Predicting Ultimate Loads for Wind Turbine Design

This paper addresses the statistical uncertainty of loads prediction using structural dynamics simulation codes and the requirements for the number and duration of simulations for obtaining robust load estimates. Substantial statistical variation is observed in loads data and a statistical model that enables extrapolation and determination of quantiles is presented. Further reduction in thenumerical work necessary to determine extreme loads with an acceptable uncertainty is possible using a stochastic process model for the dynamic responses. A procedure allowing for a slightly non-Gaussian response is proposed and satisfactory accuracy is found. Finally, the extreme loads from the revised IEC 61400-1 wind turbine standard on safety requirements are calculated for the turbine, andloads from the gust models and the properly extrapolated simulation extremes are compared.