*4.1. Modeling*

We simulate a numerical model of a 7 MW jacket-supported turbine using the procedure outlined by Nielsen et al. [57] and applied by, e.g., Augustyn et al. [34]. The simulation procedure consists of the following steps: (1) the substructure model and corresponding wave loading are reduced to a Craig–Bampton superelement [58] with 30 internal modes accounting for internal substructure dynamics. A convergence study has been performed to ascertain that the reduced model (including 30 modes) adequately captures the relevant modal parameters of the non-reduced system. Subsequently, (2) the wind loading is computed through aero-elastic analyses, in which the substructure superelement is included. Finally, (3) the force-controlled recovery run outlined by Nielsen et al. [59] is performed, where the response of the substructure is recovered and relevant measurements are extracted. The applied model is formulated using state-of-the-art modeling approaches included in a typical design procedure for jacket substructures, and the model has been validated to accurately and precisely represent the structural dynamics of a combined substructure and wind turbine system [60,61].
