CFDST-Taper형 해상풍력 모노파일의 안정성 연구 = Stability of Tapered Monopile Offshore Wind Turbine with Concrete Filled Double Steel Tubular

다국어 초록 (Multilingual Abstract)

In the context of accelerated climate change and the imperative for sustainable development, there has been a global surge in efforts to curtail greenhouse gas emissions. This has precipitated a corresponding surge in demand for renewable energy, with offshore wind power emerging as a focal point. To enhance the operational efficiency of offshore wind farms, wind turbines are currently undergoing enlargement, accompanied by a parallel increase in the structural capacity of substructures. This study proposes a foundation for a tapered monopile for an offshore wind turbine and performs an extreme load analysis on the monopile. The structure is a tapered monopile comprising a concrete-filled double steel tubular (CFDST) bonded between the MSL and the mudline. The principal objective of the structure is to reduce the wave loads on the offshore wind turbine and to ensure the structural integrity of the substructure in an efficient manner. To guarantee the structural stability and practicality of this monopile and to ascertain its variability with different variables, nine scenarios were devised for the tapered CFDST monopile based on its taper length and hollow ratio. Two additional scenarios were also developed and analyzed for comparison with constant cylinder monopile. A three-dimensional finite element model was constructed for the purpose of analysis, and the reliability of the model was verified by comparing the results of field tests with the results of finite element analysis. A model was constructed to simulate the installation of tapered CFDST monopiles at the Port of Majishan, situated to the northeast of the Zhoushan Islands in the East China Sea. The model was populated with environmental loads, ground properties, and material properties based on data obtained from the field. The model was subjected to an extreme load analysis in order to reflect the interaction between the sandy soil and the structure. As a consequence, it was determined that the lateral displacement was markedly diminished when the tapered CFDST monopile structure was implemented, and that the structure is secure from resonance when applied to offshore wind turbines. Furthermore, it was demonstrated that the requisite safety factors were met for each component, even under conditions of extreme loading, thereby substantiating the practical applicability of the tapered CFDST monopile.

목차 (Table of Contents)

• 제 1 장 서론 1
• 제 2 장 이론적 배경 및 연구 내용 10
• 2.1 CFDST(Concrete-Filled Double Steel tubular) 10
• 2.1.1 CFDST의 정의 및 구조 10
• 2.1.2 CFDST 활용 사례 12
• 2.2 극한 하중 산출 14
• 2.2.1 영구하중 14
• 2.2.2 풍하중 15
• 2.2.3 파하중 15
• 2.2.4 OpenFAST와 DLC(Design Load Case) 16
• 2.3 연구 사이트 정보 18
• 2.3.1 Metocean data 19
• 2.4 지반 20
• 2.4.1 지반 정보 20
• 2.4.1 지반-구조 상호작용 21
• 2.5 유한요소 해석 23
• 2.5.1 ANSYS Static structure와 유한요소 해석 23
• 2.5.2 유한요소 모델 정보 25
• 2.5.3 연구 시나리오 29
• 2.5.4 유한요소 모델 검증 32
• 제 3 장 구조 해석 결과 34
• 3.1 높이별 횡변위 34
• 3.2 Soft-Stiff 설계를 위한 고유진동수 확인 36
• 3.3 외부 강관 최대 Von-mises 응력 38
• 3.4 콘크리트 부 최대 인장응력 42
• 3.4.1 주 응력의 크기 비교를 통한 확인 46
• 3.4.2 주 변형률 결과를 통한 확인 49
• 3.5 내부 강관 최대 Von-mises 응력 50
• 3.6 머드라인에서의 모노파일 회전각 50
• 제 4 장 결론 52
• REFERENCE 54