A simplified time-frequency fatigue analysis method considering the response characteristics of jacket-type offshore wind turbine

Fatigue evaluation of jacket-type offshore wind turbine (OWT) is critical for structural safety. In this paper, a simplified time-frequency method is proposed to enhance the efficiency and accuracy of fatigue analysis based on the response characteristics of jacket-type OWT. Firstly, the definition of the minimum sample simulation length is employed to improve calculation efficiency. The influence of sampling variability is verified based on fatigue damage with 5000 min simulation length. Then, the combination factor is selected by considering the jacket-type OWT response characteristics and the correction of the mean stress is used to improve the fatigue analysis calculation accuracy. The results show that the simplified method can achieve the minimal sample variability with the minimum simulation length. The combination factor in Ding-Chen method is more suitable for the jacket-type OWT due to the effect of the bandwidth parameter. The consideration of the mean stress correction improves the calculation accuracy of the short-term and long-term fatigue analyses by approximately 25% and 10%, respectively. These findings can contribute to the reference for the fatigue design of future jacket-type OWT.