ky = 1 -

m y N sd X y Af y

_

 1

but K y  1.5

m y = l y (2bMy – 4) +

Wpl.y  Wel.y Wel.y

but m y  0.90

X min is the lesser of X y and X z , where X y and X z are reduction factors as calculated in the previous example. bM y is equivalent moment factor for flexural buckling. From Figure 5.5.3 in EC3, bM y = 1.8 – 0.7 y but in this example, y = 0.0 bMy = 1.8


5-34

Section 5B

Consider buckling about the y-y axis. _

l y = [ l y / l 1 ] [bA ] 0.5

b A = 1.0 for class 1 sections.

l 1 = 93.9 X 0.924 = 86.8 l y = [500 / 13.7 ] = 36.5 _

l y = [36.5 / 86.8 ] = 0.42 _

f y = 0.5 [1 + a y ( l y – 0.2) + l 2 y ] f y = 0.5 [1 + 0.34 (0.42 – 0.2) + 0.42 2 ] f y = 0.62 Xy =

1 f y  [f y  l y ] 2

2

1

=

0.5

0.62  [0.622  0.422 ]0.5

X y = 0.93 but  1, therefore X y = 0.93. Consider buckling about the z-z axis. _

l z = [ l z / l 1 ] [bA ] 0.5

b A = 1.0 for class 1 sections.

l 1 = 93.9 X 0.924 = 86.8 l z = [500 / 7.82 ] = 63.9 _

l z = [63.9 / 86.8] = 0.73 _

_

fz = 0.5 [1 + a z ( l z – 0.2) + l 2 z ] fz = 0.5 [1 + 0.49 (0.73 – 0.2) + 0.73 2 ] fz = 0.89

Section 5B

1

Xz =

1

=

_2

0.89  [0.892  0.732 ]0.5

f z  [f 2 z  l z ]0.5

X z = 0.71 but  1, therefore X z = 0.71. X min is therefore 0.71. _

l y = 0.42

m y = 0.42 (2 X 1.8 – 4) +

Ky = 1 -

2298 2049 2049

= - 0.046

0.046X1500 = 1.015  1.5 0.93X17.46X275

K y M y.sd N sd + X min Af y /gM1 Wpl.y f y /gM1

 1

1500 1.015X250 + = 0.92  1 0.71X17.46X275/1.1 2.298X275/1.1

Members for which lateral-torsional buckling is a potential problem must also satisfy: K LT M y.sd N sd + X z Af y /gM1 X LT Wpl.y f y /gM1

K LT = 1 -

 1

m LT N sd but K LT  1 X z Af y

m LT = 0.15 l z bM.LT – 0.15, but m LT  0.90 Using the equations used in Example 2, we have the following.

5-35


5-36

Section 5B

For the selected selection: i LT = 8.33 cm a LT = 97.6 cm C 1 = 1.879 (From EC3 Table F.1.2) l LT =

500/8.33 1.879 [1  (500/97.6)2 /25.66]0.25 0.5

= 36.71

l 1 = 93.9 (235 / 275) 0.5 = 86.8 l LT = 36.71 / 86.8 = 0.42 f LT = 0.5 [ 1 + 0.21 (0.42 – 0.2) + 0.42 2 ] = 0.61 X LT = 1 / { 0.61 + [ 0.61 2 – 0.42 2 ]0.5 } = 0.95 bM LT = 1.8 lz = 0.73 m LT = 0.15 X 0.73 X 1.8 – 0.15 = 0.047 K LT = 1 -

0.047X1500 = 0.98 0.71X17.46X275

K LT M y.sd N sd + X z Af y /gM1 X LT Wpl.y f y /gM1

 1

1500 0.98X250 + = 0.932 0.71X17.46X275/1.1 0.95X2.298X275/1.1

305X305X137UC is therefore satisfactory.

Section 5B

5B.5 User’s Examples

Example 1. The following input file is for the single beam in example 1. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EX.1 IN THE EC3 MANUAL. INPUT WIDTH 79 UNIT METER KNS JOINT COORDINATES 1 0.000 0.000 0.000 2 5.000 0.000 0.000 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTY BRITISH 1 TABLE ST UB457X191X82 CONSTANTS E STEEL ALL SUPPORTS 1 PINNED 2 FIXED BUT FX MZ LOAD 1 MEMBER LOAD 1 UNI GY-20.0 LOAD 2 MEMBER LOAD 1 UNI GY -25.0 LOAD COMBINATION 3 1 1.35 2 1.5 PERFORM ANALYSIS LOAD LIST 3 PARAMETER CODE EC3 UNL 0.0 ALL BEAM 2.0 ALL TRACK 2 .ALL SGR 1 .ALL CHECK CODE ALL FINISH

5-37


5-38

Section 5B

Section 5B

Example 2. The following input file is for the beam in example 2. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EXAMPLE 2 INPUT WIDTH 79 UNIT METER KNS JOINT COORDINATES 1 0.000 0.000 0.000 2 5.000 0.000 0.000 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTY BRITISH 1 TABLE ST UB457X191X82 CONSTANTS E STEEL ALL SUPPORTS 1 PINNED 2 FIXED BUT FX MZ LOAD 1 MEMBER LOAD 1 UNI GY -15.0 LOAD 2 MEMBER LOAD 1 UNI GY -20.0 LOAD COMBINATION 3 1 1.35 2 1.5 PERFORM ANALYSIS LOAD LIST 3 PARAMETER CODE EC3 BEAM 2.0 ALL TRACK 2. ALL SGR 1. ALL CHECK CODE ALL FINISH

5-39


5-40

Section 5B

Section 5B

Example 3. The following input file is for the simple column in example 3. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EXAMPLE 3. UNIT METER KNS JOINT COORDINATES 1000 2050 MEMBER INCIDENCES 112 MEMBER PROPERTIES BRITISH 1 TA ST UC305X305X158 CONSTANTS E STEEL ALL SUPPORT 1 FIXED LOAD 1 JOINT LOAD 2 FY -3500 PERFORM ANALYSIS PARAMETERS CODE EC3 TRACK 2.0 ALL SGR 1. ALL CHECK CODE ALL FINISH

5-41


5-42

Section 5B

Section 5B

Example 4. The following input file is for the column in example 4. Only code check related output is enclosed. STAAD PLANE INPUT FILE FOR EXAMPLE 4. UNIT METER KNS JOINT COORDINATES 1000 2050 MEMBER INCIDENCES 112 MEMBER PROPERTIES BRITISH 1 TA ST UC305X305X137 CONSTANTS E STEEL ALL SUPPORT 1 PINNED 2 FIXED BUT FY MZ LOAD 1 JOINT LOAD 2 FY -1500 2 MZ 250 PERFORM ANALYSIS PARAMETERS CODE EC3 BEAM 2.0 ALL TRACK 2.0 ALL CMM 6 SGR 1.0 ALL CHECK CODE ALL FINISH

5-43


5-44

Section 5B

5-45

Timber Design Per EC 5: Part 1-1. (BS EN 1995-1-1:2004) Section

5C

5C.1 General Comments The Timber Design facility as per EC5 in STAAD is based on the European Standard Eurocode 5: Design of Timber Structures - Part 1-1 - General - Common rules and rules for buildings. Principles of Limit States Design of Timber Structures are adopted as specified in the code. The application is limited to the PRISMATIC rectangular shapes only. There is no Eurocode-specific timber section database / library consisting of pre-defined shapes for analysis or for design. The feature of member selection is thus not applicable to this code. The design philosophy of this specification is based on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major cat egories of limitstate are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for all timber structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned to resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria as augmented by the designer in specification of allowable member depths, desired section type, or other such parameters. The code

Timber Design Per EC 5: Part 1-1.

5-46

Section 5C

checking portion of the program checks whether code requirements for each selected section are met and identifies the governing criteria. The following sections describe the salient features of the STAAD implementation of EC 5. A detailed description of the design process along with its underlying concepts and assumptions is available in the specification document. Axes convention in STAAD and EC5 STAAD defines the major axis of the cross-section as zz and the minor axis as yy. The longitudinal axis of the member is defined as x and joins the start joint of the member to the end with the same positive direction. EC5, however, defines the principal cross-section axes in reverse to that of STAAD, but the longitudinal axis is defined in the same way. Both of these axes definitions follow the orthogonal right hand rule. See figure 1 below:

y

z

z

z

y

y

y

z

STAAD

EC5

Figure 1 Axes convention in STAAD and EC5

Section 5C

Determination of Factors (A)

Kmod – Modification factor taking into account of Loadduration (LDC) and Moisture-content (Service Class SCL). Reference Table 3.1 of EC-5-2004. For “Solid Timber”, the values are incorporated in the program.

(B)

m – Partial factor for Material Property values. Reference Table 2.3 of EC-5-2004. For “Solid Timber”, the value of m (= 1.3) is incorporated in the program.

(C)

Kh – Size Factor. For members, subjected to tension, whose maximum c/s dimension is less than the reference width in tension the characteristic strength in tension (ft0k) is to be increased by the factor Kh. For members, subjected to bending, whose depth is less than reference depth in bending, the characteristic strength in bending (fmk) is to be increased by the factor Kh. As per clause 3.2(3) of EC 5- 2004, for rectangular solid timber with a characteristic timber density k  700 kg/m 3 the reference depth in bending or the reference width (maximum cross-sectional dimension) is 150 mm. The value of Kh = Minimum of {(150/h) 0.2 and 1.3) for such solid timber is incorporated in the software. Please refer clause numbers 3.3 and 3.4 for the value of K h for Glued laminated timber and Laminated veener lumber respectively.

5-47


5-48

Section 5C

(D)

KC90 – Factor taking into account the load configuration, possibility of splitting and degree of compressive deformation. For members, subjected to compression, perpendicular to the direction of grain alignment, this factor should be taken into account. Default value of 1 is used in STAAD.Pro. User may override the value. Please refer clause 6.1.5 of EC-5-2004 in this regard.

(E)

Km – Factor considering re-distribution of bending stress in cross section. For members, subjected to bending, this factor is taken into account for stress checking. For rectangular section the value of Km is 0.7, and this value is incorporated in STAAD.Pro. User may override the value. Please refer clause 6.1.6 of EC-5-2004 in this regard.

(F)

Kshape – Factor depending on shape of cross section. For members, subjected to torsional force, design torsional stress should be less than equal design shear strength multiplied by the factor Kshape. This factor is determined by STAAD.Pro internally using the guidelines of clause 6.1.8 of EC-5-2004 .

Section 5C

5C.2 Analysis Methodology Symbols

Description

S t0d

Design tensile stress parallel (at zero degree) to grain alignment. Design tensile stress perpendicular (at 90 degrees) to grain alignment.

S t90d S c0d

Design compressive stress parallel to grain alignment.

S c90d S mzd

Design compressive stress perpendicular to grain alignment. Design bending stress about zz axis.

S myd S vd

Design bending stress about yy axis. Design shear stress.

S tor_d

Design torsional stress.

F t0d

Design tensile strength - parallel to the grain alignment.

F t90d

Design tensile strength - perpendicular to the grain alignment.

F c0d

Design compressive strength - parallel to the grain alignment.

F c90d F mzd

Design compressive strength - perpendicular to the grain alignment. Design bending strength - about zz-axis.

F myd F vd

Design bending strength - about yy-axis. Design shear strength about yy axis.

RATIO

Permissible ratio of stresses as provided by the user. The default value is 1.

5-49


5-50

Section 5C

Symbols

Description

 z , rel,z

Slenderness ratios correspon ding to bending about zz axis. Slenderness ratios corresponding to bending about yy axis.

 y , rel,y

E 0,05

Fifth percentile value of modulus of elasticity parallel to grain.

G 0,05

Fifth percentile value of shear modulus parallel to grain.

Iz Iy

Second moment of area about the strong z-axis. Second moment of area about the weak y-axis.

I tor

Torsional moment of inertia.

f mk

Characteristic bending strength.

b, h

Width and depth of beam.

Equations for Characteristic Values of Timber Species as per Annex-A of EN 338:2003 The following equations were used to determine the characteristic values: Basic Inputs: For a particular Timber Strength Class (TSC), the following characteristic strength values are required to compute the other related characteristic values. 1. Bending Strength – fm, k 2. Mean Modulus of Elasticity in bending – E 0, mean 3. Density -  k

Section 5C

Sl. No. 1. 2. 3. 4. 5. 6. 7.

5-51

Wood Type Property

Symbol

Tensile Strength parallel to grain Tensile Strength perpendicular to grain Compressive Strength parallel to grain Compressive Strength perpendicular to grain Shear Strength

Hardwood (D)

ft,0,k

0.6 * fm, k

ft,90,k

Minimum of {0.6 and (0.0015*k )}

fc,0,k

5 * (fm,k ) 0.45

fc,90,k f v, k

Modulus of Elasticity parallel to grain Mean Modulus of Elasticity perpendicular to grain

Softwood (C)

0.007*k

0.0015*k

Minimum of {3.8 and (0.2*f m, k 0.8 )}

E 0,05

0.67* E 0,mean

0.84* E 0,mean

E 90,mean

E 0,mean /30

E 0,mean /15

8.

Mean Shear Modulus

G me an

E 0,mean /16

9.

Shear Modulus

G 0,05

E 0,05 /16

The values of the characteristic strengths computed using the above equations, may differ with the tabulated values in Table -1 of EN 338:2003. However, in all such cases, the values obtained from the provided equations are treated as actual and is used by the program, as the values of Table-1 are based on these equations. Finding the Design values of Characteristic Strength As per clause 2.4.1, Design values of a strength property shall be calculated as:

X d  K mod  X k  m 


5-52

Section 5C

Where X d is design value of strength property, X k characteristic value of strength property and  m is partial factor for material properties. The member resistance in timber structure is calculated in STAAD according to the procedures outlined in EC5. This depends on several factors such as cross sectional properties, different load and material factors, timber strength class, load duration class, service class and so on. The methodology adopted in STAAD for calculating the member resistance is explained here. Check for Tension stresses If the direction of applied axial tension is parallel to the direction of timber grain alignment, the following formula should be checked:



St0d Ft0d

  RATIO

…….(cf : Equation 6.1 of EC-5-2004)

If the direction of applied axial tension is perpendicular to the direction of timber grain alignment, the following formula should be checked:



S t90d Ft90d

  RATIO

Check for Compression stresses If the direction of applied axial compression is parallel to the direction of timber grain alignment, the following formula should be checked:



Sc0d Fc0d

  RATIO

…….(cf: Equation 6.2 of EC-5-

2004) If the direction of applied axial compression is perpendicular to the direction of timber grain alignment, the following formula should be checked:



Section 5C

Sc90d Fc90d  Kc90   RATIO (cf: Equation 6.3 of EC-5-

5-53

2004) Check for Bending stresses If members are under bending stresses, the following conditions should be satisfied. Please note that in STAAD z-z axis is the strong axis:

S   S mzd     Km   myd   RATIO .(cf: Equation 6.11 of EC-5-2004) F   Fmzd   myd   S   S myd    RATIO .(cf: Equation 6.12 of EC-5-2004) Km   mzd       Fmzd   Fmyd  Check for Shear stresses Horizontal stresses are calculated and checked against allowable values:

 S vd     RATIO F  vd 

…….( cf: Equation 6.13 of EC-5-2004)

Check for Torsional stresses Members subjected to torsional stress should satisfy the following equation:

  S tor_d    RATIO .( cf: Equation 6.14 of EC-5-2004)  Kshape  F  tor_d  


5-54

Section 5C

Check for combined Bending and Axial tension Members subjected to combined action of bending and axial tension stress should satisfy the following conditions. Please note that in STAAD z-z axis is the strong axis:

 S t0d   Ft0d

S   S mzd       Km   myd F   Fmzd   myd

   RATIO  

….

 S t0d   Ft0d

(cf: Equation 6.17 of EC-5-2004)

 S  S   Km   mzd    myd    Fmzd   Fmyd

….

   RATIO  

( cf: Equation 6.18 of EC-5-2004)

Check for combined Bending and axial Compression If members are subjected to bending and axial compression stress, following equations should be satisfied. Please note that in STAAD z-z axis is the strong axis:

 S c0d   Fc0d

S   S mzd       Km   my d F   Fmzd   my d 2

….

 S c0d   Fc0d ….

   RATIO  


 S  S   Km   mzd    my d    Fmzd   Fmy d 2

   RATIO  


Section 5C

Stability check (A)

Column Stability check The relative slenderness ratios should be calculated as follows. Please note that in STAAD z-z axis is the strong axis:

 rel,z 

 rel, y 

S z  c0k  E 0,05 y 



S c0k E 0,05

…….( Equation 6.21 of EC-5-2004)

…….( Equation 6.22 of EC-5-2004)

If both  rel,z and  rel,y are less than or equal to 0.3 the following conditions should be satisfied:

 S c0d   Fc0d

S   S mzd       Km   my d F   Fmzd   my d

   RATIO  

 S c0d   Fc0d

 S  S   Km   mzd    my d    Fmzd   Fmy d

   RATIO  

2

2

In other cases, the following conditions should be satisfied. Please note that in STAAD z-z axis is the strong axis:

 Sc0d   Kcz  Fc0d …

S   S mzd       Km   myd F   Fmzd   myd

   RATIO  


5-55


5-56

Section 5C

 Sc0d   Kcy  Fc0d

 S  S   Km   mzd    myd    Fmzd   Fmyd

   RATIO  

... ( cf: Equation 6.24 of EC-5-2004) Where the symbols Kcz and Kcy are defined as follows. Please note that in STAAD z-z axis is the strong axis:

Kcz 

Kcy 

1

Kz 

Kz 2   rel,z 2 1

Ky 

Kz     2

2

...( Equation 6.25 of EC-5-2004)

…( Equation 6.26 of EC-5-2004)

rel, y



2



2

Kz  0.5  1   c   rel,z  0.3   rel,z 

Ky  0.5  1   c   rel, y  0.3   rel, y 

 ( Equation 6.27 of EC-5-2004)  .( Equation 6.28 of EC-5-2004)

The value of  c incorporated in the software is the one for solid timber ,i.e. 0.2. (B)

Beam Stability check If members are subjected to only a moment about the strong axis z, the stresses should satisfy the following equation:

S mzd  RATIO .( cf: Equation 6.33 of EC-5-2004) Kcrit  Fmzd

Section 5C

Where a combination of moment about the strong z -axis and compressive force exists, the stresses should satisfy the following equation: 2

   Sc0d S mzd      Kcrit  Fmzd   Kcz  Fc0d ……

   RATIO 


Where,

  1  Kcrit  1.56  0.75   rel,m  1   rel,m 2  …..

 rel,m 

f mk S m ,crit

for  rel,m  0.75 for 0.75   rel,m  1.4 for 1.4   rel,m

( Equation 6.34 of EC-5-2004)

……..( Equation 6.30 of EC-5-2004)

For hardwood:

S m,crit 

  E 0,05  I y  G 0,05  I tor l ef Wz ….

(Equation 6.31 of EC-5-2004)

For softwood:

S m ,crit 

0.78  b 2  E 0, 05 ….( Equation 6.32 of EC-5-2004) h  l ef

5-57


5-58

Section 5C

5C.3 Design Parameters Design parameters communicate specific design decisions to the program. They are set to default values to begin with and may be altered to suite the particular structure. Depending on the model being designed, the user may have to change some or all of the parameter default values. Some parameters are unit dependent and when altered, the new setting must be compatible with the active “unit” specification. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

Parameter Name

Default Value

Description

SCL

3

Service Class (Ref. Cl.2.3.1.3)  1 = Class 1, Moisture content <= 12%  2 = Class 2, Moisture content <= 20%  3 = Class 3, Moisture content > 20%

LDC

1

Load Duration Class (Ref. Cl.2.3.1.2), required to get the K-MOD value from Table – 3.1.  1 - Permanent action  2 - Long term action  3 - Medium term action  4 - Short term action  5 - Instantaneous action

Section 5C

Parameter Name

Default Value

Description

TSC

6 (C24)

Timber Strength Class (Ref. Reference EN338 – 2003) Softwood: 1 = C14, 2 = C16, 3 = C18, 4 = C20, 5 = C22, 6 = C24, 7 = C27, 8 = C30, 9 = C35, 10 = C40, 11 = C45, 12 = C50. Hardwood: 13 = D30, 14 = D35, 15 = D40, 16 = D50, 17 = D60, 18 = D70. This TSC definition will calculate the corresponding characteristic strength values using the equations as given in BS-EN-338, Annex - A.

ALPHA

0.0

Angle of inclination of load to the grain alignment. (Ref. Cl.6.1.1, Cl.6.1.2, Cl.6.1.3, Cl.6.1.4) 0.0 = Load parallel to grain, 90.0 = Load Perpendicular to grain

KC90

1.0

Factor taking into account the load configuration, possibility of splitting and degree of compressive deformation. (Ref. Cl.6.1.5-(2))  Range: 1.0  KC90  4.0  Other than the default value, user may specify any value within the range, depending on load-position, loaddispersion, contact length at support locations etc.

5-59


5-60

Section 5C

Parameter Name

Default Value

Description

MTYP

0

Member Type: Beam/Column. (Ref. Cl.6.3.2, Cl.6.3.3)  0 – Not defined by the user – checks both clauses (Default).  1 – Beam Member  2 – Column Member This information is required to find which stability check will be performed as per the Cl 6.3 according to the Member Type.

KLEF

1.0 (Member Length)

Effective Length Factor to check Lateral Torsional Buckling. (Ref. Table 6.1) Span of the beam depending on the support conditions and load configurations. The user will put the appropriate value from the Table 6.1. Required only for MTYP has a value of 1 (Beam).

KLY

KLZ

1.0 (Member Length)

Effective Length Factor for Local-y-axis. (Ref. Cl.6.3.2), for the computation of the relative slenderness ratios.

1.0

Effective Length Factor for Local-z-axis. (Ref. Cl.6.3.2), for the computation of the relative slenderness ratios.

(Member Length) TRACK

0

Degree/Level of Details of design output results. Available options: 0 / 1 / 2

RATIO

1.0

Permissible ratio of actual to allowable value.

Section 5C

Parameter Name SERV

Default Value No Default Value

Description Defines the load case numbers – those are to be considered for serviceability (deflection) check.  The list of this parameter must contain only the valid load-case numbers.  Deflection checks will be performed only on those load-case results.  If this parameter is not provided, then in-spite of the presence of the parameter DFF – the deflection check will NOT be performed.

DFF

No Default Value

“Deflection Length” / Max. Allowable Net Final Local Deflection. In this case, deflection check will be performed, if both the parameters SERV and DFF are present with specific values. For appropriate range of values, please refer Cl.7.2 (Table 7.2)

DJ1

Start node number for a physical member under consideration for Deflection Check.

DJ2

End node number for a physical member under consideration for Deflection Check.

5C.4 Verification Problems In the next few pages are included 2 verification examples for reference purposes.

5-61


5-62

Section 5C

Verification Problem No. 1 A Timber Column of length 1.0 meter, having c/s dimension of 73 mm X 198 mm, is subjected to an axial compressive force of 50.0 kN. Design of the member - ULTIMATE LIMIT STATE Material properties: Timber class: C24 Service classes: Class 2, moisture content <= 20% Load duration classes: Medium-term Cross section properties: Length of the member is 1 m. Rectangular cross section, b = 73 mm, h = 198 mm, Effective cross sectional area A = 14454 mm², Radius of gyration of cross section about y-axis r y = 21 mm, Radius of gyration of cross section about z -axis r z = 57 mm, Section modulus of cross section about z-axis: W z = 4.770x10 5 mm³ Section modulus of cross section about y-axis: W y = 1.759x10 5 mm³ Characteristic material properties for timber : Modification factor Kmod = 0.80 …from table 3.1 Material factors  m = 1.30 … from table 2.3 fc0k = 21.00 N/mm², F c0d = (Kmod.f c0k )/ m = (0.80x21.00)/1.30 = 12.92 N/mm²[Cl 2.4.1(1)P]

Section 5C

5-63

Cross section loads: F x = 50.000 kN Compression parallel to the grain: S c0d = (1000xF x )/A = (1000x50.000)/14454 = 3.46N/mm² < 12.92N/mm² (F c0d ) The ratio of actual compressive stress to allowable compressive strength: = 3.46 / 12.92 = 0.268 < 1.0 [Cl. 6.1.4.(1)P] Check for Slenderness: Slenderness ratios:  z = (1000/57) = 17.54 and  y = (1000/21) = 47.62 E 0,mean = 1.1031 kN/m 2 As timber grade is C24, i.e., Soft Wood, E 0,05 = 0.67 * E 0,mean … [Annex A,EN 338:2003]

 y  f c0k  rel, y     = 0.809 E 0, 05    f c0k    rel,z   z   = 0.298 E 0, 05    Since,  rel,y is greater than 0.3, following conditions should be satisfied:

 Sc0d  K F  c, y c0d 6.3.2.(3)]

  Smyd       Km   Smzd F  F   mzd   myd 

   RATIO 

[Cl.


5-64

Section 5C

 Sc0d   Kcz  Fc0d

S   Smzd       Km   myd F   Fmzd   myd

   RATIO  

[Cl.

6.3.2.(3)]

  .5  1  

 = 0.878  .3     = 0.541

K y  .5  1  rel, y  .3  rel, y 

Kz

K c,y  K c ,z 

2

2

rel,z

1 K y  K 2y  2rel,y 1 K z  K 2z  2rel,z

rel,z

= 0.82

= 1.0

For Rectangular cross section Km = 0.70. The member is subjected to Compression only, so actual bending stress is zero.

 Sc0d  K F  c, y c0d


  = 0.326 + 0.0 + 0.0 


  = 0.268 + 0.0 + 0.0  

= 0.326

 Sc0d   Kcz  Fc0d = 0.268

Hence the critical ratio is 0.326 < 1.0 and the section is safe.

Section 5C

The Input File: STAAD SPACE START JOB INFORMATION ENGINEER DATE END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 1.0 0 0; MEMBER INCIDENCES 1 1 2; DEFINE MATERIAL START ISOTROPIC WOOD E 1.10316e+007 POISSON 0.15 DENSITY 0.00231749 ALPHA 5.5e-006 END DEFINE MATERIAL CONSTANTS MATERIAL WOOD MEMB 1 MEMBER PROPERTY 1 PRIS YD 0.198 ZD 0.073 SUPPORTS 1 FIXED LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 JOINT LOAD 2 FX -50 PERFORM ANALYSIS PARAMETER CODE TIMBER EC5 ALPHA 0 ALL LDC 3 ALL SCL 2 ALL TSC 6 ALL TRACK 2 ALL CHECK CODE ALL FINISH

5-65


5-66

Section 5C

The member checking part of the output file:

Section 5C

5-67

Verification Problem No. 2 A Timber Column of length 1.0 meter, having c/s dimension of 73 mm X 198 mm, is subjected to an axial compressive force of 5.0 kN and moments of 2.0 kN.m and 1.0 kN.m about its major and minor axes respectively. Design of the member - ULTIMATE LIMIT STATE Material properties: Timber Strength Class: C24 Service classes: Class 2, moisture content <=20% Load duration: Medium-term Cross section properties: Length of the member is 1 m. Rectangular cross section, b = 73 mm, h = 198 mm, Effective cross sectional area A = 14454 mm², Radius of gyration of cross section about y-axis r y = 21 mm, Radius of gyration of cross section about z -axis r z = 57 mm, Section modulus of cross section about z-axis: W z = 4.770x10 5 mm³ Section modulus of cross section about y-axis: W y = 1.759x10 5 mm³ Characteristic material properties for timber : Modification factor, Material factor

Kmod = 0.80  m = 1.30

fc0k = 21.00 N/mm², E 0,05 = 7370 N/mm 2 , F c0d = Kmod.f c0k / m = (0.80x21.00)/1.30 = 12.92N/mm² f myk = 24.00 N/mm², F myd = Kmod.f myk / m = (0.80x24.00)/1.30 = 14.77N/mm² f mz k = 24.00 N/mm², F mzd = Kmod.f mz k / m = (0.80x24.00)/1.30 = 14.77N/mm²


5-68

Section 5C

Cross section loads: F x = 5.000 kN, M z = 2.000 kN.m, M y = 1.000 kN.m

Check for Slenderness: Slenderness ratios:  z = (1000/57) = 17.54 and  y = (1000/21) = 47.62

 y  f c0k = 0.809  rel, y      E 0 , 05   f c0k    rel,z   z   = 0.298 E 0, 05    Since,  rel,y is greater than 0.3, following conditions should be satisfied:

 Sc0d  K F  c, y c0d


   RATIO [Cl. 6.3.2.(3)] 



   RATIO  

  .5  1  

  .3     = 0.541

K y  .5  1   rel,y  .3   rel,y  = 0.878 Kz

K c,y  K c ,z 

2

2

rel,z

1 K y  K 2y  2rel,y 1 K z  K 2z  2rel,z

rel,z

= 0.82

= 1.0

[Cl. 6.3.2.(3)]

Section 5C

For Rectangular cross section Km = 0.70 S c0d = (1000F x /A) = (1000x5.000)/14454 = 0.35 N/mm² S mzd = (106 xM z )/W z = (10 6 x2.000)/(4.770x10 5 ) = 4.19 N/mm² S myd = (10 6 xM y )/W y = (106 x1.000)/(1.759x10 5 ) = 5.69 N/mm²

 Sc0d  K F  c, y c0d


  

= 0.033 + 0.385 + 0.198 = 0.616



   

= 0.027 + 0.283 + 0.269 = 0.579

Hence the critical ratio is 0.616 < 1.0 and the section is safe.

5-69


5-70

Section 5C

The Input File: STAAD SPACE START JOB INFORMATION ENGINEER DATE 08-Jun-05 END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 0 1 0; MEMBER INCIDENCES 1 1 2; DEFINE MATERIAL START ISOTROPIC WOOD E 1.10316e+007 POISSON 0.15 DENSITY 0.00231749 ALPHA 5.5e-006 END DEFINE MATERIAL CONSTANTS MATERIAL WOOD MEMB 1 MEMBER PROPERTY 1 PRIS YD 0.198 ZD 0.073 SUPPORTS 1 FIXED LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 JOINT LOAD 2 FY -5.0 MX 1.0 MZ 2.0 PERFORM ANALYSIS PARAMETER CODE TIMBER EC5 ALPHA 0 ALL LDC 3 ALL SCL 2 ALL TSC 6 ALL TRACK 2 ALL CHECK CODE ALL FINISH

Section 5C

The member checking part of the output file:

5-71


5-72

Section 5C

Section 6

Egyptian Codes

A‟lkjdfl‟akjsfd

6-1

Concrete Design Per EGYPTIAN CODE - ECCS205 Section

6A

6A.1 Design Operations STAAD has the capability of performing design of concrete beams, columns and slabs according to ECCS 203. The 2004 revision of the code is currently implemented. Given the width and depth of a section, STAAD will calculate the required reinforcement to resist the forces and moments.


UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350.

Concrete Design Per Egyptian Code ECC S205

6-2

Section 6A

6A.3 Design Parameters The program contains a number of parameters which are needed to perform the design. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. The following Beam Design Brief contains a complete list of the available parameters and their default values.


Section 6A

6A.4 Slenderness Effects and Analysis Considerations STAAD provides the user with two methods of accounting for the slenderness effects in the analysis and design of concrete members. The first method is equivalent to the procedure presented in ECCS203-2004 equation 4-11. In this section, the code recognizes that additional moments induced by deflection are present and states that these 'secondary' moments are accounted for by the design formula in equation 6-38, 6-37 etc. This is the method used in the design for concrete in STAAD. Alternatively STAAD houses a PDELTA ANALYSIS facility, which allows the effects of these second order moments to be considered in the analysis rather than the design. In a PDELTA analysis, after solving the joint displacements of the structure, the additional moments induced in the structure are calculated. These can be compared to those calculated using the formulation of ECCS203-2004.

6A.5 Beam Design Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are pre scanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,. 75,.8,.9 and 1). All of these sections are scanned to determine the design force envelopes.

6-3


6-4

Section 6A

Design for Flexure Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections is designed to resist both of these critical sagging and hogging moments. Currently, design of singly reinforced sections only is permitted. If the section dimensions are inadequate as a singly reinforced section, such a message will be permitted in the output. Flexural design of beams is performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is performed again in a second pass taking into account the changed effective depths of sections calculated on the basis of reinforcement provided after the preliminary design. Final provision s of flexural reinforcements are made then. Efforts have been made to m eet the guideline for the curtailment of reinforcements as per ECCS203 2004. Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the detailer taking into account of other practi cal consideration), user has the choice of printing reinforcements provided by STAAD at 13 equally spaced sections from which the final detailed drawing can be prepared. Design for Shear Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design is performed at 13 equally spaced sections (0.to 1.) for the maximum shear forces amongst the active load cases and the associated torsional moments. Shear capacity calculation at different sections without the shear reinfor cement is based on the actual tensile reinforcement provided by STAAD program. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections.

Section 6A

Beam Design Output

6-5


6-6

Section 6A

6A.6 Column Design Columns are designed for axial force and biaxial bending at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement is called the critical load and is displayed. The requirements of ECCS203 -2004 equation 6-37,6-38,6-41 etc are followed, with the user having control on the effective length parameters. Bracing conditions are controlled by using the BRACE parameter. The program will then decide whether or not the column is short or slender and whether it requires additional moment calculations.

Section 6A

Column Design output

6-7


6-8

Section 6A

Shear Design Output

6-9

Steel Design Per EGYPTIAN CODE #205 Section

6B

6B.1 General Comments This section presents some gener al statements regarding the implementation of Egyptian code of practice for structural steel construction and bridges Code No. 205(Min Dec #279/2001) design in STAAD. The design philosophy and procedural logistics for member selection and code checking are based upon the principles of allowable stress design. Two major failure modes are recognized: failure by overstressing, and failure by stability considerations. The flowing sections describe the salient features of the allowable stresses being calculated and the stability criteria being used. Members are proportioned to resist the design loads without exceeding the allowable stresses and the most economic section is selected on the basis of least weight criteria. The code checking part of the program checks stability and strength requirements and reports the critical loading condition and the governing code criteria. It is generally assumed that the user will take care of the detailing requirements like provision of stiffeners and check the local effects such as flange buckling and web crippling.

6B.2 Allowable Stresses The member design and code checking in STAAD are based upon the allowable stress design method as per Egyptian Code No. 205, It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. It would not be possible to describe every aspect of Egyptian Code: 205 in this

Steel Design Per Egyptian Code # 205

6-10

Section 6B

manual. This section, however, will discuss the salient features of the allowable stresses specified by Egyptian Code: 205 and implemented in STAAD. Appropriate sections of Egyptian Code: 205 will be referenced during the discussion of various types of allowable stresses.

6B.2.1 Axial Stress Tensile Stress The allowable tensile stress, as calculated in STAAD as per Egyptian Code: 205 is described below. The estimated stress on the net effective sectional area in various members, multiplied by the appropriate factor of safety shall not exceed minimum guaranteed yield stress of the material. The permissible stress in axial tension,  at in MPa on the net effective area of the sections shall not exceed: Clause: 2.6.2 F t = 0.58 f y where, fy

= minimum yield stress of steel in Mpa

Compressive Stress Allowable compressive stress on the gross section of axially loaded compression members shall not exceed the permissible stress calculated based on the following formula: (Clause: 2.6.4) F c = 0.58F y 

(0.58F y  0.75) 4

10 For all grade of steel: For  = kl/r  100 F c = 7500/ 2

where,

2

Section 6B

Fc = Permissible stress in axial compression, in Mpa fy = Yield stress of steel, in Mpa =l/r = Slenderness ratio of the member, ratio of the effective length to appropriate radius of gyration

6B.2.2 Bending Stress The allowable bending stress in a member subjected to bending is calculated based on the following formula: (Clause: 2.6.5) The laterally unsupported length (Lu) of the compression flange is limited by 20b f Lu  fy F bt or F bc = 0.64 fy Clause 2.6.5.5 Tension F bt F bt = 0.58 F y Clause 2.6.5.5 Compression F bc I.

Compression flange is braced laterally at intervals exceeding L u , the allowable bending stress in compression F bc will be taken as follows. i.

for shallow thick flanged sections, wh ere approximately t f Lu  4, the lateral tensional buckling stress is governed bf d by the torsion strength given by: 800 Fltb1  C b  0.58F y L ud /A f

ii. For Deep flanged sections, where approximately t f Lu  0.4, the lateral torsional buckling stress governed bf d by the buckling strength given by:

6-11


6-12

Section 6B

a. When Lu / rT  84

Cb then Fy

F ltb2 = 0.58 Fy b. When

84

Cb Cb  Lu / rT  188 Fy Fy

Lu / rT 2 F y  F ltb2 =  0.64  1.176 105C b  c. When Lu / rT  188 F ltb2

1200

Lu / rT 2

then

  F y  0.58F y  

Cb then Fy

C b  0.58F y

where, L u = Effective laterally unsupported length of compression flange. k = Effective length factor r T = radius of gyration about minor axis of a section compressing the compression web area (in cms) b f = Compression flange width d = Total depth C b = Coefficient depending on the type of load and support conditions as given in table 2.2 II.

Compression on extreme fibers of channels bent about their major axis  800  F ltb =  C b  0.58F y  Lu .d / A f  where, F bt = Bending stress in tension F bc = Bending stress in compression f y = Yield stress of steel, in MPa

Section 6B

6-13

6B.2.3 Shear Stress Allowable shear stress calculations are based on Section 2.6.3 of Egyptian code 205. For shear on the web, the gross section taken into consideration consists of the product of the total depth and the web thickness. q all  0.35 F y where, q all = Allowable shear stress

6B.2.4 Combined Stress Members subjected to both axial and bending stresses are proportioned accordingly to following Axial Compression and Bending All the members subjected to bending and axial compression are required to satisfy the equation of section 2.6.7.1 f bcy f ca f  bcx A1  A2  1.0 Fc Fbcx Fbcy

where, A1 

f ca

C mx  f 1  ca  f Ex 

   

,

A2 

C my  1  f ca  f Ey 

   

= Actual compression stress

Fc = Allowable compressive stress, clause 2.6.4. f f bcx bcy = Actual Bending stress about x and y-axes respectively. Fbcx,Fbcy = Allowable compressive bending stress, clause 2.6.5. FEx,FEy = Euler stress in t/cm2 Cm = Moment modification factor


6-14

Section 6B

Axial Tension and Bending All the members subject to bending and axial tension are required to satisfy the equation of section 2.6.7.2 f bty f ta f  btx   1.0 Ft Fbtx Fbty

6B.3 Stability Requirements Slenderness ratios are calculated for all members and checked against the appropriate maximum values. Table 5.1 of Egyptian code #205: summarizes the maximum slenderness ratios for different types of members. In STAAD implementation of Egyptian code #205, appropriate maximum slenderness ratio can be provided for each member. If no maximum slenderness ratio is provided, compression members will be checked against a maximum value of 180 and tension members will be checked against a maximum value of 300

6B.4 Code Checking The purpose of code checking is to verify whether the specified section is capable of satisfying applicable design code requirements. The code checking is based on the Egyptian code #205 requirements. Forces and moments at specified sections of the members are utilized for the code checking calculations. Sections may be specified using the BEAM parameter or the SECTION command. If no sections are specified, the code checking is based on forces and moments at the member ends. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start) and magnitudes of the governing forces and moments are also printed out.

Section 6B

6B.5 Member Selection STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, that is, the lightest section, which satisfies the applicable code requirements. The section selected will be of the same type (I-Section, Channel etc.) as originally specified by the user. Member selection may be performed with all types of steel sections and user provided tables. Selection of members, whose properties are originally provided from user specified table, will be limited to sections in the user provided table. Member selection can not be performed on members whose cross sectional properties are specified as PRISMATIC. The process of MEMBER SELECTION may be controlled using the parameters listed in Table 13B.1. It may be noted that the parameters DMAX and DMIN may be used to specify member depth constraints for selection. If PROFILE parameter is provided, the search for the lightest section is restricted to that profile. Up to three (3) profiles may be provided for any member with a section being selected from each one.

6B.6 Tabulated Results of Steel Design For code checking or member selection, the program produces the result in a tabulated fashion as well as step by step procedure.

6-15


6-16

Section 6B

Section 6B

6-17

Table 6B.1 Egyptian Steel Design – Code #205 Parameters Parameter Name FYLD

Default Value 250 MPA (36.25 KSI)

Description Yield strength of steel.

NSF

1.0


SSY

0.0

0.0 = Sidesway in local y-axis. 1.0 = No sidesway

SSZ

0.0

Same as above except in local z-axis.

CMY CMZ

0.85 for sidesway and calculated for no sidesway

Cm value in local y & z axes

180 (Comp. Memb.)

Allowable Kl/r for slenderness calculations for compression members.

TMAIN

300 (Tension Memb)

Allowable Kl/r for slenderness calculations for tension members.

DMAX

100.0 cm.

Maximum allowable depth.

DMIN

0.0 cm.

Minimum allowable depth.

RATIO

1.0

Permissible ratio of the actual to allowable stresses.

3.0

0.0 = design only for end moments and those at locations specified by the SECTION command. 1.0 = calculate section forces at twelfth points along the beam, design at each intermediate location and report the critical location where ratio is maximum.

MAIN

BEAM

PROFILE DFF

-

Search for the lightest section for the profile mentioned.


"Deflection Length" / Maxm. allowable local deflection

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD w orks for all codes.


6-18

Section 6B

Section 7

French Codes

A‟lkjdfl‟akjsfd

7-1

Concrete Design Per B.A.E.L.

Section

7A

7A.1 Design Operations STAAD has the capabilities for performing design of concrete beams, columns and slabs according to B.A.E.L. - 1983. Given the width and depth (or diameter for circular columns) of a section, STAAD will calculate the required reinforcing to resist the various input loads.

7A.2 Design Parameters The program contains a number of parameters which are needed to perform design per B.A.E.L. These parameters not only act as a method to input required data for code calculations but give the engineer control over the actual design process. Default values, of commonly used numbers in conventional design practice, have been used for simplicity. Table 5A.1 contains a complete list of available parameters and their default values.

7A.3 Slenderness Effects and Analysis Consideration STAAD provides the user two methods of accounting for the slenderness effect in the analysis and design of concrete members. The first method is a procedure which takes into account second order effects. Here, STAAD accounts for the secondary moments, due to axial loads and deflections, when the PDELTA ANALYSI S command is used. STAAD, after solving for the joint displacements of the structure, calculates the additional moments induced in the structure. Therefore, by using PDELTA


7-2

Section 7A

ANALYSIS, member forces are calculated which will require no user modification before beginning member design. The second method by which STAAD allows the user to account for the slenderness effect is through user supplied moment magnification factors. Here the user approximates the additional moment by supplying a factor by which momen ts will be multiplied before beginning member design.


UNIT MM MEMBER PROPERTIES 1 3 to 7 9 PRISM YD 450 ZD 300. 11 13 PR YD 300. In the above input, the first set of members are rectangular (450 mm depth and 300 mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with a 300 mm diameter. Note that area (AX) is not provided for these members. If shear areas (AY & AZ) are to be considered in analysis, the user may provide them along with YD and ZD. Also note that moments of inertia may be provi ded, but if not provided, the program will calculate values from YD and ZD.

Section 7A

7-3

7A.5 Beam Design Beam design includes both flexure and shear. For both types of beam action, all active beam loadings are scanned to create moment and shear envelopes, and locate critical sections. The total number of sections considered is twelve, unless that number is redefined with the NSECTION parameter. From the critical moment values, the required positive and negative bar pattern is developed, with cut-off lengths calculated to include required development length. Shear design includes critical shear values plus torsional moments. From these values, stirrup sizes are calculated with proper spacing. The stirrups are assumed to be U-shaped for beams with no torsion, and closed hoops for beams subject to torsion. Table 7A.1 French Concrete Design Parameters Parameter Name FYMAIN FYSEC FC CLEAR

MINMAIN

Default Value

Description

* 300 N/mm2 * 300 N/mm * 30 N/mm * 20 mm

8 mm

2

2

Yield Stress for main reinforcing steel. Yield Stress for secondary reinforcing steel. Concrete Yield Stress. Clearance of reinforcing bar. Value is automatically set to 20 mm for C35 and higher. Minimum main reinforcement bar size. (8mm - 60mm).

MINSEC

8 mm

Minimum secondary reinforcement bar size. (8mm - 60mm).

MAXMAIN

50 mm

Maximum main reinforcement bar size. (8mm - 60mm).

SFACE

*0.0

Face of support location at start of beam. (Only considers shear - use MEMBER OFFSET for bending).


7-4

Section 7A

Table 7A.1 French Concrete Design Parameters Parameter Name

Default Value

Description

EFACE

*0.0

Face of Support Location at end of beam. (Note: Both SFACE and EFACE are input as positive numbers.).

TRACK

0.0

Critical Moment will not be printed out with beam design report. A value of 1.0 will mean a print out.

MMAG

1.0

A factor by which the design moments will be magnified.

NSECTION

10


WIDTH

ZD

Width of the concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.

DEPTH

YD

Depth of concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. * These values must be provided in the units the user is currently using for input.

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE FRENCH FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEM 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 SFACE 100 MEMB 7 TO 9 EFACE 100 MEMB 7 TO 9 TRACK 1.0 MEMB 2 TO 6

Section 7A

TRACK 2.0 MEMB 7 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

7A.6 Column Design Columns are designed for axial force and biaxial moments at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement i s called the critical load. Column design is done for square, rectangular and circular sections. For rectangular and square sections, the reinforcement is always assumed to be equally distributed on each side. That means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE FRENCH FYMAIN 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MMAG 1.5 MEMB 4 5 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN

7A.7 Slab/Wall Design Slab and walls are designed per BAEL 1983 specifications. To design a slab or wall, it must be modeled using finite elements.

7-5


7-6

Section 7A

The command specifications are in accordance with Ch apter II, section 6.40. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Chapter 2 of the Technical Reference Manual). The reinforcement required to resist Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist My moment is denoted as transverse reinforcement. The parameters FYMAIN, FC, and CLEAR listed in Table 5A.1 are relevant to slab design. Other parameters mentioned in Table 5A.1 are not applicable to s lab design. Z Y My

X Mx TRANS. My

Mx LONG.

Example of Input Data for Slab/Wall Design UNIT NEWTON MMS START CONCRETE DESIGN CODE FRENCH FYMAIN 415 ALL FC 25 ALL CLEAR 40 ALL DESIGN ELEMENT 15 TO 20 END CONCRETE DESIGN

7-7

Steel Design Per the French Code

Section

7B

7B.1 General Comments STAAD implementation of French Steel Design is based on Centre Technique Industriel de la Construction Metallique publication entitled "Design Rules for Structural Steelwork." The design philosophy em bodied in this specification is based on the concept of limit state design. Structures are designed and proportioned according to the limit states of which they would become unfit for their intended use. Two major categories of limit states are recognized: ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability; that in serviceability is deflection. Appropriate load and resistance factors are used so that uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned to resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria, as augmented by the designer in specification of allowable member depths, desired section type, or other related parameters. The code checking portion of the program verifies that code requirements for each selected section are met and also identifies the governing criteria.

