Evaluation of Capacity Spectrum Method for Estimate of Seismic Performance in Buckling-Restrained Braced Frame

In the performance-based design, determination of performance and evaluating the structure and its components requires to assess the seismic capacity and demand. In order to achieve these goals, analytical methods with high capabilities of modeling the structure and seismic excitations are required. Linear and non-linear approaches were introduced as analytical methods for rehabilitation pre-standard, where both of them can be done statically or dynamically. Among nonlinear methods, usage of nonlinear static analysis (Pushover analysis) for evaluating the structures is proliferated. This analysis aimed on evaluating the expected performance of structural system and estimating the resistance and deformation demands of it in design earthquake. These demands are compared to the existed capacities of target performance levels. In order to calculate the target displacement or performance point, different methods such as Capacity Spectrum Method (CSM) in ATC-40 [1] and Coefficient Method in FEMA-356 [2] were introduced. However, based on previous researches, the observed results of applying these methods for identical structures were dissimilar. Therefore, FEMA-440[3] proposed two enhanced methods to modify these methods and convergence of their outcomes. The aim of this study is to investigate and compare the accuracy of capacity spectrum method introduced by ATC-40 with modified capacity spectrum method of FEMA-440 for evaluating the seismic performance of Buckling Restrained Braced Frame (BRBF).