施工期现浇钢筋混凝土结构的受力特性

212Vol.21No.220044ENGINEERINGMECHANICSApril20042002-10-092002-11-27(50378051)(2003)(1963);(E-mail:[e-mail])(1963)(1963)(1932)1000-4750(2004)02-0062-071122(1.1000842.200092)()TU318APERFORMANCEOFCASTINGIN-SITECONCRETEBUILDINGSDURINGCONSTRUCTIONZHAOTing-sheng1,FANGDong-ping1,GUXiang-lin2,ZHANGYu2(1.TsinghuaUniversity,Beijing100084,China;2.TongjiUniversity,Shanghai200092,China)Abstract:Castingin-siteconcretebuildingsduringconstructionistime-dependentandofimportanceforcontrollingthesafetyandrecognizingthepropertiesofitsbearingloads.Anelasticcharacteristicvaluewhichisdefinedastheratioofstiffnessofslabtotheshoreisintroducedforthetime-dependentstructures.Amodelofcontinuousbeamwithspringsupportsisputforwardtoanalysetime-dependentstructuralsystems.Comparingtheresultsofthemodelwiththatofothermethodsandtheresultsmeasuredfromconcretebuildingduringconstruction,goodagreementisreached.Principlesofbearingloadsoftime-dependentstructuralsystemaregiven.Positionofthemaximumbearingconstructionloadoffloorcanbemovedup,whentheelasticcharacteristicvalueoftime-dependentstructuresweresmaller,andthetimeofshoreremovalcanalsochangethepositionofthefloormaximumbearingconstructionloads.Theelasticcharacteristicvalueoftime-dependentstructuresandthetimeofshoreremoval,bothhaveeffectsontheratiosofmaximumconstructionloadsbornebyfloors.Maximumconstructionloadsbornebyfloorsareofwaveformwiththepositionoffloor.Thelowerthepositionoffloor,thelargerthewaveofconstructionload,diminishingintheend.Keywords:reinforcedconcretestructures;constructionprocesses;time-dependentstructuralsystem;performance631[1,2]—(1)[3]1Fig.1Lawofsystemfailureandtheconcretestructuralresistanceagainsttime2050Neilsen[4]1963GrundyKabaila[5](ACI347-88)1983W.F.Chen[6,7]()[8][9][10][11][12]()CBSS(ContinuousBeamwithSpringSupports),2CBSS2.1(1)(2)(3)(4)2.2(2)2Fig.2ThemodelofContinuousBeamwithSpringSupports(CBSS)frt()6433CBSSFig.3CBSSmodelfortime-dependentstructuresofconcretebuildingduringconstruction2.30kEI284[5])(xq)()(d)(044xwkxqxxwdEI-=(1)0)(=xq0)(d)(044=+xwkxxwdEI(2)404kEIs=S(4):HAEkSS/0=(3)SEN/mm2SAmm2Hmm4[5]Fig.4Early-ageconcreteelasticmodulusdevelopingwithtime[5](2)0)(4d)(444=+xwSxxwd(2a)0w0j0M0QMQx∑∑-++=PmPDskMCkSBsAww0020044)(xxjx(4)xxjxjDwsPCkSMBkSAPm002030444)(--+=∑∑(5)xxjxDkSCwkSPBsMAMPm003002)(---=∑∑(6)xxjxCkSBwskMDsPAQmP002004)(---=∑∑(7)sx=x(8)sxsxAcoscosh=x(9))cossinhsin(cosh21sxsxsxsxB+=x(10)sxsxCsinsinh21=x(11))cossinhsin(cosh41sxsxsxsxD+=x(12)ABCDpmPMii-1ii-165i-1iiw0iiiKRw⋅=(13)iwimm0iKiN/mmR,Ni-1iiw′1-+=⋅=′iiiiiwwKRw(14)iKi-1i1-iwi-1(13)(14)i-1i01011ikiiiiKwwKKg=+⋅=-(15)iikww111-+=g(16)kgi1,0==kiwgN-mm33.1[5](5)500500mm180mm()1500900mm50100mm728Ec=3.5104MPa41MPaEw=7.75103MPa5.6MPa900mm(s=257)1(s=257)DTable1Comparisonofinternalforcesoftime-dependentstructures(example1)unite:DTDSA1234567qqqq1/42/43/411$0.000.000.2270.00-10.000.430.2300.510.000.840.45122$0.000.000.2270.00-10.000.670.2980.820.000.820.36320.000.480.3540.510.000.940.69433$0.000.000.2270.00-1*1.001.701.0811.240.811.370.87221.001.011.1461.140.880.881.005431.000.340.7730.821.220.410.94311.331.911.3231.370.971.390.96621.331.341.4011.400.950.961.0031.340.821.4091.331.010.621.05954$0.000.000.2270.00-11.001.001.001.001.001.001.002*1.441.801.521.550.931.160.98131.451.091.171.530.950.710.765640.110.160.310.120.921.332.5821.782.021.7621.691.051.201.04331.781.421.4251.781.000.800.80140.450.640.5860.630.711.020.93075$0.000.000.2270.00-21.001.001.001.001.001.001.003*2.031.931.7071.991.020.970.85840.710.940.8710.940.761.000.927850.260.180.4230.270.960.671.56632.362.151.94522..113311..11111.010.91341.041.271.1261.180.881.080.95450.600.660.6990.890.670.740.78596$0.000.000.2270.00-31.001.001.001.001.001.001.004*1.491.881.4751.461.021.291.01051.051.041.0521.200.880.870.8761060.460.230.470.540.480.430.870$*D1CBSS66[12]TDSA1CBSS2.13D()[12]TDSA5[5]Fig.52-DStructuralModel[5]3.2(21)67C30E=3.0104Mpa4mΦ483.5mm[13]22(D)Table2Compareoftheresultsofcalculationwithfieldmeasurementofexample2uniteD11.2951.8791.42121.2952.3251.90431.2951.4940.891141.241.861.67251.241.451.414/160.9570.991.1755/170.9570.7720.9921226Fig.6Parametersofexample44.17714824525755085507Fig.7Themaximumconstructionloadsbornebyfloors78S=148S=245S=257S=55067s8Fig.8Effectsofelasticvalueoftime-dependentstructuresonthemaximumconstructionloadsbornebyconcretefloor4.2S=1487135910(s=148)9Fig.9Themaximumconstructionloadsbeardbyfloors910135(s=148)10Fig.10Effectsofremovingtimeofshoresonthemaximumconstructionloadsbornebyconcretefloor5CBSS(1)CBSS(2)s250s250(3)(4)68[1].[M].,1997.LiuXila.Thestate-of-the-artandperspectiveofstructuralengineering[M].Beijing:People’sCommunicationsPublishingHouse,1997.(inChinese)[2]PCStivaros,GTHalvorsen.Equivalentframeanalysisofconcretebuildingsduringconstruction[J].ConcreteInternationalACI,August,1991,13(8):57-62.[3].[J].,2000,33(6):105-108.Wangguangyuan,Time-dependentstructuralmechanics[J].ChineseJ.ofcivilengineering,2000,33(6):105-108.[4]KNeilsen.Loadonreinforcedconcretefloorslabsandtheirdeformationduringconstruction[R].BulletinNo.1