Steel Design per the French Code

7-8

Section 7B

The following sections describe the salient features of STAAD implementation of "Design Rules for Structural Steelwork." A detailed description of the design process, along with its underlying concepts and assumptions, is available in the specification document.

7B.2 Basis of Methodology The "Design Rules for Structural Steelwork (Revision 80)" permits the usage of elastic analysis. Thus, in STAAD, linear elastic analysis method is used to obtain the forces and moments in the members. However, strength and stability considerations are based on the principles of plastic behaviour. Axial compression buckling and lateral torsional buckling are taken into consideration for calculation of axial compression resistance and flexural resistance of members. Slenderness calculations are made and overall geometric stability is checked for all members.

7B.3 Member Capacities The member strengths are calculated in STAAD according to the procedures outlined in section 4 of this specification. Note that the program automatically considers co-existence of axial force, shear and bending in calculating section capacities. For axial tension capacity, procedures of section 4.2 are followed. For axial compression capacity, formulas of section 5.3 are used. Moment capacities about both axes are calculated using the procedures of sections 4.5 and 4.6. Lateral torsional buckling is considered in calculating ultimate twisting moment per section 5.22 of the specification. The parameter UNL (see Table 6B.1) must be used to specify the unsupported length of the compression flange for a laterally unsupported member. Note that this length i s also referred to as twisting length.

Section 7B

7B.4 Combined Axial Force and Bending The procedures of sections 4.55 and 5.32 are implemented for interaction of axial forces and bending. Appropriate interaction equations are used and the governing criterion is determined.

7B.5 Design Parameters The design parameters outlined in Table 6B.1 may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program, thus allowing the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected as frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure.

7B.6 Code Checking and Member Selection Both code checking and member selection options are available in STAAD implementation of CM 66 (Revn. 80). For general information on these options, refer to Chapter II, sections 3.4 and 3.5. For information on specification of these commands, refer to Chapter II, and section 6.46.

7B.7 Tabulated Results of Steel Design Results of code checking and member selection are presented in the output file in a tabular format. Please note the following: COND CRITIQUE refers to the section of the CM 66 (Revn. 80) specification which governed the design.

7-9


7-10

Section 7B

If the TRACK parameter is set to 1.0, calculated member capacities will be printed. The following is a detailed description of printed items: PC TR MUZ MUY VPZ VPY

= = = = = =

Member Member Member Member Member Member

Compression Capacity Tension Capacity Moment Capacity (about z-axis) Moment Capacity (about y-axis) Shear Capacity (z-axis) Shear Capacity (y-axis)

Table 7B.1 French Steel Design Parameters Parameter Name

Default Value

Description

KY

1.0

K value for axial compression buckling about local Y-axis. Usually, this is the minor axis.

KZ

1.0

K value for axial compression buckling about local Z-axis. Usually, this is the major axis.

LY

Member Length

Length to calculate slenderness ratio about Y-axis for axial compression.

LZ

Member Length

Length to calculate slenderness ratio about Z-axis for axial compression.

FYLD

250.0 MPa


NSF

1.0

UNL

Member Length

UNF

1.0

Same as above provided as a fraction of member length.

TRACK

0.0

0.0 = Suppress printing of all design strengths. 1.0 = Print all design strengths.

DMAX

100.0 cm.

Maximum allowable depth (used in member selection).

DMIN

0.0 cm.

Minimum allowable depth (used in member selection).

RATIO

1.0

Net section factor for tension members. Unsupported length of compression flange for calculating moment resistance.

Permissible ratio of actual load effect and design strength.

Section 7B

Table 7B.1 French Steel Design Parameters Parameter Name BEAM

Default Value 0.0

Description 0.0 = design only for end moments and those at locations specified by SECTION command. 1.0 = calculate moments at tenth points along the beam, and use maximum Mz for design.

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. STAAD contains a broad set of facilities for designing structural members as individual components of an analyzed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are:   

Specify the members and the load cases to be considered in the design. Specify whether to perform code checking or member selection. Specify design parameter values, if different from the default values.

These operations may be repeated by the user any n umber of times depending upon the design requirements. Currently STAAD supports steel design of wide flange, S, M, HP shapes, angle, double angle, channel, double channel, beams with cover plate, composite beams and code checking of prismatic properties.

7-11


7-12

Section 7B

Sample Input data for Steel Design UNIT METER PARAMETER CODE FRENCH NSF 0.85 ALL UNL 10.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL

7B.8 Built-in French Steel Section Library The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members. An example of the member property specification in an input file is provided at the end of this section. A complete listing of the sections available in the built -in steel section library may be obtained by using the tools of the graphical user interface. Following are the descriptions of different types of sections.

Section 7B

IPE Shapes These shapes are designated in the following way.

10 15 TA ST IPE140 20 TO 30 TA ST IPEA120 33 36 TO 46 BY 2 TA ST IPER180 HE shapes HE shapes are specified as follows.

3 5 TA ST HEA120A 7 10 TA ST HEM140 13 14 TA ST HEB100 IPN Shapes The designation for the IPN shapes is similar to that for the IPE shapes.

25 TO 35 TA ST IPN200 23 56 TA ST IPN380 T Shapes Tee sections are not input by their actual designations, but instead by referring to the I beam shapes from which they are cut. For example,

1 5 TA T IPE140 2 8 TA T HEM120

7-13


7-14

Section 7B

U Channels Shown below is the syntax for assigning 4 different names of channel sections.

1 TO 5 TA ST UAP100 6 TO 10 TA ST UPN220 11 TO 15 TA ST UPN240A 16 TO 20 TA ST UAP250A Double U Channels Back to back double channels, with or without a spacing between them, are available. The letter D in front of the section name will specify a double channel.

11 TA D UAP150 17 TA D UAP250A SP 0.5 In the above set of commands, member 11 is a back to back double channel UAP150 with no spacing in between. Member 17 is a double channel UAP250A with a spacing of 0.5 length units between the channels. Angles Two types of specification may be used to describe an angle. The standard angle section is specified as follows:

16 20 TA ST L30X30X2.7 The above section signifies an angle with legs of length 30mm and a leg thickness of 2.7mm. This specification may be used when the local Z axis corresponds to the z-z axis specified in Chapter 2. If the local Y axis corresponds to the z-z axis, type specification "RA" (reverse angle) should be used instead of ST.

17 21 TA RA L25X25X4

Section 7B

22 24 TA RA L100X100X6.5 Note that if the leg thickness is a round number such as 4.0, only the number 4 appears in the section name, the decimal part is not part of the section name. Double Angles Short leg back to back or long leg back to back double angles can be specified by means of input of the words SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose.

33 35 TA SD L30X20X4 SP 0.6 37 39 TA LD L80X40X6 43 TO 47 TA LD L80X80X6.5 SP 0.75 Tubes (Rectangular or Square Hollow Sections) Section names of tubes, just like angles, consist of the depth, width and wall thickness as shown below.

64 78 TA ST TUB50252.7 66 73 TA ST TUB2001008.0 Members 64 and 78 are tubes with a depth of 50mm, width of 25mm and a wall thickness of 2.7mm. Members 66 and 73 are tubes with a depth of 200mm, width of 100mm and a wall thickness of 8.0mm. Unlike angles, the ".0" in the thickness is part of the section name. Tubes can also be input by their dimensions instead of by their table designations. For example,

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5

7-15


7-16

Section 7B

is a tube that has a depth of 8 length units, width of 6 length units, and a wall thickness of 0.5 length units. Only code checking, no member selection, will be performed for TUBE sections specified i n this way. Pipes (Circular Hollow Sections) To designate circular hollow sections, use PIP followed by numerical value of the diameter and thickness of the section in mm omitting the decimal portion of the value provided for the diameter. The following example illustrates the designation.

8 TO 28 TA ST PIP422.6 3 64 78 TA ST PIP21912.5 Members 8 to 28 are pipes 42.4mm in dia, having a wall thickness of 2.6mm. Members 3, 64 and 78 are pipes 219.1mm in dia, having a wall thickness of 12.5mm. Circular hollow sections may also be provided by specifying the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0 specifies a pipe with outside dia. of 25 length units and inside dia. of 20 length units. Only code checking, no member selection will be performed if this type of specification is used.

SAMPLE FILE CONTAINING FRENCH SHAPES STAAD SPACE UNIT METER KN JOINT COORD 1 0 0 0 15 140 0 0 MEMB INCI 1 1 2 14

Section 7B

UNIT CM MEMBER PROPERTIES FRENCH * IPE SHAPES 1 TA ST IPEA120 * IPN SHAPES 2 TA ST IPN380 *HE SHAPES 3 TA ST HEA200 * T SHAPES 4 TA T HEM120 * U CHANNELS 5 TA ST UAP100 * DOUBLE U CHANNELS 6 TA D UAP150 SP 0.5 * ANGLES 7 TA ST L30X30X2.7 * REVERSE ANGLES 8 TA RA L25X25X4 * DOUBLE ANGLES - SHORT LEGS BACK * TO BACK 9 TA SD L30X20X4 SP 0.25 * DOUBLE ANGLES - LONG LEGS BACK * TO BACK 10 TA LD L80X40X6 SP 0.75 * TUBES (RECTANGULAR OR SQUARE * HOLLOW SECTIONS) 11 TA ST TUB50252.7 * TUBES (RECTANGULAR OR SQUARE * HOLLOW SECTIONS) 12 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 * PIPES (CIRCULAR HOLLOW SECTIONS) 13 TA ST PIP422.6 * PIPES (CIRCULAR HOLLOW SECTIONS) 14 TA ST PIPE OD 25.0 ID 20.0 PRINT MEMB PROP FINI

7-17


7-18

Section 7B

Section 8

German Codes

Aslkdfj;alskjdf‟

8-1

Concrete Design Per DIN 1045 Section

8A

8A.1 Design Operations STAAD has the capabilities of performing concrete design based on the DIN 1045 - November 1989. Slab design is also available but this follows the requirements of Baumann, Munich, which is the basis for Eurocode 2. Design for a member involves calculation of the amount of reinforcement required for the member. Calculations are based on the user specified properties and the member forces obtained from the analysis. In addition, the details regarding placement of the reinforcement on the cross section are also reported in the output.

8A.2 Section Types for Concrete Design The following types of cross sections for concrete members can be designed. For Beams - Prismatic (Rectangular & Square) For Columns - Prismatic (Rectangular, Square and Circular)


Concrete Design Per DIN 1045

8-2

Section 8A

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350. In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350mm diameter. It is absolutely imperative that the user not provide the cross section area (AX) as an input.

8A.4 Slenderness Effects and Analysis Considerations Slenderness effects are extremely important in designing compression members. There are two options by which the slenderness effect can be accommodated. The first method is equivalent to the procedure presented in DIN 1045 17.4.3/17.4.4 which is used as the basis for commonly used design charts considering e/d and sk/d for conditions where the slenderness moment exceeds 70. This method has been adopted in the column design in STAAD per the DIN code. The second option is to compute the secondary moments through an analysis. Secondary moments are caused by the interaction of the axial loads and the relative end displacements of a member. The axial loads and joint displacements are first determined from an elastic stiffness analysis and the secondary moments are then evaluated. To perform this type of analysis, use the command PDELTA ANALYSIS instead of PERFORM ANALYSIS in the input file. The user must note that to take advantage of this analysis, all the combinations of loading must be provi ded as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during

Section 8A

8-3

the P-delta analysis based on the deflections. Also, note that the proper factored loads (like 1.5 for dead load etc.) should be provided by the user. STAAD does not factor the loads automatically. The column is designed for the total moment which is the sum of the primary and secondary forces. The secondar y moments can be compared to those calculated using the charts of DIN 1045.

8A.5 Beam Design Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are prescanned to identify the critical load cases at differen t sections of the beams. The total number of sections considered is 13 (e.g. 0., .1, .2, .25, .3, .4, .5, .6, .7, .75, .8, .9 and 1). All of these sections are scanned to determine the design force envelopes. Design for Flexure Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections is designed to resist these critical sagging and hogging moments. Currently, design of singly reinforced sections only is permitted. If the section dimensions are inadequate as a singly reinforced section, such a message will be printed in the output. Flexural design of beams is performed in two pa sses. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexural design is performed again in a second pass taking into account the changed effective depths of sections calculated on the basis of reinforcement provided after the preliminary design. Final provisions of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per the DIN code. Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the


8-4

Section 8A

detailer taking into account of other practical considerations), the user has the choice of printing reinforcements provided by STAAD at 13 equally spaced sections from which the final detailed drawing can be prepared. Design for Shear and Torsion Shear design in STAAD conforms to the specifications of section 17.5 of DIN 1045. Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear and torsional design is performed at the start and end sections of the member at a distance "d" away from the node of the member where "d" is the effective depth calculated from flexural design. The maximum shear forces from amongst the active load cases and the associated torsional moments are used in the design. The capacity of the concrete in shear and torsion is determined at the location of design and the balance, if any, is carried by reinforcement. It is assumed that no bent-up bars are available from the flexural reinforcement to carry and "balance" shear. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections. Stirrups are assumed to be U-shaped for beams with no torsion, and closed hoops for beams subject to torsion.

Example of Input Data for Beam Design UNIT NEWTON MMS START CONCRETE DESIGN CODE GERMAN FYMAIN 415 ALL FYSEC 415 ALL FC 35 ALL CLEAR 25 MEM 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN

Section 8A

8A.6 Column Design Columns are designed for axial forces and biaxi al moments at the ends. All active load cases are tested to calculate reinforcement. The loading which yields maximum reinforcement is called the critical load. The requirements of DIN 1045-figure 13, for calculating the equilibrium equations for rectangular and circular sections from first principles, is implemented in the design. The user has control of the effective length (sk) in each direction by using the ELZ and ELY parameters as described on Table 8A.1. This means that the slenderness will be evalua ted along with e/d to meet the requirements of DIN 1045 section 17.4.3 and 17.4.4. Column design is done for square, rectangular and circular sections. Square and rectangular columns are designed with reinforcement distributed on all four sides equally. T hat means the total number of bars will always be a multiple of four (4). This may cause slightly conservative results in some cases. The TRACK parameter may be used to obtain the design details in various levels of descriptivity.

Example of Input Data for Column Design UNIT NEWTON MMS START CONCRETE DESIGN CODE GERMAN FYMAIN 415 ALL FC 35 ALL CLEAR 25 MEMB 2 TO 6 MAXMAIN 40 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN

8-5


8-6

Section 8A

8A.7 Slab Design To design a slab, it must first be modeled using finite elements and analysed. The command specifications are in accordance with Chapter 2 and Chapter 6 of the Technical Reference Manual. Slabs are designed to specifications as described by BAUMANN of MUNICH which is the basis for Eurocode 2. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Chapter 2 of the Technical Reference Manual). The reinforcement required to resist the Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist the My moment is denoted as transverse reinforcement. The following parameters are those applicable to slab design: 1. FYMAIN 2. FC 3. CLEAR

4. SRA

Yield stress for all reinforcing steel Concrete grade Distance from the outer surface of the elemen t to the edge of the bar. This is considered the same on both top and bottom surfaces of the element. Parameter which denotes the angle of direction of the required transverse reinforcement relative to the direction of the longitudinal reinforcement for the calculation of BAUMANN design forces.

The other parameters shown in Table 7A.1 are not applicable to slab design. BAUMANN equations If the default value of zero is used, the design will be based on Mx and My forces which are obtained from the ST AAD analysis. The SRA parameter (Set Reinforcement Angle) can be manipulated to introduce resolved BAUMANN forces into the design replacing the pure Mx and My moments. These new design moments allow the Mxy moment to be considered when designing the section, resolved as an axial force. Orthogonal or skew reinforcement may

Section 8A

8-7

be considered. If SRA is set to -500, an orthogonal layout will be assumed. If however a skew is to be considered, an angle is given in degrees measured from the local element X axis anticlockwise (positive). The resulting Mx* and My* moments are calculated and shown in the design format. The design of the slab considers a fixed bar size of 10mm in the longitudinal direction and 8mm in the transverse. The longitudinal bar is the layer closest to the slab exterior face.

8A.8 Design Parameters The program contains a number of parameters which are needed to perform the design. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 8A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter an d Newton before performing the concrete design. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 8A.1 German Concrete Design Parameters Parameter Name FYMAIN

Default Value 420 N/mm

2

Description Yield Stress for main reinforcement (For slabs 2 it is 500 N/mm for both directions)

FYSEC

420N/mm2

Yield Stress for secondary reinforcement. Applicable to shear and torsion reinforcement in beams

FC

25N/mm2

Concrete Yield Stress/ cube strength

MINMAIN

16mm

Minimum main reinforcement bar size [Acceptable bar sizes: 6 8 10 12 14 16 20 25 32 40 50]

MINSEC

8mm

Minimum secondary reinforcement bar


8-8

Section 8A

Table 8A.1 German Concrete Design Parameters Parameter Name

Default Value

Description size. Applicable to shear and torsion reinforcement in beams.

CLEAR

25mm

Clear cover for reinforcement measured from concrete surface to closest bar perimeter.

MAXMAIN

50 mm

Maximum required reinforcement bar size. Acceptable bars are per MINMAIN above.

SFACE

0.0

Face of support location at start of beam, measured from the start joint. (Only applicable for shear - use MEMBER OFFSET for bending)

EFACE

0.0

Face of support location at end of beam, measured from the end joint. (NOTE: Both SFACE & EFACE must be positive numbers.)

TRACK

0.0

0.0 = Critical Moment will not be printed with beam design report. 1.0 = For beam gives min/max steel % and spacing. For columns gives a detailed table of output with additional moments calculated. 2.0 = For beams gives area of steel required at intermediate sections. (see NSECT)

MMAG

1.0

Factor by which design moments are magnified for column design

NSECTION

10

Number of equally-spaced sections to be considered in finding critical moment for beam design. The upper limit is 20

WIDTH

ZD

Width of concrete member. The default value is as provided as ZD in MEMBER PROPERTIES.

DEPTH

YD

Depth of concrete member. The default value is as provided as YD in MEMBER PROPERTIES.

ELY

1.0

Member length factor about local Y direction

Section 8A

8-9

Table 8A.1 German Concrete Design Parameters Parameter Name

Default Value

Description for column design

ELZ

1.0

Member length factor about local Z direction for column design

SRA

0.0

0.0 = Orthogonal reinforcement layout without considering torsional moment Mxy -slabs only -500 = Orthogonal reinforcement layout considering Mxy A = Skew angle considered in BAUMANN equations. A is the angle in degrees.


8-10

Section 8A

8-11

Steel Design Per the DIN Code

Section

8B

8B.1 General This section presents some general statements regarding the implementation of the DIN code of practice for structural steel design (DIN 18800 and DIN 4114) in STAAD. The design philosophy and procedural logistics are based on the principles of elastic analysis and allowable stress design. Facilities are available for member selection as well as code checking. Two major failure modes are recognized: failure by overstressing and failure by stability considerations. The following sections describe the salient features of the design approach. Members are proportioned to resist the design loads without exceedance of the allowable stresses or capacities and the most economical section is selected on the basis of the least weight criteria. The code checking part of the program also checks the slenderness requirements and the stability criteria. Users are recommended to adopt the following steps in performing the steel design: 1) Specify the geometry and loads and perform the analysis. 2) Specify the design parameter values if different from the default values. 3) Specify whether to perform code checking or member selection.

Steel Design per the DIN Code

8-12

Section 8B

8B.2 Analysis Methodology Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and in using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis or P-Delta analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.

8B.3 Member Property Specifications For specification of member properties of standard German steel sections, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Program User's manual.

8B.4 Built-in German Steel Section Library The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, these properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members during the analysis. An example of member property specification in an input file is provided at the end of this section.

Section 8B

A complete listing of the sections available in the built -in steel section library may be obtained using the tools of the graphical user interface. Following are the descriptions of different types of sections. IPE Shapes These shapes are designated in the following way:

20 TO 30 TA ST IPEA120 33 36 TO 46 BY 2 TA ST IPER140 HE Shapes The designation for HE shapes is similar to that for IPE shapes.

25 TO 35 TA ST HEB300 23 56 TA ST HEA160 I Shapes I shapes are identified by the depth of the section. The following example illustrates the designation.

14 15 TA ST I200

(indicates an I-section with 200mm depth)

T Shapes Tee sections are not input by their actual designations, but instead by referring to the I beam shapes from which they are cut. For example,

1 5 TA T HEA220 2 8 TA T IPE120

8-13


8-14

Section 8B

U Channels The example below provides the command for identifying two channel sections. The former (U70X40) has a depth of 70mm and a flange width of 40mm. The latter (U260) has a depth of 260mm.

11 TA D U70X40 27 TA D U260 Double Channels Back to back double channels, with or without spacing between them, are available. The letter “D” in front of the section name will specify a double channel, e.g. D U180. The spacing between the double channels is provided following the expression “SP”.

11 TA D U180 27 TA D U280 SP 0.5 (Indicates 2 channels back to back spaced at 0.5 length units) Angles Two types of specifications may be used to describe an angle. The standard angle section is specified as follows:

16 20 TA ST L20X20X2.5 The above section signifies an angle with legs of length 20mm and a leg thickness of 2.5mm. The above specification may be used when the local z-axis corresponds to the Z-Z axis specified in Chapter 2. If the local y-axis corresponds to the Z-Z axis, type specification "RA" (reverse angle) may be used.

17 21 TA RA L40X20X5

Section 8B

Double Angles Short leg back to back or long leg back to back double angles can be specified by using the word SD or LD, respectively, in front of the angle size. In case of an equal angle, either SD or LD will serve the purpose. Spacing between the angles is provided by using the word SP and the spacing value following the section name.

14 TO 20 TA SD L40X20X4 SP 0.5 21 TO 27 TA LD L40X20X4 SP 0.5 Pipes (Circular Hollow Sections) To designate circular hollow sections, use PIP followed by numerical value of the diameter and thickness of the section in mm omitting the decimal section of the value provided for diameter. The following example will illustrate the designation.

8 TO 28 TA ST PIP602.9 thickness) 3 64 67 TA ST PIP40612.5 thickness)

(60.3mm dia, 2.9mm wall (406.4mm dia, 12.5mm wall

Circular hollow sections may also be provided by specifying the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0 specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units. Only code checking and no member selection will be performed if this type of specification is used.

8-15


8-16

Section 8B

Tubes (Rectangular or Square Hollow Sections) Tube names are input by their dimensions. For example,

15 TO 25 TA ST TUB100603.6 is the specification for a tube having sides of 100mmX60mm and the wall thickness of 3.6mm. Tubes, like pipes can also be input by their dimensions (Height, Width and Thickness) instead of by their table designations.

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height of 8, a width of 6, and a wall thickness of 0.5 in current length units. Only code checking and no member selection will be performed for TUBE sections specified this way.

SAMPLE INPUT FILE CONTAINING GERMAN SHAPES STAAD SPACE UNIT METER KN JOINT COORDINATES 1 0 0 0 15 140 0 0 MEMBER INCIDENCES 1 1 2 14 UNIT CM MEMBER PROPERTIES GERMAN * IPE SHAPES 1 TA ST IPEA120 * HE SHAPES 2 TA ST HEB300 * I SHAPES 3 TA ST I200 * T SHAPES 4 TA T HEA220

Section 8B

* U CHANNELS 5 TA ST U70X40 * DOUBLE U CHANNELS 6 TA D U260 * ANGLES 7 TA ST L20X20X2.5 * REVERSE ANGLES 8 TA RA L40X20X5 * DOUBLE ANGLES - LONG LEGS BACK TO BACK 9 TA LD L40X20X4 SP 0.5 * DOUBLE ANGLES - SHORT LEGS BACK TO BACK 10 TA SD L40X20X4 SP 0.5 * PIPES 11 TA ST PIP602.9 * PIPES 12 TA ST PIPE OD 25.0 ID 20.0 * TUBES 13 TA ST TUB100603.6 * TUBES 14 TA ST TUBE DT 8.0 WT 6.0 WT 0.5 * PRINT MEMBER PROPERTIES FINISH

8B.5 Member Capacities The allowable stresses used in the implementation are based on DIN 18800 (Part 1) - Section 7. The procedures of DIN 4114 are used for stability analysis. The basic measure of member capacities are the allowable stresses on the member under various conditions of applied loading such as allowable tensile stress, allowable compressive stress etc. These depend on several factors such as cross sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Explained here is the procedure adopted in STAAD for calculating such capacities.

8-17


8-18

Section 8B

Allowable stress for Axial Tension In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension capacity of the member is calculated on the basis of the member area. STAAD calculates the tension capacity of a given member based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value, see Table 6B.1) and proceeds with member selection or code checking. Allowable stress for Axial Compression The allowable stress for members in compression is determined according to the procedure of DIN 4114 (Part 1) - Section 7. Compressive resistance is a function of the slenderness of the cross-section (Kl/r ratio) and the user may control the slenderness value by modifying parameters such as KY, LY, KZ and LZ. Allowable stress for Bending and Shear The permissible bending compressive and tensile stresses are dependent on such factors as length of outstanding legs, thickness of flanges, unsupported length of the compression flange (UNL, defaults to member length) etc. Shear capacities are a function of web depth, web thickness etc. Users may use a value of 1.0 or 2.0 for the TRACK parameter to obtain a listing of the bending and shear capacities.

8B.6 Combined Loading For members experiencing combined loading (axial force, bending and shear), applicable interaction formulas are checked at different locations of the member for all modeled loading situations. Members subjected to axial force and bending are checked using the criteria of DIN 18800 (Part 1) - Section 6.1.6. In addition, for members with compression and bending, the criteria of DIN 4114 (Part 1) - Section 10 is used. Similarly, for members with axial tension and bending, the criteria of DIN 4114 (Part 1) - Section 15 is used.

Section 8B

8B.7 Design Parameters The user is allowed complete control over the design process through the use of parameters mentioned in Table 8B.1 of this chapter. These parameters communicate design decisions from the engineer to the program. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements of the situation, some or all of these parameter values may have to be changed to exactly model the physical structure. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 8B.1 German Steel Design Parameters Parameter Name KY

Default Value

Description

1.0

K value in local y-axis. Usually, this is the minor axis.

KZ

1.0

K value in local z-axis. Usually, this is the major axis.

LY

Member Length

Length in local y-axis to calculate slenderness ratio.

LZ

Member Length

Length in local z-axis to calculate slenderness ratio.

PY

240 N/sq.mm

Strength of steel.

NSF

1.0


UNL

Member Length

Unrestrained member length in lateral torsional buckling checks.

UNF

1.0

Same as above provided as a factor of actual member length.

BEAM

0.0

Number of sections to be checked per member: 0.0 = Design only for end sections. 1.0 = Check at location of maximum MZ along member.

8-19


8-20

Section 8B

Table 8B.1 German Steel Design Parameters Parameter Name

Default Value

Description 2.0 = Check ends plus location of beam 1.0 check. 3.0 = Check at every 1/13th of the member length and report the maximum.

TRACK

0.0

Level of detail in output file: 0.0 = Output summary of results 1.0 = Output summary of results plus member capacities 2.0 = Output detailed results

RATIO

1.0

Permissible ratio of actual to allowable stresses

SGR

0.0

Grade of steel: 0.0 = St 37-2 1.0 = St 52-3 2.0 = StE 355

SBLT

0

Specify section as either rolled or built-up: 0 = Rolled 1 = Built-up

Cb

Cmm

0

Beam coefficient n, defined in Table 9: If Cb = 0, program will use n = 2.5 for rolled sections and 2.0 for welded sections.

1.0

Moment factor, Zeta, defined in Table 10: 1.0 = fixed ended member with constant moment, Zeta = 1.0 2.0 = pin ended member with UDL, Zeta = 1.12 3.0 = pin ended member with central point load, Zeta = 1.35 4.0 = fixed ended member, Zeta calculated from end moments.

DMAX

1.0 m

Maximum allowable depth during member selection

DMIN

0.0 m

Minimum required depth during member

Section 8B

8-21

Table 8B.1 German Steel Design Parameters Parameter Name

Default Value

SAME

Description selection

0.0

Control of sections to try during a SELECT process: 0.0 = Try every section of the same type as the original. 1.0 = Try only those with a similar name.

8B.8 Code Checking The purpose of code checking is to check whether the provided section properties of the members are adequate to carry the forces transmitted to it by the loads on the structure. The adeq uacy is checked per the DIN requirements. Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam, and the maximum moment about the major axis is used. When no sections are specified and the BEAM parameter is set to zero (default), design will be based on member start and end forces. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from start joint) and magnitudes of the governing forces and moments are also printed.


8-22

Section 8B

8B.9 Member Selection The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Member selection cannot be performed on TUBES, PIPES or members listed as PRISMATIC.

Sample Input data for Steel Design UNIT METER PARAMETER CODE GERMAN NSF 0.85 ALL UNL 10.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL

Section 9

Indian Codes

Ad;flaksd;lfka

9-1

Concrete Design Per IS456

Section

9A

9A.1 Design Operations STAAD has the capabilities of performing concrete design based on limit state method of IS: 456 (2000).


Prismatic (Rectangular & Square), T-Beams and L-shapes

For Columns




9-2

Section 9A

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350. 14 TO 16 PRIS YD 400. ZD 750. YB 300. ZB 200. will be done accordingly. In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350 mm diameter. The third set numbers in the above example represen ts a T-shape with 750 mm flange width, 200 width, 400 mm overall depth and 100 mm flange depth (See section 6.20.2). The program will determine whether the section is rectangular, flanged or circular and the beam or column design

9A.4 Design Parameters The program contains a number of parameters which are needed to perform design as per IS:456(2000). Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 8A.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.

9A.5 Slenderness Effects and Analysis Consideration Slenderness effects are extremely important in designing compression members. The IS:456 code specifies two options by which the slenderness effect can be accommodated (Clause 39.7).

Section 9A

One option is to perform an exact analysis which will take into account the influence of axial loads and variable moment of inertia on member stiffness and fixed end moments, the effect of deflections on moment and forces and the effect of the duration of loads. Another option is to approximately magnify design moments. STAAD has been written to allow the use of the first options. To perform this type of analysis, use the command PDELTA ANALYSIS instead of PERFORM ANALYSIS. The PDELTA ANALYSIS will accommodate all requirements of the secondorder analysis described by IS:456, except for the effects of the duration of the loads. It is felt that this effect may be safely ignored because experts believe that the effects of the duration of loads are negligible in a normal structural configuration. Although ignoring load duration effects is somewhat of an approximation, it must be realized that the approximate evaluation of slenderness effects is also an approximate method. In this method, additional moments are calculated based on empirical formula and assumptions on sidesway (Clause 39.7.1 and 39.7.1.1,IS: 456 - 2000). Considering all these information, a PDELTA ANALYSIS, as performed by STAAD may be used for the design of concrete members. However the user must note, to take advantage of this analysis, all the combinations of loading must be provided as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during the P-delta analysis based on the deflections. Also note that the proper factored loads (like 1.5 for dead load etc.) should be provided by user. STAAD does not factor the loads automatically.

9A.6 Beam Design Beams are designed for flexure, shear and torsion. If required the effect the axial force may be taken into consideration. For all

9-3


9-4

Section 9A

these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13( e.g. 0.,.1,.2,.25,.3,.4,.5,.6,.7,. 75,.8,.9 and 1). All of these sections are scanned to determine the design force envelopes. Design for Flexure Maximum sagging (creating tensile stress at the bottom face of the beam) and hogging (creating tensile stress at the top face) moments are calculated for all active load cases at each of the above mentioned sections. Each of these sections is designed to resist both of these critical sagging and hogging moments. Where ever the rectangular section is inadequate as singly reinforced section, doubly reinforced section is tried. However, presently the flanged section is designed only as singly reinforced section under sagging moment. It may also be noted all flanged sections are automatically designed as rectangular section under hogging moment as the flange of the beam is ineffective under hogging moment. Flexural design of beams is performed in two passes. In the first pass, effective depths of the sections are determined with the assumption of single layer of assumed reinforcement and reinforcement requirements are calculated. After the preliminary design, reinforcing bars are chosen from the internal database in single or multiple layers. The entire flexure design is per formed again in a second pass taking into account of the changed effective depths of sections calculated on the basis of reinforcement provide after the preliminary design. Final provisions of flexural reinforcements are made then. Efforts have been made to meet the guideline for the curtailment of reinforcements as per IS:456 -2000 (Clause 26.2.3). Although exact curtailment lengths are not mentioned explicitly in the design output (finally which will be more or less guided by the detailer taking into account of other practical consideration), user has the choice of printing reinforcements provided by STAAD at 11 equally spaced sections from which the final detail drawing can be prepared.

Section 9A

Design for Shear Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear design are performed at 11 equally spaced sections (0.to 1.) for the maximum shear forces amongst the active load cases and the associated torsional moments. Shear capacity calculation at different sections with out the shear reinforcement is based on the actual tensile reinforcement provided by STAAD program. Two-legged stirrups are provided to take care of the balance shear forces acting on these sections. As per Clause 40.5 of IS:456-2000 shear strength of sections (< 2d where d is the effective depth) close to support has been enhanced, subjected to a maximum value of  c ma x . Beam Design Output The default design output of the beam contains flexural and shear reinforcement provided at 5 equally spaced (0,.25,.5,.75 and 1.) sections along the length of the beam. User has option to get a more detail output. All beam design outputs are given in IS units. An example of rectangular beam design output with the default output option (TRACK 0.0) is presented below:

9-5


9-6

Section 9A ============================================================================ B E A M N O. 12 D E S I G N R E S U L T S M20 LENGTH: 4000.0 mm

Fe415 (Main) SIZE:

Fe415 (Sec.)

250.0 mm X 350.0 mm

COVER: 30.0 mm

DESIGN LOAD SUMMARY (KN MET) ---------------------------------------------------------------------------SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR (in mm) | P MZ MX Load Case | VY MX Load Case ---------------------------------------------------------------------------0.0 | 0.00 0.00 0.00 4 | 29.64 1.23 4 | 0.00 -25.68 1.23 4 | 400.0 | 0.00 0.00 0.00 4 | 27.97 1.23 4 | 0.00 -16.05 1.23 4 | 800.0 | 0.00 0.00 0.00 4 | 25.12 1.23 4 | 0.00 -7.17 1.23 4 | 1200.0 | 0.00 0.97 0.49 5 | 21.11 1.23 4 | 0.00 -0.14 1.32 6 | 1600.0 | 0.00 6.77 1.23 4 | 15.93 1.23 4 | 0.00 0.00 0.00 4 | 2000.0 | 0.00 11.06 1.23 4 | 9.59 1.23 4 | 0.00 0.00 0.00 4 | 2400.0 | 0.00 13.04 1.23 4 | 2.08 1.23 4 | 0.00 0.00 0.00 4 | 2800.0 | 0.00 12.45 1.23 4 | -5.43 1.23 4 | 0.00 0.00 0.00 4 | 3200.0 | 0.00 9.55 1.23 4 | -11.77 1.23 4 | 0.00 0.00 0.00 4 | 3600.0 | 0.00 4.73 1.23 4 | -16.95 1.23 4 | 0.00 0.00 0.00 4 | 4000.0 | 0.00 0.00 0.00 4 | -25.48 1.23 4 | 0.00 -17.36 1.23 4 | ---------------------------------------------------------------------------SUMMARY OF REINF. AREA (Sq.mm) ---------------------------------------------------------------------------SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ---------------------------------------------------------------------------TOP 259.04 161.29 0.00 0.00 176.31 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) BOTTOM 0.00 160.78 160.78 160.78 0.00 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) ---------------------------------------------------------------------------SUMMARY OF PROVIDED REINF. AREA ---------------------------------------------------------------------------SECTION 0.0 mm 1000.0 mm 2000.0 mm 3000.0 mm 4000.0 mm ---------------------------------------------------------------------------TOP 4-10Ø 3-10Ø 2-10Ø 2-10Ø 3-10Ø REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) BOTTOM REINF.

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

2-12Ø 1 layer(s)

SHEAR 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø 2 legged 8Ø REINF. @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c @ 100 mm c/c ---------------------------------------------------------------------------============================================================================

Section 9A

9A.7 Column Design Columns are designed for axial forces and biaxial moments at the ends. All active load cases are tested to calculate reinforcement. The loading which yield maximum reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. By default, square and rectangular columns and designed with reinforcement distributed on each side equally for the sections under biaxial moments and with reinforcement distributed equally in two faces for sections under uniaxial moment. User may change the default arrangement of the reinforcement with the help of the parameter RFACE (see Table 8A.1). Depending upon the member lengths, section dimensions and effective length coefficients specified by the user STAAD automatically determine the criterion (short or long) of the column design. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by IS:456 have been taken care of in the column design of STAAD. Default clear spacing between main reinforcing bars is taken to be 25 mm while arrangement of longitudinal bars. Column Design Output Default column design output (TRACK 0.0) contains the reinforcement provided by STAAD and the capacity of the section. With the option TRACK 1.0, the output contains intermediate results such as the design forces, effective length coefficients, additional moments etc. A special output TRACK 9.0 is introduced to obtain the details of section capacity calculations. All design output is given in SI units. An example of a long column design (Ref.Example9 of SP:16, Design Aids For Reinforced Concrete to IS:456-1978) output (with option TRACK 1.0) is given below.

9-7


9-8

Section 9A ============================================================================ C O L U M N N O. 1 D E S I G N R E S U L T S M20 LENGTH:

3000.0 mm

Fe415 (Main) CROSS SECTION:


5

Fe415 (Sec.)

250.0 mm dia.

COVER: 40.0 mm

BRACED LONG COLUMN


:

62.0


: :

About Z 2.21 1.24

About Y 32.29 1.24


: : : :

12.00 1.12 1.00 1.12

12.00 1.12 1.00 1.12


:

3.32

33.40

REQD. STEEL AREA : 1822.71 Sq.mm. MAIN REINFORCEMENT : Provide 17 - 12 dia. (3.92%, 1922.65 Sq.mm.) (Equally distributed) TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 190 mm c/c SECTION CAPACITY (KNS-MET) -------------------------Puz : 992.70 Muz1 :

36.87

Muy1 :

36.87

INTERACTION RATIO: 1.00 (as per Cl. 38.6, IS456) ============================================================================

Section 9A

Table 9A.1 Indian Concrete Design IS456 Parameters Parameter Name

Default Value

Description

FYMAIN

415 N/mm2

Yield Stress for main reinforcing steel.

FYSEC

415 N/mm2

Yield Stress for secondary reinforcing steel.

FC

30 N/mm2

Concrete Yield Stress.

CLEAR

25 mm 40 mm

For beam members. For column members

MINMAIN

10 mm


MAXMAIN

60 mm


MINSEC

8 mm


MAXSEC

12 mm


BRACING

0.0


RATIO

4.0


9-9


9-10

Section 9A

Table 9A.1 Indian Concrete Design IS456 Parameters Parameter Name RFACE

Default Value 4.0

Description A value of 4.0 means longitudinal reinforcement in column is arranged equally along 4 faces. A value of 2.0 invokes 2 faced distribution about major axis. A value of 3.0 invokes 2 faced distribution about minor axis.

WIDTH

ZD


DEPTH

YD


TRACK

0.0

BEAM DESIGN: For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output. COLUMN DESIGN: With TRACK = 0.0, reinforcement details are printed. With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output. With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output. With TRACK = 9.0, the details of section capacity calculations are printed.

REINF

0.0


Section 9A

Table 9A.1 Indian Concrete Design IS456 Parameters Parameter Name

Default Value

Description

ELZ

1.0


ELY

1.0


ULY

1.0

Ratio of unsupported length to actual length of column about minor axis.

ULZ

1.0

Ratio of unsupported length to actual length of column about major axis.

TORSION

0.0

A value of 0.0 means torsion to be considered in beam design. A value of 1.0 means torsion to be neglected in beam design.

SPSMAIN

25 mm

Minimum clear distance between main reinforcing bars in beam and column. For column centre to centre distance between main bars cannot exceed 300mm.

SFACE

0.0

Face of support location at start of beam. It is used to check against shear at the face of the support in beam design. The parameter can also be used to check against shear at any point from the start of the member.

EFACE

0.0

Face of support location at end of beam. The parameter can also be used to check against shear at any point from the end of the member. (Note: Both SFACE and EFACE are input as positive numbers).

9-11


9-12

Section 9A

Table 9A.1 Indian Concrete Design IS456 Parameters Parameter Name ENSH

Default Value 0.0

Description Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000. ENSH = 1.0 means ordinary shear check to be performed ( no enhancement of shear strength at sections close to support)

RENSH

0.0

For ENSH = a positive value(say x ), shear strength will be enhanced up to a distance x from the start of the member. This is used only when a span of a beam is subdivided into two or more parts. (Refer note ) For ENSH = a negative value(say –y), shear strength will be enhanced up to a distance y from the end of the member. This is used only when a span of a beam is subdivided into two or more parts.(Refer note) If default value (0.0) is used the program will calculate Length to Overall Depth ratio. If this ratio is greater than 2.5, shear strength will be enhanced at sections (<2d) close to support otherwise ordinary shear check will be performed. Distance of the start or end point of the member from its nearest support. This parameter is used only when a span of a beam is subdivided into two or more parts. (Refer note)

Bar combination has been introduced for detailing. Please refer section 8A.8 for details.

Notes: Value of ENSH parameter (other than 0.0 and 1.0) is used only when the span of a beam is subdivided into two or more parts. When this condition is aroused RENSH parameter is also to be used. Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

Section 9A

The span of the beam is subdivided four parts, each of length L metre. The shear strength will be enhanced up to X metre from both supports. The input should be the following: Steps: ENSH L MEMB 1 =>

Shear strength will be enhanced throughout the length of the member 1, positive sign indicates length measured from start of the member

ENSH (X-L) MEMB 2 => Shear strength will be enhanced up to a length (X-L) of the member 2, length measured from the start of the member ENSH –L MEMB 4 =>

Shear strength will be enhanced throughout the length of the member 4, negative sign indicates length measured from end of the member

ENSH –(X-L) MEMB 3 => Shear strength will be enhanced up to a length (X-L) of the member 3, length measured from the end of the member RENSH L MEMB 2 3 => Nearest support lies at a distance L from both the members 2 and 3. DESIGN BEAM 1 TO 4=> This will enhance the shear strength up to length X from both ends of the beam consisting of members 1 to 4 and gives spacing accordingly.

9-13


9-14

Section 9A

At section = y1 from start of member 1 av = y1 At section = y2 from the start of member 2 av = y2+L At section = y3 from the end of member 3 av = y3+L At section = y4 from end of member 4 av = y4 where c, enhanced = 2dc/av At section 0.0, av becomes zero. Thus enhanced shear strength will become infinity. However for any section shear stress cannot exceed c, max. Hence enhanced shear strength is limited to a maximum value of c, max.

9A.8 Bar Combination Initially the program selects only one bar to calculate the number of bars required and area of steel provided at each section along the length of the beam. Now, two bar diameters can be specified to calculate a combination of each bar to be provided at each section. The syntax for bar combination is given below. START BAR COMBINATION MD1 MEMB MD2 MEMB END BAR COMBINATION

Section 9A

MD2 bar diameter should be greater than MD1 bar diameter. The typical output for bar combination is shown below:

OUTPUT FOR BAR COMBINATION -------------------------------------------------------------|

M A I N

R E I N F O R C E M E N T

|

-------------------------------------------------------------SECTION | 0.0- 2166.7 | 2166.7- 6500.0 | 6500.0- 8666.7 | | mm | mm | mm | -------------------------------------------------------------TOP | 6-20í + 1-25í| 2-20í + 1-25í | 2-20í | | in 2 layer(s)| in 1 layer(s) | in 1 layer(s) | Ast Reqd| 2330.22 | 1029.90 | 582.55 | Prov| 2376.79 | 1119.64 | 628.57 | Ld (mm) | 940.2 | 940.2 | 940.2 | -------------------------------------------------------------BOTTOM | 4-20í | 2-20í | 2-20í | |in 1 layer(s) | in 1 layer(s) | in 1 layer(s) | Ast Reqd| 1165.11 | 582.55 | 582.55 | Prov| 1257.14 | 628.57 | 628.57 | Ld (mm) | 940.2 | 940.2 | 940.2 | -------------------------------------------------------------

The beam length is divided into three parts, two at its ends and one at span. Ld gives the development length to be provided at the two ends of each section.

9A.9 Wall Design in accordance with IS 456-2000 Design of walls in accordance with IS 456-2000 is available in STAAD.Pro. Design is performed for in-plane shear, in-plane and out-of-plane bending and out-of-plane shear. The wall has to be modeled using STAAD‟s Surface elements. The use of the Surface element enables the designer to treat the entire wall as one entity. It greatly simplifies the modeling of the wall and adds clarity to the analysis and design output. The results are presented in the context of the entire wall rather than individual finite elements thereby allowing users to quickly locate required information.

9-15


9-16

Section 9A

The program reports shear wall design results for each load case/combination for user specified number of sections given by SURFACE DIVISION (default value is 10) command. The shear wall is designed at these horizontal sections. The output includes the required horizontal and vertical distributed reinforcing, the concentrated (in-plane bending) edge reinforcing and the link required for out-of-plane shear. General format: START SHEARWALL DESIGN CODE INDIAN FYMAIN f1 FC f2 HMIN f3 HMAX f4 VMIN f5 VMAX f6 EMIN f7 EMAX f8 LMIN f9 LMAX f10 CLEAR f11 TWOLAYERED f12 KSLENDER f13 DESIGN SHEARWALL LIST shearwall-list END

Section 9A

The following table explains the parameters used in the shear wall design. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. SHEAR WALL DESIGN PARAMETERS Parameter Name

Default Value

Description

FYMAIN

415 Mpa

Yield strength of steel, in current units.

FC

30 Mpa

Compressive strength of concrete, in current units.

HMIN

8

Minimum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

HMAX

36

VMIN

8

VMAX

36

EMIN

8

EMAX

36

LMIN

6

Maximum size of horizontal reinforcing bars (range 6 mm – 36 mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Minimum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Maximum size of vertical reinforcing bars (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Minimum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Maximum size of vertical reinforcing bars located in edge zones (range 6mm – 36mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Minimum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar.

9-17


9-18

Section 9A

SHEAR WALL DESIGN PARAMETERS Parameter Name LMAX

Default Value 16

CLEAR

25 mm

TWOLAYERED

KSLENDER

0

1.0

Description Maximum size of links (range 6mm – 16mm). If input is 6 (integer number) the program will assume 6 mm diameter bar. Clear concrete cover, in current units. Reinforcement placement mode: 0 - single layer, each direction 1 - two layers, each direction Slenderness factor for finding effective height.

