• Numerical study of a shared suction caisson anchor using taut and catenary moorings. • Investigated array of 15MW floating turbines at different water depths during storms. • Aero-hydrodynamic simulations show sustained cyclic loading on mooring lines. • 3D FE analysis suggests that suction caissons are suitable as shared anchors in sand. • The shared anchor withstood 50-year storm loads in both taut and catenary cases. Floating offshore wind arrays installed with shared anchors have been proposed as a cost-effective strategy for energy production. However, uncertainties about the ability of shared anchors to maintain station keeping under multidirectional storm loading may lead to over-conservative design. The modelling approach detailed in this study aims to reduce this uncertainty by capturing realistic mooring loads and applying them to the shared anchor. The characteristics of mooring loads from different mooring configurations are explored and the response of the shared anchor investigated. Mooring loads were obtained from simulations of the VolturnUS-S reference floating offshore wind turbine model under extreme sea states, considering both taut and catenary mooring in varying water depths. Mooring loads were then applied to a geotechnical model, and a nonlinear dynamic finite element analysis was undertaken using the advanced Sanisand-MS constitutive model to explore the performance of the shared anchor. The results show that shared suction caisson anchors installed in sand deposits can maintain performance during peak 50-year return period environmental loading events. The shared anchor appears to provide a sufficient vertical tensile capacity under drained conditions. While progressive upward ratcheting of the caisson, sufficient to deteriorate anchor performance, appears unlikely over the service lifetime, further investigation is required. Optimising mooring design to reduce the load inclination angle on the anchor could help mitigate this potential risk. Given the current uncertainties in the performance and modelling of shared anchors, this study provides useful insights into the mooring loading regimes and subsequent performance of shared anchors in sand.
Barron et al. (Sat,) studied this question.