Effect of constitutive models on the seismic response of an SMA-LRB isolated highway bridge

Shape memory alloy wire-based lead rubber bearings (SMA-LRBs) are new types of smart isolators. They possess superior self-centering property with unique hysteresis and energy dissipation capacity compared to traditional elastomeric isolators. Although the hysteresis behavior of such elastomer can be approximated by bilinear kinematic hardening rule, the results become erroneous. Hence, a new constitutive model was developed for simulating the behavior of such smart bearings. Here, the developed model has been implemented in OpenSees, a finite element software. In order to verify the accuracy of this implemented model, the seismic behavior of a three-span continuous highway bridge isolated by SMA-LRBs is evaluated under different earthquake excitations. Results revealed that unlike the bilinear kinematic hardening model, the new model can precisely capture the self-centering property of SMA-LRBs. Findings show that SMA wires can satisfactorily reduce the shear strain demand in LRBs and restrain the deck displacement by increasing the effective stiffness of elastomeric isolator. As a result, the possibility of failure in the bearings, and unseating problem in the bridge deck can be effectively reduced. Results also show that due to the superior energy dissipation capacity of SMA-LRBs, such smart bearings can considerably improve the seismic performance of piers in terms of base shear.