Table 6 The following example illustrates the input for the definition of shear wall and design of the wall. Example

. . SET DIVISION 12 SURFACE INCIDENCES 2 5 37 34 SUR 1 19 16 65 68 SUR 2 11 15 186 165 SUR 3 10 6 138 159 SUR 4 . . . SURFACE PROPERTY 1 TO 4 THI 18 SUPPORTS 1 7 14 20 PINNED 2 TO 5 GEN PIN 6 TO 10 GEN PIN

Section 9A

11 TO 15 GEN PIN 19 TO 16 GEN PIN . . . SURFACE CONSTANTS E 2.17185e+007 POISSON 0.17 DENSITY 23.5616 ALPHA 1e-005 . . START SHEARWALL DES CODE INDIAN UNIT NEW MMS FC 25 FYMAIN 415 TWO 1 VMIN 12 HMIN 12 EMIN 12 DESIGN SHEA LIST 1 TO 4 END Notes 1.

2. 3.

Command SET DIVISION 12 indicates that the surface boundary node-to-node segments will be subdivided into 12 fragments prior to finite element mesh generation. Four surfaces are defined by the SURFACE INCIDENCES command. The SUPPORTS command includes the new support generation routine. For instance, the line 2 TO 5 GEN PIN assigns pinned supports to all nodes between nodes 2 and 5. As the node-to-node distances were previously subdivided by the SET DIVISION 12 command, there will be an

9-19


9-20

Section 9A

4.

5.

additional 11 nodes between nodes 2 and 5. As a result, all 13 nodes will be assigned pinned supports. Please note that the additional 11 nodes are not individually accessible to the user. They are created by the program to enable the finite element mesh generation an d to allow application of boundary constraints. Surface thickness and material constants are specified by the SURFACE PROPERTY and SURFACE CONSTANTS, respectively. The shear wall design commands are listed between lines START SHEARWALL DES and END. The CODE command selects the design code that will be the basis for the design. For Indian code the parameter is INDIAN. The DESIGN SHEARWALL LIST command is followed by a list of previously defined Surface elements intended as shear walls and/or shear wall components.

Technical Overview The program implements provisions of section 32 of IS 456 -2000 and relevant provisions as referenced therein, for all active load cases. The following steps are performed for each of the horizontal sections of the wall. Checking of slenderness limit The slenderness checking is done as per clause no. 32.2.3. The default effective height is the height of the wall. User can change the effective height. The limit for slenderness is taken as 30. Design for in-plane bending and vertical load (denoted by Mz & Fy in the shear wall force output) Walls when subjected to combined in -plane horizontal and vertical forces produce in-plane bending in conjunction with vertical load. According to clause no. 32.3.1, in -plane bending may be neglected in case a horizontal cross section of the wall is always under compression due combined effect of horizontal and vertical loads. Otherwise, the section is checked for combined vertical load and

Section 9A

in-plane moment as column with axial load and uni -axial bending. For this purpose, the depth is taken as 0.8 x horizontal length of wall and breadth is the thickness of the wall. The reinforcement is concentrated at both ends (edges) of the wall. The edge reinforcement is assumed to be distributed over a len gth of 0.2 times horizontal length on each side. Minimum reinforcements are according to clause no. 32.5.(a). Maximum 4% reinforcement is allowed. Design for in-plane shear (denoted by Fxy in the shear wall force output) By default, the program does not design only at the critical section but at all the horizontal sections. By suitable use of the surface division command, design at critical section as per clause no. 32.4.1 can be performed. The design for in-plane shear is done as per clause no. 32.4. The nominal shear stress is calculated as per clause no. 32.4.2 and it is checked with the maximum allowable shear stress as per clause no. 32.4.2.1. The design shear strength of concrete is calculated as per clause no. 32.4.3. Design of shear reinforcement is done as per clause no. 32.4.4. Minimum reinforcements are as per clause no. 32.5. Design for vertical load and out-of-plane vertical bending (denoted by Fy and My respectively in the shear wall force output) Apart from the in-plane bending and horizontal shear force, the wall is also subjected to out-of-plane bending in the vertical and horizontal directions. The part of the wall which is not having edge reinforcements (i.e. a zone of depth 0.6 x Length of the wall), is designed again as column under axial load (i.e. vertical load) and out-of-plane vertical bending. The minimum reinforcements and maximum allowable spacings of reinforcements are as per clause no. 32.5

9-21


9-22

Section 9A

Design for out-of-plane horizontal bending (denoted by Mx in the shear wall force output) The horizontal reinforcement which is already provided for in plane shear is checked against out-of-plane horizontal bending. The wall is assumed as a slab for this purpose. Design for out-of-plane shears (denoted by Qx and Qy in the shear wall force output) The out-of-plane shear arises from out-of-plane loading. The nominal shear stresses are calculated as per clause no. 40.1. Maximum allowable shear stresses are as per table 20. For shear force in the vertical direction, shear strength of concrete section is calculated as per section 4.1 of SP 16 : 1980 considering vertical reinforcement as tension reinforcement. Similarly, for shear force in the horizontal direction, shear strength of concrete section is calculated considering horizontal reinforcement as tension reinforcement. Shear reinforcements in the form of links are computed as per the provisions of clause no. 40.4. Shear Wall Design With Opening The Surface element has been enhanced to allow design of shear walls with rectangular openings. The automatic meshing algorithm has been improved to allow variable divisions along wall and opening(s) edges. Design and output are available for user selected locations. Description Shear walls modeled in STAAD.Pro may include an unlimited number of openings. Due to the presence of openings, the wall may comprise up with different wall panels.

Section 9A

1.

9-23

Shear wall set-up Definition of a shear wall starts with a specification of the surface element perimeter nodes, meshing divisions along node-to-node segments, opening(s) corner coordinates, and meshing divisions of four edges of the opening(s).

SURFACE INCIDENCE n1, ..., ni SURFACE s DIVISION sd1, ..., sdj RECOPENING x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 DIVISION od1, ..., odk

where, n1, ..., ni s sd1, ..., sdj

- node numbers on the perimeter of the shear wall, - surface ordinal number, - number of divisions for each of the node-to-node distance on the surface perimeter, x1 y1 z1 (...) - coordinates of the corners of the opening, od1, ..., odk - divisions along edges of the opening. Note: If the sd1, ..., sdj or the od1, ..., odk list does not include all nodeto-node segments, or if any of the numbers listed equals zero, then the corresponding division number is set to the default value (=10, or as previously input by the SET DIVISION command). Default locations for stress/force output, design, and design output are set as follows:

SURFACE DIVISION X xd SURFACE DIVISION Y yd


9-24

Section 9A

where, xd yd

- number of divisions along X axis, - number of divisions along Y axis.

Note: xd and yd represent default numbers of divisions for each edge of the surface where output is requested. The output is provided for sections located between division segments. For example, if the number of divisions = 2, then the output will be produced for only one section (at the center of the edge). 2.

Stress/force output printing Values of internal forces may be printed out for any user -defined section of the wall. The general format of the command is as follows: PRINT SURFACE FORCE (ALONG ) (AT a) (BETWEEN d1, d2) LIST s1, ...,si where,  a d1, d2

s1, ...,si

- local axis of the surface element (X or Y), - distance along the   a xis from start of the member to the full cross-section of the wall, - coordinates in the direction orthogonal to  , delineating a fragment of the full cross-section for which the output is desired. ** - list of surfaces for output generation

** The range currently is taken in terms of local axis. If the local axis is directed away from the surface, the negative range is to be entered.

Section 9A

9-25

Note: If command ALONG is omitted, direction Y (default) is assumed. If command AT is omitted, output is provided for all sections along the specified (or default) edge. Number of sections will be determined from the SURFACE DIVISION X or SURFACE DIVISION Y input values. If the BETWEEN command is omitted, the output is generated based on full cross-section width. 3.

Definition of wall panels Input syntax for panel definition is as follows:

START PANEL DEFINITION SURFACE i PANEL j ptype x1 y1 z1 x2 y2 z2 x3 y3 z3 x4 y4 z4 END PANEL DEFINITION

where, i j ptype x1 y1 z1 (...) 4.

- ordinal surface number, - ordinal panel number, - panel type, one of: WALL, COLUMN, BEAM - coordinates of the corners of the panel,

Shear wall design The program implements different provisions of design of walls as per code BS 8110. General syntax of the design command is as follows:

START SHEARWALL DESIGN (...) DESIGN SHEARWALL (AT c) LIST s END SHEARWALL DESIGN


9-26

Section 9A

Note: If the command AT is omitted, the design proceeds for all cross sections of the wall or panels, as applicable, defined by the SURFACE DIVISION X or SURFACE DIVISION Y input values. a.

No panel definition.

Design is performed for the specified horizontal full cross -section, located at a distance c from the origin of the local coordinates system. If opening is found then reinforcement is provided along sides of openings. The area of horizontal and vertical bars provided along edges of openings is equal to that of the respective interrupted bars. b. Panels have been defined. Only wall panel design is supported in Indian code.

9-27


Section

9A1

9A1.1 Design Operations Earthquake motion often induces force large enough to cause inelastic deformations in the structure. If the structure is brittle, sudden failure could occur. But if the structure is made to behave ductile, it will be able to sustain the earthquake effects better with some deflection larger than the yield deflection by absorption of energy. Therefore ductility is also required as an essential element for safety from sudden collapse during severe shocks. STAAD has the capabilities of performing concrete design as per IS 13920. While designing it satisfies all provisions of IS 456 – 2000 and IS 13920 for beams and columns.

9A1.2 Section Types for Concrete Design The following types of cross sections for concrete members can be designed. For Beams

Prismatic (Rectangular & Square) & T -shape

For Columns



9-28

Section 9A1

9A1.3 Design Parameters The program contains a number of parameters that are needed to perform design as per IS 13920. It accepts all parameters that are needed to perform design as per IS:456. Over and above it has some other parameters that are required only when designed is performed as per IS:13920. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 8A1.1 of this manual contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as Millimeter and Newton before performing the concrete design.

9A1.4 Beam Design Beams are designed for flexure, shear and torsion. If required the effect of the axial force may be taken into consideration. For all these forces, all active beam loadings are prescanned to identify the critical load cases at different sections of the beams. The total number of sections considered is 13. All of these sections are scanned to determine the design force envelopes. For design to be performed as per IS:13920 the width of the member shall not be less than 200mm(Clause 6.1.3). Also the member shall preferably have a width -to depth ratio of more than 0.3 (Clause 6.1.2). The factored axial stress on the member should not exceed 0.1fck (Clause 6.1.1) for all active load cases. If it exceeds allowable axial stress no design will be performed.

Section 9A1

Design for Flexure Design procedure is same as that for IS 456. However while designing following criteria are satisfied as per IS-13920: 1.

The minimum grade of concrete shall preferably be M20. (Clause 5.2)

2.

Steel reinforcements of grade Fe415 or less only shall be used. (Clause 5.3)

3.

The minimum tension steel ratio on any face, at any section, is given by  min = 0.24fck/fy (Clause 6.2.1b) The maximum steel ratio on any face, at any section, is given by

 ma x = 0.025 (Clause 6.2.2) 4.

The positive steel ratio at a joint face must be at least equal to half the negative steel at that face. (Clause 6.2.3)

5.

The steel provided at each of the top and bottom face, at any section, shall at least be equal to one-fourth of the maximum negative moment steel provided at the face of either joint. (Clause 6.2.4) Design for Shear The shear force to be resisted by vertical hoops is guided by the Clause 6.3.3 of IS 13920:1993 revision. Elastic sagging and hogging moments of resistance of the beam section at ends are considered while calculating shear force. Plastic sagging and hogging moments of resistance can also be considered for shear design if PLASTIC parameter is mentioned in the input file. (Refer Table 8A1.1) Shear reinforcement is calculated to resist both shear forces and torsional moments. Procedure is same as that of IS 456.

9-29


9-30

Section 9A1

The following criteria are satisfied while performing design for shear as per Cl. 6.3.5 of IS-13920: The spacing of vertical hoops over a length of 2d at either end of the beam shall not exceed a) d/4 b) 8 times the diameter of the longitudinal bars In no case this spacing is less than 100 mm. The spacing calculated from above, if less than that calculated from IS 456 consideration is provided. Beam Design Output The default design output of the beam contains flexural and shear reinforcement provided at 5 equally spaced sections along the length of the beam. User has option to get a more detail output. All beam design outputs are given in IS units. An example of rectangular beam design output with the default output option (TRACK 1.0) is presented below:

Section 9A1 ============================================================================ B E A M N O. 11 D E S I G N R E S U L T S M20 LENGTH:

Fe415 (Main) 3500.0 mm

SIZE:

Fe415 (Sec.)

250.0 mm X

350.0 mm

COVER: 30.0 mm

DESIGN LOAD SUMMARY (KN MET) ---------------------------------------------------------------------------SECTION |FLEXTURE (Maxm. Sagging/Hogging moments)| SHEAR (in mm) | P MZ MX Load Case | VY MX Load Case ---------------------------------------------------------------------------0.0 | 0.00 0.00 0.00 4 | 17.67 0.00 4 | 0.00 -2.74 0.00 5 | 291.7 | 0.00 1.15 0.00 5 | 16.26 0.00 4 | 0.00 0.00 0.00 4 | 583.3 | 0.00 4.61 0.00 5 | 13.97 0.00 4 | 0.00 0.00 0.00 4 | 875.0 | 0.00 7.44 0.00 5 | 10.78 0.00 4 | 0.00 0.00 0.00 4 | 1166.7 | 0.00 9.41 0.00 5 | 6.69 0.00 4 | 0.00 0.00 0.00 4 | 1458.3 | 0.00 10.33 0.00 5 | 1.10 0.00 5 | 0.00 0.00 0.00 4 | 1750.0 | 0.00 9.98 0.00 5 | -3.60 0.00 5 | 0.00 0.00 0.00 4 | 2041.7 | 0.00 8.23 0.00 5 | -10.02 0.00 4 | 0.00 0.00 0.00 4 | 2333.3 | 0.00 5.21 0.00 5 | -15.00 0.00 4 | 0.00 0.00 0.00 4 | 2625.0 | 0.00 1.14 0.00 5 | -19.08 0.00 4 | 0.00 0.00 0.00 4 | 2916.7 | 0.00 0.00 0.00 4 | -22.27 0.00 4 | 0.00 -3.79 0.00 5 | 3208.3 | 0.00 0.00 0.00 4 | -24.57 0.00 4 | 0.00 -9.35 0.00 5 | 3500.0 | 0.00 0.00 0.00 4 | -25.97 0.00 4 | 0.00 -15.34 0.00 5 | *** DESIGN SHEAR FORCE AT SECTION

0.0 IS

68.60 KN.

*** DESIGN SHEAR FORCE AT SECTION

3500.0 IS

13920 75.24 KN.

- CLAUSE 6.3.3 OF IS- CLAUSE 6.3.3 OF IS13920 ----------------------------------------------------------------------------

SUMMARY OF REINF. AREA (Sq.mm) ---------------------------------------------------------------------------SECTION 0.0 mm 875.0 mm 1750.0 mm 2625.0 mm 3500.0 mm ---------------------------------------------------------------------------TOP 226.30 0.00 0.00 0.00 226.30 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) BOTTOM 0.00 203.02 203.02 203.02 0.00 REINF. (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) (Sq. mm) ---------------------------------------------------------------------------SUMMARY OF PROVIDED REINF. AREA ---------------------------------------------------------------------------SECTION 0.0 mm 875.0 mm 1750.0 mm 2625.0 mm 3500.0 mm ---------------------------------------------------------------------------TOP 3-10í 2-10í 2-10í 2-10í 3-10í REINF. 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) 1 layer(s) BOTTOM REINF.

2-12í 1 layer(s)

2-12í 1 layer(s)

2-12í 1 layer(s)

2-12í 1 layer(s)

2-12í 1 layer(s)

SHEAR 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8í 2 legged 8í REINF. @ 100 mm c/c @ 150 mm c/c @ 150 mm c/c @ 150 mm c/c @ 100 mm c/c ---------------------------------------------------------------------------============================================================================

9-31


9-32

Section 9A1

9A1.5 Column Design Columns are designed for axial forces and biaxial moments per IS 456:2000. Columns are also designed for shear forces as per Clause 7.3.4. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by IS:456 have been taken care of in the column design of STAAD. However following clauses have been satisfied to incorporate provisions of IS 13920: 1. The minimum grade of concrete shall preferably be M20. (Clause 5.2) 2. Steel reinforcements of grade Fe415 or less only shall be used. (Clause 5.3) 3. The minimum dimension of column member shall not be less than 200 mm. For columns having unsupported length exceeding 4m, the shortest dimension of column shall not be less than 300 mm. (Clause 7.1.2) 4. The ratio of the shortest cross-sectional dimension to the perpendicular dimension shall preferably be not less than 0.4. (Clause 7.1.3) 5. The spacing of hoops shall not exceed half the least lateral dimension of the column, except where special confining reinforcement is provided. (Clause 7.3.3) 6. Special confining reinforcement shall be provided over a length l o from each joint face, towards mid span, and on either side of any section, where flexural yielding may occur. The length l o shall not be less than a) larger lateral dimension of the member at the section where yielding occurs, b) 1/6 of clear span of the member, and c) 450 mm. (Clause 7.4.1) 7. The spacing of hoops used as special confining reinforcement shall not exceed ¼ of minimum member dimension but need not be less than 75 mm nor more than 100 mm. (Clause 7.4.6)

Section 9A1

8. The area of cross-section of hoops provided are checked against the provisions for minimum area of cross-section of the bar forming rectangular, circular or spiral hoops, to be used as special confining reinforcement. (Clause 7.4.7 and 7.4.8) Column Design Output Default column design output (TRACK 0.0) contains the reinforcement provided by STAAD and the capacity of the section. With the option TRACK 1.0, the output contains intermediate results such as the design forces, effective length coefficients, additional moments etc. A special output TRACK 9.0 is introduced to obtain the details of section capacity calculations. All design output is given in SI units. An example of a column desig n output (with option TRACK 1.0) is given below. ============================================================================ C O L U M N

N O.

M20 LENGTH:

3

D E S I G N

R E S U L T S

Fe415 (Main) 3000.0 mm

CROSS SECTION:


Fe415 (Sec.)

350.0 mm X

5 END JOINT:

2


:


: :


: : : :

-


:

4.53


400.0 mm

COVER: 40.0 mm

SHORT COLUMN

226.7 About Z 0.64 4.53

About Y 146.28 4.53 146.28

5

DESIGN SHEAR FORCES

Along Z 43.31

:

Along Y 76.08

REQD. STEEL AREA : 3313.56 Sq.mm. MAIN REINFORCEMENT : Provide 12 - 20 dia. (2.69%, 3769.91 Sq.mm.) (Equally distributed) CONFINING REINFORCEMENT : Provide 10 mm dia. rectangular ties @ 85 mm c/c over a length 500.0 mm from each joint face towards midspan as per Cl. 7.4.6 of IS-13920. TIE REINFORCEMENT : Provide 10 mm dia. rectangular ties @ 175 mm c/c SECTION CAPACITY (KNS-MET) -------------------------Puz : 2261.52 Muz1 :

178.71

Muy1 :

150.75

INTERACTION RATIO: 1.00 (as per Cl. 39.6, IS456:2000) ============================================================================ ********************END OF COLUMN DESIGN RESULTS********************

9-33


9-34

Section 9A1

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 9A1.1 Indian Concrete Design IS13920 Parameters Parameter Name FYMAIN FYSEC FC CLEAR

Default Value 415 N/mm2 415 N/mm 30 N/mm

2

2

Description Yield Stress for main reinforcing steel. Yield Stress for secondary reinforcing steel. Concrete Yield Stress.

25 mm

For beam members.

40 mm

For column members

MINMAIN

10 mm


MAXMAIN

60 mm


MINSEC

8 mm


MAXSEC

12 mm


BRACING

0.0


RATIO

4.0


RFACE

4.0

A value of 4.0 means longitudinal reinforcement in column is arranged equally along 4 faces. A value of 2.0 invokes 2 faced distribution about major axis.

Section 9A1

9-35

Table 9A1.1 Indian Concrete Design IS13920 Parameters Parameter Name

Default Value

Description A value of 3.0 invokes 2 faced distribution about minor axis.

WIDTH

ZD


DEPTH

YD


ELZ

1.0


ELY

1.0


REINF

0.0


TORSION

0.0

A value of 0.0 means torsion to be considered in beam design. A value of 1.0 means torsion to be neglected in beam design.

TRACK

0.0

BEAM DESIGN: For TRACK = 0.0, output consists of reinforcement details at START, MIDDLE and END. For TRACK = 1.0, critical moments are printed in addition to TRACK 0.0 output. For TRACK = 2.0, required steel for intermediate sections defined by NSECTION are printed in addition to TRACK 1.0 output. COLUMN DESIGN: With TRACK = 0.0, reinforcement details are printed. With TRACK = 1.0, column interaction analysis results are printed in addition to TRACK 0.0 output.


9-36

Section 9A1


Default Value

Description With TRACK = 2.0, a schematic interaction diagram and intermediate interaction values are printed in addition to TRACK 1.0 output.

SPSMAIN

25 mm

Minimum clear distance between main reinforcing bars in beam and column. For column centre to centre distance between main bars cannot exceed 300mm.

SFACE

0.0

Face of support location at start of beam. It is used to check against shear at the face of the support in beam design. The parameter can also be used to check against shear at any point from the start of the member.*

EFACE

0.0

Face of support location at end of beam. The parameter can also be used to check against shear at any point from the end of the member. (Note: Both SFACE and EFACE are input as positive numbers).*

ENSH

0.0

Perform shear check against enhanced shear strength as per Cl. 40.5 of IS456:2000. ENSH = 1.0 means ordinary shear check to be performed ( no enhancement of shear strength at sections close to support) For ENSH = a positive value(say x ), shear strength will be enhanced up to a distance x from the start of the member. This is used only when a span of a beam is subdivided into two or more parts. (Refer note after Table 8A.1 ) For ENSH = a negative value(say –y), shear strength will be enhanced up to a distance y from the end of the member. This is used only when a span of a beam is subdivided into two or more parts.(Refer note after Table 8A.1) If default value (0.0) is used the program will calculate Length to Overall Depth ratio. If this ratio is greater than 2.5, shear strength will be enhanced at sections (<2d) close to support otherwise ordinary shear check will

Section 9A1

9-37


Default Value

Description be performed.

RENSH

0.0

Distance of the start or end point of the member from its nearest support. This parameter is used only when a span of a beam is subdivided into two or more parts. (Refer note after Table 8A.1)

EUDL

None

Equivalent u.d.l on span of the beam. This load value must be the unfactored load on span. During design the load value is multiplied by a factor 1.2. If no u.d.l is defined factored shear force due to gravity load on span will be taken as zero. No elastic or plastic moment will be calculated. Shear design will be performed based on analysis result.(Refer note)

GLD

None

Gravity load number to be considered for calculating equivalent u.d.l on span of the beam, in case no EUDL is mentioned in the input. This loadcase can be any static loadcase containing MEMBER LOAD on the beam which includes UNI, CON, LIN and TRAP member loading. CMOM member loading is considered only when it is specified in local direction. FLOOR LOAD is also considered. The load can be primary or combination load. For combination load only load numbers included in load combination is considered. The load factors are ignored. Internally the unfactored load is multiplied by a factor 1.2 during design. If both EUDL and GLD parameters are mentioned in the input mentioned EUDL will be considered in design Note : No dynamic (Response spectrum, 1893, Time History) and moving load cases are considered. CMOM member loading in global direction is


9-38

Section 9A1


Default Value

Description not considered. UMOM member loading is not considered.

PLASTIC

0.0

Default value calculates elastic hogging and sagging moments of resistance of beam at its ends. A value of 1.0 means plastic hogging and sagging moments of resistance of beam to be calculated at its ends.

IPLM

0.0

Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends. A value of 1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at start node of beam. This implies no support exists at start node. A value of -1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at start node of beam. . This implies support exists at start node. A value of 2.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be ignored at end node of beam. This implies no support exists at end node. A value of -2.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at end node of beam. . This implies support exists at end node. **

IMB

0.0

Default value calculates elastic/plastic hogging and sagging moments of resistance of beam at its ends. A value of 1.0 means calculation of

Section 9A1

9-39


Default Value

Description elastic/plastic hogging and sagging moments of resistance of beam to be ignored at both ends of beam. This implies no support exist at either end of the member. A value of -1.0 means calculation of elastic/plastic hogging and sagging moments of resistance of beam to be considered at both ends of beam. This implies support exist at both ends of the member.**

COMBINE

0.0

Default value means there will be no member combination. A value of 1.0 means there will be no printout of sectional force and critical load for combined member in the output. A value of 2.0 means there will be printout of sectional force for combined member in the output. A value of 3.0 means there will be printout of both sectional force and critical load for combined member in the output. ***

HLINK

Spacing of longitudinal bars measured to the outer face

Longer dimension of the rectangular confining hoop measured to its outer face. It shall not exceed 300 mm as per Cl. 7.4.8. If hlink value as provided in the input file does not satisfy the clause the value will be internally assumed as the default one. This parameter is valid for rectangular column.

Bar combination has been introduced for detailing. Please refer section 8A1.6 for details.

* EFACE and SFACE command is not valid for member combination. ** IPLM and IMB commands are not valid for member combination. These commands are ignored for members forming physical member.


9-40

Section 9A1

*** The purpose of COMBINE command is the following: 1.

If a beam spanning between two supports is subdivided into many sub-beams this parameter will combine them into one member. It can also be used to combine members to form one continuous beam spanning over more than two supports.

2.

When two or more members are combined during design plastic or elastic moments will be calculated at the column supports. At all the intermediate nodes (if any) this calculation will be ignored. Please note that the program only recognizes column at right angle to the beam. Inclined column support is ignored.

3.

It will calculate sectional forces at 13 sections along the length of the combined member.

4.

It will calculate critical loads (similar to that of Design Load Summary) for all active load cases during design. Beams will be combined only when DESIGN BEAM command is issued. The following lines should be satisfied during combination of members:

1.

2.

3. 4. 5. 6. 7.

Members to be combined should have same sectional properties if any single span between two column support s of a continuous beam is subdivided into several members. Members to be combined should have same constants (E, Poi ratio, alpha, density and beta angle) Members to be combined should lie in one straight line. Members to be combined should be continuous. Vertical members (i.e. columns) cannot be combined. Same member cannot be used more than once to form two different combined members. The maximum number of members that can be combined into one member is 299.

Section 9A1

Note: Sectional forces and critical load for combined member output will only be available when all the members combined are successfully designed in both flexure and shear. ENSH and RENSH parameters will have to be provided (as and when necessary) even if physical member has been formed.

The following lines show a standard example for design to be performed in IS 13920. STAAD SPACE UNIT METER MTON JOINT COORDINATES ………………………………….. MEMBER INCIDENCES ………………………………….. MEMBER PROPERTY INDIAN ………………………………….. CONSTANTS ……………………. SUPPORTS ……………………. DEFINE 1893 LOAD ZONE 0.05 I 1 K 1 B 1 SELFWEIGHT JOINT WEIGHT ………………………. LOAD 1 SEISMIC LOAD IN X DIR 1893 LOAD X 1 LOAD 2 SEISMIC LOAD IN Z DIR 1893 LOAD Z 1 LOAD 3 DL MEMBER LOAD …… UNI GY -5 LOAD 4 LL

9-41


9-42

Section 9A1

MEMBER LOAD ……. UNI GY -3 LOAD COMB 5 1.5(DL+LL) 3 1.5 4 1.5 LOAD COMB 6 1.2(DL+LL+SLX) 1 1.2 3 1.2 4 1.2 LOAD COMB 7 1.2(DL+LL-SLX) 1 1.2 3 1.2 4 -1.2 LOAD COMB 8 1.2(DL+LL+SLZ) 2 1.2 3 1.2 4 1.2 LOAD COMB 9 1.2(DL+LL-SLZ) 2 1.2 3 1.2 4 -1.2 PDELTA ANALYSIS LOAD LIST 5 TO 9 START CONCRETE DESIGN CODE IS13920 UNIT MMS NEWTON FYMAIN 415 ALL FC 20 ALL MINMAIN 12 ALL MAXMAIN 25 ALL TRACK 2.0 ALL *** Unfactored gravity load on members 110 to 112 is 8 t/m (DL+LL) i.e. 78.46 New/mm EUDL 78.46 MEMB 110 TO 112 ** Members to be combined into one physical member COMBINE 3.0 MEMB 110 TO 112

*** Plastic moment considered PLASTIC 1.0 MEMB 110 TO 112 DESIGN BEAM 110 TO 112 DESIGN COLUMN ……… END CONCRETE DESIGN FINISH

Section 9A1

9A1.6 Bar Combination Initially the program selects only one bar to calculate the number of bars required and area of steel provided at each section along the length of the beam. Now two bar diameters can be specified to calculate a combination of each bar to be provided at each section. The syntax for bar combination is given below. START BAR COMBINATION MD1 MEMB MD2 MEMB END BAR COMBINATION MD2 bar diameter should be greater than MD1 bar diameter. The typical output for bar combination is shown below: OUTPUT FOR BAR COMBINATION ---------------------------------------------------------------------------|

M A I N

R E I N F O R C E M E N T

|

---------------------------------------------------------------------------SECTION | 0.0- 2166.7 | 2166.7- 6500.0 | 6500.0- 8666.7 | | mm | mm | mm | ---------------------------------------------------------------------------TOP | 6-20í + 1-25í | 2-20í + 1-25í | 2-20í | | in 2 layer(s) | in 1 layer(s) | in 1 layer(s) | Ast Reqd| 2330.22 | 1029.90 | 582.55 | Prov| 2376.79 | 1119.64 | 628.57 | Ld (mm) | 940.2 | 940.2 | 940.2 | ---------------------------------------------------------------------------BOTTOM | 4-20í | 2-20í | 2-20í | | in 1 layer(s) | in 1 layer(s) | in 1 layer(s) | Ast Reqd| 1165.11 | 582.55 | 582.55 | Prov| 1257.14 | 628.57 | 628.57 | Ld (mm) | 940.2 | 940.2 | 940.2 | ----------------------------------------------------------------------------

The beam length is divided into three parts, two at its ends and one at span. Ld gives the development length to be provided at the two ends of each section.

9-43


9-44

Section 9A1

Sample example showing calculation of design shear force as per Clause 6.3.3

For Beam No. 1 and 2 Section Characteristic Strength of Steel fy Characteristic Strength of Concrete fck Clear Cover Bar Diameter Effective Depth d Eudl w Length L

Width b

250 mm

Depth D

500 mm 415 N/sq. mm 20 N/sq. mm 25 mm 12 mm 469 mm 6.5 N/sq. mm 4000 mm

Ast_Top_A

339.29 sq. mm

Ast_Bot_A

226.19 sq. mm

Ast_Top_B

226.19 sq. mm

Ast_Bot_B

339.29 sq. mm

Section 9A1

Steps Calculation of Simple Shear Simple shear from gravity load on span =

Va = Vb = 1.2 * w * L / 2

= 15600N

Calculation of Moment Of Resistances Based On Area Of Steel Provided Sagging Moment Of Resistance of End A Mu, as =

0.87 * fy * Ast_Bot_A * d *

Hogging Moment Of Resistance of End A Micah =

0.87 * fy * Ast_Top_A * d *

Sagging Moment Of Resistance of End A Mu, bs =

0.87 * fy * Ast_Bot_B * d *

Hogging Moment Of Resistance of End A Mob =

0.87 * fy * Ast_Top_B * d * ( 1 Ast_Top_B* fy / b * d * fck)

= 36768130.05 N

( 1 - Ast_Bot_A * fy / b * d * fck)

= 54003057.45 N

( 1 - Ast_Top_A * fy / b * d * fck)

= 54003057.45 N

( 1 - Ast_Bot_B * fy / b * d * fck)

= 36768130.05 N

Calculation of Shear Force Due To Formation Of Plastic Hinge At Both Ends Of The Beam Plus The Factored Gravity Load On Span

FIG1: SWAY TO RIGHT

Vur,a =

Va - 1.4 [ ( Mu,as + Mu,bh ) / L ] =

-10137.69104 N

Vur,b =

Va + 1.4 [ ( Mu,as + Mu,bh ) / L ] =

41337.69104 N

9-45


9-46

Section 9A1

FIG2: SWAY TO LEFT Vul,a =

Va + 1.4 [ ( Mu,ah + Mu,bs ) / L ] =

Vul,b =

Va - 1.4 [ ( Mu,ah + Mu,bs ) / L ] =

53402.14022 N - 22202.14022 N

Design Shear Force Shear Force From Analysis At End A , Va,anl = Design Shear Force At End A, Vu,a = Max ( Va,anl, Vur,a, Vul,a) = Shear Force From Analysis At End B , Vb,anl = Design Shear Force At End B, Vu,b = Max ( Vb,anl, Vur,b, Vul,b) =

11.56 N 53402.14022 N -6.44 N 41337.69104 N

For Beam No. 3 Section

Width b Depth D

Characteristic Strength of Steel fy Characteristic Strength of Concrete fck

300 mm 450 mm 415 N/sq. mm 20 N/sq. mm

Clear Cover

25 mm

Bar Diameter

12 mm

Effective Depth d Eudl w Length L

419 mm 6.5 N/sq. mm 3000 mm

Ast_Top_A

226.19 sq. mm

Ast_Bot_A

339.29 sq. mm

Ast_Top_B

452.39 sq. mm

Ast_Bot_B

226.19 sq. mm

Section 9A1 Calculation of Simple Shear Simple shear from gravity load on span =

Va = Vb = 1.2 * w * L / 2

= 11700N

Calculation of Moment Of Resistances Based On Area Of Steel Provided Sagging Moment Of Resistance of End A Mu,as =

0.87 * fy * Ast_Bot_A * d *

Hogging Moment Of Resistance of End A Mu,ah =

0.87 * fy * Ast_Top_A * d *

Sagging Moment Of Resistance of End A Mu,bs =

0.87 * fy * Ast_Bot_B * d *

Hogging Moment Of Resistance of End A Mu,bh =

0.87 * fy * Ast_Top_B * d * ( 1 Ast_Top_B* fy / b * d * fck)

= 48452983 N

( 1 - Ast_Bot_A * fy / b * d * fck)

( 1 - Ast_Top_A * fy / b * d * fck)

( 1 - Ast_Bot_B * fy / b * d * fck)

= 32940364.5 N

= 32940364.5 N

= 63326721.3 N

Calculation of Shear Force Due To Formation Of Plastic Hinge At Both Ends Of The Beam Plus The Factored Gravity Load On Span

FIG1: SWAY TO RIGHT Vur,a =

Va - 1.4 [ ( Mu,as + Mu,bh ) / L ] =

-40463.862 N

Vur,b =

Va + 1.4 [ ( Mu,as + Mu,bh ) / L ] =

63863.862 N

9-47


9-48

Section 9A1

Vul,a =

Va + 1.4 [ ( Mu,ah + Mu,bs ) / L ] =

42444.3402 N

Vul,b =

Va - 1.4 [ ( Mu,ah + Mu,bs ) / L ] =

-15144.34 N

Design Shear Force Shear Force From Analysis At End A , Va,anl = Design Shear Force At End A, Vu,a = Max ( Va,anl, Vur,a, Vul,a) = Shear Force From Analysis At End B , Vb,anl = Design Shear Force At End B, Vu,b = Max ( Vb,anl, Vur,b, Vul,b) =

-10.31 N 42444.3402 N

-23.81 N 63863.862 N

9-49

Steel Design Per IS800 Section

9B

9B.1 Design Operations STAAD contains a broad set of facilities for designing structural members as individual components of an analyzed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are:  Specify the members and the load cases to be considered in the design.  Specify whether to perform code checking or member selection.  Specify design parameter values, if different from the default values.  Specify whether to perform member selection by optimization. These operations may be repeated by the user any number of times depending upon the design requirements. The entire ISI steel section table is supported. Section 8B.13 describes the specification of steel sections.

Steel Design Per IS800

9-50

Section 9B

9B.2 General Comments This section presents some general statements regarding the implementation of Indian Standard code of practice (IS:800 -1984) for structural steel design in STAAD. The design philosophy and procedural logistics for member selection and code checking are based upon the principles of allowable stress design. Two major failure modes are recognized: failure by overstressing, and failure by stability considerations. The flowing sections describe the salient features of the allowable stresses being calculated an d the stability criteria being used. Members are proportioned to resist the design loads without exceeding the allowable stresses and the most economic section is selected on the basis of least weight criteria. The code checking part of the program checks stability and strength requirements and reports the critical loading condition and the governing code criteria. It is generally assumed that the user will take care of the detailing requirements like provision of stiffeners and check the local effects such as flange buckling and web crippling.

9B.3 Allowable Stresses The member design and code checking in STAAD are based upon the allowable stress design method as per IS:800 (1984). It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. It would not be possible to describe every aspect of IS:800 in this manual. This section, however, will discuss the salient features of the allowable stresses specified by IS:800 and implemented in STAAD. Appropriate sections of IS:800 will be referenced during the discussion of various types of allowable stresses.

Section 9B

9B.3.1 Axial Stress Tensile Stress The allowable tensile stress, as calculated in STAAD as per IS:800 is described below. The permissible stress in axial tension,  at in MPa on the net effective area of the sections shall not exceed  at = 0.6 f y where, fy


Compressive Stress Allowable compressive stress on the gross section of axially loaded compression members shall not exceed 0.6f y nor the permissible stress  ac calculated based on the following formula: (Clause: 5.1.1)   0.6

f f [(f cc)n (f y)n]

where,  ac fy fcc E =l/r n

= = = = =

Permissible stress in axial compr ession, in Mpa Yield stress of steel, in Mpa Elastic critical stress in compression = 2 E/ 2 Modulus of elasticity of steel, 2 X 10 5 Mpa Slenderness ratio of the member, ratio of the effective length to appropriate radius of gyration = A factor assumed as 1.4.

9-51


9-52

Section 9B

9B.3.2 Bending Stress The allowable bending stress in a member subjected to bending is calculated based on the following formula: (Clause: 6.2.1)  bt or  bc = 0.66 fy where,  bt = Bending stress in tension  bc = Bending stress in compression f y = Yield stress of steel, in MPa For an I-beam or channel with equal flanges bent about the axis of maximum strength (z-z axis), the maximum bending compressive stress on the extreme fibre calculated on the effective section shall not exceed the values of maximum permissible bending compressive stress. The maximum permissible bending compressive stress shall be obtained by the following formula: (Clause: 6.2.2)

σbc

 0.66

f cb  f y 1/n

(Clause : 6.2.3)

n n [(f cb)  (f y) ]

where, f y = Yield stress of steel, in Mpa n = A factor assumed as 1.4. fcb = Elastic critical stress in bending, calculated by the following formula:

f

 k [ X  k Y]

c c

Section 9B

9-53

where, X  Y 1

Y=

26.5x10 (1/ r y)

k1

= a coefficient to allow for reduction in thickness or breadth of flanges between points of effective lateral restraint and depends on , the ratio of the total area of both flanges at the point of least bending moment to the corresponding area at the point of greatest bending moment between such points of restraint.

k2

= a coefficient to allow for the inequality of flanges, and depends on , the ratio of the moment of inertia of the compression flange alone to that of the sum of the moment of the flanges each calculated about its own axis parallel to the y-yaxis of the girder, at the point of maximum bending moment.

1

= effective length of compression flange

ry

= radius of gyration of the section about its axis of minimum strength (y-y axis)

T

= mean thickness of the compression flange, is equal to the area of horizontal portion of flange divided by width.

D

= overall depth of beam

c 1 ,c 2 =

9B.3.3

1 IT MP 20 r D

respectively the lesser and greater distances from the section neutral axis to the extreme fibres.

Shear Stress Allowable shear stress calculations are based on Section 6.4 of IS:800 . For shear on the web, the gross section taken into consideration consist of the product of the total depth and the web thickness. For shear parallel to the flanges, the gross section is taken as 2/3 times the total flange area.


9-54

Section 9B

9B.3.4 Combined Stress Members subjected to both axial and bending stresses are proportioned accordingly to section 7 of IS:800. All members subject to bending and axial compression are required to satisfy the equation of Section 7.1.1.(a) for intermediate points, and equation of Section 7.1.1.(b) for support points. For combined axial tension and bending the equation of Section 7.1.2. is required to be satisfied. Cm coefficients are calculated according to the specifications of Section 7.1.3. information regarding occurrence of sidesway can be provided through the use of parameters SSY and SSZ. In the absence of any user provided information, sidesway will be assumed.

9B.4 Design Parameters In STAAD implementation of IS:800, the user is allowed complete control of the design process through the use of design parameters. Available design parameters to be used in conjunction with IS:800 are listed in Table 7B.1 of this section along with their default values and applicable restrictions. Users should note that when the TRACK parameter is set to 1.0 and use in conjunction with this code, allowable bending stresses in compression (FCY & FCZ), tension (FTY & FTZ), and allowable shear stress (FV) will be printed out in Member Selection and Code Check output in Mpa. When TRACK is set to 2.0, detailed design output will be provided.

9B.5 Stability Requirements Slenderness ratios are calculated for all members and checked against the appropriate maximum values. Section 3.7 of IS:800

Section 9B

summarizes the maximum slenderness ratios for different types of members. In STAAD implementation of IS:800, appropriate maximum slenderness ratio can be provided for each member. If no maximum slenderness ratio is provided, compression members will be checked against a maximum value of 180 and tension members will be checked against a maximum value of 400.

9B.6 Truss Members As mentioned earlier, a truss member is capable of carrying only axial forces. So in design no time is wasted in calculating bending or shear stresses, thus reducing design time considerably. Therefore, if there is any truss member in an analysis (like bracing or strut, etc.), it is wise to declare it as a truss member rather than as a regular frame member with both ends pinned.

9B.7 Deflection Check This facility allows the user to consider deflection as a criteria in the CODE CHECK and MEMBER SELECTION processes. The deflection check may be controlled using three parameters which are described in Table 7B.1. Note that deflection is used in addition to other strength and stability related criteria. The local deflection calculation is based on the latest analysis results.

9B.8 Code Checking The purpose of code checking is to verify whether the specified section is capable of satisfying applicable design code requirements. The code checking is based on the IS:800 (1984) requirements. Forces and moments at specified sections of the members are utilized for the code checking calculations. Sections may be specified using the BEAM parameter or the SECTION command. If no sections are specified, the code checking is based on forces and moments at the member ends.

9-55


9-56

Section 9B

The code checking output labels the members as PASSed or FAILed. In addition, the critical condition (applicable IS:800 clause no.), governing load case, location (distance from the start) and magnitudes of the governing forces and moments are also printed out.

9B.9 Member Selection STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, that is, the lightest section, which satisfies the applicable code requirements. The section selected will be of the same type (I-Section, Channel etc.) as originally specified by the user. Member selection may be performed with all types of steel sections listed in Section 7B.13 and user provided tables. Selection of members, whose properties are originally provided from user specified table, will be limited to sections in the user provided table. Member selection can not be performed on members whose cross sectional properties are specified as PRISMATIC. The process of MEMBER SELECTION may be controlled using the parameters listed in Table 8B.1. It may be noted that the parameters DMAX and DMIN may be used to specify member depth constraints for selection. If PROFILE parameter is provided, the search for the lightest section is restricted to that profile. Up to three (3) profiles may be provided for any member with a section being selected from each one.

9B.10 Member Selection By Optimization Steel section selection of the entire structure may be optimized. The optimization method utilizes a state-of-the -art numerical technique which requires automatic multiple analysis. The user may start without a specifically designated section. However, the section profile type (BEAM, COLUMN, CHANNEL, ANGLE etc.) must be specified using the ASSIGN command (see Chapter 6).

Section 9B

The optimization is based on member stiffness contributions and corresponding force distributions. An optimum member size is determined through successive analysis/design iterations. This method requires substantial computer time and hence should be used with caution.

9B.11 Tabulated Results of Steel Design For code checking or member selection, the program produces the result in a tabulated fashion. The items in the output table are explained as follows: a) MEMBER refers to the member number for which the design is performed b) TABLE refers to the INDIAN steel section name which has been checked against the steel code or has been selected. c) RESULT prints whether the member has PASSED or FAILed. If the RESULT is FAIL, there will be an asterisk (*) mark in front of the member number. d) CRITICAL COND refers to the section of the IS:800 code which governs the design. e) RATIO prints the ratio of the actual stresses to allowable stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed. f)

LOADING provides the load case number which governs the design.

g) FX, MY and MZ provide the axial force, moment in local yaxis and moment in local z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX,MY and MZ are printed since they are the ones which are of interest , in most cases.

9-57


9-58

Section 9B

h) LOCATION specifies the actual distance from the start of the member to the section where design forces govern. i)

If the parameter TRACK is set to 1.0, the program will block out part of the table and will print allowable bending stress es in compression (FCY & FCZ) and tension (FTY & FTZ), allowable axial stress in compression (FA), and allowable shear stress (FV). When the parameter TRACK is set to 2.0 for all members parameter code values are as shown in Fig 8B.1. STAAD.Pro CODE CHECKING - (ISA ) *********************** |---------------------------------------------------------------------------| | Y PROPERTIES | |************* | IN CM UNIT | | * |=============================| ===|=== ------------ | |MEMBER 7 * | | | AX = 72.4 | | * | ST ISLB400 | | --Z AY = 32.0 | |DESIGN CODE * | | | AZ = 27.5 | | IS-800 * =============================== ===|=== SY = 86.8 | | * SZ = 965.3 | | * |<---LENGTH (ME= 3.00 --->| RY = 3.1 | |************* RZ = 16.3 | | | | 104.6( KN-METR) | |PARAMETER |L1 STRESSES | |IN NEWT MM | IN NEWT MM| |--------------- + -------------| | KL/R-Y= 95.4 | FA = 84.8 | | KL/R-Z= 18.4 + fa = 1.6 | | UNL = 3000.0 | FCZ = 116.6 | | C = 400.0 + FTZ = 165.0 | | CMY = 0.85 | FCY = 165.0 | | CMZ = 0.85 + FTY = 165.0 | | FYLD = 249.9 | L3 fbz = 108.4 | | NSF = 0.9 +---+---+---+---+---+---+---+---+---+---| fby = 0.0 | | DFF = 325.0 92.7 FV = 100.0 | | dff = 4383.0 ABSOLUTE MZ ENVELOPE | | (WITH LOAD NO.) | | | | MAX FORCE/ MOMENT SUMMARY ( KN-METR) | | ------------------------| | | | AXIAL SHEAR-Y SHEAR-Z MOMENT-Y MOMENT-Z | | | | VALUE -23.7 61.3 0.0 0.0 104.6 | | LOCATION 0.0 0.0 0.0 0.0 0.0 | | LOADING 3 1 0 0 1 | | | |***************************************************************************| |* *| |* DESIGN SUMMARY ( KN-METR) *| |* -------------*| |* *| |* RESULT/ CRITICAL COND/ RATIO/ LOADING/ *| | FX MY MZ LOCATION | | ====================================================== | | PASS IS-7.1.2 0.667 1 | | 9.62 T 0.0 -104.6 0.00 | | | | DEFLECTION * PASS | | RATIO: 0.074 LOADING: 3 LOCATION: 0.67 | |* *| |***************************************************************************|

Section 9B

9B.12 Indian Steel Table This is an important feature of the program since the program will read section properties of a steel member directly from the latest ISI steel tables (as published in ISI-800). These properties are stored in memory corresponding to the section designation (e.g. ISMB250, etc.). If called for, the properties are also used for member design. Since the shear areas are built in to these tables, shear deformation is always considered for these members. Almost all ISI steel tables are available for input. A complete listing of the sections available in the built -in steel section library may be obtained using the tools of the graphical user interface. Following are the descriptions of all the types of sections available: Rolled Steel Beams (ISJB, ISLB, ISMB and ISHB). All rolled steel beam sections are available the way they are designated in the ISI handbook., e.g. ISJB225, ISWB400, etc.

