Abstract: This paper presents an approach to calculate the fatigue damage of offshore wind turbine foundation caused by wave load. On the basis of wave spectrum and random wave theory, random sea wave was transformed into a series of linear waves. The wave force was obtained and linearized by employing the Morison equation. Through dynamic analysis on the foundation structure under the liner wave force, the structure response was obtained to calculate the transfer function of structural stress within the frequency area. Furthermore, the stress spectrum of hot spot was obtained based on the wave spectrum and transfer function. By assuming that the long period hot spot stress distribution obeys short time Rayleigh model, the accumulated fatigue damage of the structure in a sea area in designed lifetime was obtained in the light of the Miner’s theory. A single-pile foundation case is taken to verify the feasibility of this calculation approach. This research could be a reference for the fatigue design of offshore wind turbine foundation.

Key words: offshore wind turbine foundation, fatigue analysis, transfer function, spectrum analysis