Experimental investigation on hysteretic performance improvement measures for self-centering pier system: NPR-BRB damper and UHPC with steel plate

Self-centering (SC) pier system has the advantages of self-recovery and low damage, which is an effective way to improve the seismic performance of bridge structures. However, major mechanical performance degradation is still observed in many hysteretic tests of SC pier specimens owing to the damage in the energy dissipation and contact segment components. Therefore, to markedly decrease the hysteretic performance degeneration of SC pier system, this study proposes and evaluates two innovative measures to strengthen these two components. In the energy dissipation component, a negative Poisson's ratio (NPR) steel bar is used as the core of the BucklingRestrained-Brace (BRB) damper to improve its ductility. In the contact segment component, the rocking interface is strengthened using ultra-high-performance concrete (UHPC) with steel plate to prevent the brittle failure. Firstly, the performance decline of SC pier system owing to the damage in the energy dissipation and contact segment components is analyzed in detail. Then, the proposed performance improvement measures are introduced through tests and mechanical analyses. Finally, a hysteretic test and finite element models of the SC pier system confirm the effectiveness and feasibility of the proposed strengthening measures for improving the hysteretic performance.