20 TO 30 TA ST ISLB325 NOTE: In case of two identical beams, the heavier beam is designated with an „A” on the end., e.g. ISHB400 A, etc.

1 TO 5 TA ST ISHB400A

9-59


9-60

Section 9B

Rolled Steel Channels (ISJC, ISLC and ISMC) All these shapes are available as listed in ISI section handbook. Designation of the channels are per the scheme used by ISI.

10 TO 20 BY 2 TA ST ISMC125 12 TA ST ISLC300 Double Channels Back to back double channels, with or without spacing between them, are available. The letter D in front of the section name will specify a double channel, e.g. D ISJC125, D ISMC75 etc.

21 22 24 TA D ISLC225 Rolled Steel Angles Both rolled steel equal angles and unequal angles are available for use in the STAAD implementation of ISI steel tables. The following example with explanations will be helpful in understanding the input procedure: ISA 150 X 75 X 8 Angle symbol

Thickness in mm

Long leg length in mm

Short leg length in mm

At present there is no standard way to define the local y and z axes for an angle section. The standard section has local axis system as illustrated in Fig.2.4 of this manual. The standard angle is specified as:

51 52 53 TA ST ISA60X60X6

Section 9B

This specification has the local z-axis ( i.e., the minor axis corresponding to the V-V axis specified in the steel tables. Many engineers are familiar with a convention used by some other programs in which the local y-axis is the minor axis. STAAD provides for this convention by accepting the command:

54 55 56 TA RA ISA50X30X6

(RA denotes reverse angle)

Double Angles Short leg back to back or long leg back to back double angles can be specified by inputting the word SD or LD, respectively, in front of the angle size. In case of an equal angle either LD or SD will serve the purpose. For example,

14 TO 20 TA LD ISA50X30X5 SP 1.5 23 27 TA SD ISA75X50X6 Rolled Tees (ISHT, ISST, ISLT and ISJT) All the rolled tee sections are available for input as they are specified in the ISI handbook. Following example illustrates the designated method.

1 2 5 8 TA ST ISNT100 67 68 TA ST ISST250 Pipes (Circular Hollow Sections) To designate circular hollow sections from ISI tables, use PIP followed by the numerical value of diameter and thickness of the section in mm omitting the decimal section of the value provi ded for diameter. Following example will illustrate the designation.

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9-62

Section 9B

10 15 TA ST PIP 213.2 (Specifies a 213 mm dia. pipe with 3.2 mm wall thickness) Circular pipe sections can also be specified by providing the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0ID 20.0 (specifies a pipe with outside dia. of 25 and inside dia. of 20 in current length units) Only code checking and no member selection will be performed if this type of specification is used. Tubes (Rectangular or Square Hollow Sections) Designation of tubes from the ISI steel table is illustrated below. TUB 400 200 12.5 Tube Symbol

Thickness in mm

Height in mm

Width in mm

Example:

15 TO 25 TA ST TUB 160808 Tubes, like pipes, can also be input by their dimensions (Height, Width and Thickness) and not by any table designations.

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height of 8, a width of 6, and a wall thickness of 0.5.

Section 9B

Note that only code checking and no member selection is performed for TUBE sections specified this way. Plate And Angle Girders (With Flange Plates) All plate and angle grinders (with flange plates) are available as listed in ISI section handbook. The following example with explanations will be helpful in understanding the input procedure. I 1000 12 A 400 12

A

F B

E C

A B C D E F

D

Plate and angle girder symbol. Web plate width in mm. Web plate thickness in mm. Flange angle (Flange angle key below): Flange plate width in mm. Flange plate thickness in mm.

SYMBOL

ANGLE(A X B X t)(all in mm)

A B C E

150X150X18 200X100X15 200X150X18 200X200X18

9-63


9-64

Section 9B

SINGLE JOIST WITH CHANNELS AND PLATES ON THE FLANGES TO BE USED AS GIRDERS All single joist with channel and plates on the flanges to be used as girders are available as listed in ISI section handbook. The following example with explanations will be helpful in understanding the input procedure. IW 450 350 X 10 20 A

E B

D C

A

Joist Designation:

IW450=ISWB450

B

Top flange channel designation: 350=ISMC350

C

Constant (always X).

D

Top flange plate thickness in mm. NOTE: D is 0 for no plate.

E

Bottom flange plate thickness in mm.

NOTE: The heavier ISWB600 has been omitted, since the lighter ISWB600 is more efficient.

Section 9B

9-65

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 9B.1 Indian Steel Design - IS : 800 Parameters Parameter Name

Default Value

Description

KY

1.0

K value in local y-axis. Usually, this is minor axis.

KZ

1.0

K value in local z-axis. Usually, this is major axis.

LY

Member Length


LZ

Member Length

Same as above except in local z-axis (major).

FYLD

250 MPA (36.25 KSI)


NSF

1.0

UNL

Member Length

UNF

1.0

Same as above provided as a fraction of actual member length.

SSY

0.0


SSZ

0.0


CMY CMZ MAIN TMAIN

TRACK

0.85 for sidesway and calculated for no sidesway

Net section factor for tension members. Unsupported length for calculating allowable bending stress.

Cm value in local y & z axes

180 (Comp. Memb.)

Allowable Kl/r for slenderness calculations for compression members.

400 (Tension Memb)

Allowable Kl/r for slenderness calculations for tension members.

0.0

0.0 = Suppress critical member stresses 1.0 = Print all critical member stresses 2.0 = Print expanded output. If there is deflection check it will also print the governing load case number for deflection check whenever critical condition for design is not DEFLECTION. (see fig.8B.1)


9-66

Section 9B

Table 9B.1 Indian Steel Design - IS : 800 Parameters Parameter Name

Default Value

Description

DMAX

100.0 cm.


DMIN

0.0 cm.


RATIO

1.0


3.0

0.0 = design only for end moments and those at locations specified by the SECTION command. 1.0 = calculate section forces at twelfth points along the beam, design at each intermediate location and report the critical location where ratio is maximum.

BEAM

-

Search for the lightest section for the profile mentioned.

DFF



DJ1



DJ2

End Joint of member


PROFILE

NOTES: 1) "Deflection Length" is defined as the length that is used for calculation of local deflections within a member. It may be noted that for most cases the "Deflection Length" will be equal to the length of the member. However, in some situations, the "Deflection Length" may be different. For example, refer to the figure below where a beam has been modeled using four joints and three members. Note that the "Deflection Length" for all three members will be equal to the total length of the beam in this case. The parameters DJ1 and DJ2 should be used to model this situation. Also the straight line joining DJ1 and DJ2 is used as the reference line from which local deflections are measured. Thus, for all three members here, DJ1 should be "1" and DJ2 should be "4".

Section 9B

1

2 1

3 2

EXAMPLE :

4 3 D

D = Maximum local deflection for members 1 2 and 3.


2) If DJ1 and DJ2 are not used, "Deflection Length" will default to the member length and local deflections will be measured from original member line. 3) The above parameters may be used in conjunction with other available parameters for steel design.

9B.13 Column With Lacings And Battens For columns with large loads it is desirable to build rolled sections at a distance and inter-connect them. The joining of element sections is done by two ways: a) Lacing and b) Batten Double channel sections (back-to-back and face-to-face) can be joined either by lacing or by batten plates having rivetted or welded connection. Table 8B.2 gives the parameters that are required for Lacing or batten design. These parameters will have to be provided in unit NEW MMS along with parameters defined in Table 9B.1.

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9-68

Section 9B

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 9B.2 Indian Concrete Design IS800 Parameters Parameter Name CTYPE

Default Value 1

Description Type of joining CTYPE = 1 implies single lacing with rivetted connection CTYPE = 2 implies double lacing with rivetted connection CTYPE = 3 implies single lacing with welded connection CTYPE = 4 implies double lacing with welded connection CTYPE = 5 implies batten with rivetted connection CTYPE = 6 implies batten with welded connection

THETA

50 degree

Angle of inclination of lacing bars. It should lie between 40 degree and 70 degree.

DBL FVB

20 mm 100 N/mm2

Nominal diameter of rivet Allowable shear stress in rivet

FYB

300 N/mm2

Allowable bearing stress in rivet

WMIN

6 mm

Minimum thickness of weld 2

WSTR

108 N/mm

EDIST

32 mm (Rivetted Connection) 25 mm (Welded Connection)

Allowable welding stress Edge Distance

Section 9B

9-69

Table 9B.2 Indian Concrete Design IS800 Parameters Parameter Name DCFR

Default Value 0.0

Description 0.0 implies double channel back-to-back. 1.0 Implies double channel face-to-face. This parameter is used when member properties are defined through user provided table using GENERAL option.

COG

0.0 mm

Centre of gravity of the channel. This parameter is used when member properties are defined through user provided table using GENERAL option.

SPA

0.0 mm

Spacing between double channels. This parameter is used when member properties are defined through user provided table using GENERAL option.


9-70

Section 9B

9-71

Steel Design Per IS802 Section

9C

9C.1 General Comments This section presents some general statements regarding the implementation of Indian Standard code of practice (IS:802 -1995 – Part 1) for structural steel design for overhead transmission line towers in STAAD. The design philosophy and procedural logistics for member selection and code checking are based upon the principles of allowable stress design. Two major failure modes are recognized: failure by overstressing, and failure by stability considerations. The flowing sections describe the salient features of the allowable stresses being calculated and the stability criteria being used. Members are proportioned to resist the design loads without exceeding the allowable stresses and the most economic section is selected on the basis of least weight criteria. The code checking part of the program checks stability and strength requirements and reports the critical loading condition and the governing code criteria.

9C.2 Allowable Stresses The member design and code checking in STAAD are based upon the allowable stress design method as per IS:802 (1995). It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. This section discusses the salient features of the allowable stresses specified by IS:802 and implemented in STAAD.


9-72

Section 9C

9C.2..1 Axial Stress Tensile Stress The allowable tensile stress, as calculated in STAAD as per IS:802 is described below. The estimated tensile stresses on the net effective sectional area in various members, multiplied by the appropriate factor of safety shall not exceed minimum guaranteed yield stress of the material. Thus, the permissible stress in axial tension,  at in MPa on the net effective area of the sections shall not exceed  at = fy where, fy


Compressive Stress The estimated compressive stresses in various members multiplied by the appropriate factor of safety shall not exceed the value given by the formulae described below.

b

 b 

 Condition 1: If        t    t  lim 

210   Fy 

KL / r  CC

 1  KL / r  2  Stress F a = 1     Fy N/mm 2   2  Cc   KL / r  CC

Section 9C

 E 2

Stress F a =

KL / r 

2

N/mm 2

b   t  lim

Condition 2: If  

 b  378 when F y is the N/mm 2   Fy t

formulae given in condition 1 shall be used substituting for F y the value F cr given by:   b  0.677     t  F F cr = 1.677    y b      t lim  

 b  378 Condition 3:   > when F y is the N/mm 2 formulae given in Fy t

condition 1 shall be used substituting for F y the value F cr given by F cr =

65550 b   t

2

In which C C =  2E Fy where, F a = allowable unit stress in compression, Mpa F y = minimum guaranteed yield stress of the material, Mpa K = restraint factor, L = unbraced length of the compression member in cm, and R = appropriate radius of gyration in cm. E = modulus of elasticity of steel in N/mm 2

9-73


9-74

Section 9C

KL = largest effective slenderness ratio of any unbraced segment r of the member,

b = distance from edge of the fillet to the extreme fibre in mm, and t = thickness of flange in mm. Note : The maximum permissible value of b/t for any type of steel shall not exceed 25.

9C.3 Stability Requirements Slenderness ratios are calculated for all members and checked against the appropriate maximum values. Following are the default values used in STAAD: Compression Members: Members

Slenderness value

Leg Members, ground wire peak member and lower members of cross arms in compression

120

Other members carrying computed stress

200

Redundant members and those carrying nominal stresses

250

Section 9C

Slenderness ratios of compression members are determined as follows: ELA NO.

Type of members

Value of KL/r

1

Leg sections or joint members bolted at connections in both faces

L/r

2

Members with concentric loading at both ends of the unsupported panel with values of L/r up to and including 120

L/r

3

Member with concentric loading at one end and normal eccentricities at the other end of the unsupported panel for value of L/r up to and including 120

30 + 0.75L/r

4

Members with normal framing eccentricities at both ends of the unsupported panel for values of L/r up to and including 120

60 + 0.5L/r

5

Member unrestrained against rotation at both ends of the unsupported panel for value of L/r from 120 to 200

L/r

6

Members partially restrained against rotation at one end of the unsupported panel for values of L/r over 120 and up to and including 225

28.6 + 0.762L/r

7

Members partially restrained against rotation at both ends of the unsupported panel for values of L/r over 120 and up to and including 250

46.2 + 0.615L/r

If ELA number given in the input for any particular member is such that condition for L/r ratio to fall within the specified range is not satisfied, STAAD goes on by the usual way of finding slenderness ratio using K*L/r formula.

9-75


9-76

Section 9C

Tension Members: Slenderness ratio KL/r of a member carrying axial tension only, shall not exceed 400.

9C.4 Minimum Thickness Requirement As per Clause7.1 of IS: 802-1995 minimum thickness of different tower members shall be as follows: Members Leg Members, ground wire peak member and lower members of cross arms in compression Other members

Minimum Thickness, mm Galvanized Painted 5

6

4

5

9C.5 Code Checking The purpose of code checking is to verify whether the specified section is capable of satisfying applicable design code requirements. The code checking is based on the IS:802 (1995) requirements. Axial forces at two ends of the members are utilized for the code checking calculations. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from the start) and magnitudes of the governing forces are also printed out. Using TRACK 9 option calculation steps are also printed.

Section 9C

9C.5.1 Design Steps The following are the steps followed in member design. Step 1 Thickness of the member (maximum of web and flange thicknesses) is checked against minimum allowable thickness, depending upon whether the member is painted or galvanised. Step 2 If the minimum thickness criterion is fulfilled, the program determines whether the member is under compression or tension for the loadcase under consideration. Depending upon whether the member is under tension or compression the slenderness ratio of the member is calculated. This calculated ratio is checked against allowable slenderness ratio. Step 3 If the slenderness criterion is fulfilled check against allowable stress is performed. Allowable axial and tensile stresses are calculated. If the member is under tension and there is no user defined net section factor (NSF), the net section factor is calculated by the program itself (Refer Section 8C.10). Actual axial stress in the member is calculated. The ratio for actual stress to allowable stress, if less than 1.0 or user defined value, the member has passed the check. Step 4 Number of bolts required for the critical loadcase is calculated.

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9-78

Section 9C

9C.6 Member Selection STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, that is, the lightest section, which satisfies the applicable code requirements. The section selected will be of the same type (either angle or channel) as originally specified by the user. Member selection may be performed with all angle or channel sections and user provided tables. Selection of members, whose properties are originally provided from user specified table, will be limited to sections in the user provided table. The process of MEMBER SELECTION may be controlled using the parameters listed in Table 8B.1. It may be noted that the parameters DMAX and DMIN may be used to specify member depth constraints for selection. If PROFILE parameter is provided, the search for the lightest section is restricted to that profile. Up to three (3) profiles may be provided for any member with a section being selected from each one.

9C.7 Member Selection by Optimization Steel section selection of the entire structure may be optimized . The optimization method utilizes a state-of-the -art numerical technique which requires automatic multiple analysis. The optimization is based on member stiffness contributions and corresponding force distributions. An optimum member size is determined through successive analysis/design iterations. This method requires substantial computer time and hence should be used with caution.

Section 9C

9C.8 Tabulated Results of Steel Design

DETAILS OF CALCULATION ---------------------CHECK FOR MINIMUM THICKNESS --------------------------TYPE : GALVANISED MIN. ALLOWABLE THICKNESS : 5.0 MM ACTUAL THICKNESS : 10.0 MM RESULT : PASS

9-79


9-80

Section 9C

CHECK FOR SLENDERNESS RATIO --------------------------VALUE OF L/r : 90.16 EQN. USED TO FIND KL/r : 60.0 + 0.5 *L/r ACTUAL VALUE OF KL/r : 105.08 ALLOWABLE KL/r : 120.00 RESULT : PASS

CALCULATION OF ALLOWABLE STRESS -------------------------------CRITICAL CONDITION : COMPRESSION Cc : sqrt(2 *3 .141592*3.1 41592*E/fy) : 127.22 b : LENGTH OF LEG - WEB THICKNESS - ROOT RADIUS : 150.0 - 10.0 - 11.0 : 129.0 MM (b/t)lim : 210/sqrt(fy)

: 13.28

(b/t)cal : 12.90 (b/t)cal <= (b/t)lim AND KL/r <= Cc ALLOWABLE AXIAL COMP. STRESS : (1 -0.5 *(KL/r/Cc)*(KL/r/Cc))*fy 164.72 MPA CHECK AGAINST PERMISSIBLE STRESS -------------------------------DESIGN AXIAL FORCE : 250000.00 N ACTUAL AXIAL COMP. STRESS : 250000.00 / 2552.0 : 97.96 MPA RESULT : PASS BOLTING ------BOLT DIA : 16 MM SHEARING CAP : 20.11 KN BEARING CAP : 38.40 KN BOLT CAP : 20.11 KN NO. OF BOLT S REQD. : 13

:

Section 9C

9-81

9C.9 Parameter Table for IS 802 Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 9C.1 Indian Steel Design - IS 802 Parameters Parameter Name

Default Value

Description

KY

1.0

K value in local y-axis. Usually, this is minor axis.

KZ

1.0


LY

Member Length

Unbraced length in local z-axis to calculate slenderness ratio.

LZ

Member Length

Unbraced length in local z-axis to calculate slenderness ratio.

FYLD

250 MPA

MAIN

1.0

Yield Strength of steel Type of member to find allowable Kl/r for slenderness calculations for members. 1.0 = Leg, Ground wire peak and lower members of cross arms in compression (KL/r = 120) 2.0 = Members carrying computed stress (KL/r = 200) 3.0 = Redundant members and members carrying nominal stresses (KL/r = 250) 4.0 = Tension members (KL/r = 400) 10.0 = Do not perform KL/r check Any value greater than 10.0 indicates user defined allowable KL/r ratio. For this case KY and KZ values are must to find actual KL/r ratio of the member.

DMAX

100.0 cm.


DMIN

0.0 cm.



9-82

Section 9C

Table 9C.1 Indian Steel Design - IS 802 Parameters Parameter Name TRACK

Default Value 0.0

Description 0.0 = Suppress critical member stresses 1.0 = Print all critical member stresses 2.0 =

Print expanded output.

9.0 = Print design calculations along with expanded output. LEG

1.0

This parameter is meant for plain angles. 0.0 = indicates the angle is connected by shorter leg 1.0 = indicates the angle is connected by longer leg

ELA

1.0

This parameter indicates what type of end conditions is to be used. Refer Section 8C.3.

NSF

1.0

Net section factor for tension members

CNSF

0.0

This parameter indicates whether user has defined NSF or the program will calculate it. 0.0 = User has defined NSF 1.0 = Program has to calculate it

DANGLE

0.0

This parameter indicates how the pair of angles are connected to each other. This is required to find whether the angle is in single or double shear and the net section factor. 0.0 = Double angle placed back to back and connected to each side of a gusset plate 1.0 = Pair of angle placed back-to-back connected by only one leg of each angle to the same side of a gusset plate�

DBL

12 mm

Diameter of bolt for calculation of number of bolts and net section factor.

FVB

218 MPA

Allowable shear stress in bolt

FYB

436 MPA

Allowable bearing stress in bolt

Section 9C

9-83

Table 9C.1 Indian Steel Design - IS 802 Parameters Parameter Name GUSSET

Default Value 5 mm

Description Thickness of gusset plate. Minimum of the thicknesses of the gusset plate and the leg is used for calculation of the capacity of bolt in bearing

NHL

0.0 mm

Deduction for holes. Default value is one bolt width plus 1.5 mm. If the area of holes cut by any straight, diagonal or zigzag line across the member is different from the default value, this parameter is to be defined.

9C.10 Calculation of Net Section Factor The procedure for calculating net section factor for angle section is described below. Single angle connected by only one leg A net = A 1 + A 2 x K 1 Where, A 1 = net cross-sectional area of the connected leg A 2 = gross cross-sectional area of the unconnected leg And K 1 =

3xA1 3xA1  A2

The area of a leg of an angle = Thickness of angle x (length of leg – 0.5x thickness of leg)


9-84

Section 9C

Pair of angles placed back-to-back connected by only one leg of each angle to the same side of a gusset plate A net = A 1 + A 2 x K 1 Where A 1 = net cross-sectional area of the connected leg A 2 = gross cross-sectional area of the unconnected leg And K 1 =

5 xA1 5 xA1  A2

The area of a leg of an angle = Thickness of angle x (length of leg – 0.5x thickness of leg) Double angles placed back to back and connected to each side of a gusset plate A net = gross area – deduction for holes Net Section Factor For angle section it is the ratio of the net effective area, A net to the gross area. For channel section net section factor is taken to be 1.0.

Section 9C

9C.11 Example Problem No. 28 A transmission line tower is subjected to different loading conditions. Design some members as per IS-802 and show detailed calculation steps for the critical loading condition.

Given:

End Condition = Members with normal framing eccentricities at both ends of the unsupported panel for values of L/r up to and including 120 Diameter of the bolt = 16 mm Thickness of the gusset plate = 8 mm Net Section Factor is to be calculated.

9-85


9-86

Section 9C

STAAD TRUSS INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 3 0 3; 2 1.2 27 1.2; 3 2.8 3 2.8; 4 2.6 6 2.6; 5 2.4 9 2.4; 6 2.2 12 2.2; 7 2 15 2; 8 1.8 18 1.8; 9 1.6 21 1.6; 10 1.4 24 1.4; 11 -3 0 3; 12 -1.2 27 1.2; 13 -2.8 3 2.8; 14 -2.6 6 2.6; 15 -2.4 9 2.4; 16 -2.2 12 2.2; 17 -2 15 2; 18 -1.8 18 1.8; 19 -1.6 21 1.6; 20 -1.4 24 1.4; 21 3 0 -3; 22 1.2 27 -1.2; 23 2.8 3 -2.8; 24 2.6 6 -2.6; 25 2.4 9 -2.4; 26 2.2 12 -2.2; 27 2 15 -2; 28 1.8 18 -1.8; 29 1.6 21 -1.6; 30 1.4 24 -1.4; 31 -3 0 -3; 32 -1.2 27 -1.2; 33 -2.8 3 -2.8; 34 -2.6 6 -2.6; 35 -2.4 9 -2.4; 36 -2.2 12 -2.2; 37 -2 15 -2; 38 -1.8 18 -1.8; 39 -1.6 21 -1.6; 40 -1.4 24 -1.4; 41 1.2 30 1.2; 42 -1.2 30 1.2; 43 1.2 30 -1.2; 44 -1.2 30 -1.2; 45 4.2 27 1.2; 46 7.2 27 1.2; 47 4.2 30 1.2; 48 4.2 27 -1.2; 49 7.2 27 -1.2; 50 4.2 30 -1.2; 51 -4.2 27 1.2; 52 -7.2 27 1.2; 53 -4.2 30 1.2; 54 -4.2 27 -1.2; 55 -7.2 27 -1.2; 56 -4.2 30 -1.2; 57 1.2 33 1.2; 58 -1.2 33 1.2; 59 1.2 33 -1.2; 60 -1.2 33 -1.2; 61 0 35 0; MEMBER INCIDENCES 1 1 3; 2 3 4; 3 4 5; 4 5 6; 5 6 7; 6 7 8; 7 8 9; 8 9 10; 9 10 2; 10 11 13; 11 13 14; 12 14 15; 13 15 16; 14 16 17; 15 17 18; 16 18 19; 17 19 20; 18 20 12; 19 13 3; 20 14 4; 21 15 5; 22 16 6; 23 17 7; 24 18 8; 25 19 9; 26 20 10; 27 12 2; 28 11 3; 29 1 13; 30 13 4; 31 3 14; 32 14 5; 33 15 4; 34 15 6; 35 16 5; 36 16 7; 37 17 6; 38 17 8; 39 18 7; 40 18 9; 41 19 8; 42 19 10; 43 20 9; 44 20 2; 45 12 10; 46 21 23; 47 23 24; 48 24 25; 49 25 26; 50 26 27; 51 27 28; 52 28 29; 53 29 30; 54 30 22; 55 3 23; 56 4 24; 57 5 25; 58 6 26; 59 7 27; 60 8 28; 61 9 29; 62 10 30; 63 2 22; 64 1 23; 65 21 3; 66 3 24; 67 23 4; 68 4 25; 69 5 24; 70 5 26; 71 6 25; 72 6 27; 73 7 26; 74 7 28; 75 8 27; 76 8 29; 77 9 28; 78 9 30; 79 10 29; 80 10 22; 81 2 30; 82 31 33; 83 33 34; 84 34 35; 85 35 36; 86 36 37; 87 37 38; 88 38 39; 89 39 40; 90 40 32; 91 23 33; 92 24 34; 93 25 35; 94 26 36; 95 27 37; 96 28 38; 97 29 39; 98 30 40; 99 22 32; 100 21 33; 101 31 23; 102 23 34; 103 33 24; 104 24 35; 105 25 34; 106 25 36; 107 26 35; 108 26 37; 109 27 36; 110 27 38; 111 28 37; 112 28 39; 113 29 38; 114 29 40; 115 30 39; 116 30 32; 117 22 40; 118 33 13; 119 34 14; 120 35 15; 121 36 16; 122 37 17; 123 38 18; 124 39 19; 125 40 20; 126 32 12; 127 31 13; 128 11 33; 129 33 14; 130 13 34; 131 34 15; 132 35 14; 133 35 16; 134 36 15; 135 36 17; 136 37 16; 137 37 18; 138 38 17; 139 38 19; 140 39 18; 141 39 20; 142 40 19; 143 40 12; 144 32 20; 145 32 44; 146 12 42; 147 2 41; 148 22 43; 149 42 41; 150 41 43; 151 43 44; 152 44 42; 153 12 41; 154 42 2; 155 22 41; 156 43 2; 157 43 32; 158 44 22; 159 12 44; 160 32 42; 161 41 47; 162 47 45; 163 45 2; 164 47 46; 165 46 45; 166 41 45; 167 43 50; 168 50 48; 169 48 22; 170 50 49; 171 49 48; 172 43 48; 173 47 50; 174 46 49; 175 45 48; 176 41 50; 177 50 46; 178 43 47; 179 47 49; 180 22 50; 181 2 47; 182 22 45; 183 2 48; 184 47 48; 185 50 45; 186 45 49; 187 48 46; 188 42 53; 189 53 51; 190 51 12; 191 53 52; 192 52 51; 193 42 51; 194 44 56; 195 56 54; 196 54 32; 197 56 55; 198 55 54; 199 44 54; 200 53 56; 201 52 55; 202 51 54; 203 42 56; 204 56 52; 205 44 53; 206 53 55; 207 32 56; 208 12 53; 209 32 51; 210 12 54; 211 53 54; 212 56 51; 213 51 55; 214 54 52; 215 44 60; 216 42 58; 217 41 57; 218 43 59; 219 60 59; 220 59 57; 221 57 58; 222 58 60; 223 44 58; 224 42 60; 225 42 57; 226 41 58; 227 44 59; 228 43 60; 229 43 57; 230 41 59; 231 60 57; 232 59 58; 235 33 3; 236 13 23; 237 34 4; 238 14 24; 239 35 5; 240 15 25; 241 36 6; 242 16 26; 243 37 7; 244 17 27; 245 38 8; 246 18 28; 247 39 9; 248 19 29; 249 40 10; 250 20 30; 251 32 2; 252 22 12; 253 44 41; 254 43 42;

Section 9C 255 60 61; 256 58 61; 257 57 61; 258 59 61; MEMBER PROPERTY INDIAN 1 TO 18 46 TO 54 82 TO 90 145 TO 148 215 TO 218 TA LD ISA200X150X18 SP 0.01 19 TO 26 28 TO 45 55 TO 62 64 TO 81 91 TO 98 100 TO 125 127 TO 144 155 156 159 160 223 224 229 230 235 TO 250 TA ST ISA150X150X10 27 63 99 126 149 TO 154 157 158 161 TO 214 219 TO 222 225 TO 228 231 232 251 252 TO 258 TA ST ISA80X50X6 CONSTANTS E 2.05e+008 ALL POISSON 0.3 ALL DENSITY 76.8195 ALL ALPHA 6.5e-006 ALL SUPPORTS 1 11 21 31 FIXED UNIT METER KG LOAD 1 VERT SELFWEIGHT Y -1 JOINT LOAD 61 FX 732 46 49 52 55 FX 153 61 FX 1280 FY -1016 FZ 160 46 49 52 55 FX 9006 FY -7844 FZ 1968 2 12 22 32 FX 4503 FY -3937 FZ 1968 LOAD 2 GWBC SELFWEIGHT Y -1 JOINT LOAD 61 FX 549 46 49 52 55 FX 1148 61 FX 515 FY -762 FZ 2342 46 49 52 55 FX 6755 FY -5906 2 12 22 32 FX 3378 FY -2953 LOAD 3 LEFT PCBC SELFWEIGHT Y -1 JOINT LOAD 61 FX 549 46 49 52 55 FX 1148 61 FX 960 FY -762 46 49 FX 6755 FY -5906 52 55 FX 4211 FY -4551 FZ 13293 2 12 22 32 FX 3378 FY -2953 LOAD 4 RIGHT PCBC SELFWEIGHT Y -1 JOINT LOAD 61 FX 549 46 49 52 55 FX 1148 61 FX 960 FY -762 52 55 FX 6755 FY -5906 46 49 FX 4211 FY -4551 FZ 13293 2 12 22 32 FX 3378 FY -2953 PERFORM ANALYSIS UNIT NEW MMS PARAMETER CODE IS802

9-87


9-88

Section 9C

LY 2800 MEMB 28 LZ 2800 MEMB 28 MAIN 1.0 MEMB 1 ELA 4 MEMB 1 CNSF 1.0 MEMB 28 DBL 16 ALL GUSSET 8 ALL TRACK 9 ALL CHECK CODE MEMB 1 28 FINISH

Output of design result

Section 9C DETAILS OF CALCULATION ---------------------CHECK FOR MINIMUM THICKNESS --------------------------TYPE : PAINTED MIN. ALLOWABLE THICKNESS : 6.0 MM ACTUAL THICKNESS : 18.0 MM RESULT : PASS CHECK FOR SLENDERNESS RATIO --------------------------VALUE OF L/r : 48.49 EQN. USED TO FIND KL/r : 60.0 + 0.5*L/r ACTUAL VALUE OF KL/r : 84.25 ALLOWABLE KL/r : 120.00 RESULT : PASS CALCULATION OF ALLOWABLE STRESS --------------------------------CRITICAL CONDITION : COMPRESSION Cc : sqrt (2*3.141592*3.141592*E/fy) : 127.24 b : LENGTH OF LEG - WEB THICKNESS - ROOT RADIUS : 200.0 - 18.0 - 13.5 : 168.5 MM (b/t)lim : 210/sqrt(fy)

: 13.28

(b/t)cal : 9.36 (b/t)cal <= (b/t)lim AND KL/r <= Cc ALLOWABLE AXIAL COMP. STRESS : (1195.15 MPA

0.5*(KL/r/Cc)*(KL/r/Cc))*fy :

CHECK AGAINST PERMISSIBLE STRESS -------------------------------LOAD NO. :

1

DESIGN AXIAL FORCE : 1742002.38 N ACTUAL AXIAL COMP. STRESS :1742002.38 / 11952.0 : 145.75 MPA RESULT : PASS

9-89


9-90

Section 9C BOLTING ------BOLT DIA : 16 MM SHEARING CAP : 87.66 KN BEARING CAP : 55.81 KN BOLT CAP : 55.81 KN NO. OF BOLTS REQD. : 32

Section 9C DETAILS OF CALCULATION ---------------------CHECK FOR MINIMUM THICKNESS --------------------------TYPE : PAINTED MIN. ALLOWABLE THICKNESS : 6.0 MM ACTUAL THICKNESS : 10.0 MM RESULT : PASS CHECK FOR SLENDERNESS RATIO --------------------------VALUE OF L/r : 95.56 EQN. USED TO FIND KL/r : K*L/r ACTUAL VALUE OF KL/r : 95.56 ALLOWABLE KL/r : 400.00 RESULT : PASS CALCULATION OF ALLOWABLE STRESS --------------------------------CRITICAL CONDITION : TENSION ALLOWABLE AXIAL TENSILE STRESS : 249.94 MPA CHECK AGAINST PERMISSIBLE STRESS -------------------------------LOAD NO. :

3

DESIGN AXIAL FORCE : 112909.27 N ACTUAL AXIAL TENSILE STRESS : 112909.27 / ( 2903.0*0.801 ) : 48.53 MPA RESULT : PASS BOLTING ------BOLT DIA : 16 MM SHEARING CAP : 43.83 KN BEARING CAP : 55.81 KN BOLT CAP : 43.83 KN NO. OF BOLTS REQD. : 3 ********** END OF TABULATED RESULT OF DESIGN ***********

9-91


9-92

Section 9C

9-93

Design Per Indian Cold Formed Steel Code Section

9D

9D.1 General Provisions of IS:801-1975, including revisions dated May, 1988, have been implemented. The program allows design of single (non-composite) members in tension, compression, bending, shear, as well as their combinations. Cold work of forming strengthening effects has been included as an option.

9D.2 Cross-Sectional Properties The user specifies the geometry of the cross-section by selecting one of the section shape designations from the Gross Section Property Tables from IS:811-1987 (Specification for cold formed light gauge structural steel sections). The Tables are currently available for the following shapes: 

Channel with Lips






Angle without Lips



Z with Lips



Hat

Shape selection may be done using the member property pages of the graphical user interface (GUI) or by specifying the section designation symbol in the input file.

Design Per Indian Cold Formed Steel Code

9-94

Section 9D

The properties listed in the tables are gross section properties. STAAD.Pro uses unreduced section properties in the structure analysis stage. Both unreduced and effective section properties are used in the design stage, as applicable.

9D.3 Design Procedure The following two design modes are available: 1.

Code Checking The program compares the resistance of members with the applied load effects, in accordance with IS:801-1975. Code checking is carried out for locations specified by the user via the SECTION command or the BEAM parameter. The results are presented in a form of a PASS/FAIL identifier and a RATIO of load effect to resistance for each member checked. The user may choose the degree of detail in the output data by setting the TRACK parameter.

2.

Member Selection The user may request that the program search the cold formed steel shapes database (IS standard sections) for alternative members that pass the code check and meet the least weight criterion. In addition, a minimum and/or maximum acceptable dep th of the member may be specified. The program will then evaluate all database sections of the type initially specified (i.e., channel, angle, etc.) and, if a suitable replacement is found, presents design results for that section. If no section satisfying the depth restrictions or lighter than the initial one can be found, the program leaves the member unchanged, regardless of whether it passes the code check or not. The program calculates effective section properties in accordance with Clause 5.2.1.1. Cross-sectional properties and overall slenderness of members are checked for compliance with

Section 9D



Clause 6.6.3, Maximum Effective Slenderness Ratio for members in Compression



Clause 5.2.3, Maximum Flat Width Ratios for Elements in Compression



Clause 5.2.4, Maximum Section Depths.

The program will check member strength in accordance with Clause 6 of the Standard as follows: Members in tension Resistance is calculated in accordance with Clauses 6.1 Members in bending and shear Resistance calculations are based on Clauses: a)

6.4.1 Shear stress in webs,

b)

6.4.2 Bending stress in webs

c)

6.4.3 Combined Bending and Shear in Webs.

Members in compression Resistance calculations are based on Clauses: a)

6.2 Compression on flat unstiffened element,

b)

6.6.1.1 Shapes not subject to torsional -flexural buckling,

c)

6.6.1.2 Singly-symmetric sections and nonsymmetrical shapes of open cross section or intermittently fastened singly-symmetrical components of built-up shapes having Q = 1.0 which may be subject to torsional-flexural buckling,

9-95


9-96

Section 9D

d)

6.6.1.3 Singly-symmetric sections and nonsymmetrical shapes or intermittently fastened singly-symmetrical components of built-up shapes having Q < 1.0 which may be subject to torsional-flexural buckling,

e)

6.8 Cylindrical Tubular Sections.

Members in compression and bending Resistance calculations are based on Clauses: a)

All clauses for members in compression &

b)

6.3 Laterally Unsupported Members,

c)

6.7.1 Doubly-symmetric shapes or Shapes not subjected to torsional or torsional-flexural buckling

d)

6.7.2. Singly-symmetric shapes or Intermittently fastened singly-symmetric components of built-up shapes having Q=1.0 which may be subjected to torsional-flexural buckling

e)

6.7.3. Singly-symmetric shapes or Intermittently fastened singly-symmetric components of built-up shapes having Q<1.0 which may be subjected to torsional-flexural buckling.

Input for the coefficients of uniform bending must be provided by the user.

Section 9D

9-97

The following table contains the input parameters for specifying values of design variables and selection of design options. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. COLD FORMED STEEL DESIGN PARAMETERS Parameter Name BEAM

Default Value 1.0

Description When this parameter is set to 1.0 (default), the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details. For TRUSS members only start and end locations are designed.

CMZ

1.0

Coefficient of equivalent uniform bending z. See IS:8011975, 6.7. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CMY

0.85

Coefficient of equivalent uniform bending y. See IS:8011975, 6.7. Used for Combined axial load and bending design. Values range from 0.4 to 1.0.

CWY

0.85

Specifies whether the cold work of forming strengthening effect should be included in resistance computation. See IS:801-1975, 6.1.1 Values: 0 – effect should not be included 1 – effect should be included

FLX

1

Specifies whether torsional-flexural buckling restraint is provided or is not necessary for the member. See IS:8011975, 6.6.1 Values: 0 – Section not subject to torsional flexural buckling 1 – Section subject to torsional flexural buckling


9-98

Section 9D

COLD FORMED STEEL DESIGN PARAMETERS Parameter Name

Default Value

FU

450 MPa (4588.72 kg/cm2)


FYLD

Yield strength of steel in current units.

KX

353.04 MPa (3600.0 kg/cm2) 1.0

KY

1.0

Effective length factor for overall buckling about the local Yaxis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

KZ

1.0

Effective length factor for overall buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

LX

Member length

Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

LY

Member length

Effective length for overall buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

Description

Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the capacity in axial compression.

Section 9D

9-99

COLD FORMED STEEL DESIGN PARAMETERS Parameter Name

Default Value

Description

LZ

Member length

Effective length for overall buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a member completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the capacity in axial compression.

MAIN

0

0 – Check slenderness ratio 0 – Do not check slenderness ratio

NSF

1.0

DMAX

2540.0 cm.

RATIO

1.0

TRACK

0

Net section factor for tension members Maximum allowable depth. It is input in the current units of length. Permissible ratio of actual to allowable stresses This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 0 - Prints only the member number, section name, ratio, and PASS/FAIL status. 1 - Prints the design summary in addition to that printed by TRACK 1 2 - Prints member and material properties in addition to that printed by TRACK 2.

TSA

1

Specifies whether webs of flexural members are adequately stiffened to satisfy the requirements of IS:801-1975, 5.2.4. Values: 0 – Do not comply with 5.2.4 1 – Comply with 5.2.4


9-100

Section 9D

Section 10

Japanese Codes

;alksdf;lkajf

10-1

Concrete Design Per AIJ

Section

10A

10A.1 Design Operations STAAD has the capabilities of performing concrete design based on the AIJ standard for structural calculation of Reinforced Concrete Structures (1985 edition). Design for a member involves calculation of the amount of reinforcement required for the member. Calculations are based on the user specified properties and the member forces obtained from the analysis. In addition, the details regarding placement of the reinforcement on the cross section are also reported in the output.

10A.2 Section Types for Concrete Design The following types of cross sections for concrete members can be designed. For Beams Prismatic (Rectangular & Square) For Columns Prismatic (Rectangular, Square and Circular)



10-2

Section 10A

UNIT MM MEMBER PROPERTY 1 3 TO 7 9 PRISM YD 450. ZD 250. 11 13 PR YD 350. In the above input, the first set of members are rectangular (450 mm depth and 250mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 350mm diameter. It is absolutely imperative that the user not provide the cross section area (AX) as an input.

10A.4 Slenderness Effects and Analysis Consideration Slenderness effects are extremely important in designing compression members. Slenderness effects result in additional forces being exerted on the column over and above thos e obtained from the elastic analysis. There are two options by which the slenderness effects can be accommodated. The first option is to compute the secondary moments through an exact analysis. Secondary moments are caused by the interaction of the axial loads and the relative end displacements of a member. The axial loads and joint displacements are first determined from an elastic stiffness analysis and the secondary moments are then evaluated. The second option is to approximately magnify the moments from the elastic analysis and design the column for the magnified moment. It is assumed that the magnified moment is equivalent to the total moment comprised of the sum of primary and secondary moments. STAAD provides facilities to design according to bot h of the above methods. To utilize the first method, the command PDELTA ANALYSIS must be used instead of PERFORM ANALYSIS in the

Section 10A

input file. The user must note that to take advantage of this analysis, all the combinations of loading must be provided as primary load cases and not as load combinations. This is due to the fact that load combinations are just algebraic combinations of forces and moments, whereas a primary load case is revised during the P-delta analysis based on the deflections. Also, note that the proper factored loads (like 1.5 for dead load etc.) should be provided by the user. STAAD does not factor the loads automatically. The second method mentioned above is utilized by providing the magnification factor as a concrete design parameter (See the parameter MMAG in Table 9A.1). The column is designed for the axial load and total of primary and secondary biaxial moments if the first method is used and for the axial load and magnified biaxial moments if the second method is used.

10A.5 Beam Design Beams are designed for flexure, shear and torsion. Program considers 12 equally spaced sections of the beam member. However this number can be redefined by NSECTION parameter. All these sections are designed for flexure, shear and torsion for all the load cases and print out the design results for most critical load case. Design for Flexure Reinforcement for positive and negative moments are calculated on the basis of section properties provided by the user. Program first try to design the section for =0 and pt = balanced reinforcement ratio. If allowable moment is lower than the actual moment program increases  value for same pt and checks the satisfactory conditions. If conditions are not satisfied this procedure continues until  reaches to 1.0 and then pt value is increased keeping  = 1.0. This procedure continues until pt reaches to its maximum value( 2 % ). But if the allowable moment for pt = maximum value and  = 1.0 is lower than the actual moment the program gives message that the section fa ils. This program automatically calculates the Bar size and no. of bars needed to design the section. It arranges the bar in layers as per

10-3


10-4

Section 10A

the requirements and recalculate the effective depth and redesign the sections for this effective depth. Notes: 

Beams are designed for MZ only. The moment MY is not considered in flexure design



MMAG parameter can be used to increase design moment



1.4 cm. is added to the clear cover to take stirrup size into consideration for flexure design.



STAAD beam design procedure is based on the local practice and considering the fact that Japan is a high seismic zone area.

Design for Shear Shear design of beam is done for Qy value. The update effective depth is used for allowable shear stress calculation. Allowable shear stress of concrete is automatically calculated from design load type (permanent or temporary) and given density of concrete. Program calculates required Bar size and spacing of stirrups. Pw is calculated for design Bar size and spacing and all the necessary checking is done. For seismic load it is needed to increase shear force 1.5 times the actual value and this can be done utilizing SMAG parameter. Notes: 

SMAG parameter can be used if its needed to increase the Design Shear Force without changing Design Moment.



Stirrups are always assumed to be 2-legged



Governing density to determine Light weight or Normal Weight Concrete is 2.3 kg/sq. cm

Section 10A

Example of Input Data for Beam Design UNIT KG CM START CONCRETE DESIGN CODE JAPAN FYMAIN SRR295 ALL FYSEC SRR295 ALL FC 350 ALL CLEAR 2.5 MEM 2 TO 6 TRACK 1.0 MEMB 2 TO 9 DESIGN BEAM 2 TO 9 END CONCRETE DESIGN Design for Torsion Torsion design for beam is optional. If TORSION parameter value is 1.0, program design that beam for torsion. Program first checks whether extra reinforcement is needed for torsion or not. If additional reinforcement is needed, this additional pt is added to flexure pt and additional Pw is added to shear design Pw.

10A.6 Column Design Columns are designed for axial force, MZ moment, MY moment and shear force. Both the ends of the members are designed for all the load cases and the loading which produces largest amount of reinforcement is called as critical load. If Track 0 or Track 1 is used, design results will be printed for critical load on ly. But if Track 2 is used user can get details design results of that member. Pt needed for minimum axial force, maximum axial force, maximum MZ, maximum MY among all the load cases for both the ends will be printed. If MMAG parameter is used, the column moments will be multiplied by that value. If SMAG parameter is used, column shear force will be multiplied by that value. Column design is done for Rectangular, Square and Circular sections. For rectangular and square sections Pt value is calculated

10-5


10-6

Section 10A

separately for MZ and MY, while for circular sections Pg value is calculated for MZ and MY separately. Column design for biaxial moments is optional. If BIAXIAL parameter value 1.0, program will design the column for biaxial moments. Otherwise column design is always uniaxial type. Steps involved : 1) Depending on the axial force zone is determined for Pt = 0.0 . 2) If the column is in "zone A", design is performed by increasing Pt and checking allowable load for that known Pt and known actual eccentricity of the column. 3) If the column is in "zone B" or in "zone C", xn is calculated for given P and Pt and checking is done for allowable moment, if allowable moment is less than the actual moment, program increases Pt and this procedure continues until the column design conditions are satisfied or the column fails as the required Pt is higher than Pt maximum value. 4) If the column is in tension, design is done by considering allowable tensile stress of steel only. 5) If biaxial design is requested program solve the following interaction equation 



 My   Mz        1.0 Mycap    Mzcap 

where,  = 1.0+1.66666666  (ratio-0.2), ratio = P/Pcap & 1.0    2.0, Mycap, Mzcap & Pcap represents section capacity 6) If the interaction equation is not satisfied program increases Pt and calculates Pcap, Mycap and Mzcap and solve the interaction equation again and this process continues until the

Section 10A

eqn. is satisfied or the column fails as Pt exceeds its maximum limit. 7) If biaxial design is not requested program assumes that interaction equation is satisfied ( if uniaxial design is performed successfully ). 8) If the interaction equation is satisfied program determines bar size and calculates no. of bars and details output is written.

