Sensitivity Analyses of Dominant Design Variables for Semi-Submersible Type Substructure of a 15MW Floating Offshore Wind Turbine

Abstract This study classifies semi-submersible floats into center column and side column types, analyzing kinematic response differences based on key design variables. Using the IEA 15 MW reference model, draft, circumradius, main column diameter, and pontoon breadth were set as variables. A Python-based automatic modeler generated 220 analytical models per type for frequency response analysis. Heave natural periods were derived, and long-term values of maximum pitch angle and RNA acceleration were obtained for a 20-year recurrence period. Greater draft reduced long-term RNA acceleration and pitch angle for both types. The side column type exhibited significantly higher long-term RNA acceleration, while the center column type had a greater long-term pitch angle. Among design variables, circumradius had the most significant influence. These findings will support a float geometry optimization methodology under development, enhancing floating offshore wind turbine performance and stability.