Reliability-based Calibration of Fatigue Safety Factors for Offshore Wind Turbines

This paper describes reliability-based investigations on the required safety factors / Fatigue Design Factors (FDF) values to be used for fatigue design of steel substructures for offshore wind turbines. Design and limit state equations are formulated and stochastic models for the uncertain strength and load parameters are described. Further, the effect of possible inspections during the design lifetime is investigated. The results indicate that for fatigue critical details where the fatigue load is dominated by wind load FDF values equal to 2.5 are required. If wave load is dominating slightly larger FDF values are required.This paper describes reliability-based investigations on the required safety factors / Fatigue Design Factors (FDF) values to be used for fatigue design of steel substructures for offshore wind turbines. Design and limit state equations are formulated and stochastic models for the uncertain strength and load parameters are described. Further, the effect of possible inspections during the design lifetime is investigated. The results indicate that for fatigue critical details where the fatigue load is dominated by wind load FDF values equal to 2.5 are required. If wave load is dominating slightly larger FDF values are required