고정식 해상풍력터빈에 대한 지반-말뚝 상호작용 및 세굴깊이를 고려한 신뢰성 해석

Abstract

Currently, multi-member lattice-type structures including jackets and tripods are being considered as one of good alternatives to monopile foundations for relatively deep water in the range of 25-50 m of water depth owing to their technical and economic feasibility. In this study, the reliability analysis of bottom-fixed offshore wind turbines with monopile and/or multi-member lattice-type foundations is carried out and the sensitivities of random variables such as material properties, external wind loadings and scouring depth are compared with respect to different types of foundations. Response surface method is incorporated to handle the implicit type of failure function for applying the first-order reliability method (FORM). From the nu-merical analysis of the NREL 5 MW wind turbine supported by monopile, tripod and jacket substructures, it is found that the uncertainties of soil properties affect the reliability index more significantly for the monopile-supported OWTs while the reliability index is not so sensitive to the material properties in the cases of tripod- and jacket-supported OWTs. In conclusion, the reliability analysis can be preliminarily carried out without the consideration on soil-pile-interaction in the cases of tripod- and jacket-supported OWTs when the soil properties are not fully known while it is very important to use the well-measured soil properties for reliable design of monopile-supporte and economic feasibility. In this study, the reliability analysis of bottom-fixed offshore wind turbines with monopile and/or multi-member lattice-type foundations is carried out and the sensitivities of random variables such as material properties, external wind loadings and scouring depth are compared with respect to different types of foundations. Response surface method is incorporated to handle the implicit type of failure function for applying the first-order reliability method (FORM). From the nu-merical analysis of the NREL 5 MW wind turbine supported by monopile, tripod and jacket substructures, it is found that the uncertainties of soil properties affect the reliability index more significantly for the monopile-supported OWTs while the reliability index is not so sensitive to the material properties in the cases of tripod- and jacket-supported OWTs. In conclusion, the reliability analysis can be preliminarily carried out without the consideration on soil-pile-interaction in the cases of tripod- and jacket-supported OWTs when the soil properties are not fully known while it is very important to use the well-measured soil properties for reliable design of monopile-supporte