Safety evaluation of large-scale floating wind turbines under extreme typhoon-wave conditions

Coupled extreme typhoon wind and wave loading poses severe challenges to the structural safety of large-scale floating offshore wind turbines (FOWTs). However, a comprehensive framework that integrates typhoon-environment reconstruction, coupled dynamic analysis, and component-level safety assessment remains lacking. This study develops an integrated wind-wave-structure assessment framework by combining parametric typhoon wind-field modeling, coupled SWAN-ADCIRC wave simulations, and fully coupled time-domain aero-hydro-servo-elastic analysis. The typhoon wind field is reconstructed from in situ measurements, and the simulated wave field is evaluated against ERA5 reanalysis data. The dynamic responses and safety margins of four benchmark FOWT systems (NREL 5 MW, DTU 10 MW, IEA 15 MW, and IEA 22 MW) are investigated under consistent typhoon-wave conditions. A rapid response prediction framework based on dimensional analysis and dominant physical mechanisms is further developed to improve computational efficiency. Physically interpretable dimensionless parameters and explicit polynomial models are used to predict structural responses and quantify the contributions of wind- and wave-induced excitations. The results show that blade responses are primarily governed by wind excitation, whereas tower responses exhibit greater sensitivity to wave-induced platform motion. Blade-tip deflection and platform pitch are identified as the principal safety indicators under intensified typhoon conditions, while the governing constraints vary among the four FOWT systems. The proposed framework provides an efficient and physically interpretable approach for assessing FOWT safety and supports the development of typhoon-adapted design criteria for next-generation floating wind turbines.