Seismic response sensitivity and optimal design of an isolated multi-span continuous highway bridge with self-centering SMA RC bridge piers and superelastic SMA restrainers

The use of superelastic shape memory alloy (SMA) in reinforced concrete (RC) pier and restrainers between girder and pier/abutment has been proposed in an earlier study to improve the seismic performance of highway bridges. This paper aims at identifying the significant factors that affect the seismic response of such a novel bridge system. A sequential fractional factorial design method is performed to statistically evaluate the effects of six design factors (three geometry-related and three material-related) as well as their interactions. Additionally, a multi-criteria optimization technique is implemented to determine the most efficient combination of the design parameters for SMA RC piers and SMA restrainers. Results demonstrate that the geometry-related factors and their interactions have large effects (with a contribution greater than 91%) on the relative displacement between the girder and pier. The target residual drift of the pier, design target displacement of the restrainer, and their interaction are the three most significant factors (with contributions approximately 30%-68%) affecting the base shear of the pier. The residual drift of the pier is sensitive to the design target displacement of the restrainer, its interaction with the forward transformation stress of SMA, and material-related factors with regard to the energy dissipation of SMA.