An innovative base isolation system with Ni–Ti alloy and its application in seismic vibration control of Izadkhast Bridge

In this article, an innovative base isolation system based on steel–polytetrafluoroethylene sliding bearings equipped with shape memory alloy is proposed. This isolation system employs superelastic Ni–Ti alloy cables as recentering components and dissipates input energy through the friction and additional damping of shape memory alloy. As a case study, Izadkhast Bridge, the longest railway bridge in Iran, is considered and fitted with the proposed system. A three-dimensional nonlinear finite element model of the bridge is developed and time history analyses for various earthquake records are conducted. The results demonstrate that the proposed isolation system can effectively improve the bridge response quantities. Moreover, equipping the sliding bearings with shape memory alloy efficiently reduces permanent deck displacement of the base-isolated bridge. This study reveals that shape memory alloy cables mostly work as recentering elements with regard to the minimal damping capacity of shape memory alloy cables. In addition, sensitivity analyses on environmental temperature reveals that mechanical behavior of shape memory alloy on minimum probable temperature should be considered in design procedure. Regarding the financial and functional aspects, using minimum cross-sectional area and length of shape memory alloy cables is appropriate. Moreover, the geometric characteristics of shape memory alloy cables should be selected, so that shape memory alloy strain is being limited to the recoverable range (up to 8%).