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nbr_6123_PFIN(巴西风荷载).doc

nbr_6123_PFIN(巴西风荷载)

zhang小娟j
2017-10-10 0人阅读 举报 0 0 暂无简介

简介:本文档为《nbr_6123_PFIN(巴西风荷载)doc》,可适用于综合领域

nbrPFIN(巴西风荷载)ForcesinbuildingsduetowindProcedureOrigin:ProjectNBCB–BrazilianCivilConstructionCommitteeCE:CommissionforStudyofForcesinBuildingsDuetoWindNBRBuildingconstructionBasesfordesignofstructuresWindloads–ProcedureDescriptors:WindBuildingConstructionIncorporatestheErrataNrofDECReprintingofNBofDECKeywords:WindBuildingConstructionpagesSUMMARYObjectiveLiteralconventionsDefinitionsProcedureforthecalculationofforcesduetowindinbuildingsVelocitycharacteristicofwindAerodynamiccoefficientsforbuildingscurrentsForcecoefficientsforprismaticandreticulatedbarsForcescoefficientsforwalls,platesandisolatedcoveringsDynamiceffectsduetoatmosphericturbulenceANNEXA–StandardlizedvelocitySandtimeperiodsANNEXB–StatisticalFactorSfortheprobabilityPandusefullifeofabuildinginmyearsmANNEXCLocalizationandaltitudeofthemeteorologicalstationsANEXODDeterminationoftheinternalpressurecoefficientANEXOEAerodynamiccoefficientforcurvedcoveringsANEXOF–additionalinformationANEXOG–SurroundingbuildingsEffectsANEXOH–DynamicisseateddirectlyovertheterrainTypicaldistributionsoftheisobarsaregiveninFigureThereisnooverpressurezoneinthecupolaswithfdlessthanandwithawallheighthigherthandELimitvaluesofthepositive(overpressures)andnegative(suctions)externalpressurecoefficientsaregiveninTableforintermediaterelationsoffdandofhd,thecoefficientsareobtainedbyinterpolationsa)ElevationWindb)TopView:isobariclinesoftheexternalpressurecoefficientsforfd=Windc)TopView:isobariclinesoftheexternalpressurecoefficientsforfd=FigureCupolaoverterrain,isobariclinesTableLimitvaluesoftheexternalpressurecoefficients,c,andofthesustainingcoefficients,CpesCupolasovertheterraincpefdCsSuperimpositionSuctionWinda)elevationb)Topview:isobarsoftheexternalpressurecoefficientsforfd=andhd=Windc)Topview:isobarsoftheexternalpressurecoefficientsforfd=andhd=FigureCupolasovercylindricalwallsIsobariclinesTableLimitvaluesoftheexternalpressurecoefficients,cCupolasovercylindricalwallspeCpefdhdWindwardlaterallyatthetopANNEXF–AdditionalInformationResultsofrecenttrials,whichareapplicabletobuildingswithrelationshipsbetweentheindicateddimensionsintherespectivetables,arepresentedinthisAnnexExtrapolationscanbemadeforproportionsclosetotheseThetrialswereexecutedwithsimulationofthemaincharacteristicsofnaturalwinds,andcanbeappliedtoanycategoryofterrain,withtolerableerrorSurfacesonwhichconsiderablepressurevariationsoccurweresubdivided,andshapecoefficientsCaregivenforeeachoneofthepartsForhighsuctionzones,theaveragevalues(caverage)ofpressurecoefficientsarepresented,whichshouldonlypebeusedforthecalculationofthewindforcesintherespectivezones,applyingtothedimensioning,theverificationandanchoringofcoveringelementsandofthesecondarystructureRemarksmadeinarevalidTableExternalpressureandshapecoefficientsforroofswithtwosymmetricalgableswithacentralgutter,inbuildingswitharectangularplanview(useScorrespondingtoheighth)TableExternalpressureandshapecoefficientsformultiplegableequalsectionroofswithaverticalgable,Wind(Takethesmallestvalue)(Takethesmallestvalue)Thebandsparalleltothelongersideofthepavillion(withwidthy)includetheverticalfaces(a*,c*,m*x*)InclinationwindofincidencFirstOtherLastsectionFirstcaveragepeTheroofeangle:intermediateintermediatesectionθsectionsectionα=,inthesecondintermediatesction*C=,inthelastintermediatesction*CeewindInclinationofCdistanceeincidenceTheroofangle:θαNotes:a)Therelationbetweenthedimensionsaxbxhofthetestedmodelsisthefollowing:forθ=and:xxandxxforθ=:xx,xx,xxandxxb)FrictionForces:forα=:thehorizontalfrictionforcesshouldbedeterminedinaccordancewithforα=and:F'=C'qab,whereC'=fora=andC'=forα=(:angleindegrees)ANNEXG–ProximityEffectsTherearecertainsituationsinwhichitisnecessarytoconsidertheinfluenceofbuildingssituatedinproximitytotheonebeingstudiedThesebuildingscancauseanincreaseinthewindforcesinthreedifferentmodes:GBytheVenturieffectNeighboringbuildingscan,bytheirdimensions,shapeandorientation,cause"funneling"ofthewind,acceleratingtheairflow,withconsequentalterationinthepressuresThiseffectappearsmainlyinbuildingswhichareveryclose,inwhichcasenegativepressurecoefficients(suctions)havebeenobservedexceeding,inmodulus,avalueofThesesuctionpointsareverifiedontheconfrontingwallsofthetwobuildings,closetothewindwardedgeGBydeflectionofthewindintheverticaldirectionTallbuildingsdeflectdownpartofthewindthatisincidentontheirwindwardfaçade,increasingthevelocityinzonesclosetothegroundLowerbuildings,situatedinthesezones,canhavethewindloadsincreasedbythiseffect,withtheshapecoefficientsreachingvaluesbetween–e–,GBythewaketurbulenceAbuildingsituatedontheleewardsideofanothercanbegreatlyaffectedbytheturbulencegeneratedonthewakeofthewindwardbuilding,whichcancauseconsiderabledynamiceffects("gusteffects")andalterationinthepressuresTheseareparticularlyimportantinbuildingswithroofsandcoveringpanelsmadeoflightmaterialsGDeterminationoftheproximityeffectsItisnotpossibletoindicatenumericvaluesforproximityeffectsinagenericandnormativemannerTheseeffectscanbedeterminedbytestsinwindtunnels,inwhichtheproximityconditionsandthenaturalwindcharacteristicswhichcaninfluencetheresultsarereproducedTheproblemisworsenedbythepossibilityofunfavorablealterationsintheproximityconditionsduringtheusefullifeofthebuildingbeingstudiedAnapproximateindicationoftheincreasesthattheaerodynamiccoefficientscansufferduetotheproximityeffectswillbegivenbelowGiven:s=spacingbetweentheplanesoftheconfrontingfacesoftwotallneighboringbuildings,whereaxbaretheplanviewdimensionsofthebuildings(axbbetweenxandx)d*=thesmallestofthetwodimensions:smallestsidebsemidiagonalFV=proximityeffectfactor,definedbytherelationship:CbuildingwithneighborhoodCatisolatedbuilding,caverage,C)C=aerodynamiccoefficientbeingstudied(CepeaTherepresentativevaluesofFVarethefollowing:forthedragcoefficient,C(seeFiguresand)fortheshapecoefficient,C,andfortheaveragevalueoftheaepressurecoefficient,caverage,onconfrontingwalls(facesparalleltothewindinTable):pesd*,FV=sd*,FV=forshapecoefficient,C,andforanaveragevalueofthepressurecoefficient,caverage,ontheroof(seeTableepe):sd*<FV=sd*>FV=Interpolatelinearlyforintermediatevaluesofsd*TheproximityeffectfactorsareconsidereduptotheheightofthetopoftheneighboringbuildingsThetrialsonwhichthepreviousrecommendationswerebasedweremadewithtwoorafewmodelswithapproximatelyequalheightsForthecaseofmanyneighboringbuildingsintheseconditions,theproximityeffectfactorsgenerallywillbesmaller,andcanbelowerthanNevertheless,therecanbeincidencesofwindthatcausevaluesofFVclosetothosepreviouslyindicated,mainlywhenthereare“emptyspaces”intheproximityofthebuildingbeingstudiedProximityeffectsonthetorsioncoefficient,C,wereconsideredtobetANNEXHDynamiceffectsinslenderandflexiblebuildingsCertainslenderandflexiblebuildingspresentintrinsicallydynamicbehavior,whenexposedtowind,andnotalwaysthemostunfavorablevelocityisthemaximumvelocityforeseenforthewindItbecomesnecessarytomathematicallyandorexperimentallystudythestability,inaveryextensiverangeofwindvelocitiesThedynamicresponseinthebuildingtotheexcitationofthewinddependsnotonlyonitsexternalshape,butalsoonthematerialsemployed,onthedampingandonthestructuralrigidityIngeneral,thevibrationsareoriginatedbyoneormoreofthefollowingcauses:HCadencedunloosingofvorticesMovementstransversaltothedirectionofwindcanbeproducedbythesevorticesifoneofthenaturalfrequenciesofthestructureorofastructuralelementisequaltotheloosingfrequencyofapairofthesevortices,withintheexpectedvelocityrangeofwindThisphenomenoncanbeparticularlyharmfulinchimneysandcylindricalmetallictowersTheenergyofthevorticesandthespatialcorrelationoftheirloosingareinfluenced,amongstotherfactors,bytheoscillationofthestructureorstructuralelementandbythecharacteristicsofthewindturbulenceTheeffectsonthestructureorstructuralelementincreasewiththereductionofthewindturbulenceandofthestructuraldampingThecriticalvelocityofthewind,V,isthevelocityforwhichtheloosingfrequencyofapairofvorticescoincidesαwithoneofthenaturalfrequenciesofthestructureorofastructuralelementThisvelocityisobtainedbytheexpression:Where:f=naturalfrequencyofthestructureL=characteristicdimensionSt=StrouhalnumberDynamiceffectsarepossibleifthecriticalvelocityisequaltoorinferiortothemaximumaveragevelocity,foreseenforthelocationofthebuildingForacircularcrosssection(Re=,d):L:diameterofthecylinderSt:<Re<St=Re>St=InterpolatelinearlyforintermediatevaluesofReForaplateperpendiculartothewind:L:widthlSt=Forarectangularcrosssectionwindperpendiculartothelargestface:L:widthlSt=Forprofileswithflatfaces:L:widthISt:to(ingeneral)Asanapproximateindication,theaveragevelocity,,canbecalculatedoveranintervaloftimeofbetweensands(toperiodsofloosingofapairofvortices,dependinguponthestructuraldamping)Asthewindvelocityisvariablewiththeheight,thefrequencyofloosingofthevorticeswillalsobevariablewiththeheight,whichgreatlyreducestheeffectsonthestructureorstructuralelement,duetothelackofsynchronismoftheexcitingforceHGusteffectsThebuildingsuffersdynamiceffectscausedbytheturbulenceexistinginthewakeofanotherbuildingTheseeffectscabbeconsiderable,inlightandslenderbuildings,aswellasinbuildingswithgreatheightandthinnessHGallopTheeffectdenominatedgallopisduetotheforcesdeterminedbythemovementofthebuildingandbyitsshapeAmongsttheshapessensitivetothisphenomenon,aretheprismaticbuildingswithrectangularandtriangularcrosssectionsGallopappearsasacertainwindvelocityisexceeded,producingoscillationsthataretransversaltothedirectionofthewindTheseoscillationsincreaseinamplitudewiththewindvelocity,andcanbemuchlargerthanthoseprovokedbycadencedvorticesThinconstructions,whicharelightandflexible,suchasthelatticedpillarsofaveryhighviaductarepronetothisphenomenonHFlutterThisisthedynamiceffectthatinvolvestwoormoredegreesoffreedomofthestructure,withvibrationcouplingItisaphenomenontypicalofslenderstructureswithproportionssimilartothewingsofanairplane,suchasaverytallandslenderbuilding,witharectangularcrosssectionthatisnotclosetosquareHEnergycontainedintheatmosphericturbulenceEventhoughthewindgustsconstituteanaleatoryphenomenon,thecharacteristicsofthemechanicaladmittanceofastructurecancausethekineticenergycontainedinthewindguststooriginateanonnegligibleoscillationinthebuildingFormoredetails,seeChapterandAnnexIANNEXIDeterminationofthedynamicresponseduetoatmosphericturbulenceSimplifiedmethodThewindloadwillbedetermined,inthedirectionoftheaveragevelocity,inabuildingwithasquaresectionof=msandtheminheightandmonaside,locatedincategoryIVterrain,wherethevelocityVoparametersS=andS=thefollowingalternativeswillbeanalyzedcasea:buildingwithaconcretestructure,inwhichthehorizontalforcesareexclusivelyresistedbyporticoscaseb:idem,witharesistantsteelstructure(weldedunions)Calculate,inthefirstplace(see):=xxx=mspThefundamentalperiods,forbothofthecases,werebasedonmeasurementsmadeinsimilarbuildingsThemodalshape(parameter,)andthecriticaldampingratiowereobtainedfromTable:casea:T=s,,=Ç=caseb:T=s,,=,Determinationofthedynamicamplificationcoefficient,:casea:fL=,x,=,pFromthegraphinFigure,weobtain,forlh==and,=:h(m):,caseb:pfL=x,=FromthegraphinFigure,weobtain,forh==e,=:h(m):Thevaluescorrespondingtoh=mcanbedeterminedbygraphicalinterpolation,asillustratedinFigure,resultingin:casea:,=(concrete)caseb:,=(steel)Calculate,asfollows(see):qb=xx=NmoThedynamicpressurevariationwiththeheightisgivenbytheexpression(qinNm,zinm):,,casea:q(z)=(z)()(z)xx,q(z)=(z)(z),caseb:q(z)=(z)()(z)xx),q(z)=(z(z)Atthetopofthebuilding(z=m),thedynamicpressureresultsareequalto,Nminthecaseofabuildingwithareinforcedconcretestructureandto,NminthecaseofabuildingwithasteelstructureThestaticmethodconductstoasinglevalueof,Nm(categoryIV,classC,lowturbulencewind):V=VSSS=xxx=mskOq=V=,NmkTheequivalentstaticforce,perunitofheight,isobtainedbytheexpression(see):q(z)lCawhereI,thewidthofthebuilding,equaltomThedragcoefficient,C,isobtainedfromthegraphofFigure,aor,fortherarecasesofhighturbulencewind,fromthegraphinFigure,whereitsvalueisconsiderednonvariablewithZDiscretemodelThewindloadwillbedetermined,inthedirectionoftheaveragevelocity,inareinforcedconcretechimneywiththecharacteristicsindicatedinTableThepropertiesofthemodeladoptedinthedynamicanalysisareindicatedin=HzTheshapeofTableThefundamentalvibrationfrequencyofthechimneywascalculated,obtainingfthefundamentalvibrationmodeisalsogiveninTable,adoptingtheratioofcriticaldamping,=ThedragcoefficientisC=,takingintoaccounttheReynoldsnumberandtheroughnessofthesurfaceofthechimneyaWhereV=ms,S=S=,thedesignvelocityresultsareequalto:TheterrainhasacategorylllroughnessFromFigureweobtain,forfL=,valuesforh=,p,andmandfortherelationshiplh=OandBygraphicalinterpolation,wearriveat,=FromTable,weobtainp=andb=Followingthis,wecalculate(see):ThegraphicalinterpolationthatpermittedthedeterminationisreproducedinFigure,whileTableshowsthecalculationschemeforthedeterminationoftheforcesinthechimney,forthefundamentalvibrationmode(j=)Formulas(see)andtheauxiliaryvalues:SteelstructureConcretestructureCategoryIVFigureGraphicaldeterminationofthedynamicamplificationcoefficientlinearinterpolationFigureGraphicaldeterminationofthedynamicamplificationcoefficientTableCharacteristicsofthechimneyHeighth=mExternalThicknessoftheMomentofZ(m)Mass(kgm)diameter(m)wall(m)Inertia(m),,,,O,TablePropertiesoftheadoptedmodelTableDeterminationoftheaveragefluctuatingandtotalforcesonthechimneyforthefundamentalmode(j=)INDEXItemsPageObjectiveLiteralconventionsUppercaseromanlettersLowercaseromanlettersGreeklettersDefinitionsWindwardReticulationOverpressureLeewardSuctionFrontalsurfaceBasicwindHighturbulencewindLowturbulencewindProcedureforthecalculationoftheforcesduetowindinbuildingsWindonpartiallyexecutedstructuresDeterminationofthestaticforcesduetowindPressurecoefficientsShapecoefficientsForcecoefficientsDeterminationofthedynamiceffectsofwindCharacteristicwindvelocityBasicwindvelocity,VTopographicFactor,SRoughnessoftheterrain,dimensionsofthebuildingandheightabovetheterrain:FactorSRoughnessoftheterrainDimensionsofthebuildingHeightabovetheterrainStatisticalFactorS,ChangeinroughnessoftheterrainTransitiontoahighercategoryofroughness(z>z)Transitiontoalowercategoryofroughness(z>z)AerodynamicCoefficientsforcurrentbuildingsExternalpressureandshapecoefficientsInternalpressurecoefficientsDragcoefficientsFrictioncoefficientsReductionsintheshapeanddragcoefficientsEccentricityinthedragforcesForcecoefficientsforprismaticandreticulatedbarsPrismaticbarsFlatfacedprismaticbarsCircularsectionprismaticbarsWiresandcablesReticulatedisolatedplanesMultipleflatreticulatedplanesReticulatedTowersForcecoefficientsforwalls,platesandisolatedroofsWallsandrectangularplatesIsolatedflatgableroofsDynamiceffectsduetoatmosphericturbulenceGeneralconsiderationsEntrydataforthedeterminationofthedynamicresponseinthedirectionofthewindDesignvelocityvDynamiccharacteristicsofthestructureSimplifiedcontinuousmodelDiscretemodelCalculationofthedynamicresponseinthedirectionofthewindSimplifiedmethodDiscretemodelDeterminationofthemodalcontributionsCombinationofthemodalcontributionsCalculationofthetransversaldynamicresponseofthewindCalculationofthemaximumaccelerationsforcomfortverificationandthetimeintervalANNEXANormalizedVelocitySAFactorSATimeIntervalANNEXB–StatisticalFactorSfortheprobabilityPandtheusefullifeofthebuildingofmyearsmANNEXCLocationandaltitudeofthemeteorologicalstationsANNEXDDeterminationoftheinternalpressurecoefficientANNEXEAerodynamiccoefficientsforcurvedroofsECylindricalarchedroofswithacircularcrosssectionECupolasECupolasovertheterrainECupolasovercylindricalwallsANNEXFAdditionalinformationANNEXG–ProximityeffectsGBytheVenturieffectGBywinddeflectionintheverticaldirectionGBythewaketurbulenceGDeterminationoftheproximityeffectsANNEXHDynamiceffectsinslenderandflexiblebuildingsHCadencedloosingofvorticesHGustEffectsHGallopHFlutterHEnergycontainedintheatmosphericturbulenceANNEXDeterminationofthedynamicresponseduetoatmosphericturbulenceSimplifiedMethodDiscreteModelFigureIsoplethsofthebasicvelocityV(ms)Figure–TopographicFactorS(z)iFigureProfileofSontheleewardsideofachangeinroughnessFigure–Dragcoefficient,C,forparalelepipedicbuildingsinlowturbulencewindaFigure–Dragcoefficient,C,forparalelepipedicbuildingsinhighturbulencewindaFigure–Dragcoefficient,C,forflatreticulatedplanesformedbyprismaticbarswithsharporaslightlyroundededgesFigure–Dragcoefficient,C,forflatreticulatedplanesformedbycircularcrosssectionbarsaFigureProtectionFactor,>,fortwoormoreequallyspacedparallelreticulatedplanesFigure–Dragcoefficient,C,forreticulatedtowerswithsquareorequilateraltriangularcrosssectionsaformedbyprismaticbarswithsharporslightlyroundededgesFigure–Dragcoefficient,C,forreticulatedsquarecrosssectiontowersformedbyacircularcrosssectionbarsWindincidentperpendicularlyontwoparallelfacesFigure–Dragcoefficient,C,forreticulatedsquarecrosssectiontowersformedbyacircularcrosssectionbarsWindincidentonadiagonalFigure–Dragcoefficient,C,forreticulatedequilateraltriangularsectiontowersformedbyacircularcrosssectionbarsWindfromanydirectionFigureSchemeforadiscretedynamicmodelFigureDynamicamplificationcoefficient,forcategoryterrainFigureDynamicamplificationcoefficient,forcategoryIIterrainFigureDynamicamplificationcoefficient,forcategoryterrainFigureDynamicamplificationcoefficient,forcategoryIVterrainFigureDynamicamplificationcoefficient,forcategoryVterrainFigureInternalpressureonatypicalfloorofthebuildingFigureInternalpressureinanindustrialpavilionFigure–Cylindricalarchedroofswithcircularcrosssection<I<IFigureCylindricalarchedroofswithcircularcrosssectionFigureCupolasoverterrain–IsobariclinesFigureCupolasoncylindricalwallsIsobariclinesFigure–GraphicaldeterminationofthecoefficientofdynamicamplificationFigureGraphicaldeterminationofthecoefficientofdynamicamplificationTableMeteorologicalparametersTableFactorSTableMinimumvaluesofthestatisticalfactorSTableExternalpressureandshapecoefficientsforwallsofbuildingswitharectangularplanviewTableExternalpressureandshapecoefficientsforroofswithtwosymmetricalgables,inbuildingswitharectangularplanviewTableExternalpressureandshapecoefficientsforroofswithonegable,inbuildingswitharectangularplanviewr,withhlb<sTableExternalpressureandshapecoefficients,formultiplesymmetricalgableroofswithequalsections,withh<a'TableExternalpressureandshapecoefficients,formultipleasymmetricalgableroofs,withequalsections,Withthesmallestgableinclinedatandwithh<a'TableDistributionoftheexternalpressuresincircularcrosssectioncylindricalbuildingsTableDragcoefficient,C,forconstantsectionbodiesaTableValuesofthereductionfactorKforfinitelengthbarsTableForcecoefficients,CandC,forflatfacedinfinitelengthprismaticbarsxyTable–Dragcoefficient,C,forcircularsectioninfinitelengthprismaticbarsaTableDragcoefficient,C,forwiresandcableswithId>aTableDragforcecomponentsonthefacesofreticulatedtowerswithsquareorequilateraltriangularcrosssectionTableForcecoefficients,C,forwallsandrectangularplatesfTablePressurecoefficientsonisolatedoneflatgableroofsTablePressurecoefficientsonisolatedtwosymmetricalflatgableroofsTableParametersforthedeterminationofthedynamiceffectsTableExponentpandparameterbTableParametersb,p,F,,TableNormalizedVelocitySTableStatisticalFactorSTableExternalpressurecoefficients,C,forwindblowingperpendicularlytothegeneratrixoftheperoofTableExternalpressurecoefficients,C,forwindblowingparalleltothegeneratrixoftheperoofTableExternalpressurecoefficients,c,forwindblowingobliquelytothegeneratrixoftheperoofTableExternalpressurecoefficient,C,forwindblowingperpendicularlytothegeneratrixoftheperoofTableExternalpressurecoefficient,c,forwindblowingparalleltothegeneratrixoftheperoofTableExternalpressurecoefficient,C,forwindblowingobliquelytothegeneratrixoftheperoofTableLimitvaluesoftheexternalpressurecoefficients,c,andofthesustainingcoefficients,CpesCupolasovertheterrainTableLimitvaluesoftheexternalpressurecoefficients,cCupolasovercylindricalwallspeTableExternalpressureandshapecoefficientsforroofswithtwosymmetricalgableswithacentralgutter,inbuildingswitharectangularplanview(useScorrespondingtoheighth)TableExternalpressureandshapecoefficientsformultiplegableequalsectionroofswithaverticalgable,TableCharacteristicsofthechimneyTablePropertiesoftheadoptedmodelTableDeterminationoftheaverageandtotalfluctuatingforcesinthechimneyforthefundamentalmode(j=
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