A probabilistic evaluation of wind turbine fatigue design rules

In wind turbine fatigue design, it is customary to use the partial safety factor approach: loads are inflated by some factor, while material fatigue strength is decreased in calculations. Values for partial factors used originally come from civil engineering standards for utility buildings and bridges, and it is not clear that they are optimal for wind turbines. In the paper, an inventory of important stochastic parameters influencing fatigue loads is given, and their estimated distributions are presented. With this information, failure probabilities due to fatigue are determined, as well as the relative importance of the stochastic parameters for total uncertainty. Using a simple cost model, economically optimal failure probabilities and partial factors are derived. The main conclusion of the presented work is that uncertainties in material fatigue properties and life prediction methods dominate total uncertainty, and hence determine the required partial factors. Copyright © 2008 John Wiley & Sons, Ltd.