Fatigue Analysis Of Offshore Wind Turbine Mono-pile Support Structure

Offshore wind turbine support structure is an important component of offshore wind farm. The support structure is subjected to cyclic loads caused by both aerodynamic force and hydrodynamic force. During the service life, the cycle counts of the loads are so large that fatigue strength of the support structure deserves special attention. WAsP was used to analyze the wind data of a wind farm and the distribution of the wind speed was gained. The parameters of wind, wave and current for each working condition were calculated. The control strategy of generator was figured out based on momentum-blade element theory. According to the stochastic transient sequences of wind speed and the running condition of the turbine, turbine loads and wind pressure acting on the offshore wind turbine mono-pile support structure were calculated. The loads caused by wave and current were also worked out through Morison equation. ABAQUS was used to model the offshore wind turbine mono-pile support structure, the dynamic response was calculated through mode superposition method and the stress time history was figured out. According to S-N curves, rainflow counting method and Miner's linear damage theory, fe-safe was used to work out the fatigue damage of the structure for each working condition. The fatigue life of the support structure was estimated and the effect of different kinds of loads on the structure fatigue life was also researched. The results showed that the fatigue life of the support structure meets demand; The stress caused by wind turbine loads is higher and the variation amplitude is larger than that cased by other loads, wind turbine loads are key influence factor of the fatigue life; Sensible generator control strategy is good for reducing the fluctuation of the turbine loads and increasing the fatigue life.