Cyclic Behavior Of Composite Joints Between Square Hollow Steel Tube-reinforced Concrete Columns And H-shaped Steel Beams

The hollow concrete-filled steel tubular composite column has evolved from the concrete-filled steel tubular composite column.It is a new type of structural component with a very broad prospect in the engineering field.In recent years,the research on the mechanical properties of the component by the majority of scholars is becoming more and more perfect,but the research on the joint field is very few.In this paper,the seismic behavior of the hollow concrete-filled steel tubular composite column-h-shaped steel beam joint is explored in detail through the method of combining test and simulation.The main work is divided into the following parts:Based on the main parameters of axial compression ratio,sleeve thickness and flexural rigidity of beams and columns,the hysteretic behavior of four concrete-filled square hollow steel tubular composite columns H-beams is studied.In the loading mode,a fixed and constant axial pressure is applied at the top of the column,and then a reciprocating load is applied at the loading points at both ends of the beam.Based on the P-? curve obtained from the test,the strength degradation,stiffness degradation,ductility and energy dissipation capacity of the joint under the reciprocating load are analyzed in detail.The experimental results show that the hysteretic curve of the joint under the action of reciprocating load is relatively full,the ductility and stiffness of the joint are stable,the failure of the specimen is the bending at the variable cross-section of the beam end,resulting in the loss of bearing capacity of the specimen.Therefore,this type of joint has good seismic performance.The model of concrete-filled square hollow steel tubular composite column-h-beam joint is established by ABAQUS.The model considers geometrical nonlinearity and material nonlinearity.In the process of establishing the model,the plastic damage degradation effect of concrete material under the action of reciprocating load is considered,and the contact relationship between sleeve and concrete,concrete and inner steel tube is established.The accuracy and reliability of the finite element model are verified by the existing experimental results.According to the comparison between the test results and the finite element method,the working mechanism of the concrete-filled square hollow steel tube composite Column-H steel beam joint is analyzed.The stress and the ultimate failure mode of the joint in the elastic,elastic-plastic and plastic stages are studied.The influence of sleeve thickness,axial compression ratio,beam column bending capacity and other factors on the joint failure resistance is analyzed in detail.