Three-dimensional soil–pile dynamic interaction analyses of monopile offshore energy turbi̇nes under the effects of earthquake, wind, and ocean

The dynamic analysis of offshore wind turbines requires careful consideration of various key design parameters, especially due to the complexity of their interaction with the marine environment. Among these, the monopile foundation—commonly used to support turbines—plays a crucial role not only in structural performance but also in terms of cost-efficiency. Designing such systems under the combined influence of seismic activity and time-dependent environmental loads demands a detailed understanding of nonlinear soil-structure interaction mechanisms. This study focuses on the behavior of monopile-supported offshore wind turbines constructed in complex soil conditions, taking into account three-dimensional geomorphological variations and deformations. Using finite element analysis, dynamic responses such as lateral displacements, rotational movements, and bending moment changes were evaluated under the combined effects of earthquakes, wind, and ocean waves. These responses, which are rarely encountered in standard structural systems, highlight the need for a more integrated design approach. Special attention was given to how seismic and environmental forces alter the acceleration and deformation behavior of the monopile system, with soil-pile interaction playing a central role. Simulation results were compared with those obtained through optimization techniques as part of the validation process. The nonlinear time-history responses under unilateral seismic excitation, combined with wind and wave loads, were used to investigate the dynamic behavior of the system. Findings indicate that the interaction between the monopile and surrounding soil is significantly affected by subsurface geomorphological variations. Therefore, incorporating three-dimensional deformation patterns derived from seismic field investigations into the analysis is essential for achieving realistic and reliable design outcomes.