Performance evaluation of bridges isolated with SMA-based friction pendulum system at low temperatures

This study investigates the performance of bridges isolated with the SMA (shape memory alloy) -based FPB (pendulum friction bearing) system at low temperatures. The SMA-based FPB system with Cu-Al-Be alloy wires is performed in OpenSees. The nonlinear time history analyses are conducted under near-fault ground motions. The optimum amount of the Cu-Al-Be wires with respect to isolation period is obtained by the proposed method. The effectiveness of the SMA-based FPB system for bridges at low temperatures is further investigated. Results show that the residual displacement can be effectively reduced without significantly increasing the base forces at low temperatures. The maximum isolator displacement can be effectively reduced when temperature is higher than -10 degrees C, whereas the reduction is limited below -20 degrees C. The energy dissipation capability of the side bearings can be improved at 20 degrees C, whereas limited improvement for the energy dissipation of the bearings can be provided at low temperatures. This study demonstrates that the SMA-based FPB system with Cu-Al-Be wires at low temperatures can provide reliable re-centering capability for bridges under near-fault ground motions.