Influence of Thermomechanical Coupling Effects of Superelastic Shape Memory Alloy Cables on the Seismic Performance of Bridges

Abstract Current constitutive models of shape memory alloys (SMAs) used in structural seismic design are predominantly derived from quasi-static experimental tests. However, as a thermomechanically responsive material, the stress–strain behavior of SMAs exhibits significant temperature dependence. During seismic events, SMAs experience rapid dynamic loading conditions, resulting in substantial deviations between their actual in-service stress–strain response and the predictions based on conventional experimental analysis. This study investigates the thermomechanical behavior of SMA cables through differential scanning calorimetry (DSC) to determine their phase transformation temperatures and employs an MTS universal testing machine to characterize their stress–strain relationships under varying loading frequencies. By incorporating theoretical analysis based on martensite fraction evolution, the research establishes the phase transformation stresses corresponding to different loading frequencies. Finally, a comprehensive case study was conducted on a typical bridge structure to assess the impact of thermomechanical effects during seismic events. The analysis revealed that neglecting these thermomechanical considerations leads to significant underestimation of forces in substructures, potentially compromising the structural safety and integrity of bridge systems.