Scour-induced degradation of soil–structure interactions (SSIs) may substantially amplify the dynamic response of monopile offshore wind turbines (OWTs) under combined environmental and seismic loads. To clarify this mechanism and provide guidance for the safety assessment of OWT foundations, this study establishes a coupled numerical model considering wind, wave, earthquake, scour, and SSI effects. Based on this model, the DTU 10 MW OWT is selected as the research object, and its dynamic responses are investigated with different scour morphologies, scour depths, earthquake inputs, and selected soil parameter sets. The results show that scour reduces the lateral stiffness of the soil–structure system, shifts the structural natural frequency toward a lower-frequency range, and amplifies the displacement, acceleration, and stress responses under seismic excitation. With the selected M8 earthquake input, the tower top displacement reaches 4.18 m in the global-2D scour case, which is more than twice that in the non-scoured case. Global scour produces stronger response amplification than local scour because it weakens the SSI constraint around the full circumference of the pile. For the selected soil parameter sets and the adopted p–y formulations, the clayey foundation model produces smaller calculated displacement and stress responses than the sandy foundation model, reflecting differences in the prescribed lateral stiffness and ultimate soil resistance. These results provide comparative insights for the seismic assessment and scour-resistant design of monopile OWT foundations.

Owing to transportation, installation, grid-connection, and maintenance requirements, nearshore offshore wind farms are often located close to busy shipping routes, substantially increasing the risk of ship–offshore wind turbine (OWT) collisions. To enhance the impact resilience of OWT support structures against ship collisions, a novel honeycomb sandwich fender is proposed for tower protection. Nonlinear transient analyses were performed using ANSYS/LS-DYNA to simulate a 5000 t ship traveling at 2 m/s and colliding with a 4 MW OWT supported by a single-column tripod foundation. The effects of rubber and aluminum foam cores on the crashworthiness and protective performance of the fender were compared. The results show that the rubber core stores collision energy through recoverable large deformation and releases most of the stored energy during unloading, resulting in pronounced energy restitution and prolonged structural excitation. By contrast, the aluminum foam core dissipates 7.5 MJ through cell-wall buckling, progressive crushing, and plastic collapse, corresponding to 75% of the initial kinetic energy of the ship. Compared with the rubber-core fender, the higher initial stiffness of the aluminum foam increases the peak contact force by 23.1%, from 13.0 to 16.0 MN. However, its irreversible energy-dissipation mechanism reduces the maximum tower-top displacement by 40.0%, from 1.25 to 0.75 m, and decreases the residual tower stress after three successive collisions by 25.0%, from 200 to 150 MPa. These results demonstrate that, despite transmitting a higher peak contact force, the aluminum foam fender provides more effective overall protection under the collision conditions considered because of its greater irreversible energy-dissipation capacity.