Finite Element Analysis Of Seismic Behavior Of Joints With Concrete-filled Steel Tubular Column And Unequal Depth Steel Beam

The special-shaped joints of concrete-filled steel tubular(CFST)columns are widely used in high-rise buildings and long-span industrial factories.However,the research on joints with concrete-filled steel tubular column and steel beam is mainly aimed at conventional joints,rarely involving special-shaped joints with unequal depth steel beams,and the research parameters are relatively single and lack of detailed analysis of the working mechanism.In this paper,the seismic behavior of joints with concrete-filled square steel tubular column and unequal depth steel beam is studied through experimental and finite element analysis.The main research work is as follows:1.The numerical model of joints with concrete-filled steel tubular column and unequal depth steel beam was established.According to the different constraints,the fiber sections of confined concrete were finely divided,and the fibers of different uniaxial material constitutive models were defined to simulate their different stress-strain relations.Considering that the joints with beam and column in the OpenSees platform were connected in rigid domain by default,the joints was comprised of advanced fiber beam-column elements,non-linear springs and shear panel to reflect its actual mechanical performance.The calculated results of the finite element models were in good agreement with the experimental results.2.The parametric analysis was conducted to investigate influences of key parameters on the seismic performance of joints with concrete-filled steel tubular column and unequal depth steel beam.The specific parameters included: the ratio of left side beam height and right side beam height,steel ratio of column section,test axial compression ratio,steel pipe strength grade,core concrete strength grade,stiffness ratio of beam to column and so on.The seismic behavior of this kind of joints was further analyzed by the model calculation,such as bearing capacity and stiffness degradation,energy dissipation capacity,failure mode of specimens and so on.Based on experimental research and finite element simulation,the failure modes and process were investigated,and the key factors influencing the failure pattern of the joints were clarified.3.Based on the results of parameter analysis and the current code,the theoretical formula of shear capacity were developed for panel zone of joints with concrete-filled steel tubular column and unequal depth steel beam.The core zone shear model of joints with concrete-filled steel tubular column and unequal depth steel beam was proposed through experimental and finite element analysis.A method for calculating the shear capacity of the joint core area is put forward,which is composed of the steel tube webs of the panel zone,the concrete of the panel zone,the steel tube flange of the panel zone and the external stiffening ring.The calculated results of the model are in good agreement with the experimental results and the finite element results.