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1、Pre-calculationDuetothelossofconcretecover,thestiffnessofthecolumnandthebridgeisreducedby5%.TheoriginalstiffnessEoisknown,26Gpa.Then,thecurrentstiffnesscanbecalculatedasbelow:Ei=・(1一5%)=24.7GpaDuetothecorrosion,theoriginalallowablecompressivestress(20Mpa)isdecr
2、easedby30%.Then,thecurrentallowablecompressivestresscanbecalculatedasfollows:6mEZD0.4ma-adx=a0•(1—30%)=14Mpab・bFig.l-crosssectionofthebridgeandthecolumnAsthecresssectionFig.l・b-billustrates,theareamomentofInertiaofthebridge/canbecalculatedasshown:bh36xl3l=~n=12
3、=0.5m32)SuperpositionAnalysisandBridgeDeflectionCalculation:Fig.2illustratestheprofileofthewholestructureofthebridgeandtheloadsubjectedto.co」厂))-L-卄J))Fig.2Intermsofthissample,dividetheun讦ormdistributedload(deadweightofthebridgeandthedesignedcarryliveload)andth
4、esupportforceofthecolumnintotwopartstocalculatetheindividualandthesumdeflectionofthebridge.Fig.3BeamunderuniformlydistributedloadAccordingtothebeamdeflectionformula,thedeflection&undertheun讦ormlydistributedloadisshownblow:81=1384EJstheun讦ormlydistributedloadtha
5、tisthesumofthedeadweightofthebridgeandthedesiredliveloadcarryability.Inthiscase,usethemaximumload-carryingability,o)=300+120=420kN/mI】thelengthofthebridge・Fig.4BeamunderconcentratedloadatthecenterAccordingtothebeamdeflectionformula,thedeflectiongundertheconcent
6、ratedloadatthecenterisshownblow:248EJPisthesupportforceofthecolumn.ThetotaldeflectionofthebridgeisthesumofthedeflectionundertheconcentratedloadPandtheuniformlydistributedload.5a)l4Pl3A6=51+52=38W4W3)ConcreteReinforcementAssumption:Inthissituation,thesupportforc
7、eofthecolumnisanunknownvariable.Inordertoreinforcethecorrodedcolumn,thecriticalsituationneedtobeconsidered.Assumethatreinforcethecolumnbyusingthesamekindofmethodwiththebuildingmethodoftheoriginalcolumn,andthecolumnisunderthecriticalcompressedcondition,whichmean
8、s:E1=E2=24.7GpaBecausethedeformationofthecolumnequalsthetotaldeflect!onofthebridge,andthedeformationpi”ofthecolumnAS=—7.(l2theheightofthebridge)E2ASubstitutingtheequationsab
