Study On BRB On Seismic Performance Of Irregular Tall Structure Beyond The Code-specification Based On Seismic Fragility Analysis

With the highly development of economy, more and more irregular tall structures beyond the code-specification are appearing in China with complex buildings shape, irregular layout, functional diversification. Based on a large number of statistical analyses and researches of earthquake damage, both irregular plane and vertical irregularity can cause structural damage or collapse, which has significant adverse impact on the seismic performance of the structure. Obviously, it's a key issue of seismic studies to assure the seismic performance of irregular tall structures beyond the code-specification. It's an effective way to solve the problem by using the technology of buckling-restrained braces energy dissipation in improving the seismic safety of structure. It's an active seismic disaster prevention technology by using the BRB to control structure damage, but it's unknown that how much emergency capecity BRB can provide for irregular tall structures beyond the code-specification. Therefore, it's crucial to reveal the relationship between main performance parameters of BRB (the initial stiffness, yield strength and yield stiffness ratio) and the seismic performance of irregular tall structures beyond the code-specification, and establish the relationship between main performance parameters of BRB and seismic reliability of irregular tall structures beyond the code-specification.This paper takes one irregular tall frame-shear wall structure beyond the code-specification as research object, studying the influence of BRB on lateral force resistance, seismic response, damage severity and the vulnerability assessment by adopting pushover analysis, nonlinear dynamic analysis and seismic fragility analysis method.The main work and conclusions are as follow:(1) As the ground motions and structural parameters are the key parameter to evaluate the seismic performance of complex high-rise structures, this paper consider the influence of BRB on ground motion intensity parameter sensitivity analysis of complex high-rise structures, and propose a reasonable methods for ground motion intensity parameter sensitivity analysis. This paper takes one irregular tall frame-shear wall structure beyond the code-specification as research object, to study the influence of BRB on ground motion intensity parameter sensitivity analysis and select the more accurate round motion intensity parameters. Studies have shown that the BRB has a great influence on ground motion intensity parameter sensitivity analysis for irregular tall frame-shear wall structure beyond the code-specification. The sensitivity analysis has great discreteness, which has great influence on the rationality of assessment on seismic performance of complex high-rise structures. The peak ground motion velocity PGV has the greatest influence on structural seismic demand, which is suitable for the evaluation parameter used in the structural seismic fragility analysis.(2) In order to fully evaluate influence of BRB on seismic performance of irregular tall structure beyond the code-specification, this paper studies the influence of BRB on lateral force resistance, seismic response, damage severity and the vulnerability assessment by adopting pushover analysis, nonlinear dynamic analysis and seismic fragility analysis method. Dynamic characteristics analysis has shown that BRB can improve the overall stiffness of structure, reducing the torsional effect. Pushover analysis has shown BRB can improve the lateral stiffness, bearing capacity and ductility of structure. Nonlinear dynamic analysis has shown that BRB can improve the stiffness of structure and dissipate a large amount of seismic energy by taking advantage of plastic deformation. So the vertex acceleration and base shear have been increased, the vertex displacemen, the overall plasticity hysteretic energy, the maximum inter-story drift angle and the damage degree of shear wall and column have been decreased, with the structure does not appear significant inelastic state. Seismic fragility analysis has shown that BRB can effectively reduce the exceeding probability of seismic demand fragility curves of irregular tall frame-shear wall structure beyond the code-specification in different limit states, but the influence is gradually reduced with the ground motion intensity increases.(3) The the mechanical properties of BRB are determined by the main performance parameters composed by the initial stiffness, yield strength and post-yield stiffness ratio. The influence of BRB on seismic performance of structures can be changed by the main performance parameters. This paper establishs the irregular tall frame-shear wall structures beyond the code-specification with different performance parameters of BRB, and studies the influence of the different performance parameters on the the vulnerability assessment of irregular tall frame-shear wall structure beyond the code-specification based on the seismic fragility analysis to fully evaluate the influence of BRB on seismic performance of complex high-rise structures. The results of analysis has shown that the exceeding probabilities of seismic demand fragility curves of irregular tall frame-shear wall structure beyond the code-specification have been reduced with the growth of performance parameters, but the growth trend has been smaller and smaller. The influence of initial stiffness on the seismic vulnerability assessment results is the largest, the influence of initial stiffness is the least.