Seismic Performance And Residual Deformation Analysis Of Steel Frame With Self-centering Joints Under Mainshock-aftershocks

The earthquake usually occurs in sequence.After the main-shock,it is often accompanied by aftershocks,which will cause further damage to the structure.Therefore,the impact of aftershocks on the structure cannot be ignored.Compared with the traditional rigid joint,the self-centering joint has the advantages of small residual deformation and controllable damage.However,present research on the seismic performance of the self-centering joint only considers the single main earthquake action.How the seismic performance of self-centering joints under the action of the mainshock-aftershock sequence will change,and what factors will affect its seismic performance in the aftershock are worthy of further study.The research object of this paper is the top-seat angle connecting self-centering joint.The beam and the column of the joint is connected by angle steel,high strength bolt and prestressed steel strand.Under the earthquake action,the energy is dissipated by the plastic deformation of angle steel,and the self reset function is realized by prestressed steel strand.In this paper,a self-centering beam-column edge joint of steel frame is designed,and the low cycle cyclic loading test is carried out.In order to simulate the effect of mainshock-aftershocks,five displacement loading systems are designed.Each loading system includes two identical loading stages.The maximum displacement loading levels are1% rad,2% rad,3% rad,4% rad and 5% rad respectively,so as to simulate the influence of main and aftershocks of different intensities on the joint.In addition,the joint is repaired after loading,so as to explore its repairability.Secondly,the refined solid model of self-centering joint is established by using the finite element analysis software ABAQUS.The simulation results of finite element agree well with the experimental results,which proves the correctness of the modeling method.On this basis,the thickness of the steel angle,the position of bolts,the vertical spacing of steel strand,the initial tension of steel strand and the number of steel strand are analyzed,and the hysteretic performance,skeleton curve,energy dissipation capacity and tension change of steel strand are compared.The results show that: the greater the thickness of angle steel,the stronger the energy dissipation capacity of the joint,and the energy dissipation capacity will be retained to a greater extent under the aftershock,but the residual deformation of the joint will increase;the bearing capacity and energy dissipation capacity of the joint can be improved by reasonable arrangement of bolts;the vertical spacing of steel strands has little effect on the seismic performance of the joint,but increases the initial tension and increase of the steel strand The number of large steel strands can significantly improve the bearing capacity and reduce the residual deformation of joints,and improve the seismic performance of joints under aftershocks.Finally,the simplified models of the self-centering frame and the traditional rigid frame are established respectively,and then three suitable ground motion records are selected to construct the mainshock-aftershock sequence,and the amplitude of the main shock is adjusted to the level of 8 degree rare occurrence.The after-shock intensity is adjusted according to the peak acceleration ratio of the aftershock and the main shock,taking 0.4,0.6,0.8 and 1.0 respectively.The mainshock-aftershock sequence of the structure is input into two frames for dynamic time history analysis,and the overall response under the mainshock-aftershock is studied.Through the comparison of the calculation results,the main conclusions are as follows: the story drift angle of the self-centering frame is slightly larger than that of the rigid frame,but the maximum base shear,residual story drift angle and energy consumption capacity are all smaller than that of the rigid frame;when the aftershock intensity is close to the main earthquake,the self-centering frame shows stronger ability to resist aftershock compared with the rigid frame;when the residual deformation is taken as the judgment The repairability of the self-centering frame is better than that of the rigid frame.