• 대한조선학회논문집
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• 제42권3호
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• pp.284-289
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• 2005

A structural design system is developed for the optimum design of double hull tankers based on the multi-objective function method. As a multi-objective function method, Pareto optimal based random search method is adopted to find the minimum structural weight and fabrication cost. The fabrication cost model is developed by considering the welding technique, welding poses and assembly stages to manage the fabrication man-hour and process. In this study, a new structural design is investigated due to the rapidly increased material cost. Several optimum structural designs on the basis of high material cost are carried out based on the Pareto optimal set obtained by the random search method. The design results are compared with existing ship, which is designed under low material cost.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 가을 학술발표회 논문집
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• pp.249-256
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• 1999

This study is intended to propose a systematic procedure for the development of the reliability-based seismic safety and cost-effective Performance criteria for design and upgrading of long span PC bridges. In the paper, a set of cost function models for life cycle cost analysis of bridges is proposed. The total life cycle cost functions consist of initial cost and direct/indirect damage costs considering repair/replacement costs, human losses and property damage costs, road user costs, and indirect regional economic losses. The damage costs are successfully expressed in terms of Park-Ang median global damage indices and damage probabilities. The proposed approach is successfully applied to model bridges in both regions of a moderate seismicity area like Seoul, Korea and a high one like Tokyo, Japan. It may be expected that the proposed approach can be effectively utilized for the development of cost-effective performance criteria for design and upgrading of various types of bridges as well as long span PC bridges.

• 한국자동차공학회논문집
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• 제15권3호
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• pp.63-71
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• 2007

During the design phase of a product, reliability and design engineers are called upon to evaluate the reliability of the system, The question of how to meet target reliability for the system arises when estimated reliability or cost is inadequate. This then becomes a problem of reliability allocation and system structure design. This study proposes the optimization methodology to achieve target reliability with minimum cost through construction of the cost function of system. In cost function, total cost means the sum of initial cost, repair cost and maintenance cost. This study constructs optimization problem about system structure design and reliability allocation using cost function. This problem constructed is solved by Multi-island Genetic Algorithm(MIGA), and applies to urban transit brake system. Current brake system of the urban transit is series system. Series system is the simplest and perhaps one of the most common system, but it demands high reliability and maintenance cost because all components must be operating to ensure system operation. Thus this study makes a comparative study by applying k-out-of-n system to brake system. This methodology presented can be a great tool for aiding reliability and design engineers in their decision-makings.

• Computers and Concrete
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• 제13권4호
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• pp.457-482
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• 2014

This paper summarizes available literature on the optimization of reinforced concrete (RC) beams. The objective of optimization (e.g. minimum cost or weight), the design variables and the constraints considered by different studies vary widely and therefore, different optimization methods have been employed to provide the optimal design of RC beams, whether as isolated structural components or as part of a structural frame. The review of literature suggests that nonlinear deterministic approaches can be efficiently employed to provide optimal design of RC beams, given the small number of variables. This paper also presents spreadsheet implementation of cost optimization of RC beams in the familiar MS Excel environment to illustrate the efficiency of the exhaustive enumeration method for such small discrete search spaces and to promote its use by engineers and researchers. Furthermore, a sensitivity analysis is performed on the contribution of various design parameters to the variability of the overall cost of RC beams.

• Structural Engineering and Mechanics
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• 제50권3호
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• pp.323-347
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• 2014

This paper proposes a Particle Swarm Optimization (PSO) algorithm, which is improved by making use of the Harmony Search (HS) approach and called HS-PSO algorithm. A computer code is developed for optimal sizing design of non-linear steel frames with various semi-rigid and rigid beam-to-column connections based on the HS-PSO algorithm. The developed code selects suitable sections for beams and columns, from a standard set of steel sections such as American Institute of Steel Construction (AISC) wide-flange W-shapes, such that the minimum total cost, which comprises total member plus connection costs, is obtained. Stress and displacement constraints of AISC-LRFD code together with the size constraints are imposed on the frame in the optimal design procedure. The nonlinear moment-rotation behavior of connections is modeled using the Frye-Morris polynomial model. Moreover, the P-${\Delta}$ effects of beam-column members are taken into account in the non-linear structural analysis. Three benchmark design examples with several types of connections are presented and the results are compared with those of standard PSO and of other researches as well. The comparison shows that the proposed HS-PSO algorithm performs better both than the PSO and the Big Bang-Big Crunch (BB-BC) methods.

