桥梁工程毕业设计外文翻译.docx

桥梁工程毕业设计外文翻译.docx

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桥梁工程毕业设计外文翻译

Reviewofassessmentandrepairoffire-damagedRChighwaybridges

Abstract：

Thispaperpresentsareviewoftheprogressoftheresearchandengineeringpracticeofassessmentandrepairoffire-damagedRChighwaybridges，basedonwhichexistingandpressingproblemsoftheevaluationmethodarepointedout．Atlast，Prospectforthedevelopmentofassessmentandrepairoffire-damagedhighwaybridgesisalsoproposed．

Keywords：

firedamage；assessment；repairtechniques；RCstructure；bridge

1Preface

Firescancausegreatstructuraldamagetobridgesandmajordisruptiontohighwayoperations．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．Theconsequenttoweringinfernomeltedthebridgestructureandcausedthesouthboundlanestosagseveralfeet

Undocumentednumberofbridgefiresoccurringthroughouttheworldeachyearcausevaryingdegreesofdisruption，repairactions，andmaintenancecost．Althoughfirescauseddamagetothebridgestructures,somebridgescontinuetofunctionafterproperrepairandretrofit．Stillinsomesituationstheyhavetoberepairedforthecauseoftrafficpressureeventhoughsupposedtobedismantledandreconstructed．However,inothercases，structuresareseverelydamagedinthefiredisasterandfailtofunctionevenafterrepair，orthecostsofrepairandretrofitoverweightheirreconstructioncostsoverwhelminglyeveniftheyarerepairable，underwhichsituationreconstructionservesasapreferableoption．Thereforein—situinvestigationandnecessarytestsandanalysesshouldbeconductedtomakecomprehensiveassessmentoftheresidualmechanicalpropertiesandworkingstatusesafterfireandtoevaluatethedegreesofdamageofmembersandstructures,inreferencetowhichdecisionsaremadetodeterminewhetherFiredamagedstructuresshouldberepairedordismantledandreconstructed．Urgentneedfromengineeringpracticehighlightedthenecessitytounderstandthesusceptibilityandseverityoftheseincidentsaswel1astoreviewavailableinformationonmitigationstrategies，damageassessments，andrepairtechniques.

2ProgressinResearchandEngineeringPractice

2.1ProcessesofAssessmentandRepairofFiredamagedBridgeStructure

InChinaandmostcountriesintheworld，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.

2．2RepairTechniques

Fortherepairoffire—damagedbridge，properrepairmethodsshouldbetakenaccordingtothedegreeandrangeofthestructure’sdamage．Meanwhilethesafetyandeconomyoftherepairmethodsshouldbeconcernedwithbyavoidingdestructingtheoriginalstructure，preservingthevaluablestructuralmembers，andminimizingunnecessarydemolishmentandreconstruction。

Commonrepairtechniquesarelistedasfollows．

（1）Fire-damagedconcreteReplacement

Thereplacementoffire—damagedconcreteisthemostcommontechniqueindamagedconcreterepair．Iftheconcretestructureisdamagedonlywithintheconcretecover，itispreferabletoremovethefire—damagedconcretefromthestructuremakingtherebarexposedandtomakeuptheremovedpartbymeansofrecastingorconcretespraying．Ifthedisplacementofthestructureexceedsthecontrolledvalueortheembeddedrebarisbuckled，thedamagedstructureshouldbeotherwisehandled。

（2）CFRPstrengthening

CFRPmaterialshavestrongtensilestrengthandelasticityaswellasexcellentworkabilityanddurabilityandarewidelyappliedinengineeringpracticeinrecentyears．CFRPmaterialsareusedtoboosttheloadingcapacitybyadheringthemtotheedgeoftensileregiontoreplacethereinforcedrebar.CFRPareespeciallysuitablefortheprojectscallingforboostofloadingcapacitywhilenoextraweightisallowed．

（3）StructuralmemberReplacement

Forslabbridgesandgirderbridges,thedecksofthebridgearemadeofparallelgirdersorthickslabs.Onconditionthatpartofstructuralmemberisseverelydamagedinthefiresothatit’sbeyondrepairortherepaircostoverweighanewone，itispreferabletoreplacethe

damagedspanswithnewgirdersorslabs．Thoughappearstoberelativelyhighincost,thismethodservesasreliableandeffectivewayinengineeringpractice

2．3CaseStudyofAssessmentandRepairTechniquesoffire-damagedbridges

Somedomesticandforeignscholarshaveconductedaseriesofstudiesontheinspection，assessment，andrepairtechniquesoffiredamagedbridgesintheengineeringpracticebydifferentassessmentstandardsandprocessesonthecase—by—casebasisusingavarietyoffieldand

laboratoryevaluationmethods，includingbothdestructiveandnondestructivetesting

Literatureemployedvisualinspectionandmaterialtestingincludingcompressivestrengthtestingandpetrographicanalysis（pastedepth，microcracking，colorchange）onafire-damagedbridge，basedonwhich1oadratinganalysiswasperformedusingreducedgirderanddecksections．Literaturemadequalitativesafetyevaluationontwofire-damagedbridgestructuresusingthereboundmethod，coretests，carbonizationdepthmeasurement，concretecovermeasurement，deflectionmeasurement，andappearanceobservation．Literatureusethecombinationofultrasonicmethodandreboundmethodtodeterminethehistoricalhighesttemperatureofstructuresinfire，basedonwhichstiffnessandstrengthoftwofiredamagedstructuresaredeterminedtomakesafetyevaluationsonthem．AndthenCFRPandstructuraladhensiveareusedtostrengthenthefire—damagedsegmentsrespectively．Literaturemadeasafetyevaluationonaprestressedreinforcedconcreteslabbridge，thefire—directly—strickensegmentsofwhichareseverelyspalledandcarbonizedwithembeddedrebarsandprestressedstrandsexposed．Itsrubberisolatorswerealsohighlycarbonized．Theresearchertookthecoretestsandinferredthatlocalsegmentsoftheslabswereseverelydamagedandtheprestresshadbeenlost．Meanwhile，theresearcherconductedaseriesofdynamictestsonthedamagedbridgeandpresumedthatthevariationofthecomprehensiveperformanceofthebridgestructureafterfirewasinsignificantinreferencetotheresultsofthedynamictests.Theresearcherproposedtoreplacetheseverelydamagedslabsfromtheperspectiveofdurabilityandsafety．Literaturemadethedamageassessmentandrepairworkonafire-damagedT-shapedprestressedbeambridge．Thefiredisasterwasderivedfromtheleakageofaoiltankerandthentheburningoilwasspreadtotheunderbellyofthebridge．