Partial Safety Factors for Fatigue Design of Wind Turbine Blades

In the present paper calibration of partial safety factors for fatigue design of wind turbine blades is considered. The stochastic models for the physical uncertainties on the material properties are based on constant amplitude
fatigue tests and the uncertainty on Miners rule for linear damage accumulation is determined from variable amplitude fatigue tests with the Wisper and Wisperx spectra. The statistical uncertainty for the assessment of the fatigue
loads is also investigated.

The partial safety factors have been calibrated for different variations of the stochastic models in order to determine the influence from each of these. In general model uncertainty on the aerodynamics has the largest influence on the
partial safety factors followed by the physical uncertainty on the material properties and the model uncertainty on Miners rule. In the paper a framework is presented for determination of the partial safety factors depending on the
level of model and statistical uncertainty. This could be useful for manufactures that perform additional measurements or calculations in order to bring down the model and statistical uncertainties.