• 한국공간구조학회논문집
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• 제4권3호
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• pp.103-109
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• 2004

본 논문은 조합하중을 받는 공간구조물의 안정경계를 파악하는 것이다. 구조물에 작용하는 독립된 여러 가지 하중벡터는 기본이 되는 하중 모드와 하중매개 변수를 이용하여 나타내고, 독립된 하중 매개변수에는 비례관계를 설정함으로서 하나의 하중변수에 의해 하중을 부여한다. 구조물의 좌굴하중 즉 임계점은 평형조건이 불안정이 되는 극한점과 분기점으로 분류되고, 가장 낮은 하중이 좌굴하중으로 정의된다. 본 논문에서는 기하학적 비선형 문제를 해석하기 위한 수치해석법으로는 호장법과 뉴턴-랩슨법을 이용하였으며, 본 해석을 통하여 안정경계를 파악함은 물론 좌굴모드 및 좌굴하중을 명확히 규명하였다.

• Steel and Composite Structures
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• 제1권1호
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• pp.75-96
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• 2001

Actual buckling curves are always characterised by the erosion of ideal buckling curves. In case of compact sections this erosion is due to the imperfections, while for thin-walled members, a supplementary erosion is induced by the phenomenon of coupled instabilities. The ECBL approach- Erosion of Critical Bifurcation Load - represents a practical and convenient tool to characterise the instability behaviour of thin-walled members. The present state-of-art paper describes the theoretical background of this method and the applications to cold-formed steel sections in compression and bending. Special attention is paid to the evaluation methods of erosion coefficient and to their validation. The ECBL approach can be also used to the plastic-elastic interactive buckling of thin-walled members, and the paper provides significant results on this line.

• Structural Engineering and Mechanics
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• 제5권6호
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• pp.715-728
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• 1997

The aim of this paper is to investigate the secondary buckling behaviour and mode-coupling of spherical caps under uniformly external pressure. The analysis makes use of a rotational finite shell element on the basis of strain-displacement relations according to Koiter's shell theory (Small Finite Deflections). The post-buckling behaviours after a bifurcation point are analyzed precisely by considering multi-mode coupling between several higher order harmonic wave numbers: and on the way of post-buckling path the positive definiteness of incremental stiffness matrix of uncoupled modes is examined step by step. The secondary buckling point that has zero eigen-value of incremental stiffness matrix and the corresponding secondary mode are obtained, moreover, the secondary post-buckling path is traced.

• 한국전산구조공학회논문집
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• 제12권3호
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• pp.407-415
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• 1999

쉘형 구조물의 불안정 현상은 크게 뜀좌굴과 분기좌굴로 분류할 수 있다. 이들은 구조물의 형상특성, 특히 형상 초기불완전에 대해 매우 민감하게 반응한다. 본 연구에서는, 형상 초기불완전을 가진 쉘형 구조물의 불안정 거동을 파악하기 위해 양단이 힌지로 고정된 얕은 정현형 아치의 평형경로를 조사한다. 비선형 방정식을 얻기 위해 Galerkin법을 이용하였으며, 증분형 방정식으로의 변환은 섭동법을 이용하였다.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3441-3453
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• 1996

A finite element anlaysis is performed for large deformations of a felxible beam. The total Lagrangian formulation for a general large deformation, which involves finite rotations, is chosen and the exponential map is used to treat finite rotations from the Eulerian point of view. The finite elements results are confirmed for several cases of deformations through comparison to a first order elasticity solution obtained by numerical integration, and the agreement between the two is found to be excellent. For lateral buckling, the point of vanishing determinant of the resulting unsymmetric tangent stiffness is traced to examine its relationship to bifurcation points. It is found that the points of vanishing determinant is not corresponding to bifurcation points for large deformation in general, which suggests that the present unsymmetric tangent stiffness is not an exact first derivative of internal forces with respect to displacement.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.9-18
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• 1996

The primary objective of this paper is to grasp many characteristics of buckling behavior of latticed spherical domes under various conditions. The Arc-Length Method proposed by E.Riks is used for the computation and evaluation of geometrically nonlinear fundamental equilibrium paths and bifurcation points. And the direction of the path after the bifurcation point is decided by means of Hosono's concept. Three different nonlinear stiffness matrices of the Slope-Deflection Method are derived for the system with rigid nodes and results of the numerical analysis are examined in regard in geometrical parameters such as slenderness ratio, half-open angle, boundary conditions, and various loading types. But in case of analytical model 2 (rigid node), the post-buckling path could not be surveyed because of Newton-Raphson iteration process being diversed on the critical point since many eigenvalues become zero simultaneously.

