Abstract This paper introduces a closed-form analytical formulation for the stiffness matrix of floating systems with shared mooring. The model accounts for surge, sway, and yaw motions (thus, considering only motions on the horizontal plane) and can be applied both at neutral and displaced equilibrium positions. It provides rapid and consistent estimates of restoring forces and stiffness properties, offering a computationally efficient alternative to finite-element or iterative approaches. A two-platform Floating Offshore Wind Farm (FOWF) case study illustrates the formulation. Results show non-intuitive couplings and additional yaw stiffness, confirmed by comparison with finite-element simulations. Analysis of natural modes and periods reveals how independent platform motions transform into collective dynamics when coupling is considered. Modal veering phenomena are also identified when natural periods approach themselves under external mean force loads. It is important to emphasize that this formulation complements high-fidelity numerical tools, providing a fast and insightful framework for early stage assessments of FOWFs with shared mooring.
Amaral et al. (Tue,) studied this question.