Fatigue Reliability Assessment of Floating and Bottom-Fixed Offshore Wind Turbines

Abstract This study investigates the fatigue reliability of critical structural components in offshore wind turbines. It emphasises the significance of various design fatigue factors that critically influence the longevity and performance of these systems. The fatigue reliability of several vital areas, including the blade root, critical tubular members, and the tower base of the OC4 jacket wind turbine, the OC4 semi-submersible wind turbine, and the mooring line, is investigated. A key aspect is the definition of the fatigue limit state failure event, which serves as a benchmark for evaluating structural integrity under cyclical loading conditions. Various sources of uncertainty that can significantly influence these failure events, affecting the overall performance and safety of the wind turbines, are assessed and discussed. A case study is conducted to illustrate the variation in implied reliability for different support structures.