Example of Input Data for Column Design UNIT KGS CMS START CONCRETE DESIGN CODE JAPAN FYMAIN SRR295 ALL FC 210 ALL CLEAR 2.5 MEMB 2 TO 6 DESIGN COLUMN 2 TO 6 END CONCRETE DESIGN

10A.7 Slab/Wall Design To design a slab or a wall, it must first be modelled using finite elements and analysed. The command specifications are in accordance with Chapter 2 and Chapter 6 of the Technical Reference Manual. Elements are designed for the moments Mx and My. These moments are obtained from the element force output (see Chapter 2 of the Technical Reference Manual). The reinforcement required to resist the Mx moment is denoted as longitudinal reinforcement and the reinforcement required to resist the My moment is denoted as transverse reinforcement.

10-7


10-8

Section 10A

The longitudinal bar is the layer closest to the exterior face of the slab or wall. The following parameters are those applicable to slab and wall design: 1. FYMAIN 2. FC 3. CLEAR

4. MINMAIN

Yield stress for reinforcing steel - transverse and longitudinal. Concrete grade Distance from the outer surface of the element to the edge of the bar. This is considered the same on both top and bottom surfaces of the element. Minimum required size of longitudinal/transverse reinforcing bar

The other parameters shown in Table 9A.1 are not applicable to slab or wall design. Z Y My

X Mx TRANS. My

Mx LONG.

10A.8 Design Parameters The program contains a number of parameters which are needed to perform the design. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 9A.1 contains a complete list of the available parameters and their default values. It is necessary to declare length and force units as centimeters and Kilograms before performing the concrete design. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

Section 10A

10-9

Table 10A.1 Japanese Concrete Design Parameters Parameter Name

Default Value

Description

FYMAIN

SR235

Steel grade. Acceptable values for steel grade and their associated yield stress values are shown in the next table. Program automatically calculates yield stress value depending on design load type (permanent or temporary).

FYSEC

SR235

Same as FYMAIN except this is for secondary steel.

FC

210 Kg/cm2

CL

3.0 cm

Clear cover for Beam.

CLS

4.0 cm

Clear side cover for Column.

MINMAIN

10 mm


MINSEC

10 mm


MAXMAIN

41.0 cm

Maximum main reinforcement bar size

MAXSEC

41.0 cm


Compressive Strength of Concrete.

SFACE

0.0

Face of support location at start of beam.

EFACE

0.0

Face of support location at end of beam. (Note: Both SFACE & EFACE are input as positive numbers).

REINF

0.0

Tied Column. A value of 1.0 will mean spiral.

MMAG

1.0

Design moment magnification factor

SMAG

1.0

Design shear magnification factor

LONG

0.0

Value to define design load type 0 = Permanent Loading 1 = Temporary Loading

BIAXIAL

0.0

Value to define biaxial or uniaxial design type for Column 0 = uniaxial design only 1 = design for biaxial moments

TORSION

0.0

Value to request for torsion design for beam 0 = torsion design not needed 1 = torsion design needed


10-10

Section 10A

Table 10A.1 Japanese Concrete Design Parameters Parameter Name

Default Value

Description

WIDTH

ZD

Width of concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES.

DEPTH

YD

Depth of concrete member. This value defaults to YD as provided under MEMBER PROPERTIES.

NSECTION

12


TRACK

0.0

BEAM DESIGN: 0.0 = Critical section design results. 1.0 = Five section design results & design forces. 2.0 = 12 section design results & design forces. COLUMN DESIGN: 1.0 = Detail design results for critical load case only. 2.0 = Design results for minimum P, maximum P, maximum MZ and maximum MY among all load cases for both ends.

Table of permissible Steel Grades and associated Yield Stresses for FYMAIN and FYSEC parameters. (Default values in Kg/Cm^2) Steel Grade SR235 SRR235 SDR235 SR295 SRR295 SD295A SD295B SDR295 SDR345 SD345 SD390

Design Load Type Long Term

Design Load Type Short Term

22.76

34.14

22.76

42.67

28.45

42.67

31.29

49.78

31.29

56.89

10-11

Steel Design Per AIJ

Section

10B

10B.1 General This section presents some general statements regarding the implementation of the “Architectural Institute of Japan” (AIJ) specifications for structural steel design (1986 edition) in STAAD. The design philosophy and procedural logistics are based on the principles of elastic analysis and allowable stress design. Facilities are available for member selection as well as code checking. Two major failure modes are recognized: failure by overstressing an d failure by stability considerations. The following sections describe the salient features of the design approach. Members are proportioned to resist the design loads without exceedance of the allowable stresses or capacities and the most economical section is selected on the basis of the least weight criteria. The code checking part of the program also checks the slenderness requirements and the stability criteria. Users are recommended to adopt the following steps in performing the steel design:   

Specify the geometry and loads and perform the analysis. Specify the design parameter values if different from the default values. Specify whether to perform code checking or member selection.


10-12

Section 10B

10B.2 Analysis Methodology Elastic analysis method is used to obtain the forces and moments for design. Analysis is done for the primary and combination loading conditions provided by the user. The user is allowed complete flexibility in providing loading specifications and in using appropriate load factors to create necessary loading situations. Depending upon the analysis requirements, regular stiffness analysis or P-Delta analysis may be specified. Dynamic analysis may also be performed and the results combined with static analysis results.

10B.3 Member Property Specifications For specification of member properties of standard Japanese steel shapes, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built-in steel table. Members properties may also be specified using the User Table facility. For more information on these facilities, refer to the STAAD Technical Reference Manual.

10B.4 Built-in Japanese Steel Section Library The following information is provided for use when the built-in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, these properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered for these members during the analysis. An example of member property specification in an input file is provided at the end of this section.

Section 10B

A complete listing of the sections available in the built -in steel section library may be obtained using the tools of the graphical user interface. Following are the descriptions of different types of sections. I shapes I shapes are specified in the following way: I 250 X 125 X 10 Section-type (I)

Web thickness (mm)

Nominal height (mm)

Nominal width of flange (mm)

Note : While specifying the web thickness, the portion after the decimal point should be excluded.

Example:

1 TO 9 TA ST I300X150X11 12 TO 15 TA ST I350X150X9

H shapes H shapes are specified as follows: H 600 X 200 X 11 Section-type (H)

Web thickness (mm)

Nominal height (mm)

Nominal width of flange (mm)

Note: While specifying the web thickness, the portion after the decimal point should be excluded.

Example:

1 TO 8 TA ST H200X100X4 13 TO 17 TA ST H350X350X12

10-13


10-14

Section 10B

T shapes T shapes are specified as follows: T 250 X 16 Section-type (T) Nominal width of flange (mm)

Flange thickness (mm)

Note : While specifying the web thickness, the portion after the decimal point should be excluded

Example:

20 TO 25 TA ST T250X19

Channels Channel sections are specified as follows. C 300 X 90 X 10 Section-type (C) Nominal height (mm)

Example:

Web thickness (mm) Nominal width of flange (mm)

25 TO 34 TA ST C125X65X6 46 TO 49 TA ST C200X90X8

Double Channels Back to back double channels, with or without a spacing in between them, are available. The letter D in front of the section name is used to specify a double channel.

17 TO 27 TA D C300X90X10 45 TO 76 TA D C250X90X11 SP 2.0 In the above commands, members 17 to 27 are a back to back double channel C300X90X10 with no spacing in between.

Section 10B

Members 45 to 76 are a double channel C250X90X11 with a spacing of 2 length units. Angles Two types of specification may be used to describe an angle. The standard angle specification is as follows. L 125 X 90 X 10 Section-type (L) Length of longer side (mm)

Thickness (mm) Length of shorter side (mm)

The letter L (signifying that the section is an angle) is follo wed by the length of the legs and then the thickness of the leg, all in millimetres. The word ST signifies that the section is a STandard angle meaning that the major principal axis coincides with the local YY axis specified in Chapter 1 of Section 1.5.2 o f the User's Manual.

Example: 1 4 TA ST L150X90X9 If the minor principal axis coincides with the local YY axis specified in Chapter 2 of the User's Manual, the word RA (Reverse Angle) should be used instead of ST as shown below.

7 TO 23 TA RA L90X75X9 Double angles Short leg back to back and long leg back to back double angles may be specified by using the words SD or LD in front of the angle size. In the case of an equal angle, either SD or LD will serve the purpose. The spacing between the angles may be specified by using the word SP after the angle size followed by the value of the spacing.

10-15


10-16

Section 10B

8 TO 25 TA SD L100X65X7 SP 2.0 36 TO 45 TA LD L300X90X11 SP 3.0 The first example indicates a short legs back to back double angle comprised of 100X65X7 angles separated by 2 length units. The latter is a long legs back to back double angle comprised of 300X90X11 angles separated by 3 length units. Tubes Tube names are input by their dimensions. For example,

6 TA ST TUBE DT 8.0 WT 6.0 TH 0.5 is a tube that has a height of 8 length units, width of 6 length units and a wall thickness of 0.5 length units. Only code checking, no member selection can be performed on TUBE sections. Pipes (Circular Hollow sections) Circular hollow sections may be provided by specifying the word PIPE followed by the outside and inside diameters of the section. For example,

1 TO 9 TA ST PIPE OD 25.0 ID 20.0 specifies a pipe with outside diameter of 25 length units and an inside diameter of 20 length units. Only code checking, no membe r selection, can be performed on PIPE sections.

Section 10B

Sample Input file containing Japanese shapes STAAD SPACE UNIT KIP FEET JOINT COORD 1 0 0 0 12 11 0 0 MEMB INCIDENCE 1 1 2 11 UNIT INCH MEMBER PROPERTY JAPANESE * H-SHAPE 1 TA ST H200X100X4 * I SHAPE 2 TA ST I250X125X10 * T SHAPE 3 TA ST T200X19 * CHANNEL 4 TA ST C125X65X6 * DOUBLE CHANNEL 5 TA D C200X90X8 * REGULAR ANGLE 6 TA ST L100X75X7 * REVERSE ANGLE 7 TA RA L90X75X9 * DOUBLE ANGLE - LONG LEG BACK TO BACK 8 TA LD L125X75X7 SP 2.0 * DOUBLE ANGLE - SHORT LEG BACK TO BACK 9 TA SD L300X90X11 SP 1.5 * TUBE 10 TA ST TUBE DT 3.0 WT 2.5 TH 0.25 * PIPE 11 TA ST PIPE OD 3.0 ID 2.5 PRINT MEMBER PROPERTIES FINISH

10-17


10-18

Section 10B

10B.5 Member Capacities As mentioned before, member design and code checking in STAAD are based upon the allowable stress design method. It is a method for proportioning structural members using design loads and forces, allowable stresses, and design limitations for the appropriate material under service conditions. The basic measure of member capacities are the allowable stresses on the member under various conditions of applied loading such as allowable tensile stress, allowable compressive stress etc. These depend on several factors such as cross sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Explained here is the procedure adopted in STAAD for calculating such capacities. Design Capabilities All types of available shapes like H-Shape, I-Shape, L-Shapes, CHANNEL, PIPE, TUBE, Prismatic section etc. can be used as member property and STAAD will automatically adopt the design procedure for that particular shape if Steel Design is requested. STEEL TABLE available within STAAD or UPTABLE facility can be used for member property. Methodology For steel design, STAAD compares the actual stresses with the allowable stresses as required by AIJ specifications. The design procedure consist of following three steps. 1) Calculation of sectional properties Program extract sectional properties like sectional area ( A ), Moment of Inertia about Y axis and Z axis ( Iyy, Izz) from inbuilt Japanese Steel Table and calculates Zz, Zy, iy, iz using appropriate formula. For calculation of i ( radius of gyration needed for bending ), program calculates moment of inertia ( Ii )and sectional area ( Ai ) for 1/6th section and then uses following formula:

Section 10B

i

Ii Ai

Please note, that the above mentioned procedure for calculation of i is applicable for I shape, H shape and Channel sections. 2) Calculation of actual and allowable stresses Program calculates actual and allowable stresses by following methods: i)

Axial Stress: Actual tensile stresses ( FT ) = Force / ( A  NSF ), NSF = Net Section Factor for tension Actual compressive stress ( FC ) = Force / A Allowable tensile stress ( ft ) = F / 1.5 (For Permanent Case) = F ( For Temporary Case ) Allowable compressive stress (fc )  1  .4x  / 2 x F /  when   











 2.77 x F /  / 2 when   

= fc  1.5 (For Temporary Case ) where,   2 E /(.6xF)  =F) ,  =3 / 2 + 2 / 3  ( / ) 2 ii) Bending Stress: Actual bending stress for My for compression ( Fbcy) = My / Zcy Actual bending stress for Mz for compression ( Fbcz) = Mz / Zcz Actual bending stress for My for tension ( Fbty ) = My / Zcy Or ( Fbty ) = My / Zty Actual bending stress for Mz for tension ( Fbtz ) = Mz / Zcz Or (Fbtz ) = Mz / Ztz

10-19


10-20

Section 10B

where, Zcy , Zcz are section modulus for compression and Zty, Ztz are section modulus for tension Allowable bending stress for My (fbcy) = ft Allowable bending stress for Mz (fbcz) = { 1-.4  (lb / i ) 2 / (C  2 )}ft max = 900/ ( lb  h / Af ) For Temporary case, fbcz = 1.5  (fbcz for Permanent Case) where, C = 1.75 -1.05(M2/M1)+0.3(M2/M1) 2 Allowable bending stress for My ( fbty) = ft Allowable bending stress for Mz ( fbtz) = fbcz iii) Shear Stress Actual shear stresses are calculated by following formula : qy = Qy / Aww, Where, Aww = web shear area = product of depth and web thickness qz = Qz / Aff , Where, Aff = flange shear area = 2/3 times total flange areas Allowable shear stress ( fs ) = Fs / 1.5 , Fs = F /

3

3) Checking design requirements: User provided RATIO value (default 1.0) is used for checking design requirements The following conditions are checked to meet the AIJ specifications. For all the conditions calculated value should not be more than the value of RATIO. If for any condition value exceeds RATIO , program gives the message that the section fails. Conditions: i) Axial tensile stress ratio = FT / ft ii) Axial compressive stress ratio = FC / fc iii) Combined compression & bending ratio = FC/fc+Fbcz/fbcz+Fbcy/fbcy

Section 10B

iv)

Combined compression & bending ratio = (Fbtz+Fbty-FC) / ft v) Combined tension & bending ratio = (FT+Fbtz+Fbty) / ft vi) Combined tension & bending ratio = Fbcz/fbcz+Fbcy/fbcyFT/ft vii) Shear stress ratio for qy = qy / fs viii) Shear stress ratio for qz = qz / fs New Output Format ( TRACK -- 3 ) One new output format has been introduced which provides details step by step information of Steel Design for guiding load case only. If Section command is used before Parameter command this output will provide details information for all the sections specified by Section Command. Please note, that this output format is available only when Beam parameter value is 0 and Track parameter value is 3. If section command is not used design information will be printed for two ends only. If Member Truss option is used no Shear Design information will be printed.

Example: SECTION 0.0 0.25 0.5 0.75 1.0 ALL PARAMETER CODE JAPAN BEAM 0.0 ALL TMP 0.0 MEMB 1 to 4 TMP 1.0 MEMB 5 to 8 TRACK 3 ALL CHECK CODE ALL FINISH Allowable stress for Axial Tension Allowable axial stress in tension is calculated per section 5.1 (1) of the AIJ code. In members with axial tension, the tensile load must not exceed the tension capacity of the member. The tension

10-21


10-22

Section 10B

capacity of the member is calculated on the basis of the member area. STAAD calculates the tension capacity of a given member based on a user supplied net section factor (NSF-a default value of 1.0 is present but may be altered by changing the input value, see Table 8B.1) and proceeds with member selection or code checking. Allowable stress for Axial Compression The allowable stress for members in compression is determined according to the procedure of section 5.1 (3). Compressive resistance is a function of the slenderness of the cross -section (Kl/r ratio) and the user may control the slenderness value by modifying parameters such as KY, LY, KZ and LZ. In the absence of user provided values for effective length, the actual member length will be used. The slenderness ratios are checked against the permissible values specified in Chapter 11 of the AIJ code. Allowable stress for Bending The permissible bending compressive and tensile stresses are dependent on such factors as length of outstanding legs, thickness of flanges, unsupported length of the compression flange (UNL, defaults to member length) etc. The allowable stresses in bending (compressive and tensile) are calculated as per the criteria of Clause 5.1 (4) of the code. Allowable stress for Shear Shear capacities are a function of web depth, web thickness etc. The allowable stresses in shear are computed according to Clause 5.1 (2) of the code.

10B.6 Combined Loading For members experiencing combined loading (axial force, bending and shear), applicable interaction formulas are checked at different locations of the member for all modelled loading situations. Members subjected to axial tension and bending are checked using the criteria of clause 6.2. For members with axial compression and bending, the criteria of clause 6.1 is used.

Section 10B

10-23

10B.7 Design Parameters The user is allowed complete control over the design process through the use of parameters mentioned in Table 9B.1 of this chapter. These parameter s communicate design decisions from the engineer to the program. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements of the situation, some or all of these parameter values may have to be changed to exactly model the physical structure. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 10B.1 - Japanese Steel Design Parameters Parameter Name

Default Value

Description

KY

1.0

K value in local y-axis. Usually, this is the minor axis.

KZ

1.0

K value in local z-axis. Usually, this is the major axis.

LY

Member Length


LZ

Member Length

Same as above except in z-axis

FYLD

235 MPA

Yield strength of steel in Megapascal.

NSF

1.0

UNL

Member Length

UNF

1.0

Same as above provided as a fraction of actual member length.

SSY

0.0


Net section factor for tension members. Unsupported length for calculating allowable bending stress.


10-24

Section 10B

Table 10B.1 - Japanese Steel Design Parameters Parameter Name

Default Value

Description

SSZ

0.0


MAIN

0.0

0.0 = check for slenderness 1.0 = suppress slenderness check

TRACK

0.0

0.0 = Suppress critical member stresses 1.0 = Print all critical member stresses 2.0 = Print expanded output

DMAX

100 cm

Maximum allowable depth for member.

DMIN

0.0 cm

Minimum allowable depth for member.

TMP

0 (Permanent Load)

0 = Permanent Loading 1 = Temporary Loading

RATIO

1.0


BEAM

0.0

0.0 = design only for end moments or those at locations specified by the SECTION command. 1.0 = calculate moments at twelfth points along the beam, and use the maximum Mz location for design.

DFF


DJ1



DJ2

End Joint of member



NOTE: 1) "Deflection Length" is defined as the length that is used for calculation of local deflections within a member. It may be noted that for most cases the "Deflection Length" will be equal to the length of the member. However, in some situations, the "Deflection Length" may be different. For example, refer to the figure below where a beam has been modeled using four joints and three members. Note that the "Deflection Length"

Section 10B

for all three members will be equal to the total length of the beam in this case. The parameters DJ1 and DJ2 should be used to model this situation. Also the straight line joining DJ1 and DJ2 is used as the reference line from which local deflections are measured. Thus, for all three members here, DJ1 should be "1" and DJ2 should be "4". 1

2 1

3 2

EXAMPLE :

4 3 D

D = Maximum local deflection for members 1, 2 and 3.


2) If DJ1 and DJ2 are not used, "Deflection Length" wil l default to the member length and local deflections will be measured from original member line. 3) The above parameters may be used in conjunction with other available parameters for steel design.

10B.8 Code Checking The purpose of code checking is to check whether the provided section properties of the members are adequate to carry the forces transmitted to it by the loads on the structure. The adequacy is checked per the AIJ requirements. Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1, moments are calculated at every twelfth point along the beam, and the maximum moment about the major axis is used. When no sections are specified and the BEAM parameter is set to zero (default), design will be based on the forces at the start and end joints of the member. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (distance from start joint) and magnitudes of the governing forces and moments are also printed.

10-25


10-26

Section 10B

10B.9 Member Selection The member selection process basically involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments obtained from the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally pr ovided from a user table will be limited to sections in the user table. Member selection cannot be performed on TUBES, PIPES or members listed as PRISMATIC.

Sample Input data for Steel Design UNIT METER PARAMETER CODE JAPAN NSF 0.85 ALL UNL 10.0 MEMBER 7 KY 1.2 MEMBER 3 4 RATIO 0.9 ALL TRACK 1.0 ALL CHECK CODE ALL SELECT ALL

Section 11

Mexican Codes

11-1

Concrete Design Per MEX NTC 1987 Section

11A

11A.1 Design Operations STAAD has the capabilities for per forming concrete design. It will calculate the reinforcement needed for the specified concrete section. All the concrete design calculations are based on the current: Complementary Technical Standards for the Design and Construction of Concrete Structures – Nov. 1987. (Normas Técnicas Complementarias para Diseño y construcción de Estructuras de Concreto) of the Mexican Construction Code for the Federal District –Aug. 1993 (Reglamento de Construcciones para el Distrito Federal).

11A.2 Section Types for Concrete Design The following types of cross sections can be defined for concrete design. For Columns For Beams For Slabs

Prismatic (Rectangular, Square and Circular) Prismatic (Rectangular & Square), Trapezoidal and T-shapes Finite element with a specified thickness

Concrete Design Per Mexican Code

11-2

Section 11A

11A.3 Member Dimensions Concrete members which will be designed by the program must have certain section properties input under the MEMBER PROPERTY command. The following example shows the required input: UNIT CM MEMBER PROPERTY 13 TO 79 PRISM YD 40. ZD 20. IZ 53333 IY 13333 11 13 PR YD 20. 14 TO 16 PRIS YD 24. ZD 48. YB 18. ZB 12. 17 TO 19 PR YD 24. ZD 18. ZB 12.

In the above input, the first set of members are rectangular (40 cm depth and 20 cm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 20 cm diameter. Note that no area (AX) is provided for these members. For concrete design, this property must not be provided. If shear areas and moments of inertias are not provided, the program calculates these values from YD and ZD. Notice that in the above example the IZ and IY values provided are actually 50% of the values calculated using YD and ZD. This is a conventional practice which takes int o consideration revised section parameters due to cracking of section.

Section 11A

Note that the third and the fourth set of members in the above example represent a T-shape and a TRAPEZOIDAL shape respectively. Depending on the properties (YD, ZD, YB, ZB, etc.) provided, the program will determine whether the section is rectangular, trapezoidal or T-shaped and the BEAM design will be done accordingly.

11A.4 Design Parameters The program contains a number of parameters which are needed to perform design by the Mexican code. Default parameter values have been selected such that they are frequently used numbers for conventional design requirements. These values may be changed to suit the particular design being performed. Table 3.1 is a complete list of the available parameters and their default values. The manual describes the commands required to provide these parameters in the input file. For example, the values of SFACE and EFACE (parameters that are used in shear design), the distances of the face of supports from the end nodes of a beam, are assigned values of zero by default but may be changed depending on the actual situation. Similarly, beams and columns are designed for moments directly obtained from the analyses without any magnification. The factors MMAGx and MMAGy may be used for magnification of column moments. For beams, the user may generate load cases which contain loads magnified by the appropriate load factors. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

11-3


11-4

Section 11A

Table 11A.1 – Mexican Concrete Design Parameters Parameter Name

Default

Description

Value

FYMAIN

4200Kg/cm2

Yield Stress for main reinforcing steel

FYSTIRR

4200Kg/cm2

Yield Stress for stirrup reinforcing steel

FC

200Kg/cm2

Compressive Strength of Concrete

clear_cover_top

3cm

Clear cover for top reinforcement

clear_cover_bottom

3cm

Clear cover for bottom reinforcement

clear_cover_side

3cm

Clear cover for side reinforcement

MINMAIN**

No 2.5 bar

Minimum main reinforcement bar size (Number 2 -18)

MINSEC**

No 2.5 bar

Minimum secondary reinforcement bar size (Number 2 -18)

MAXMAIN**

No 12 bar

Maximum main reinforcement bar size (Number 2 18)

0

Face to support location of start of beam. If specified, for shear force at start is computed at a distance of SFACE+d from the start joint of the member. Positive number

EFACE

0

Face to support location of end of beam. If specified, for shear force at start is computed at a distance of EFACE+d from the start joint of the member. Positive number.

REINF

0

Tied Column. A value of 1 will mean spiral.

AMAGx AMAGy

1

A factor by which the column design moments will be magnified

WIDTH

*ZD

Width of concrete member. This value defaults to ZD as provided under MEMBER PROPERTIES

DEPTH

*YD

Depth of concrete member. This value defaults to YD as provided under MEMBER PROPERTIES

12

Number of equally-spaced sections to be considered in finding critical moments for beam design

SFACE

NSECTION

Section 11A

11-5

Table 11A.1 – Mexican Concrete Design Parameters Parameter

Default

Name

Description

Value Beam Design 0 = Critical Moment will not be printed out with beam design report. 1 = will mean a print out. 2 = will print out required steel areas for all intermediate sections specified by NSECTION.

TRACK

0 Column Design 0 = will print out detailed design results. 1 = will mean a print out column interation analysis results in addition to TRACK 0 output. 2 = will print out a schematic interaction diagram and intermediate interaction values in addition to all of the above.

BARTYPE

2

0: IMPERIAL (No 3 1: METRIC (4.2 2: MEXICAN (No 2 to 18)

to to

18) 60mm)

DIM_PRECAUTION

TRUE

TRUE: Precautions are taken to assure dimensions FALSE: Not precautions taken - Section reduction to section 1.5 NTC Concrete

EXPOSED_SOIL_ WEATHER

FALSE

Exposition to soil or weather to define cover and min Steel reinforcement

CONC_CLAS

1

Concrete class according to 1.4.1d) to define Modulus of Elasticity

LIGHT_CONC

FALSE

Light Concrete to define development multipliers according to table 3.1 NTC

COLD_FORM_BAR

FALSE

Cold formed Bar to define development multipliers according to table 3.1 NTC

DUCTILE_SEISMIC _DESIGN

TRUE

DUCTILE FRAMES ACCORDING TO SECTION 5. Some design conditions are considered (not including, for the time being, geometric or confinment ones)

DIAM_AG

*2 cm

MAXIMUM DIAM AGGREGATE

BEARED_PERIM

TRUE

Slab beared perimeter. To calculate min steel required according to 2.1.2


11-6

Section 11A

Table 11A.1 – Mexican Concrete Design Parameters Parameter

Default

Name

Description

Value

DIRECT_COMP

TRUE

Beam Loads and reactions in direct compression Cl-2.1.5.a.I 2nd paragraph

PHI

90 degrees

Stirrups angle with the axis of the element

TORSIONAL_ EQUILIBRIUM

FALSE

Beam needed for torsional equilibrium Cl.2.1.6a) 2nd paragraph

Pfact

1.0

Part of the longitudinal steel considered to reduce shear. 0(zero) is on the safe side. Value between 1 and 0.

ZB

0.0

IDEM ACI

YB

0.0

IDEM ACI

EIT

*198000 CONCRETE MODULUS OF ELASTICITY Kg/cm2 * These values must be provided in the current unit system being used. ** When using metric bars for design, provide values for these parameters in actual „mm„ units instead of the bar number. The following metric bar sizes are available: 4.2mm, 6 mm, 8 mm, 10 mm, 12 mm, 16 mm, 20 mm, 25 mm, 32 mm, 40 mm, 50 mm and 60 mm.

11A.5 Beam Design Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are prescanned to locate the possible critical sections. The total number of sections considered is 12 (twelve) unless this number is redefined with an NSECTION parameter. All of these equally spaced sections are scanned to determine moment and shear envelopes. Design for Flexure Reinforcement for positive and negative moments are calculated on the basis of the section properties provided by the user. If the section dimensions are inadequate to carry the applied load, that is if the required reinforcement is greater than the maximum allowable for the cross section, the program reports that beam fails in maximum reinforcement. Rectangular sections are also designed with compression reinforcement.

Section 11A

Effective depth is chosen as Total depth - (Clear cover + diameter of stirrup + half the dia. of main reinforcement), and a tr ial value is obtained by adopting proper bar sizes for the stirrups and main reinforcements. The relevant clauses in Sections 1.5, 1.6, 2.1.1 -25, 3.10 and 5.2.2 of NTC Concrete are utilized to obtain the actual amount of steel required as well as the maximum allowable and minimum required steel. These values are reported as ROW, ROWMX and ROWMN in the output and can be printed using the parameter TRACK 1.0 (see Table 10A.1). In addition, the maximum, minimum and actual bar spacing are also printed. It is important to note that beams are designed for flexural moment MZ only. The moment MY is not considered in the flexural design. Design for Shear Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear forces are calculated at a distance (d+SFACE) and (d+EFACE) away from the end nodes of the beam. SFACE and EFACE have default values of zero unless provided under parameters (see Table 10A.1). Note that the value of the effective depth "d" used for this purpose is the update value and accounts for the actual c.g. of the main reinforcement calculated under flexural design. Clauses 2.1.5-6 and 5.2.4 of NTC Concrete are used to calculate the reinforcement for shear forces and torsional moments. Based on the total stirrup reinforcement required, the size of bars, the spacing, the number of bars and the distance over which they are provided are calculated. Stirrups due to geometric conditions are assumed to be 2-legged, due to design conditions could be 2 or 4-legged. Design for Anchorage In the output for flexural design, the anchorage details are also provided. At any particular level, the START and END coordinates of the layout of the main rein forcement is described along with the information whether anchorage in the form of a hook or continuation is required or not at these START and END points. Note that the coordinates of these START and END points are obtained after taking into account the anchorage requirements.

11-7


11-8

Section 11A

Anchorage length is calculated on the basis of described in Section 3.1 of NTC concrete. In case selects 2 different diameters for the main or reinforcement, only the anchorage for the largest analyzed. Output

the Clauses the program compression diam eter is

Section 11A

ACTUAL OUTPUT FROM DESIGN ===================================================================== BEAM NO. 1 DESIGN RESULTS - FLEXURE PER CODE NTC FOR THE DESIGN AND CONSTRUCTION OF CONCRETE STRUCTURES,DDF LEN 525.00(cm) FY - 4200. FC 250. SIZE 30.00 X 80.00(cm) LEVEL HEIGHT BAR INFO FROM TO ANCHOR (cm) (cm) (cm) STA END _____________________________________________________________________ 1 4. 8 - -NUM, 5 0. 39. YES NO 1 4. 1 - -NUM, 4 0. 39. 2 8. 3 - -NUM, 5 0. 39. YES NO |---------------------------------------------------------------| | CRITICAL MOMENT=5978000.50 Kg cm AT 0.00 (cm)LOAD 1| | REQD STEEL= 24.41 (cm2)ROW=0.0109 ROWMX=0.0190 ROWMN=0.0026 | | REQD COMP STEEL= 0.00 (cm2) | | MAX/MIN/ACTUAL BAR SPACING= 24.14/ 3.18/ 3.45 (cm) | | COMP MAX/MIN/ACTUAL BAR SPACING= 0.00/ 0.00/ 0.00 (cm) | | BASIC/REQD. DEVELOPMENT LENGTH = 40.07/ 39.08(cm) | |----------------------------------------------------------------| Cracked Moment of Inertia Iz at above location = 1015658.4 cm^4 3 77. 10 - NUM, 4 0. 45. YES NO 4 73. 9 - -NUM, 4 0. 45. YES NO |---------------------------------------------------------------| | CRITICAL MOMENT=5978000.50 Kg cm AT 0.00 (cm)LOAD 1| | REQD STEEL= 24.17 (cm2)ROW=0.0107 ROWMX=0.0190 ROWMN=0.0026 | | REQD COMP STEEL= 0.00 (cm2) | | MAX/MIN/ACTUAL BAR SPACING= 24.46/ 2.54/ 2.72 (cm) | | COMP MAX/MIN/ACTUAL BAR SPACING= 0.00/ 0.00/ 0.00 (cm) | | BASIC/REQD. DEVELOPMENT LENGTH = 32.00/ 44.81(cm) | |----------------------------------------------------------------|Cracked Moment of Inertia Iz at above location = 1008728.7 cm^4 REQUIRED REINF. STEEL SUMMARY : ------------------------------SECTION REINF STEEL(+VE/-VE) MOMENTS(+VE/-VE) LOAD(+VE/-VE) ( CM ) (SQ. CM ) (KG -CM ) 0.00 24.67/ 24.67 5978000./ 5978000.50 0/ 0 525.00 24.67/ 24.67 5978000./ 5978000.50 0/ 0 B E A M N O. 1 D E S I G N R E S U L T S – SHEAR AT START SUPPORT - Vu=41850.00 Kg Vc= 6074.49 Kg Vs=44719.39 Kg Tu= 0.00 Kg cm Tc= 0.00 Kg cm Ts= 0.00 Kg cm LOAD 0 NO STIRRUPS ARE REQUIRED FOR TORSION. REINFORCEMENT IS REQUIRED FOR SHEAR. PROVIDE NUM. 2.5 2-LEGGED STIRRUPS AT 7.(cm) C/C FOR 176.(cm) ADDITIONAL LONGITUDINAL STEEL REQD. FOR TORSIONAL RESISTANCE = 0.00 (cm2) AT END SUPPORT - Vu=37450.00 Kg Vc= 6074.49 Kg Vs=39219.39 Kg Tu= 0.00 Kg cm Tc= 0.00 Kg cm Ts= 0.00 Kg cm LOAD 0 NO STIRRUPS ARE REQUIRED FOR TORSION. REINFORCEMENT IS REQUIRED FOR SHEAR. PROVIDE NUM. 2.5 2-LEGGED STIRRUPS AT 8.(cm) C/C FOR 176.(cm) ADDITIONAL LONGITUDINAL STEEL REQD. FOR TORSIONAL RESISTANCE = 0.00 (cm2)

11-9


11-10

Section 11A

11A.6 Column Design Columns design in STAAD per the Mexican code is performed for axial force and uniaxial as well as biaxial moments. All active loadings are checked to compute reinforcement. The loading which produces the largest amount of reinforcement is called the critical load. Column design is done for square, rectangular and circular sections. For rectangular and circular sections, reinforcement is always assumed to be equally distributed on all faces. This means that the total number of bars for these sections will always be a multiple of four (4). If the MMAGx & -MMAGy parameters are specified, the column moments are multiplied by the corresponding MMAG value to arrive at the ultimate moments on the column. Minimum eccentricity conditions to be satisfied according to section 2.1.3.a are checked. Method used: Bresler Load Contour Method Known Values: Pu, Muy, Muz, B, D, Clear cover, Fc, Fy Ultimate Strain for concrete : 0.003 Steps involved : 1. Assume some reinforcement. Minimum reinforcement (1% for ductile design or according to section 4.2.2 ) is a good amount to start with. 2. Find an approximate arrangement of bars for the assumed reinforcement. 3. Calculate PNMAX = Po, where Po is the maximum axial load capacity of the section. Ensure that the actual nominal load on the column does not exceed PNMAX. If PNMAX is less than the axial force Pu/FR, (FR is the strength reduction factor) increase the reinforcement and repeat steps 2 and 3. If the reinforcement exceeds 6% (or 4% for ductile design), the column cannot be designed with its current dimensions. 4. For the assumed reinforcement, bar arrangement and axial load, find the uniaxial moment capacities of the column for the

Section 11A

11-11

Y and the Z axes, independently. These values are referred to as MYCAP and MZCAP respectively. 5. Solve the Interaction Bresler equation:  Mny  Mycap



Mnz +  Mycap

Where a = 1.24. If the column is subjected to uniaxial moment: a =1 6. If the Interaction equation is satisfied, find an arrangement with available bar sizes, find the uniaxial capacities and solve the interaction equation again. If the equation is satisfied now, the reinforcement details are written to the output file. 7. If the interaction equation is not satisfied, the assumed reinforcement is increased (ensuring that it is under 6% or 4% respectively) and steps 2 to 6 are repeated. By the moment to check shear and torsion for columns the sections have to be checked as beams and the most strict of both shear and torsion reinforcement adopted.

11A.7 Column Interaction The column interaction values may be obtained by using the design parameter TRACK 1.0 or TRACK 2.0 for the column member. If a value of 2.0 is used for the TRACK parameter, 12 different Pn-Mn pairs, each representing a different point on the Pn-Mn curve are printed. Each of these points represents one of the several Pn-Mn combinations that this column is capable of carrying about the given axis, for the actual reinforcement that the column has been designed for. In the case of circular columns, the values are for any of the radial axes. The values printed for the TRACK 1.0 output are:


11-12

Section 11A

P0 = Maximum allowable pure axial load on the column (moment zero). Pnmax = Maximum allowable axial load on the column. P_bal = Axial load capacity of balanced strain condition. M_bal = Uniaxial moment capacity of balanced strain condition. E_bal = M_bal / P_bal = Eccentricity of balanced strain condition. M0 = Moment capacity at zero axial load. P_tens = Maximum permissible tensile load on the column. Des. Pn = Pu/FR where FR is the Strength Reduction Factor and Pu is the axial load for the critical load case. Des.Mnx = Mux*MMAGx/FR where FR is the Strength Reduction Factor and Mu is the bending moment for the appropriate axis for the critical load case.

Mu =  (Mux.Mmagx)²+ (Muy.Mmagy)² e/h

= (Mn/Pn)/h

where h is the length of the column

11A.8 Column Design Output The next table illustrates different levels of the column design output.

Section 11A

The output is generated without any TRACK specification: ==================================================================== COLUMN

NO.

1

DESIGN PER

- AXIAL + BENDING

FY -4200.0 FC - 294.1 Kg/cm2 CIRC SIZE AREA OF STEEL REQUIRED = 128.506

100.0(cm)DIAMETER

BAR CONFIGURATION REINF PCT. LOAD LOCATION PHI ---------------------------------------------------------46 - NUMBER 6 (EQUALLY SPACED)

1.669

1

END

0.700

TRACK=1 generates the following additional output: COLUMN INTERACTION: MOMENT ABOUT Z/Y -AXIS (Kg-cm ) -------------------------------------------------------P0 Pn max P-bal. M-bal. e-bal.(cm) 2095196.38 2095196.38 727411.12 29235398.00 40.2 M0 P-tens. Des.Pn 'Des.Mn e/h 20606994.00 -550620.00 0.00 20000000.00 NaN -------------------------------------------------------TRACK=2 generates the following output in addition Pn Mn | 1934027.38 5373253.50 P0 |* 1772858.50 11408365.00 | * 1611689.50 16296947.00 Pn,max|__* 1450520.62 20083028.00 | * 1289351.62 23117562.00 Pn | * 1128182.62 25462606.00 NOMINAL| * AXIAL| * COMPRESSION| * Pb|-------*Mb | * ___________|____*_______ | * M0 Mn, | * BENDING P-tens|* MOMENT

to all the above: Pn Mn 967013.69 27278232.00 805844.75 28658428.00 644675.81 29473708.00 483506.84 28901764.00 322337.91 27205616.00 161168.95 24433192.00

11A.9 Slab Design Slab are designed per Mexican NTC specifications. To design a slab, it must be modeled using finite elements. Element design will be performed only for the moments MX and MY at the center of the element. Design will not be performed for FX, FY, FXY, MXY. Also, design is not performed at any other point on the surface of the element. Shear is checked with Q. A typical example of element design output is shown below. The reinforcement required to resist Mx moment is denoted as

11-13


11-14

Section 11A

longitudinal reinforcement and the reinforcement required to resist My moment is denoted as transverse reinforcement. The parameters FYMAIN, FC, CLEAR, DIM_PRECAUTION, and EXPOSED_SOIL_WEATHER listed in Table 3.1 are relevant to slab design. Other parameters mentioned are not used in slab design.

ELEMENT DESIGN SUMMARY ---------------------ELEMENT

LONG. REINF (SQ.CM/M )

MOM-X /LOAD (T -M /M )

1 TOP : Longitudinal direction 1 BOTT: Transverse direction 1 TOP : 2.239 0.00 BOTT: 3.758 983.00 1 SHEAR CAPACITY

TRANS. REINF (SQ.CM/M )

MOM-Y /LOAD (T -M /M )

- Only minimum steel required. - Only minimum steel required. / 0 3.252 983.00 / / 1 1.684 0.00 /

3794.73 Kg ***PASS***

1 0

11-15

Steel Design per Mexican Code Section

11B

11B.1 General The program is based in: Complementary Technical Standards for the Design and Construction of Steel Structures – Dec. 1987. (Normas Técnicas Complementarias para Diseño y construcción de Estructuras Metálicas) of the Mexican Construction Code for the Federal District –Aug. 1993 (Reglamento de Construcciones para el Distrito Federal). The design philosophy considered is that of the Load Cases and Resistance Method or Limit States Design usually known as Load and Resistance Factor Design (LRFD). Structures are designed and proportion ed taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit -state are recognized-ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation of the Mexican Standards for steel structures, members are proportioned to resist the design loads without exceeding the limit states of strength, and stability. It allows to check deformation to verify serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria as augmented by the designer in

Steel Design Per Mexican Code

11-16

Section 11B

specification of allowable member depths, desired section type, or other such parameters. The code checking portion of the program checks that main code requirements for each selected section are met and identifies the governing criteria. The following sections describe the salient features of the Mexican specifications as implemented in STAAD steel design. A brief description of the fundamental concepts is presented here.

11B.2 Limit States Design Fundamentals The primary objective of the Limit States Design Specification is to provide a uniform reliability for all steel structures under various loading conditions. The Limit States Design Method uses separate factors for each load and resistance. Because the different factors reflect the degree of uncertainty of different loads and combinations of loads and of the accuracy of predicted strength, a more uniform reliability is possible. The method may be summarized by the inequality Yi Qi < Rn FR On the left side of the inequality, the required strength is the summation of the various load effects, Qi, multiplied by their respective load factors, yi. The design strength, on the right side, is the nominal strength or resistance, Rn, multiplied by a resistance factor, FR. In the STAAD implementation of the Mexican Standards, it is assumed that the user will use appropriate load factors and create the load combinations necessary for analysis. The design portion of the program will take into consideration the load effects (forces and moments) obtained from analysis. In calculation of resistances of various elements (beams, columns etc.), resistance (nomina l strength) and applicable resistance factor will be automatically considered.

Section 11B

11B.3 Member End Forces and Moments Member end forces and moments in the member result from loads applied to the structure. These forces are in the local member coordinate system. the following figures show the member end actions with their directions.

11-17


11-18

Section 11B

11B.4 Section Classification The Limit States Design specification allows inelastic deformation of section elements. Thus local buckling becomes an important criterion. Steel sections are classified as compact (type 2), noncompact (type 3), or slender element(type 4), sections depending upon their local buckling characteristics, besides sections type 1 are able for plastic design. This classification is a function of the geometric properties of the section. The design procedures are different depending on the section class. STAAD is capable of determining the section classification for the standard shapes and design accordingly.

11B.5 Member in Axial Tension The criteria governing the capacity of tension members is based on two limit states. The limit state of yielding in the gross section is intended to prevent excessive elongation of the member. The second limit state involves fracture at the section with th e minimum effective net area. The net section area may be specified by the user through the use of the parameter NSF (see Table 10B.1), that always refers to the gross section. STAAD calculates the tension capacity of a given member based on these two limit states and proceeds with member selection or code check accordingly. In addition to the tension resistance criterion, the user defines if tension members are required to satisfy slenderness limitations which are a function of the nature of use of the member (main load resisting component, bracing member, etc.). In both the member selection and code checking process, STAAD immediately does a slenderness check on appropriate members before continuing with other procedures for determining the adequacy of a given member.

Section 11B

11B.6 Axial Compression The column strength equations take into account inelastic deformation and other recent research in column behavior. Two equations governing column strength are available, one for inelastic buckling and the other for elastic or Euler buckling. Both equations include the effects of residual stresses and initial out -ofstraightness. Compression strength for a particular member is calculated by STAAD according to the procedure outlin ed in Section 3.2 of the NTC. For slender elements, the procedure described in Section 2.3.6.NTC is also used. The procedures of Section 3.2 of the Commentaries, design helps and examples of the Complementary Technical Standards for the Design and Construction of Steel Structures (de los Comentarios, ayudas de diseño y ejemplos de las Normas Técnicas Complementarias para el Diseño y Construcción de Estructuras Metálicas, DDF (Comentarios - Julio 1993) were implemented for the determination of design stren gth for these limit states. Effective length for calculation of compression resistance may be provided through the use of the parameters KY, KZ and/or LY, LZ. If not provided, the entire member length will be taken into consideration. In addition to the compression resistance criterion, compression members are required to satisfy slenderness limitations which are a function of the nature of use of the member (main load resisting component, bracing member, etc.). In both the member selection and code checking process, STAAD immediately does a slenderness check on appropriate members before continuing with other procedures for determining the adequacy of a given member.

11-19


11-20

Section 11B

11B.7 Flexural Design Strength In the Limit States Design Method, the flexural design strength of a member is determined mainly by the limit state of lateral torsional buckling. Inelastic bending is allowed and the basic measure of flexural capacity is the plastic moment capacity of the section. The flexural resistance is a function of plastic moment capacity, actual laterally unbraced length, limiting laterally unbraced length, buckling moment and the bending coefficient. The limiting laterally unbraced length Lu and flexural resistance Mr are functions of the section geometry and are calculated as per the procedure of Section 3.3.2 of the NTC. The purpose of bending coefficient Cb is to account for the influence of the moment gradient on lateral-torsional buckling. This coefficient can be specified by the user through the use of parameter CB or CBy (see Table 10B.1) or may be calculated by the program (according to LRDF USA specification) if CB is specified as 0.0. In the absence of the parameter CB, a default value of 1.0 will be used. To specify laterally unsupported length, either of the parameters UNL and UNF (see Table 10B.1) can be used. It is taken into account the reduction of flexural resistance due to slender web according to section 4.5.8 of the NTC For the sections where the web and flange are slender the LRDF USA specification was used.

Section 11B

Stress areas due to bending about y axis (MY)

Notes: the local X axis goes into the page; the Global Y axis is vertical upwards; the shaded area indicates area under compression; the area not shaded indicates area under tension.

