1 Research Group of Wind Turbines, The Faculty of Engineering and Science, Aalborg University, VBN2 Department of Civil Engineering, The Faculty of Engineering and Science, Aalborg University, VBN3 Division of Structural Mechanics, The Faculty of Engineering and Science, Aalborg University, VBN
This paper describes a reliability-based approach to determine fatigue design factors (FDF) for offshore wind turbine support structures made of steel. The FDF values are calibrated to a specific reliability level and linked to a specific inspection and maintenance (I&M) strategy used for the considered offshore wind turbines in such a way that the specific uncertainties for the fatigue life are accounted in a rational manner. Similar approaches have been used for offshore oil & gas sub-structures, but the required reliability level for offshore wind turbines is generally lower and the fatigue loading is different. Based on representative stochastic models and response functions a set of FDF values are determined which depend on the degree of accuracy of the fatigue analysis and the consequences of fatigue failure of a critical detail. It is illustrated how the FDF values can be reduced if inspections are planned during the design life, and thereby the basis is available for selecting a cost-effective fatigue design. Further, the results can be used as basis for recommendations in standardization.
Ewec 2010 Conference Proceedings: Europe's Premier Wind Energy Event, 2010