Fatigue analysis of monopile-supported offshore wind turbine under varied supported conditions

The fatigue life of a monopile-supported offshore wind turbine (OWT) is substantially influenced by the support conditions which inevitably changes during its service life. This study performed fatigue analyses of monopilesupported OWTs with varied support conditions, which not only determine the correlation between the support condition and the fatigue damage of OWT, but also predict fatigue lifetime of OWT for different support condition scenarios. A simplified finite element model of a 10 MW OWT is constructed. Long-term wind and wave data, measured over 25 years in the South China Sea, are utilized to determine the fatigue loads. The results show that the fatigue damage incurred in the parked status of the OWT is negligible, accounting for 0.84% of the total fatigue damage. Both support stiffness and damping have significant effects on the fatigue damage of OWT, both exhibiting a strictly negative correlation with the fatigue damage of OWTs. When stiffness and damping decrease at high rates, the total fatigue damage of the structure exceeds 100%, indicating that fatigue damage may occur in the OWT structure during its life cycle. This study provides a reference for fatigue design and may contribute to the assessment of fatigue damage in OWT.