Dynamic reliability assessment of floating offshore wind turbine drivetrains considering various levels of stress

Floating offshore wind turbines (FOWTs), designed to exploit wind resources in deep-water environments, have attracted considerable attention due to their substantial development potential. This study investigates the operational reliability of a floating offshore wind turbine drivetrain (FOWTD) subjected to multiple stress levels throughout its service life. The structural configuration and power transmission mechanism of FOWTs are first analyzed, and based on this analysis, a fully coupled dynamic model and a dynamic reliability model under varying stress conditions are developed. The fatigue strength and gear reliability of the FOWTD under stochastic wind conditions are systematically evaluated, and the evolution trends of the dynamic failure rate and time-dependent reliability are examined. Experimental validation demonstrates that the proposed dynamic reliability model exhibits high accuracy and applicability. The maximum absolute error over the entire life cycle does not exceed 3.1%, and the relative error at the 25-year operational stage remains below 5%, satisfying engineering accuracy requirements. The findings of this study provide valuable insights into the reliability evolution of FOWTDs under realistic multi-stress operating conditions.