Reliability of an offshore wind turbine with an uncertain S-N curve

Abstract

Probabilistic methods in wind turbine design are becoming more important in order to achieve a higher and more economic utilization of the structural resources. A design is thereby evaluated through its reliability by taking uncertainties into account. The influence of uncertainties emerging specifically within the fatigue limit state can be essential on a structure's reliability. For that reason, this study investigates two different sources for uncertainties within probabilistic fatigue design. The influence of a reduced approach, where the random behavior of a structural failure is only represented through an uncertain critical Miner sum, is compared to an approach, where also the S-N curve is subjected to uncertainties. For this, an offshore wind turbine with monopile support structure is investigated. The reliability analysis is performed through crude Monte Carlo simulations which utilize a Gaussian Process regression model in order to determine the wind turbine's structural response. The results show that both sources of uncertainties, the critical Miner sum and the S-N curve, contribute differently to the overall reliability. Uncertainties of the critical Miner sum have a rather small influence, whereas the implementation of an uncertain S-N curve leads to a noticeable increase of the reliability.