UNIVERSITY OF MAURITIUS
DEPARTMENT OF CIVIL ENGINEERING Module Name: Structural Design I
Module Code: CIVE 2016 Y (3)
Student Name & ID: 131 0372 – Veeramah Veeramah Avinaash
131 8156 – Bhirugnath Bhirugnath Yashveer Name of Assessor: Mr. Sailesh Sailesh Kumar Nunkoo
Signature of Assessor:
Date: 6 th March 2015
WRITTEN REPORT ASSESSMENT FORM Marks allocated on a 40/ 60 basis Remarks made with respect to guidance over page PRESENTATION, STYLE, LANGUAGE (40%) Remarks---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Mark (max 40):
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CONTENT (60%) Remarks-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Mark (max 60): ----OTHERS Remarks------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Total Mark (max 100): -----
CIVIL ENGINEERING DEPARTMENT
CIVE 2016 Y (3)
COURSEWORK:
Analysis of the load transfer sequences of the UoM Gymnasium.
By:
Veeramah Avinaash – 131 131 0372 Bhirugnath Yashveer Yashveer – 131 131 8156
6 th March 2015
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1. PRESENTATION, STYLE, LANGUAGE (40%)
ASSESSOR TO INDICATE HERE GENERAL COMMENTS
i. Presentation and style Structure of report: Use of tables, diagrams, pictures: General appeal: ii.
Language
Grammar/ Use of English: Spelling/ Clarity of expression: Overall quality: 2. CONTENT i.
(60%)
Write Up
Coverage: Level of detail: Accuracy: Use of references: Overall quality: ii. Graphs, tables, illustrations Clarity: Details: Accuracy: Overall quality:
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Acknowledgements We seize this opportunity to express our gratitude to Mr. S.Nunkoo, our lecturer, who provided us with a unique chance to work on this assignment. Being new to the concept of steel design, we ’ve been able to enrich our understanding of the subject matter and are now able to describe the components of any steel framed building along with describing the load paths taken by different load systems acting on it. Furthermore, this assignment has led us to appreciate the use of steel as a structural material in the construction of specific buildings.
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Table of Contents 1.0 Introduction ............................................................................................................................................. 1 1.1 Aim ..................................................................................................................................................... 1 1.2 Objectives ........................................................................................................................................... 1 2.0 Desk study ............................................................................................................................................... 2 2.1 Gymnasium sketches .......................................................................................................................... 2 2.1.1 General layout of gymnasium ...................................................................................................... 2 2.1.2 Top view of gymnasium .............................................................................................................. 3 2.1.3 Side view of gymnasium .............................................................................................................. 3 2.1.4 Front view of gymnasium ............................................................................................................ 4 2.1.5 Overall view of gymnasium steel structure .................................................................................. 4 2.2 Description of the structural members of UoM gymnasium ............................................................... 5 2.2.1 Purlins .......................................................................................................................................... 5 2.2.2 Rafters and haunched joints ......................................................................................................... 5 2.2.3 Bridges ......................................................................................................................................... 6 2.2.4 Braces........................................................................................................................................... 7 2.2.5 Cylindrical beams ........................................................................................................................ 9 2.3 Method of design of steel framework of UoM Gymnasium ............................................................. 10 2.4 Load transfer mechanisms ................................................................................................................ 10 2.4.1 Transfer of gravity loads ............................................................................................................ 11 2.4.2 Transfer of wind loads ............................................................................................................... 12 3.0 Conclusion ............................................................................................................................................ 14 References ................................................................................................................................................... 15
