欧洲建筑防火规范(Introduction-to-Eurocode-Structural-Fire-Engineering)课件

IntroductiontoEurocodeStructuralFireEngineeringStructuralSteelworkEurocodes1Strain(%)0.51.01.52.0Stress(N/mm2)03002502001501005020°C200°C300°C400°C500°C600°C700°C800°CSteelsoftensprogressivelyfrom100-200°Cup.Only23%ofambient-temperaturestrengthremainsat700°C.

At800°Cstrengthreducedto11%andat900°Cto6%.Meltsatabout1500°C.Steelstress-straincurvesathightemperatures21.0012341000°C800°C20°C200°C400°C600°CStrain(%)NormalisedstressConcretealsolosesstrengthandstiffnessfrom100°Cupwards.Doesnotregainstrengthoncooling.

Hightemperaturepropertiesdependmainlyonaggregatetypeused.Concretestress-straincurvesathightemperatures3Stagesofanaturalfire-andthestandardfiretestcurveCooling….ISO834standardfirecurveIgnition-SmoulderingPre-FlashoverHeatingPost-Flashover1000-1200°CNaturalfirecurveTimeTemperatureFlashover5TheEC1(ISO834)standardfirecurve30010020004005006007008009001000060012001800240030003600Time(sec)GasTemperature(°C)5766757397818429456200400600800100012000120024003600Time(sec)GasTemperature(°C)TypicalEC1ParametricfirecurveExternalFireStandardFireHydrocarbonFireFireresistancetimesbasedonstandardfurnacetests-NOTonsurvivalinrealfires.EC1ParametricFiretemperature-timecurves.Basedonfireloadandcompartmentproperties(<500m2).Onlyallowedwithcalculationmodels.DifferentEC1

time-temperaturecurves7FurnacetestsonstructuralelementsFireTesting

Loadkeptconstant,firetemperatureincreasedusingStandardFirecurve.Maximumdeflectioncriterionforfireresistanceofbeams.Loadcapacitycriterionforfireresistanceofcolumns.ProblemsLimitedrangeofspansfeasible,simplysupportedbeamsonly.Effectsofcontinuityignored.Beamsfailby“run-away”.Restrainttothermalexpansionbysurroundingstructureignored.9Standardfireresistancefurnacetest1002003000120024003600Time(sec)Deflection(mm)10Standardfireresistancefurnacetest1002003000120024003600Time(sec)Deflection(mm)Span2/400dIfrate<span2/9000dStandardFireSpan/3011“Slim-floor”SystemsDownstandBeamShelf-angleBeamInherentfireprotectiontosteelbeams13Structuralfireprotection

CompositesectionsPassiveProtection–CompositesectionsDownstandBeamTraditionaldownstandbeam

topflangeupperfacetotallyshieldedbytheslab

14Structuralfireprotection

CompositesectionsPassiveProtection–CompositesectionsEncased

BeamBeamswithconcreteencasementHavehighfireresistance(upto180minutes).Involvecomplicatedconstructionofjoints.

Requireformwork.15LoadreductionfactorinfireRelativetoambient-temperaturedesignresistanceEither…..Relativetoambient-temperaturedesignload(moreconservative)Ormoreusefully…..17EstablishingFireResistance:StrategiesEurocodesallowfireresistancetobeestablishedinanyof3“domains”:Time: tfi.d>tfi.requLoadresistance: Rfi.d.t>Efi.d.tTemperature: cr.d>

dUsuallyonlydirectlyfeasibleusingadvancedcalculationmodels.Feasiblebyhandcalculation.Findreducedresistanceatdesigntemperature.MostusualsimpleEC3method.Findcriticaltemperatureforloading,comparewithdesigntemperature.18MaterialpropertiesSteel

Mechanical

(effectiveyieldstrength,elasticmodulus,...)Concrete

Thermal

(thermalexpansion,thermalconductivity,specificheat)

Mechanical

(compressivestrength,secantmodulus,...)

Thermal

(thermalexpansion,thermalconductivity,specificheat)19RftDegradationofsteelstrengthandstiffness0300600900120010080604020%ofnormalvalueTemperature(°C)RftEffectiveyieldstrength(at2%strain)SSElasticmodulusSSStrengthandstiffnessreductionsverysimilarforS235,S275,S355structuralsteelsandhot-rolledreinforcingbars.(SS)Cold-workedreinforcingbarsS500deterioratemorerapidly.(Rft)2110050020040060080010001200Temperature(°C)654321Strain(%)Strength(%ofnormal)StrainatmaximumstrengthDegradationofconcretestrengthandstiffnessNormal-weightConcreteAccuratefornormaldensityconcretewithsiliceousaggregates.Conservativefornormaldensityconcretewithcalcareousaggregates,.LightweightConcreteConservativeforlight-weightconcretes.Alltypestreatedthesame.Strengthreductionfactors22ConcretestrengthinheatingandcoolingStress-strainrelationshipincoolingfrom700°C(at400C)Stress-strainrelationshipinheatingphase(700C)515250,010,020,03Stress-strainrelationshipatambienttemperatureStress-strainrelationshipinheatingphase(400C)Stress-strainrelationshipaftercoolingfrom700°C(at20C)23la=45W/m°K(EC3simplecalculationmodel)Thermalconductivity(W/m°K)102030405060020040060080010001200Temperature(°C)Steelca=600J/kg°K(EC3simplecalculationmodel)OthersteelthermalpropertiesSpecificHeat(J/kg°K)5000020040060080010001200Temperature(°C)4000300020001000Steel25OtherconcretethermalpropertiesNCLCNCLCMayassumeconstantvalueforNC:1,60W/m.KMayassumeconstantvalueforNC:1000J/kg.Kcc*Specificheatcc(J/kg.K)400800100012002006001000°CThermalconductivitylc(W/m.K)2006001000°C12326SectionfactorAm/V-unprotectedsteelmembe