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 Anatomy of A Bridge Anatomy of A Bridge

 Atin Sinha, Ph.D., P.E. Atin Sinha, Ph.D., P.E.

 Albany State University Albany State University

 Anatomy of A Bridge

 Atin Sinha, Ph.D., P.E. Atin Sinha, Ph.D., P.E.

 Albany State University Albany State University

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Different Types of BridgesDifferent Types of Bridges

• Truss BridgeTruss Bridge

• Suspension BridgeSuspension Bridge

•

Cable Stayed BridgeCable Stayed Bridge

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Truss BridgeTruss Bridge

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Truss BridgeTruss Bridge

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Suspension BridgeSuspension Bridge

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Suspension BridgeSuspension Bridge

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Cable Stayed BridgeCable Stayed Bridge

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Cable Stayed BridgeCable Stayed Bridge

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oads E!perien"ed by A Bridgeoads E!perien"ed by A Bridge Stati" #Stru"tural$Stati" #Stru"tural$

%ariable #%ehi"ular Traffi", Pedestrian$%ariable #%ehi"ular Traffi", Pedestrian$

Environmental #&ind, Earth'ua(e$Environmental #&ind, Earth'ua(e$

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Forces that Act on BridgesForces that Act on Bridges

TensionTension

CompressionCompressionTorsionTorsion

Shear Shear 

http://www.garrettsbridges.com/design/theforces/http://www.garrettsbridges.com/design/theforces/http://www.garrettsbridges.com/design/theforces/

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Suspension vs. Cable StayedSuspension vs. Cable Stayed

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Common Trusses Used inCommon Trusses Used in

Engineering)Engineering)Warren Pratt

Howe K Truss

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Red represents tension, blue represents compression,

 and green is no load

Now examine the same Warren truss,

but with added vertical members

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*odel Bridge Building Steps*odel Bridge Building Steps

earn the +ules of the Competitionearn the +ules of the Competition

Design the BridgeDesign the Bridge

et the Supplieset the Supplies Build the BridgeBuild the Bridge

Test the BridgeTest the Bridge

 Analy-e the ailure Analy-e the ailure /mprove 0our Design/mprove 0our Design

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South1est eorgia +egional *odel BridgeSouth1est eorgia +egional *odel Bridge

Building ContestBuilding Contest

Design Specifications for the odel BridgeDesign Specifications for the odel BridgeSpanSpan 22 in.22 in.

*a!imum Allo1able &eight*a!imum Allo1able &eight 23.4 g23.4 g

*a!imum Allo1able 5eight #6verall$*a!imum Allo1able 5eight #6verall$ 78 in78 in

*a! Superstru"ture 5eight*a! Superstru"ture 5eight 9 in9 in

*a! Substru"ture 5eight*a! Substru"ture 5eight : in: in

*inimum verti"al "learan"e through the bridge*inimum verti"al "learan"e through the bridge 2 in2 in

*inimum hori-ontal "learan"e through the bridge*inimum hori-ontal "learan"e through the bridge 2 in2 in

No height restriction for Middle SchoolsNo height restriction for Middle Schools

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Design the BridgeDesign the Bridge

Center the design around the loading pointCenter the design around the loading point Provide e!tra bra"ing around the loading pointProvide e!tra bra"ing around the loading point

Choose a truss &arren, Pratt or design your o1nChoose a truss &arren, Pratt or design your o1n

Dra1 the bridge to s"ale on graph paper Dra1 the bridge to s"ale on graph paper 

Create a list of all the pie"esCreate a list of all the pie"es

Cut the pie"es to e!a"t si-eCut the pie"es to e!a"t si-e

abel and 1eight every pie"eabel and 1eight every pie"e

 Allo1 78; 1eight for glue Allo1 78; 1eight for glue

/f you e!"eed the 1eight limit, modify the design/f you e!"eed the 1eight limit, modify the design

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Preparation for Building the BridgePreparation for Building the Bridge

et the 1oodet the 1ood 5obby stores5obby stores Spe"iali-ed Spe"iali-ed Balsa."omBalsa."om  Pi"( out the E!a"to (nife ram s"aleram s"ale

Clamps>"lothespinsClamps>"lothespins oam Board #optional$oam Board #optional$

&or(spa"e&or(spa"e ood lightingood lighting

ood ventilationood ventilation 

http://www.specializedbalsa.com/http://www.specializedbalsa.com/http://www.specializedbalsa.com/http://www.specializedbalsa.com/http://www.specializedbalsa.com/http://www.specializedbalsa.com/

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Build the BridgeBuild the Bridge

Tape the top and bottom beams to the design onTape the top and bottom beams to the design on

the graph paper the graph paper 

lue the remaining pie"es and "ure overnightlue the remaining pie"es and "ure overnight

holding firmly using pins.holding firmly using pins.  After both trusses are "ompleted, tape them to After both trusses are "ompleted, tape them to

t1o fi!ed bo!es spa"ed "orre"tly apartt1o fi!ed bo!es spa"ed "orre"tly apart

lue bra"ing on top and bottomlue bra"ing on top and bottom *a(e sure the bridge is not leaning on one side*a(e sure the bridge is not leaning on one side

&eigh the bridge and re"ord in"luding the spe"s&eigh the bridge and re"ord in"luding the spe"s

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Test the BridgeTest the Bridge

Test before "ompetition if)Test before "ompetition if)  0ou have time to build another bridge0ou have time to build another bridge

0ou are only testing your bridge to a "ertain point0ou are only testing your bridge to a "ertain point

Testing e'uipmentTesting e'uipment  Bathroom s"ale #top loaded only$Bathroom s"ale #top loaded only$

Bu"(et and sand #top or bottom$Bu"(et and sand #top or bottom$

Testing pro"edureTesting pro"edure Pour the sand slo1ly but steadilyPour the sand slo1ly but steadily

&at"h for defle"tion # 2= is "onsidered failure$&at"h for defle"tion # 2= is "onsidered failure$

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Evaluation of the BridgeEvaluation of the Bridge

Effi"ien"yEffi"ien"y ? mass that bridge held divided by mass? mass that bridge held divided by mass

of bridgeof bridge /n order to 1in typi"ally s"ore need to be 1ell above 2@8/n order to 1in typi"ally s"ore need to be 1ell above 2@8

&hat failed&hat failed ##Bro(en member > oints unglued$ Bro(en member > oints unglued$ %ideo taping%ideo taping

Careful e!amination of bro(en pie"esCareful e!amination of bro(en pie"es

/mproving/mproving  Design #Add a pie"e 1here it failed$Design #Add a pie"e 1here it failed$ Constru"tion #add not"hed oint > gusset plate$Constru"tion #add not"hed oint > gusset plate$

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&inners rom the Past 0ears&inners rom the Past 0ears

0ear 0ear  BridgeBridge&eight #gm$&eight #gm$

Brea(ingBrea(ingoad #gm$oad #gm$

Stru"turalStru"turalEffi"ien"yEffi"ien"y

28842884 23.723.7 78297829 49@.49@.

288:288: 2@.92@.9 @3@3 229.7229.7288@288@ 22.322.3 787787 ::::

28892889 7.@7.@ :33:33 @:2@:2

288288 24.24. 742@4742@4 @@@@28832883 23.723.7 7777:7777: 4949

288288 22.22. @48@48 297297