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The development of offshore wind technology has become a feasible solution to meet the increasing demands for clean and renewable energy. The United States has a total of 4250GW offshore wind energy potential; however, 65% of it is in deep water zones (Lopez et al., 2022) where wind turbines with fixed foundations typically are economically and technically unfeasible. In those situations, floating turbines supported by subsea anchors are a more competitive solution. Based on previous studies, ring anchors can be more material-efficient than piles and caissons because they require less material. Ring anchors also perform better than drag anchors due to their greater embedment depth. To further understand the behavior of ring anchors in saturated sand, a series of centrifuge load tests were performed at the University of California Davis Center for Geotechnical Modeling (CGM) at an acceleration of 70g. This test series investigated the effect of the anchor embedment depth and loading angle on the monotonic loading behavior. The ring anchor models were embedded in dense saturated sand, and then connected to an actuator using taut steel wire ropes. Sensors were used to measure the line tension, displacement, and inclination. The results indicate that the ring anchors mobilize greater capacities as their embedment depth is increased and when they are loaded at angles close to the horizontal direction, while vertical loading leads to the smallest capacity. The anchor displacement during the tests deviated slightly from the loading direction, showing a horizontal deviation at the earlier stages of the tests and a vertical one after the peak load. Furthermore, soil disturbance induced by the anchor installation was found to have a strong effect on the vertical capacity of the ring anchors. Overall, this study provides valuable information regarding the monotonic loading behavior of ring anchors which can aid in their future field deployment. 

A multiline ring anchor (MRA) system has been developed as a cost-effective alternative for securing arrays of floating offshore wind turbines (FOWTs) to the seabed. Multiline attachments can improve the economically competitiveness of FOWTs by reducing the capital cost of the support system for the floating structures. FOWTs can be subjected to severe wind and wave conditions resulting in extreme loads to the anchor system. Thus, the reliable design of the anchor system requires proper determination of the extreme mooring line loads acting on the anchor needed to secure FOWTs to the seabed. Previous studies showed the MRA in soft clay has clear advantages over existing anchors under the extreme horizontal loading conditions imposed by catenary moorings; however, its performance relative to conventional anchors under extreme vertical loading imposed by taut mooring systems requires further investigation. This study presents predictions of extreme loads on floating structures secured by taut mooring systems and evaluates the potential for developing an economical anchor for resisting these extreme loads. 

The trend of offshore wind energy in deeper water that is expected to shift from fixed to floating platforms requires a cost-effective anchor solution for floating offshore wind turbines (FOWTs). Multiline ring anchor (MRA) has been developed as a cost-effective solution for FOWTs due to its capability of anchoring multiple mooring lines, its high efficiency, and its availability to a wide range of soils and loading conditions. While previous preliminary studies on the anchor performance provide useful insights on how the potential advantages of the MRA can improve load capacity, these studies are limited to focusing on optimizing the anchor design in certain soil and loading conditions. By contrast, the MRA will be installed in seabeds under more complex conditions that depend on geological location, water depth of at-place, and environmental conditions, of which wind, current, and wave are major components. These may result in additional substantial extra capital costs, delays in the projects, and safety issues, when the complex conditions are not properly considered. Specifically, the installation time and expenses of the offshore anchor are very susceptible to anchor types, installation methods, and environmental conditions. For this reason, this paper compares two existing offshore anchor installation methods and different anchor types on the basis of their performance under the same severe environmental condition. In evaluating the installability of the MRA, this paper conducts a comparative scenario study. The results show that the anchor installations and anchor handling vessel (AHV) operations are sensitive to weather conditions and AHV sizes. In view of total weather standby, the results show that anchor types or installation methods have little effect on it due to their relatively shorter duration than other work sequences. However, the MRA can benefit in substantially reducing transport time and costs due to its compact size. The MRA can be more efficient and cost-effective than other alternatives under complex and severe weather conditions.