Stress areas due to bending about Z axis (MZ)

11-21


11-22

Section 11B

11B.8 Design for Shear The procedure of Sect. 3.3.3 of the NTC is used in STAAD to design for shear forces in members. Besides combined bending and shear is checked according to section 3.3.4 of the NTC, considering also the limits for stiffeners of the web according to sections 4.5.6/7 of the NTC. Shear in wide flanges and channel sections is resisted by the area of the web/s..

11B.9 Combined Compression Axial Force and Bending The interaction of flexure and axial forces in singly and doubly symmetric shapes is governed by formulas of the Section 3.4 of the NTC. These interaction formulas cover the general case of biaxial bending combined with axial force. They are also valid for uniaxial bending and axial force. It is considered that the frames are part of structures that have shear walls or rigid elements so that the lateral displacements of a floor could be disregarded. The program has included for mulas to include structures with lateral displacements in the future considering for B2 the columns individually and not the complete floor analysis. It is taken into account if the elements have transverse loads and if the ends are angularly restrained.

11B.10 Combined Tension Axial Force and Bending Based on Section 3.5 4 of the NTC.

Section 11B

11B.11 Design Parameters Design per Mexican Standards is requested by using the CODE. Other applicable parameters are summarized in Table 10B.1. These parameters communicate design decisions from the engineer to the program and thus allow the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure. The parameters DMAX and DMIN may only be used for member selection only. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

11-23


11-24

Section 11B

TABLA 11B.1. DESIGN PARAMETERS ACCORDING TO MEXICAN STANDARS - STEEL Parameter Default Description Name

Value

KX

1.0

K value for flexural-torsional buckling

KY

1.0

K value in local Y axis- Usually minor axis

KZ

1.0

K value in local Z axis- Usually major axis

LX

Member length

Length for flexural-torsional buckling

LY

Member length

LZ

Member length

Length to calculate slenderness ratio for buckling about local Y axis. Length to calculate slenderness ratio for buckling about local Z axis.

FYLD

2530 kg/cm2

Minimum Yield strength of steel

FU NSF

4230 Kg/cm2 1

Ultimate tensile strength of steel Net section factor for tension members

UNT

Member length

Unsupported length (L) of the top* flange for calculating flexural strength . Will be used only if compression is in the top flange.

UNB

Member length

Unsupported length (L) of the bottom* flange for calculating flexural strength . Will be used only if compression is in the bottom flange.

STIFF

Member length

Spacing of stiffeners for beams for shear design

Cb y Cby

1

Coefficient C defined per section 3.3.2.2. If Cb is set to 0.0 it will be calculated by the program according to LRFD USA (CbMex=1/CbUSA). Any other value will be directly used in the design.

TRACK

0

0 = Suppress all design strengths 1 = Print all design strengths 2 = Print expanded design output

DMAX

114 cm


DMIN RATIO

0.0 cm 1.0

Minimum allowable depth Permissible ratio of actual load effect and design strength

BEAM

0

0: Design at ends and those locations specified by SECTION command. 1: Design at ends and at every y cada 1/12th point along member length

Rigid_to_H_Loads

TRUE

Defines if the structure has elements to bear the wind load ( shear walls, wind trusses or bracing

Section 11B

11-25


IRREG

Value rigid elements ) that restrict lateral displacements and allow to disregard slenderness effects. Variable defined for the whole structure indicating if it is regular or irregular according to section 3.4 of the NTC. IRREG=1 for columns being part of irregular structures.

0

I_NO_OXIG

0

IMAIN_MEM

0

Ccomb

1


TRUE

Defined for I shapes or tubes Curve Definition according to NTC.3.2.2.1a) I_NO_OXIG.= 0 implies n=1.4 laminated I shapes, tubes or built up with 3 or 4 welded plates obtained from wider plates cuts with oxygen. I_NO_OXIG.= 1 implies n=1 I shapes, tubes or built up with 3 or 4 welded plates n is defined by the program IMAIN_MEM=0 MAIN MEMBER IMAIN_MEM=1 Secondary and wind trusses Cfactor for combined forces when there are transverse loads in the members. Section 3.4.3.3.ii NTC Ccomb=1 If members ends are restricted angularly. Ccomb=0.85 If members ends are not restricted angularly. DUCTILE FRAMES ACCORDING TO SECTION 11. Main design conditions are considered (not including, at the moment, geometric ones)

KX

1.0

K value for flexural-torsional buckling

KY

1.0

K value in local Y axis- Usually minor axis

KZ

1.0

K value in local Z axis- Usually major axis

LX

Member length

Length for flexural-torsional buckling

LY

Member length

LZ

Member length

Length to calculate slenderness ratio for buckling about local Y axis. Length to calculate slenderness ratio for buckling about local Z axis.

FYLD

2530 kg/cm2

Minimum Yield strength of steel

FU

4230 Kg/cm2

Ultimate tensile strength of steel


11-26

Section 11B


Value

NSF

1


UNT

Member length

Unsupported length (L) of the top* flange for calculating flexural strength . Will be used only if compression is in the top flange.

UNB

Member length

STIFF

Member length

Unsupported length (L) of the bottom* flange for calculating flexural strength . Will be used only if compression is in the bottom flange. Spacing of stiffeners for beams for shear design

Cb y Cby

1

Coefficient C defined per section 3.3.2.2. If Cb is set to 0.0 it will be calculated by the program according to LRFD USA (CbMex=1/CbUSA). Any other value will be directly used in the design.

TRACK

0

0 = Supress all design strengths 1 = Print all design strengths 2 = Print expanded design output

DMAX

114 cm


DMIN RATIO

0.0 cm 1.0

Minimum allowable depth Permissible ratio of actual load effect and design strength

BEAM

0

0: Design at ends and those locations specified by SECTION command. 1: Design at ends and at every y cada 1/12th point along member length

Rigid_to_H_Loads

TRUE

Defines if the structure has elements to bear the wind load ( shear walls, wind trusses or bracing rigid elements ) that restrict lateral displacements and allow to disregard slenderness effects.

IRREG

0

Variable defined for the whole structure indicating if it is regular or irregular according to section 3.4 of the NTC. IRREG=1 for columns being part of irregular structures.

I_NO_OXIG

0

Defined for I shapes or tubes Curve Definition according to NTC.3.2.2.1a) I_NO_OXIG.= 0 implies n=1.4 laminated I shapes, tubes or built up with 3 or 4 welded plates obtained from wider plates cuts with oxygen.

Section 11B


Value I_NO_OXIG.= 1 implies n=1 I shapes, tubes or built up with 3 or 4 welded plates n is defined by the program

IMAIN_MEM

0

Ccomb

1


TRUE

IMAIN_MEM=0 MAIN MEMBER IMAIN_MEM=1 Secondary and wind trusses Cfactor for combined forces when there are transverse loads in the members. Section 3.4.3.3.ii NTC Ccomb=1 If members ends are restricted angularly. Ccomb=0.85 If members ends are not restricted angularly. DUCTILE FRAMES ACCORDING TO SECTION 11. Main design conditions are considered (not including, at the moment, geometric ones)

* Top and Bottom represent the positive and negative side of the local Y axis (local Z axis if SET Z UP is used. Note: For deflection check, parameters DFF, DJ1 and DJ2 from Table 2.1 may be used. All requirements remain the same.

11B.12 Code Checking and Member Selection Both code checking and member selection options are available in STAAD Mexican Standards implementation.

11-27


11-28

Section 11B

11B.13 Tabulated Results of Steel Design Results of code checking and member selection are presented in a tabular format. CRITICAL COND refers to the section of the Mexican NTC which governed the design. If the TRACK is set to 1.0, member design strengths will be printed out.

Section 12

Russian Codes

12-1

Concrete Design Per Russian Code (SNiP 2.03.01-84*) Section

12A

12A.1 General Russian Code SNiP 2.03.0184* “Plain concrete and concrete structures” is based on the method of limit states. Code SNiP 2.03.0184* defines two groups of limit states. Analysis according to the first group of limit states is performed to avoid the following phenomena:    

brittle, plastic or other type of failure, loss by structure of stable form or position, fatigue failure, failure due to the action of load actions and unfavourable environmental effects.

Analysis according to the second group of limit states is performed to avoid the following phenomena:  

excessive and longterm opening of cracks if they are allowed according to service conditions, excessive displacements.

Analysis of structures for the first group of limit states is performed with the use of the maximum (design) loads and actions. Analysis of structures for the second group of limit states is made in accordance with the operational (normative) loads and actions. Ratio between design and normative loads is called reliability coefficient for loads which is determined according to SNiP 2.01.07.-85 “Loads and actions”.

Concrete Design Per Russian Code

12-2

Section 12A

Reliability coefficient n for destination according to SNiP 2.01.07.-85 shall be considered in determination of loads and their combinations. Program STAAD/Pro makes it possible to calculate reinforcement for concrete members according to codes of many countries round the World and Russian Code SNiP 2.03.01  84* inclusive. Algorithms for calculation of reinforcement of concrete linear (beams, columns) and 2D (two dimensional) (slabs, walls, shells) members are incorporated in program STAAD/Pro. Not only Code SNiP 2.03.01  84* but also the “Guide for design of plain concrete and reinforced concrete structures from normal weight and lightweight concrete (to SNiP 2.03.01 84)” have been used in creation of these algorithms. It is possible using program STAAD/Pro to calculate reinforcement for beams of rectangular or T section and for columns of rectangular or circular section (Fig.1).

Figure 1 - Notation of dimensions for rectangular, circular and T sections

Flange of T-shape beams may be situated at the top zone of the section if the angle BETA=0 0 , or at the bottom zone of the section, if BETA=180 0 .

Section 12A

12A.2 Input Data Entry of data of cross-sections of beams and columns is made by the use of MEMBER PROPERTIES command, and thicknesses of 2D members are entered by ELEMENT PROPERTY command. Example: UNIT MM MEMBER PROPERTIES * Columns of rectangular cross-section 1 TO 16 PRI YD 350. ZD 350. * Columns of circular cross-section 17 TO 22 PRI YD 350. * Beams of T cross-section 23 TO 40 PRI YD 450. ZD 550. YB 230. ZB 200. UNIT METER ELEMENT PROPERTY 41 TO 100 THICKNESS 0.14 101 TO 252 THICKNESS 0.16 * Flange of T beams is located at the bottom zone of cross-section BETA 180. MEMB 23 TO 40 Commands for calculation of reinforcement are located in the input data file after the command of analysis and as a rule, after output commands to print results of calculation. Example: * Command of analysis PERFORM ANALYSIS . .* Output command to print results of calculation (according to user’s judgment) .

12-3


12-4

Section 12A

* Command of loading and their combinations considered in design LOAD LIST 1 5 TO 9 * Command to start reinforcement calculation procedure START CONCRETE DESIGN CODE RUSSIAN .* List of parameters being used in reinforcement calculation . . BCL 20. MEMB 17 TO 22 CL1 0.04 MEMB 1 TO 40 DD2 10. MEMB 23 TO 40 CRA 0.036 MEMB 41 TO 252 . . . * Command of beam reinforcement calculation DESIGN BEAM 23 TO 40 * Command of column reinforcement calculation DESIGN COLUMN 1 TO 22 * Command of calculation 2D elements (slabs, walls, shells) DESIGN ELEMENT 41 TO 252 * Command of interruption reinforcement calculation END CONCRETE DESIGN In tables 1, 2 and 3 information about parameters used for calculation of reinforcement for beams, columns and 2D (two dimensional) members is presented. Values of parameters do not depend on UNIT command. In the file of input data only such parameters have to be taken, the values of which differ from determined in the program.

Section 12A

12-5

Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 1- Names of parameters for Concrete design according to Russian Code СНиП 2.03.0184* for beams.

No. 1

Parameter name NLT

Default value 1

Description Number of long-term loading case

2

RCL

3

Class of longitudinal reinforcement:  RCL = 1, if class of reinforcement is A-I;  RCL = 2, if class of reinforcement is A-II;  RCL = 3, if class of reinforcement is A-III;  RCL = 33, if class of reinforcement is A-IIIb;  RCL = 4, if class of reinforcement is A-IV;  RCL = 5, if class of reinforcement is A-V;  RCL = 6, if class of reinforcement is A-VI;  RCL = 7, if class of reinforcement is A-VII;  RCL = 77, if class of reinforcement is K-7;  RCL = 8, if class of reinforcement is B-II;  RCL = 9, if class of reinforcement is Bp-II;  RCL = 10, if class of reinforcement is Bp-I;  RCL = 19, if class of reinforcement is K-19

3

USM

1.

Total product of service conditions coefficients for longitudinal reinforcement ( s )

4

UB2

0.9

5

DD1

16.

6

DD2

16.

Diameter of shear reinforcement bars for beam;

7

BCL

15.

Compression class of concrete

8

UBM

1.

Product of service conditions coefficients for concrete, except UB2 ( b ) Parameter of concrete hardening conditions:  TEM=0, for natural hardening conditions;  TEM=1, for steam hardening conditions

9

TEM

0.

10

CL1

0.05

Specific service conditions coefficient for concrete ( b2 ) Diameter of longitudinal reinforcement bars in beam tension zone

Distance from top/bottom fiber of beam cross


12-6

Section 12A

No.

Parameter name

Default value

Description section to the center of longitudi nal reinforcement bar;

11

CL2

0.05

Distance from left/right side of beam cross section to the center of longitudinal reinforcement bar

12

WST

0.4

Ultimate width of short-term crack

13

WLT

0.3

Ultimate width of long-term crack

14

SSE

0

Limit state parameter for beam design  SSE=0, if calculation of reinforcement amount must be carried out according to the requirements of load carrying capacity (the first limit state);  SSE=1, if calculation of reinforcement amount must be carried out according to the cracking requirements (the second limit state) Class             

of shear reinforcement: RSH = 1, if class of reinforcement is A-I; RSH = 2, if class of reinforcement is A-II; RSH = 3, if class of reinforcement is A-III; RSH = 33, if class of reinforcement is AIIIb; RSH = 4, if class of reinforcement is A-IV; RSH = 5, if class of reinforcement is A-V; RSH = 6, if class of reinforcement is A-VI; RSH = 7, if class of reinforcement is A-VII; RSH = 77, if class of reinforcement is K-7; RSH = 8, if class of reinforcement is B-II; RSH = 9, if class of reinforcement is Bp-II; RSH = 10, if class of reinforcement is Bp -I; RSH = 19, if class of reinforcement is K-19

15

RSH

1

16

FWT

ZD

Design width of beam top flange. Use for beam design only with default value provided as ZD in member properties.

17

FWB

ZB

Design width of beam bottom flange. Use for beam design only with default value provided as ZB in member properties.

Section 12A

12-7

No.

Parameter name

Default value

18

DEP

YD

Design depth of beam section. Use for beam design only with default value provided as YD in member properties.

19

SFA

0.

Face of support location at the start of the beam. Use for beam design only.

20

EFA

0.

Face of support location at the end of the beam. Use for beam design only.

13

Number of equally-spaced sections for beam design. Use for beam design only. Upper limit is equal to 20.

21

NSE

Description

Table 2 - Names of parameters for Concrete design according to Russian Code СНиП 2.03.0184* for columns

No. 1

2

Parameter name

Default value

NLT

1

Number of long-term loading case

3

Class of longitudinal reinforcement:  RCL = 1, if class of reinforcement is A-I;  RCL = 2, if class of reinforcement is A-II;  RCL = 3, if class of reinforcement is A-III;  RCL = 33, if class of reinforcement is A-IIIb;  RCL = 4, if class of reinforcement is A-IV;  RCL = 5, if class of reinforcement is A-V;  RCL = 6, if class of reinforcement is A-VI;  RCL = 7, if class of reinforcement is A-VII;  RCL = 77, if class of reinforcement is K-7;  RCL = 8, if class of reinforcement is B-II;  RCL = 9, if class of reinforcement is Bp-II;  RCL = 10, if class of reinforcement is Bp-I;  RCL = 19, if class of reinforcement is K-19 Total product of service conditions coefficients for longitudinal reinforcement ( s )

RCL

Description

3

USM

1.

4

UB2

0.9

Specific service conditions coefficient for concrete ( b2 )

5

DD1

16.

Minimum diameter of longitudinal reinforcement


12-8

Section 12A

Parameter name

No.

Default value

Description bars for column

6

DD2

16.

Maximum diameter of longitudinal reinforcement bars for column

7

BCL

15.


8

UBM

1.

Product of service conditions coefficients for concrete, except UB2 ( b ) Parameter of concrete hardening conditions:  TEM=0, for natural hardening conditions;  TEM=1, for steam hardening conditions

9

TEM

0.

10

CL1

0.05

11

ELY

1.

Column's length coefficient to evaluate slenderness effect in local Y axis

12

ELZ

1.

Column's length coefficient to evaluate slenderness effect in local Z axis

Distance from edge of column cross section to the center of longitudinal reinforcement bar

Тable 3 - Names of parameters for Concrete design according to Russian Code (SNiP 2.03.01-84*) for slabs and/or walls

No. 1

2

Parameter name NLT

RCL

Default value 1

3

Description Number of long-term loading case Class of longitudinal reinforcement:  RCL = 1, if class of reinforcement is A-I;  RCL = 2, if class of reinforcement is A-II;  RCL = 3, if class of reinforcement is A-III;  RCL = 33, if class of reinforcement is AIIIb;  RCL = 4, if class of reinforcement is A-IV;  RCL = 5, if class of reinforcement i s A-V;  RCL = 6, if class of reinforcement is A-VI;  RCL = 7, if class of reinforcement is A-VII;  RCL = 77, if class of reinforcement is K-7;  RCL = 8, if class of reinforcement is B-II;  RCL = 9, if class of reinforcement is Bp-II;  RCL = 10, if class of reinforcement is Bp-I;

Section 12A

No.

Parameter name

Default value

12-9

Description 

RCL = 19, if class of reinforcement is K-19

3

USM

1.

Total product of service conditions coefficients for longitudinal reinforcement ( s )

4

UB2

0.9

Specific service conditions coefficient for concrete ( b2 )

5

SDX

16.

Diameter of reinforcing bars located in the first local (X) direction of slab/wall

6

SDY

16.

Diameter of reinforcing bars located in the second local (Y) direction of slab/wall

7

BCL

15.


8

UBM

1.

Product of service conditions coefficients for concrete, except UB2 ( b )

9

TEM

0.

Parameter of concrete hardening conditions:  TEM=0, for natural hardening conditions;  TEM=1, for steam hardening conditions

10

CL

0.05

Distance from top/bottom face of slab/wall element to the center of longitudinal reinforcing bars located in first local (X) direction. (Main thickness of top/bottom concrete cover for slab/wall element)

11

CRA

0.05

Distance from top/bottom face of slab/wall element to the center of transverse reinforcing bars located in second local (Y) direction (Secondary thickness of top/bottom concrete cover for slab/wall)

12

WST

0.4

Ultimate width of short-term crack

13

WLT

0.3

Ultimate width of long-term crack

14

STA

0

Parameter of limit state for slab/wall design:  STA=0, if calculation of nons ymmetrical reinforcement must be carried out according to the requirements of load carrying capacity (the first limit state);  STA=1, if calculation of symmetrical reinforcement must be carried out according to the requirements of load carrying capacity (the first limit state);


12-10

Section 12A

No.

Parameter name

Default value

Description 



STA=2, if calculation of nonsymmetrical reinforcement must be carried according to the cracking requirements (the second limit state); STA=3, if calculation of symmetrical reinforcement must be carried according to the cracking requirements (the second limit state)

15

SELX

0.

Design length of wall member to evaluate slenderness effect in local X axis

16

SELY

0.

Design length of wall member to evaluate slenderness effect in local Y axis

0

Design parameter of slab/wall reinforcement:  MMA=0, if reinforcement calculation must be applied by stresses in local axis;  MMA=1, if reinforcement calculation must be applied by principal stresses

1

Design parameter of slab/wall reinforcement:  MMB=0, if the effect of additional eccentricity is not taken into account;  MMB=1, if the effect of additional eccentricity is taken into account

17

18

MMA

MMB

12A.3 Beams Reinforcement for beams of rectangular and T cross-section can be calculated. In calculation of longitudinal reinforcement bending moment about local axis Z loc and torsional moments are considered, but influence of longitudinal forces and bending moments in relation to local axis Yloc is ignored. In calculation of transverse reinforcement shear forces parallel t o local axis Yloc and torsional moments are taken into account.

Section 12A

Reinforcement for beams can be calculated either from conditions of strength or from conditions of open crack width limitation (see parameter SSE). Parameters SFA and ЕFA are considered only in calculation of transverse reinforcement. In general case calculation of reinforcement for beams is carried out two times – according to strength conditions and according to conditions of open crack width limitation. In reinforcement calculations from conditions of strength design values of load have to be taken and in calculations from conditions of crack width limitation – characteristic (normative) load values are used. Both calculations can be carried out in one session with the use multiple analysis possibility of the program STAAD.Pro. In most cases calculation of reinforcement is carried out with account only of a part of loadings. In such cases command LOAD LIST is used, in which numbers of loads considered in calculation are indicated. Number of permanent and long-term loads equal to parameter NLT must be included into the list of considered loads. It has to be noted, that values of parameters DD1 and DD2 have influence not only on the width of opened crack but also in som e cases, on design and normative reinforcement resistances. Parameter BCL can be equal to any value of concrete compression strength class given in SNiP 2.03.0184* and to any intermediate value as well. It should be remembered, that accuracy of results of calculation of transverse reinforcement increases with the value of parameter NSE. Parameters SFA and ЕFA are considered only in calculations of transverse reinforcement. Beam 1 is shown in Figure 2 with rigid intervals the lengths of which are: at th e start of the beam 0.3m and at the end – 0.2m. In modeling of the beam the following command can be used.

12-11


12-12

Section 12A

MEMBER OFFSET 1 START 0.3 0 0 1 END -0.2 0 0

Figure 2 - Diagram of a beam with rigid intervals

When command MEMBER OFFSET is used forces corresponding to the beam the length of which is equal to the distance between points a and b are calculated and then used in calculation of reinforcement. In such case it is necessary to take into account default values of parameters SFA and ЕFA equal to zero. When command MEMBER OFFSET is not used forces corresponding to the beam the length of which is equal to the distance between points 10 and 11 are calculated and then used in calculation of reinforcement. In this case it is necessary to consider values of parameters SFA=0.3 and ЕFA=0,2 in reinforcement calculation. In both cases calculated quantity of transverse reinforcement will be the same. Calculated quantity of longitudinal reinforcement in the second case will be greater. For beam the following output is generated:  beam number;  method of calculation (according to conditions of strength or limitations of opened crack width);  length and cross-sectional dimensions;  distance from resultant of forces acting in bottom/top reinforcement to bottom/top edge of the section;

Section 12A

 distance from the side edge of cross-section of the beam web to the centroid of longitudinal bars located at this edge;  concrete class;  class of longitudinal and transverse reinforcement;  assumed in calculations bar diameters of longitudinal and transverse reinforcement;  calculation results of longitudinal and transverse reinforcement (in two tables). In nine columns of the first table the following results are presented: Section As 

As 

Moments ( /  )

Load. N. ( /  ) Acrc1 Acrc2

distance of the section from the “start” of the beam, мм cross-sectional area of longitudinal reinforcement in the bottom zone of crosssection of the beam, if angle BETA=0 , or in the top zone, if BETA=180 , sq.cm cross-sectional area of longitudinal reinforcement in the top zone of cross-section of the beam , if angle BETA=0 , or in the top zone, if BETA=180 , sq.cm values of bending moments, determining crosssectional areas of longitudinal reinforcement As  and As  , kNm numbers of loading versions, determining crosssectional areas of longitudinal reinforcement short-term opened crack width*, mm long-term opened crack width*, mm

* Opened crack width is presented only in the case when calculation is performed according to conditions limiting opened crack width.

12-13


12-14

Section 12A

In ten columns of second table the following results are presented: Section Qsw Asw Q T Load N.

distance of the section from the “start” of the beam, mm intensity of transverse reinforcement, kN/m cross-sectional area of transverse bars, sq.cm, if their step is 10, 15, 20, 25 or 30 cm value of shear force parallel to the local axis, kN value of torsional moment, kNm number of loading version, determining intensity of transverse reinforcement

An example of output of calculation results is presented below. BEAM NO. 23 DESIGN RESULTS (by limitation of crack width) Length  6000 mm. Section: BF1= 550 mm, B= 200 mm, HF1=220 mm, H=450 mm. Distance from top/bottom surface of beam to center of longitudinal reinforcement  40 mm. Distance from side surface of beam to center of longitudinal reinforcement  30 mm. Concrete class  В25.0 (Rb=13.05 MPa; Rbt=0.94 MPa; Gb2=0.9). Class of longitudinal reinforcement  А  III (Rs=365.0 MPa; Rsc=365.0 MPa). Diameter of longitudinal reinforcement bars D=16 mm. Class of shear reinforcement  А I (Rsw=175.0 MPa). Diameter of shear reinforcement bars Dw=10 mm.

Section 12A

12-15

LONGITUDINAL REINFORCEMENT Section mm

As- As+ Moments( -/+) sq.cm 10.92

0.41

4.74

0.41

1.13

 152.

Acrc1

Acrc2

mm

mm

/

2.

6

/

4

0.237

0.121

 60.

/

0.

5

/

0

0.294

0.157

1.13

 5.

/

17.

4

/

6

0.000

0.000

1.13

6.41

 8.

/

75.

4

/

6

0.295

0.147

1.13

9.24

 11.

/

115.

4

/

6

0.298

0.149

1.13

11.53

 14.

/

139.

4

/

6

0.271

0.134

1.19

12.16

 18.

/

144.

4

/

6

0.263

0.127

1.41

10.86

 21.

/

132.

4

/

6

0.277

0.130

1.63

8.28

 24.

/

103.

4

/

6

0.296

0.129

1.95

4.54

 27.

/

56.

4

/

6

0.299

0.093

3.23

0.58

 39.

/

9.

5

/

3

0.293

0.157

0.74

0.41

 124.

/

0.

5

/

0

0.271

0.142

16.89

0.41

 226.

/

0.

5

/

0

0.155

0.078

0. 500. 1000. 1500. 2000. 2500. 3000. 3500. 4000. 4500. 5000. 5500. 6000.

Load.N.(-/+ )

kNm


12-16

Section 12A

SHEAR REINFORCEMENT Section mm

Qsw kN/m

10cm

Asw, cm^2, if Sw= 15cm 20cm 25cm

30cm

Q kN

T kNm

Load N.

0.0

6

0.0

6

0.0

6

0.0

6

0.0

6

2000.

Minimu m detailing requirements !

2500.


 203.9  168.9  133.9  98.9  63.9  28.9

0.0

6

3000.


12.7

0.0

5

3500.


47.7

0.0

5

0.

251.3

1.44

2.15

2.87

3.59

4.31

500.

251.3

1.44

2.15

2.87

3.59

4.31

1000.

174.5

1.00

1.50

1.99

2.49

2.99

1500.

63.9

0.36

0.55

0.73

0.91

1.09

4000.

82.7

0.0

5

4500.

95.0

Minimu m detailing requirements ! 0.55

0.82

1.09

1.37

1.64

117.7

0.0

5

5000.

242.5

1.39

2.08

2.77

3.46

4.16

152.7

0.0

5

5500.

302.5

1.73

2.59

3.46

4.32

5.19

187.7

0.0

5

6000.

302.5

1.73

2.59

3.46

4.32

5.19

216.1

0.0

5

Here Minimum detailing requirements! means that reinforcement is not required according to calculation.

122A.4 Columns Reinforcement for columns of rectangular or circular cross -section can be calculated. Flexibility of columns can be evaluated in two ways. In the case of usual analysis (command PERFORM ANALYSIS) flexibility is assessed by parameters ELY and ELZ, values of which should conform with recommendation of the Code SNiP 2.03.01  84*. If P  DELTA (analysis according to deformed diagram) or NONLINEAR (nonlinear geometry) analysis is performed, values of parameters ELY and ELZ should be close to zero, for example ELY = ELZ=0.01. Longitudinal reinforcement for columns is calculated only from condition of strength. Longitudinal forces and bending moments in

Section 12A

relation to local axes Yloc and Z loc are taken into account in longitudinal reinforcement calculations. For rectangular columns the following output is generated:  column number;  column length and cross-sectional dimensions;  distance of centroid of each longitudinal bar from the nearest edge of the cross-section;  concrete class;  longitudinal reinforcement class;  range of longitudinal reinforcement bar diameters assumed in calculation;  diameter of longitudinal reinforcement bars obtained in calculation;  total quantity of longitudinal bars;  quantity of longitudinal bars at each cross-section edge, directed parallel to the local axis Yloc ;  quantity of longitudinal bars at each cross-section edge, directed parallel to the local axis Z loc . In nine columns of the table under the heading LONGITUDINAL REINFORCEMENT the following output is presented: Section Astot Asy

distance of the section from the “start” of the column, mm total cross-sectional area of longitudinal reinforcement, sq.cm cross-sectional area of longitudinal reinforcement bars at each edge of section, directed parallel to the local axis Yloc , sq.cm

Asz

cross-sectional area of longitudinal reinforcement bars at each edge of section, directed parallel to the local axis Z loc , sq.cm

Percent Nx, Mz, My

reinforcement percentage in the section respective values of longitudinal force and bending moments in relation to the local axes Z loc and Yloc , determining cross-sectional area

12-17


12-18

Section 12A

of longitudinal reinforcement number of loading version, determining crosssectional area of longitudinal reinforcement

Load.N.

An example of output of calculation results is presented below. COLUMN NO. 97 DESIGN RESULTS (rectangular section) Length  4000 mm. Section: B= 350 mm, H=350 mm. Distance from edge of column cross section to center of each longitudinal reinforcement bar  40 mm. Concrete class  В25.0 (Rb=13.05 МPa; Gb2=0.9). Class of longitudinal reinforcement  А  III (Rs=365.0 МPa; Rsc=365.0 МPa). Diameter range of longitudinal reinforcement bars: Dmin=16 mm . . . Dmax=32 mm Diameter of longitudinal reinforcement bars from calculation d=20 mm. Total number of reinforcement bars Ntot=6. Number of longitudinal bars at each section edge parallel to the local Y axis Nyy =2. Number of longitudinal bars at each section edge parallel to t he local Z axis Nzz =3. LONGITUDINAL REINFORCEMENT Section m

Astot

Asy

sq.cm sq.cm

Asz

Per cent

Nx

Mz

My

sq.cm

%

kN

kNm

kN m

Load N.

0.

16.42

3.01

6.20

1.34

285.5

81.9

0.0

6

4000.

15.35

3.01

5.67

1.25

397.3

95.3

0.0

5

Section 12A

Diameter of longitudinal reinforcement bars, total quantity of longitudinal bars as well as quantity of longitudinal bars at each edge of the section obtained from calculation should be considered as recommendation. In this case arrangement of reinforcement in the section depends on the orientation of the local axes and is as follows:

or

Calculated values of reinforcement cross-sectional areas are presented in the table and they may differ from recommended on the lower side. When it is not possible according to detailing provisions to arrange in the column longitudinal reinforcement determined from calculation additional message is derived. For columns of circular section the following output is generated:  column number;  column length and diameter of cross-section;  distance of centroid of each longitudinal bar to the edge of cross-section;  longitudinal reinforcement class;  assumed in calculation range of diameters of longitudinal reinforcement bars;  diameter of longitudinal reinforcement bars obtained from calculation;  quantity of longitudinal bars.

12-19


12-20

Section 12A

In seven columns of the table under the heading LONGITUDINAL REINFORCEMENT the following results are presented: Section Astot Per cent Nx, Mz, My

distance of the section from the “start” of the column, mm total cross-sectional area of longitudinal reinforcement, sq.cm percentage of longitudinal reinforcement respective values of longitudinal force and bending moments in relation to local axis Z loc and

Load. N.

Yloc ,

determining cross-sectional area of

longitudinal reinforcement number of loading version, determining crosssectional area of longitudinal reinforcement

An example of output of calculation results for a column of circular section is presented below. COLUMN NO. 80 DESIGN RESULTS (circular section) Length  4000 mm. Diameter: Dс= 350 mm. Distance from edge of column cross section to center of each longitudinal reinforcement bar  50 mm. Concrete class  В20.0 (Rb=10.35 МPa; Gb2=0.9). Class of longitudinal reinforcement  А  III (Rs=365.0 МPa; Rsc=365.0 МPa). Diameter range of longitudinal reinforcement bars: Dmin=16 mm . . . Dmax=32 mm Diameter of longitudinal reinforcemen t bars from calculation D=20 mm. Total number of reinforcement bars Ntot =7.

Section 12A

12-21

LONGITUDINAL REINFORCEMENT Section mm

0. 4000.

Astot sq.cm

Per cent %

Nx kN

17.96 21.86

1.87 2.27

195.1 195.1

Mz kNm

59.8 80.2

My k Nm

0.0 0.0

Load. N.

5 5

Diameter of longitudinal reinforcement bars, total quantity of longitudinal bars as well as quantity of longitudinal bars at each edge of the section should be considered as recommendation. Arrangement of reinforcement in section in this case is shown below:

Calculated cross-sectional areas of reinforcement presented in the table may differ from recommended on the lower side. When according to detailing provisions it is not possible to arrange in the column longitudinal reinforcement obtained from calculation additional message is derived.

12A.5 2D (two dimensional) element (slabs, walls, shells) In general case calculation of reinforcement for 2D members is carried out two times – according to conditions of strength and conditions of limiting opened width of cracks. If reinforcement is calculated according to conditions of strength, design values of loads have to be used, and for conditions of limiting crack width – characteristic (normative) loads are employed. Both calculations can be made in one session taking advantage of multiple analysis possibility of the program STAAD.Pro.


12-22

Section 12A

Symmetric or nonsymmetric reinforcement of 2D members is calculated according to conditions of strength or according to conditions of limiting opened crack width (see for example STA). In reinforcement calculation for 2D members it is necessary to pa y attention to arrangement of local axes of member and direction of reinforcement (see for example CL and CRA).

An example of output of calculation results is presented bellow.

SLAB/WALL DESIGN RESULTS (by stresses in local axes for limitation of cra ck width)

Element

Asx sq.cm/m

60 TOP

0.00

BOT

3.53

61 TOP BOT

Mx Nx kNm/m kN/m

- 4.9

Load. N. Asy (X) sq.cm/m

My Ny Load N. kNm/m kN/m (Y)

0.0

1

0.00

- 4.5

0.0

1

- 9 .9

0.0

3

3.46

- 8.9

0.0

3

0.00

- 5 .3

0.0

1

0.00

- 4.7

0.0

1

3.87

- 10.7

0.0

3

3.65

- 9.4

0.0

3

62 TOP

0.00

- 5 .6

0.0

1

0.00

- 4.8

0.0

1

BOT

4.10

- 11.2

0.0

3

3.77

- 9.6

0.0

3

Section 12A

12-23

Here: Element

number of finite element, TOP  “top” zone of member, BOT  “bottom” zone of member (“top” zone of member is determined by positive direction of local axis Z loc  see Fig.2)

Asx

intensity of reinforcing in the first direction (parallel to the local axis X loc ), sq.cm/m

Mx

distributed bending moment in respect to the local axis Yloc , kNm/m

Nx

distributed longitudinal force directed parallel to the axis X loc , kNm/m

Load N.(X)

number of loading version, determining intensity of reinforcing in the first direction intensity of reinforcing in the second direction (parallel to the local axis Yloc ), sq.cm/m

Asy My

distributed bending moment in respect to the local axis X loc kNm/m

Ny

distributed longitudinal force directed parallel to the local axis Yloc kN/m

Load N.(Y)

number of loading version, determining intensity of reinforcing in the second direction


12-24

Section 12A

Figure 2 - Local coordinate system of 2D member and notation of forces

12-25

Steel Design Per Russian Code SNIP 2.23-81* (Edition 1990) Section

12B

12B.1 General Design Code SNiP “Steel Structures” as majority of modern codes is based on the method of limit states. The following groups of limit states are defined in the Code. 



The first group is concerned with losses of g eneral shape and stability, failure, qualitative changes in configuration of structure. Appearance of non -allowable residual deformations, displacements, yielding of materials or opening of cracks. The second group is concerned with states of structures making worse normal their service or reducing durability due to not allowable deflections, deviations, settlements, vibrations, etc.

Analysis of structures for the first limit state is performed using the maximum (design) loads and actions, which can cause failure of structures. Analysis of structures for the second limit state is performed using service (normative) loads and actions. Relation between design and normative loads is referred to as coefficient of load reliability, which is defined in SNiP 2.01.07.- 85 “Loads and Actions”. Coefficient of reliability for destination GAMA n according to SNiP 2.01.07.- 85 shall be taken in to account determining loads or their combinations.

Steel Design Per Russian Code

12-26

Section 12B

In this version of the program only members from rolled, tube and roll-formed assortment sections and also from compound such as double angles of T-type sections, double channels are presented. Design of other members of compound section will be presented in other versions of the program. Economy of selected section is indicat ed by ratio (RATIO)  /R yy c presented in calculation results. A section is economical when said ratio equals to 0,9 – 0,95.

12B.2 Axial tension members Stress in a section of axial tension member shall not exceed design strength R y of selected steel multiplied by coefficient of service conditions  c (KY and KZ), table 6 of SNiP 2.01.07. - 81*. Slenderness of tension member (CMM) shall not exceed slenderness limit indicated in table 20 of SNiP 2.01.07. - 81* (default value  u =200, but another value can be defined). Net section factor (ratio A net /A gross (NSF)) is used for tension member to allow for reduction of design cross-section area.

12B.3 Axial compression members All axial compression members are calculated as long bars, i.e., with allowance for slenderness (=l 0 /i min ). Calculation is performed in accordance with the clause 5.3 of SNiP 2.01.07. 81*, buckling coefficient  is determined by formula 8-10. Effective bar lengths (within and out of plane) taking in to account role and location of the bar in the structure, as well as fixation of ends (l 0 =l), are determined according to requirements of chapter 6 or addition 6 to SNiP 2.01.07.- 81* and are set by specification of members. Slenderness of compression members (CMN) shall not exceed limit values given in table 19 of SNiP 2.01.07.- 81*. Value of coefficient  being used in table 19 is taken within limits from 0,5 to 1,0. Limit slenderness value depends on stress acting in the member, section area, buckling coefficient and design resistance of steel.

Section 12B

Since slenderness can be different in various planes the greatest slenderness is assumed in calculations.

12B.4 Flexural members Members subjected to the action of bending moments and shear forces are called flexural members. Calculation of flexural members consists of verification of strength, stability and deflection. Normal and tangential stresses are verified by strength calculation of members. Normal stresses are calculated in the outermost section fibres. Tangential stresses are verified in the neutral axis zone of the same section. If normal stresses do not exceed design steel strength and tangential stresses do not exceed design value of steel shear strength R s  s then according to clause 5.14 of SNiP 2.01.07.- 81* principal stresses are checked. General stability of member subjected to bending in one plane are calculated in accordance with clause 5.15 of SNiP 2.01.07. - 81*, and subjected to bending in two planes – in accordance with “Guide to design of steel structures” (to SNiP 2.01.07. - 81*). Coefficient  b value is determined according to appendix 7 of SNiP 2.01.07.- 81*. Additional data about load (concentrated or distributed), numbers of bracing restrains of compression flanges, location of applied load are required. For closed sections it is assumed that coefficient  b =1,0. Simply supported (non-continuous) beams can be calculated in elastic as well as in elastic-plastic state according to requirements of clause 5.18 of SNiP 2.01.07.- 81*. Calculation can be selected by specification of structure in input data.

12-27


12-28

Section 12B

Stiffness of flexural members is verified comparing input value of deflection limit (through parameter DFF) with maximum displacement of a section of flexural member allowing for load reliability coefficient, which is specified, in input data. Limit values of deflection are determined in accordance with S NiP 2.01.07.- 85 “Loads and Actions. Addition chapter 10. Deflections and displacements”. Verification of deflection is performed only in the case of review (CHECK) problem.

12B.5 Eccentrical compression/tension members Eccentrical compression or tension members are subjected to simultaneous action of axial force and bending moment. Bending moment appears due to eccentrical application of longitudinal force or due to transverse force. Stress in eccentrical compression/tension members is obtained as a sum of stresses due to axial force and bending. Following the requirements of clause 5.25 of SNiP 2.01.07.- 81* resistance of eccentrical compression/tension member taking into consideration condition R y <530 MPa, <0,5Rs and N/(A n Ry )>0,1 is calculated by formula 49, and in other cases-by formula 50. Calculations of stability verification are performed according to requirements of clauses 5.27, 5.30, 5.32 or 5.34. Calculation for strength of eccentrical tension members is made according to formula 50 of SNiP 2.01.07.- 81*. When reduced relative eccentricity m ef>20 eccentrical compression members are calculated as flexural members (N=0), when m ef<20 strength by formula 49 is not verified (clause 5.24).

Section 12B

12-29

12B.6 Input Data Program STAAD/Pro gives opportunity to verify sections of steel structures by codes of many countries including and Russian Code SNiP 2.01.07.- 81*. Algorithms for selection and review of sections for steel members according to assortments and databases of the main rolled steel producers from given countries and according to international standards as well are included in STAAD/Pro program. In this program version only assortment sections can be utilized. Typical sections of members being checked and selected according to SNiP 2.01.07.- 81* are presented in tables 1 and 2.

Table 1. No . 1

Typical sections Section

I-beam (GOST 8239-89)

Section type

Designation form ST I12

2

Regular I-beam (GOST 2602083)

ST B1-10

3

Broad-flanged I-beam (GOST 26020-83)

ST SH1-23

4

Column I-beam (GOST 2602083)

ST K1-20

5

Channel (GOST 8240-89)

ST C14


12-30

Section 12B

Table 1.

Typical sections

No .

Section

6

Equal legs angle (GOST 850989)

7

Unequal legs 8510-89)

angle

Section type

(GOST

8

Pipes (welded and for gas piping)

9

Roll-formed square and rectangular tubes

Designation form

ST L100x100x7 RA L100x100x7

ST L125x80x10 RA L125x80x10

ST PIP102x5.5 or ST PIPE OD 0.102 ID 0.055 ST TUB160x120x3 or ST TUBE TH 0.003 WT 0.12 DT 0.16

Section 12B

Table 2. No .

1

12-31

Compound sections Section

Double channels

Section type

Designation form

D C14 SP 0.01 (SP – clear distance between channel walls)

2

Double equal legs angles

LD L100x100x7 SP 0.01 (SP – clear distance between angle walls)

5

Double unequal legs angles with long legs back to back

LD L125x80x10 SP 0.01 (SP – clear distance between angle walls)

6

Double unequal legs angles with short legs back to back

SD L125x80x10 SP 0.01 (SP – clear distance between angle walls)

7

Tee with flange at the top

T I12 T B1-10 T SH1-23 T K1-20

Flange of Tee beams is at the top part of cross-section if angle BETA = 0, or at the bottom part if BETA = 180. For entry of cross-sectional dimensions command MEMBER PROPERTIES RUSSIAN is used.


12-32

Section 12B

Example UNITS METER MEMBER PROPERTY RUSSIAN * I-beam 1 TO 6 TABLE ST B1-10 * Channel 7 TO 11 TABLE ST C14 * Unequal legs angle 12 TO 30 TABLE RA L125x80x10 * Round assortment pipe 31 TO 46 TABLE ST PIP102x5.5 * Round pipe of cross-sectional dimensions defined by client 47 TO 60 TABLE ST PIPE OD 0.102 ID 0.055 * Square tube from assortment 61 TO 68 TABLE ST TUB120x120x3 * Rectangular tube of cross-sectional dimension defined by client 69 TO 95 TABLE ST TUBE TH 0.003 WT 0.12 DT 0.16 * Double channel (distance between walls 10 мм) 96 TO 103 TABLE D C14 SP 0.01 * Double unequal legs angles with short legs back to back (distance between walls 10 мм) 104 TO 105 TABLE SD L125x80x10 SP 0.01 * Member of Tee section 106 TO 126 TABLE T SH1-23 * Flange of T-beams at the bottom of cross-section BETA 180. MEMB 116 TO 126 * Orientation of the local angle axes in relation to the global axes of the structure BETA RANGLE MEMB 12 TO 30 Commands of output data for check and selection of sections are located after commands of analysis and, as a rule, after output command to print results of calculation.

Section 12B

Example * Command of analysis PERFORM ANALYSIS * Command of loadings and their combinations considered in design LOAD LIST 1 5 TO 9 * Command to start design according to Russian Code PARAMETER CODE RUSSIAN * List of parameters used in checking and selecting . BEAM 1. ALL (obligatory parameter) . LY 4. MEMB 1 TO 4 LZ 4. MEM 1 TO 4 MAIN 1. ALL SGR 3. ALL SBLT 0 ALL * Parameter of output amount of information on calculation results TRACK 2. ALL . * Command to start section check proced ure CHECK CODE ALL * Command to start section selection procedure SELECT ALL . * Command of output to print content of assortment tables PRINT ENTIRE TABLE * Command of output to print summary of steel according to sections STEEL TAKE OFF * Command of output to print summary of steel according to members and sections STEEL MEMBER TAKE OFF

12-33


12-34

Section 12B

Information on parameters, data used for check and selection of sections in design of steel structures according to Russian Code is presented in table 3. In this version of calculation according to requirements of SNiP 2.01.07.- 81* there is common database of equal legs angles and unequal legs angles, therefore solution of section selection problem may give equal legs angle as well as unequal legs angle irrespective of set at the beginning. The same is and with rectangular and square tubes. Values of parameters do not depend on command UNIT. Only these values of parameters, which differ from, defined in the program need to be included in the input data file. Review of sections (command CHECK) can be performed according to the first and the second group of limit states. Selection of section (command SELECT) can be performed only according to the first group of limit states with subsequent recalculation and verification of selected section with allowance for deflection. Calculation for the first group of limit states involves selection of members according to strength and stability. Parameters CMN and CMM give opportunity to set slenderness limit for compression and tension members respectively for their stability calculation, or refuse consideration of slenderness by setting default parameters. In this case selection of sections will be performed with consideration only of strength check. Check for deflection performed by setting parameter DFF (maximum allowable relative deflection value) different from set in the program. In the case of application of steel not defined by SNiP and/or GOST it is necessary to set their design strength by parameters UNL and PY.

Section 12B

12-35

In determination of steel parameters SBLT and MAIN shall be approved (see table 4). Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

Table 3. Names of parameters for Steel design according to Russian Code (SNiP II – 23 – 81*, edition 1990) No.

