Masoud Ghamari - Corresponding author: civil engineering department, Bu-Ali Sina University, Hamedan, Iran
Mohammad Shooshtari - Civil engineering department, Bu-Ali Sina University, Hamedan, Iran
Sara Naeimi - Civil engineering department, Bu-Ali Sina University, Hamedan, Iran

Buckling Restrained Braces (BRBs) are frequently used in structures since they dissipate the seismic energy without failure. Their performance and effectiveness vary with the seismic structural system. On the other hand, most buildings are irregular, and their seismic behavior differs from regular structures. This paper investigates the fragility of regular and irregular steel structures with BRBs. Eight five-story and eight ten-story ۳D buildings are designed; half use Special Concentrically Braces (SCBs), and half use BRBs as lateral resisting systems. In addition, three irregularities are considered: geometrical irregularity in height and plan and nonorthogonal (nonparallel) systems. Nonlinear IDA is performed using twenty earthquake records to construct the fragility curves. Finally, valuable results are presented to clarify the effectiveness of BRBs in different heights, irregularities, and systems.

buckling restrained braces, seismic performance, irregularity, ۳D structures, fragility curve