土木工程專業(yè)英語 課件 4.4. Reinforced Concrete Column

4.4ReinforcedConcreteColumn4.4.1TypesofColumnColumnsaredefinedasmembersthatcarryloadschieflyincompression.Columnscarryaxialcompressiveloadsbendingmomentcompressionforcesdominate.4.4.1TypesofColumnUsuallycolumnscarrybendingmomentaswell,aboutoneorbothaxesofthecross-section.bendingmomentaboutyaxisBendingactionmayproducetensileforceoverapartofthecross-section.ClassificationofColumnsBasedonloadingAxiallyloadedcolumnEccentricallyloadedcolumnBiaxiallyloadedcolumnseccentrically[ik5sentrikEli].偏軸地BiaxiallyloadedcolumnsAxiallyloadedcolumnClassificationofColumnsAxiallyloadedcolumnloadsareassumedactingatthecentroid

ofcolumnsection.centroid

[5sentrCid]質(zhì)心偏心受力MNcNte0=M/NcNce0=M/NtNt轉(zhuǎn)化為Nce0loadactsatadistanceefromthecentroidofcolumnsection.EccentricallyloadedcolumnClassificationofColumnsThedistanceecouldbealongthexoryaxis,causingmomentseither

aboutthexaxisor

yaxis.momentsabouttheyaxismomentsaboutthexaxisEccentricallyloadedcolumnClassificationofColumnsBiaxiallyloadedcolumnsloadisappliedatanypointonthecolumnsection,causingmomentsabout

boththexaxisand

yaxissimultaneously.Biaxially

loadedcolumnsClassificationofColumnsBasedonlengthShortcolumnsLongcolumnsShortcolumnscolumn’sfailureisduetocrushingofconcreteyieldingofsteelbarsReachfullloadcapacityuponfailure

Longcolumns(slendercolumns)長柱bucklingeffect

屈曲andslendernessratio長細比mustbetakenintoconsiderationreducingtheloadcapacityofthecolumnrelativetothatofashortcolumn.在同等條件下，即截面相同，配筋相同，材料相同的條件下，長柱承載力低于短柱承載力ClassificationofColumnsBasedonlateralreinforcementColumnsreinforcedwithlongitudinalbarsandlateralties.普通箍筋柱縱筋箍筋：側(cè)向約束縱筋、抗剪bhClassificationofColumnsBasedonlateralreinforcementColumnsreinforcedwithlongitudinalbarsandcontinuousspirals.螺旋箍筋柱ClassificationofColumnsBasedonlateralreinforcementCompositecompressionmembers組合柱

reinforcedlongitudinallywith

structuralsteelshapes型鋼structuralsteelpipe鋼管structuralsteeltubing[5tju:biN]管形材料withorwithoutadditionallongitudinalbarswithvarioustypesoflateralreinforcementReinforcementincolumns配筋形式Themainreinforcementincolumnsislongitudinal,paralleltothedirectionoftheloadLateralreinforcement

：arrangedinasquare,rectangular,orcircularpattern.縱筋箍筋：側(cè)向約束縱筋、抗剪內(nèi)折角處！??！bhReinforcementincolumns配筋形式LateralreinforcementTiesindividualrelativelywidelyspacedSpiralscontinuouscloselyspacedFunctionsoflateralreinforcementholdthelongitudinalbarsinpositionspreventlongitudinalbarsfrombucklingLateralreinforcement,intheformofindividualrelativelywidelyspacedtiesoracontinuouscloselyspacedspirals,servesseveralfunctions.max.80mmMin.80mmtiesspiralForone,suchreinforcementisneededtoholdthelongitudinalbarsinpositionsinthe

formswhiletheconcreteisbeingplaced.Forthispurpose,longitudinalandtransversesteelarewiredtogethertoformcages,whicharethenmovedintotheformsandproperlypositionedbeforeplacingtheconcrete.鋼筋骨架Foranother,transversereinforcementisneededtopreventthehighlystressed,slenderlongitudinalbarsfrombucklingoutwardbyburstingthethinconcretecover.4.2.2ShortColumnsBehaviorofAxiallyLoadedShortColumn

Whenanaxialloadisappliedtoareinforcedconcreteshortcolumn,theconcretecanbeconsideredtobehaveelasticallyuptoalowstressofabout1/3fc

當軸向應力小于1/3fc時，短柱的壓縮變形主要為彈性變形。Twodifferenttypesoffailureoccurincolumns,dependingonwhethertiesorspiralsareused.tiedcolumnfailssuddenlyattheloadNaspirallyreinforcedcolumncontinuestodeflectAtiedcolumnfailsattheloadNa

concretefailsbycrushingorshearingoutwardalonginclinedplanes混凝土被壓碎崩裂

longitudinalsteelbarsfailbybucklingoutwardbetweenties箍筋之間的縱向鋼筋壓屈而向外凸出shearingoutwardalonginclinedplanesspirallyreinforcedcolumnwhenthesameloadNaisreached,longitudinalsteelandtheconcretewithinthecorearepreventedfrommovingoutwardbythespiral.Theconcreteintheoutershellspallsoff

