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Reviewofassessmentandrepairoffire-damagedRChighwaybridgesAbstract：Thispaperpresentsareviewoftheprogressoftheresearchandengineeringpracticeofassessmentandrepairoffire-damagedRChighwaybridges，basedonwhichexistingandpressingproblemsoftheevaluationmethodarepointedout．Atlast，Prospectforthedevelopmentofassessmentandrepairoffire-damagedhighwaybridgesisalsoproposed．Keywords：firedamage；assessment；repairtechniques；RCstructure；bridge1PrefaceFirescancausegreatstructuraldamagetobridgesandmajordisruptiontohighwayoperations．Theseincidentsstemprimarilyfromvehicleaccident(oftenoiltanker)fires，bridgesmightalsobedamagedbyfiresinadjacentfacilitiesandfromothercauses．Quiteafewofthem，thoughrarelyhappened，leadtoseverestructuraldamageorcollapseandcasualty．OnJune2，2008，firedisasterbrokeoutunderthe18thspanofNanjingYangtzeRiverBridgeandlastedforapproximate75min．Duringthefire’sdevelopmentandextinguishment，thestructureexperiencedthesharpriseandfallintemperaturecausingseveredamagetofire-strickensegments．OnApril29，2007，agasolinetankeroverturnedontheconnectorfromInterstate8OtoInterstate880inCalifornia．Theintenseheatfromthesubsequentfuelspillandfireweakenedthestee1underbellyoftheelevatedroadway,collapsingapproximately165feetofthiselevatedroadwayontoasectionofI—880below．OnMarch25，2004，Connecticut，UnitedStates，atankertruckcarryingfuelswervedtoavoidacarandoverturned，dumping8000gallonsofhomeheatingoilontotheHowardAvenueoverpass．TheconsequenttoweringinfernomeltedthebridgestructureandcausedthesouthboundlanestosagseveralfeetUndocumentednumberofbridgefiresoccurringthroughouttheworldeachyearcausevaryingdegreesofdisruption，repairactions，andmaintenancecost．Althoughfirescauseddamagetothebridgestructures,somebridgescontinuetofunctionafterproperrepairandretrofit．Stillinsomesituationstheyhavetoberepairedforthecauseoftrafficpressureeventhoughsupposedtobedismantledandreconstructed．However,inothercases，structuresareseverelydamagedinthefiredisasterandfailtofunctionevenafterrepair，orthecostsofrepairandretrofitoverweightheirreconstructioncostsoverwhelminglyeveniftheyarerepairable，underwhichsituationreconstructionservesasapreferableoption．Thereforein—situinvestigationandnecessarytestsandanalysesshouldbeconductedtomakecomprehensiveassessmentoftheresidualmechanicalpropertiesandworkingstatusesafterfireandtoevaluatethedegreesofdamageofmembersandstructures,inreferencetowhichdecisionsaremadetodeterminewhetherFiredamagedstructuresshouldberepairedordismantledandreconstructed．Urgentneedfromengineeringpracticehighlightedthenecessitytounderstandthesusceptibilityandseverityoftheseincidentsaswel1astoreviewavailableinformationonmitigationstrategies，damageassessments，andrepairtechniques.2ProgressinResearchandEngineeringPractice2.1ProcessesofAssessmentandRepairofFiredamagedBridgeStructureInChinaandmostcountriesintheworld，mosthighwaybridgesarebuiltinRCstructure．AndthepracticeoftheassessmentandrepairtechniquesofbridgestructureafterfiredirectlyrefertothatofRCstructure，which，todate，domesticandforeignscholarshavemadegreatamountofresearchon，withtheirtheoriesandpracticesbeingincreasinglymature.Asfortheassessmentandrepairoffire-damagedreinforcedconcretestructures，therearetwomainstreamassessmentprocessesinworld．CountriesincludingUnitedStates，UnitedKingdomandJapanadopttheassessmentprocessstipulatedbyTheBritishConcreteSociety.Thisprocessgratestheseverityoffiredamageofconcretestructureintofourdegreesaccordingtothedeflection，damagedepth，crackingwidth,color，andloadingcapacityvariationoffire-damagedstructuresandadoptfourcorrespondingstrategies(includingdemolish，strengthenaftersafetymeasures，strengthen.andstrengthenindamagedsegments)todealwiththemaccordingly．Ingeneral，thisprocessisaqualitativemethodandconsidered，however，notquantityenough.InChineseMainlandandTaiwan，theprevailingasassessmentandrepairprocessoffiredamagedincorporatesfollowingsteps：Incomparisonthisprocessismoredetailed．(1)ConductIn-situinspections，measurements，andtestsincludingcolorobservation，concreteobservation，degreeofrebarexposureobservation，crackingmeasurement，deflectionmeasurement，variousdestructiveandnondestructivetestmethodsasgroundsforassessmentoffire—damagedstructures．Inassessmentofthepost-firemechanicalpropertiesoffire—damagedstructures，historicalhighesttemperatureandtemperaturedistributionofstructureduringthefireserveasdecisivefactors．Thecommonmethodstodeterminethemincorporatepetrographicanalysis，ultrasonicmethod，Reboundmethod，IgnitionLossmethod，coretest，andcolorobservationmethod(2)calculatetodeterminewhetherthefire-damagedstructurecanmeetthedemandofstrengthanddeflectionunderworkingloadsafterfireusingmechanicalpropertiesofrebarandconcretebeforeandafterfirebasedonthehistoricalhighestandtemperaturedistributionofstructuresobtainedfromstepone．Therearetwomainmethodstoevaluatethepost-fireperformanceoffire-damagedstructures：FEMmethodandRevisedClassicMethod．(3)Onthebasisoftestandcalculationresultsobtainedfromsteptwo，takecorrespondingrepairstrategiesandparticularmethodstostrengthenthefire-damagedstructures.2．2RepairTechniquesFor