Support condition identification for monopile-supported offshore wind turbines based on time domain model updating

The soil-structure interaction (SSI), which presents intricate nonlinearities and inevitably varies throughout the structural lifetime, is critical for the structural performance of monopile-supported offshore wind turbines (OWTs). Since its direct monitoring is challenging, a new time domain model updating method for support condition identification of monopile-supported OWTs is proposed in this study. A distributed spring-dashpot model incorporating nonlinear stiffness and damping is used to simulate the SSI. Time-domain responses of the OWT are used to construct the objective function for model updating. Vibration tests on a scaled model of the DTU 10 MW OWT are performed in the laboratory to verify the proposed method. The model updating results based on the test data show that the mean squared error between simulated and measured responses is less than 0.011, significantly smaller than the results obtained by using the traditional frequency-domain model updating methods. These findings demonstrated that the proposed distributed spring-dashpot model can accurately capture the complex nonlinearity in SSI and that the proposed time-domain model updating method can be used to identify the support conditions of monopile-supported OWTs. The methodology is expected to contribute significantly to enhancing the efficiency of the operation and maintanence for OWTs.