confiningactionofthespiralstartstotakeeffectifsizablespiralsteelisprovided,theloadwillultimatelyfailthecolumnbycausingthespiralsteeltoyield.SpirallyreinforcedcolumnTheaxialstrainwhenthecolumnfailscanbemuchlargerthanthatatwhichtheshellspallsoff.TheultimatebearingcapacityofashortcolumnreinforcedwithlongitudinalbarsandlateraltiesIftheloadonthecolumnisincreasedtoreachitsultimatestrength,concretewillreachthemaximumstrengthsteelwillreachitsyieldstrengthDetailingRequirementsforReinforcementMaterialStrength：Concretestrengthhasapronouncedeffectonthestrengthcapacityofacolumn.ThehighstrengthconcreteC30-C40orhighergradearegenerallyused.受壓構(gòu)件的承載力主要取決于混凝土強度，一般應采用強度等級較高的混凝土。目前我國一般結(jié)構(gòu)中柱的混凝土強度等級常用C30~C40。ReinforcementsofgradeHRB335orHRB400areused,andthehighstrengthbarsarenotrecommended.鋼筋：通常采用Ⅱ級和Ⅲ級鋼筋，不宜過高。DetailingofColumnLongitudinalReinforcementTheratiooflongitudinalsteelareatogrossconcretecross-sectionareaisintherangefrom0.6percentto5percent.Thelowerratiolimitisnecessarytoensureresistancetobendingmomentnotaccountedintheanalysisandtoreducetheeffectsofcreepandshrinkageoftheconcreteundersustainedcompression.

考慮到實際結(jié)構(gòu)中存在偶然附加彎矩的作用（垂直于彎矩作用平面），以及收縮和溫度變化產(chǎn)生的拉應力，規(guī)定了受壓鋼筋的最小配筋率DetailingofColumnLongitudinalReinforcementRatioshigherthan5percentnotonlyareuneconomical,butalsowouldcausedifficultyowingtocongestionofthereinforcement,particularlywherethesteelmustbespliced.考慮到施工布筋不致過多影響混凝土的澆筑質(zhì)量，全部縱筋配筋率不宜超過5%。Mostcolumnsaredesignedwithratiosbelow2percent.

DetailingofColumnLongitudinalReinforcementLargerdiameterbarsareusedtoreduceplacementcostsandtoavoidunnecessarycongestion.一般宜采用根數(shù)較少，直徑較粗的鋼筋，以保證骨架的剛度。

Thediameterofthelongitudinalreinforcementshouldnotbelessthan12mm.縱向受力鋼筋的直徑不宜小于12mmAminimumoffourlongitudinalbarsisrequiredwhenthebarsareenclosedbyspacedrectangularorcircularties.柱中縱向受力鋼筋不少于４根DetailingofColumnLongitudinalReinforcementSpacingbetweenlongitudinalbarsmeasuredalongtheperiphery[pE5rifEri]shouldnotexceed300mm.側(cè)面上的縱向受力鋼筋中距不宜大于300mmWhenthedepthoftheeccentricallyloadedcolumnisgreaterthan600mm,additionallongitudinalbarswithadiameterof10-16mmshouldbeplacedonthelateralsides.當偏心受壓柱的截面高度h≥600mm時，在柱的側(cè)面上應設(shè)置直徑為10-16mm的縱向構(gòu)造鋼筋DetailingofColumnLongitudinalReinforcementLongitudinalbarsinacolumnaregenerallysplicedatmid-storeyheight,awayfromthesectionofmaximumstress.Wherethecolumncross-sectiondimensionschange,longitudinalbarsneedtobeoffset.Theslopeoftheoffsetbarshouldnotexceed1in6.Horizontaltiesareneededwithintheoffsetwithaspacingnottoexceed10timestheminimumdiameteroflongitudinalbarsor200mm,whicheverisless.

DetailingofColumnTiesorHoopsTopreventbucklingoflongitudinalbars,allbarsoftiedcolumnsshallbeenclosedbylateralties.受壓構(gòu)件中的周邊箍筋應做成封閉式。Thetiesmustbeatleast1/4ofthemaximumlongitudinalbardiameterandatleast6mm.箍筋直徑不應小于d/4（d為縱向鋼筋的最大直徑），且不應小于6mm。

DetailingofColumnTiesorHoopsTheverticalspacingoftiesincolumnsshouldnotexceed15timestheminimumdiameteroflongitudinalbars,400mm,orthesmallestdimensionofthecolumnsize,whicheveristheleast.箍筋間距不應大于400mm及構(gòu)件截面的短邊尺寸，且不應大于15d（d為縱向受力鋼筋的最小直徑）。

DetailingofColumnTiesorHoopsWhentheoverallreinforcementratioisgreaterthan0.03,hoopsshouldbeusedwithaspacingnottoexceed10timestheminimumdiameteroflongitudinalbars,butnotlargerthan200mm.Theminimumhoopdiameterisspecifiedtobe8mm.當柱中全部縱向受力鋼筋的配筋率大于3%時，箍筋直徑不應小于8mm，間距不應大于縱向受力鋼筋最小直徑的10倍，且不應大于200mm；

DetailingofColumnTiesorHoopsThetiesshallbesoarrangedthateverycornerandalternatelongitudinalbarshallhavelateralsupportprovidedbythecornerofatiehavinganincludedangleofnotmorethan135degree,andnolongitudinalbarshallbefartherthan300mmoneithersidefromsuchalaterallysupportedbar.DetailingofColumnTiesorHoopsInmemberswithlargeaxialforcesandsmallmoment,longitudinalbarsarespacedmoreorlessuniformlyaroundtheperimeter.Whenbendingmomentsarelarger,muchofthelongitudinalsteelisconcentratedatthefacesofhighestcompressionortension,i.e.,atmaximumdistancefromtheaxisofbending.highestcompressionortensionDetailingofColumnSpiralsSpiralcolumnsrequireaminimumofsixlongitudinalbar