• Journal of Advanced Marine Engineering and Technology
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• 제23권5호
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• pp.702-710
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• 1999

U-shaped bellows are usually used to piping system pressure sensor and controller for refriger-ator. Bellows subjected to internal pressure are designed for the purpose of absorbing deformation. Internal pressure on the convolution sidewall and end collar will be applied to an axial load tend-ing to push the collar away from the convolutions. To find out deformation behavior of bellow sub-jected to internal pressure the axisymmetric shell theory using the finite element method is adopted in this paper. U-shaped bellows can be idealized by series of conical frustum-shaped ele-ments because it is axisymmetric shell structure. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displace-ments are added to r-z cylindrical coordinates of nodal points. The new stiffness matrix of the sys-tem using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacement that is the step by step method is used in this paper. The force required to deflect bellows axially is a function of the dimensions of the bellows and the materials from which they are made. Spring constant is analyzed according to the changing geometric factors of U-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM the internal pressure vs. deflection characteristics of a particu-lar bellows can be predicted by input of a few factors.

• Computers and Concrete
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• 제2권1호
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• pp.1-18
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• 2005

This paper presents a study on the effects of localized steel-concrete bond degradation on the flexural behaviour of RC beams. A finite element analysis is undertaken to complete the experimental analysis. The first part deals with an experimental study on beams where bond was removed by using plastic tube at different locations and for various lengths. The flexural behaviour was studied at global scale (load-deflection) and local scale (moment-curvature). The second part, a numerical study using a simplified special finite element (rust element) modelling the rust layer occurring between reinforcement and concrete with corrosion was conducted in order to find the relation between the degree of corrosion and the degradation of the steel-concrete bond. The computed value of the corrosion degree corresponding to the total degradation of bond has been used in a second time to model the tests, in order to evaluate the influence of the loss of bond, the steel cross section reduction, and the combination of both. The results enable to evaluate the influence of the different corrosion effects on the flexural behaviour, according to the length and the location of the corroded zone.

• 전산구조공학
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• 제7권4호
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• pp.69-83
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• 1994

평면 뼈대구조물의 매우 큰 변형에 대하여 정확한 비선형 유한요소의 정식화 과정을 나타내었다. 유한요소의 구성은 변화되는 재료의 기준 물성치에 근거를 두고 형성하였으며 매우 큰 변형을 받는 재료의 성질을 명확하게 특정지어 진응력-변형율 관계식을 직접 적용할 수 있도록 하였다. 큰회전과 작은 변형율을 받는 문제들을 형성하기 위하여 Co-rotation 접근 방법을 사용하였다. 큰 변형을 일으키는 요소의 문제를 해결하기 위하여 직선보 형태의 유한요소를 사용하였으며 개개의 유한요소의 정식화는 축방향력의 영향을 고려하여 미소 처짐보이론을 바탕으로 형성하였다. 본 연구에서 형성된 큰 변형에 대한 비선형 유한요소의 타당성을 확인하기 위해 몇몇 수치해들을 해석하고 검토하였다.

• 한국농공학회지
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• 제27권2호
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• pp.38-46
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• 1985

The reinforced concrete farm silos on the elastic foundatin are widely used in agricultural engineering because of their superior structural performance, economy and attractive appearance. Various methods for the analysis and design of farm silo, such as the analytical method, the finite difference method, and the finite element methods, can be used. But the analytical procedure can not be applied for the intricate conditions in practice. Therefore lately the finite element method has been become in the structural mechanics. In this paper, a method of finite element analysis for the cylindrical farm silo on ffness matrix for the elastic foundation governed by winkler's assumption. A complete computer programs have been developed in this paper can be applicable not only to the shell structures on elastic foundation but also to the arbitrary three dimensional structures. Assuming the small deflection theory, the membrane and plate bending behaviours of flat plate element can be assumed mutually uncoupled. In this case, the element has 5 degrees of freedom per node when defined in the local coordinate system. However, when the element properties are transformed to the global coordinates for assembly, the 6th degree of freedom should be considered. A problem arises in this procedure the resultant stiffness in the 6th degree of freedom at this node will be zero. But this singularity of the stiffness matrix can be eliminated easily by merely replacing the zero diagonal by dummy stiffness.

