• 대한기계학회논문집
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• 제15권3호
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• pp.771-788
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• 1991

본 연구에서는 편심된 강성 강화 부재가 붙어 있는 얇은 판 또는 얇은 셸에 대해 유한 요소 해석을 할 때, 편심된 강성 강화 부재를 개별된 요소로서 정확히 묘사 할 수 있도록, 일반적인 보 이론을 기초로 하여 2개의 절점을 갖고, 각 절점당 6자유 도를 갖는 3차원 편심 보 요소(offset beam element)에 대하여 수식화하여 변위와 응 력을 계산한다.

• 대한토목학회논문집
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• 제26권1A호
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• pp.191-203
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• 2006

가정 변형률 9절점 쉘 요소를 이용하여 스티프너로 보강된 적층 복합 보강판의 진동 특성을 연구하였다. 기존의 연구결과들과 비교하기 위하여 대칭으로 적층된 carbon-epoxy 복합재료 적층 판을 사용하였다. 또한 본 연구에서 스티프너를 쉘로 모델링 한 결과들은 보 요소로 모델링 된 결과들과 비교하였다. 비틀림에 약한 스티프너의 경우에 국부 좌굴이 스티프너에서 발생할 수 있다. 이 경우에 스티프너는 쉘로 모델링 하여야 한다. 본 연구는 면내 압축 및 전단하중을 받는 적층 복합 보강 판과 보강되지 않은 적층 복합 판의 연구에 집중되어 있다. 면내 압축 및 전단하중은 적층복합 판의 고유진동수와 진동 모우드를 변화시키고 압축 하중의 증가는 압축 하중이 임계 좌굴하중에 도달하여 진동수가 0 이 될 때 까지 진동수를 감소시킨다. 면내 전단하중의 작용은 그렇지 않은 경우에 비하여 진동수를 증가시켰다. 또한 진동수와 면내 하중 관계 곡선의 교차는 적층 복합 보강판의 진동 모우드를 교체 시킨다. 본 연구에서 제시한 쉘 요소로 적층 복합 보강판을 해석한 결과 참고문헌과 비교하여 매우 정확한 결과를 나타내었다. 그러므로 보강된 적층 복합 판의 면내 전단 및 압축하중의 종류와 크기는 특정한 진동수와 모우드 형상의 조절을 위해 적절하게 선택되어야 한다. 고유치 문제를 풀기 위하여 Lanzcos 방법을 사용하였다.

• Composites Research
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• 제13권6호
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• pp.9-22
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• 2000

한 방향으로 상자형 단면을 갖는 보강재로 보강된 복합재료 사각판에 대한 고유진동수 및 한 방향 압축, 양방향압축, 양 또는 음의 전단하중에 대한 임계좌굴하중에 대한 이론적 해석을 위해 에너지법을 기초로 한 Rayleigh-Ritz 과정이 이용되었다. 해석과정에서 판 구조물에서의 보강재에 의한 보강효과를 표현하기 위해 이산보강이론이 도입되었다. 해의 정확도를 검증하기 위해 수렴성 검토가 이루어졌으며, 몇 가지 예에 대해 진동 및 좌굴모드형상의 contour plot이 제시되었다. 보강재의 수, 위치, 형상비와 판의 적층각, 형상비 등과 같은 변수에 따른 영향을 중점적으로 설명하였다.

• Journal of Welding and Joining
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• 제32권2호
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• pp.54-62
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• 2014

Manhole cover, which is usually made of grey cast iron and consists of frame and cover, should have enough strength to support the heavy traffic load. The manhole cover made of cast iron has heavy weight to handle manually and is vulnerable to impact force with its brittle characteristics. Moreover, its production process of casting has been regulated in terms of environmental pollution. In this study, steel manhole cover is proposed to substitute the cast cover with a series of structural analyses to confirm its strength to support the test load for manhole cover. The cover of the proposed steel manhole cover is made of thin circular pate and stiffeners below the plate. Rectangular columns and hollow circular plate were selected for the shape of the stiffener. In order to give enough strength for the cover to behave within elastic range in the loading, strengthening structures of the cover were varied with increasing the number and the size of the stiffeners. The results of the analyses revealed that when both the hollow circular stiffener and cross stiffeners were additionally applied at the same time to the steel cover with longitudinal stiffeners, the maximum stress level in the cover could be reduced to that level presented in the cast cover.

