ACI 435.8R-85 Observed Deflections of Reinforced Concrete Slab Systems

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1、SP-86-2ACI435.8R-85(Reapproved1991)(Reapproved1997)ObservedDeflectionsofReinforcedConcreteSlabSystems,andCausesofLargeDeflectionsByACICommittee435D.R.Buettner*S.K.Ghosh*ChairmanChairman,SubcommitteeonFieldMeasurementsD.E.BransonS.V.KulkarniA.Scanlon*R.G.Drysdale*M.S.Mirza*J.

2、M.SpangA.FarahE.G.Nawy*M.K.TadrosA.B.GogateM.V.PregnoffA.F.ShaikhJ.GrossmanG.M.Sabnis*S.ZundelevichC-T.T.HsuC.G.Salmon*MembersoftheSubcommitteeonFieldMeasurementswhichpreparedthisreport.**PleaseseePrefacefortheentire435membership.Synopsis:Thisreportisintwodistinctparts.PartI

3、isasummaryofpublishedstudiesonslabdeflections(3fromAustralia,1fromScotland,1fromSweden,2fromU.S.).Thesummaryfocusesonconstructionpracticesandmaterialsquality.Comparisonofdeflectionscalculatedbyvariousmethodswithactuallong-termdeflectionsismadeinsomecases.PartIIsummarizesseve

4、ralconstructionproblemsandmate-rialdeficiencieswhichcancontributetolargelong-termdeflec-tions.Focusingonlargeconstructionloads,theauthorsshowCopyright©1985,AmericanConcreteInstitute.12ACICommittee435thatconstructionloadsmaybeconsiderablyhigherthandesignloadsandthathighconstr

5、uctionloadscausehighinitialdeflec-tionsbecauseconcretehasalowermodulusofelasticitywhenloadedatanearlyage.Furthermore,concretecreepsmorewhenitisloadedatanearlyage,therebycausingadditionalhighlong-termdeflections,evenwhenconstructionloadsaresus-tainedonlyforafewdays.Theauthors

6、thensuggestamethodofformremovalandreshoringthathasprovedsuccessfulintheNewYorkCityareainpreventinglargeslabdeflections.Essentially,nomorethanan8-footslabspanisleftunsupporteduntilaslabismature.AreaderinterestedonlyintheCommittee'sfindingsandrecommendationsmayproceedstraightt

7、oPartIIofthereport.;concreteslabs;creepproperties;deflection;flatconcreteplates;formremoval;loads(forces);modulusofelasticity;reinforcedconcrete;shorinq;shrinkage;two-wayslabs.Contents:PartIFIELDDEFLECTIONMEASUREMENTSOFREINFORCEDCONCRETEFLATPLATES,FLATSLABSANDBEAMS:AREVIEWOF

8、LITERATUREInvestigationA(CommonwealthScientificandIndustrialResearchOrganiz