Influences of the pile-restrained floating breakwater on extreme wave forces of coastal bridge with box-girder superstructure under the action of two-dimensional focused waves

In the complex marine environment, coastal bridges are vulnerable to damage under extreme wave action, and researchers have focused on taking effective measures to reduce structural damage and extreme wave forces in recent years. In this study, a wave-structure coupling method was utilized to numerically investigate the focused wave forces on the two-dimensional coastal bridge with a box-girder superstructure under the influence of the pile-restrained floating breakwater. After a series of validations in the focused wave generation and wave-structure interactions, the effectiveness of floating breakwaters in protecting the box-girder superstructure from extreme wave damage and the influence of control parameters of floating breakwaters on extreme wave forces were conducted. The numerical results demonstrate that the focused wave forces on the box-girder su-perstructure are effectively reduced after the installation of the pile-restrained floating breakwater. Compared with the floating breakwater with linear stiffness, the maximum horizontal and vertical wave forces are reduced more significantly by the floating breakwater with the displacement constraint. According to the wave param -eters of the coastal bridge site, the appropriate size of the pile-restrained floating breakwater and the distance between the breakwater and the superstructure are suggested to improve the reduction effect of focused wave forces on the box-girder superstructure.