1 Department of Civil Engineering, The Faculty of Engineering and Science, Aalborg University, VBN2 The Faculty of Engineering and Science (ENG), Aalborg University, VBN3 Division for Structures, Materials and Geotechnics, The Faculty of Engineering and Science, Aalborg University, VBN4 Geotechnical Engineering, The Faculty of Engineering and Science, Aalborg University, VBN
When designing offshore monopiles without scour protection, the stiffness of the foundation will vary with time due to the dependency of the scour depth on current and sea conditions. Currently, design regulations of organizations such as Det Norske Veritas (DNV) and the International Organization for Standardization (ISO) recommend the use of the most extreme local scour depth as the design scour depth. This is a conservative approach, because the scour depth depends on the sea conditions and because the equilibrium scour depth is low during moderate to extreme wave loading. In this paper the effect of using expected scour depths when designing for the ultimate limit state and the fatigue limit state is illustrated by means of a desk study.