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1外文资料TheTenthEastAsia-PacificConferenceonStructuralEngineeringandConstructionAugust3-5,2006,Bangkok,ThailandStructuralRehabilitationofConcreteBridgeswithCFRPComposites-PracticalDetailsandApplicationsRiyadS.ABOUTAHA1,andNuttawatCHUTARAT2ABSTRACT:Manyoldexistingbridgesarestillactiveinthevarioushighwaytransportationnetworks,carryingheavierandfastertrucks,inallkindsofenvironments.Water,salt,andwindhavecauseddamagetotheseoldbridges,andscarcityofmaintenancefundshasaggravatedtheirconditions.Oneattempttorestoretheoriginalcondition;andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinforcedpolymer(CFRP)composites.ThereappeartobeverylimitedguidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Inthispaper,guidelinesfornondestructiveevaluation(NDE),nondestructivetesting(NDT),andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.TheeffectofdetailingonductilityandbehaviorofCFRPstrengthenedconcretebridgesarealsodiscussedandpresented.KEYWORDS:Concretedeterioration,corrosionofsteel,bridgerehabilitation,CFRPcomposites.1IntroductionThereareseveraldestructiveexternalenvironmentalfactorsthatlimittheservicelifeofbridges.Thesefactorsincludebutnotlimitedtochemicalattacks,corrosionofreinforcingsteelbars,carbonationofconcrete,andchemicalreactionofaggregate.Ifbridgeswerenotwellmaintained,thesefactorsmayleadtoastructuraldeficiency,whichreducesthemarginofsafety,andmayresultinstructuralfailure.Inordertorehabilitateand/orstrengthendeterioratedexistingbridges,thoroughevaluationshouldbeconducted.Thepurposeoftheevaluationistoassesstheactualconditionofanyexistingbridge,andgenerallytoexaminetheremainingstrengthandloadcarrycapacityofthebridge.1AssociateProfessor,SyracuseUniversity,U.S.A.2Lecturer,SripatumUniversity,Thailand.2Oneattempttorestoretheoriginalcondition,andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinforcedpolymer(CFRP)composites.InNorthAmerica,EuropeandJapan,CFRPhasbeenextensivelyinvestigatedandapplied.SeveraldesignguideshavebeendevelopedforstrengtheningofconcretebridgeswithCFRPcomposites.However,thereappeartobeverylimitedguidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Thispaperpresentsguidelinesforrepairofdeterioratedconcretebridges,alongwithproperdetailing.Evaluation,nondestructivetesting,andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.SuccessfulapplicationofCFRPcompositesrequiresgooddetailingastheforcesdevelopedintheCFRPsheetsaretransferredbybondattheconcrete-CFRPinterface.TheeffectofdetailingonductilityandbehaviorofCFRPstrengthenedconcretebridgeswillalsobediscussedandpresented.2DeterioratedConcreteBridgesDurabilityofbridgesisofmajorconcern.Increasingnumberofbridgesareexperiencingsignificantamountsofdeteriorationpriortoreachingtheirdesignservicelife.Thisprematuredeteriorationconsideredaproblemintermsofthestructuralintegrityandsafetyofthebridge.Inaddition,deteriorationofabridgehasaconsiderablemagnitudeofcostsassociatedwithit.Inmanycases,therootofadeteriorationproblemiscausedbycorrosionofsteelreinforcementinconcretestructures.Concretenormallyactstoprovideahighdegreeofprotectionagainstcorrosionoftheembeddedreinforcement.However,corrosionwillresultinthosecasesthattypicallyexperiencepoorconcretequality,inadequatedesignorconstruction,andharshenvironmentalconditions.Ifnottreatedadurabilityproblem,e.g.corrosion,mayturnintoastrengthproblemleadingtoastructuraldeficiency,asshowninFigure1.3Figure1Corrosionofthesteelbarsisleadingtoastructuraldeficiency3Non-destructiveTestingofDeterioratedConcreteBridgePiersInordertodesignasuccessfulretrofitsystem,theconditionoftheexistingbridgeshouldbethoroughlyevaluated.Evaluationofexistingbridgeelementsorsystemsinvolvesreviewoftheasbuiltdrawings,aswellasaccurateestimateoftheconditionoftheexistingbridge,asshowninFigure2.Dependingonthepurposeofevaluation,non-destructivetestsmayinvolveestimationofstrength,saltcontents,corrosionrates,alkalinityinconcrete,etc.Figure2VisibleconcretedistressmarkedonanelevationofaconcretebridgepierAlthoughmostofthenon-destructivetestsdonotcauseanydamagetoexistingbridges,someNDTmaycauseminorlocaldamage(e.g.drilledholes&coring)thatshouldberepairedrightaftertheNDT.Thesetestsarealsoreferredtoaspartialdestructivetestsbutfallundernon-destructivetesting.Inordertoselectthemostappropriatenon-destructivetestforaparticularcase,the4purposeofthetestshouldbeidentified.Ingeneral,therearethreetypesofNDTtoinvestigate:(1)strength,(2)otherstructuralproperties,and(3)qualityanddurability.Thestrengthmethodsmayinclude;compressivetest(e.g.coretest/reboundhammer/ultrasonicpulsevelocity),surfacehardnesstest(e.g.reboundhammer),penetrationtest(e.g.Windsorprobe),andpullouttest(anchortest).Otherstructuraltestmethodsmayinclude;concretecoverthickness(cover-meter),locatingrebars(rebarlocator),rebarsize(somerebarlocators/rebardatascan),concretemoisture(acquameter/moisturemeter),cracking(visualtest/impactecho/ultrasonicpulsevelocity),delamination(hammertest/ultrasonicpulsevelocity/impactecho),flawsandinter