Seismic Design and Performance Evaluation of a Triple-Column Bent Bridge Retrofitted with Buckling-Restrained Shape Memory Alloy Dampers

In seismic prone regions, many old bridges deserve retrofitting measures to improve their seismic resilience. The recently proposed buckling-restrained shape memory alloy (SMA) dampers, which can maintain axial resistance under low temperatures, are potential candidates for outdoor applications. However, the corresponding design method and retrofitting efficacy remain unknown. Besides, the effects arising from temperature variations and device uncertainty have not been addressed. To this end, this work proposes a performance-based retrofitting method and conducts a probabilistic evaluation for bridges retrofitted with buckling-restrained SMA dampers. The temperature-specific behavior of the damper is first described, and then a triple-column bent bridge located in Salt Lake City is selected for demonstration purposes. To unveil the seismic retrofitting efficacy, nonlinear time history analysis and fragility analysis are performed. The considered uncertainties include temperature variation, device uncertainty, and seismic intensity. The results indicate that the bridges retrofitted by the designed damper could achieve prescribed performance targets. In addition, with the variations of temperature and device, the seismic response demands are relatively stable. The damage probabilities and seismic risk are reduced by the installed dampers. Hence, the buckling-restrained SMA dampers have a reliable seismic control efficacy for bridges.