Nonlinear FEM Analysis On Mechanical Behavior Of Joint Of Gangue Concrete Filled Steel Tubular Column-Steel Beam Under Reversed Low Cyclic Loads

The forces of process of Gangue concrete-filled steel tubular (GCFT) is the interaction between gangue concrete and steel tubular two different materials, which is the core gangue concrete strengthen by the steel tube.It has been strongly increased gangue concrete strength,plasticity, toughness owing to their composite action. In addition, it is lighter and more economical than the ordinary concrete filled steel tube. So far, gangue concrete-filled steel tubular has been widely used in engineering practice, but the beam-column joints research are not mature and perfect,the behavior of beam to column connections is the key of entire structure , which exists in the complex structure, difficult construction and high cost in the practical application and limits the development of concrete-filled steel tube. In this paper,this type of joints seismic behaviour and design approach were studied,specifically including the following tasks:Based on the appropriate material constitutive equation and failure criterion,interface model between the steel tube and the core gangue concrete are presented ,14 nonlinear finite element method models are set with ABAQUSThe stress distribution,microscopic mechanism and the failure mode of the steel tube and the gangue concrete core during the loading process are analyzed.Meanwhile,the P-Δand M-φhysteresis curves and the skeleton curves are calculated.The result show that:The hystersis curves are full and no obvious stiffness deterioration ,and the connections have a good energy dissipation capacity.The results of numerical simulations for load-displacement (P-Δ) enveiopes curves of the GCFT columns joints are verified against the experimental data. Generally, the numerical results show very good agreement with the experimental data which indicate that the finite element model and the material constitutive model adopted in this paper can simulate the GCFT beam-columns joints subjected to cyclic loading well.By establishing different finite element models,the influence of steel ratio, axial compression ratio,steel yield strength,the beam-to-column linear stiffness and the width of stiffening ring to hysteretic behavior are analyzed .The simplified Practical design approachs for the ultimate flexural and initial bending stiffness of the joints was proposed based on parameter analysis.According to the analysis of the nonlinear finite element calculating results, the influence of the parameters on load-displacement curve, stiffness degrading, Strength degradation energy absorption and displacement ductility is explored. The seismic behavior of the joints GCFT beam-columns is studied in depth.