Risk-based design and optimization of shape memory alloy restrained sliding bearings for highway bridges under near-fault ground motions

Abstract

The Shape Memory Alloy (SMA)-restrained bearing consists of a typical sliding bearing and SMA wires. The SMA wires are adopted to limit the excessive displacement caused by near-fault ground motions, which can improve the re-centering capacity and energy dissipation capability of sliding bearings. Such bearings should be carefully designed to balance the pier force and bearing displacement so that the bridge system can achieve better performance. The present paper proposed a novel seismic risk-based methodology for the optimization design of SMA-restrained sliding bearings for highway bridges subjected to near-fault ground motions. First, the seismic risk of the bridge system was served as the performance index in this methodology. Second, identical component fragility curves were derived in order to minimize the seismic risk of the whole bridge system. Then, the Particle Swarm Optimization (PSO) approach was implemented to obtain the optimal mechanical properties of SMA-restrained sliding bearings that yield the same fragility curves. Finally, a simplified optimization design method was proposed for searching optimal designs, which can significantly reduce the computational effort but maintain the accuracy of optimal results. The proposed methodology was demonstrated by using a two-span highway bridge as a case study. It is shown that the proposed methodology can be adopted to obtain the optimal designs of the SMA-restrained sliding bearings for highway bridges, which can minimize the seismic risk of the whole bridge system under near-fault ground motions.