Axialtensionmembers轴拉构件

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1、Tensionmembersoccurintrusses,andinsomespecialstructuresLoadisusuallyself-aligningEfficientuseofmaterialStress=Force/AreaTheconnectionsarethehardestpartEurekaMuseum,BallaratAxialTensionMembersForshortpiers,Stress=Force/AreaForlongcolumns,bucklingbecomesa

2、problemLoadisseldomexactlyaxialSlendercolumns,UniswimmingpoolSquatbrickpiersAxiallyLoadedPiersMemberwillonlyfailintruecompression(bysquashing)-iffairlyshortshortcolumnOtherwisewillbucklebeforefullcompressivestrengthreachedlongcolumnAxiallyLoadedPiers(co

3、nt.)HorizontalloadxheightLoadxeccentricityyHWPeR=WR=W+PMMOTM=HyOTM=PeWTheOverturningMoment(OTM)Theaveragecompressivestress=Force/AreaButitisn’tuniformacrossthesectionStressescanbesuperimposedElevationPPlanStressdiagramsPebd=compressivestress=tensilestre

4、ssMPonlyMonlyPandMaddedEccentricallyLoadedPiersStressduetoverticalloadisP/A,allcompressionStressduetoOTMisM/Z,tensiononesideandcompressionontheotherIsthetensionpartbigenoughtoovercomethecompression?Whathappensifitis?DoesTensionDevelop?Ifeccentricityissm

5、all,P/AisbiggerthanPe/ZIfeccentricityislarger,Pe/ZincreasesConcretedoesn’tsticktodirt—tensioncan’tdevelop!PonlyLargerMonlyPandMaddedPonlySmallerMonlyPandMaddedTensionDoesTensionDevelop?(cont.)Forarectangularpier—Reactionwithinmiddlethird,notensionReacti

6、onoutsidemiddlethird,tensiontriestodevelopWithinmiddlethirdLimitOutsidemiddlethirdMiddle-ThirdRulethelimitingcaseTheoverturningeffectissimilartoeccentricloadingWetreatthemsimilarlyThereisonlytheweightofthepieritselftoprovidecompressionyHWR=WMOTM=HyHoriz

7、ontalLoadsonPiersExtraloadhelpstoincreasethecompressioneffect,andcounteracttension2PElevationPPlanHHy=compression=tensionStressdiagramsSometensionoccursExtraloadavoidstensionPinnaclesaddloadExtraWeightHelpsWillitsink?(Canthematerialstandthemaximumcompre

8、ssivestress?)Willitoverturn?Reactionwithinthemiddlethird—factorofsafetyagainstoverturningusuallybetween2and3Reactionoutsidemiddlethird—factorofsafetyinadequateReactionoutsidebase—nofactorofsafetyHowSafeismyPier?Aslendercolumnbuck