Comparative seismic fragility assessment of mid-rise steel buildings with non-buckling (BRB and SMA) braced frames and self-centering energy-absorbing dual rocking core system

Abstract

During the past two decades, many emerging smart lateral force-resisting systems have been proposed for achieving better post-earthquake recoverability than the conventional ones in steel buildings. The Self-centering Energy-absorbing Dual Rocking Core (SEDRC) system has been developed recently by the authors for achieving excellent self-centering behavior with large deformability in steel buildings. This paper intends to investigate the benefit of steel buildings using the SEDRC system compared to that using other emerging smart lateral force-resisting system (e.g., shape memory alloy braced frame (SMABF)) and conventional one (e.g., buckling restrained braced frame (BRBF)). For this purpose, first, three six-story steel buildings with BRBFs, SMABFs, and SEDRC systems, were designed to obtain similar inter-story drifts subjected to the design basis earthquakes. Second, nonlinear static and dynamic analyses were conducted to preliminarily study the seismic performance of the designed buildings. Then, incremental dynamic analyses (IDAs) with far-field and near-fault ground motion inputs were conducted to study the seismic responses of the designed buildings under different seismic hazard levels. Finally, the results from the IDAs were analyzed in a probability framework. The inter-story drifts, residual inter-story drifts, and floor acceleration responses of the considered systems were analyzed to investigate the seismic fragility of the structural and nonstructural components in the designed buildings. The analysis results indicate that the SEDRC system can achieve the best structural collapse-resistant capacity under both far-field and near-fault ground motions because of the excellent deformability. The SMABF and SEDRC system show better seismic resilience performance by controlling the residual inter-story drift responses than BRBF. Moreover, the SEDRC system can obtain a smaller exceedance probability of damage states associated with nonstructural components depending on floor acceleration responses than SMABF because of uniform inter-story drift responses.