Reconsidering fatigue limit state load sets for jacket substructures utilizing probability distributions of environmental states

Combinations of environmental conditions like wind, wave, and current states are often simplified or related to high demands on numerical capacity in fatigue design of offshore wind turbines. To address this recent topic, a fatigue study is performed where a basis of 2048 design load cases is incrementally reduced to smaller subsets. The full load set contains information on real measurement data in terms of probability distributions that were derived from the research platform FINO3, located in the German North Sea. With the aim of obtaining knowledge about the required design load set size, a reduction study is performed. Joint damages of two representative jacket substructures (one three-legged and one four-legged jacket) are calculated with the aero-servo-hydro-elastic simulation framework FAST. The present study shows that the degree of uncertainty in fatigue damage evaluation is high when considering realistic environmental conditions.