Load analysis and structural strength evaluation of semi-submersible platform for wind turbines in Jeju Island sea states using hydrodynamic-structure interaction analysis

Abstract

The present study conducted an analysis of waves and wind on the west coast of Jeju Island in South Korea to derive the loads for a structural analysis under operational, extreme, and survival conditions and then evaluated the structural strength of the DeepCwind semi-submersible platform of NREL for 5 MW wind turbine. As a floating structure is exposed to wind and wave loads in a highly changeable marine environment and consists of tubular joints with slender-element members, a load analysis is necessary for strength evaluation and design of the structure. The wave scatter diagrams based on KORDI's 24-year measurements of sea states and the annual mean wind speeds were used as the operational conditions. A sea state with a period that is very likely to cause the resonance of a floating structure was applied as the extreme condition. Another sea state during the Bolaven, a typhoon passing west of Jeju Island in 2000, is adopted as the survival condition. The surface pressure distribution of DeepCwind calculate through hydrodynamic analysis was applied to a structural analysis model based on a hydrodynamic-structure interaction analysis. The evaluation of the structural strength is performed in accordance with the provisions of DNV-OS-C201 and API-2A-WSD under operational, extreme, and survival conditions.