Comparison of Fatigue Damage Caused by Wave and Wind for a Semi-Submersible Wind Turbine Structure

Abstract

Abstract Floating wind turbine structures are subjected to complex fatigue damage resources, such as wave dynamic, blade motion, turbine vibration, wind turbulence, structure vibration and so on. A study of a semi-submersible wind turbine structure has revealed that the load from wind turbine significantly affects the fatigue behavior of the structure. However, how the load is comprised and how impacts fatigue life is unknown. Lately developed fully coupled time domain global analysis are capable of getting the time history of wind turbine tower bottom load. A study is performed to analyze the load the get the components of the loads. To get fatigue life of the whole structure, a complete structure model instead of hydro model is required. Due to the complication of the fully coupled time domain structural analysis, it is required to develop a methodology for coupling wind and wave impact on the fatigue life of the structure. In this study, time domain wind turbine load is used to compute the fatigue life due to wind and spectral fatigue method is used to computer fatigue life caused by wave. Then the fatigue damages were combined and compared to give suggestions for the future floating wind turbine structures.