반 잠수식 해양플랜트의 캐스팅 구조물 형상 최적화 설계에 관한 연구

다국어 초록 (Multilingual Abstract)

The offshore structures are exposed to repeated dynamic loads, such as wave loads and wind loads, depending on sea conditions. These dynamic loads produce considerably high stress concentrations at the point where the cross section of the offshore structure. In particular, stress concentrations occur in areas such as column-deck and column-pontoon. Therefore, structural reinforcement is essential in these areas. Thus these are connected to the casting structure to which the fillet is applied for structural reinforcement. It is called casing and cast-integral.

Recently, the demand and importance of cast structures have been emphasized as marine resource development has increased. However, the production cost of a Cast-integral is significantly higher than typical steel structure. Also, Cast-integral for offshore structures are supplied exclusively by two companies of the world. There is a question whether the shape design for the high production cost of the casting and the radius of the fillet is the optimal shape. Therefore, we tried to establish the optimum design method.

This study was conducted as follows: First, cast models without fillets were constructed in three dimensions. Second, the plate extension sub-model was constructed for applying the load and boundary conditions without global analysis. Third, the analysis results of the sub-model were used as constraints for optimization. Fourth, the finite element analysis was performed using the analysis results in the previous step for the cast-integral model with fillet. Fifth, for the approximate approach, the design of experiments(D.O.E) of the cast-integral with fillet was constructed using the fillet radius as a variable and the analysis results were derived. Sixth, the response surface was constructed using the results derived from D.O.E. Seventh, an approximation of the optimal solution using the genetic algorithm was derived using the configured response surface. Finally, the approximate optimal solution was used as the initial value to derive the fine optimal solution.

In this study, we could suggest design methods of Cast-integral, even if the design parameters were insufficient on the initial design stage. the design method of the fillet radius to obtain the desired strength of the cast-integral is established. In this study, we propose a relatively accurate and fast design method of cast-integral. Finally, design methods were established to improve approximate errors.

목차 (Table of Contents)

• 1. 서 론 1
• 1.1 연구배경 1
• 1.2 관련 연구 3
• 1.3 연구 목적 및 개요 5
• 1.3.1 Cast-integral의 3D Model 구성 6
• 1.3.2 Plate extension Sub-model 7
• 1.3.3 Fillet이 적용되지 않은 Cast-integral의 구조해석 8
• 1.3.4 실험계획법(Design of Experiments)을 이용한 Fillet이 적용된 Cast-integral의 구조해석 9
• 1.3.5 반응 표면법(Response Surface Method) 10
• 1.3.6 근사 최적화 11
• 1.3.7 국부 최적화 11
• 2. Cast-integral 구조물의 구성 12
• 2.1 Cast-integral 구조물의 기본 형상 12
• 2.1.1 Cast-integral case1 12
• 2.1.2 Cast-integral case2 13
• 2.2 Plate Extension submodel 구성 14
• 2.2.1 Cast-integral case1 의 Sub-model 15
• 2.2.2 Cast-integral case2 의 Sub-model 16
• 3. 경계 조건 및 하중 조건 17
• 3.1 하중 조건 및 Case 정리 17
• 3.2 Plate Extension Sub-model의 경계 조건 21
• 4. Cast-integral 형상 최적화 24
• 4.1 실험계획법과 반응표면법 24
• 4.2 Approximate Optimization 28
• 4.2.1 최적화 정식화 28
• 4.2.2 근사 최적화 결과 30
• 4.3 Local Fine Optimization 33
• 4.4 Cast-integral 형상 최적화 설계 36
• 5. 결 론 41
• 참고문헌 42
• ABSTRACT 44