Seismic resilience-based assessment and design of concrete bridge piers reinforced with shape memory alloy bars

Abstract

Using the shape memory alloy (SMA) bar to reinforce a bridge pier is considered a viable solution for improving its seismic resilience. Up to now, engineering and academic communities still lack knowledge on designing bridge piers from a seismic resilience-based perspective with quantifiable and controllable earthquake-induced disturbance. This study proposes and implements a resilience-based seismic design method for concrete bridge piers or columns reinforced with SMA bars to address this issue. Such a methodology utilizes an equivalent downtime to quantify seismic resilience and incorporates an authentic and quantifiable bridge post-earthquake recovery process into the pre-disaster evaluation and design processes. After that, this methodology is implemented through a benchmark bridge pier. A numerical model of the pier, reinforced with varying SMA replacement ratios in its plastic region, is generated considering the longitudinal rebars’ bond slip and material-related parameter uncertainty. Site-specific ground motion records are chosen based on a uniform hazard spectrum for seismic excitations. The seismic fragility and resilience surfaces of the bridge pier are generated (using residual and peak drift ratios as dual damage indicators) to reveal the influence of the SMA replacement ratio. Finally, an optimal SMA replacement ratio is ascertained based on seismic resilience objectives. The result indicates that partially rather than fully replacing the ordinary longitudinal rebars using SMA bars in the plastic hinge region of concrete bridge piers is adequate to satisfy seismic resilience requirements, achieving a balance between the bridge’s seismic resilience and its initial construction costs.