Seismic Performance Of Beam-Tocolumn Connection With Mechanical Hinge And Buckling-Restrained Steel Plates And The Steel Frame Structure

The steel structure has the advantages of light weight,high strength,easy assembly,and environmental protection.It has great development prospects in the field of prefabricated buildings.The introduction of energy dissipation devices into prefabricated steel structure buildings reduces the damage of the main structure and improves the seismic performance of the structure.This dissertation proposes a new type of prefabricated energy dissipation beam-to-column connection——beam-tocolumn connection with a mechanical hinge and buckling-restrained steel plates.It consists of a steel column,a cantilever beam,a steel beam,a mechanical hinge and a pair of buckling-restrained steel plates.The connection uses a mechanical hinge to bear the shear force,and a pair of buckling-restrained steel plates to bear the bending moment.The load-bearing mechanism is clear and the parameters can be designed efficiently.When the steel plate is compressed,due to the existence of the doublesided restraint members,the instability of the plate will not occur,so that the connection has a stable load-bearing and energy dissipation capacity.Through a reasonable design of the connection strength,the ideal failure mode of "weak beam and strong column" can be effectively realized.This dissertation investigates the seismic performance of the beam-to-column connection with a mechanical hinge and buckling-restrained steel plates and the corresponding steel moment frames equipped with the mechanical hinge connections,with a combination of theoretical analysis and experimental research methods.Specifically,following research contents have been completed:(1)Based on the load-bearing mechanism of the beam-to-column connection with a mechanical hinge and buckling-restrained steel plates,the formulas for the connection mechanical parameters are proposed,and the detailed design process of the connection under four design principles is given.A refined finite element model of the beam-to-column connection with a mechanical hinge and buckling-restrained steel plates based on the ABAQUS software is established,and the effects of key parameters on the overall stability of the connection are studied.A comprehensive numerical analysis is conducted and design parameter suggestions are given.On this basis,the influence of the design parameters on the yield bearing capacity of the connection is studied,and the accuracy of the theoretical formula for the calculation of the connection yield bending capacity is verified.In order to facilitate the structural analysis,a simplified analysis model of the connection——the "equivalent rotation spring model" is proposed,and the accuracy of the model is evaluated based on the monotonic loading curve.(2)Three groups of different forms of full-scale beam-to-column connection with a mechanial hinge and steel plates are designed,including: channel type steel plate connection,buckling-restrained channel type steel plate connection and buckling-restrained flat steel plate connection.The cyclic loading tests and low-cycle fatigue tests of three connections are completed.Firstly,according to the bearing and deformation characteristics of the specimens measured during the test,the skeleton curve,the curve of the enclosed area of the hysteresis loop,the energy dissipation curve and the equivalent damping ratio curve of the specimens are obtained,then the the load-bearing capacity,ductility and energy dissipation characteristics of the specimen are studied.Secondly,according to the experimental phenomena such as buckling and crack development of the steel plates observed during the test,the loadbearing mechanism and failure mode are analyzed.Finally,according to the American Code for Seismic Design of Steel Structures and the Chinese Code for Seismic Design,the effectiveness of the three types of connections is verified and evaluated.(3)Based on the Japanese E-Defense 18-story steel frame shaking table test results and Open Sees analysis platform,an effective nonlinear steel moment frame model is established,and the influence of mechanical hinge connection on the seismic response of the 18-story steel moment frame is studied.Firstly,based on theoretical analysis,the effect of the equivalent stiffness of the mechanical hinge connection on the lateral displacement of the steel moment frame is studied.Based on the "threelevel" seismic fortification goal and the "two-stage" design method of the Chinese seismic code,the seismic design method of the steel frame-mechanical hinge connection structure is proposed.On this basis,a 6-story and 12-story structure are designed with conventioanl steel frame structure and steel frame-mechanical hinge connection structure,respectively.The effects of design parameters of mechanical hinge connection on the strucutures under rare and super rare earthquakes are studied.To solve the problem that the seismic responses of the 12-story structure exceeds the code limit under super rare earthquakes,structure failure path and plastic hinge failure probability are obtained based on the single-run multi-modal Pushover analysis method and then the structural failure mode optimization method is used to improve the seismic performance of the structure,and the effectiveness of the method is verified.(4)The performance-based plastic design method for the steel frame-mechanical hinge connection structure and steel frame-mechanical hinge connection-bucklingrestrained brace dual system is developed to ensure the ideal failure mode of "weak beam and strong column".For the former structure,the method first uses the modified energy balance equation to obtain the structural design base shear force.Based on the expected failure mode of the structure and the lateral force distribution pattern of the structure under strong earthquakes,the bending strength of the connections is obtained,and the plastic design of the frame beams and columns is carried out.For the latter structure,the total structure system is divided into two independent substructure systems.Two design parameters——the base shear force ratio and yield displacement ratio are used to ensure a reasonable lateral force distribution and yield sequence of the sub-systems,so that the structure can enter the plastic state in sequence under increasing ground motion,with sufficient energy dissipation margin to withstand continuous increased intensity of ground motions.The plastic design method is adopted to design a 12-story steel frame-mechanical hinge connection structure and a 30-story dual system.The proposed design method is verified by the seismic response analysis under a rare earthquake.