Estimation of Wave Force Acting on Bridge Superstructures due to the 2011 Tohoku Tsunami

Wave forces acting on the superstructures of two highway bridges affected by the 2011 Tohoku tsunami, the Shin-Aikawa Bridge and the Yanoura Bridge, are estimated combining 2-D FDM and a numerical wave flume (CADMAS-SURF) analysis. The superstructure of the Shin-Aikawa Bridge was washed out and swept 500 m away by the backwash. The Yanoura Bridge suffered no damage even though it was completely submerged in the tsunami. Time histories of the tsunami wave height and flow velocity are calculated using 2-D FDM, based on the nonlinear long wave theory. Lateral and uplift forces acting on the superstructures due to the simulated tsunami are then analyzed by the numerical wave flume. Comparisons between the analytical wave forces and corresponding loading capacities account for the differences in damage to the two bridges.