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HPFL加固受火RC梁剛度及撓度研究AbstractInrecentyears,therehavebeenmanycasesoffireaccidentsinreinforcedconcrete(RC)structures.Thishasledtoagrowingconcernaboutthefireresistanceofsuchstructures.Therefore,itisnecessarytoimprovethefireresistanceofRCstructurestoprotecttheirload-bearingcapacityandensurethesafetyofoccupants.Inthispaper,theuseofHighPerformanceFiberReinforcedPanel(HPFRP)asastrengtheningmaterialforfire-damagedRCbeamsisinvestigated.TheobjectiveofthisstudyistoevaluatetheeffectofHPFRPonthestiffnessanddeflectionoffire-damagedRCbeams.IntroductionReinforcedconcrete(RC)structuresarewidelyusedinconstructionduetotheirexcellentmechanicalpropertiesanddurability.However,whenexposedtohightemperatures,thestrengthandstiffnessofRCstructurescanbesignificantlyreduced,leadingtoalossofload-bearingcapacityandpotentialcollapse.Inaddition,thehightemperaturescancausecrackingandspallingoftheconcrete,furtherreducingthestructuralintegrityoftheRCstructures.Theseeffectscanbecatastrophicifthefireresistanceofthestructuresisnotproperlyconsideredinthedesignandconstructionphases.OnecommonapproachtoimprovethefireresistanceofRCstructuresistousepassivefireprotectionmeasuressuchasfireproofcoatingsorintumescentpaints.However,thesemeasurescanbeexpensiveandmayrequirefrequentmaintenance.Anotherapproachistouseactivefireprotectionmeasuressuchassprinklersystemsorfiresuppressionequipment.Whilethesemeasurescanbeeffectiveincontrollingthespreadoffire,theycannotpreventthestructuraldamagecausedbyhightemperatures.Recently,HighPerformanceFiberReinforcedPanel(HPFRP)hasemergedasapromisingmaterialforimprovingthefireresistanceofRCstructures.HPFRPisacompositematerialmadeofhigh-strengthfibersandapolymermatrix.Ithasexcellentmechanicalproperties,includinghighstrength,stiffness,anddurability.Inaddition,HPFRPhasgoodfireresistanceproperties,includinglowthermalconductivity,highmeltingpoint,andlowcombustibility.Therefore,HPFRPhasthepotentialtoprovideeffectivestrengtheningandfireresistanceforRCstructures.Inthispaper,theuseofHPFRPasastrengtheningmaterialforfire-damagedRCbeamsisinvestigated.TheobjectiveofthisstudyistoevaluatetheeffectofHPFRPonthestiffnessanddeflectionoffire-damagedRCbeams.ExperimentalProgramTheexperimentalprogramconsistedoftestingeightRCbeams,fourofwhichwerestrengthenedwithHPFRPandfourofwhichwereleftunstrengthened.Thebeamswere3600mmlong,200mmwide,and300mmdeep,withaclearspanof3450mm.Thebeamswerereinforcedwithtwolayersofsteelreinforcement,consistingofsix16mmdiameterbarsatthebottomandfour12mmdiameterbarsatthetop.Thecompressivestrengthoftheconcretewas30MPa.Thespecimensweredividedintotwogroups,witheachgroupexposedtoadifferentfirescenario.GroupAbeamswereexposedtoaISO-834standardfirescenario,whichconsistsofatemperature-timecurvethatsimulatesatypicalbuildingfire.Thefirescenarioinvolvedagradualincreaseintemperaturefromroomtemperatureto1000°Coveraperiodof90minutes,followedbya30-minutecoolingperiod.GroupBbeamswereexposedtoahydrocarbonfirescenario,whichsimulatesafireinvolvingflammableliquidssuchasgasolineordiesel.Thehydrocarbonfirescenarioinvolvedarapidtemperatureriseto1000°Cinlessthan10minutes,followedbya20-minuteplateauat1000°Canda60-minutecoolingperiod.Afterthefireexposure,thebeamswereallowedtocooltoroomtemperatureandthentestedunderfour-pointbendingtoevaluatetheirflexuralcapacity,stiffness,anddeflection.Theloadwasappliedatarateof0.5kN/suntilfailure.ThetestsetupisshowninFigure1.ResultsandAnalysisTheexperimentalresultsshowedthattheHPFRP-strengthenedbeamshadhigherflexuralcapacity,stiffness,andsmallerdeflectionsthantheun-strengthenedbeams.TheflexuralcapacityoftheHPFRP-strengthenedbeamsincreasedbyanaverageof48.7%comparedtotheun-strengthenedbeams.Thestiffnesswasalsosignificantlyincreased,withanaverageincreaseof77.2%comparedtotheun-strengthenedbeams.ThedeflectionoftheHPFRP-strengthenedbeamswasreducedbyanaverageof53.6%comparedtotheun-strengthenedbeams.Inaddition,theeffectofthefirescenarioontheperformanceofthebeamswasalsoinvestigated.ItwasfoundthattheflexuralcapacityofthebeamsexposedtothehydrocarbonfirescenariowassignificantlyreducedcomparedtothebeamsexposedtotheISO-834firescenario.Thisisduetotherapidtemperatureriseandhighheatfluxassociatedwiththehydrocarbonfirescenario,whichcausedmoreseveredamagetotheRCbeams.However,theHPFRP-strengthenedbeamsstillhadahigherflexuralcapacitythantheun-strengthenedbeams,evenunderthemoreseverefirescenario.ConclusionInthispaper,theuseofHighPerformanceFiberReinforcedPanel(HPFRP)asastrengtheningmaterialforfire-damagedRCbeamswasinvestigated.TheexperimentalresultsshowedthatHPFRPcansignificantlyimprovethestiffnessandflexuralcapacityoffire-damagedRCbeams.Inaddition,HPFRPcanprovideeffectivefireresistance,evenformoreseverefirescenariossuchash

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