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Assessment cover shee

ENG 1020 Engineering Structures

24428817 Yeap Ci Qing

23732288 Hendrata Kristian

v

AlMansari Ahmed23848138

24735124 ShivaNarayan

Lim Pooi Mee

26/04/2013 24/04/2013

Tuesday, 16.00

Kristian Hendrata

Yeap Ci Qing

Ahmed Almansari

Shiva Narayan

24/04/2013

24/04/2013

24/04/2013

24/04/2013

Project 1 : Truss Design Report


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ENG1020 ENGINEERING STRUCTURE

Monash University Sunway Campus

Department of Civil Engineering

Truss Design Report

Group assignment

Name: Ahmed AlMansari ID: 23848138

Name: Kristian Hendrata ID: 23732288

Name: Shiva Narayan ID: 24735124

Name: Matthew Yeap Ci Qing ID: 24428817

Tutor : Lim Pooi Mee

Session : Tuesday, 16.00-18.00

Submission dates: 23 April 2013


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SummaryThis is a report of the design of a truss for the pedestrian bridge. The bridges will be

constructed across the new highway between Monash University Sunway Campus and the

Western Carpark. Two designs will be shown, one of them is initial design, which is an

assumption and another is an optimized final design.

Firstly, the geometry of the truss will be shown with all estimated loadings, for instance, dead

loads, live loads and wind loading for initial design to initialize the calculation. Afterwards,

the analysis of truss will describe how the estimated design loads will be allocated, how

much external reactions at the contact point with ground will be generated and how muchinternal forces at each members will exist. Lastly, is a full detailed failure check on yielding

and buckling of critical members. With all the data collected, optimisation was performed to

find a material with enough support and least resources for the truss design.

In short, this report wills demonstrates the main features of the support of the bridge in three

areas, which are geometry, analysis and optimization of the truss. This report will show that

the final size of SHS 20x20x1.6 is suitable to support the bridge and using the least materials. !!

!!!!


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Table&of&Contents&

Summary. ii

1.0$Introduction!..........................................................................................................................!1$1.1$Problems$and$Limitation$for$the$application !..........................................................................!1$

1.2$Background$of$the$truss !..............................................................................................................!1$2.0$The$Geometry$of$Truss!.......................................................................................................!1$2.1$Assumption$of$the$pedestrian$bridge !.......................................................................................!1$2.1.1$Dead$Loads$..............................................................................................................................................$2 $2.1.2$Live$Load$..................................................................................................................................................$2 $2.1.3$Wind$Load$...............................................................................................................................................$3 $

2.2$Design$of$Trusses!..........................................................................................................................!3$

3.0$Analysis$of$truss!...................................................................................................................!5$3.1$Allocation$of$the$loads !.................................................................................................................!5$3.2$Reactions$of$the$truss !...................................................................................................................!5$3.3$Internal$forces$of$each$members !...............................................................................................!6$

4.0$Optimization$of$The$Truss!.................................................................................................!7$4.1$Failure$checking !............................................................................................................................!7$4.2$Optimization!..................................................................................................................................!7$

5.0$Conclusions!...........................................................................................................................!7$

6.0$References!.............................................................................................................................!8$

$$$$$$$Appendices$

Appendix AGeometry of the bridgeAppendix B Loadings of all estimated dead, live and wind loads

Appendix C Load Paths and Supports

Appendix D Truss AnalysisAppendix E Failure checking and OptimisationAppendix F Final Design


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1.0 Introduction

1.1 Problems and Limitation for the application

An opportunity has come, a new pedestrian bridge, in between Monash University and theWestern Carpark, is on demand. The bridge has to span over twenty meters across the new

highway and link our fellow students to their cars. To avoid the truss towers to be built too closeto the highway, a tolerance of four meters for the bridge should be given if the width of truss is

smaller than one meter. Meanwhile, overhead walkway should height over five meters but notover designed, so that trucks can pass by and users will not be tortured. Also the majority of

drivers in campus at the moment appear to be stand around average Asian, obesity is also not thatpopular around the campus, thus a height of two and a half meters by width of two meters

walkway can be expected. Since the major objective is to design the truss, materials beyondtrusses will be over designed and might not be suitable for real application. These are the major

concerns of the team when decisions were made.

