• 대한조선학회논문집
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• 제48권2호
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• pp.178-182
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• 2011

Generally in order to reduce the steel weight of stiffened plate, stiffener spaces tend to be narrow and the plate gets thin. However, it will involve more fabrication cost because it can lead to the increase of welding length and the number of structural members. In the yard, the design which is able to reduce the total fabrication cost is needed, although it requires more steel weight. The purpose of this study is to find optimum stiffener spaces to minimize the fabrication cost for the cargo tank of LPG Carriers. Global optimization methods such as ES(Evolution Strategy) and GA(Genetic Algorithm) are introduced to find a global optimum solution and the sum of steel material cost and labor cost is selected as main objective function. Convergence degree of both methods in according to the size of searching population is examined and an efficient size is investigated. In order to verify the necessity of the optimum design based on the cost, minimum weight design and minimum cost design are carried out.

• 대한조선학회논문집
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• 제47권4호
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• pp.598-605
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• 2010

The structural design of oil tankers and bulk carriers should be performed based on the Common Structural Rules(CSR) which were recently established by the International Association Classification Societies(IACS). At first, in the structural design viewpoint, the scantling and hullweight based on the CSR should be compared with those of existing rules, and then a minimum weight/cost design should be performed by considering the variation of the number of web and the material property. In this study, the optimum web space and material property will be proposed by performing a minimum weight/cost design of a large oil tanker, and the results will be compared with those of existing ship. The longitudinal members are determined by SeaTrust-Holdan developed by the Korean Register of Shipping(KR), and the transverse members are determined by NASTRAN and PULS.

• Structural Engineering and Mechanics
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• 제15권1호
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• pp.39-52
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• 2003

A computer program has been developed for the optimum design of prestressed concrete beams under flexure. Optimum values of prestressing force, tendon configuration, and cross-sectional dimensions are determined subject to constraints on the design variables and stresses. 28 constraints have been used including flexural stresses, cover requirement, the aspect ratios for top and bottom flanges and web part of a beam and ultimate moment. The objective function contains cost of concrete, prestressing force and formwork. Using this function, it is possible to obtain minimum cost design, minimum weight or cross-sectional area of concrete design and minimum prestressing force design. Besides the idealized I-shaped cross-section, which is widely used in literature, a general I-shaped cross-section with eight geometrical design variables are used here. Four examples, one of which is available in the literature and the others are modified form of it, have been solved for minimum cost and minimum cross-sectional area designs and the results are compared. The computer program, which employs modified grid search optimization method, can assist a designer in producing efficient designs rapidly and easily. Considerable savings in computational work are thus made possible.

• 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.

• International Journal of Naval Architecture and Ocean Engineering
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• 제2권4호
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• pp.217-222
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• 2010

Since 1980's, optimum design techniques for ship structural design have been developed to the preliminary design which aims at minimum weight or minimum cost design of mid-ship section based on analytic structural analysis. But the optimum structural design researches about the application for the detail design of local structure based on FEA have been still insufficient. This paper presents optimization technique for the detail design of a racing motor boat. To improve the performance and reduce the damage of a real existing racing boat, direct structural analyses; static and non-linear transient dynamic analyses, were carried out to check the constraints of minimum weight design. As a result, it is shown that the optimum structural design of a racing boat has to be focused on reducing impulse response from pitching motion than static response because the dynamic effect is more dominant. Optimum design algorithm based on nonlinear finite element analysis for a racing motor boat was developed and coded to ANSYS, and its applicability for actual structural design was verifed.

• 한국농공학회지
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• 제37권E호
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• pp.31-39
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• 1995

Weight minimization for the steel bridge girders using an approximation based optimization technique is presented. To accomplish this, an optimization oriented finite element program is used to achieve continuous weight reduction until the optimum is reached. To reduce computational cost, approximation techniques are adopted during the optimization process. Constraint deletion as well as intermediate design variables and responses are also used for higher qualitv of approximations and for a better convergence rate. Both the reliability and the effectiveness of the underlying optimization method are reviewed.

