Seismic Performance Test And Analysis Of A New Series Self-centering Buckling Restrained Braces

Self-centering Buckling-Restrained Brace(SC-BRB)has good hysteretic behavior and self-centering ability.It can effectively control the seismic response through the self-centering system of tube-BFRP pre-tensioning rod and reduces or even eliminates residual deformation,thus improving the repairability of structure after the earthquake.However,under the action of Maximum Credible Earthquake,due to the elastic elongation limit of the pre-tensioned rod material,it is difficult to meet the large deformation demand and the pre-tensioning rod fracture occurs,resulting in large structural seismic response and residual deformation,increasing the difficulty and cost of repair.Based on above problems,in order to improve the seismic performance of the brace under large deformation conditions and effectively control the seismic response of the structure under the action of MCE,this paper proposes the design of the series SC-BRB.The main research contents are as follows:(1)Based on the structure of SC-BRB,a series design is proposed.The self-centering working mechanism and the series working mechanism of the brace are explained,and the stiffness and restoring force models of each stage are derived.The design method,installation and assembly process are proposed.The hysteretic behavior and energy consumption capacity are studied by a 1/4 scale model;(2)A series SC-BRB were designed and processed.Firstly,the variable amplitude and constant amplitude quasi-static tests were carried out at a loading rate of 0.1 mm/s to verify the series mechanism and study its seismic performance.The results show that the series structure doubles the deformation capacity but does not affect its self-centering ability.The brace has a stable and full hysteresis curve,the residual deformation is small,the tension and compression are symmetrical,and the cumulative plastic deformation is satisfied.The brace has stable performance under normal amplitude loading corresponding to 3% residual displacement angle.In order to study the performance of the support under the secondary loading after the earthquake,the failure test was carried out at a loading rate of 0.2 mm/s.The results show that the hysteretic behavior and energy dissipation capacity of the support are still relatively stable,and the energy consumption of the support is increased after increasing the loading rate as well as the residual deformation.When the self-centering system was damaged,it degraded to the hysteresis characteristics of BRB.(3)Considering the tube length error,the numerical analysis of the series SC-BRB is carried out by ABAQUS software.The results are basically consistent with the experimental and theoretical values.The first stiffness and the second stiffness are close to each other,and the machining error of the brace is well simulated by considering the tube length error,which verifies the effectiveness of the finite element model.On this basis,the parameters of the pre-tensioned rod size,initial pre-tension and core plate area are discussed as well as the multi-wave buckling phenomenon of the brace.The results show that when the size of the pre-tensioned rod is increased,the second stiffness and the maximum axial force of the series SC-BRB support are increased,and the residual deformation of the support is reduced.When the initial pre-tension is increased,the bearing capacity and the residual deformation is increased,and the multi-wave buckling wave number of the core plate is reduced.When the core plate area is increased,the first stiffness,the second stiffness and the bearing capacity of the brace are increased,the residual deformation is increased,the self-centering capability is reduced,and the energy consumption is reduced,and the wavenumber of multi-wave buckling and the strain at the trough are reduced.(4)Establish the SC-BRB model that can consider the pre-tensioned rod fracture,and the seismic performance of the series SC-BRB frame and the non-series SC-BRB frame under the action of DBE and MCE through Opensees software.The results show that under the action of DBE,the two types of brace have similar seismic responses.Under the action of MCE,the pre-tensioned rods in the non-series SC-BRB reach the ultimate strain and fracture,and the brace degenerates to the working state of BRB.The overall lateral stiffness of the frame is reduced,the displacement response and residual deformation are increased,while the series SC-BRB can still work stably.It controls the residual story drift angle after the earthquake,dissipate seismic energy and enhance the ductility of the frame.