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Jang, Beom-Seon,Yang, Young-Soon,Suh, Jung-Chun The Society of Naval Architects of Korea 2004 Journal of ship and ocean technology Vol.8 No.2
Ship design process requires lots of complicated analyses for determining a large number of design variables. Due to its complexity, the process is divided into several tractable designs or analysis problems. The interdependent relationship requires repetitive works. This paper employs collaborative optimization (CO), one of the multidisciplinary design optimization (MDO) techniques, for treating such complex relationship. CO guarantees disciplinary autonomy while maintaining interdisciplinary compatibility due to its bi-level optimization structure. However, the considerably increased computational time and the slow convergence have been reported as its drawbacks. This paper proposes the use of an approximation model in place of the disciplinary optimization in the system-level optimization. Neural network classification is employed as a classifier to determine whether a design point is feasible or not. Kriging is also combined with the classification to make up for the weakness that the classification cannot estimate the degree of infeasibility. For the purpose of enhancing the accuracy of a predicted optimum and reducing the required number of disciplinary optimizations, an approximation management framework is also employed in the system-level optimization.
FEA based optimization of semi-submersible floater considering buckling and yield strength
Beom-Seon Jang,Jae Dong Kim,Tae-Yoon Park,Sang Bae Jeon 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1
A semi-submersible structure has been widely used for offshore drilling and production of oil and gas. The small water plane area makes the structure very sensitive to weight increase in terms of payload and stability. Therefore, it is necessary to lighten the substructure from the early design stage. This study aims at an optimization of hull structure based on a sophisticated yield and buckling strength in accordance with classification rules. An in-house strength assessment system is developed to automate the procedure such as a generation of buckling panels, a collection of required panel information, automatic buckling and yield check and so on. The developed system enables an automatic yield and buckling strength check of all panels composing the hull structure at each iteration of the optimization. Design variables are plate thickness and stiffener section profiles. In order to overcome the difficulty of large number of design variables and the computational burden of FE analysis, various methods are proposed. The steepest descent method is selected as the optimization algorithm for an efficient search. For a reduction of the number of design variables and a direct application to practical design, the stiffener section variable is determined by selecting one from a pre-defined standard library. Plate thickness is also discretized at 0.5t interval. The number of FE analysis is reduced by using equations to analytically estimating the stress changes in gradient calculation and line search steps. As an endeavor to robust optimization, the number of design variables to be simultaneously optimized is divided by grouping the scantling variables by the plane. A sequential optimization is performed group by group. As a verification example, a central column of a semi-submersible structure is optimized and compared with a conventional optimization of all design variables at once.
FEA based optimization of semi-submersible floater considering buckling and yield strength
Jang, Beom-Seon,Kim, Jae Dong,Park, Tae-Yoon,Jeon, Sang Bae The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1
A semi-submersible structure has been widely used for offshore drilling and production of oil and gas. The small water plane area makes the structure very sensitive to weight increase in terms of payload and stability. Therefore, it is necessary to lighten the substructure from the early design stage. This study aims at an optimization of hull structure based on a sophisticated yield and buckling strength in accordance with classification rules. An in-house strength assessment system is developed to automate the procedure such as a generation of buckling panels, a collection of required panel information, automatic buckling and yield check and so on. The developed system enables an automatic yield and buckling strength check of all panels composing the hull structure at each iteration of the optimization. Design variables are plate thickness and stiffener section profiles. In order to overcome the difficulty of large number of design variables and the computational burden of FE analysis, various methods are proposed. The steepest descent method is selected as the optimization algorithm for an efficient search. For a reduction of the number of design variables and a direct application to practical design, the stiffener section variable is determined by selecting one from a pre-defined standard library. Plate thickness is also discretized at 0.5t interval. The number of FE analysis is reduced by using equations to analytically estimating the stress changes in gradient calculation and line search steps. As an endeavor to robust optimization, the number of design variables to be simultaneously optimized is divided by grouping the scantling variables by the plane. A sequential optimization is performed group by group. As a verification example, a central column of a semi-submersible structure is optimized and compared with a conventional optimization of all design variables at once.
FE Model Based Parametric Study Support System
Jang, Beom-Seon The Society of Naval Architects of Korea 2008 Journal of ship and ocean technology Vol.12 No.4
In preliminary ship design, a parametric study is a more realistic way to explore design space and analyze design problem than an optimization technique due to time-consuming computational work or a difficulty in incorporating all constraints into the optimization formulation. In the parametric study, feasible alternatives are examined in various aspects; the best one can be selected. Among the aspects, the strength assessment by FE analysis is an essential process in the ship design. This paper proposes a system to facilitate a parametric study for FE model based on design of experiment (DOE). It works on a FE pre-processor environment and assists a user to define a parametric study by interacting with FE model. It also provides an interface module with a FE solver in order to control the input file and extract predefined FE results from the output file. Based on the proposed system, a better understating and a better design are expected to be achieved.
