Fatigue Reliability Analysis of Offshore Wind Turbines Under Combined Wind-Wave Excitation via DPIM

As offshore wind turbines develop into deepwater operations, accurately quantifying the impact of stochastic excitation in complex sea environments on offshore wind turbines and conducting structural fatigue reliability analysis has become challenging. In this paper, based on long-term wind-wave reanalysis data from a site in the South China Sea, a novel direct probability integral method (DPIM) is developed for the stochastic response and fatigue reliability analysis of the key components for the floating offshore wind turbine structures under combined wind-wave excitation. A 5MW floating offshore wind turbine is considered as the research object, and a fully coupled dynamic response analysis of the wind turbine system is conducted to calculate the short-term fatigue damage value of tower base and blade root. The DPIM is applied to calculate the fatigue reliability of the wind turbine structure. The accuracy and efficiency of the proposed method are validated by comparing the obtained results with those of Monte Carlo simulations. Furthermore, the results indicate that the fatigue life of floating offshore wind turbine structures under combined wind-wave excitation meets the design requirements. Notably, the fatigue reliability of the wind turbine under aligned wind-wave conditions is lower compared to misaligned wind-wave conditions.