A spectral approach for efficient fatigue damage evaluation of floating support structure for offshore wind turbine taking account of aerodynamic coupling effects.

This paper addresses a spectral approach for evaluating the fatigue damage in a floating offshore wind turbine (FOWT) structure accurately by taking account of the nonlinear coupling effects between wind and wave loads. It is shown that the spectral moments under the combined loads can be estimated by a sum of those under wind-only cases and wave only-cases, however, with some corrections to account for the nonlinear coupling effects. A formula to estimate the variance of the stress under combined loads as a function of wind speed and wave height is developed based on a mechanical model. The formula is extended to even higher spectral moments. Then, the developed method is applied to the fatigue damage evaluation in a semi-submersible FOWT. The results from the developed method in terms of the fatigue damage are compared with those from the direct approach for validation. An efficient method for long-term fatigue damage evaluation of FOWT is envisaged based on the proposed method. [ABSTRACT FROM AUTHOR]