Numerical investigation of breaking wave impact on coastal bridge superstructures with box girder

Coastal bridges are pivotal components of coastal transportation networks, yet their structural integrity is increasingly threatened by extreme wave events. To address this concern, the present study develops a numerical model using open-source computational fluid dynamics (CFD) software OpenFOAM. This model employs the constant steepness wave focusing method to generate breaking waves, with predictive accuracy validated through quantitative comparisons with experimental data from physical flume tests. A systematic parametric investigation elucidates the effects of three key factors on breaking wave forces acting on box girder bridge superstructures: the relative distance between the box girder and wave breaking point, global wave steepness, and bridge clearance. Results show that extreme breaking wave force is predominantly attributed to slamming force, with magnitude reaching peak when the bridge is positioned near the breaking point. With increasing global wave steepness, breaking wave force exhibits an overall increasing trend, and abrupt variation in force coincides with transitions in breaking wave types (e.g., from spilling to plunging waves). Breaking wave force decreases as bridge clearance increases. The research outcomes provide valuable insights and a robust technical basis for disaster prevention and mitigation design of coastal bridge engineering.