Numerical study on mitigating tsunami force on bridges by an SPH model

This study applies the numerical model of GPUSPH, an implementation of the weakly compressible Smoothed Particle Hydrodynamics method on graphics processing units, to investigate tsunami forces on bridge superstructures and tsunami mitigation on bridges by using a service road bridge and an offshore breakwater. The capability of GPUSPH to predict tsunami forces on bridges is first validated by simulating a laboratory experiment on tsunami impacting a bridge with different configurations of superstructures. To address the uncertainty of tsunami generation with the gate falling method used in the laboratory, this study proposes a new tsunami wave generation method that makes use of the laboratory free-surface measurements to replicate the wave. Furthermore, the tsunami force, in particular, the first impact force, on bridges is reasonably predicted by GPUSPH. Next additional numerical experiments built upon the laboratory work are carried out to examine the efficiency of tsunami mitigation by an upwave service road bridge and an offshore breakwater. It is found that a two-girder service road bridge is effective in reducing tsunami forces on the main bridge. Furthermore, a breakwater can also reduce tsunami forces on a bridge, and there is an optimal distance between the breakwater and the bridge to achieve the best reduction effect. However, the tsunami mitigation structures experience a strong tsunami force, which may lead to the failure of these structures.