Wave load is one of the main environmental loads on the foundation of sea-crossing bridges. In order to investigate the difference between various wave load calculation methods on large-scale bridge foundations, the Morison equation, the code, the three-dimensional diffraction theory based on the boundary element method and the CFD method based on the Navier Stokes equation are used to calculate the wave load on a large-scale round ended caisson foundation of a sea-crossing bridge, respectively. The influence of the relative scale of the structure on the results of each method is studied. The distribution of three-dimensional flow field and pressure field of the latter two numerical methods is compared in detail and the influence of the nonlinear second-order force effect is focused on. It is found that when the relative scale of the structure is about 0.2, the results of the above method are similar. With the increase of the relative scale, the boundary element method is still in good agreement with the CFD method, while the code gives a more conservative wave load, and the Morison equation may overestimate the contribution of the wave drag force. The results of flow the field and pressure field obtained by the boundary element method and CFD method are consistent in trend, but there are obvious differences in local areas such as free surface and object surface at the front of the open caisson and wave trough at the side of the open caisson, which may be due to the difference between the two theories that consider the diffraction effect and the viscosity effect, respectively. The second-order force effect will increase the wave load slightly and add the difference frequency and sum frequency components into the frequency spectrum. After considering the nonlinear second-order force effect, the frequency spectrum curve of the boundary element method is more consistent with that of the CFD method, and the boundary element method can calculate the wave load more accurately. Both the boundary element method and CFD method can reasonably give the wave load results of large-scale structures. The results provide a basis for the accurate calculation of wave load on sea-crossing bridge engineering.
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