臨時(shí)支撐風(fēng)荷載計(jì)算 standard method

臨時(shí)支撐風(fēng)荷載計(jì)算(BS6399-2:1995StandardMethod)1BasicwindspeedDefinition:thehourlywindspeedwithanannualriskQofbeingexceededof0.02,irrespectiveofwinddirection,ataheightof10movercompletelyflatterrainatsealevelthatwouldoccuriftheroughnessoftheterrainwasuniformeverywhere(includingurbanareas,inlandlakesandthesea)andequivalenttotypicalopencountryintheUnitedKingdom.ThebasicwindspeedVbshouldbetakenfromFigure6(limitedinUKregion).InthecaseofNTStender,only3secondgustspeedisprovidedinthewindreport,thus3secondgustspeedneedtobeconvertedtohourlywindspeedinaccordancewithBS6399-2:1995.Therelationshipisshownasfollows:☆3secondgustspeeda1.6xhourlywindspeedReferredtoGustAndMeanWind.pdfconfirmed!!NotethatQ=0.02equivalenttoonce-in-50-yearrisk,refertoannexD.2.SitewindspeedThesitewindspeed,Vs,shouldbecalculatedfrom:Altitudefactor,SaThealtitudefactordependson:ThealtitudeabovesealevelAnysignificanttopography.Iftopographyisnotconsideredtobesignificant,Sa=1+(altitude/1000).Altitudeismeasuredinmeters.Directionalfactor,SdValuesofthedirectionalfactorarefoundinTable3.Seasonalfactor,SsInmostcircumstances,theseasonalfactorhasavalueof1.00.Ifthestructurewillbeexposedtothewindforlessthanoneyear(i.e.atemporarystructure),aseasonalfactoroflessthan1.00maybeused.Probabilityfactor,SpTheprobabilityfactorhasavalueof1.00orless.Usingaprobabilityfactorof1.0representsaonce-in-50-yearrisk,equivalenttoanannualriskof0.02.Asthetemporarysupportisatemporarystructure,theannualmodecorrespondingtomostlikelyannualmaximumvalueisconsidered,refertoannexD.Sp=0.749forQ=0.632whenannualmodeisadopted.3.EffectivewindspeedTheeffectivewindspeedisderivedfromthesitewindspeed,dependingontheterrainandthebuildingheight.K=%x覓TerraincategoryInordertodeterminetheterrainandbuildingfactor,theterraincategory,theeffectiveheightandthedistancefromtheseamustallbecalculated.ThreecategoriesofterrainaredefinedintheStandard:Sea(whichineludeslargestretchesofinlandwater)TownCountryEffectiveheightandreferenceheightinlatticesForhorizontalsections,thereferenceheightHrshouldbetakenastheheightabovegroundoftheaxisofthesection.Verticalorinclinedsectionsmaybetakenasbeingdividedintopartsoflengthatleasttwicethecrosswindbreadth,L>2B,andtherefereneeheightHrshouldbetakenastheheightabovegroundofthetopofeachpart.Forconservative,thebeneficialfactorisignored.EffectiveheightHeistakenasthereferenceheightofbuildingHr.Distancefromthesea

Inordertodeterminetheterrainandbuildingfactor,thedistancefromtheseamustbecalculated.Theeffectivewindspeedreducesasdistancefromthecoastincreases.Table4.2R^comn^endedaccuracyformeasL/ringdistancefromtheseaDistancefromtheseaRecommendedaccuracyBetween100and3DOmNearest100mBetween300mand'IkmNearest200mBetween1kmand3kmNearest600mBetween3kmand10knnNearestkmBetween10kmcind30kmNearest2kmBetween30kmand100kinNearest10kmFactorSbUblc4hFactoriSfeforstEmdardmethodSlt?Inc&oiitTyShiteinUjwHmextending蘭2kmupwindfromthEsiteEtTectiveheifChtCloflesEdintancrtoaraEfTectili^hrfiKtitClos?tdisUnCr3艙削塊kmkmHl0210工100m210M100s21-48L.401.351.26占2IL】冉i,inl.ff?&1.651621.571.45&1-501.451.36101.781冷1.73182101"31.60].&e151^51S31.8Z1.71151,S5L821,7130L901-90L89L77SO1.90l.sel.?730L開1.96L961.85303.舗Lfi61.8&502.042-042.041.S5丸2.042j041.951002.!22.522322.07IIX)￡422,122-07NOTEkInEerpclaticnmaybftusedwithineacrhtable.NOTE2-Thefiguresmthistab膽havebesnrLmrived!fromreference番]NOTE3-購Iln^sajinumeadiagonaldhriEvtskma?5m.NOTE4,If珥>IQOmussthediirectioinaJmethodofswtion3kAstemporarysupportisdesignedasalatticescolumn,thewindloadontheopenlatticescolumnisdeterminedbysummingtheloadsonindividualelement,referto.Therefore,thevalueofSbwillbevariousastheeffectiveheightofelementschange.4CalculationofloadsDynamicpressureThedynamicpressureisgivenby:幺=0,613xK-

PressurecoefficientsforelementsCpNetpressurecoefficientsforcircularandshape-edgedsectionsuchasrolledsteelsection,plategirder,boxsection,beamandcirculartubewiththelongaxisnormaltowindaregivenintable20IIhble20.NetpressurecoefficientsCpforlongelementsElementtypeqCircularsectionsL2Sharp-edgedsections2,0ThelengthofelementThelengthLbetweenfreeendsshouldbetakenasthelengthofeachelement,i.e.thelengthbetweennodesofthelattice.NetsurfacepressureP=qCesp5.ExampleBasicwindspeedReferredto4640CPPFinalReport-SSH-StructuralWindLoads.pdf,recommend3secondgustspeed:32m/s.3secondgustspeeda1.6xhourlywindspeedTherefore,hourlywindspeed:20m/s.SitewindspeedThesitewindspeed,Vs,shouldbecalculatedfrom:K=KxxSdx3；x￡Altitudefactor,SaInthiscase,topographyisnotsignificantandaltitudeis104.5m.Sa=1+104.5/1000=1.1.Directionalfactor,SdOnlyonewinddirectionisconsideredinthiscase,therefore,Sd=1.0.45°需考慮Seasonalfactor,SsHowever,inthisproject,thetemporarysupportisexpectedtoexposetothewindmorethanoneyear.Thus,Ss=1.0.Probabilityfactor,SpAsthetemporarysupportisatemporarystructure,theannualmodecorrespondingtomostlikelyannualmaximumvalueisconsidered.Sp=0.749forQ=0.632whenannualmodeisadopted.Basedonaboveparameters,Vs=16.48m/s.EffectivewindspeedTheeffectivewindspeedisderivedfromthesitewindspeed,dependingontheterrainandthebuildingheight.ve=TerraincategoryIntown.IncountryDistaneefromtheseaD=2kmEffectiveheightTakethefirstintervalasanexample.Theeffectiveheightofhorizontal,vertical,diagonalelementsH=4.5m(asshownin①，②,③)