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List of figures Figure 1 - General layout sketch of UoM gymnasium. ................................................................................. 2 Figure 2 - Top view of UoM gymnasium. .................................................................................................... 3 Figure 3 - Side view of UoM gymnasium..................................................................................................... 3 Figure 4 - Front view of UoM gymnasium. .................................................................................................. 4 Figure 5 - Overall view of the UoM gymnasium. ......................................................................................... 4 Figure 6 - Purlins used in the UoM gymnasium. .......................................................................................... 5 Figure 7 - Rafter connected to a column via a haunched joint...................................................................... 6 Figure 8 - Bridges, fixed to purlins, at the UoM gymnasium. ...................................................................... 6 Figure 9 - Fly brace at the UoM gymnasium. ............................................................................................... 7 Figure 10 - Roof braces at UoM gymnasium. ............................................................................................... 8 Figure 11 - Side braces (K-shaped) at the UoM gymnasium. ....................................................................... 9 Figure 12 - Cylindrical beams at UoM gymnasium. ..................................................................................... 9 Figure 13 - Representative diagram of load path for gravity load system. ................................................. 11 Figure 14 - Representative diagram of load path for wind loading along the steel frame. ......................... 12 Figure 15 - Representative diagram of load path for wind loads perpendicular to the gable ends. ............ 13
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1.0 Introduction Structures are designed in such a way that they are able to resist the applied loads onto them as well as providing a pathway to channelize these loads to a safe medium. This pathway is called a load path. A load path is, in a more technical jargon, a passageway that transfers loads on a building structure to the foundation system and transmits them to the ground. This ensures that there is no collapse of the structure or any other structural damage. 1.1 Ai m
The main aim of this assignment is to be able to describe the load paths taken by different load systems acting on a steel frames structure. The chosen steel structure is the gymnasium of the University of Mauritius. 1.2 Obj ecti ves
The objectives set out to be able to meet the specified aim are as follows: a) Visiting the above-named gymnasium. b) Producing sketches of the gymnasium using a CAD software. In this case, the chosen software was AutoCAD. c) Recognizing and describing the different structural members of the building. d) Analysing the different types of load systems acting on the building.
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2.0 Desk study Following a site visit to the gymnasium, we were able to identify the main structural members of the structure as well as producing its sketches. 2.1 Gymn asi um sketches
The 2-D sketches were produced using AutoCAD and then plotted as pictures in this document. Furthermore, an overall view of the gymnasium was produced using another CAD software, namely Sketch Up, has been included. 2.1.1 General layout of gymnasium
Figure 1 - General layout sketch of UoM gymnasium.
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2.1.2 Top view of gymnasium 44.3 m
34.0 m
Figure 2 - Top view of UoM gymnasium.
Note: The red lines represent the braces of the steel structure. 2.1.3 Side view of gymnasium
8.0 m
Figure 3 - Side view of UoM gymnasium.
Note: The blue lines represent the side and fly braces of the steel structure.
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2.1.4 Front view of gymnasium
10.0 m
10.0 m
34.0 m Figure 4 - Front view of UoM gymnasium.
2.1.5 Overall view of gymnasium steel structure
Figure 5 - Overall view of the UoM gymnasium.
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2.2 Descri ption of the str uctur al members of U oM gymnasiu m
2.2.1 Purlins It is a member subjected to biaxial bending. In the gymnasium, the purlins are connected to the steel framework by using bolts through cleats. The latter are fixed to the columns or rafters. Its main purposes are: a. support external cladding of the gymnasium. b. minimise lateral torsional buckling of the rafter at connecting joints.
Purlins
Figure 6 - Purlins used in the UoM gymnasium.
2.2.2 Rafters and haunched joints Rafters are the inclined structural members of the roof framework. They provide lateral and torsional restraint at the supports. They are connected to columns by haunched joints. The latter are situated at the rafter-to-rafter, apex and rafter-to-column connections. They increase the resistive moment at the joints while adding stiffness to the frame. Excessive deflection is reduced and local buckling is prevented.
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Figure 7 - Rafter connected to a column via a haunched joint.
2.2.3 Bridges Bridges are members fitted midway between and fixed to the purlins to prevent twisting of the latter. Moreover, the presence of ridges reduces deflection.
Bridge
Bridge
Figure 8 - Bridges, fixed to purlins, at the UoM gymnasium.