1.2 Background of the truss

Truss is a framework of stone or timber, typically consisting of rafters, posts, and struts,supporting a roof, bridge, or other structure, usually consisting of triangular units (Lindberg &

Stevenson, 2010). In this application, four trusses are to be form a truss tower and support thepedestrian bridge and all of them have the identical design. The truss is the one that takes the

most static loading among other trusses. Furthermore, the ratio of the width and height of a trussshould range between 1:10 to 1:20.

2.0 The Geometry of Truss

2.1 Assumption of the pedestrian bridge

First of all, dimensions of the bridge are decided under the limitation defined in the introduction.Length of the bridge is twenty-four meters, with a width of two meters and stand five meters

high from ground level. The walkway of the bridge has two and a half meters height to allowmost pedestrian pass by. Advertising board will be equipped on each side of truss towers. For

detailed drawings please refers to Appendix A. In addition, assumptions of loads support bytrusses were made to initialize the calculation. Typically the calculation of loads will be products

of quantities and specific mass in term of kilo newton. However, the values of assumptions areslightly exaggerated and have not been optimized, so that designed trusses will not easily fail in

real application. For instance the loads are dead loads, live load and wind load. Moreover, theloads were applied with magnification factor to satisfy Ultimate Limit State (ULS) of the trusses

to reduce the chance of collapse (Department of Civil Engineering, 2001). Detailed calculationsand references of properties are performed in Appendix B.


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Figure 1. Front view of the bridge.

The major logical thinking behind the calculations of loads is below:

2.1.1 Dead Loads

Dead loads are weight of components that are fixed with the bridge and will be carried by

the trusses. The domain includes the loads of roof, roof frames, frames of advertising board(AD), floor, trusses, lamps and handrails. A list of the properties of the dead loads is prepared as

following:Weight of roof : 4.58kg/m

2

Weight of roof frames : 12kg/mWeight of AD frames : 5.56kg/m

Weight of floor : 28kg/m2

Weight of trusses : 10kg/m

Weight of lighting : 1.2kg per lampWeight of handrails : 3.10kg/m

During detailed calculation, each of them is expressed in term of kilo newton (kN) andmultiplied with their corresponding quantities. However, please note that loads of trusses are

initialized, as 10kg/m, but the value will be reassigned after optimization. Additionally, the loadsof trusses and frames of advertising board will be refer later in Method of Joints and Method of

Section instead of allocation of loads.

2.1.2 Live Load

At the moment, the bridge is designed exclusively for pedestrians only.

Weight of pedestrian : 100kg per person

Occupancy of people : 4 person per meter squareAreas of the floor : 48m

2

The total live loads will be multiplier of the given predictions and areas can be occupied, the

same logic as the calculation of dead loads. Total loads of both dead and live loads aresummarized in table 1 , exclude the loads of trusses and frames of advertising board.


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Items Loads (kN) ULS (kN)Roof 2.1984 2.638Roof frame 26.04 31.248Floor 13.44 16.128Lighting 0.2880 0.3456Handrail 1.488 1.786Live Loads 192 288TOTAL 235.454 340.145Table 1. Loads beyond the trusses, for detailed calculation please refers to Appendix B.

2.1.3 Wind Load

In this case, the wind load was designed to blow only from a horizontal direction to create a

worst-case scenario. However the wind load was not factored with any standard. Wind load will

be applied on advertising boards and pushes truss tower from the sides with fewer loadsallocated to the sides with more loads. This load path is important to make sure the wind doesn'taffect the structures stability. In this report, the load carried by the wind was assumed to be:

Wind pressures : 0.5 kPaAreas of a advertising board : 2.5 m

2

Wind loads on a advertising board : 1.25kN

2.2 Design of Trusses

The geometries of the truss were determined by limitation mentioned earlier in the introduction

such as trucks should be able to pass the bridge. The height of truss towers is five meters, and the

width of truss is half a meter to make sure the ratio of width and height is between 1:10 to 1:20.Angles between diagonal and horizontal members are designed to be forty-five degrees, so thatlength of vertical members is identical with horizontal members. Also directions of diagonal

members will alternate between forty-five and one hundred and thirty five degrees. At groundlevel, one side of the truss is hinged and another is roller. Figure 2 presents the side view of a

truss.


