@inproceedings{01JKWSCTKCRV9K0RWEWRT0MDE0,
  abstract     = {{As offshore wind energy advances, floating offshore wind turbines (FOWTs) provide a crucial solution for harnessing wind power in deep waters where fixed-bottom turbines are not viable. Traditional dynamic analysis of FOWTs considers their structural behaviour as the combination of a rigid substructure connected either to a flexible or rigid tower. The software packages used to perform these analyses, such as OpenFAST, have been developed in such a way that the loads at the tower base are easily extracted. As a result, the majority of research on the fatigue of the substructure focuses only on fatigue damage at the tower base. However, most FOWT substructures contain welded joints, which are known to be fatigue-critical locations. Hence, accurate assessment of the loads, and particularly the local stresses at these joints, is vital.

This study presents a novel time-domain numerical method to accurately map the loads from global hydro-servo-aero-elastic (dynamic) simulations to a detailed shell-based finite element model (FEM). The first step of the method is to implement the hydrostatic, inertial, mooring line, tower base, and Morison drag loads on the FEM. However, because the dynamic simulations assume a rigid substructure, hydrodynamic loads, such as diffraction, radiation, and Froude-Krylov loads, are simplified as concentrated forces at the substructure’s centre of gravity. For more accurate results, these loads should be represented as distributed pressure loads acting on the wetted surface elements of the FEM.

To achieve this, a boundary element method (BEM) solver is employed to calculate the distributed pressure loads in the frequency domain. The obtained pressure loads are then transformed into the time domain using the appropriate data from the dynamic simulations, i.e. the wave elevation for the diffraction and Froude-Krylov loads, and the platforms movement for the radiation loads. This approach allows for high-fidelity pressure load modelling in the FEM, facilitating the determination of accurate stress fields across the entire structure.

To validate the accuracy of the proposed method, the resultant loads from the FEM are compared to the loads extracted from the original dynamic simulations. This comparison shows that the load distribution is accurately captured on the FEM, confirming the method’s ability to model and map the forces reliably.  This means that accurate stress, and, in extension, fatigue life predictions can be determined for the FOWT substructure. These predictions are crucial for optimising the structural integrity and operational lifespan of offshore wind energy systems.}},
  author       = {{Rappe, Victor and Hectors, Kris and Ong, Muk Chen and De Waele, Wim}},
  booktitle    = {{EERA DeepWind Conference 2025, Abstracts}},
  keywords     = {{Finite element analysis,Fatigue,Floating offshore wind turbines}},
  language     = {{eng}},
  location     = {{Trondheim, Norway}},
  title        = {{Accurate load mapping for fatigue analysis of floating offshore wind turbine substructures}},
  url          = {{https://www.sintef.no/globalassets/project/eera-deepwind-2025/presentasjoner/3b-substructures_rappe.pdf}},
  year         = {{2025}},
}