Design And Seismic Performance Study Of A Novel Self-centering Damping Energy Dissipation Brace

Most self-centering energy dissipation braces usually adopt shape memory alloys or pre-pressed tendons to offer self-centering ability to return to their initial position,but the thermo elastic martensite of shape memory alloy is obviously affected by temperature,and it need to be heat treated to realize self-centering ability,and due to the small elastic deformation of prestressed tendons,the engineering application is limited.Based on this,an innovative self-centering damping energy dissipation brace,which utilizes combination disc springs to supply self-centering force,a permanent magnet to produce the constant magnetic field and rheological properties of Magnetorheological(MR)fluid to dissipate input energy of earthquakes,has been proposed in this paper,and the design requirements of stiffness,deformation and restoring force of the brace can be realized by changing the combination form of the disc spring,so as to meet the requirement of the structure to the interstory drift and lateral stiffness.In this paper,the theoretical analysis and experimental study on the seismic performance of the self-centering damping energy dissipation brace are carried out,and the double Bouc-Wen restoring force model which can accurately portray the hysteretic behaviors of the brace has been established.The main contents are as follows:(1)A new type of self-centering damping energy dissipation brace is developed,and the configuration and the performance at each stage of the force are analyzed.The segmentation model is developed to portray the performance of brace according to the elastic deformation of inner tube and guide shaft,the bilinear elastic model of disc springs and the bingham model of MR fluid.(2)The finite element numerical simulation analysis of the self-centering damping energy dissipation brace with 1.5m long and coulomb damping force of 200kN is carried out,the changing rules of hysteretic behavior,energy dissipation capacity and equivalent viscous damping ratio under sinusoidal excitation with different frequency and amplitude,different initial pre-pressed force and combination disc spring stiffness are researched.Hysteretic curves of the brace exhibits full flag shape,and the increment of energy dissipation and restoring force is proportional to the increment'of loading amplitude.With the increase of the loading frequency,the hysteretic curves at the same displacement are more full,and the equivalent viscous damping ratio decreases stably with the increase of the loading displacement,which indicates that the brace has good hysteretic behavior and stable energy dissipation capability.Results of the segmentation model and solid finite element simulation are compared,the hysteretic curves are in a good agreement,the maximum relative error of restoring force and energy dissipation is less than 10%,which shows that the segmentation model can precisely describe the hysteretic behavior of the brace and provide an important reference for the parameters design of brace.(3)A self-centering damping energy dissipation brace with a length of 1.5m is fabricated,and the dynamic tests of the energy dissipation system under sinusoidal excitation with different frequency and amplitude are carried out.Results show that the hysteretic curves of the energy dissipation system is full,the energy dissipation capablility is stable,and the damping force increases with the increase of loading frequency and amplitude,and the maximum viscous damping force accounts for about 40%of the maximum damping force.The dynamic tests of the self-centering damping energy dissipation braces with different initial pre-pressed force of disc springs due to the sinusoidal excitation with different frequency and amplitude are carried out.Hysteretic curves of the brace exhibits full flag shape,when the initial pre-pressed force of disc springs is greater than the damping force of the energy dissipation system,there is almost no residual deformation,when the initial pre-pressed force of disc springs and damping force are equal,the residual deformation becomes larger with the increase of loading frequency and amplitude.When the load is removed,the brace can still return to its initial position,and which indicates that the self-centering capability of the brace is not affected by the increase of viscous damping force.When the initial pre-pressed force is less than the coulomb damping force of the energy dissipation system,a large residual deformation occurs and accounts for 45%of the maximum deformation,and the energy dissipation capability of brace increases nonlinearly with the increase of the displacement and the loading frequency,the viscous energy dissipation accounts for about 40%of the total energy dissipation.Therefore,the brace has good energy dissipation characteristics and stability.(4)In order to accurately simulate the dynamic characteristics of brace during the nonlinear analysis of structure,through the improvement of traditional Bouc-Wen model,a restoring force model is established to portray the hysteretic behavior of the self-centering damping energy dissipation brace,and the improved double Bouc-Wen model is simulated in simulink environment.Comparisons between the simulation and the finite element analysis are conducted,the hysteretic curves obtained from simulink and finite element simulation are in good agreement,and the bearing force and energy dissipation error are controlled within 10%.Comparisons between the hysteresis curves obtained from the double Bouc-Wen model and experiments are also conducted,and the results show that the hysteresis curves are highly consistent,and the maximum error is 9.8%and the average error is less than 5%,which shows that the double Bouc-Wen model can accurately describe the hysteretic behavior of the self-centering damping energy dissipation brace.(5)The secondary development program of the improved double Bouc-Wen model is developed based on OpenSees platform,and using a 9-story benchmark steel frame structure as a numerical example,comparisons of the seismic performance between structure with self-centering damping energy dissipation braces and structure with buckling restrained braces are conducted.The double Bouc-Wen model can well describe the hysteretic behavior of the self-centering damping energy dissipation braces in OpenSees.Compared with structure with buckling restrained braces,the average maximum interstory drift of structure with the self-centering damping energy dissipation brace is reduced by 11.54%under 5 different earthquakes with PGA of 0.6g,and compared with the original steel frame structure,the average maximum interstory drift is reduced by 53.3%.In addition,the residual deformation of the structure with self-centering damping energy dissipation braces compared to the original steel frame structure is reduced more than 95%,compared with the structure with buckling restrained braces is reduced by 85%,the self-centering damping energy dissipationbrace has good energy dissipation and self-centering capabilities.