Study On Seismic Behavior Of Reinforced Circular CFST Column Steel Beam Joint In Core Area

The concrete-filled steel tube structure has high bearing capacity,strong anti-seismic capacity and remarkable economic effect,which has been widely used in various engineering fields.According to the design concept of CFST,the mechanical performance of circular CFST is the best,but in the actual project,the connection between circular CFST column and steel beam is not easy to handle,so it is difficult to achieve good mechanical performance of joints,simple structure and convenient construction,Therefore,based on the research results of circular CFST beam column joints at home and abroad,this paper proposes a joint form of reinforced circular CFST column and steel beam in the core area.The steel beam and circular CFST column in this kind of joint are connected by square sleeve,which is simple in structure,less in steel consumption and convenient in construction The main research contents and achievements of experimental research and finite element analysis under action are as follows:A new type of reinforced circular CFST column steel beam joint in core area is put forward innovatively.Three joint specimens are designed and manufactured and tested.The corresponding failure process is described in detail,and the seismic performance indexes of each specimen are analyzed.The results show that: the joint designed in this paper has high bearing capacity and strong energy dissipation capacity,all indicators meet the requirements of the code;increasing the ratio of beam to column linear stiffness can greatly improve the bearing capacity and stiffness of the joint,but it will reduce the energy dissipation capacity of the joint,when the ratio of beam to column linear stiffness increases to a certain extent,the failure of the joint may transform from the failure of the beam end to the failure of the column end;in the joint Adding welding seam in the joint area can effectively improve the bearing capacity of the joint,but it will reduce the ductility of the joint;by setting stiffeners and haunched plates in the joint area,it can effectively avoid the stress concentration phenomenon at the steel beam and end plate,make the plastic hinge generated by the damage move out,avoid the damage of the joint area,and meet the seismic requirements of "strong joint and weak component".Based on the test results,the three-dimensional nonlinear finite element simulation of the reinforced circular CFST column steel beam bolted joint in the core area under the action of low cycle reciprocating load is carried out by using the finite element software ABAQUS.The failure form,hysteretic curve and skeleton curve of the test piece are obtained and by comparison with the test results.The results show that the hysteretic curves and skeleton curves of the two are similar,the coincidence is good,the failure mode is the same,and the difference between yield load and ultimate load is small.Based on the finite element analysis,the parameters of the model,such as axial compression ratio,concrete strength grade,steel strength and beam column linear stiffness ratio,are changed to study and analyze the influence degree of these factors on the seismic performance of this kind of joint.The results show that the larger the axial compression ratio,the stronger the energy dissipation capacity,the lower the bearing capacity and the worse the ductility;the concrete strength grade has no effect on the seismic performance of such joints;the higher the steel strength to the beam column linear stiffness ratio,the higher the bearing capacity of the joints,but the ductility of the joints changes with the increase of the beam column linear stiffness ratio.