Publications

Polyester ropes are attractive for reducing the costs of mooring systems for floating offshore wind turbines. Their tension-strain response, however, is nonlinear, path-dependent, and sensitive to loading rate and duration. The Syrope Joint Industry Project proposed a visco-elasto-plastic framework that captures these complex stiffness characteristics. In this model, the dynamic stiffness under fast cyclic loading varies linearly with mean tension, which is applicable to both wave-frequency (WF) and low-frequency (LF) loads, while slow effects are represented by the so-called working curves. Conventional practice of implementing the Syrope model performs a quasi-static analysis along the working curves to obtain mean tension, followed by a dynamic analysis at this working point using the corresponding dynamic stiffness. As part of the ESOMOOR project (www.esomoor.eu) co-funded by EU’s CETPartnership, we introduce a fully dynamic, time-domain implementation of the Syrope model that eliminates this split, in which the mean tension is estimated without switching between static and dynamic solvers. In the Syrope model, the total stretch is decomposed into permanent and elastic parts. Permanent stretch is tracked by the preceding highest mean tension, which defines the current working curve. Whenever a higher mean tension is detected, the preceding highest mean tension as well as the active working curve is updated. Elastic stretch is represented by a fast spring in series with a Kelvin–Voigt element (dashpot and slow spring in parallel). The fast spring responds instantly to both fast and slow loading, whereas the Kelvin–Voigt branch is inactive at high rates because the dashpot locks the slow spring. Dashpot damping can be tuned to separate WF/LF loads from other slow loads. The implementation has been verified against DNV Syrope data by comparing the tension-strain path across a series of several different sea states. The integration into the open-source MoorDyn codebase is in progress.

The advancement of floating offshore wind energy demands innovative and robust mooring and shared infrastructure solutions to enable scalable, cost-effective deployment of future wind farms. This review provides a comprehensive overview of shared mooring systems for floating offshore wind applications, with a focus on system configurations, environmental load considerations, modelling methods and mooring cost estimations. Existing concepts of shared mooring and shared anchoring are summarized and discussed. Drawing on insights from numerical studies, industrial practices, and academic research, the paper identifies key technical challenges and gaps in current design methodologies, validation requirements, and regulatory frameworks. Recommendations are proposed to guide future research aimed at improving system reliability, optimizing mooring layouts, and lowering the levelized cost of energy for large-scale floating wind projects.