Seismic Response Mechanism and Soil–Structure Interaction of Monopile Offshore Wind Turbines Under Flat and Near‐Sloping Seabed Scenarios

Monopile foundations are widely used in fixed‐bottom offshore wind turbines (OWTs), and their seismic response is strongly affected by pile–soil–structure interaction. Most existing studies have focused on OWTs located on flat and idealized seabeds, whereas the influence of near‐slope seabed topography has received relatively limited experimental attention. To address this gap, this study conducts small‐scale shake table tests on a monopile‐supported OWT model embedded in sand under no‐slope and near‐slope conditions. The effects of turbine orientation angle, toward‐slope and away‐slope orientations, and the distance from the pile to the slope crest are examined using structural acceleration, soil acceleration, acceleration amplification factors, and pile‐head displacement. The results show that, under no‐slope conditions, the pile‐head and tower‐top accelerations increase with the turbine orientation angle, while the soil acceleration is less sensitive to turbine eccentricity. Under near‐slope conditions, the measured soil accelerations are approximately 5%–10% higher under the toward‐slope orientation than under the away‐slope orientation. A shorter distance from the pile to the slope crest generally corresponds to a higher soil acceleration response within the tested range. Compared to previous studies based mainly on flat seabed assumptions or numerical models, this study provides controlled physical model evidence for understanding the seismic response of monopile‐supported OWTs near sloping seabeds. The findings provide preliminary experimental support for considering seabed topography effects in the seismic assessment of fixed‐bottom OWTs.