Effect of ambient temperature on the hinge opening in bridges with shape memory alloy seismic restrainers

The superelastic behavior exhibited by shape memory alloys (SMAs) at temperatures above the austenite finish temperature could be directed towards many structural seismic applications. However, this superelasticity characteristic of shape memory alloys is highly dependent on ambient temperature. This would be of a major concern in the case of structures which are directly subjected to the surrounding environment such as bridges and coastal structures. This paper evaluates the effect of variability in the ambient temperature on the performance of SMAs as potential seismic restrainers for bridges. A sensitivity study is conducted using a 2-DOF bridge model and a thermomechanical SMA model subjected to a suite of ground motion records. The results of the study are validated using a case study where a 6-frame MDOF bridge model is used. The results of both studies show that SMA restrainers are more effective in limiting the hinge opening at higher ambient temperatures. The effect of temperature changes on the hinge opening is more pronounced at temperatures near the austenite finish temperature and in the case of bridges with large ductility and/or moderate-to-high period ratio.