[精品]结构分析

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1、ANALYSISOFCRACKINGEFFECTSONTALLREINFORCEDCONCRETEBUILDINGSINTRODUCTIONTheresponseofreinforcedconcretemembersandstructuralsystemstoloadshasbeenthesubjectofmuchinvestigationsincethetimereinforcedconcretewasfirstusedasadominantstructuralmaterialinengineeringconstruction.Inthedesignproce

2、ssofallreinforcedconcretebuildings,controloflateraldriftisoneofthemostimportantserviceabilitycriteria,notonlytopreventlargesecond-orderP-deltaeffects,butalsotoavoidthemalfunctioningofnonstructuralcomponentssuchaselevatorsanddoors.Cracking,whichisprimarilyloaddependent,reducesthelater

3、alstiffnessandsubstantiallyincreasesthelateraldeflectionofabuilding.Toaccuratelyassessthelateraldeflection,crackedmembersinthesetallbuildingsneedtobeidentifiedandtheireffectivememberstiffnessdetermined.Indesign,theeffectsofconcretecrackingonthestiffnessofthestructuralframearegenerall

4、yaccountedforbyassigningreducedmomentsofinertiatothemembers・Thegrossmomentofinertiaofbeamsisusuallyreducedto50%oftheiruncrackedvalues,whereasthegrossmomentofinertiaofcolumnsisreducedto80%(StaffordSmithandCoull1991).Thereductionsaregenerallyconsideredconstantoverthetotalheightofthestr

5、uctures,independentofthehistory,type,andmagnitudeofloading,andindependentofthereinforcementratiosinthemembers・Noconsensuscanbedrawnastowhetherthistypeofdesignisconservativeornot,becausenoreliableanalysishasbeendevelopedtoestimatesatisfactorilytheeffectofcracking.Whenthedeflectionofbe

6、amsoronewayslabsisrequiredincalculations,anempiricalexpressionforeffectivemomentofinertiadevelopedbyBranson(1963)isperhapsthemostwidelyused・VariousformsoftheBransonformulacanbefoundintheAmericanConcreteInstitute(ACI)BuildingCodesince1971(ACI1995),CAN3-A23.3-M95[CanadianStandardsAssoc

7、iation(CSA)1994]andAS3600-1994[StandardsAssociationofAustralia(SAA)1994].BasedonBranson'seffectivestiffnessmodel,Polak(1996)andScanlonandMurray(1982)developedcomputationaltechniquesfortheanalysisofreinforcedconcreteslabs・Thesetechniquesaresimpleandaccurate,andprovideveryreasonableest

8、imatesofslab