Reliability Analysis of Offshore Wind Structures Considering the Korean Met-ocean Conditions

Abstract

Offshore structures are predominantly affected by hydrodynamic loadings such as wave and wind loads. In the case of Europe, IEC and DNV documents had been developed based on the construction experiences of offshore wind structures, but in Korea, there are no design codes only for offshore winds and marine energy. Meanwhile, IEC and DNV documents adopt the reliability design method, which is a partial safety factor based on the LSD (Limit State Design). However, since these documents were developed under European met-ocean conditions, it is necessary to develop the reliability design method suitable for the Korean met-ocean conditions to satisfy the safety level required by overseas documents. Thus, this paper conducted the reliability analysis of offshore wind structures using the design methods provided by ABS and IEC. The Level Ⅲ (Monte Carlo Simulation) method, which is one of the reliability analysis techniques, was used. And long-term wave and wind data of the Korean west sea were calculated by numerical simulation, and design parameters were estimated using extreme analysis. As a result, in the case of the Korean coast, where typhoons are dominant, the reliability index was calculated lower than in Europe due to the higher variation of design variables such as wind. The results showed that a more careful approach should be taken to install offshore wind turbines in areas affected by typhoons. In the absence of Korean design codes for offshore wind power, it is inevitable to apply overseas codes to secure reliability. However, in order to apply overseas codes, usability under the Korean met-ocean conditions must be reviewed. In addition, it is judged that it is necessary to introduce the Level Ⅰ reliability design method (partial safety factor method) and to establish the design equations considering the statistical characteristics of design variables in Korea.