• 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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• 제42권2호
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• pp.175-182
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• 2005

It is necessary to develop an efficient optimization technique to optimize the engineering structures which have given design spaces, discrete design values and several design goals. As optimization techniques, direct search method and stochastic search method are widely used in designing of engineering structures. The merit of the direct search method is to search the optimum points rapidly by considering the search direction, step size and convergence limit. And the merit of the stochastic search method is to obtain the global optimum points by spreading point randomly entire the design spaces. In this paper, a Pareto optimal based multi-objective function method (PMOFM) is developed by considering the search direction based on Pareto optimal points, step size, convergence limit and random search generation . The PMOFM can also apply to the single objective function problems, and can consider the discrete design variables such as discrete plate thickness and discrete stiffener spaces. The design results are compared with existing Evolutionary Strategies (ES) method by performing the design of double bottom structures which have discrete plate thickness and discrete stiffener spaces.

• 한국해양공학회지
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• 제33권5호
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• pp.411-420
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• 2019

It is essential to design crashworthy marine structures for operations in Arctic regions, especially ice-covered waters, where the structures must have sufficient capacity to resist iceberg impact. In this study, a numerical analysis of a colliding accident between an iceberg and stiffened plates was carried out employing the commercial finite element code ABAQUS/Explicit. The ice material model developed by Liu et al. (2011) was implemented in the simulations, and its availability was verified by performing some numerical simulations. The influence of the ambient temperature on the structural resistance was evaluated while the local stress, plastic strain, and strain energy density in the structure members were addressed. The present study revealed the risk of fracture in terms of steel embrittlement induced by ambient temperature. As a result, the need to consider the possibility of brittle failure in a plate-stiffener junction during operations in Arctic regions is acknowledged. Further experimental work to understand the structural behavior in a plate-stiffener junction and HAZ is required.

• 대한조선학회 특별논문집
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• 대한조선학회 2009년도 특별논문집
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• pp.123-129
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• 2009

Ship painting procedures can be divided into two categories; Out-shell plate painting of the hull and the interior painting of each double gull blocks. It is really hard to apply standardized and automated operations to the latter because the double hull blocks contains a variety of complicated supportive materials and pipes to strengthen the ship structure. In addition their poor working conditions cause painting workers to avoid working in them, resulting in the waste of paints and additional pollution issues. So this research, successfully focused on overcoming the difficulties in working in the complicated blocks and the tough working conditions introduces the main details of automatic equipment systems and their transfer algorism which show how the equipment paints the inner sides of a longitudinal stiffener and moves to another automatically.

• Steel and Composite Structures
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• 제25권5호
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• pp.535-544
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• 2017

Box sections are symmetrical sections and they have high moment of inertia in both directions, therefore they are good members in tall building structures. For the rigid connection in structures with box column continuity plates are used on level of beam flanges in column. Assembly of the continuity plates is a difficult and unreliable work due to lack of weld or high welding and cutting in the fourth side of column in panel zone, so the use of experimental stiffeners have been considered by researchers. This paper presented an experimental investigation on connection in box columns. The proposed connection has been investigated in four cases which contain connection without internal and external stiffeners(C-0-00), connection with continuity plates(C-I-CP), connection with external vase shape stiffener (C-E-VP) and connection with surrounding plates(C-E-SP). The results show that the connections with vase plates and surrounding plates can respectively increase the ultimate strength of the connection up to 366% and 518% than the connection without stiffeners, in case connection with the continuity plates this parameter increases about 39%. In addition, the proposed C-E-VP and C-E-SP connection provide a rigid and safe connection to acquire rigidity of 95% and 98% respectively. But C-I-CP connection is classified as semi-rigid connections.

• 대한조선학회지
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• 제17권4호
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• pp.1-11
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• 1980

Stiffened plates are commonly used as a component of ship's structures. Most frequently symmetrically stiffened plates are used, but some of stern structures and any specified parts are often constructed with eccentrically stiffened plates. The problems of these eccentrically stiffened plates have been studied rarely, and the results of eccentricity effect of eccentrically stiffened plates are not available. This paper deals with the analysis of eccentrically stiffened plates in the linear elastic range. The derivation of the stiffness matrix was carried out by finite element method for which the isoparametric element was adopted. To show the effect of eccentricity, the deflection at the center under the uniformly distributed and the concentrated load of simply supported and clamped plate models are computed respectively in accordance with the eccentricity of the stiffener. As shown in the results of computations, the eccentricity effect of concentrated load case is greater than that of distributed load case and that of simply supported boundary condition is greater than that of clamped boundary condition. The higher eccentricity of stiffener is, the smaller the effect of stiffener becomes, therefore scantling of eccentrically stiffened plates should be considerably greater than those of symmetrically stiffened plates.