Wave dissipation effect of a new combined breakwater and its protective performance for coastal box girder bridges

Breakwaters play an important role in in mitigating wave-induced damage to marine structures. However, conventional submerged breakwaters often exhibit limited wave dissipation capabilities, while floating breakwaters may lack adequate safety performance. Therefore, this study introduces a novel combined breakwater design aimed at addressing the shortcomings of both traditional types. The proposed breakwater integrates a floating structure with a trapezoidal submerged breakwater via an anchor chain connection. To evaluate its efficacy, numerical simulations of wave interactions with structures were conducted using the OpenFOAM computational fluid dynamics (CFD) software in a two-dimensional (2D) numerical flume. Dynamic mesh technology was employed to simulate the motion of the floating body, and the resulting wave loads on a box girder bridge deck positioned behind the breakwater were analyzed to assess the combined breakwater's protective capabilities and influencing factors. Analysis of wave heights and loads on the bridge deck revealed that the combined breakwater outperformed traditional submerged breakwaters in terms of wave dissipation. Furthermore, it was observed that the protective efficacy of the combined breakwater was more sensitive to variations in the size of the floating body compared to the submerged structure, and more responsive to changes in wave period than wave height. Leveraging the ability of the floating body to attenuate waves near the surface and the enhanced impact resistance provided by the combined floating and submerged structures, the proposed breakwater offers a promising approach to improving wave attenuation performance and enhancing safety for coastal infrastructure.