Numerical investigation of wave force on two closely spaced bridges subjected to stokes wave

In recent years, coastal transportation infrastructure has entered a phase of rapid development. However, frequent extreme storm surges and tsunami waves pose significant threats to the structural safety of coastal bridges. This study investigates wave force acting on two closely spaced box-girder bridge decks under second-order Stokes wave conditions. A two-dimensional numerical wave flume was developed using Computational Fluid Dynamics (CFD) methods, incorporating second-order Stokes wave theory for wave generation. The model’s accuracy was validated through comparison with experimental results. Key findings include: (1) Significant differences in wave-induced force are observed between two closely spaced box-girder bridges and solo deck configurations, mainly due to wave reflection and flow entrapment between decks; (2) Hydrodynamic parameters such as submergence coefficient, wave height, deck spacing, and wave period exhibit differing effects on the wave-ward and leeward bridge decks; (3) After full submergence and with higher wave heights, the peak counteracting horizontal force (the force acting opposite to the wave propagation direction) is more likely to surpass the peak forward force; (4) Inclined web configurations are effective in reducing horizontal wave impacts compared to vertical webs, though they induce greater vertical loads. These insights provide a theoretical reference for the hydrodynamic design and safety evaluation of coastal bridges under extreme wave conditions. In particular, the distinct differences in wave force responses between two closely spaced and solo box-girder configurations deserve further engineering attention in marine bridge applications.