• 한국통신학회논문지
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• 제19권7호
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• pp.1390-1406
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• 1994

본 논문은 로컬 엑세스 컴퓨터 네트워크를 설계할 때 발생되는 문제의 하나로 네트워크의 평균 지연 시간을 고려한 최소 비용 루프 설계 문제(DMCLP-Delay constrained Minimum Cost Loop Problem)를 다룬다. 이 문지는 종단 사용자의 트래픽 요구량을 만족시키는 링의 집합을 구하는 것으로 목적 함수는 전체라인 비용을 최소화하는 것이다. 본 논문에서는 하나의 링이 서비스할 수 있는 노드의 수가 제한되어 있으며 동시에 네트워크의 평균 지연 시간이 원하는 시간이내이어야 한다는 제약 조건하에서 이 문제에 대한 2단계-휴리스틱 알고리즘을 제안한다. 이 알고리즘은 기존의 최소 비용 루프 설계(MCLP) 알고리즘에 의한 클러스터와 본 논문에서 제안한 trade-off criterion를 이용하여 유도된다. 실제 시뮬레이션의 결과, 본 논문에서 제안한 알고리즘은 수정된 기존의 MCLP 알고리즘보다 우수한 해를 제공하며 아울러 비교적 짧은 실행 시간을 갖는다.

• 대한토목학회논문집
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• 제34권6호
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• pp.1845-1850
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• 2014

철도 운영측면에서 비용을 최소화하는 최적노선을 설계하기 위해서는 다양한 지형 위에 설계기준에 맞는 노선을 배치하여야 하며, 절토량과 성토량을 최소화 하거나 이 둘의 합을 균형화 하여 공사비용을 최소화하고 있다. 열차의 효율적인 운행을 가능하게 하는 노선의 설계는 다양한 변수의 해 공간을 모두 고려하여야하기 때문에 조합최적화의 문제라고 할 수 있다. 본 연구에서는, 공사비를 최소화 하는 최적 철도 노선을 설정하기 위한 수리적 모형을 개발하였으며, Genetic Algorithm을 사용한 문제의 해석을 하였고, Algorithm과 결과를 활용한 철도 최적 노선 설계 개념을 정립하였다. 그리고 가상의 구간에 대한 사례적용을 통하여 본 연구에서 제시하고 있는 방법론에 대하여 평가하여 성토량과 절토량을 균형화 할 수 있음을 확인하였다. 이러한 결과는 실제적으로 수명 동안의 에너지 비용이 공사비보다 높은 현실에서 철도노선설계의 최적화 과정에서 중요하게 활용될 수 있을 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 추계학술대회 논문집 학회본부
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• pp.400-402
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• 1994

The voltage drop in distribution path of battery-reserved DC power system can affect the total of battery, cable and electricity costs. To determine an optimum voltage drop in distribution path for minimizing the total cost, battery, cable and electricity costs are represented as a function of the voltage drop, respectively, and are summed up to the total cost. An optimum voltage drop is selected as the value giving the minimum total cost. In this paper, a design technique of optimum voltage drop in distribution path of DC power system is proposed to minimize the total of battery, cable and electricity costs. The design procedure is described and design curve for selecting optimum voltage drop is also presented as a function of distribution distance.

• 전기학회논문지
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• 제57권8호
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• pp.1429-1433
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• 2008

In this paper, we consider the design method of robust guaranteed cost controller for discrete-time singular systems with norm-bounded time-varying parameter uncertainty. In order to get the optimum(minimum) value of guaranteed cost, an optimization problem is given by linear matrix inequality (LMI) approach. The sufficient condition for the existence of controller and the upper bound of guaranteed cost function are proposed in terms of strict LMIs without decompositions of system matrices. Numerical examples are provided to show the validity of the presented method.

• 대한조선학회지
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• 제21권4호
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• pp.29-39
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• 1984

In this paper, the membrane and buckling analysis of beams with various shaped brackets is performed by using the finite element method. From the viewpoint of minimum structural weight, a optimum design method to determine the optimal shapes and scantling of brackets under design load is proposed by investigating the effects of beam depth, bracket length and aspect ratio on the structural weight. Also optimal design data and charts for the brackets to support transverse girders or web frames of actual ships are provided. By the present design method, it is possible to perform optimum design of brackets used in actual ships, which could result in considerable reduction of structural weight or cost, increase of dead weight and service speed of ships.