Seismic retrofit of simply supported bridges using shape memory alloys

Recent earthquakes in the United States and Japan have highlighted the vulnerability of bridges to collapse due to excessive movement at the intermediate hinges and abutments. This study investigates the effectiveness of shape memory alloy restrainer bars to reduce the seismic vulnerability of bridges. Full-scale tests of shape memory alloy (SMA) restrainer bars are conducted to determine their force-deformation and energy dissipation characteristics. The 25.4 mm diameter bars are subjected to cyclical strains up to 8%, with minimum residual deformation. The effectiveness of the SMA restrainer bars in bridges is assessed through nonlinear analyses of a typical multi-span simply supported bridge. The SMA restrainer bars are effective in limiting the relative displacement at the piers and abutments. In addition, the bars are shown to be very effective for near-field ground motion.