Research On Seismic Performance For A New Type Buckling-restrained Brace With Multi-point Dispersing Energy Dissipation Devices And Structure Seismic Fragility Analysis

In recent years,there are increasing soft-first-storey buildings.The upper structure of these buildings is used for residential or office buildings,while the lower structure is used for commercial buildings or garages.The Marshal Hotel and Yuncui Building in Taiwan are examples of such buildings.During the Hualien earthquake in Taiwan in 2018,the concrete at the bottom floor column end of the building was seriously damaged and deformed,leading to the serious structural damage and collapse.As a result,heavy casualties and huge economic losses are generated.Energy dissipation structure is highly valued by scholars due to its characteristics such as its good damping effect,simple structure and convenient maintenance.Therefore,energy dissipation technology has been developed rapidly and gradually applied to the damage control of frame structure with soft first storey.The existing research on buckling restrained braces only has the first-order stiffness after yielding.Besides,the research on buckling restrained braces which can provide additional second-order stiffness is less.In this thesis,a new type buckling restrained brace with multi-point dispersing energy dissipation devices is proposed.Moreover,the brace can dissipate seismic energy and provide additional second-order stiffness for the structure,which contributes to reducing the lateral deformation and improving the overall seismic performance of the structure.This study mainly investigates the seismic performance for a new type buckling restrained brace with multi-point dispersing energy dissipation devices and the damage control of frame structure with soft first storey.The main contents and conclusions are presented as follows:(1)As shown in Chapter 2,five steel braces are designed,and the limitation displacement,limitation block number,steel core section size and length are chosen as the design parameters.Based on the test study,the characteristics including the failure mode,hysteresis loops behavior,skelton curves and stiffness are demonstrated.The results show that the steel brace structure is reasonable with stable hysteretic performance,the position limitation block could play a limiting role and provide greater additional stiffness.The number and section size of the position limitation block and the weld stiffness of the joint surface with the steel core affect the lifting degree of the additional stiffness.The deformation capacity of the steel brace with small working section is the worst,and the bearing capacity of the brace decreases obviously with the decrease of steel core section,and the fullness of hysteretic curve is weaker than other braces.The calculation results of the stiffness formulas presented in this thesis are in good agreement with the experimental values,which can provide reference for the practical design of steel braces.(2)As shown in Chapter 3,ABAQUS finite element software is employed to model and analyze five buckling restrained braces with multi-point dispersing energy dissipation devices.In addition,the setting methods of steel constitutive,analysis steps,contact,boundary conditions,mesh generation,solid element and other parameters are clarified.The hysteretic curves obtained from the finite element analysis are compared with the experimental results to confirm the correctness of the numerical model and the rationality of the parameters.Through carrying out the comparative analysis,it can be found that the ABAQUS finite element numerical simulation results are basically consistent with the test results.At the same time,there is little difference in the stiffness and peak bearing capacity of the elastic and plastic stages,which can better simulate the hysteretic performance of the brace.(3)As presented in Chapter 4,based on incremental dynamic analysis,the seismic vulnerability analysis of the structure model of soft-first-storey structures and soft-first-storey structures with new buckling-restrained brace is carried out,aiming to discuss the feasibility of the new buckling-restrained brace to enhance the seismic collapse resistance of the frame structure with soft first storey.According to the obtained results,collapse reserve coefficient of soft-firststorey structures with new buckling-restrained brace is improved,which is conducive to improving the collapse resistance of the structure with soft first storey.