Seismic Damage Assessment of SMA-Retrofitted Multiple-Frame Bridge Subjected to Strong Main Shock–Aftershock Excitations

Abstract

This study numerically examined the seismic performance of a multiple-frame bridge retrofitted with external shape memory alloy (SMA) spirals actively confining the plastic hinges of the bridge piers when subjected to strong main shock–aftershock sequences. A numerical model of the bridge, including abutments and expansion joints, was developed and used in the study. The model accounts for the spread of plasticity along the piers and the constitutive behavior of SMA-confined concrete. A suite of main shock–aftershock records with various characteristics was used in a series of nonlinear dynamic analyses performed on the as-built and retrofitted bridge using different levels of SMA confinement. The seismic performance of the bridge was assessed by monitoring damage states at the local and global levels. The results show that active confinement provided by SMA spirals is quite effective in preventing concrete crushing under strong sequential seismic events and that strength degradation in concrete greatly reduces as the level of confinement increases. SMA confinement can also contribute to reducing fatigue damage in reinforcing bars and residual hinge openings at the bridge joints.