Effect of Scour on Hydrodynamic Pressure of Offshore Monopile and Site Response Under Seismic Loads

In complex marine environments, monopile foundations are subjected not only to waves and currents but also to seismic loads. The long-term combined action of waves and currents induces scour around the monopile, leading to soil loss, seabed morphology changes, and an enlarged water–structure interface. When seismic load is present, scour amplifies the hydrodynamic pressure on offshore monopiles and modifies the site response, significantly influencing the seismic performance of the monopiles and their superstructures. To address the issue, this study develops three-dimensional numerical models based on the computational fluid dynamics (CFD) method and ABAQUS (2020) to systematically investigate the effects of scour on hydrodynamic pressure of offshore monopile and site dynamic response under seismic loads. First, a numerical model including scour effects is established in ANSYS Fluent (2022), and parametric analyses are performed to evaluate the impact of local scour hole geometry on hydrodynamic pressure; subsequently, comparisons are made with global scour conditions, and an added mass coefficient accounting for the distribution of scour effects along the pile is proposed. Finally, on the ABAQUS platform, a numerical model is developed to analyze the dynamic response of the free-field soil and the coupled water–soil free-field under scour conditions.