• 한국CDE학회지
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• 제21권2호
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• pp.50-60
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• 2015

Corresponding to the high consumption rate of the selfie stick for cell phone camera, the design of the product is becoming diverse. However, relatively low cost selfie stick models are not strong enough to stand the weight of the cell phone. This results into a bending of the stick or the accidental fall of the cell phone by the failure of the holding unit. As a solution to the problem, design of selfie stick that is structurally strong enough to stand the weight of the cell phone with the minimum weight for the portability is proposed in this paper.

• 한국전산구조공학회논문집
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• 제15권4호
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• pp.591-598
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• 2002

공학적 설계에 있어 많은 문제들은 몇 가지 목적함수들을 동시에 최소화하여야 할 필요가 있을 경우가 있다. 선박설계에 있어, 종래에는 자재비 경감과 재화중량 증가를 위해 최소중량설계가 구조 설계의 주된 목적이었으나, 값싼 노동력을 내세운 후발 조선국과의 치열한 국제 경쟁을 극복하기 위해서는 보다 경제성 있는 선박 건조 기술 개발이 선행되어야 할 것이다. 이에 따라 본 연구에서는 다목적함수 최적화기법을 이용한 선체 구조의 보다 합리적인 설계 방안에 대한 연구를 수행하여 실제 건조된 유조선을 대상으로 중량, 건조비 등의 경제성을 비교 평가하였다. 다목적 함수로는 유조선의 중량과 건조비로 하였으며 최적화 기법으로는 확률론적 탐색법인 ES(Evolution Strategies)를 이용하였다. 건조비 모델은 상대 건조비 개념을 도입하였고, 종강도 부재는 선급규정에 의해, 횡강도 및 횡격벽 부재는 직접해석법인 일반화된 경사처짐법을 사용하여 설계에 적용하였다. 다목적함수 최적화 결과로부터 도출된 Pareto 최적 설계점들에 대하여, 요구운임률을 각각 산정함으로써 이들 최적 설계점들 중에서 가장 경제성이 뛰어난 선박 설계 방안을 제시하였다.

• 대한조선학회논문집
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• 제59권1호
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• pp.39-45
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• 2022

Normal strategy of structure optimization procedure has been minimum cost or weight design. Minimum weight design satisfying an allowable stress has been used for the ship and offshore structure, but minimum cost design could be used for the case of high human cost. Natural frequency analysis and forced vibration one have been used for the strength estimation of marine structures. For the case of high precision experiment facilities in marine field, the structure has normally enough margin in allowable stress aspect and sometimes needs high natural frequency of structure to obtain very high precise experiment results. It is not easy to obtain a structure design with high natural frequency, since the natural frequency depend on the stiffness to mass ratio of the structure and increase of structural stiffness ordinary accompanies the increase of mass. It is further difficult at the grillage structure design using the profiles, because the properties of profiles are not continuous but discrete, and resource of profiles are limited at the design of grillage structure. In this paper, the grillage structure design system under the constraint of high natural frequency is introduced. The design system adopted genetic algorithm to realize optimization procedure and can be used at the design of the experimental facilities of marine field such as a towing carriage, PMM, test frame, measuring frame and rotating arm.

• Structural Engineering and Mechanics
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• 제45권2호
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• pp.211-232
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• 2013

In this study a multi-objective optimization problem is solved. The objectives used here include simultaneous minimum construction cost in term of sections weight, minimum structural damage using a damage index, and minimum non-structural damage in term of inter-story drift under the applied ground motions. A high-speed and low-error neural network is trained and employed in the process of optimization to estimate the results of non-linear time history analysis. This approach can be utilized for all steel or concrete frame structures. In this study, the optimal design of a planar eccentric braced steel frame is performed with great detail, using the presented multi-objective algorithm with a discrete population and then a moment resisting frame is solved as a supplementary example.