Stress Estimation Based on Stochastic Method for Strength Evaluation of Floating Wind Turbines

Structural integrity assessment of floating wind turbine (FOWT) systems is performed based on fully coupled load analysis in time domain and structural analysis that consider the complex interactions among wind, wave, and currents. However, there is a limit to repeating load and structural analyses several times for numerous DLCs required in actual projects. In this study, to determine the reasonable analysis time for structural integrity evaluation, actual time series for 1 hour and 3 hours were calculated based on FOWT load and structural analysis. Next, each time series was stochastically fitted to Weibull distribution function. The most probable maximum (MPM) von-Mises stresses were estimated according to the probability level corresponding to the design life of the platform on the fitted curves. The maximum von-Mises stress from 1 h and 3 h showed a large deviation depending on the analysis time, while the MPM von-Mises stress estimated by applying the same probability level did not show a large deviation, and the variability according to random execution also showed a similar trend. Through further research, it is expected that the optimal analysis time for estimating MPM stress can be determined, allowing for efficient structural integrity assessment for FOWT.