Study On Seismic Behavior Of Steel Frames With T-shaped Steel Self Centering Joints

Steel structure has the advantages of light weight,good seismic performance,easy transportation and installation,recyclable and so on.The most important thing of steel structure is the design of its beam column joints.The beam column joints can be connected by welding with high stiffness,bolt with low stiffness and semi-rigid connection between them.In this paper,according to the existing literature,the semi-rigid joints connected by bolts are improved,which is also an improvement of the existing self reset joints.Most of the existing self reset joints use angle steel to dissipate energy.In this paper,the prestressed reinforcement is applied to the semi-rigid joints of T-shaped steel,that is,the angle steel in the existing angle steel energy dissipation self reset joints is replaced by the T-shaped steel with better energy dissipation performance Section steel.The node has the ability of self reset,at the same time,it has stronger energy consumption performance and ensures the ductility of the node.Firstly,a standard node is designed.According to the standard node,the node parameters are changed,and 13 node variable parameter models are set.The variable parameters are divided into four series: cm(connect mode)series specimens,BP(bolt parameters)series specimens,TS(T steel)series specimens,PR(suppressed reinforcement)series specimens.The 13 models with different parameters were simulated,By comparing the simulation results,the influence of different parameters on the performance of T-beam self reset joints is explored.The results show that the semi-rigid joints without prestressing tendons do not have self reset performance,and the self reset joints can meet the requirements of no plastic deformation of beams and columns after earthquake,and the post earthquake repair is easier than the traditional welded frame.The results show that the influence of bolt grade and(within a certain range)prestressed tendon length on the self reset joint is small;the increase of bolt number,T-section steel thickness,T-section steel material grade and T-section steel flange height will improve the initial stiffness,maximum bearing capacity and energy dissipation capacity of the joint,but the self reset capacity of the joint will be reduced accordingly.The increase of initial prestress and the number of prestressed tendons will improve the maximum bearing capacity,initial stiffness,energy dissipation capacity and self reset capacity of the joint.If the initial prestress of prestressed tendons is too large,it will cause brittle failure of the joint,and the initial prestress of the joint should be controlled.Finally,the connection element method of finite element software is used to establish the self reset steel frame,and the joint performance is substituted into the frame.The response of self reset steel frame and welded steel frame under different seismic waves is compared,and the different arrangement of self reset joints is studied.The results show that: the self reset steel frame has smaller story residual displacement after the earthquake,and the beams and columns are in elastic state after the earthquake,which can achieve the design concept of self reset steel frame.Through the research on the location of the self reset joints in the self reset steel frame,it is concluded that the self reset performance of the steel frame with the self reset joints only in the side column is better than that of the steel frame with the self reset joints only in the middle column.And each reset node can meet the original design intention of "repairable and easy to repair".