EG1109Report1024 tan yang 的冲突副本 1025Word文档下载推荐.docx

EG1109Report1024 tan yang 的冲突副本 1025Word文档下载推荐.docx

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IshaanPakrasi（A0117853B）

INDEX

PageNo:

3-5

6

7

8

9

11-13

15

17

Introduction

Design

AdvantagesVSDisadvantages

Calculation:

TrafficLoad

DeckMass

TrussMembers

TableA:

CalculationofMaxForces

References

Task:

ToperformapreliminarydesignforatrussbridgespanningacrosstheSingaporeRiver.Thedistancebetweenthe2banksisgivenas20m,theheightofthebridgeisrestrictedtobelessthan5mabovethebankand2mbelowthebank.

Thebridgewillsupportvehiculartrafficflowthatconsistsof4lanes.Inourcalculations,weusedtheweightof12fullyladenclass4vehiclestoestimatethemaximumhighesttrafficloadingthebridgewillfaceinitslifetime.

Thebridgewillsupportedatbankbyapinsupportononeendandarollersupportattheother.ThedeckofourbridgewillbeconstructedusingreinforcedconcretebasedoffSingapore’sconstructionstandards.Thedeckwillalsoincludeasteelgridinthecenterofthedecktoreinforcetheconcretedeck.

ThedesignofourbridgeissimilartotheiconicHoweTrussBridgestyle,whichwasinventedin1840byWilliamHowe（Nakate,2013）.TheHowetrussismadeupofdiagonalandverticalmembers.Inthisbridge,thediagonalmembersslopetowardsthecenterinanupwardmannerandthediagonalwebmembersareincompressionwhiletheverticalwebmembersareintension（Boon,2011）.

AccordingtoCalvert（2004）,comparedtoothertrussdesigns,theHoweTrusshastheadvantageofsimplicitywithstrength.Unlikeotherinventorsofthetime,whoaddedsuperfluouselementstotheirdesignsonthebasisoffaultyunderstanding,WilliamHowereducedthenumberofmemberstoaminimum.Ifanymemberfails,thewholebridgecollapses.Thisimpliesthattheforcesineachmembercanbeuniquelydetermined,andthemembercanbeproportionedtobearitsloadsafely,i.e.thestructureisstaticallydeterminateandtheforcesdonotdependonthedetailsofconstruction.IntheoriginalHoweTruss,allmemberswereofwoodexceptfortheverticalties,whichwereironrodsthreadedattheendsandsecuredbynuts.Thebridgewasverysuccessful.

PicturesofexamplestheHoweTrussinuseareshownbelow–

Above:

TheJayBridgeisawoodencoveredbridgethatspanstheeastbranchofthe

AusableRiverinJay,inEssexCounty,NewYork,USA.ItiseligibletobelistedintheNationalRegisterofHistoricPlaces.Ittheonlyoneofthe29coveredbridgesinNewYorkStatethatisintheAdirondacks.

BNHoquiamRiverSwingBridge

（BRIDGEHUNTER.COM,2013）

Advantages

Disadvantages

∙Simplebutstillefficientandstrong

∙Minimummembers

∙Lessmaterialusedascomparedtootherelaboratetrussdesigns

∙Memberscanbeeasilyreplacedastrussmembersarestraightandofrelativelyequallengths

∙Lessstableoverlongdistances（howeverforourbridgedistanceisrelativelyshort）

∙Noteconomicaltousesteelmemberstohandlecompressiveforces.

Calculations

TrafficLoad

Forthe4lanebridge,eachlanewillbe3mwideandtherewillbeasidelaneofwidth1.5mforpedestriansorbrokendownvehicles.Thelengthofthelaneswillbe20mlong.

Ourtrafficloadisbasedoneachlanebeingtakenupby3Class4Vehiclesofmaxladenweightoflessthan7250kg（ClassesofDrivingLicence,2013）.

Massoftrafficload:

Mass=7250x12=87000kg

W=87000xg=853470N

Deck

Thedeckismadeupofconcreteslab0.25mthickwithreinforcedsteelgridinthecenterwithadiameterof32mm.

Concreteslab:

Volume=（0.25mX15mx20）–1m3=74m3（wetakeaway1m3asvolumeofrodisas1m3）

DensityofConcrete=2400kg/m3

Massofconcreteslab=2400x74=177600kg

SteelRod:

Length=（40x15）+（30x20）=1200m

Volume=（0.016）2xπx1200=0.965m3

Mass=0.965m3x7850kg/m3=7575kg（roundof）

Totalmassofdeck=177600+7575=185000kg

Weight=185000x9.81=1814850N

TotalWeightofTrafficLoadandDeck=1814850+853470=2668320N=2670000N（3sf）

TrussMembers:

Forthewholebridge,

Fx=0

Fy=0=>

Ay+Ey=Wtot

ForjointA

=>

Ey=

Ax=Ey=

ForjointF

ForjointE（sameasjointA）,jointH（sameasjointF）

ForjointC,

ForjointG,

Fromthiscalculations,

MaximumTensileForcemembersareFBC,FCDandFCGandthemagnitudeisequaltoWtotwhichisthetotalweightofthebridge.

MaximumCompressiveForcemembersareFBGandFDGwiththemagnitudeof

.

TableA

AnalysisofTableA

TableAtakesinthedifferentrangesofdiameteroftrussandthethickness.Withthisvaluesweareabletocalculatetheweightofthetrussmembersandthustotalweightofthebridge,Wtot.WithWtotwecanthencalculatethemaximumcompressiveandtensileforcesinthetrussasshownabove.Next,wetookthoseforcesandmultiplieditwiththesafetyfactorof1.2andcalculatedthestressofthosemaximumforces.Wethencomparethisstressvalueswiththeacceptedyieldstressof0.85yieldstrengthfortensileforcesand0.7yieldstrengthforcompressiveforces.Ourgrouphaschosenthediameterof406.4mmandthicknessof16mmbecauseitproducesthesmallestdifferencebetweenmaximumcompressive/tensilestressesandacceptablestressasdefinedbytheyieldstrength.

Dimensions:

d=406.4mm

t=16mm

References:

Boon,G.（2011）.ModelBridgeDesign.Retrievedfrom

BRIDGEHUNTER.COM.（2013）.HoweTruss.Retrievedfrom

Calvert,J.B.（2004）.EarlyEvolutionofTrusses.Retrievedfrom

http:

//mysite.du.edu/~jcalvert/tech/truss.htm

ClassesofDrivingLicence.（2013）Retirvedfrom

//driving-in-singapore.spf.gov.sg/services/driving_in_singapore/services/information.html

Nakate,S.（2013）.TrussBridgeDesign.Retrievedfrom