A simple member model for inelastic earthquake response analysis of three-dimensional steel frames with large deformation

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1.A simple numerical analysis method called 'inelastic joint mode., ' which is able to trace the inelastic behaviors of the steel members subjected to varying combined stress, is developed in this research. The behaviors of steel members can be simply demonstrated with several uni-axial inelastic springs.2.The steel members, are regarded as an assembly of two kinds of elements : one is an elastic beam element and the other is multi-spring inelastic joint. The inelastic joint is composed of several inelastic axial springs, shear panels and torsional spring. The skeleton curve of the inelastic spring is supposed to be the tri-linear type. A 'skeleton-shift model' is used for the inelastic springs here. A skeleton-shift factor is proposeded, which can be properly designed according to the available test data of uni-axial cyclic loading test of steel bars. By using the 'skeleton-shift model', the yielding, strain-hardening, stress degeneration caused by local bucking, the Bauschinger effect and the complicated hysteresis behavior can be easily considered.3.The appreciation of the parameters of the inelastic joint model is discussed. These parameters can be given proper values according to the material tests and the monotonic bending tests of beam-columns. An incremental analysis program is developed.4.The validity of the numerical analysis method is checked by the simulation of the loading tests of beam-columns subjected to varying axial load or varying grandience of moments. Numerical analysis results show good agreement totally with the loading tests, especially in the case of cyclic loading tests and earthquake loading tests.