• Structural Engineering and Mechanics
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• 제22권1호
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• pp.71-83
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• 2006

This paper deals with the effects of various moisture environments on the structural behavior of concrete beams. The presented results were obtained within a large experimental program carried out at the Laboratoire Central des Ponts et Chauss$\acute{e}$es (LCPC), with Electricit$\acute{e}$ de France (EDF) as a partner. The aim of this paper is to point out and to quantify the strains resulting from unidirectional moisture conditions: a drying gradient applied during 14 months, followed by the re-wetting of the dried surface during 9 months. The effect of reinforcement on the shrinkage and on the deformation due to water absorption is pointed out. Moreover, a lot of tests on companion cylinders and prisms were carried out to determine the mechanical characteristics of the material and help checking analysis methods. The paper focuses on numerous measurements obtained during the 23 months on one plain concrete beam and one reinforced concrete beam: variation of water content, followed by precise weighing and gammadensitometry, relative humidity measurements, local and global deformations in the three directions and deflection of the beams. Thus, the effects of drying and water absorption on the behavior of concrete structures are documented and analyzed in comparison with existing representation of water diffusion.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.283-290
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• 2019

In global competition manufacturing companies have to produce modern, new constructions from advanced materials in order to increase competitiveness. The aim of my research was to develop a new composite cellular plate structure, which can be primarily used for structural elements of road, rail, water and air transport vehicles (e.g. vehicle bodies, ship floors). The new structure is novel and innovative, because all materials of the components of the newly developed structure are composites (laminated Carbon Fiber Reinforced Plastic (CFRP) deck plates with pultruded Glass Fiber Reinforced Plastic (GFRP) stiffeners), furthermore combines the characteristics of sandwich and cellular plate structures. The material of the structure is much more advantageous than traditional steel materials, due mainly to its low density, resulting in weight savings, causing lower fuel consumption and less environmental damage. In the study the optimal construction of a given geometry of a structural element of a road truck trailer body was defined by single- and multi-objective optimization (minimal cost and weight). During the single-objective optimization the Flexible Tolerance Optimization method, while during the multi-objective optimization the Particle Swarm Optimization method were used. Seven design constraints were considered: maximum deflection of the structure, buckling of the composite plates, buckling of the stiffeners, stress in the composite plates, stress in the stiffeners, eigenfrequency of the structure, size constraint for design variables. It was confirmed that the developed structure can be used principally as structural elements of transport vehicles and unit load devices (containers) and can be applied also in building construction.

• Steel and Composite Structures
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• 제42권6호
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• pp.765-777
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• 2022

Ultra high performance concrete (UHPC) can be used in the UHPC-steel composite structures especially for bridge structures to achieve high stiffness and high fatigue resistance with low self-weight. The structural performances of UHPC-steel composite slabs subjected to hogging moment have a significant influence on the global stiffness and durability of UHPC-steel composite structures. In order to study the structural behaviors of non-steam-cured UHPC-steel composite slabs subjected to negative moment, five composite slabs combined the thin UHPC layers to steel plates via shear stud connecters with the diameter of 16mm were fabricated and tested under negative moment. The test program aimed to investigate the effect of stud spacing and longitudinal reinforcement ratios on the failure mode, load-deflection behaviors, cracking patterns, bond-slips, and carrying capacities of composite slabs subjected to negative moment. In addition, direct tensile tests for the dog-bone UHPC specimens with longitudinal reinforcement bars were carried out to study the effect of reinforcement bars on the tensile strength of UHPC in the thin structure members. Based on the experimental results, analytical models were also developed to predict the cracking load and ultimate load of UHPC-steel composite slabs subjected to negative moment.