지지조건에 따른 FPSO 상부 모듈의 구조적 거동에 관한 연구
장범선(Beom-Seon Jang),고대은(Dae-Eun Ko) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.11
FPSO는 원유의 생산을 위한 플랜트가 기능별로 모듈화 되어있는 상부구조(topside)와 생산된 원유의 저장 및 상부구조의 지지 기능을 하는 하부구조(hullside)로 구성된다. FPSO 상부 모듈과 이를 지지하는 선체의 구조적 거동은 이들을 연결하는 인터페이스 구조에 따라 달라지며, 인터페이스 구조의 형식은 MSS(Module Support Seat)라고 하는 개별 단위 지지구조들의 조합으로 구성된다. 인터페이스 구조의 형식이 다양하고 이에 따라 FPSO 상부 모듈 구조의 기본 설계가 크게 영향 받으므로 초기 설계 단계부터 다양한 설계 방안을 검토해야 한다. FPSO 상부 모듈의 구조 설계 시에는 선체와의 상호 작용을 고려하여 MSS의 개수, 연결 형식을 결정해야 하고, 구조 강도 검증을 위한 유한요소 모델의 범위, 하중 조건, 경계 조건 등 구조 해석 옵션을 신중히 고려해야 한다. 본 연구에서는 상기 고려 사항들에 대한 비교 조합 Case들을 도출하고 강도 평가를 수행하였으며, 해석 결과의 상세한 고찰을 통해 상부 모듈의 구조적 거동 특성을 비교 분석하였다. 본 연구 결과는 보다 신뢰성 있는 상부 모듈 구조 설계를 위한 좋은 참고 자료가 될 것으로 판단된다. FPSO consists of topside modularized plants for production of crude oil, and hullside structures that serve as support for the topside and storage of produced crude oil. The structural behavior of the FPSO topside module and its supporting hull depends on the interface structure that connects them, and the interface structure consists of a combination of individual unit support structures called Module Support Seat (MSS). Types of interface structures are various and, accordingly, the basic design of the FPSO topside module structure is greatly influenced, so various design methods should be considered from the initial design phase. Structural design of FPSO topside module requires consideration of the number of MSSs, connection type, and structural analysis options such as the range of finite element models, load conditions, and boundary conditions for verification of structural strength. In this study, the comparison combination cases for the above considerations were derived and the strength evaluation was performed, and the structural behavior characteristics of the topside module were compared and analyzed through a detailed review of the analysis results. The results of this study are considered to be a good reference for designing a more reliable topside module structure.
보강판의 좌굴 평가식에 따른 좌굴 강도 및 최적설계의 비교
장범선(Beom-Seon Jang),조호영(Ho-Young Cho) 한국해양공학회 2009 韓國海洋工學會誌 Vol.23 No.5
In ship design or offshore structure design, the evaluation of buckling strength (or ultimate strength) is critical to the determination of scantling of stiffened plates. For this reason, it is useful to study the effect of applying different formula or the relationship between stiffened plate with buckling utilization factor (UF). It can facilitate a designer to decide how much the scantling should be reinforced or how much can be reduced for an optimal design. This paper conducts a comparative study for three budding check methods; DNV-Ship-Rule, DNV-RP-C201, DNV-PULS. The capacity curves and 2D contour plot for utilization factors versus bi-axial in-plane stresses are compared. The contour plots of DNV-Ship-Rule and DNV-PULS show smoothly increasing trends of UF as the applied in-plane stresses increase, however that of DNV-RP-C201 shows rapidly increasing trend as the applied stresses go beyond transverse buckling stress. A sensitivity analysis is performed to investigate the influence level of each parameter of a stiffened plate on UF. Resulting from the analysis, plate thickness is identified to be the most affective parameter to UF regardless of the buckling check methods. Based on the addressed study, optimal designs for bottom plate of 165 K tanker corresponding to three formulas are compared with each other. DNV-PULS yields 1 ㎜ and 2 ㎜ less thickness than DNV-Ship-Rule and DNV-RP-C201, respectively.
포스터 발표 : 일차성 갑상선기능저하증 및 일차성 부신기능저하증이 합병된 환자에서 발생한 횡문근융해증 및 IgA신증 1예
장윤경 ( Jang Yun Gyeong ),장인선 ( Jang In Seon ),최범순 ( Choe Beom Sun ),신영신 ( Sin Yeong Sin ),진동찬 ( Jin Dong Chan ),김석영 ( Kim Seog Yeong ),장윤식 ( Jang Yun Sig ),방병기 ( Bang Byeong Gi ),서광선 ( Seo Gwang Seon ) 대한신장학회 2003 춘계학술대회 초록집 Vol.22 No.1