Pile anchors of floating offshore wind farms subjected to lateral cyclic loadings in different directions 

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This paper presents a numerical study to investigate the behaviour of pile anchors used to support Floating Offshore Wind Turbines (FOWTs). In conventional FOWT farms, each anchor is attached to a single FOWT and thus the anchor is said unshared with the other neighbouring FOWTs and it is subjected to a single unidirectional irregular loading. In order to reduce the high costs of FOWT farms, the behaviour of a shared anchor was recently investigated in literature. Anchor sharing consists of designing a foundation to anchor multiple neighbouring FOWTs organised in an array, rather than designing a set of anchors for each FOWT. Anchor sharing will notably cause irregular cyclic loading on the anchor in different directions. This case corresponds to a global multidirectional irregular loading. This paper presents a numerical study using Abaqus finite element implicit solver to investigate the effect of the global load multi-directionality on the behaviour of pile anchors in sandy soil. Two extreme loading cases among a total of 32 load cases corresponding to a given wind farm layout and a prescribed sea-state were considered in the analysis. Also, two configurations of shared and unshared anchors were investigated for comparison purposes. In the first case, the anchor was subjected to a global irregular lateral load with high amplitude and small directional variation. However, in the second loading case, the anchor was subjected to an irregular global lateral load with a moderate amplitude and a high directional variation. The numerical results have shown that the anchor design is mainly governed by the loading case associated with a high amplitude and small directional variation. The classical unshared anchor design is thus not affected by a possible anchor sharing between multiple FOWTs.

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

13 - Developmental foundation and anchoring concepts: hybrid foundations, ring anchors, helical piles, torpedo, shared anchoring