Effects of floating breakwater on hydrodynamic load of low-lying bridge deck under impact of cnoidal wave

Abstract

Extreme ocean surface waves generated during hurricanes or tsunamis can cause severe damage to coastal communities and infrastructures, especially coastal bridges. In this paper, installation of floating breakwater is proposed to protect coastal bridge decks against strong ocean surface waves. As an environmental-friendly wave-reduction device, floating breakwaters can be easily installed and removed before and after a storm, avoiding impacts on navigation and other coastal operations. To numerically investigate effects of a floating breakwater on the applied hydrodynamic load of a bridge deck under the impact of cnoidal waves, a high-resolution numerical wave tank (NWT) is established using the open-source flow solver REEF3D, which solves the governing equations of the incompressible two-phase flow on a staggered mesh and captures the interface between air and water using a high-resolution level-set method. Effects of prominent parameters, i.e. wave height, water depth, submersion depth, spacing distance and aspect ratio of breakwaters, on the performance of floating breakwater and reducing the hydrodynamic load on a coastal bridge deck are systematically analyzed. It is found that hydrodynamic loads of coastal bridge deck can be greatly reduced through the use of floating breakwaters. Results of this paper can further enhance our understanding on the damage mechanism of coastal bridges under extreme surge waves, and should be instructive for future bridge design.