Computation of wave loads on the superstructures of coastal highway bridges

Recent hurricanes have caused severe structural damages to a number of coastal highway bridges along the US coast of the Gulf of Mexico. A large amount of bridge superstructure sections were displaced or pushed off the substructure by storm surge and wave action. To prevent such structural failure of coastal bridges, wave loads on bridge superstructures need to be quantified. In this study, two different numerical models were used to analyze wave-structure interaction and compute wave loads. Computational Fluid Dynamics (CFD) Software Flow-3D was used to analyze the effects of green water loading and superstructure elevation on wave forces. A 2D potential flow model was developed for computation of wave loads on bridge superstructures fully submerged in water. Wave induced pressure on bridge superstructures was obtained by solving complex velocity potential from Laplace's equation and boundary conditions using finite difference method. The 2D potential flow model was validated by large-scale laboratory measurements, and then used to perform parametric study using a range of wave parameters, water depth and bridge superstructure width. Equations for calculating wave loads on bridge superstructures were developed using results of the parametric study.