土木工程专业英语 教学课件 作者 陈瑛 4.6.Slab.ppt

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1、4.6Slab单向板(a)两对边简支矩形板(b)两对边简支矩形板的弯曲形状One-wayslabIftheratiooflengthtowidthoftheslabpanelisgreaterthan2,mostoftheloadiscarriedintheshortdirectiontothesupportingbeamsandonewayactionisobtainedineffect,eventhoughsupportsareprovidedonallsides.双向板two-wayslabWhenarectangularsl

2、abissupportedonallthesidesandthelength-to-widthratio(L/B)islessthantwo,itisconsideredasatwo-wayslab.DesignofOne-WaySlabDesignofOne-WaySlabIftheratiooflengthtowidthoftheslabpanelisgreaterthan2,mostoftheloadiscarriedintheshortdirectiontothesupportingbeamsandonewayactioni

3、sobtainedOne-WaySlabReinforcementMainreinforcementUsedtoresistmomentShrinkageandtemperaturereinforcementUsedtopreventcrackingduetocontractionoftheconcreteresultingfromshrinkageandtemperaturechangesTemperatureandShrinkageReinforcementSlabsandothermembersarejointedrigidl

4、ytootherpartsofthestructureandcannotcontractfreely.Thisresultsintensionstressesknownasshrinkagestresses.Sinceconcreteisweakintension,thesetemperatureandshrinkagestressesarelikelytoresultincracking.TemperatureandShrinkageReinforcementOne-WaySlabDesignReinforcementTypica

5、lReinforcementinaone-wayslab:Two-WaySlabTwo-wayslabsbendintoadishedsurfaceratherthanacylindricalonewhenloaded.Thismeansthatatanypointtheslabiscurvedinbothprincipledirections,andsincebendingmomentsareproportionaltocurvatures,momentsalsoexistinbothdirections.Toresistbend

6、ingmoments,theslabmustbereinforcedinbothdirections,byatleasttwolayersofbarsperpendicular,respectively,totwopairsofedges.Two-WaySlabTheslabmustbedesignedtotakeaproportionateshareoftheloadineachdirection.thelargershareoftheloadiscarriedintheshortdirection,theratioofthetw

7、oportionsofthetotalloadbeinginverselyproportionaltothefourthpoweroftheratioofthespans.Becausethemomentsinthelongdirectionarethesmallerones,itiseconomicaltoplacethesteelinthatdirectionontopofthebarsintheshortdirection.Thestackingproblemdosesnotexistfornegativereinforcem

8、entperpendiculartothesupportingedgeexceptatthecorners,wheremomentsaresmall.