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2.2.4 Braces Braces are secondary members which stabilise the main members by providing a pathway for the transfer of loads while also providing restraint to compression flanges. 3 main types of braces have been used in the steel framework of the UoM gymnasium. a. Fly-braces (V-shaped) They are connected from the bottom flange of the rafter to the purlins and provide restraint to lateral torsional buckling of the rafters.
Fly-brace Figure 9 - Fly brace at the UoM gymnasium.
b. Roof braces These are plan braces which prevent lateral buckling of the compression flanges of the roof beams.
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Roof braces
Figure 10 - Roof braces at UoM gymnasium.
c. Side braces (K-shaped) They are found at the 4 extremities of the steel framework. Their main purpose is to resist torsional effects on the columns which can occur mainly due to wind loads.
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Side braces
Figure 11 - Side braces (K-shaped) at the UoM gymnasium.
2.2.5 Cylindrical beams These are secondary beams which link the columns and restrict the latter from moving sideways while also helping to transmit horizontal forces.
Cylindrical beam
Figure 12 - Cylindrical beams at UoM gymnasium.
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2.3 M ethod of design of steel fr amework of U oM Gymnasiu m
There are 3 main types of methods adopted for the design of a steel structure. They are: 1. Simple design – The joints are not required to resist moments. 2. Continuous design – Only the structural properties of the members need to be considered in global analysis. 3. Semi-continuous design – The structural properties of both the members and connections need explicit consideration in global analysis. In this case, the continuous design method has been considered, which is exemplified by the use of haunched joints. The end connections are assumed to be rigid and capable of transmitting moments and shear forces between members. Also, the frame attains stability against side-sway by the bending of beams and columns. 2.4 Load tr ansfer mechanisms
The 2 main types of loads encountered by the gymnasium are: 1. Gravity loads – These include self-weights of the different components, the weight of finishes and wind loads acting vertically. 2. Lateral loads – These include mainly wind loads acting in different directions. The mechanism of transfer of the loads is described as per the following flow charts.
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2.4.1 Transfer of gravity loads Load from cladding and selfweights of members.
Rafters (in terms of bending stresses)
Haunched joints (these take the moments from the rafters).
Columns
Foundation bases
Ground
Figure 13 - Representative diagram of load path for gravity load system.
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2.4.2 Transfer of wind loads 2.4.2.1 Case 1 – Wind loads along steel frame Wind loads
Roof braces (majority of loads)
Beams (small portion of the loads)
Side braces
Columns
Foundation
Ground
Figure 14 - Representative diagram of load path for wind loading along the steel frame.
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2.4.2.2 Case 2 – Wind loads perpendicular to gable ends. Winds loads
Roof braces (with the haunched joints resisting the moments caused by the wind loads)
Concrete columns
Foundation base
Ground
Figure 15 - Representative diagram of load path for wind loads perpendicular to the gable ends.
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3.0 Conclusion It is definitely clear that loads within a building must find their way to the ground b y some method. If this does not happen, being inside of a building would never be a safe situation. Without a clear gravity system, the loads due to the self-weight of the structural system and building materials would distribute themselves randomly. Without a lateral system, a building would fall over like a stack of cards if a big gust of wind came, or if an earthquake hit. This would also lead to many injuries and deaths in both cases. Therefore, the load path process is essential to structural engineering and safety of the public.
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References 1. Kristen Lechner, M.,2007. Load Paths in a Braced Frame Steel Building [online].Available from: http://www.personal.psu.edu/kml5016/blogs/kristen_lechners_e portfolio/Technical%20Description.pdf [Accessed on 1st March 2015]. 2. Victor Saouma, E. Structural Concepts and Systems for Architects [online]. University of Colorado, Boulder, CO 80309-0428 Available from: http://ceae.colorado.edu/~saouma/Lecture-Notes/s4a.pdf [Accessed on 2nd March 2015].
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