• 대한토목학회논문집
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• 제32권1A호
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• pp.19-30
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• 2012

최근 캠코더와 같은 영상 장비의 고성능화 및 대중화, 그리고 화상 처리(image procession) 기술의 발달 등으로 인하여 영상 기반의 구조물 동적변위 계측에 관한 연구가 활발하며, 이러한 연구개발의 결과로 관련 시스템의 사용성 및 정확도가 많이 개선되고 있다. 그러나 이러한 영상 기반 시스템의 경우 장비 측면에서 볼 때 영상 장비 자체의 진동에 의한 오차, 화상 처리 과정에서의 오차 등을 개선할 필요가 있으며, 또한 적용 측면에서 볼 때 교량의 수직 처짐이나 건축구조물의 수평변위 계측에 제한되어 있어 부유체의 파랑응답과 같은 3차원 운동을 하는 구조물에 대한 확장이 필요한 시점이다. 이 연구에서는 이러한 영상 기반 동적변위 계측방법을 3차원 문제에 적용하기 위하여 다중 표적(multiple target)을 사용한 방법을 제시하고, 또한 화상 처리 과정에서의 정량적 판단 기준을 제시함으로써 간접적으로 영상 기반 시스템의 계측 정확도를 평가하여, 영상 기반 방법에 의하여 계측된 동적변위 계측결과의 유효성을 판단할 수 있도록 하였다. 제안된 방법을 $50m{\times}30m{\times}5m$ 규모의 대형 부유체에 대한 실해역 파랑 응답 실험에 적용하여, 부유체의 동적변위를 계측하였으며, 그 결과를 기존의 RTK-GPS(Real Time Kinematics-Global Positioning System), MRU(Motion Reference Unit) 등의 장비를 이용한 계측결과와 비교함으로써 그 성능을 검증하였다.

• 패션비즈니스
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• 제24권5호
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• pp.35-51
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• 2020

To satisfy consumers' desire to enjoy their own individuality and cultural trends, the discovery of various materials and the expression of materials embodying their characteristics are increasingly important in the fashion jewelry industry. This study examines, paper mulberry fiber, a raw material of hanji that has been excavated as a new material for fashion jewelry, is durable as wall as, soft and easy to form, has a unique texture along with, excellent aesthetic quality, and expresses various colors, thereby differentiating itself from traditional fashion jewelry materials. The material itself also has symbolic significance as an approach to discovering new sustainable materials for fashion jewelry to ensure increased specificity of the product based on the premise of freedom of expression. The weight and optimal drying time of chicken fiber were derived for the study of fashion jewelry expression using the characteristics of paper mulberry fiber. The techniques of casting, deflection, packing and winding (winding beads with fibers and straps) were derived and four brooches were produced in total. This study is meaningful for the future of, the fashion jewelry industry as it presents the uses of new materials such as paper mulberry fiber to induce multidisciplinary consumption and to suggest a direction for the creation of new value-added products. Further, in order to expand the realm of fashion jewelry industry with our own competitive products that have secured our cultural identity and uniqueness in the global market, there must be continued follow-up research on mass production methods for industrialization.

• 한국항공우주학회지
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• 제36권3호
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• pp.229-237
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• 2008

본 연구에서는 항공기 날개를 설계하기 위하여 공기역학과 구조해석을 통합한 다분야 설계최적화(MDO) 프레임웍을 구성하였다. 파라미터 모델링 기법을 사용하여 최적화 전 과정을 자동화하였다. 공력해석은 Fluent를 사용하였으며 이를 위한 격자는 CATIA의 파라미터 모델과 Gridgen을 사용하여 자동으로 생성되도록 하였다. 유한요소해석을 위한 격자는 MSC.Patran의 PCL 기능을 사용한 파라미터 방법으로 자동으로 생성되도록 하였다. 공력하중은 volume spline method를 사용하여 구조하중으로 변환시켰다. 최적화 방법은 전역해를 구하기 유리한 반응표면법을 사용하였다. 최적화 문제로 목적 함수는 날개의 무게의 최소화, 제약조건은 양항비와 날개의 변위로 정하였다. 그리고 종횡비, 테이퍼 비 및 후퇴각을 설계변수로 정의하였다. 최적화 시험 결과는 본 MDO 프레임웍이 성공적으로 구성되었음을 보여주었다.