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Figure 2. Side view of the truss, all dimensions in mm

The stability of the design can be determined using the following equation:

m + r = 2jm : member of the truss

r: number of external reactionsj: number of joint in structure

m + r = 2j Stable Determinate

m + r > 2j Stable Indeterminate

m + r < 2j Unstable Undefined


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From figure 2, (41) + (3) = 2(22), which is left hand side equals to right hand side. Thus the trusswill be stable and determinate.

3.0 Analysis of truss

3.1 Allocation of the loads

Figure 3. Top view of the bridge, all dimensions in mm.

All of the loads collected in section 2.1 will be treated as UDL to simplify the question. So the

loads will be divided according to the areas of each joints take part. In addition, a truss towerconsists of four trusses, eight joints in total. On the other hand, each two joints of the eight joints

are extremely close to each other, which means the team can take it as sixteen quadrilaterals andthen halve the values into two joints of that area. The result of allocation is shown as figure 3.

The highest value will be thirty-one and twenty two hundredth kilo newton and the highest value

of adjacent joints is ten and four hundreds and eight thousandth kilo newton. Go to Appendix Cfor detailed calculations.

3.2 Reactions of the truss

The truss with highest value of allocated loads is examined. constructed with the approximatevalue of loads and forces on each truss members. The structure will undergo a bending moment,

but the design truss will then apply the equilibrium bending moment equation in order to balanceback the force generated by the wind and cancel out the forces to achieve the stable structure.

The three state of equilibrium of the structure was described using the equations stated below:

Fx = 0 shows an equilibrium on x-axisFy = 0 shows an equilibrium on y-axisM = 0 shows an equilibrium for the moment from any point

Reactions:Ry1 = -9.008kN

Rx1 = 0.6250kN

Ry2 = 36.07kN


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3.3 Internal forces of each members

The internal forces will be calculated by Method of joints and checked by Method of section andreactions. Sum of forces in x and y direction will equals to zeros was used to find all the internal

forces of every member joints by joints, while method of sections was used to check thecalculation. Bear in mind that the self-weight of the truss is distributed to each joint according

the length of trusses around the joints. In defense of the team, although it cost a little more effortsto do that, calculations standing on a solid foundation are increasing our faith on the result.

Detailed calculations available in Appendix D.For vertical members:

Highest compression : 35.807kNFor diagonal members:

Highest tension : 0.905kNHighest compression : 0.751kN

Figure 4. Internal Forces Diagram, all dimensions in kN.


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4.0 Optimization of The Truss

4.1 Failure checkingProperties of SHS 65x65x6.0

Yielding Stress : 350MPa

Buckling Force : 5574kNActual and design Stress for highest tension and compression member is needed. The conditionof not failing is the actual stress smaller than the design stress. Both yielding and buckling is

checked with the dimension of SHS 65x65x6.0 using P=F/A and F = 2EI/L

2.

Actual Stress and Force

Compression Yielding Stress : 27.76 MPaTension Yielding Stress : 0.702 MPa

Buckling Force : 35.807 kNThe result appears to be a pass. All detailed calculations in this section are in Appendix E.

4.2 OptimizationOptimization is similar with failure checking, same equations were applied just that differentvariables that varies. The value of maximum compression is then used and manipulated in the

buckling and yielding equation to get the minimum gross section area and moment of inertia, Ivalue of the truss. The value of maximum tension is also used in the yielding equation to get the

minimum gross section area. Using the values from previous calculation, the team can getmaximum three ranges in table of section hollow size. Choose the sizes that include all three sets

with the least mass, it will be a better materials that have enough supports and fewer mass.Beware that vertical and diagonal members require different sizes, which means two times of

comparing and choosing. Use the new values and redo section 2.1.1, 3.0 and 4.0 until new valuesequals to the old values. It will be wise to let programs to do it for the team. All detailed

calculations in this section are in Appendix E&F.Equations:

Amin = Fmax/PImin = FmaxL

2/

2E

Result :

Highest Amin = 105.3mm2

Highest Imin = 0.004535 x 106mm

4

5.0 Conclusions

In conclusion, after repeated calculation, the team found that the best sizes of the truss membersfor the bridge will be SHS 20x20x1.6 and the members intermediate the bridge and at the ground

level were most heavily loaded. .


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6. ReferencesLindberg, C. A., & Stevenson, A. (Eds.). (2010). New Oxford American Dictionary (3

ed.). Oxford University Press.Department of Civil Engineering. (2001). ENG1020 Engineering Structure Study Guide.

Monash University.

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