CFD investigation of the cap effects on wave loads on piles for the pile-cap foundation

Abstract The cap effects on the wave forces acting on the piles underneath the cap are important for the estimation of the wave loads on the elevated pile-cap foundations of sea-crossing bridges. Full scale 3-dimensional numerical simulations are carried out for large square caps with piles placed at different locations underneath. The influences of wave height, wave length, cap dimension and submerged depth on the cap effects are investigated. The analytical method is introduced and its solutions are compared with the numerical simulation results. The results show that the wave forces on piles are influenced by the free surface runup and rundown in front of the cap, and the negative force on the pile near the front edge of the cap can be remarkably larger than the positive force with large wave height. The cap coefficient K c a p decreases with the increase of the relative cap dimension. The cap shows force-increasing effect on piles when the relative cap dimension is smaller, i.e. K c a p > 1 , which should be highly concerned in the sea-crossing bridge design.