Earthquake Resilient Design of Highway Bridges with Tall Piers

With rapid development of the western region in China, a large number of highway and railway bridges with tall piers will be built in the mountainous areas of Western China with high seismicity and high seismic intensity. To improve the seismic performances of the bridges with very tall piers, two kinds of innovative earthquake-resilient tall pier systems are proposed, including four-limb RC column (FLRCC) - buckling restrained brace (BRB) composite pier and concrete-filled steel tubular column (CFSTC) - energy dissipating mild steel plate (EDMSP) composite pier, based on the concept of earthquake resilient structures. Trail designs of highway bridges with the proposed earthquake-resilient tall pier systems were carried out based on a typical continuous rigid frame highway bridge with very tall piers. The finite element models of the bridges with conventional RC piers (including hollow section and spatial frame piers), and with innovative composite piers (including FLRCC-BRB and CFSTC-EDMSP composite piers) were built by OpenSees software and ABAQUS software, respectively. Nonlinear time-history analyses of the bridge models were performed under E2 level earthquake ground motions according to the Chinese Guidelines for Seismic Design of Highway Bridge, and the seismic performances of the bridges with different tall piers were compared and discussed. The results show that: (1) Both the bridges with conventional RC piers experience medium damage in the piers under E2 level seismic action; (2) Both the bridges with FLRCC-BRB composite piers and with CFSTC-EDMSP composite piers nearly remain elastic under E2 level seismic action, while only the EDMSP or BRB elements undergo plastic deformations, indicating that both the bridge structures are earthquake-resilient; (3) Compared to the bridges with conventional RC piers, the bridge with FLRCC-BRB composite piers or with CFSTC-EDMSP composite piers has much better energy dissipation capacity, and the seismic lateral displacement demands are also much smaller, under a strong earthquake ground motion.