풍력 터빈 타워 구조물의 최종 강도에 미치는 설계 변수 영향에 관한 실험 및 수치적 연구 = Experimental and Numerical Investigation of the Effects of Design Parameters on the Ultimate Strength of Wind Turbine Tower Structure

다국어 초록 (Multilingual Abstract)

Wind turbine tower structures composed of slender steel cylindrical shells serve as the primary load-bearing components in the entire system. With the recent trend towards larger wind turbines, the tower height is increasing while the wall thickness remains relatively thin. Consequently, the structures can be particularly susceptible to buckling. Among various loading scenarios, wind turbine towers are specifically subjected to two main concentrated loads: laterally concentrated loads due to wind on the rotor and torsional loads due to blade rotation. Under these loading conditions, due to the thin and tall structural characteristics of the slender cylindrical shells, the ultimate strength of wind turbine towers may be lower than the allowable design strength, leading to collapse. Therefore, to achieve more robust tower designs, it is essential to conduct research on ultimate behavior, including the buckling and ultimate strength of slender cylindrical shells, which are influenced by material properties, boundary conditions, and loading scenarios. This study aims to identify the influence of design parameters on the ultimate behavior of wind turbine tower structures under upper torsional and lateral loading conditions. To this end, a nonlinear finite element analysis technique under each loading condition was developed. The reliability of this numerical method was validated against experimental tests on scaled-down shell models for lateral loading conditions and through theoretical analysis for torsional loading conditions. Subsequently, a total of 3,125 finite element models were created by combining five levels of key tower design parameters (height, bottom diameter, bottom thickness, and bottom-to-top diameter and thickness ratios), incorporating initial imperfections based on the first eigenbuckling mode to account for geometric imperfections. Based on the numerical results, a sensitivity analysis of the design parameters was conducted to identify the influence of each design parameter on the ultimate behavior of the tower structure. The results offer valuable insights into optimizing the structural design of both onshore and offshore wind turbine towers by providing fundamental data for understanding their structural behavior under torsional and lateral loading conditions.

목차 (Table of Contents)

• Ⅰ. 서 론 1
• Ⅱ. 유한요소해석 기법 개발 4
• 1. 해석 대상 풍력 터빈 타워 모델 4
• 2. 유한요소해석 모델링 6
• 3. 메쉬 수렴성 분석 8
• 4. 초기 기하학적 불완전성 10
• Ⅲ. 유한요소해석 기법 신뢰성 검증 14
• 1. 측면 하중 하 유한요소해석의 실험적 검증 14
• 가. 실험 대상 모델 및 실험 개요 14
• 나. 실험 및 유한요소해석 결과 극한 거동 비교 20
• 다. 실제 및 수치적 기하학적 불완전성이 구조 거동에 미치는 영향 23
• 2. 비틀림 하중 하 유한요소해석의 이론적 검증 24
• Ⅳ. 풍력 터빈 타워 설계 변수의 민감도 분석 26
• 1. 측면 하중 하 극한 거동에 관한 민감도 분석 26
• 2. 비틀림 하중 하 극한 거동에 관한 민감도 분석 37
• 3. 최종 강도에 대한 설계 변수의 상관관계 분석 47
• Ⅴ. 결론 및 고찰 50