Parameter name

1

KY

2

KZ

3

LY [m]

4

LZ [m]

5

SBLT

6

NSF

Description Coefficient of effective length in respect to local axis Y (in plane XZ) Coefficient of effective length in respect to local axis Z (in plane XY) Effective length in respect to local axis Y (in plane XZ) Default is selected member's length Effective length in respect to local axis Z (in plane XY) Default is selected member's length Number of lateral bracing restraints along the span:  SBLT = 0, if beam not fixed;  SBLT = 1, one restraint in the middle of the span;  SBLT = 2, 3, etc. number of uniformly spaced lateral supports along the span Net section factor for tension members or web section area weakening factor for bending members

Default value 1.0

1.0

Member length

Member length

0

1.0


12-36

Section 12B


Parameter name

7

MAIN

8

DFF

Description Standard of steel grade (GOST):  MAIN = 1, if Standard of steel grade is GOST27772-88;  MAIN = 2, if Standard of steel grade is GOST10705-80;  MAIN = 3, if Standard of steel grade is GOST10706-76;  MAIN = 4, if Standard of steel grade is GOST873187;  MAIN = 5, if Standard of steel grade is TY14-3-56776 Allowable limit of relative local deflection (Member length/Deflection Ratio): Default value 0 is valid if design is applied without deflection limitation. Set for deflection check only

Default value

1

0.

Section 12B


9

Parameter name

SGR

Description Steel grade (STAL):  SGR = 1, if Steel grade is C235;  SGR = 2, if Steel grade is C245;  SGR = 3, if Steel grade is C255;  SGR = 4, if Steel grade is C275;  SGR = 5, if Steel grade is C285;  SGR = 6, if Steel grade is C345;  SGR = 7, if Steel grade is C345K;  SGR = 8, if Steel grade is C375;  SGR = 9, if Steel grade is C390;  SGR = 10, if Steel grade is C390K;  SGR = 11, if Steel grade is C440;  SGR = 12, if Steel grade is C590;  SGR = 13, if Steel grade is C590K;  SGR = 14, if Steel grade is BCT3KP;  SGR = 15, if Steel grade is BCT3PC;  SGR = 16, if Steel grade is BCT3CP;  SGR = 17, if Steel grade is 20;

Default value

1

12-37


12-38

Section 12B


Parameter name

Description 

10

СMM

Default value

SGR = 18, if Steel grade is 16G2AF

Slenderness limit value for tension members:  СMM = 0, if slenderness is suppressed;  СMM = 2, if ultimate slenderness value is "150";  СMM = 2, if ultimate slenderness value is "200";  СMM = 3, if ultimate

0

Section 12B


11

Parameter name

CMN

Description slenderness value is "250";  СMM = 4, if ultimate slenderness value is "300";  СMM = 5, if ultimate slenderness value is "350";  СMM = 6, if ultimate slenderness value is "400 Set slenderness limit value not equal to "0" for design with evaluation of buckling effect Slenderness limit value for compression members:  СMN = 0, if slenderness is suppressed;  СMN = 1, if slenderness limit value is "120";  СMN = 2, if slenderness limit value is "21060a";  СMN = 3, if slenderness limit value is "22040a";  СMN = 4, if slenderness limit

Default value

0

12-39


12-40

Section 12B


Parameter name

Description value is "220"; СMN = 5, if slenderness limit value is "18060a";  СMN = 6, if slenderness limit value is "21060a";  СMN = 7, if slenderness limit value is "21060a";  СMN = 8, if slenderness limit value is "200";  СMN = 9, if slenderness limit value is "150"; Set slenderness limit value not equal to "0" for design with evaluation of buckling effect Type and position of loading on beam:  LEG = 1, for loading concentrated in the middle span;  LEG = 2, for loading concentrated in the quarter of the span;  LEG = 3, for loading concentrated at the end of bracket;  LEG = 4, for loading uniformly distributed on

Default value



12

LEG

4

Section 12B


Parameter name

Description 

13

CB

14

TRACK

15

TB

16

RATIO

Default value

beam; LEG = 5, for loading uniformly distributed on bracket

Place of loading on beam:  CB = 1, for loading on top flange;  CB = 2, for loading on bottom flange Output parameter:  TRACK = 0, for suppressed output information;  TRACK = 1, for extended output information;  TRACK = 2, for advanced output information Indication of elastic or elasticplastic calculation:  TB = 0, for elastic calculation  TB = 1, for elastic-plastic calculation Set for members under bending or non-axial compression/tension only. Ratio between design and characteristic loads values

1

0

0

1.0

12-41


12-42

Section 12B


Parameter name

Description

Default value

17

DMAX [m]

Maximum allowable section depth

1.

18

DMIN [m]

Minimum allowable secti on depth

0.

19

BEAM

20

GAMC1

21

GAMC2

22

PY [MPa]

Member design parameter:  BEAM = 0, Design members for forces at their ends or at the sections defined by SECTION command;  BEAM = 1, Calculate the major axis moment Mz at 13 points along the beam and design beam at the location of maximum Mz;  BEAM = 2, Same as BEAM=1, but additional checks are carried out at beam ends and at critical inter mediate section;  BEAM = 3, Calculate forces at 13 points and perform design checks at all locations including the ends Specific service condition coefficient for buckling design Specific service condition coefficient for strength design Design steel strength (yield strength): If parameters MAIN according to Standard of steel grade (GOST)

1

1.0 1.0

0

Section 12B


Parameter name

Description

Default value

and by SGR according to Steel grade (STAL) are not defined

23

UNL [MPa]

Design steel strength (ultimate strength): If parameters MAIN according to Standard of steel grade (GOST) and by SGR according to Steel grade (STAL) are not defined

0

12-43


12-44

Section 12B

Table 4. Steel types for design of steel structures according to SNiP 2.01.07.- 81* (table 51 and 51a) Parameter SGR

Steel

Parameter MAIN

1

C235

1

2

C245

3

GOST

For members * GT, F

1

GOST 27772-88 “

C255

1

“

GT, F

4

C275

1

“

GT, F

5

C285

1

“

GT, F

6

C345

1

“

GT, F

7

C345K

1

“

GT, F

8

C375

1

“

GT, F

9

C390

1

“

F

10

C390K

1

“

F

11

C440

1

“

F

12

C590

1

“

F

13

C590К

1

“

F

14

BSt3kp

2

Tube

15

BSt3ps

2 3

GOST 10705GOST 80* 10705-

80* GOST GOST 16 BSt3sp 107051070680* 76* GOST 17 20 4 GOST 8731-87 TY 14-318 16G2АF 5 10706567-76 76* *GT – members from sheet and roll-formed tubes F – rolled section steel 2 3

GT, F

Tube Tube Tube Tube

Section 12B

12B.7 Section selection and check results Output of selection and check results are given in suppressed, extended and advanced forms. Form of output results depends on value of parameter TRACK. Results are presented in tables. Three versions of output results are possible: suppressed – results according the critical strength condition (TRACK=0), extended - results according to all check conditions (TRACK=1) and advanced – complete information on results of member design (TRACK=2). In tables of results common data for all TRACKs are indicated: (TRACK=2). In tables of results common data for all TRACKs are indicated: number of member; type and number of cross-section; result obtained (ACCEPTED – requirements are met, FAILURE – are not met); abbreviated name of normative document (code, standard) (SNiP); number of check clause; safety of strength (ratio between design and normative values); number of the most unfavorable loading; value of longitudinal force acting in the member with subscript indicating its direction (“C” – compression, “P” – tension); bending moments in relation to local member axes Z and Y; distance to section, in which the most unfavorable combination of forces acts.

12-45


12-46

Section 12B

In suppressed form (TRACK=0) results are presented according to the critical check for given member with indication of S NiP clause number, according to which strength safety of the member is minimum. Example of output with TRACK=0 of calculation results of a member is given below.

ALL UNITS ARE - KN METE ============================================================== MEMBER CROSS RESULT/ CRITICAL COND/ RATIO/ LOADING/ SECTION NO. FX MZ MY LOCATION ============================================================== 1 B1-30 PASS SNiP- 5.12 0.73 2 0.000E+00 -8.750E+01 0.000E+00 4.167E+00

In extended form (TRACK=1) results are presented on the basis of all required by SNiP checks for given stress state. Example of output with TRACK=1 of calculation results of a member is given below.

ALL UNITS ARE - KN METE ============================================================== MEMBER CROSS RESULT/ CRITICAL COND/ RATIO/ SECTION NO. FX MZ MY ==============================================================

*

1

B1-30

1

B1-30

1

B1-30

1

B1-30

1

B1-30

PASS 0.000E+00 PASS 0.000E+00 PASS 0.000E+00 PASS 0.000E+00 FAIL 0.000E+00

SNiP- 5.12 -8.750E+01 SNiP- 5.12 -8.750E+01 SNiP- 5.14 -8.750E+01 SNiP- 5.15 -8.750E+01 SNiP- DISPL -8.750E+01

0.73 0.000E+00 0.06 0.000E+00 0.97 0.000E+00 0.84 0.000E+00 1.59 0.000E+00

LOADING/ LOCATION 2 4.167E+00 2 4.167E+00 2 4.167E+00 2 4.167E+00 2 4.167E+00

Section 12B

In advanced form (TRACK=2) in addition to tabled results supplementary information is presented. Material characteristics: Steel; Design resistance; Elasticity modulus; Section characteristics: Length of member; Section area; Net area; Inertia moment (second moment of area) (I); Section modulus (W); First moment of area (S); Radius of gyration; Effective length; Slenderness; Results are presented in two columns, Z and Y respectively. Design forces: Longitudinal force; Moments; Shear force. Signs “+” and “-“ indicate direction of acting longitudinal force, bending moments and shear forces in accordance with sign rules assumed in program STAAD. Check results in advanced form are presented with values of intermediate parameters by formulas in analytical and numerical expression with indication of SNiP clause. Example of output with TRACK=2 of calculation results of a member is given in the next page.

12-47


12-48

Section 12B

ALL UNITS ARE - KN METE ======================================================================== MEMBER CROSS RESULT/ CRITICAL COND/ RATIO/ LOADING/ SECTION NO. FX MZ MY LOCATION ======================================================================== 1 B1-30 PASS SNiP- 5.12 0.73 2 0.000E+00 -8.750E+01 0.000E+00 4.167E+00 1 B1-30 PASS SNiP- 5.12 0.06 2 0.000E+00 -8.750E+01 0.000E+00 4.167E+00 1 B1-30 PASS SNiP- 5.14 0.97 2 0.000E+00 -8.750E+01 0.000E+00 4.167E+00 1 B1-30 PASS SNiP- 5.15 0.84 2 0.000E+00 -8.750E+01 0.000E+00 4.167E+00 * 1 B1-30 FAIL SNiP- DISPL 1.59 2 0.000E+00 -8.750E+01 0.000E+00 4.167E+00 MATERIAL DATA Steel Modulus of elasticity Design Strength (Ry)

= C285 = 206.E+06 KPA = 280.E+03 KPA

SECTION PROPERTIES (units - m) Member Length Gross Area Net Area

= = =

Moment of inertia (I) Section modulus (W) First moment of area (S) Radius of gyration (i) Effective Length Slenderness

: : : : : :

1.00E+01 4.19E-03 4.19E-03 z-axis 633.E-07 428.E-06 240.E-06 123.E-03 100.E-01 0.00E+00

y-axis 390.E-08 557.E-07 415.E-07 305.E-04 333.E-02 0.00E+00

DESIGN DATA (units -kN,m)SNiP II-23-81*/1998 Axial force : 0.00E+00 z-axis y-axis Moments : -875.E-01 0.00E+00 Shear force : 0.00E+00 -150.E-01 CRITICAL CONDITIONS FOR EACH CLAUSE CHECK F.(28) M/Wmin=-875.0E-01/ 4.28E-04= 204.6E+03 F.(29) (QY*SZ)/(IZ*TW)=-150.0E-01* 2.40E-04/ 6.33E-05* 5.80E-03= 980.9E+01 RS*GAMAC= 162.4E+03 F.(33) SQRT(SIGMz**2+3*TAUzy**2)<=1.15*RY*GAMAC -312.5E+03**2+3* 980.9E+01**2<=1.15* 280.0E+03* 100.0E-02 313.0E+03<= 322.0E+03 TAUzy<=RS*GAMAC 980.9E+01<= 162.4E+03 F.(34) M/(FIB*Wmin)=-875.0E-01/ 8.75E-01* 4.28E-04= 234.0E+03 RY*GAMAC= 280.0E+03 ACTUAL SECTION DISPLACEMENT = 6.349E-02 M MAXIMUM MEMBER DEFLECTION = 6.349E-02 M Loading No. 2 ULTIMATE ALLOWABLE DEFLECTION VALUE = 4.000E-02 M

Conventional notations assumed in presentation of results: “+”, “ “, “/”, “*”,”**”, “SQRT”, their respective meanings – addition, subtraction, division, multiplication, raising to the second power (squared) and square root. Conventional notations of stresses, coefficients and characteristics of steel resistance comply with accepted in SNiP, only Greek letters are changed by their names (e.g. ,  с -GAMAC; -ALFA; -BETA, -ETA, -FI, etc.).

Section 13

South African Codes

13-1

Concrete Design Per SABS 0100-1

Section

13A

13A.1 Design Operations STAAD has the capability for performing design of concrete beams and columns according to the South African code SABS 0100-1. The 2000 revision of the code is currently implemented. Design can be performed for beams (flexure, shear and torsion) and columns (axial load + biaxial bending). Given the width and depth (or diameter for circular columns) of a section, STAAD will calculate the required reinforcement.

13A.2 Design Parameters The program contains a number of parameters which are needed to perform and control the design to SABS 0100-1. These parameters not only act as a method to input required data for code calculations but give the engineer control over the actual design process. Default values of commonly used parameters for conventional design practice have been chosen as the basis. Table 12A.1 contains a complete list of available parameters with their default values. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

South African Concrete Code Per SABS 0100-1

13-2

Section 13A

Table 13A.1 – South African Concrete Design-SABS 0100-1 -Parameters Parameter Name FYMAIN

Default

Description

Value *450 N/mm2

Yield Stress for main reinforcement

2

Yield Stress for secondary reinforcement a. Applicable to shear bars in beams

2


FYSEC

*450N/mm

FC

* 30N/mm

MINMAIN

8mm

Minimum main reinforcement bar size Acceptable bar sizes: 6 8 10 12 16 20 25 28 32 36 40 50 60

MINSEC

8mm


MAXMAIN

50mm


CLT

20mm

Clear Cover for outermost top reinforcement

CLB

20mm

Clear Cover reinforcement

CLS

20mm

Clear Cover reinforcement

TRACK

0.0

for for

outermost outermost

bottom side


WIDTH

*ZD


DEPTH

*YD


Section 13A

Table 13A.1 – South African Concrete Design-SABS 0100-1 -Parameters Parameter Name BRACE

Default

Description

Value 0.0

0.0 = Column braced in both directions. 1.0 = Column braced about local Y direction only 2.0 = Column unbraced about local Z direction only 3.0 = Column unbraced in both Y and Z directions

ELY

1.0


ELZ

1.0


* Provided in current unit system

13A.3 Member Dimensions Concrete members that are to be designed by STAAD must have certain section properties input un der the MEMBER PROPERTIES command. The following example demonstrates the required input: UNIT MM MEMBER PROPERTIES *RECTANGULAR COLUMN 300mm WIDE X 450mm DEEP 1 3 TO 7 9 PRISM YD 450. ZD 300. *CIRCULAR COLUMN 300mm diameter 11 13 PR YD 300. * T-SECTION - FLANGE 1000.X 200.(YD-YB) * - STEM 250(THICK) X 350.(DEEP) 14 PRISM YD 550. ZD 1000. YB 350. ZB 250.

13-3


13-4

Section 13A

In the above input, the first set of members are rectangular (450mm depth x 300mm width) and the second set of members, with only depth and no width provided, will be assumed to be circular with 300mm diameter. Note that area (AX) is not provided for these members. If shear area areas (AY & AZ ) are to be considered in analysis, the user may provide them along with YD and ZD. Also note that if moments of inertias are not provided, the program will calculate them from YD and ZD. Finally a T section can be considered by using the third definition above.

13A.4 Beam Design Beam design includes flexure, shear and torsion. For all types of beam action, all active beam loadings are scanned to create moment and shear envelopes and locate the critical sections. The total number of sections considered is thirteen. From the critical moment values, the required positive and negative bar pattern is developed. Design for flexure is carried out as per clause no. 4.3.3.4. Shear design as per SABS 0100 clause 4.3.4 has been followed and the procedure includes computation of critical shear values. From these values, stirrup sizes are calculated with proper spacing. If torsion is present, the program will also consider the provisions of SABS 0100 clause 4.3.5. Torsional reinforcement is separately reported.

Section 13A

A TRACK 2 design output is presented below. B E A M

N O.

4

M20 LENGTH:

D E S I G N

R E S U L T S

Fe450 (Main) 7500.0 mm

SIZE:

380.0 mm X

Fe450 (Sec.) 715.0 mm

COVER: 25.0 mm

DESIGN LOAD SUMMARY (KN MET) -------------------------------------------------------------------SECTION |FLEXURE (Maxm. Sagging/Hogging moments)| SHEAR (in mm) | MZ Load Case MX Load Case | VY P -------------------------------------------------------------------0.0 | 135.75 5 -3.44 5 | 152.06 50.62 | -295.92 4 | 625.0 | 189.16 5 -3.43 5 | 133.95 48.87 | -236.52 4 | 1250.0 | 231.25 5 -3.41 5 | 115.84 47.12 | -188.44 4 | 1875.0 | 262.01 5 -3.40 5 | 97.73 45.37 | -151.68 4 | 2500.0 | 281.46 5 -3.39 5 | 79.61 43.63 | -126.24 4 | 3125.0 | 289.59 5 -3.37 5 | 61.50 41.88 | -112.12 4 | 3750.0 | 286.39 5 -3.36 4 | -62.13 40.13 | -109.32 4 | 4375.0 | 271.88 5 -3.37 4 | -80.25 41.88 | -117.84 4 | 5000.0 | 246.05 5 -3.39 4 | -98.36 43.63 | -137.68 4 | 5625.0 | 208.89 5 -3.40 4 | -116.47 45.37 | -168.84 4 | 6250.0 | 160.42 5 -3.41 4 | -134.58 47.12 | -211.33 4 | 6875.0 | 100.62 5 -3.43 4 | -152.70 48.87 | -265.13 4 | 7500.0 | 29.50 4 -3.44 4 | -170.81 29.63 | -330.25 5 |

Load Case 4 4 4 4 4 4 5 5 5 5 5 5 4

SUMMARY OF REINF. AREA FOR FLEXURE DESIGN (Sq.mm) -------------------------------------------------------------------SECTION | TOP | BOTTOM | STIRRUPS (in mm) | Reqd./Provided reinf. | Reqd./Provided reinf. | (2 legged) -------------------------------------------------------------------0.0 | 1232.70/1256.64( 4-20í )| 543.40/ 565.50( 5-12í )| 8í @ 425 mm 625.0 | 960.90/ 981.74( 2-25í )| 754.32/ 791.70( 7-12í )| 8í @ 510 mm 1250.0 | 751.24/ 791.70( 7-12í )| 937.49/ 942.48( 3-20í )| 8í @ 510 mm 1875.0 | 596.52/ 603.18( 3-16í )| 1075.72/1206.36( 6-16í )| 8í @ 510 mm 2500.0 | 543.40/ 565.50( 5-12í )| 1165.13/1206.36( 6-16í )| 8í @ 510 mm 3125.0 | 543.40/ 565.50( 5-12í )| 1203.00/1206.36( 6-16í )| 8í @ 220 mm 3750.0 | 543.40/ 565.50( 5-12í )| 1188.08/1206.36( 6-16í )| 8í @ 220 mm 4375.0 | 543.40/ 565.50( 5-12í )| 1120.87/1206.36( 6-16í )| 8í @ 220 mm 5000.0 | 543.40/ 565.50( 5-12í )| 1003.50/1005.30( 5-16í )| 8í @ 220 mm 5625.0 | 668.18/ 678.60( 6-12í )| 839.38/ 904.80( 8-12í )| 8í @ 220 mm 6250.0 | 849.99/ 904.80( 8-12í )| 632.84/ 678.60( 6-12í )| 8í @ 220 mm 6875.0 | 1089.94/1206.36( 6-16í )| 543.40/ 565.50( 5-12í )| 8í @ 220 mm 7500.0 | 1397.16/1407.42( 7-16í )| 543.40/ 565.50( 5-12í )| 8í @ 220 mm -------------------------------------------------------------------TORSION REINFORCEMENT: Not required

13-5


13-6

Section 13A

13A.5 Column Design Columns are designed for axial force and biaxial bending at the ends. All active loadings are tested to calculate reinforcement. The loading which produces maximum reinforcement is called the critical load and is displayed. The requirements of SABS 0100 -1 clause 4.7 are followed, with the user having control on the effective length in each direction by using the ELZ and ELY parameters as described in table 12A.1. Bracing conditions are controlled by using the BRACE parameter. The program will then decide whether or not the column is short or slender and whether it requires additional moment calculations. For biaxial bending, the recommendations of 4.7.4.4 of the code are considered. Column design is done for square, rectangular and circular sections. For rectangular and square sections, the reinforcement is always assumed to be arranged symmetrically. This causes slightly conservative results in certain cases. Table 12A.3 shows typical column design results. Using parameter TRACK 1.0, the detailed output below is obtained. TRACK 0.0 would merely give the bar configuration, required steel area and percentage, column size and critical load case.

Section 13A

TABLE 12A.3 -COLUMN DESIGN OUTPUT ======================================================================= C O L U M N

N O.

M20 LENGTH: 3660.0 mm

1

D E S I G N

Fe450 (Main) CROSS SECTION:


R E S U L T S Fe450 (Sec.)

750.0 mm X 460.0 mm COVER:40.0mm

4 END JOINT:

1

SHORT COLUMN


:

915.6


: :

About Z 0.00 18.31

About Y 0.00 18.31

SLENDERNESS RATIOS ADDITION MOMENTS (Maddz and Maddy)

: :

7.96 0.00

4.88 0.00


:

555.13

21.91

REQD. STEEL AREA : 3349.20 Sq.mm. REQD. CONCRETE AREA: 114451.62 Sq.mm. MAIN REINFORCEMENT : Provide 32 - 12 dia. (1.05%, 3619.20 Sq.mm.) (Equally Distributed) TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 140 mm c/c SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET) ---------------------------------------------------------Puz : 2160.42 Muz1 : 570.23 Muy1 : 563.74

13-7


13-8

Section 13A

13-9

Steel Design Per SAB Standard SAB0162–1: 1993 Section

13B

13B.1 General The South African Steel Design facility in STAAD is based on the SAB Standard SAB0162-1: 1993, Limit States Design of Steel Structures. A steel section library consisting of South African Standards shapes is available for member property specification. The design philosophy embodied in this specification is ba sed on the concept of limit state design. Structures are designed and proportioned taking into consideration the limit states at which they would become unfit for their intended use. Two major categories of limit-state are recognized - ultimate and serviceability. The primary considerations in ultimate limit state design are strength and stability, while that in serviceability is deflection. Appropriate load and resistance factors are used so that a uniform reliability is achieved for all steel structures under various loading conditions and at the same time the chances of limits being surpassed are acceptably remote. In the STAAD implementation, members are proportioned to resist the design loads without exceeding the limit states of strength, stability and serviceability. Accordingly, the most economic section is selected on the basis of the least weight criteria as augmented by the designer in specification of allowable member depths, desired section type, or other such parameters. The code checking portion of the program checks whether code requirements for each selected section are met and identifies the governing criteria.

South African Steel Code Per SAB Standard SAB0162–1: 1993

13-10

Section 13B

The following sections describe the salient features of the STAAD implementation of SAB0162-1: 1993. A detailed description of the design process along with its underlying concepts and assumptions is available in the specification document.


13B.3 Member Property Specifications For specification of member properties, the steel section library available in STAAD may be used. The next section describes the syntax of commands used to assign properties from the built -in steel table. Member properties may also be specified using the User Table facility. For more information on these facilities, refe r to the STAAD Technical Reference Manual.

13B.4 Built-in Steel Section Library The following information is provided for use when the built -in steel tables are to be referenced for member property specification. These properties are stored in a database file. If called for, the properties are also used for member design. Since the shear areas are built into these tables, shear deformation is always considered during the analysis of these members.

Section 13B

I Shapes The following example illustrates the specification of I- shapes.

1 TO 15 TABLE ST IPE-AA100 H shapes Designation of H shapes in STAAD is as follows. For example,

18 TO 20 TABLE ST 152X37UC PG shapes Designation of PG shapes in STAAD is as follows.

100 TO 150 TABLE ST 720X200PG Channel Sections (C & MC shapes) C and MC shapes are designated as shown in the following example.

3 TABLE ST 127X64X15C Double Channels Back to back double channels, with or without spacing between them, are specified by preceding the section designation by the letter D. For example, a back to back double channel section PFC140X60 without spacing in between should be specified as:

13-11


13-12

Section 13B

100 TO 150 TABLE D PFC140X60 A back to back double channel section 140X60X16C with spacing 0.01unitlength in between should be specified as:

100 TO 150 TABLE D 140X60X16C SP 0.01 Note that the specification SP after the section designation is used for providing the spacing. The spacing should always be provided in the current length unit. Angles To specify angles, the letter L succeeds the angle name. Thus, a 70X70 angle with a 25mm thickness is designated as 70X70X8L. The following examples illustrate angle specifications.

100 TO 150 TABLE ST 70X70X8L Note that the above specification is for “standard” angles. In this specification, the local z-axis (see Fig. 2.6 in the Technical Reference Manual) corresponds to the Y‟-Y‟ axis shown in the CSA table. Another common practice of specifying angles assumes the local y-axis to correspond to the Y‟-Y‟ axis. To specify angles in accordance with this convention, the reverse angle designation facility has been provided. A reverse angle may be specified by substituting the word ST with the word RA. Refer to the following example for details.

100 TO 150 TABLE RA 45X45X3L The local axis systems for STANDARD and REVERSE angles are shown in Fig. 2.6 of the STAAD Technical Reference manual.

Section 13B

Double Angles To specify double angles, the specification ST should be substituted with LD (for long leg back to back) or SD (short leg back to back). For equal angles, either SD or LD will serve the purpose. Spacing between angles may be provided by using the word SP followed by the value of spacing (in current length unit) after section designation.

100 TO 150 TABLE LD 50X50X3L 3 TABLE LD 40X40X5L SP 0.01 The second example above describes a double angle section consisting of 40X40X5 angles with a spacing of 0.01 length units. Tees Tee sections obtained by cutting W sections may be specified by using the T specification instead of ST before the name of the W shape. For example:

100 TO 150 TABLE T IPE-AA180 will describe a T section cut from a IPE-AA180 section. Rectangular Hollow Sections These sections may be specified in two possible ways. Those sections listed in the SAB tables may be specified as follows.

100 TO 150 TABLE ST TUB60X30X2.5

13-13


13-14

Section 13B

TUB60X30X2.5

Tube symbol

Thickness

Height

Width

In addition, any tube section may be specified by using the DT(for depth), WT(for width), and TH(for thickness) specifications. For example:

100 TO 150 TABLE ST TUBE TH 3 WT 100 DT 50 will describe a tube with a depth of 50mm, width of 100mm. and a wall thickness of 3mm. Note that the values of depth, width and thickness must be provided in current length unit. Circular Hollow Sections Sections listed in the SAB tables may be provided as follows:

100 TO 150 TABLE ST PIP34X3.0CHS PIP34X3.0

Thickness Pipe symbol

Diameter

In addition to sections listed in the SAB tables, circular hollow sections may be specified by using the OD (outside diameter) and ID (inside diameter) specifications.

Section 13B

For example:

100 TO 150 TABLE ST PIPE OD 50 ID 48 will describe a pipe with an outside diameter of 50 length units and inside diameter of 48 length units. Note that the values of outside and inside diameters must be provided in terms of current length unit. Sample input file to demonstrate usage of South African shapes is shown below. STAAD PLANE START JOB INFORMATION ENGINEER DATE 30-Mar-05 END JOB INFORMATION UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 9 0 0; 3 0 6 0; 4 3 6 0; 5 6 6 0; 6 9 6 0; 7 0 10.5 0; 8 9 10.5 0; 9 2.25 10.5 0; 10 6.75 10.5 0; 11 4.5 10.5 0; 12 1.5 11.4 0; 13 7.5 11.4 0; 14 3 12.3 0; 15 6 12.3 0; 16 4.5 13.2 0; MEMBER INCIDENCES 1 1 3; 2 3 7; 3 2 6; 4 6 8; 5 3 4; 6 4 5; 7 5 6; 8 7 12; 9 12 14; 10 14 16; 11 15 16; 12 13 15; 13 8 13; 14 9 12; 15 9 14; 16 11 14; 17 11 15; 18 10 15; 19 10 13; 20 7 9; 21 9 11; 22 10 11; 23 8 10; MEMBER PROPERTY SAFRICAN 1 TABLE ST IPE-AA100 2 TABLE T IPE120 3 TABLE ST 152X23UC 4 TABLE T 152X23UC 5 TABLE ST 812X200PG 6 TABLE T 812X200PG 7 TABLE ST 178X54X15C 8 TABLE D 178X54X15C 9 TABLE D 178X54X15C SP 0.1 10 TABLE ST 25X25X5L 11 TABLE RA 25X25X5L 12 TABLE LD 25X25X5L 13 TABLE SD 25X25X5L 14 TABLE LD 25X25X5L SP 0.1 15 TABLE SD 25X25X5L SP 0.1

13-15


13-16

Section 13B

16 TABLE ST TUB40X2.5SHS 17 TABLE ST TUBE TH 0 WT 0 DT 50 18 TABLE ST TUBE TH 0.02 WT 100 DT 50 20 TABLE ST PIP48X2.0CHS 21 TABLE ST PIPE OD 0.5 ID 0.48 PRINT MEMBER PROPERTIES FINISH

13B.5 Section Classification The SAB specification allows inelastic deformation of section elements. Thus, local buckling becomes an important criterion. Steel sections are classified as plastic (Class 1), compact (Class 2), non compact (Class 3) or slender element (Class 4) sections depending upon their local buckling characteristics (See Clause 11.2 and Table 1 of SAB0162-1:1993). This classification is a function of the geometric properties of the section. The design procedures are different depending on the section class. STAAD determines the section classification for the standard shapes and user specified shapes. Design is performed for sections that fall into the category of Class 1,2 or 3 sections only. Class 4 sections are not designed by STAAD.

13B.6 Member Resistances The member resistances are calculated in STAAD according to the procedures outlined in section 13 of the specification. These depend on several factors such as members‟ unsupported lengths, cross-sectional properties, slenderness factors, unsupported width to thickness ratios and so on. Note that the program automatically takes into consideration appropriate resistance factors to calculate member resistances. Explained here is the procedure adopted in STAAD for calculating the member resistances. All the members are checked against allowable slenderness ratio as per Cl.10.2 of SAB0162-1: 1993.

Section 13B

Axial Tension The criterion governing the capacity of tension members is based on two limit states. The limit state of yielding in the gross section is intended to prevent excessive elongation of the member. The second limit state involves fracture at the section with the minimum effective net area. The net section area may be specified by the user through the use of the parameter NSF (see Table 3B.1). STAAD calculates the tension capacity of a member based on these two limits states per Cl.13.2 of SAB0162-1: 1993. Parameters FYLD, FU and NSF are applicable for these calculations. Axial Compression The compressive resistance of columns is determined based on Clause 13.3 of the code. The equations presented in this section of the code assume that the compressive resistance is a function of the compressive strength of the gross section (Gross section Area times the Yield Strength) as well as the slenderness factor (KL/r ratios). The effective length for the calculation of compression resistance may be provided through the use of the parameters KX, KY, KZ, LX, LY and LZ (see Table 3B.1). Some of the aspects of the axial compression capacity calculations are: 1. For frame members not subjected to any bending, and for truss members, the axial compression capacity in general column flexural buckling is calculated from Cl.13.3.1 using the slenderness ratios for the local Y-Y and Z-Z axis. The parameters KY, LY, KZ and LZ are applicable for this. 2. For single angles, asymmetric or cruciform sections are checked as to whether torsional-flexural buckling is critical. But for KL/r ratio exceeding 50,as torsional flexural buckling is not critical, the axial compression capacities are calculated by using Cl.13.3. The reason for this is that the South African code doesn‟t provide any clear guidelines for calculating this value. The parameters KY, LY, KZ and LZ are applicable for this.

13-17


13-18

Section 13B

3. The axial compression capacity is also calculated by taking flexural-torsional buckling into account. Parameters KX and LX may be used to provide the effective length factor and effective length value for flexural-torsional buckling. Flexuraltorsional buckling capacity is computed for single channels, single angles, Tees and Double angles. 4. While computing the general column flexural buckling capacity of sections with axial compression + bending, the special provisions of 13.8.1(a), 13.8.1(b) and 13.8.1(c) are applied. For example, Lambda = 0 for 13.8.1(a), K=1 for 13.8.1(b), etc.) Bending The laterally unsupported length of the compression flange for the purpose of computing the factored moment resistance is specified in STAAD with the help of the parameter UNL. If UNL is less than one tenth the member length (member length is the distance between the joints of the member), the member is treated as being continuously laterally supported. In this case, the moment resistance is computed from Clause 13.5 of the code. If UNL is greater than or equal to one-tenth the member length, its value is used as the laterally unsupported length. The equations of Clause 13.6 of the code are used to arrive at the momen t of resistance of laterally unsupported members. Some of the aspects of the bending capacity calculations are: 1. The weak axis bending capacity of all sections except single angles is calculated as For Class 1 & 2 sections, Phi*Py*Fy For Class 3 sections, Phi*Sy*Fy Where Phi = Resistance factor = 0.9 Py = Plastic section modulus about the local Y axis Sy = Elastic section modulus about the local Y axis Fy = Yield stress of steel

Section 13B

2. For single angles sections are not designed by STAAD, as the South African code doesn‟t provide any clear guidelines for calculating this value. 3. For calculating the bending capacity about the Z-Z axis of singly symmetric shapes such as Tees and Double angles, SAB0162-1: 1993 stipulates in Clause 13.6(b), page 31, that a rational method. Axial compression and bending The member strength for sections subjected to axial compression and uniaxial or biaxial bending is obtained through the use of interaction equations. In these equations, the additional bending caused by the action of the axial load is accounted for by using amplification factors. Clause 13.8 of the code provides the equations for this purpose. If the summation of the left hand side of these equations exceeds 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the member is considered to have FAILed under the loading condition. Axial tension and bending Members subjected to axial tension and bending are also designed using interaction equations. Clause 13.9 of the code is used to perform these checks. The actual RATIO is determined as the value of the left hand side of the critical equation. Shear The shear resistance of the cross section is determined using the equations of Clause 13.4 of the code. Once this is obtained, the ratio of the shear force acting on the cross section to the shear resistance of the section is calculated. If any of the ratios (for both local Y & Z axes) exceed 1.0 or the allowable value provided using the RATIO parameter (see Table 3B.1), the section is considered to have failed under shear. The code also requires that the slenderness ratio of the web be within a certain limit (See Cl.13.4.1.3, page 29 of SABS 0162-1:1993). Checks for safety in shear are performed only if this value is within the allowable limit.

13-19


13-20

Section 13B

Users may by-pass this limitation by specifying a value of 2.0 for the MAIN parameter.

13B.7 Design Parameters The design parameters outlined in table below may be used to control the design procedure. These parameters communicate design decisions from the engineer to the program and thus allow the engineer to control the design process to suit an application's specific needs. The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements, some or all of these parameter values may be changed to exactly model the physical structure. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

South African steel design parameters Parameter

Default Value

Description

Name Kt

1.0

K value for flexural torsional buckling

Ky

1.0

K value in local Y-axis, usually minor axis

Kz

1.0

K value in local Z-axis, usually major axis

Lt

Member length

Length for flexural torsional buckling

Ly

Member length

Length in local Y axis for slenderness value KL/r

Lz

Member length

Length in local Z axis for slenderness value KL/r

Fyld

300Mpa

Yield strength of steel

Fu

345Mpa

Ultimate strength of steel

NSF

1.0


Section 13B

13-21


Default Value

Description

Member Length

Unsupported length in bending compression of top flange for calculating moment resistance

Member Length

Unsupported length in bending compression of bottom flange for calculating moment resistance

Name UNT

UNB

Flag for controlling slenderness check Main

0

0 - For Check for slenderness. 1 - For Do not check for slenderness

Cb

1.0

Greater than 0.0 and less than 2.5,Value of Omega_2 (C1.13.6) to be used for calculation Equal to 0.0: Calculate Omega_2 Sidesway parameter

Ssy

0

0 - Sideway about local Y-axis. 1 - No sideway about local Y-axis. Sidesway parameter

Ssz

0

0 - Sideway about local Z-axis. 1 - No sideway about local Z-axis.

Cmy

1.0

1 - Do not calculate Omega-1 for local Y axis. 2 - Calculate Omega-1 for local Y axis

Cmz

1.0

1 - Do not calculate Omega-1 for local Z axis. 2 - Calculate Omega-1 for local Z axis Track parameter

Track

0

0 = Print the design output at the minimum detail level. 1 = Print the design output at the


13-22

Section 13B


Default Value

Description

Name intermediate detail level. 2 = Print the design output at maximum detail level Dmax

1000

Dmin

0

Ratio

1.0

Maximum allowable depth Minimum required depth Permissible ratio of applied load to section capacity Used in altering the RHS of critical interaction equations 0 - Perform design at ends and those locations specified in the section command.

Beam

0

Dff

0

Default is 0 indicating that deflection check is not performed

0

Start node of physical member for determining deflected pattern for deflection check and should be set along with DFF parameter

0

End node of physical member for determining deflected pattern for deflection check and should be set along with DFF parameter

Dj1

Dj2

1 - Perform design at ends and 1/12th section locations along member length.

13B.8 Code Checking The purpose of code checking is to determine whether the current section properties of the members are adequate to carry the forces obtained from the most recent analysis. The adequacy is checked as per the SAB0162-1: 1993 requirements.

Section 13B

Code checking is done using forces and moments at specified sections of the members. If the BEAM parameter for a member is set to 1 (which is also its default value), moments are calculated at every twelfth point along the beam. When no section locations are specified and the BEAM parameter is set to zero, design will be based on member start and end forces only. The code checking output labels the members as PASSed or FAILed. In addition, the critical condition, governing load case, location (di stance from the start joint) and magnitudes of the governing forces and moments are also printed. Using the TRACK parameter can control the extent of detail of the output.

PARAMETER CODE SAB0162 MAIN 1 all LY 4 MEMB 1 LZ 4 MEMB 1 UNL 4 MEMB 1 CB 0 MEMB 1 TO 23 CMZ MEMB 2 1 TO 23 CMY MEMB 2 1 TO 23 SSY 0 MEMB 1 TO 23 SSZ 0 MEMB 1 TO 23 FU 450000 MEMB 1 TO 23 BEAM 1 ALL NSF 0.85 ALL KY 1.2 MEMB 3 4 RATIO 1.0 ALL TRACK 2 ALL FYLD 300000 1 TO 23 CHECK CODE ALL FINISH

13-23


13-24

Section 13B

13B.9 Member Selection The member selection process involves determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. Selection of members whose properties are originally provided from a user table will be limited to sections in the user table. Member selection cannot be performed on members listed as PRISMATIC.

13B.10 Tabulated Results of Steel Design Results of code checking and member selection are presented in a tabular format. The term CRITICAL COND refers to the section of the SAB0162-1: 1993 specification, which governed the design. If the TRACK parameter is set to 1.0, the output will be displayed as follows:

************************************** STAAD.PRO CODE CHECKING (SOUTHAFRICAN STEEL/SAB-0162-01(1993)) ************************************** ALL UNITS ARE - KNS

MET


MEMBER

TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= *

1 ST

PFC140X60

(SOUTHAFRICAN SECTIONS) FAIL SAB-13.9 4.321 1 -20.00 0.00 82.53 0.00 |---------------------------------------------------------------------| | FACTORED RESISTANCES FOR MEMBER1 UNIT - KN,M PHI = 0.90 | | MRZ= 14.35 MRY= 3.86 | | CR= 58.41 TR= 425.81 VR= 123.85 | |---------------------------------------------------------------------|

Factored member resistances will be printed out. Following is a description of some of the items printed out. MRZ= Factored moment of resistance in z direction

Section 13B

MRY= Factored moment of resistance in z direction CR = Factored compressive resistance for column TR= Factored tensile capacity VR= Factored shear resistance Further details can be obtained by setting TRACK to 2.0. A typical output of track 2.0 parameter is as follows.

************************************** STAAD.PRO CODE CHECKING (SOUTHAFRICAN STEEL/SAB-0162-01(1993)) ************************************** ALL UNITS ARE - KNS MEMBER

MET


RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= *

TABLE

1 ST

PFC140X60

(SOUTHAFRICAN SECTIONS) SAB-13.9 4.321 0.00 82.53

FAIL -20.00

1 0.00



4.50E+02


FU = 285.4

SECTION CAPACITIES (UNIT - KN,M) --------------------------------CRY = 5.841E+01 CRZ = 2.947E+02 CTORFLX = 2.021E+02 TENSILE CAPACITY = 4.258E+02 COMPRESSIVE CAPACITY = 5.841E+01 FACTORED MOMENT RESISTANCE : MRY = 3.859E+00 MRZ = 1.435E+01 FACTORED SHEAR RESISTANCE : VRY = 1.238E+02 VRZ = 1.168E+02 MISCELLANEOUS INFORMATION -------------------------NET SECTION FACTOR FOR TENSION = 1.000 KL/RY = 239.051 KL/RZ = 80.789 ALLOWABLE KL/R = 300.000 UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 4.500 OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00 SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 3.526E+01 SLENDERNESS RATIO OF WEB (H/W) = 2.00E+01

13-25


13-26

Section 13B

Following is a description of some of the items printed out. CRY

Factored compressive resistance for column buckling about the local y axis

CRZ

Factored compressive resistance for column buckling about the local z axis

CTORFLX

Factored compressive resistance against torsional flexural buckling

TENSILE CAPACITY

Factored tensile capacity

COMPRESSIVE CAPACITY

Factored compressive capacity

FACTORED MOMENT RESISTANCE

MRY = Factored moment of resistance in y direction

FACTORED SHEAR RESISTANCE

VRY = Factored shear resistance in y direction

MRZ = Factored moment of resistance in z direction

VRZ = Factored shear resistance in z direction

13B.11 Verification Problems In the next few pages are included 3 verification examples for reference purposes.

Section 13B

Verification Problem No. 1 Objective: -

To determine the capacity of a South African Isection column in axial compression. Column is braced at its ends for both axes.

Design Code: - South African steel design code (SAB:01621(1993)) Reference: -

Example 4.3.4.1, page 4.18, Structural Steel Design to SAB:0162-1(1993)(Limit state Design) by Greg Parrott, 1st edition, Shades Technical publication

Given: -

FYLD = 300Mpa Length = 6000mm

Comparison: Solution Theory STAAD Difference

Design Strength (kN) 1516 1516 No

13-27


13-28

Section 13B **************************************************** * * * STAAD.Pro * * Version Bld * * Proprietary Program of * * Research Engineers, Intl. * * Date= * * Time= * * * * USER ID: * ****************************************************

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39.

STAAD PLANE START JOB INFORMATION ENGINEER DATE END JOB INFORMATION INPUT WIDTH 79 *********************************************** * STAAD.PRO GENERATED COMMENT * *********************************************** *1 0 0 0,2 0 6 0 *********************************************** UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 0 6 0 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTY SAFRICAN 1 TABLE ST 356X67UB DEFINE MATERIAL START ISOTROPIC MATERIAL1 E 2.0E+008 POISSON 0.3 DENSITY 76.977 ISOTROPIC STEEL E 2.00E+008 POISSON 0.3 DENSITY 76.8195 ALPHA 1.2E-005 DAMP 0.03 END DEFINE MATERIAL UNIT MMS KN CONSTANTS MATERIAL STEEL MEMB 1 UNIT METER KN SUPPORTS 1 FIXED LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 JOINT LOAD 2 FY -1500 PERFORM ANALYSIS P R O B L E M S T A T I S T I C S -----------------------------------

NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 3 DOF TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = SIZE OF STIFFNESS MATRIX = 0 DOUBLE KILO-WORDS REQRD/AVAIL. DISK SPACE = 12.0/ 3978.5 MB 40. 41. 42. 43. 44. 45. 46. 47. 48. 49.

PARAMETER CODE SAB0162 LZ 6 ALL LY 3 ALL FU 450000 ALL BEAM 1 ALL NSF 0.85 ALL TRACK 2 ALL FYLD 300000 ALL CHECK CODE ALL

1 3

Section 13B ************************************** STAAD.PRO CODE CHECKING (SOUTHAFRICAN STEEL/SAB-0162-01(1993)) ************************************** ALL UNITS ARE - KNS MEMBER

MET


TABLE


356X67UB

(SOUTHAFRICAN SECTIONS) SAB-13.8 0.989 0.00 0.00

PASS 1500.00

1 0.00



6.00E+02


FU = 345.0

SECTION CAPACITIES (UNIT - KN,M) --------------------------------CRY = 1.516E+03 CRZ = 2.038E+03 CTORFLX = 1.516E+03 TENSILE CAPACITY = 1.918E+03 COMPRESSIVE CAPACITY = 1.516E+03 FACTORED MOMENT RESISTANCE : MRY = 6.561E+01 MRZ = 1.992E+02 FACTORED SHEAR RESISTANCE : VRY = 5.903E+02 VRZ = 6.461E+02 MISCELLANEOUS INFORMATION -------------------------NET SECTION FACTOR FOR TENSION = 0.850 KL/RY = 75.220 KL/RZ = 39.730 ALLOWABLE KL/R = 200.000 UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 6.000 OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00 SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 0.000E+00 SLENDERNESS RATIO OF WEB (H/W) = 3.65E+01 50. FINISH

13-29


13-30

Section 13B

Verification Problem No. 2 Objective:-

To determine the capacity of a South African I-section beam in bending. The beam has torsional and simple lateral rotational restraint at the supports, and the applied point load provides effective lateral restraint at the point of application is braced at its ends for both axes.

Design Code: - South African steel design code (SAB:01621(1993)) Reference: -

Example 4.5, page 4.37, Structural Steel Design to SAB:0162-1(1993)(Limit state Design) by Greg Parrott, 1st edition, Shades Technical publication

Given: -

FYLD = 300Mpa


Design Strength (kN-m) 353.4 353.3 Small

Section 13B

**************************************************** * * * STAAD.Pro * * Version Bld * * Proprietary Program of * * Research Engineers, Intl. * * Date= * * Time= * * * * USER ID: * **************************************************** 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36.

