Seismic vulnerability in tall steel structures: Conventional vs. buckling restrained braced frames

This paper presents a comparative analysis of the seismic performance of two tall steel buildings employing different dual systems: the Special Concentrically Braced Frame (SCBF) and the Buckling Restrained Braced Frame (BRBF). The study investigates the behavior of two 30-story structures subjected to ground motions from 15 far-field and 15 near-field earthquake records, using Incremental Dynamic Analysis (IDA). Additionally, fragility curves are developed to evaluate structural damage probabilities at Immediate Occupancy (IO) and Collapse Prevention (CP) performance levels. Seismic loss estimation is conducted using the FEMA P-58 methodology, providing a comprehensive assessment of economic implications at two intensity levels, corresponding to mean return periods of 475 and 2475 years. The outcomes emphasize the critical influence of near-field ground motions, which impose greater demands on structural performance compared to far-field scenarios. The results reveal that BRBF systems consistently outperform SCBFs in terms of economic efficiency and seismic resilience. At intensity level 1, median repair costs for SCBFs are 24.7% and 30.4% of the total replacement cost under far-field and near-field conditions, respectively, compared to 20.7% and 25.6% for BRBFs. These cost advantages persist at intensity level 2, where BRBF repair costs are 31.7% and 36.4%, significantly lower than the 33.9% and 42.5% for SCBFs. These findings confirm the superiority of Buckling Restrained Braced Frames in reducing repair costs, minimizing damage probabilities, and enhancing the seismic resilience of tall steel buildings, regardless of ground motion characteristics.