• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.2
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• pp.135-148
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• 2013

Recently, road tunnels have become longer and the plans for long and deep road tunnel have been underway in urban areas. These long and deep tunnel excavations include NATM and TBM. Shield TBM is applied to around 80% of traffic tunnels in Europe, and approximately 30% of them in other developed countries. However, as much of equipment is imported from foreign countries at high prices and distribution rate of TBM tunnel is considerably low in Korea, NATM excavation method is commonly used. To increase TBM tunnel, it is necessary to do assure economic feasibility with the supply-demand of TBM equipment. For this, the selection of standardized TBM diameter is urgently needed. Therefore, the study aims to estimate the standardized optimum section properties of TBM by examining TBM excavation cross section utilization depending on the volume of traffic, the number of lane and its cross-section type(single or double deck), and ventilation system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.1
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• pp.39-46
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• 1993

The need to develop method which can improve the shape design efficiency using high quality approximation is being brought up. In this study, to perform shape optimal design of three-dimensional continuum structures an efficient approximation method for stress constraints is proposed, based on expanding the nodal forces in Taylor series with respect to shape variables. Numerical examples are performed using the 3-D cantilever beam and fixed-fixed beam and compared with other method to demonstrate the efficiency and convergence rate of the Force Approximation method. It is shown that by taking advantage of this high quality approximation, the total number of finite element analysis required for shape optimization of 3-D continuum structures can be reduced significantly, resulting to the same level of efficiency achieved previously in sizing optimization problems. Also, shape representation by super curve technique applied to obtain optimal shape finds useful method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.1109-1110
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• 2012

• Transactions of Materials Processing
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• v.5 no.4
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• pp.281-287
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• 1996

Two kinds of blank shapes optimum and square are adopted to investigate formability. Optimum blank shape is determined to construct an L-shape cup with uniform height and without flange part. For this purpose rigid-plastic FEM analysis is applied with backward tracing technique. Maximum cup depth and strain distribution are measured experimentally for the products of the two kinds of blank shapes which are optimum and square. it is confirmed that deeper cup without severe thickness reduction can be obtained from the optimum shape.

• Transactions of Materials Processing
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• v.5 no.2
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• pp.138-144
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• 1996

The differences of formability with maximum cup depth of drawn product and thickness strain distribution are compared for two kinds of blank shapes which are suggested optimum shape and conventional square shape. The suggested blank is determined by backward tracing technique of rigid-plastic FEM. The deeper cup without wrinkle and flange part could be obtained from the suggested blank shape however the cross sevtion sup from the square blank could not be kept smooth thickness strain distribution and defended those phenomena..

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.672-676
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• 2002

In this paper, a reliability-based design optimization method, which enables the determination of optimum design that incorporate confidence range for structures, is studied. Response surface method and Monte Carlo simulation are utilized to determine limit state function. The proposed method is applied to the I-type steel structure for reliability based optimal design.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1997.10a
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• pp.114-121
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• 1997

회전 열파이프의 열전달 성능은 액막 두께 및 증발부로 귀환되는 응축 액막 유동율에 의해 결정된다. 그 동안 응축액 유동율을 촉진시키기 위하여 용기 내벽에 groove, 테이퍼 및 나선형 코일을 삽입하여 유동율을 높이는 방법들이 연구되었다. 본 연구도 회전 열파이프의 내부 관벽 구조에 관한 것으로써 삼각 단면을 갖는 회전 열파이프의 열전달 특성을 파악하고자 하였다. 삼각 단면을 갖는 회전 열파이프는 고속 회전 영역에서 모서리 부분으로 액막이 집중되어 관 내벽에 형성되는 액막 두께를 줄일 수 있으나 증발부에서 국부적인 과열이 발생되어 불안정한 작동 상태를 나타내었다. 따라서 본 연구에서는 개선방안으로 증발부에 부분적으로 원형관을 접합하였으며, 그 결과 dry-out의 억제와 함께 삼각 유동 단면에 의한 액막 두께 감소 효과를 볼 수 있었다. 회전체 발열부 냉각에 적용시키기 위해서는 앞으로 최적의 기하학적 형상에 따른 충전율 및 액막에서의 열전달에 대한 정량적인 해석 연구가 필요할 것으로 생각된다.

• Journal of Korean Association for Spatial Structures
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• v.4 no.3 s.13
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• pp.77-84
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• 2004

This study presents an effective stiffness-based optimal technique to control quantitatively lateral drift for tall frameworks using composit member subject to lateral loads. To this end, displacement sensitivity depending on behavior characteristics of tall frameworks is established and approximation concept that preserves the generality of the mathematical programming and can efficiently solve large scale problems is introduced. Specifically, under the 'constant-shape' assumption, resizing techniqe of composite member is developed. Two types of 50 story frameworks are presented to illustrate the features of the quantitative lateral drift control technique proposed in this study.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.819-832
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• 2004

This study describes an efficient and facile method for configuration optimum design of structures. One of the ways to achieve numerical shape representation and the selection of design variables is using the design element concept. Using this technique, the number of design variables could be drastically reduced. Isoparametric mapping was utilized to automatically generate the finite element mesh during the optimization process, and this made it possible to easily calculate the derivatives of the coordinates of generated finite element nodes w.r.t. the design variables. For the structural analysis, finite element analysis was adopted in the optimization procedure, and two different techniques(the deterministic method, a modified method of feasible direction; and the stochastic method, a genetic algorithms) were applied to obtain the minimum volumes and section areas for an efficient configuration optimization procedure. Futhermore, spline interpolation was introduced to present a realistic optimum configuration that meet the manufacturing requirements. According to the results of several numerical examples(steel structures), the two techniques suggested in this study simplified the process of configuration optimum design of structures, and yielded improved objective function values with a robust convergence rate. This study's applicability and capability have therefore been demonstrated.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.383-390
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• 2019

A helideck is one of the essential structures in offshore platforms for the transportation of goods and operating personnel between land and offshore sites. As such, it should be carefully designed and installed for the safety of the offshore platform. In this study, a structural design optimization method for a lightweight offshore helideck is developed based on a genetic algorithm and an attainable design set concept. A helideck consists of several types of structural members such as plates, girders, stiffeners, trusses, and support elements, and the dimensions of these members are typically pre-defined by manufacturers. Therefore, design sets are defined by collecting the standard section data for these members from the American Institute of Steel Construction (AISC), and integer section labels are assigned as design variables in the genetic algorithm. The objective is to minimize the total weight of the offshore helideck while satisfying the maximum allowable stress criterion under various loading conditions including self-weight, wind direction, landing position, and landing condition. In addition, the unity check process is also utilized for additional verification of structural safety against buckling failure of the helideck.