STAAD PLANE START JOB INFORMATION ENGINEER DATE END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 10 0 0; 3 7 0 0 MEMBER INCIDENCES 1 1 3; 2 3 2 MEMBER PROPERTY SAFRICAN 1 2 TABLE ST 406X67UB DEFINE MATERIAL START ISOTROPIC MATERIAL1 E 2.0E+008 POISSON 0.3 DENSITY 76.977 ISOTROPIC STEEL E 2.00E+008 POISSON 0.3 DENSITY 76.8195 ALPHA 1.2E-005 DAMP 0.03 END DEFINE MATERIAL UNIT MMS KN CONSTANTS MATERIAL STEEL MEMB 1 2 UNIT METER KN SUPPORTS 1 3 PINNED LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 MEMBER LOAD 1 CON GY -104 4 1 UNI GY -26.4 2 UNI GY -7.2 PERFORM ANALYSIS P R O B L E M S T A T I S T I C S -----------------------------------

NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 3/ 2/ ORIGINAL/FINAL BAND-WIDTH= 2/ 2/ 5 DOF TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = SIZE OF STIFFNESS MATRIX = 1 DOUBLE KILO-WORDS REQRD/AVAIL. DISK SPACE = 12.0/ 3978.5 MB 37. 38. 39. 40. 41. 42. 43. 44. 45. 46.

PARAMETER CODE SABS0162 CB 0 ALL UNL 4 MEMB 1 FU 450000 ALL BEAM 1 ALL NSF 0.85 ALL FYLD 300000 ALL TRACK 2 ALL CHECK CODE MEMB 1

2 5

13-31


13-32

Section 13B ************************************** STAAD.PRO CODE CHECKING (SOUTHAFRICAN STEEL/SAB-0162-01(1993)) ************************************** ALL UNITS ARE - KNS MEMBER

MET


TABLE


406X67UB

(SOUTHAFRICAN SECTIONS) SHEAR 0.244 0.00 32.40

PASS 0.00

1 7.00



7.00E+02


FU = 345.0

SECTION CAPACITIES (UNIT - KN,M) --------------------------------CRY = 4.532E+02 CRZ = 2.016E+03 CTORFLX = 4.532E+02 TENSILE CAPACITY = 1.918E+03 COMPRESSIVE CAPACITY = 4.532E+02 FACTORED MOMENT RESISTANCE : MRY = 6.399E+01 MRZ = 3.533E+02 FACTORED SHEAR RESISTANCE : VRY = 6.420E+02 VRZ = 6.075E+02 MISCELLANEOUS INFORMATION -------------------------NET SECTION FACTOR FOR TENSION = 0.850 KL/RY = 175.514 KL/RZ = 41.522 ALLOWABLE KL/R = 300.000 UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 4.000 OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.75 SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = -1.565E+02 SLENDERNESS RATIO OF WEB (H/W) = 4.33E+01 47. FINISH

Section 13B

Verification Problem No. 3 Objective: -

To determine the elastic shear capacity of a South African I-section which is simply supported over the span of 8 m

Design Code: - South African steel design code (SAB:0162-1(1993)) Reference: -

Example 4.6.5, page 4.54, Structural Steel Design to SAB:0162-1(1993)(Limit state Design) by Greg Parrott, 1st edition, Shades Technical publication

Given: -

FYLD = 300Mpa


Design Strength (kN) 687.1 687.1 No

13-33


13-34

Section 13B **************************************************** * * * STAAD.Pro * * Version Bld * * Proprietary Program of * * Research Engineers, Intl. * * Date= * * Time= * * * * USER ID: * **************************************************** 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34.

STAAD PLANE START JOB INFORMATION ENGINEER DATE END JOB INFORMATION INPUT WIDTH 79 UNIT METER KN JOINT COORDINATES 1 0 0 0; 2 8 0 0 MEMBER INCIDENCES 1 1 2 MEMBER PROPERTY SAFRICAN 1 TABLE ST 457X67UB DEFINE MATERIAL START ISOTROPIC MATERIAL1 E 2E+008 POISSON 0.3 DENSITY 76.977 ISOTROPIC STEEL E 2E+008 POISSON 0.3 DENSITY 76.8195 ALPHA 1.2E-005 DAMP 0.03 END DEFINE MATERIAL UNIT MMS KN CONSTANTS MATERIAL STEEL MEMB 1 UNIT METER KN SUPPORTS 1 2 PINNED LOAD 1 LOADTYPE NONE TITLE LOAD CASE 1 MEMBER LOAD 1 UNI GY -70 PERFORM ANALYSIS P R O B L E M S T A T I S T I C S -----------------------------------

NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 2/ 1/ ORIGINAL/FINAL BAND-WIDTH= 1/ 1/ 2 DOF TOTAL PRIMARY LOAD CASES = 1, TOTAL DEGREES OF FREEDOM = SIZE OF STIFFNESS MATRIX = 0 DOUBLE KILO-WORDS REQRD/AVAIL. DISK SPACE = 12.0/ 3978.4 MB 35. 36. 37. 38. 39. 40. 41.

PARAMETER CODE SABS0162 FU 450000 ALL BEAM 1 ALL FYLD 300000 ALL TRACK 2 ALL CHECK CODE ALL

2 2

Section 13B ************************************** STAAD.PRO CODE CHECKING (SOUTHAFRICAN STEEL/SAB-0162-01(1993)) ************************************** ALL UNITS ARE - KNS MET (UNLESS OTHERWISE NOTED) MEMBER

TABLE RESULT/ CRITICAL COND/ RATIO/ LOADING/ FX MY MZ LOCATION ======================================================================= *

1 ST

457X67UB

(SOUTHAFRICAN SECTIONS) CLASS 4 SECT 2.000 0.00 0.00

FAIL 0.00 MEMBER PROPERTIES (UNIT = CM) ----------------------------CROSS SECTION AREA = 8.55E+01 IZ = 2.94E+04 SZ = 1.30E+03 IY = 1.45E+03 SY = 1.53E+02


8.00E+02


FU = 345.0

SECTION CAPACITIES (UNIT - KN,M) --------------------------------CRY = 0.000E+00 CRZ = 0.000E+00 CTORFLX = 0.000E+00 TENSILE CAPACITY = 2.257E+03 COMPRESSIVE CAPACITY = 0.000E+00 FACTORED MOMENT RESISTANCE : MRY = 4.123E+01 MRZ = 0.000E+00 FACTORED SHEAR RESISTANCE : VRY = 6.871E+02 VRZ = 5.730E+02 MISCELLANEOUS INFORMATION -------------------------NET SECTION FACTOR FOR TENSION = 1.000 KL/RY = 194.263 KL/RZ = 43.142 ALLOWABLE KL/R = 200.000 UNSUPPORTED LENGTH OF THE COMPRESSION FLANGE (M) = 8.000 OMEGA-1 (Y-AXIS) = 1.00 OMEGA-1 (Z-AXIS) = 1.00 OMEGA-2 = 1.00 SHEAR FORCE (KNS) : Y AXIS = 0.000E+00 Z AXIS = 2.800E+02 SLENDERNESS RATIO OF WEB (H/W) = 5.04E+01 42. FINISH

13-35


13-36

Section 13B

Section 14

American Aluminum Code

14-1

Design Per American Aluminum Code Section

14

14.1 General STAAD is currently equipped with the facilities to perform design based on the specifications for Aluminum Structures. The requirements of the Allowable Stress Design, Sixth edition, October 1994, have been implemented. The various issues related to the implementation of this code in STAAD are explained below.

14.2 Member Properties In order to do this design in STAAD, the members in th e structure must have their properties specified from Section VI of the above mentioned manual. The section names are mentioned in Tables 5 through 28 of that manual. All of those tables except Table 10 (Wing Channels) and Table 20 (Bulb Angles) are availa ble in STAAD. Described below is the command specification for various sections: Standard single section

memb-list TA ST section-name

Design Per American Aluminum Code

14-2

Section 14

Example 1 TO 5 9 11 33 45 67 18 15 23 25 29

TA ST CS12X11.8 TA ST I8.00X13.1 TA ST LS8.00X8.00X0.625 TA ST 1.50PipeX160 TA ST T(A-N)6.00X8.00X11.2 TA ST 20X12RectX.500Wall

Double channel back-to-back

memb-list TA BACK section-name SPACING value

Example 3 TA BACK C(A-N)7X3.61 SPACING 1.5 5 TA BACK C15X17.33 SP 0.75

Double channel front-to-front

memb-list TA FRONT section-name SPACING value

Example 2 TA FRONT CS12X10.3 SP 1.0 4 TA FR CS10X10.1 SP 0.5

Section 14

Double angle long leg back-to-back

memb-list TA LD section-name SPACING value

Example 14 TA LD LS4.00X3.00X0.375 SP 1.5

Double angle short leg back-to-back

memb-list TA SD section-name SPACING value

Example 12 TA SD L3.5X3X0.5 SP 0.25 13 TA SD L8X6X0.75 SP 1.0

14.3 Design Procedure The design is done according to the rules specified in Sections 4.1, 4.2 and 4.4 on pages I-A-41 and I-A-42 of the Aluminum code. The allowable stresses for the various sections are computed according to the equations shown in Section 3.4.1 through 3.4.21 on pages I-A-27 through I-A-40. The adequacy of the member is checked by calculating the value of the left -hand side of equations 4.1.1-1, 4.1.1-2, 4.1.1-3, 4.1.2-1, 4.4-1 and 4.4-2. This left-hand side value is termed as RATIO. If the highest RATIO among these equations turns out to be less than or equal to 1.0, the member is declared as having PASSed. If it exceeds 1.0, the member has FAILed the design requirements.

14-3


14-4

Section 14

The check for torsion per Clause 4.3 for open sections is currently not done.

14.4 Design Parameters The following are the parameters for specifying the values for variables associated with the design. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 14.1 Aluminum Design Parameters Parameter

Default

Description

Name

Value

ALLOY

34

This variable can take on a value from 1 through 40. The default value represents the alloy 6061-T6. See Table 12A.2 in the following pages for a list of values for this parameter and the alloy they represent. Table 3.3-1 in Section I-B of the Aluminum specifications provides information on the properties of the various alloys.

PRODUCT

1

This variable can take on a value from 1 through 4. They represent: 1 - All 3 - Drawn Tube

2 - Extrusions 4 - Pipe

The default value stands for All. The PRODUCT parameter finds mention in Table 3.3-1 in Section I-B of the Aluminum specifications. ALCLAD

0

This variable can take on a value of either 0 or 1. 0 - Material used in the section is not an Alclad. 1 - Material used in the section is an Alclad.

Section 14

14-5

Table 14.1 Aluminum Design Parameters Parameter

Default

Name

Value

WELD

0

Description In Table 3.4-2 in Section I-A of the Aluminum specifications, it is mentioned that the value of coefficients Kt and Kc are dependent upon whether or not, the location of the section where design is done is within 1.0 inch of a weld. The WELD parameter is used in STAAD for this purpose. The values that can be assigned to this parameter are: 0 - Region is farther than 1.0in from a weld 1 - Region is within 1.0in from a weld

STRUCTURE

1

In Table 3.4-1 in Section I-A of the Aluminum specifications, it is mentioned that the value of coefficients nu, ny and na are dependent upon whether the structure being designed is a building or a bridge. Users may convey this information to STAAD using the parameter STRUCTURE. The values that can be assigned to this parameter are: 1 - Buildings and similar type structures 2 - Bridges and similar type structures

DMAX

1000 in.

Maximum depth permissible for the section during member selection. This value must be provided in the current units.

DMIN

0.0 in

Minimum depth required for the section during member selection. This value must be provided in the current units.

UNL

Member length

Distance between points where the compression flange is braced against buckling or twisting. This value must be provided in the current units. This value is used to compute the allowable stress in bending compression.

KY

1.0

Effective length factor for overall column buckling in the local Y-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.


14-6

Section 14

Table 14.1 Aluminum Design Parameters Parameter Name

Default

Description

Value

LY

Member length

Effective length for overall column buckling in the local Y-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.

KZ

1.0

Effective length factor for overall column buckling in the local Z-axis. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.

LZ

Member length

Effective length for overall column buckling in the local Z-axis. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from buckling) to any user specified large value. It is used to compute the KL/R ratio for determining the allowable stress in axial compression.

KT

1.0

Effective length factor for torsional buckling. It is a fraction and is unit-less. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the allowable stress in axial compression. See Equation 3.4.7.2-6 on page I-A-28 of the Aluminum specifications for details.

LT

Member length

Unbraced length for twisting. It is input in the current units of length. Values can range from 0.01 (for a column completely prevented from torsional buckling) to any user specified large value. It is used to compute the KL/R ratio for twisting for determining the allowable stress in axial compression. See Equation 3.4.7.2-6 on page I-A-28 of the Aluminum specifications for details.

STIFF

Member length

Spacing in the longitudinal direction of shear stiffeners for stiffened flat webs. It is input in the current units of length. See section 3.4.21 on page IA-40 of the Aluminum specifications for information regarding this parameter.

Section 14

14-7

Table 14.1 Aluminum Design Parameters Parameter Name SSY

Default

Description

Value 0.0

Factor that indicates whether or not the structure is subjected to sidesway along the local Y axis of the member. The values are: 0 - Sidesway is present along the local Y-axis of the member 1 - There is no sidesway along the local Y-axis of the member. The sidesway condition is used to determine the value of Cm explained in Section 4.1.1, page I-A-41 of the Aluminum specifications.

SSZ

0.0

Factor that indicates whether or not the structure is subjected to sidesway along the local Z axis of the member. The values are: 0 - Sidesway is present along the local Z-axis of the member 1 - There is no sidesway along the local Z-axis of the member. The sidesway condition is used to determine the value of Cm explained in Section 4.1.1, page I-A-41 of the Aluminum specifications.

TRACK

2

This parameter is used to control the level of detail in which the design output is reported in the output file. The allowable values are: 1 - Prints only the member number, section name, ratio, and PASS/FAIL status. 2 - Prints the design summary in addition to that printed by TRACK 1 3 - Prints the member properties and alloy properties in addition to that printed by TRACK 2. 4 - Prints the values of variables used in design in addition to that printed by TRACK 3.


14-8

Section 14

Table 14.1 Aluminum Design Parameters Parameter

Default

Name

Value

BEAM

0.0

Description If this parameter is set to 1.0, the adequacy of the member is determined by checking a total of 13 equally spaced locations along the length of the member. If the BEAM value is 0.0, the 13 location check is not conducted, and instead, checking is done only at the locations specified by the SECTION command (See STAAD manual for details). If neither the BEAM parameter nor any SECTION command is specified, STAAD will terminate the run and ask the user to provide one of those 2 commands. This rule is not enforced for TRUSS members.

14.5 Code Checking The purpose of code checking is to determine whether the initially specified member properties are adequate to carry the forces transmitted to the member due to the loads on the structure. Code checking is done at the locations specified by either the SECTION command or the BEAM parameter described above. It is done with the aid of the command “CHECK CODE” described in the main STAAD Technical Reference Manual. Example Problem 1 in the Getting Started and Examples Manual for STAAD provides an example on the usage of the CHE CK CODE command.

14.6 Member Selection The member selection process involves the determination of the least weight member that PASSes the code checking procedure based on the forces and moments of the most recent analysis. The section selected will be of the same type as that specified initially. For example, a member specified initially as a channel will have a channel selected for it. It is done with the aid of the command “SELECT MEMBER” described in the main STAAD Technical

Section 14

Reference Manual. Example Problem 1 in the Getting Started and Examples Manual for STAAD provides an example on the usage of the SELECT MEMBER command.

Sample input data for Aluminum Design PARAMETER CODE ALUMIMUM BEAM 1 ALL KY 1.2 MEMB 3 4 ALLOY 35 ALL PRODUCT 2 ALL TRACK 3 ALL SELECT ALL ALCLAD 1 ALL STRUCT 1 ALL CHECK CODE ALL

14-9


14-10

Section 14

Table 14.2 - ALLOY PARAMETER :

Values and Corresponding Names 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

1100-H12 1100-H14 2014-T6 2014-T6510 2014-T6511 2014-T651 3003-H12 3003-H14 3003-H16 3003-H18 3004-H32 3004-H34 3004-H36 3004-H38 5005-H12 5005-H14 5005-H32 5005-H34 5050-H32 5050-H34 5052-H32 5052-H34 5083-H111 5086-H111 5086-H116 5086-H32 5086-H34 5454-H111 5454-H112 5456-H111 5456-H112 6005-T5 6105-T5

Section 14

34 35 36 37 38 39 40

6061-T6 6061-T6510 6061-T6511 6061-T651 6063-T5 6063-T6 6351-T5

14-11


14-12

Section 14

Section 15

American Transmission Tower Code

15-1

Steel Design per ASCE 10-97 Section

15A

15A.1 General Comments The design of structural steel members in accordance with the specifications of ASCE Standard 10-97 – Design of Latticed Steel Transmission Structures is now implemented. This code is meant to supercede the older edition of the code, available under the name ASCE Publication 52. However, in the interests of backward compatibility, both codes are currently accessible in STA AD.Pro. To access the ASCE 52 code, use the commands PARAMETER CODE ASCE 52 To access the ASCE 10-97 code, use the commands PARAMETER CODE ASCE In general, the concepts followed in MEMBER SELECTION and CODE CHECKING procedures are similar to that of t he AISC based design. It is assumed that the user is familiar with the basic concepts of steel design facilities available in STAAD. Please refer to Section 2 of the STAAD Technical Reference Manual for detailed information on this topic. This section specifically addresses the implementation of steel design based on ASCE 10 97. Design is available for all standard sections listed in the AISC ASD 9 th edition manual, namely, Wide Flanges, S, M, HP, Tees, Channels, Single Angles, Double Angles, Tubes and Pipes. Design

Steel Design Per ASCE 10-97

15-2

Section 15A

of HSS sections (those listed in the 3 rd edition AISC LRFD manual) and Composite beams (I shapes with concrete slab on top) is not suppported.

15A.2 Allowable Stresses per ASCE 10 - 97 Member selection and code checking operations in th e STAAD implementation of ASCE 10-97 are done to resist loads at stresses approaching yielding, buckling, fracture and other limiting conditions specified in the standard. Those stresses are referred to in the standard as Design Stresses. The appropriate sections of the ASCE standard where the procedure for calculating the design stresses is explained are as follows. Design Axial Tensile Stress Design tensile stresses are calculated on the basis of the procedure described in section 3.10. The NSF parameter (see the Parameters table shown later in this section) may be used if the section area needs to be reduced to account for bolt holes. Design Axial Compressive Stress Design compressive stress calculation is based on the procedures of section 3.6 through 3.9. For angle members under compression, the procedures of sections 3.7 and 3.8 have been implemented. Capacity of the section is computed for column buckling and wherever applicable, torsional buckling. The user may control the effective lengths for buckling using the LT, LY, LZ and/or KT, KY, KZ parameters (see the Parameters table shown later in this section). Design Bending Compressive Stress Calculations for design bending compressive stress about the major axis and minor axis are based on the procedures of section 3.14. Procedures outlined in sections 3.14.1 through 3.14.6 have been implemented.

Section 15A

Design Bending Tensile Stress Calculations for design bending tensile stress about the major and minor axis are based on the procedures of section 3.14.2. Design Shear Stress Calculation of the design shear stress is based on the procedure outlined in section 3.15 of the ASCE 10-97. The procedure of section 3.15.2 is followed for angles and the procedure of section 3.15.1 is followed for all other sections.

15A.3 Critical Conditions used as criteria to determine Pass/Fail status These are Clause 3.4 for slenderness limits, Clause 3.12 for Axial Compression and Bending, Clause 3.13 for Axial Tension and Bending, Clause 3.9.2 for Maximum w/t ratios and Clause 3.15 for Shear.

15A.4 Design Parameters Design per ASCE (10-97) must be initiated by using the command CODE ASCE. This command should be the first command after the PARAMETER statement. Other applicable parameters are summarized in the table shown later in this section. These parameters may be used to control the design process to suit specific modeling needs. The default parameter values have been selected such that they are frequently used numbers for conventional design.

15A.5 Code Checking and Member Selection Both code checking and member selection options are available in the ASCE 10-97 implementation. For general information on these

15-3


15-4

Section 15A

options, refer to sections 2 and 5 of the STAAD Technical Reference Manual. Table of Steel Design Parameters for ASCE 10-97 Parameter Name

Default Value

Description

KY

1.0

Effective length factor (K) for compression buckling about the Y-axis (minor axis)

KZ

1.0

Effective length factor (K) for compression buckling about the Z-axis (major axis)

KT

1.0

Effective length coefficient for warping restraint (clause 3.14.4, pg 11)

LY

Member Length

Length to calculate slenderness ratio for buckling about the Y-axis (minor axis)

LZ

Member Length

Length to calculate slenderness ratio for buckling about the Z-axis (major axis)

LT

Member Length

Effective length for warping.

FYLD

36.0 KSI

Yield Strength of steel

NSF

1.0

UNL

Member Length

UNF

1.0

Same as UNL, but provided as a fraction of the member length

TRACK

0.0

0.0 = Suppresses printing of allowable stresses 1.0 = Prints all allowable stresses

DMAX

45.0 in.

Maximum allowable depth for member selection

DMIN

0.0 in.

Minimum allowable depth for member selection

RATIO

1.0

Permissible ratio that determines the cut off point for pass/fail status. A value below this quantity indicates PASS while a value greater than this quantity indicates FAILURE.

BEAM

1.0

0.0 = Perform design at beam ends and section locations specified according to the SECTION command 1.0 = Perform design at the ends and eleven intermediate sections of the beam

Net section factor for tension members Unsupported length of member for calculation of allowable bending stress

Section 15A

Table of Steel Design Parameters for ASCE 10-97 Parameter Name MAIN

Default Value 2

Description Parameter that indicates the member type for the purpose of calculating the KL/R ratio (SEE CLAUSE 3.4, PAGE 3, ASCE 10-97) = = = = =

10 : DO NOT PERFORM THE KL/R CHECK 1 : LEG MEMBER KL/R <= 150 2 : COMPRESSION MEMBER KL/R <= 200 3 : TENSION MEMBER KL/R <= 500 4 : HANGAR MEMBERS KL/R <= 375 (Clause 4C.4, page 43) = 5 : REDUNDANT MEMBERS KL/R <= 250 ELA

4

Indicates what type of end conditions are to be used from among Equations 3.7-4 thru 3.7-7 to determine the KL/R ratio. ELA=1 : EQN.3.7-4, Page 4 (VALID FOR LEG MEMBERS ONLY) ELA=2 : EQN.3.7-5, Page 4 ELA=3 : EQN.3.7-6, Page 4 ELA=4 : EQN.3.7-7, Page 5

ELB

1

Indicates what type of end conditions are to be used from among Equations. 3.7-8 thru 3.7-10 and 3.7-12 thru 3.7-14 to determine the KL/R ratio. ELB=1 : EQN.3.7-8, Page 5, EQN.3.7-12, Page 5 ELB=2 : EQN.3.7-9, Page 5, EQN.3.7-13, Page 5 ELB=3 : EQN.3.7-10, Page 5, EQN.3.7-14,Page 5

15-5


15-6

Section 15A

Table of Steel Design Parameters for ASCE 10-97 Parameter Name LEG

Default Value 0.0

Description This parameter is meant for plain angles. 0.0 = indicates that the angle is connected by both legs and allowable stress in axial tension is 1.0FYLD. 1.0 = indicates that the angle is connected only by the shorter leg and allowable tensile stress is computed per clause 3.10.2 as 0.9FYLD. 2.0 = indicates that the angle is connected by the longer leg.

DBL

0.75 in.

Diameter of bolt for calculation of number of bolts required and the net section factor.

FYB

36 KSI

Yield strength of bolt.

FVB

30 KSI

Shear strength of bolt.

NHL

0

Number of bolt holes on the cross section that should be used to determine the net section factor for tension capacity.

Notes: All values must be provided in the current unit system. Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

15-7

Steel Design per ASCE Manuals and Reports Section

15B

15B.1 General Comments This document presents some general statements regarding the implementation of the Steel Design per ASCE Manuals and Reports on Engineering Practice No. 52 – Guide for Design of Steel Transmission Towers, Second Edition. The design philosophy and procedural logistics for member selection and code checking is based upon the principles of allowable stress design. Two major failure modes are recognized: failure by overstressing and failure by stability considerations.

The following sections describe the salient features regarding the process of calculation of the relevant allowable stresses and the stability criteria being used. Member s are proportioned to resist the design loads without exceeding the allowable stresses and the most economical section is selected based on the least weight criteria. The code checking part of the program also checks the slenderness requirements, the minimum metal thickness requirements and the width-thickness requirements. It is generally assumed that the user will take care of the detailing requirements like provision of stiffeners and check the local effects like flange buckling, web crippling, etc. It general, it may be noted that the concepts followed in MEMBER SELECTION and CODE CHECKING procedures are similar to that of the AISC based design. It is assumed that the user is familiar with the basic concepts of Steel Design facilities available in ST AAD. Please refer to Section 3 of the STAAD Technical Reference Manual for detailed information on this topic. This document specifically addresses the implementation of steel design based on ASCE Pub. 52.

Steel Design Per ASCE Manuals and Reports

15-8

Section 15B

15B.2 Allowable Stresses per ASCE (Pub. 52) The member design and code checking in the STAAD implementation of ASCE (Pub. 52) is based upon the allowable stress design method. Appropriate sections of this publication are referenced below. Allowable Axial Tensile Stress Allowable tensile stresses are calculated on the basis of the procedure described in section 4.10. The NSF parameter (Table 1.1) may be used if the net section area needs to be used. Allowable Axial Compressive Stress Allowable compressive stress calculation is based on the procedures of section 4.6 through 4.9. For angle members under compression, the procedures of sections 4.7 and 4.8 have been implemented. Capacity of the section is computed for column buckling and wherever applicable, torsional buckling. The user may control the effective lengths for buckling using the LX, LY, LZ and/or KX, KY, KZ parameters (Table 1.1). Allowable Bending Compressive Stress Calculations for allowable bending compressive stress about the major axis and minor axis are based on the procedures of section 4.14. Procedures outlined in sections 4.14.1 through 4.14.6 have been implemented. Allowable Bending Tensile Stress Calculations for allowable bending tensile stress about the major and minor axis are based on the procedures of section 4.14.2. Allowable Shear Stress Calculation of the allowable shear stress is based on the procedure outlined in section 4.15 of the ASCE Pub. 52. The procedure of

Section 15B

section 4.15.2 is followed for angles and the procedure of section 4.15.1 is followed for all other sections.

Critical Conditions used as criteria to determine Pass/Fail status These are Clause 4.4 for slenderness limits, Equation 4.12 -1 for Axial Compression and Bending, Equation 4.13-1 for Axial Tension and Bending, Clause 4.9.2 for Maximum w/t ratios and Clause 4.15 for Shear.

15B.3 Design Parameters Design per ASCE (Pub. 52) must be initiated by using the command CODE ASCE. This command should be the first command after the PARAMETER statement. Other applicable parameters are summarized in Table 1.1. These parameters may be used to control the design process to suit specific modeling needs. The default parameter values have been selected such that they are frequently used numbers for conventional design.

15B.4 Code Checking and Member Selection Both code checking and member selection options are available in the ASCE Pub. 52 implementation. For general information on these options, refer to section 3 of the STAAD Technical Reference Manual. For information on specification of these commands, refer to section 6.

15-9


15-10

Section 15B

15B.5 Parameter Definition Table Table 15B.1 - Steel Design Parameters for ASCE (PUB. 52) Based Design Parameter Name

Default Value

Description

KY

1.0

Effective length factor (K) for compression buckling about the Y-axis (minor axis)

KZ

1.0

Effective length factor (K) for compression buckling about the Z-axis (major axis)

KT

1.0

Effective length coefficient for warping restraint (clause 4.14.4, pg 36)

LY

Member Length

Length to calculate slenderness ratio for buckling about the Y-axis (minor axis)

LZ

Member Length

Length to calculate slenderness ratio for buckling about the Z-axis (major axis)

LT

Member Length

Effective length for warping.

FYLD

36.0 KSI

Yield Strength of steel

NSF

1.0

UNL

Member Length

Net section factor for tension members Unsupported length of member for calculation of

UNF

1.0

Same as UNL, but provided as a fraction of the member length

TRACK

0.0

1.0 = Suppresses printing of allowable stresses

DMAX

45.0 in.

Maximum allowable depth for member selection

DMIN

0.0 in.

Minimum allowable depth for member selection

RATIO

1.0

allowable bending stress

1.0 = Prints all allowable stresses

Permissible ratio that determines the cut off point for pass/fail status. A value below this quantity indicates PASS while a value greater than this quantity indicates FAILURE.

Section 15B

15-11

Table 15B.1 - Steel Design Parameters for ASCE (PUB. 52) Based Design Parameter Name BEAM

Default Value 0.0

Description 2.0 = Perform design using the section locations specified according to the SECTION command 3.0 = Perform design at the ends and eleven intermediate sections of the beam

MAIN

2

Parameter that indicates the member type for the purpose of calculating the KL/R ratio (SEE CLAUSE 4.4, PAGE 25) = 10 : DO NOT PERFORM THE KL/R CHECK = 1 : LEG MEMBER

KL/R <= 150

= 2 : COMPRESSION MEMBER KL/R <= 200 = 3 : TENSION MEMBER

KL/R <= 500

= 4 : HANGAR MEMBERS

KL/R <= 375

(Clause 4C.4, page 43) = 5 : REDUNDANT MEMBERS ELA

4

KL/R <= 250

Indicates what type of end conditions are to be used From among Equations 4.7-4 thru 4.7-7 to determine the the KL/R ratio. ELA=1 : EQN.4.7-4, Page 26 (VALID FOR LEG MEMBERS ONLY) ELA=2 : EQN.4.7-5, Page 27 ELA=3 : EQN.4.7-6, Page 27 ELA=4 : EQN.4.7-7, Page 27

ELB

1

Indicates what type of end conditions are to be used From among Equations. 4.7-8 thru 4.7-10 to determine the KL/R ratio. ELB=1 : EQN.4.7-8, Page 27, EQN.4.7-12, Page 28 ELB=2 : EQN.4.7-9, Page 27, EQN.4.7-13, Page 28 ELB=3 : EQN.4.7-10, Page 27, EQN.4.7-14,Page28


15-12

Section 15B

Table 15B.1 - Steel Design Parameters for ASCE (PUB. 52) Based Design Parameter Name LEG

Default Value 0.0

Description This parameter is meant for plain angles. 3.0 = indicates that the angle is connected by both legs and allowable stress in axial tension is 1.0FYLD. 4.0 = indicates that the angle is connected only by the shorter leg and allowable tensile stress is computed per clause 4.10.2 as 0.9FYLD. 5.0 = indicates that the angle is connected by the longer leg.

DBL

0.75 in.

Diameter of bolt for calculation of number of bolts required and the net section factor.

FYB

36 KSI

Yield strength of bolt.

FVB

30 KSI

Shear strength of bolt.

NHL

0

Number of bolt holes on the cross section that should be used to determine the net section factor for tension capacity.

Notes: All values must be provided in the current unit system. Note: Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes.

Section 16

American Steel Design Per A.P.I. Code

16-1

Steel Design Per A.P.I. Section

16

16.1 Design Operations STAAD contains a broad set of facilities for the design of structural members as individual components of an analyzed structure. The member design facilities provide the user with the ability to carry out a number of different design operations. These facilities may be used selectively in accordance with the requirements of the design problem. The operations to perform a design are:    

Specify the members and the load cases to be considered in the design; Specify whether to perform code checking or member selection; Specify design parameter values, if different from the default values; and Specify design parameters to carry out punching shear checks.

These operations may be repeated by the user any number of times depending upon the design requirements, but care should be taken when coupled with manipulation of the punching shear LEG parameter. The basic process is:a.

Define the STAAD model geometry, loading and analysis.

b. Define the API code parameters with LEG 1.0. c.

Run the analysis and API design which creates the Geometry file and give preliminary design results.

d. Check and modify the Geometry file as necessary.

Steel Design Per A.P.I.

16-2

Section 16

e.

Reset the LEG parameter to 2.0 and re-run the analysis to read the modified Geometry file for the final design results.

16.2 Allowables per API Code For steel design, STAAD compares the actual stresses with the allowable stresses as defined by the American Petroleum Institute (API-RP2A) Code. The 20th edition of API Code, as published in 1993, is used as the basis of this design (except for tension stress).

16.2.1 Tension Stress Allowable tension stresses, as calculated in STAAD, are based on the API Code, clause (3.2.1-1). Allowable tension stress on the net section F t = 0.60F y

16.2.2 Shear Stress Beam Shear Stress Allowable beam shear stress on the gross section must conform to (3.2.4-2): F v = 0.4 F y The maximum applied beam shear stress is: f v = V / 0.5 A

(3.2.4-1)

Torsional Shear Stress Allowable torsional shear stress F vt = 0.4 F y

(3.2.4-4)

Section 16

F vt is the maximum torsional shear stress per (3.2.4-3).

16.3 Stress due to Compression The allowable compressive stress on th e gross section of axially loaded compression members is calculated based on the formula 3.2.2-1 in the API Code, when the largest effective slenderness

Kl  Kl  2 E . If exceeds C c the  is less than C c = 2 Fy r  r 

ratio 

allowable compressive stress is increased as per formula (3.2.2 -2) of the Code.

For

D > 60 the lesser of F xe or F xc are substituted for F xy . t

F xe = the elastic local buckling stress calculated with C, the critical elastic buckling coefficient = 0.3 (3.2.2-3) F xc = the inelastic local buckling stress, (3.2.2-4)

16.4 Bending Stress The allowable bending stress for tension and compression for a symmetrical member loaded in the plane of its minor axis, as given in Section 3.2.3 is: a)

F b = 0.75 F y provided

b)



D 1500  (Imperial Units) Fy t

F b = 0.84  1.74



Fy D  Fy Et 

16-3


16-4

Section 16

where

c)

3000 1500 D < < (Imperial Units) Fy Fy t



F b = 0.72  0.58



where

Fy D  Fy Et 

3000 D  300 (Imperial Units) < Fy t

16.5 Combined Compression and Bending Members subjected to both axial compression and bending stresses are proportioned to satisfy API for mula 3.3.1-1 and 3.3.1-2 when

fa is greater than 0.15, otherwise formula 3.3.1-3 applies. It Fa should be noted that during code checking or member selection, if

fa exceeds unity, the program does not compute the second Fa 3.3.1-1/2.

16.6 Design Parameters The program contains a large number of parameter names which are required to perform design and code checks. These parameter names, with their default values, are listed in Table 12.1. These parameters communicate design decisions from the engineer to the program. (Also see section 5.44.1). The default parameter values have been selected such that they are frequently used numbers for conventional design. Depending on the particular design requirements for an analysis, some or all of these parameter values may have to be changed to exactly model the physical structure. For example, by default the KZ value (k value in local z-axis) of a member is set to 1.0, wile in the real

Section 16

16-5

structure it may be 1.5. In that case, the KZ value in the program can be changed to 1.5, as shown in the input instruction (Section 5). Similarly, the TRACK value of a member is set to 0.0, which means no allowable stresses of the member will be printed. If the allowable stresses are to be printed, the TRACK value must be set to 1.0. Notes: The parameter names DMAX and DMIN are only used for member selection. Once a parameter is specified, its value stays at that specified number till it is specified again. This is the way STAAD works for all codes. Table 16.1- American (API) Steel Design Parameters Parameter Name KY

Default Value 1.0

Description K value in local y-axis. Usually, this is minor axis.

KZ

1.0


LY

Member Length

Length in local Y-axis to calculate slenderness ratio.

LZ

Member Length

Length in local Z-axis to calculate slenderness ratio.

FYLD

36 KSI

NSF

1.0

UNL

Member Length

UNF

1.0

CB

1.0

MAIN

0.0

Yield strength of steel. Net section factor for tension members. Unsupported length for calculating allowable bending stress Same as above provided as a fraction of actual member length Cb value as used in Section 1.5 of AISC 0.0 = Cb value to be calculated Any other value will mean the value to be used in design 1.0 = Main member 2.0 = Secondary member

SSY

0.0

0.0 = Sidesway in local y-axis


16-6

Section 16

Table 16.1- American (API) Steel Design Parameters Parameter Name

Default Value

Description 1.0 = No sidesway

SSZ

0.0

CMY

0.85 for sidesway* and calculated for no sidesway

CMZ

Same as above except in local z-axis Cm value in local y & z axes

TRACK

0.0

1.0 =

DMAX

0.0


DMIN

0.0

Minimum allowable depth

RATIO WELD

Print all critical member stresses 100.0 = Suppress all checks except punching shear

Permissible ratio of the actual to allowable stresses 1 for closed sections 2 for open sections

Weld type, as explained in section 3.1.1. 1 = Welding is one side only except for wide flange or tee sections, where the web is always assumed to be welded on both sides. 2 = Welding is both sides. For closed sections like pipe or tube, the welding will be only on one side.

BEAM

1.0

WMIN

1.16 in.

WSTR

0.4 X FLYD

LEG

0.0 = design only for end moments or those at locations specified by the SECTION command. = calculate moments at twelfth points along the beam, and use the maximum Mz location for design. Minimum thickness Allowable welding stress

1.0

To write out external parameters file.

2.0

To read in the external parameters file.

Section 16

16.7 Code Checking The purpose of code checking is to ascertain whether the provided section properties of the members are adequate as per API. Code checking is done using the forces and moments at specific sections of the members. If no sections are specified, the program uses the start and end forces for code checking. When code checking is selected, the program calculates and prints whether the members have passed or failed the checks, the critical condition of API code (like any of the API specifications for compression, tension, shear, etc.), the value of the ratio of the critical condition (overstressed for value more than 1.0 or an y other specified RATIO value), the governing load case, and the location (distance from the start of the number of forces in the member) where the critical condition occurs. Code checking can be done with any type of steel section listed in Section 2.2, American Steel Design, of the Technical Reference manual.

16.8 Member Selection STAAD is capable of performing design operations on specified members. Once an analysis has been performed, the program can select the most economical section, i.e. the lightest section which fulfills the code requirements for the specified member. The section selected will be of the same type section as originally designated for the member being designed. Member selection can also be constrained by the parameters DMAX and DMIN which limits the maximum and minimum depth of the members. Member selection can be performed with all types of hollow steel sections.

16-7


16-8

Section 16

Selection of members whose properties are originally input from a user created table will be limited to sections in the user table. Member selection cannot be performed on members whose section properties are input as prismatic.

16.9 Truss Members As mentioned earlier, a truss member is capable of carrying only axial force. So in design, no time is wasted calcula ting the allowable bending or shear stresses, thus reducing design time considerably. Therefore, if there is any truss member in an analysis (like bracing or strut, etc.), it is wise to declare it as a truss member rather than as a regular frame member wi th both ends pinned.

16.10 Punching Shear For tubular members, punching shear may be checked in accordance with the American Petroleum Institute (API) RP 2A – 20th Edition Section 4. The parameter PUNCH is used to identify joint types for each end of th e member where the punching shear check is required. The PUNCH parameter is only read in from the external geometry file. The external geometry file is described in section 12.13. The PUNCH parameter is not specified within the STAAD input file (the file with the .std extension). Type of Joint and Geometry

Req. Value of Parameter PUNCH

K (overlap) K (gap) T&Y CROSS CROSS (with/diaphragms)

1.0 2.0 3.0 4.0 5.0

Section 16

Note: A value representing joint type and geometry must be provided for parameter PUNCH, in the external file. On the first run where no external table is present, LEG must equal 1.0.

16.11 Generation of the Geometry File Automatic selection of the chord and brace members is performed with the parameter LEG 1.0. Two tubular members are used by the program to identify the chord member. The chord members must be collinear (5 degree tolerance). The chord member must have a greater diameter and thickness than the brace member being considered. The punching shear check is performed on the joint treating it as a T/Y joint. The yield stress of the brace is used. In the 50% strength check the brace and chord yield are assumed to be the same. The major moment axis Mz is taken as In Plane Bending (IPB). To change this, the parameter SWAP 1 should be used in the external geometry file. Note: The in-plane/out-of-plane correspondence can be set by using the BETA angle. If the punching shear cannot be performed at the joint for the member being considered, a message is written to the output file .ANL. If a punching shear check is performed with the parameter LEG 1.0 used, then the geometry data used to perform the check is written to the default external output file APIPUN. The default external output/input file name can be chang ed by using the command line:-

16-9


16-10

Section 16

CODE API . This external output data file can be edited and used as an external input file to re-perform the check using the parameter PUNCH 1.0 to 5.0. This external input file allows can/stub geometry data to be specified and chords to be assigned geometry where they could not be identified in the Automatic selection. The parameter LEG 2.0 must be used to read an external input file where the default name is APIPUN. The yield strength of the brace is used in th e punching shear check. This can be changed in the external geometry file. The user should ensure that the correct cord member has been selected for the check.

16.12 Chord Selection and Qf Parameter Q f is a factor to account for the presence of nominal longitudinal stress in the chord. When calculating Q f for the joints, the moments used in the chord stress calculation will be from the computer node results and not the representative moments underneath the brace. If the moment varies significantly a long the chord, it is more accurate to use the actual chord moment in the middle of the brace foot print. The tests reported in Reference I 1 were performed with a constant moment along the chord. Thus for a local joint check, the local chord moment (under the brace) should be used. STAAD calculates Q f based on the moment at the chord member. The chord member can be selected automatically by initial screening by the program (based on geometry and independent of loading) or specified by the user in the External file. 1

Ref I: Boone, TJ, Yura, JA and Hoadley, PW, Ultimate Strength if Tubular Joints – Chord Stress Effects, OTC 4828, 1984

Section 16

16-11

In the automatic selection of the chord two collinear members (5 degree tolerance) are used to identify the chord. The chord is then selected from one of the two members based on the larger diameter then thickness or then by the minimum framing angle; for T joints the first member modeled will be selected as the chord. The user should confirm that the chord either be assigned by the program or the user is representative of the local chord moment for the brace in question.

16.13 External Geometry File An example of the external geometry file is shown below: BRACE

CHORD

PUNCH

D

T

d

T

GAP

FYLD

THETAT

TW

SWAP

209

211

3

17.992

0.984

12.752

0.787

0.000

50.00

0.00

0.000

0

209

210

3

17.992

0.984

12.752

0.787

0.000

50.00

0.00

0.000

0

212

202

3

17.992

0.787

12.752

0.787

0.000

50.00

0.00

0.000

0

The parameters used in the external file are defined as follows: Table 16.2 – External File Parameter

Description

PUNCH BRACE

Parameter for punching shear (See Section 12.10) Member number of brace

CHORD D

Member number of chord Chord Diameter in inches

T

Chord Thickness in inches

d T

Brace Diameter in inches Brace Thickness in inches

GAP

Gap in inches (must be negative for overlap K-joint)

FYLD

Local yield strength used for joint in KIPS

THETAT

Angle of through brace in overlap K-joint in


16-12

Section 16

Table 16.2 – External File Parameter TW

SW AP

Description Degrees Used in overlap K-joint, taken as the lesser of the weld throat thickness or thickness t of the thinner brace in inches If parameter SWAP 0 is used then major moment Mz is taken for In Plane Bending (IPB). SWAP 1 uses the minor moment My as the IPB.

Notes:  





For overlap K-joints, the through brace is assumed to be the same diameter as the brace being checked. If any of the parameters for diameter and thickness specified in the external file are less than that for members being checked, then the member properties specified in the STAAD file shall be used. The member diameter and thickness should be used in API equation (4.1-1); in this check it has been assumed that the yield strength of the chord and brace members are the same. The geometry file name is currently limited to eight characters (4 if an extension as .txt is used).

The overall process of performing punching shear checks consists of two steps. These steps are explained in section 12.16.

16.14 Limitations The parameter SELECT 1.0 should not be used while carrying out punching shear checks. It can be used in initial runs for member selection. No classification of the joint is performed using the loading. No hydrostatic checks are performed.

Section 16

16.15 Tabulated Results of Steel Design For code checking or member selection, the program produces the results in a tabulated fashion. The items in the output table are explained as follows: a)

Member refers to the member number for which the design is performed.

b)

TABLE refers to AISC steel section name which has been checked against the steel code or has been selected.

c)

RESULTS prints whether the member has PASSed or FAILed. If the RESULT is FAIL, there will be an a sterisk (*) mark on front of the member.

d)

CRITICAL COND refers to the section of the AISC code which governs the design.

e)

RATIO prints the ratio of the actual stresses to allowable stresses for the critical condition. Normally a value of 1.0 or less will mean the member has passed.

f)

LOADING provides the load case number which governed the design.

g)

FX, MY, and MZ provide the axial force, moment in local Y-axis, and the moment in local Z-axis respectively. Although STAAD does consider all the member forces and moments (except torsion) to perform design, only FX, MY and MZ are printed since they are the ones which are of interest, in most cases.

h)

LOCATION specifies the actual distance from the start of the member to the section where design forces govern.

i)

If the parameter TRACK is set to 1.0, the program will block out part of the table and will print the allowable bending stressed in compression (FCY & FCZ) and tension (FTY & FTZ), allowable axial stress in compression (FA), and allowable shear stress (FV).

16-13


16-14

Section 16

16.16 The Two-Step Process The overall procedure for performing the code check per the API code is as follows: Step 1 – Creating the geometry data file. This is done by specifying the name of the geometry data file alongside the command line CODE API. If a file name is not specified, STAAD automatically assigns the file name APIPUN to the geometry data file. The parameter instructions in the .std file should contain the LEG parameter and it should be assigned the value 1.0.

Example Reading External Geometry File UNIT INCHES KIPS PARAMETERS * All joint data will be written to external file GEOM1 for punching shear. CODE API GEOM1 LEG 1.0 * Joints to be considered as T and Y, i.e. PUNCH is set to 3.0. FYLD 50.0 ALL TRACK 1.0 ALL RATIO 1.0 ALL BEAM 1.0 ALL CHECK CODE ALL After ensuring that your STAAD input file contains the above data, run the analysis. Once the analysis is completed, you will find that a file by the name GEOM1 has been created and is located in the same folder as the one where your .std file is located. (In case you did not specify a file name - GEOM1 shown in the earlier example - STAAD will create the file named APIPUN.

Section 16

Step 2 – The geometry data file (GEOM 1 or otherwise) should be inspected and modified as required such as changing the PUNCH values and local section properties for the punching shear checks. Modify the .std file so it reruns the code check process by reading the instructions of the GEOM file. This message is conveyed by changing the value of the LEG parameter to 2.0. After making this change, a re-analysis will result in the program using the information in the geometry data file (GEOM1, APIPUN, or otherwise) for performing the code check.

Example Reading an existing Joint Geometry Data File, GEOM1 UNIT INCHES KIPS PARAMETERS * All joint data will be read from the external file GEOM1 for punching shear. CODE API GEOM1 LEG 2.0 FYLD 50.0 ALL TRACK 1.0 ALL RATIO 1.0 ALL BEAM 1.0 ALL CHECK CODE ALL

16-15


16-16

Section 16

Staadpro 2007 International Codes 2007 Complete

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