A French Recommended Practice for Planning and Designing Anchor Foundations of Floating Wind Turbines

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Considering the acceleration of call for tenders involving floating wind turbines in French waters, Recommendations for Planning and Designing Anchor Foundations of Floating Wind Turbines have been developed by a Working Group of CFMS during the period 2019-2023. These recommendations aimed to assist all stakeholders involved in the design and installation of foundations for floating offshore wind turbines in the French territorial waters in the absence of normative documents or national regulatory texts.

This Recommended Practice is devoted to the geotechnical aspects related to the design and installation of anchors for unmanned floating offshore wind turbines (FOWT) with a focus on anchor design. The recommendations cover various types of anchors commonly used in the industry, including drag embedment anchors (DEAs), plate anchors, pile anchors, suction anchors and gravity anchors.

In evaluating the safety of a station-keeping system, the safety of both the mooring system and the anchor point cannot be dissociated; the redundancy of the global system plays a pivotal role. Verification procedures adhere to the framework of the Load and Resistance Factor Design (LRFD) philosophy. Different load factors are proposed for the design of redundant versus non-redundant mooring lines and tendons. These load factors align with the guidelines outlined in DNV-ST-119 (2021).

The design of the anchors considers an original approach where safety is contingent on the material or resistance factors. These factors account for the level of redundancy of the anchor point relative to the anchor type and the loading direction. The chosen values for these material or resistance factors are consistent with those recommended in normative documents for the oil and gas industry, .

The proposed paper presents a summary of the content of the Recommendations with focus on the most significant aspects.

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

17 - Design Standards, Certification and Risk Mitigation