Wave forces on box-girder-type bridge deck located behind trench or breakwater

Wave forces severely damage low-lying coastal bridges during hurricanes. In this study, a model for analyzing hydrodynamic wave forces acting on a bridge superstructure with a box girder behind a trench or breakwater was developed. First, the boundary value problem was defined based on necessary assumptions and simplifications. Next, an analytical solution of wave forces on the bridge superstructure was obtained using the potential flow theory and the eigenfunction-matching method. The validity and convergence of the analytical model were verified against the results of an experimental hydrodynamic study and a limiting case. With the proposed method, the effects of the trench and breakwater on the wave loads were investigated. Finally, a parametric analysis was conducted to reveal the hydrodynamic characteristics that influenced the wave–bridge interaction. The parametric study shows that both the trench and breakwater are useful in mitigating wave forces. A specialized design of the wave–structure system configuration is required to reduce the wave forces acting on bridge decks effectively.