Impact of cyclic contour diagram definition on monopile design for offshore wind turbines 

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In the design of monopile foundations for offshore wind turbines, accurate modelling of cyclic soil degradation is a key factor due to the effects of cyclic wind and wave loading. Rambolls in-house approach relies on the definition of unit-specific cyclic contour diagrams and load redistribution along the monopile. If cyclic soil data is limited, literature contour diagrams are generally scaled to match the trend shown by laboratory test results in order to define design inputs. Alternatively, cyclic contour diagrams can be defined solely based on the results of cyclic tests, when these are deemed to be sufficient to define new diagrams. The latter approach might offer a more accurate input to the analysis but requires a more detailed cyclic testing programme. Overall, the chosen methodology will impact the outcome of the strain or pore pressure accumulation analysis and, therefore, the definition of unit- and depth-specific degradation factors resulting from load redistribution. This paper illustrates the impact of different approaches in defining input contour diagrams on the monopile design. The analysis helps identifying areas for modification of the cyclic contour diagram generation to improve its robustness under various conditions.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

9 - Monopile design to cyclic loads: quasi-static, dynamic and seismic loads