Study On Seismic Behavior And Design Method Of Self-Centering Concrete-Filled Square Steel Tubular Column-Steel Beam Frame Joint With Wedge-Shaped Device

Self-centering structure is a new structure which can effectively control the residual deformation of the structure.After the earthquake,no need or little maintenance can restore the normal function of the structure.In this paper,a self-centering concrete-filled square steel tubular column-steel beam frame joint with wedge-shaped device(SCFJ),with simple structure,excellent self-centering behavior and good energy dissipation capability,is proposed.By using the method of experimental research,with finite element analysis and theoretical analysis,the mechanical mechanism,failure mode,seismic behavior and self-centering behavior of SCFJ are studied,and the design method of the joint is proposed.The main contents are listed as follows:(1)Based on the traditional beam-column joints and the existing self-centering beam-column joints,according to the requirements of self-centering behavior and the easy-to-repair after the earthquake,a SCFJ is proposed.The energy dissipation bars(ED bars)in SCFJ are used to dissipative energy,which avoid the influence of energydissipation components on the self-centering behavior of the structure,and reduces the requirement for the pre-tension of the steel strand.After the earthquake,the structure restores function quickly by replacing the ED bars and adjusting the position of the wedge-shaped devices.(2)The quasi-static tests of four SCFJ specimens are carried out to study their seismic behavior,self-centering behavior,carrying capacity,force mechanism and failure mechanism.The influence of initial post-tensioned(PT)force of steel strands,the diameter of ED bars and the placement of wedge-shaped devices on its performance is analyzed.The results show that the hysteretic curves of SCFJs are typical double-flag shape with great self-centering behavior and energy dissipation capacity.Under 4.00%drift,the residual deformation is less than 0.20%.The ED bars yielded while the column,beam and strands remained elastic,creating no damage to the main structural elements,which can achieve rapid repair after earthquake.Increasing the initial PT force can significantly increase carrying capacity of the joint.Increasing the diameter of the ED bar has a notable effect on the carrying capacity and energy dissipation capacity of the joint.Setting wedge-shaped devices allow the ED bar to fully dissipate energy.(3)The test specimens were simulated by ABAQUS 2017,and the hysteresis curve,skeleton curve,energy dissipation capacity,stress variation of steel strands and ED bars and other indicators of the test and finite element analysis are compared.The finite element results agree well with the test,which verifies the rationality and correctness of the finite element simulation.(4)The influence of the arrangement of the wedge-shaped devices,the diameter and yield strength of ED bars,the initial PT force,length and quantity of the steel stands on the performance of SCFJ is studied.The results show that the wedge-shaped device can improve the carrying capacity and energy dissipation capacity of the joint.Increasing the diameter of the ED bars or increasing the yield strength of the ED bars can increase the carrying capacity of the joint.Increasing the initial PT force,reducing the length or increasing the number of strands can increase the carrying capacity of the joint,but it will weaken the energy dissipation of the joint.Besides,increasing the initial PT force or increasing the number of strands increases the initial stiffness of the joint.(5)The calculation formula of the restoring force model is proposed,and the results were in good agreement by experiments and finite element verification.Based on the experimental and finite element results,combined with theoretical analysis,the design method of SCFJ is proposed.