1Example36Title3-DsinglestoryframestructureDescriptionComputethenaturalfrequenciesofa3-Dsinglestoryframestructure.StructuralgeometryandanalysismodelVerificationExample2ModelAnalysisType3-DeigenvalueanalysisUnitSystemin,lbfDimensionLength27.25inWidth17.25inHeight18.625inMassM5~M8,M13~M18=8.94223×10-3lbf∙sec2/inM9~M12=0.0253816lbf∙sec2/inElementBeamelementMaterialModulusofelasticityE=27.9×106psiPoisson’sratioν=0.3SectionPropertyAreaA=1.074531in2ShearAreaAsy=0.5372657in2(=Asz)TorsionalstiffnessIxx=1.331494in4MomentofinertiaIyy=0.665747in4(=Izz)BoundaryConditionNodes1~4;ConstrainallDOFs.AnalysisCaseConverttheselfweighttonodalmassesandinputmanually.Numberofnaturalfrequenciestobecomputed=5Example363ResultsEigenvalueAnalysisResultsVerificationExample41stvibrationmodeofthestructure5thvibrationmodeofthestructureExample365ComparisonofResultsUnit:HzNaturalfrequencyANSYSSAP2000NISAIIMIDAS/Genf1111.5114.0111.46111.2f2115.9119.0116.10115.8f3137.6141.0137.50137.1f4218.0222.0216.20215.7f5404.2400.0405.00404.2ReferencesI.S.TubaandW.B.Wright,ASMEPressureVesselandPiping1972,“ComputerProgramsVerification”,ASMEPublicationI-24,Problem1“ANSYS,EngineeringAnalysisVerificationManual”,Revision4.4,SWANSONAnalysisSystems,Inc.,1990“SAP90,ASeriesofComputerProgramsfortheFiniteElementAnalysisofStructures,StructuralAnalysisVerificationManual”,Computersandstructures,Inc.,1992,Example4“NISAII,VerificationManual”,Version91.0,EngineeringMechanicsResearchCorporation,1991
