• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 1996년도 춘계학술대회논문집; 부산수산대학교, 10 May 1996
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• pp.335-341
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• 1996

유한차분 감소를 이용한 감도해석 및 구조변경 프로그램을 개발하고 수치해석을 수행하여 다음과 같은 결론을 얻었다. 1) 유한요소 모델로부터 얻은 유한차분감도를 이용한 결과가 미분을 이용한 감도해석법의 결과에 비해 큰 차이없이 타당한 결과를 제시하여 주는 것을 확인하였다. 2) 복잡한 판구조물의 형상을 등가의 동특성을 갖는 보를 이용하여 모델링하고, 보의 단면치수를 설계변수로하여, 구조변경을 수행함으로써 효율적인 해석을 수행하였다. 3) 혀상이 복잡한 판 구조물의 형상 및 치수등 비선형적인 요소의 변경으로 인한 구조변경시 유한차분 감도 해석법을 이용한 구조변경이 좋은 결과를 나타내는 것을 확인하였고, 이로써 유한차분을 이용한 감도해석법이 형상최적화(shape optimization)에 적합한 방법임을 알 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• 제5권6호
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• pp.21-27
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• 2001

In this paper, a nonlinear finite element procedure is presented for the dynamic analysis of reinforced concrete shells. A computer program, named RCAHEST(reinforced concrete analysis in higher evaluation system technology), for the analysis of reinforced concrete structures was used. A 4-node flat shell element will drilling rotational stiffness is used for spatial discretization. The layered approach is used to discretize behavior of concrete and reinforcement through the thickness. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. Solution of the equations of motion is obtained by numerical integration using Hilber-Hughes-Taylor(HHT) algorithm. The proposed numerical method for the nonlinear dynamic analysis of reinforced concrete shells is verified by comparison with reliable analytical results.

• Magazine of the Korea Concrete Institute
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• 제1권2호
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• pp.121-132
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• 1989

유한요소법을 바탕으로 한 프리스트레스트 콘크리트 평면 보-기둥 구조의 후좌굴 거동에 대한 수직해석법을 제시하였다. 콘크리트의 균열, 변형연화 및 PS강재의 항복과 같은 재료 비선형성을 고려하였다. 좌굴 거동 연구에 필수적 요소인 기하학적 비선형성을 Updated Lagraugian Formulation에 의하여고려하였다. 현재의 재료성질 및 변형상태에 부합하는 단분형 평형방정식을 수립하고 이것을 불평형 가중보정에 의한 Newton-Raphson 반복법으로 푼다. 좌굴후 발생하는 하중변형 곡선의 하련부는 비선형 평형 방정식의 해법중 일반적으로 많이 사용되는 가중 단분법이 아니라 변위단분법을 사용함으로써 올바르게 추적한다. 요소내의 재료성질변화는 층적분법에 의하여 고려한다. 본 논문에서는 콘크리트 균열에 의한 중립축이동의 영향을 정확히 고려하기 위하여 추가적으로 축방향변위에 대한 내부자유도를 설정하였다. 본 논문에서 제안하는 방법의 정당성과 응용성을 나타내 보일 수 있는 수직해석 예제를 제시하였다.

• Journal of the Korea institute for structural maintenance and inspection
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• 제9권4호
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• pp.159-168
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• 2005

This study carries out a finite difference nonlinear analysis of anisotropic advanced composite plate structures with various layer sequences. In the numerical analysis of various mechanical problems involving complex partial differential equations, the finite difference method (FDM) developed in this study has an advantage over the finite element method in its ability to avoid mesh generation and numerical integration. Many studies in FDM have been made on clamped or simple boundary conditions using merely an energy approach. These approaches cannot be satisfied, however, with pivotal points along the free boundary. Therefore, this study addresses the nonlinear problem of anisotropic plates by adopting a finite difference modeling elimination of pivotal difference points in the case of a free boundary condition. Complex nonlinear behaviors of composite plate structures for various parameters, especially for layer sequences, are analyzed using the proposed approach.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제12권3호
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• pp.363-370
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• 1999

