For offshore wind turbines (OWT), the fatigue loads are strongly dependent on the action of wave and wind on the tower base. The effective calculating methods for fatigue loads on the OWT's monopile foundation are developed in this paper. The fatigue wave load on the support structure is predicted using the spectra analysis method. Linear irregular wave models do not adequately represent waves in shallow waters where OWT's monopile is commonly sited. Our study investigates the use of irregular nonlinear waves for estimating loads on an offshore wind turbine. The nonlinear wave force spectrum and fatigue stress spectrum are achieved using the autocorrelation function and the Fourier transform. The fluctuating wind load acted on the rotor is analyzed based on the BEM (blade element momentum) theory. We use a 1.5MW wind turbine model for the simulations; calculate respectively fatigue loads of wind and wave. It has been show that wave effect dominates in fatigue loads and the fatigue damage under combined wave and wind loads isn't equal to the simple summation of the damage caused by the two sources of loading. The adapted load combination of wind and wave for the fatigue design of the OWT's monopile foundation is provided.

This content is only available via PDF.
You can access this article if you purchase or spend a download.