Use of Shape Memory Alloys with Laminated Rubber Bearings in Seismic Isolation of Multi-Span Continuous Moderate to Strong Seismic Zones

This study is devoted towards evaluating seismic performance of a three-span continuous highway bridge subjected to moderate to strong earthquake ground motions in its longitudinal direction. In this regard, nonlinear dynamic analysis of the bridge based on the direct time integration approach using the 4 order Runge-Kutta method is conducted. Two types of isolation bearings are used in the analysis: high damping rubber bearing (HDRB) and SMA-rubber bearing (SRB) consisting of Ni-Ti SMA wires and natural rubber bearing. The hysteretic behavior of HDRB is evaluated using the strain-rate dependent rheology model (i.e. visco-elasto-plastic model), while for the SRBs the hysteretic behavior is modeled by the nonlinear elasto-plastic model. The nonlinear force-displacement relation for the bridge pier as characterized by the bilinear model is employed in the analytical model of the bridge. Finally, the variation in seismic responses of the bridge due to the use of HDRB and SRBs is investigated. The bridge response quantities evaluated in the investigation include peak values of deck displacement, pier top displacements, and deck acceleration. The comparison shows that the seismic responses of the bridge are affected by the use of different isolation systems; more specifically the displacements of the bridge pier are noticeably reduced in the case of SRBs compared to those in the case of HDRBs.