Seismic Performance Upgrade of Double-Column Multistory Pier Bents by Integrating Sequentially Sacrificial Shear Dampers and Buckling-Restrained Braces

Reinforced concrete (RC) double-column multistory pier bents in mountainous highway bridges often employ multiple link beams to enhance lateral stiffness, but this design can amplify seismic demands and cause severe beam–column joint damage. This study proposes a seismic-resisting system that integrates shear dampers (SDs) within link beams and buckling-restrained braces (BRBs) between columns. Acting as sequentially sacrificial components, SDs and BRBs dissipate energy and fail in a controlled manner, thereby protecting columns and link beams while enhancing deformation capacity of the whole pier bents. Following an overview of the proposed system, three systems are utilized to unveil the mechanisms and validate the effectiveness, including a typical double-column pier bent in engineering practice as the prototype, the prototype without link beams used for comparison, and the prototype retrofitted with the proposed resisting system. Nonlinear pushover and incremental dynamic analyses show that the proposed system prevents premature failure of link beams and reduces the lateral displacement demands of columns under strong earthquakes without imposing additional base reaction. Additionally, the ultimate displacement capacity of the pier bent is increased by 43%, which substantially improves the seismic performance and reliability accompanied with the reduction in demands. Furthermore, results of fragility analysis confirm the lowest seismic vulnerability of the proposed system in probabilistic perspective, reducing the likelihood of suffering extensive damage at the design earthquake of the prototype with and without link beams from 33% and 26%, respectively, to 10% in the proposed system. The findings highlight the effectiveness of the proposed system as a potential seismic resilient design strategy for RC pier bents.