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1、外文资料TheTenthEastAsia-PacificConferenceonStructuralEnghieerhigandConstructionAugust3-5f2006,Bangkok,ThailandStructuralRehabilitationofConcreteBridgeswithCFRpcomposites-PracticalDetailsandApplicationsRiyadS.ABOUTAHA1,andNuttawatCHUTARAT2ABSTRACT:Manyoldexistingbridgesarestillactiveinthevarioushighwayt
2、ransportationnetworks,carryingheavierandfastertrucks,inallkindsofenvironments.Water,salt,andwindhavecauseddamagetotheseoldbridges,andscarcityofmaintenancefundsHasaggravatedtheirconditions.Oneattempttorestoretheoriginalcondition;andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinfor
3、cedpolymer(CFRP)Composites.ThereappeartobeverylimitedguidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Inthispaper,guidelinesfornondestructiveevaluation(NDE),nondestructivetesting(NDT),andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.Theeffectofdetailingonduct
4、ilityandbehaviorofCFRPstrengthenedconcretebridgesarealsodiscussedandpresented.KEYWORDS:Concretedeterioration,corrosionofsteel,bridgerehabilitation,CFRPcomposites.!IntroductionThereareseveraldestructiveexternalenvironmentalfactorsthatlimittheservicelifeofbridges.Thesefactorsincludebutnotlimitedtochem
5、icalattacks,corrosionofreinforcingsteelbars,carbonationofconcrete,andchemicalreactionofaggregate.Ifbridgeswerenotwellmaintained,Ihesefactorsmayleadtoastructuraldeficiency,whichreducesthemarginofsafety,andmayresultinstructuralfailure.Inordertorehabilitateand/orstrengthendeterioratedexistingbridges,th
6、oroughevaluationshouldbeconducted.Thepurposeoftheevaluationistoassesstheactualconditionofanyexistingbridge,andgenerallytoexaminetheremainingstrengthandloadcarrycapacityofthebridge.7AssociateProfessor,SyracuseUniversity,U.S,A.2Lecturer,SripatumUniversity,Thailand.Oneattempttorestoretheoriginalconditi
7、on,andtoextendtheservicelifeofconcretebridgesisbytheuseofcarbonfiberreinforcedpolymer(CFRP)composites.InNorthAmerica,EuropeandJapan,CFRPhasbeenextensivelyinvestigatedandapplied.SeveraldesignguideshavebeendevelopedforstrengtheningofconcretebridgeswithCFRPcomposites.However,thereappeartobeverylimitedg
8、uidesonrepairofdeterioratedconcretebridgeswithCFRPcomposites.Thispaperpresentsguidelinesforrepairofdeterioratedconcretebridges,alongwithproperdetailing.Evaluation,nondestructivetesting,andrehabilitationofdeterioratedconcretebridgeswithCFRPcompositesarepresented.SuccessfulapplicationofCFRPcompositesr
9、equiresgooddetailingastheforcesdevelopedintheCFRPsheetsaretransferredbybondattheconcrete-CFRPinterface.TheeffectofdetailingOnductilityandbehaviorofCFRPstrengthenedconcretebridgeswillalsobediscussedandpresented.2DeterioratedConcreteBridgesDurabilityofbridgesisofmajorconcern.Increasingnumberofbridgesa
10、reexperiencingsignificantamountsofdeteriorationpriortoreachingtheirdesignservicelife.Thisprematuredeteriorationconsideredaproblemintermsofthestructuralintegrityandsafetyofthebridge.Inaddition,deteriorationofabridgehasaconsiderablemagnitudeofcostsassociatedwithit.Inmanycases,therootofadeteriorationpr
11、oblemiscausedbycorrosionofsteelreinforcementinconcreteStructures.Concretenormallyactstoprovideahighdegreeofprotectionagainstcorrosionoftheembeddedreinfbrcement.However,corrosionwillresultinthosecasesthattypicallyexperiencepoorconcretequality,inadequatedesignorconstruction,andharshenvironmentalcondit
12、ions.Ifnottreatedadurabilityproblem,e.g.corrosion,mayturnintoastrengthproblemleadingtoastructuraldeficiency,asshowninFigurel.FigurelCorrosionofthesteelbarsisleadingtoastructuraldeficiency3Non-destructiveTestingofDeterioratedConcreteBridgePiersInordertodesignasuccessfulretrofitsystem,theconditionofth
13、eexistingbridgeshouldbethoroughlyevaluated.Evaluationofexistingbridgeelementsorsystemsinvolvesreviewoftheasbuiltdrawings,aswellasaccurateestimateoftheconditionoftheexistingbridge,asshowninFigure2.Dependingonthepurposeofevaluation,non-destructivetestsmayinvolveestimationofstrength,saltcontents,corros
14、ionrates,alkalinityinconcrete,etc.Figure2VisibleconcretedistressmarkedonanelevationofaconcretebridgepierAlthoughmostofthenon-destructivetestsdonotcauseanydamagetoexistingbridges,someNDTmaycauseminorlocaldamage(e.g.drilledholes&coring)thatshouldberepairedrightaftertheNDT.Thesetestsarealsoreferredtoas
15、partialdestructivetestsbutfallundernon-destructivetesting.Inordertoselectthemostappropriatenon-destructivetestforaparticularcase,thepurposeofthetestshouldbeidentified.Ingeneral,therearethreetypesofNDTtoinvestigate:(1)strength,(2)Otherstructuralproperties,and(3)qualityanddurability.Thestrengthmethods
16、mayinclude;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(acquametermoisturemeter),cracking(visualtest/impactecho/ultrasonicpulsevelocity),delamination(hammertest/ultrasoni
