Long-Term Fatigue Damage Sensitivity to Wave Directionality in Extra Large Monopile Foundations

Abstract

The fatigue damage sensitivity to wave directionality on large-diameter monopile foundations for use in the offshore wind turbine industry is investigated. A frequency domain approach with the Dirlik method is used for a fatigue damage estimate and evaluate the effect of wave spreading and swell separation compared to a total sea representation. 30 years of hindcast data from the Dogger Bank area is used to evaluate the long-term impact. Furthermore, a computationally efficient time domain model of a 10 MW offshore wind turbine is used to compare with the frequency domain results. Results show that benefits in terms of structural fatigue can be obtained with directional considerations.