• 한국전산구조공학회논문집
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• 제21권2호
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• pp.153-160
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• 2008

본 연구에서는 완화된 평형조건을 만족하는 응력함수를 가지는 새로운 3절점 혼합요소를 제안하였다. 전단변형률을 고려한 본 요소는 Hellinger-Reissner 변분이론에 바탕하여 유한요소정식화를 수행하였다. 응력함수는 강체변형모드를 제거하고, 장일치(field consistency) 개념을 이용하여 곡선보의 극한거동에서 가성구속조건들을 억제할 수 있도록 선정하였다. 또한, 3절점 곡선보의 혼합정식화에서 강체변형모드를 제거하면서 동시에 평형방정식을 완전하게 만족하는 응력함수와 응력매개변수를 선정하는 것은 매우 어렵기 때문에 완화된 평형조건을 만족할 수 있는 응력함수를 도입하였다. 해석결과를 통하여, 제안된 3절점 혼합 곡선보요소가 곡선보의 해석에서 세장비와 곡률에 상관없이 매우 빠른 수렴성과 안정적인 거동을 나타냄을 확인할 수 있었으며, 응력분포 계산에 있어서도 기존 혼합요소보다 뛰어난 성능을 보여주었다.

• Structural Engineering and Mechanics
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• 제19권2호
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• pp.199-215
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• 2005

An assumed stress quadrilateral thin/moderately thick plate element HQP4 based on the Mindlin/Reissner plate theory is proposed. The formulation is based on Hellinger-Reissner variational principle. Static and free vibration analyses of plates are carried out. Numerical examples are presented to show that the validity and efficiency of the present element for static and free vibration analysis of plates. Satisfactory accuracy for thin and moderately thick plates is obtained and it is free from shear locking for thin plate analysis.

• Steel and Composite Structures
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• 제11권5호
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• pp.359-374
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• 2011

In this paper, the influence of fibre orientation and aspect ratio on stability analysis of simply supported skew plates subjected to in plane loading is studied by using a four noded hybrid plate finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. Some numerical problems are solved and the effects of skew angle, aspect ratio, fibre orientation and loading type on the critical buckling loads are highlighted.

• Structural Engineering and Mechanics
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• 제21권5호
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• pp.571-590
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• 2005

An 8 node assumed stress hexahedral element with rotational degrees of freedom is proposed for static and free vibration analyses. The element formulation is based directly on an 8-node element. This direct formulation requires fewer computations than a similar element that is derived from an internal 20-node element in which the midside degrees of freedom are eliminated by expressing them in terms of displacements and rotations at corner nodes. The formulation is based on Hellinger-Reissner variational principle. Numerical examples are presented to show the validity and efficiency of the present element for static and free vibration analysis.

• Structural Engineering and Mechanics
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• 제63권2호
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• pp.225-235
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• 2017

In this paper a vibration study on orthotropic elliptic paraboloid shells with openings is carried out by using a hybrid stress finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. Natural frequencies of orthotropic elliptic paraboloid shells with and without openings are presented. The influence of aspect ratio, height ratio, opening ratio and material angle on the frequencies and mode shapes are investigated.

• Steel and Composite Structures
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• 제23권6호
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• pp.737-746
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• 2017

In this paper the influence of aspect ratio, height ratio and material angle on static and free vibration behaviour of orthotropic elliptic paraboloid shells is studied by using a four-node hybrid stress finite element. The formulation of the element is based on Hellinger-Reissner variational principle. The element is developed by combining a hybrid plane stress element and a hybrid plate element. A parametric study is carried out for static and free vibration response of orthotropic elliptic paraboloid shells with respect to displacements, internal forces, fundamental frequencies and mode shapes by varying the aspect and height ratios, and material angle.

• 동력기계공학회지
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• 제10권4호
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• pp.83-89
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• 2006

Curved beams are more efficient in transfer of loads than straight beams because the transfer is effected by bending, shear and membrane action. The finite element method is a versatile method for solving structural mechanics problems and curved beam problems have been solved using this method by many author. In this study, a new three-noded hybrid-mixed curved beam element is proposed to investigate the in-plane flexural vibration behavior of arches depending on the curvature, aspect ratio and boundary conditions, etc. The proposed element including the effect of shear deformation is based on the Hellinger-Reissner variational principle, and employs the quadratic displacement functions and consistent linear stress functions. The stress parameters are then eliminated from the stationary condition of the variational principle so that the standard stiffness equations are obtained. Several numerical examples confirm the accuracy of the proposed finite element and also show the dynamic behavior of arches with various shapes.

• 대한기계학회논문집
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• 제18권11호
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• pp.2871-2882
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• 1994

Two kinds of 4-node plane stress/strain finite elements are presented in this work. They are derived from the modified Hellinger-Reissner variational principle so as to employ the internal incompatible displacement and independent stress fields, or the incompatible displacement and strain fields. The introduced incompatible functions are selected to satisfy the constant strain condition. The elements are evaluated on several problems of bending and material incompressibility with regular and distorted elements. The results show that the new elements perform excellently in the calculation of deformation and stresses.

• 대한기계학회논문집A
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• 제20권7호
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• pp.2078-2086
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• 1996

This paper introduces two three-dimensional eight-node hexagonal elements obtained by using multivariable variational mehtod. Both of them are based on the modified hellinger-reissner principle to employ incompatible displacements and assumed stresses of assumed strains. The internal functions of element are introduced to as element formulation through two different methods : the first one uses the functions determined directly from the element boundary condition of the incompatible displacements ; while the second, being a kind of B-bar mehtod, employs the modification technique of strain-displacement matrix to pass the patch test. The elements are evaluated on the selective problems of bending and material incompressibility with regular and distorted meshes. The results show that the new elements perform with good accuracy in both of deformation and stress calculation and they are insensitive to distorted geometry of element.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.89-92
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• 2000

In this paper, an effective procedure is presented for the local recovery of displacements and stresses in multilayered composite panels, which incorporate the local refinement using mesh superposition. The mesh superposition method is used to refine the global coarse mesh by superimposing refined mesh to the localized zone of interest without transition zones. The finite element model used is a solid element based on the Hellinger-Reissner variational principle. The a posteriori computation of the through-the-thickness distributions of displacements and stresses is achieved using a predictor-corrector procedure. The procedure utilizes the superconvergent stresses and nodal displacements of the finite element patch. The element patch is generated by locally superimposing a refined local mesh to the coarse global mesh.