• 한국공간구조학회논문집
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• 제13권1호
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• pp.87-96
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• 2013

This study investigated characteristics of buckling load and effective buckling length by member rigidity of dome-typed space frame which was sensitive to initial conditions. A critical point and a buckling load were computed by analyzing the eigenvalues and determinants of the tangential stiffness matrix. The hexagonal pyramid model and star dome were selected for the case study in order to examine the nodal buckling and member buckling in accordance with member rigidity. From the numerical results, an effective buckling length factor of adopted models was bigger than that of Euler buckling for the case of fixed boundary. These numerical models indicated that the influence of nodal buckling was greater than that of member buckling as member rigidity was higher. Besides, there was a tendency that the bifurcation appeared on the equilibrium path before limit point in the member buckling model.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 가을 학술발표회 논문집
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• pp.16-21
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• 1990

Recently, the finite element method has been sucessfully extended to treat the rather couplet phenomena such as nonlinear buckling problems which are of considerable practical interest. In this study, a finite element program to evaluate the elasto-plastic buckling stress is developed. The Stowell's deformation theory for the plastic buckling of flat plates, which is in good agreement with experimental results, is used to evaluate bending stiffness matrix. A bifurcation analysis is performed to compute the elasto-plastic buckling stress. The subspace iteration method is employed to find the eigenvalues. The results are compared with corresponding enact solutions to the governing equations presented by Stowell and also with experimental data due to Pride. The developed program Is applied to obtain elastic and elasto-plastic buckling stresses for various loafing cases. The effect of different plate aspect ratio is also investigated.

• 한국강구조학회 논문집
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• 제17권6호통권79호
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• pp.707-715
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• 2005

파형강판은 파형 형상으로 가공된 강판으로 높은 면내, 면외 방향의 강성을 갖으며, 건물, 교량 등으로 적용도가 높아지고 있다. 파형강판을 플레이트 거더나 프리스트레스트 박스거더교의 복부판으로 적용하면, 파형강판의 아코디언 효과에 의해 플랜지가 휨응력을 복부판이 전단응력을 대부분 지지하는 효율적인 구조를 얻을 수 있다. 전단응력을 받는 파형 강판은 전체좌굴, 국부좌굴 및 연성좌굴에 의해 내하력을 상실할 수 있다. 세 가지 좌굴 모드 중 연성 좌굴에 대한 명확한 분석은 거의 이루어지지 않았고 보수적인 강도 예측을 위한 강도 감소식이 사용되고 있다. 따라서 본 연구에서는 연성 좌굴 거동에 미치는 기하학적인 인자들의 영향을 파악하기 위하여 유한요소해석법을 이용한 좌굴해석이 수행되었다. 해석 결과는 연성 좌굴은 패널의 세장비와 북부판 높이 두께비의 복합변수에 의존하는 것으로 나타났다.

• 대한기계학회논문집A
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• 제22권4호
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• pp.887-894
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• 1998

This paper presents the results of analytical invesstigation of the buckling behavior of thin-walled box-section column. Throughout this investigation, the single curve for finding the buckling stress at each effective slenderness ratio is derived by modification of the Rankine's formula. The applicable formula in the small slederness region is derived by considering the inelastic behavior of material. Additionally, the bifurcation criterion(slenderness ratio) which can distinguish between the local and overall buckling mode shapes is suggested by equating the local and overall buckling stresses. The overall buckling formula is closely concurrent with the experiments for the rectangular tubes.