Time Domain Global Dynamic Analysis and Load Generation Methodology for Floating Offshore Wind Turbine Substructures

Ensuring the structural reliability of floating offshore wind turbine (FOWT) substructures requires global dynamic analysis methods that can accurately capture the combined effects of wind, waves, and currents. On the other hand, conventional integrated analysis tools focus primarily on global motions and are limited in their ability to represent structural responses. This paper presents a time-domain global analysis procedure and load-generation methodology that enable detailed finite-element structural analysis of FOWT platforms. The hydrodynamic coefficients were calculated using KR3D based on potential theory and incorporated into OpenFAST to perform fully coupled aero-hydro-elastic simulations under design loading conditions. The simulation results provided the basis for reconstructing all major time-domain load components, including tower-base loads, mooring tensions, inertial forces, wave pressures, and internal pressures. These loads are generated using coordinate transformations, transfer functions, and motion-based formulations. The reconstructed loads show strong agreement with the corresponding global dynamic results in terms of the amplitude and phase. Structural response analyses further showed that the applied loads produce physically consistent deformation patterns and stress distributions across critical structural regions. The proposed methodology enhances time-domain structural evaluation while efficiently linking global dynamic analysis.