This study presented an modeling method for the connections in mixed structure with reinforced concrete columns and steel beam using finite element method. The contacting surfaces between concrete and steel are modeled using master-slave contact algorithm and the incompatible mode elements were used in the steel tube subjected to bending. The characteristics of mixed structure was that diaphragm was used for transferring force from beam to column. The three dimensional nonlinear analysis was performed and the analytical results compared with experimental results in order to prove modeling method.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 한국전산구조공학회 2010년도 정기 학술대회
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• pp.68-71
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• 2010

극심한 고온 및 고압 환경에 노출되기 쉬운 항공우주 구조물에서 발생하는 기계적 삭마 현상을 해석하기 위하여 영역/경계 분할법을 적용한 삭마 해석 모델을 제안하였다. 영역 및 경계는 상변화 현상에 의한 비선형 거동을 하는 삭마 부영역과 선형 거동을 하는 선형 열탄성 부영역, 공유면, 경계 공유면으로 분할하였다. 삭마 재료 내부의 열분해 반응은 엔탈피 방법을 이용하였으며, 표면 침식 반응은 공기역학적 전단 응력과 삭마 재료의 전단 강도를 기반으로 매칭 기법을 이용하였다. 화학적 및 열적 삭마는 고려하지 않았으며, 간단한 수치 해석을 통해서 기본적인 기계적 삭마 특성을 분석하였다.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 한국해안해양공학회 2002년도 한국해안해양공학발표논문집 Proceedings of Coastal and Ocean Engineering in Korea
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• pp.298-301
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• 2002

경계요소법은 Laplace 방정식을 지배방정식으로 하는 지하수 흐름이나 해안공학 문제의 해석에 있어 매우 정확한 해를 제공하는 수치 기법이다. 특히, 경계요소법은 유한차분법이나 유한요소법과 같은 다른 수치기법과 달리 계산시간이나 기억용량의 절감 등에서 매우 효율적이다. 또한, 임의의 형태를 갖는 지형에도 큰 문제없이 쉽게 적용할 수 있고 요소의 크기를 자유롭게 조절할 수 있는 장점이 있다. (중략)

• Journal of Korean Association for Spatial Structures
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• 제8권1호
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• pp.41-48
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• 2008

Spatial structure is an appropriate shape that resists external force only with in-plane forte by reducing the influence of bending moment, and it maximizes the effectiveness of structure system. the spatial structure should be analyzed by nonlinear analysis regardless static and dynamic analysis because it accompanys large deflection for member. To analyze the spatial structure geometrical and material nonlinearity should be considered in the analysis. In this paper, a geometrically nonlinear finite element model for plane truss structures is developed, and material nonlinearity is also included in the analysis. Arc-length method is used to solve the nonlinear finite element model. It is found that the present analysis predicts accurate nonlinear behavior of plane truss.

• Journal of Korean Society of Coastal and Ocean Engineers
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• 제3권3호
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• pp.176-183
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• 1991

In this paper. boundary element method is applied to the analysis of nonlinear free surface wave. A particular concern is given to the treatment of the open boundaries at the in-flow boundary and out-flow boundary, which uses the mass-flux and energy-flux considering the continuity of fluid. By assuming the fluid to be inviscid and incompressible and the flow to be irrotational. the problem is formulated mathematically as a two-dimentional nonlinear problem in terms of a velocity potential. The equation(Laplace equation) and the boundary conditions are transformed into two boundary integral equations. Due to the nonlinearity of the problem. the incremental method is used for the numerical analysis. Numerical results obtained by the present boundary element method are compared with those obtained by the finite element method and also with experimental values.

• Transactions of the Korean Society of Mechanical Engineers
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• 제16권8호
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• pp.1468-1484
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• 1992

In the present paper forward projection is proposed as a new approach to determine the preform shape in rib-web type forging. In the forward projection technique an optimal billet is determined by applying some mathematical relationship between geometrical trials in the initial billet shape and the final products. In forward projection a volume difference between the desired product shape and the final computed shape obtained by the rigid-plastic finite element method is used as a measure of incomplete filling of working material in the die. At first linear inter-/extrapolation is employed to find a proper trial shape for the initial billet and the method is successfully applied to some cases of different aspect ratios of the initial billet. However, when the initial guesses are not sufficiently near the optimal value linear inter-/extrapolation does not render complete die filling. For more general application, a fuzzy system is used in the forward projection technique in order to determine the initial billet shape for rib-web type forging. It has been thus shown that the fuzzy system is more reliable for the preform design in the rib-web type forging process.