• 한국전산구조공학회논문집
• /
• 제18권2호
• /
• pp.159-168
• /
• 2005

탄성좌굴 고유치해석을 이용한 유효좌굴길이 산정법과 2차 탄성해석기법을 이용하여 축력과 휨모멘트를 받는 강절프레임의 보-기둥부재에 대하여 개선된 좌굴설계법을 제안한다. 이를 위하여 먼저 안정함수를 이용하여 보-기둥요소의 접선강성행렬을 유도하고, 탄성좌굴 고유치해석을 이용한 유효좌굴길이 산정법을 고찰한다. 또한 강절프레임에 대하여 소위 P-Delta 효과를 고려하는 2차 해석법을 제시한다. 해석예제를 통하여 먼저 2차 탄성해석과 기하학적 비선형해석에 의한 결과를 비교하여 2차 해석의 정확성을 검증하고, 강절프레임에 대한 기존의 설계법과 본 연구의 개선된 좌굴설계법에 대한 수치결과를 비교, 검토를 행한다.

• Steel and Composite Structures
• /
• 제45권4호
• /
• pp.547-554
• /
• 2022

This paper studies the static stability of an axially graded column with the power-law gradient varying along the axial direction. For a nonhomogeneous column with one end linked to a rotational spring and loaded by a compressive force, respectively, an Euler problem is analyzed by solving a boundary value problem of an ordinary differential equation with varying coefficients. Buckling loads through the characteristic equation with the aid of the Bessel functions are exactly given. An alternative way to approximately determine buckling loads through the integral equation method is also presented. By comparing approximate buckling loads with the exact ones, the approximate solution is simple in form and enough accurate for varying power-law gradients. The influences of the gradient index and the rotational spring stiffness on the critical forces are elucidated. The critical force and mode shapes at buckling are presented in graph. The critical force given here may be used as a benchmark to check the accuracy and effectiveness of numerical solutions. The approximate solution provides a feasible approach to calculating the buckling loads and to assessing the loss of stability of columns in engineering.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
• /
• pp.83-88
• /
• 1994

Recently, the equipments of the structure are increasing remarkably. It is very important to evaluate the stability of the domes under concentrated loading such as a large-scale illuminating, visional, and sound equipment. The paper is aimed at investigating the buckling characteristics of single-layer latticed domes with triangular network under the uniformly distributed vertical-loading and the partially concentrated equipment-loading. The results show that the effects of the equipment-loading on the buckling strength is much more sensitive in domes of overall buckling than in domes of member buckling.

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

• 한국컴퓨터그래픽스학회논문지
• /
• 제8권1호
• /
• pp.37-45
• /
• 2002

본 논문은 매우 안정적이며 동시에 사실적인 직물 시뮬레이션 기법을 제안한다. 제안된 방법을 통해 안정성을 향상시킴으로써 고정된 큰 시간 간격을 사용할 수 있게 되었고, 따라서 복잡한 옷감의 변형 및 움직임을 효율적으로 시뮬레이션 할 수 있었다. 또한 제안된 방법은 직물의 가장 중요한 특성중의 하나인 주름 현상을 자연스럽게 표현한다. 안정성과 사실성에서 동시에 큰 향상을 가져올 수 있었던 것은, 수치적 안정성 외에 옷감의 좌굴 후 거동시의 불안정성을 극복함으로써 가능했다. 좌굴에 의한 불안정성은 직물의 구조적 불안정성으로부터 기인하며 단순히 암시적 시적분 방법을 사용함으로써 해결되지 않는다. 그러한 불안정성은 감쇠력을 더하여 안정성을 회복할 수 있으나 직물의 움직임을 둔화 시켜 사실적인 움직임을 얻을 수 없게 한다. 본 논문에서는 즉좌굴(immediate buckling) 가정에 기반 한 새로운 직물의 좌굴 모형을 제시한다. 즉좌굴 가정은 직물이 좌굴되는 순간 안정한 상태로 곧바로 변형되는 것을 의미하며, 이러한 가정을 통해 가상적인 감쇠력을 더하지 않고도 안정적으로 직물을 시뮬레이션 할 수 있다. 결과적으로 즉좌굴 모델은 직물의 고유한 좌굴 현상을 적절히 모델링하여 안정성을 향상시킬 뿐 아니라 외부 힘에 민감하게 반응하는 직물의 움직임을 사실적으로 생성할 수 있도록 한다.

