An integrated model for long-term dynamic performance of monopile-supported wind turbines under operational loads with consideration of soil-structure interaction and soil property evolution

During the long-term operation of monopile-supported wind turbines (MWTs), operation loads such as wind, 1P, and 3P loads gradually alter the mechanical properties of surrounding soil, which in turn modifies the turbine's dynamic performance and potentially compromise its safe operation. To address this issue, this study proposed a novel and integrated framework for modelling the long-term dynamic performance of MWTs. The wind turbine is modeled using Euler-Bernoulli beam theory with Rayleigh damping, while aerodynamic loads are computed through blade element momentum (BEM) theory. A bounding surface p-y model considering ratcheting effects is proposed to capture the hysteretic response of soils. Structural stiffness, damping, and aerodynamic loads are iteratively updated to obtain the system response. The framework is validated against monopile cyclic loading tests (Chiou et al., 2018), MWT cyclic loading tests, and MWT long-term dynamic performance wind tunnel tests. Comparison between the predicted and experimental results shows that the model achieves an average error of 12 % for displacement and rotation. The errors in key dynamic characteristics including natural frequency and damping ratio remain within 10 %. These results demonstrate that the model can accurately capture the long-term dynamic response of MWTs, providing an effective method for assessing their long-term operational safety.