Prediction of Springing-induced Extreme Responses of a TLP-Type Floating Wind Turbine

Floating wind turbines are designed to survive 50-year-extreme environmental conditions during their 20-year service life, as specified by International Electrotechnical Commission (IEC) standards. For a tension-leg platform (TLP)-type floating wind turbine, extreme wave loads can induce significant high-frequency resonant and transient responses, e.g. springing and ringing, which greatly amplify the structural responses of the floating wind turbines.

This study aims to predict the springing-induced extreme responses of the WindStar TLP system by using FAST__(Fatigue, Aerodynamics, Structures, and Turbulence), a fully coupled simulation tool. The hydrodynamic loads considered include both first- and second-order wave-excitation loads. Different simulation sizes are compared.

Different extreme-value prediction methods are applied and the results are compared. Both the peak-over-threshold (POT) and block maxima method (BMM) are applied to extract local maxima, which are then fitted using a threeparameter Weibull distribution. The average conditional exceedance rate (ACER) method and the Gumbel method are applied and compared with the above method.