Performance-based Seismic Design Of Self-centering Steel Concentrically Braced Frames

Conventional concentrically-braced frame(CBF)systems are a commonly used lateral force resisting system.These systems are economical and have excellent stiffness;however,CBFs have a low lateral drift capacity before serious damage of the main structural members initiates.This damage leads to residual lateral drift after the earthquake.Aiming at such disadvantages of the conventional CBFs as the limited drift capacity and the significant residual drift,a kind of self-centering system has been developed and become the focus of seismic research in recent years,a self-centering concentrically-braced frame(SC-CBF)system can desirably resist earthquake loading without structural damage or residual drift.A SC-CBF is a concentrically-braced frame with column base details that permit column uplift and rocking at a specified level of lateral force.The vertically-oriented post-tensioning bars provide restoring force and self-centering behavior that reduces the potential for residual drift.This paper briefly stated the behavior of the SC-CBFs,recognized four primary structural limit states of an SC-CBF:column decompression,PT bar yielding,member yielding,member failure,and introduced the behavior of the structural limit states.Based on the basic theory of performance-based seismic design,the performance levels and objectives of the SC-CBFs are determined.The performance-based seismic design(PBSD)approach and evaluation methods are investigated in this paper,and the feasibility of this method is verified by a case study.A conventional concentrically-braced steel fame model of 12 stories and a self-centering concentrically-braced steel frame model were established in SAP2000,the nonlinear static analysis and the elastic-plastic dynamic analysis of both systems were carried out to evaluate their seismic performances.The results indicate that: the seismic performance of the self-centering concentrically-braced steel frame is better than that of the conventional frame;under the strong earthquakes,the former has a lower or no residual drift;the roof drift and the base shear of the self-centering concentrically-braced steel frame is much less than that of the conventional frame.