• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.203-204
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• 2009

The maglev guiderail systems, which receive directly the live load of maglev train and transfer the load to the main girder, is a important constituent in guideway system. As a process of development of maglev guideway girder adopting the precast decks, static and fatigue loading tests of the connections systems of precast deck and guiderail have been accomplished. In this stude, the structural characteristics of precast deck-guiderail connection systems are being evaluated by performing a detailed finite element analyses.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.61-71
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• 2007

Navier's and Finite element solutions based on the first-order shear deformation theory are presented for the analysis of through-thickness functionally graded plates and shells. The functionally graded materials are considered: a sigmoid function is utilized for the mechanical properties through the thickness of the isotropic structure which varies smoothly through the plate and shell thickness. The formulation of a nonlinear 9-node Element-based Lagrangian shell element is presented for the geometrically nonlinear analysis. Natural-coordinate-based strains are used in present shell element. Numerical results of the linear and nonlinear analysis are presented to show the effect of the different top/bottom elastic modulus, loading conditions, aspect ratios and side-to-thickness ratios on the mechanical behaviors. Besides, the result according to the variation of the power-law index of isotropic functionally graded structures is investigated.

• Computational Structural Engineering
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• v.11 no.4
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• pp.155-168
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• 1998

보강된 판 및 쉘구조의 안정성 및 후좌굴을 포함하는 기하학적 비선형 해석을 수행하기 위하여, total Lagrangian formulation에 근거한 연속체의 증분평형방정식으로부터 변형된 쉘요소인 유한요소이론을 제시하였다. 쉘구조의 곡률이 불연속적으로 변하거나 쉘부재들이 유한한 각도로 만나는 보강된 판 및 쉘구조의 비선형 해석이 가능하도록 주부재와 보강재 간의 연결점에 대한 일반적인 변환관계를 제시하였으며 좌굴해석 및 기하학적 비선형해석의 경우에 해의 정확성 및 수렴성을 개선시키기 위하여 접선강도행렬 산정시 회전각의 2차항을 포함시켰다. 또한, shear locking 현상을 극복하기 위하여 감차적분을 적용하였고 쉘구조의 좌굴해석에서는 power method를 적용하여 해석의 효율을 높였으며, 후좌굴해석에서는 변위 및 하중증분법을 적절히 결합시켜 보강된 쉘구조의 후좌굴 거동추적이 용이하였다. 또한, 입력자료를 손쉽게 준비하고 좌굴모드 및 후좌굴거동을 효율적으로 분석하기 위하여 전, 후 처리 프로그램을 개발하였고 다양한 해석예제를 통하여 다른 문헌의 해석결과를 비교함으로써 본 연구에서 개발된 유한요소 해석프로그램의 타당성 및 정확성을 입증하였다.

• Computational Structural Engineering
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• v.7 no.4
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• pp.85-101
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• 1994

A family of variational principles governing the dynamics of laminated plate has been derived using a variationally consistent shear deformable discrete laminated plate theory with particular reference to finite element procedures. The theoretical basis for the derivation is Sandhu's generalized procedure for the variational formulation of linear coupled boundary value problem. As the bilinear mapping to write the operator matrix of the field equations in self-adjoint form, convolution product was employed. Boundary conditions, initial conditions and probable internal discontinuity were explicitly included in the governing functionals. Some interesting extensions and specializations of the general variational principle were presented, which can provide many different finite element formulations for the problem.

• Computational Structural Engineering
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• v.10 no.2
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• pp.243-254
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• 1997

When dynamic loads such as mechanical load, wind load, and seismic load, which causing a vibration, acts on the body of the 3-D framework resting on soil foundation, it is required to consider the dynamic behavior of soil-space framework interation system. Thus, this study presents the 3-dimensional soil-interaction system analyzed by finite element method using 4-node plate elements with flexibility, 2-node beam elements, and 8-node brick elements for the purpose of idealizing an actual structure into a geometric shape. The objective of this study is the formulation of the equation for a dynamic motion and the development of the finite element program which can analyze the dynamic behavior of soil-space framework interaction system.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.100-115
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• 1993

In this paper, the extent of use of three kinds of the existing idealized structural units, namely the idealized beam-column unit, the idealized unstiffened plate unit and the idealized stiffened plate unit, is expanded to deal with the excessive tension-deformation effects, in which a simplified mechanical model for the stress-strain relation of steel members under tensile load is suggested. The 1/3-scale hull model for a leander class frigate under sagging moment tested by Dow is analyzed, and it is shown that the excessive tension-de-formation is a significant factor affecting the progressive collapse behavior, particularly in the post-collapse range.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.08a
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• pp.123-127
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• 2008

본 논문에서는 2006년 11월 신 차량 번호판 등장 이후 꾸준히 증가하고 있는 흰색 번호판 차량에서 흰색 번호판 추출에 관한 연구를 수행한다. 먼저 입력된 차랑 영상을 그레이 레벨로 변환 후, 국부적으로 밝기 보정을 수행하고, Otsu 판별식을 이용해 이진화 한다. 이진화 된 차량 영상에서 번호판 특성을 이용하며 라인 구조요소에 의한 침식연산과 채움 연산을 적용한다. 이후, 수평 투영으로 명암 변화가 심한 후보 영역을 찾고, 다시 수직 투영을 하여 일정구간에서 흰색의 값이 가장 많이 나타나는 구간을 찾는다. 마지막으로 번호판의 형태학적 특징을 이용해 번호판을 추출한다. 제안한 알고리즘을 적용한 결과 번호판 크기가 일정하지 않거나 불규칙한 조명 상태에서도 번호판 추출이 가능하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.519-525
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• 2009

In this study a cohesive zone model was used to simulate the delamination phenomena which occurs by a successive crack initiation and propagation in composite laminates. The cohesive zone model was incorporated to the classical finite element method via cohesive element formulation and then implemented into the user-subroutine UEL of a commercial finite element program Abaqus. To validate the formulation and implementation of the cohesive element the finite element results were compared with the experimental data of double cantilever beam and end notched flexure tests. The numerical results well agree with the experimental load-displacement curves. Also the effect of the elastic stiffness and the size of the cohesive element on the global load-displacement curves were studied numerically. To minimize the mesh-dependency of the crack propagation path and eliminate the zig-zag patterns in the load-displacement curve, cohesive elements should be refined at the crack-tip.

• Journal of Korean Association for Spatial Structures
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• v.11 no.3
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• pp.77-83
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• 2011

Laminated composite plates have shown their superiority over metals in applications requiring high specific strength, high specific modulus, and so on. Therefore, they have used in various industry. However, they have poor resistance to impact compared to typical metal materials. To resolve this problem by many researchers for a variety of studies have been attempted. This study investigates characteristic of impact behavior of laminated composite plates due to initial stress. Using finite element program which involved the indentation law, we investigate characteristic of impact behavior of laminated composite plates due to initial stress.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.621-628
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• 2004

This paper introduces a new theory, that in a stiffened plate, a steel stiffener could be substituted a composite material in order to prevent from buckling. Changing a steel stiffener into a composite material would not only preclude welding, but could also prevent damage to the material due to fatigue and corrosion.A composite material is assumed to adhere to a steel plate, and is never separated from the plate until the steel plate reaches buckling.Such plate has variable shapes, with different lengths and widths, and also shows an anisotropic material property. LUSAS, a commercial finite element analysis package, was used in the buckling analysis.This paper investigated buckling behavior in anisotropic composite plates with variable parameters.