• Structural Engineering and Mechanics
• /
• 제16권5호
• /
• pp.533-556
• /
• 2003

The flutter and buckling analysis of a beam structure subjected to a static follower force is completely studied in the paper. The beam is fixed in the transverse direction and constrained by a rotational spring at one end, and by a translational spring and a rotational spring at the other end. The co-existence of flutter and buckling in this beam due to the presence of the follower force is an interesting and important phenomenon. The results from this theoretical analysis will be useful for the stability design of structures in engineering applications, such as the potential of flutter control of aircrafts by smart materials. The transition-curve surface for differentiating the two distinct instability regions of the beam is first obtained with respect to the variations of the stiffness of the springs at the two ends. Second, the capacity of the follower force is derived for flutter and buckling of the beam as a function of the stiffness of the springs by observing the variation of the first two frequencies obtained from dynamic analysis of the beam. The research in the paper may be used as a benchmark for the flutter and buckling analysis of beams.

• Smart Structures and Systems
• /
• 제18권1호
• /
• pp.155-181
• /
• 2016

In the present paper we discuss the stability and the post-buckling behaviour of thin piezoelastic plates. The first part of the paper is concerned with the modelling of such plates. We discuss the constitutive modelling, starting with the three-dimensional constitutive relations within Voigt's linearized theory of piezoelasticity. Assuming a plane state of stress and a linear distribution of the strains with respect to the thickness of the thin plate, two-dimensional constitutive relations are obtained. The specific form of the linear thickness distribution of the strain is first derived within a fully geometrically nonlinear formulation, for which a Finite Element implementation is introduced. Then, a simplified theory based on the von Karman and Tsien kinematic assumption and the Berger approximation is introduced for simply supported plates with polygonal planform. The governing equations of this theory are solved using a Galerkin procedure and cast into a non-dimensional formulation. In the second part of the paper we discuss the stability and the post-buckling behaviour for single term and multi term solutions of the non-dimensional equations. Finally, numerical results are presented using the Finite Element implementation for the fully geometrically nonlinear theory. The results from the simplified von Karman and Tsien theory are then verified by a comparison with the numerical solutions.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.223-227
• /
• 2004

The pultruded structural shapes are usually composed of thin-walled plate elements. Because the composite material has relatively low elastic moduli, the design of pultruded compression members may not be governed by the material strength limit state but by the stability limit state such as the local buckling or the global buckling. Therefore, the stability limit state must be checked to design pultruded columns. In this research, the local buckling analysis of pultruded I-shape column was conducted for various composite materials using the closed-form solution. To establish the design guidelines for the local buckling of pultruded I-shape compression members, the simplified form of equation to find the local buckling coefficient of pultruded I-shape column was proposed as a function of mechanical properties and the width ratio of plate components using the results obtainde by the closed-form solution. In order to verify the validity of proposed solution, the results obtained by the proposed approximate solution were compared with those of the closed-form solution and the experimental results.

• 한국정밀공학회지
• /
• 제16권11호
• /
• pp.191-196
• /
• 1999

This stability of a plate structure is very crucial problem which results in wrinkle and bucking. In this study, the effect of the pattern of spot-welding points of the two rectangular plates on the compressive buckling load is studied with respect to the thickness, aspect ratio of plates, number of welding spots. buckling coefficient of the plate not welded was compared with that of two plates with various thickness to extract the effect of thickness. The effect of number of welding spots are studied in tow directions, longitudinal and transverse directions. The conclusions obtained were that the reinforcement effect was maximized when the aspect ratio was close to 1.25 and that the effect of number of welding spots in transverse direction was large than that in longitudinal direction.

• Structural Engineering and Mechanics
• /
• 제85권6호
• /
• pp.825-835
• /
• 2023

The effective buckling length factor is an important parameter in the elastic buckling analysis of steel structures. The present article aims at developing a new method that allows the determination of the buckling factor values for frames. The novelty of the method is that it considers the interaction between the bracing and the elastic supports for asymmetrical frames in particular. The approach consists in isolating a critical column within the frame and evaluating the rotational and translational stiffness of its restraints to obtain the critical buckling load. This can be achieved by introducing, through a dimensionless parameter 𝜙_i, the effects of coupling between the axial loading and bending stiffness of the columns, on the classical stability functions. Subsequently, comparative, and parametric studies conducted on several frames are presented for assessing the influence of geometry, loading, bracing, and support conditions of the frame columns on the value of the effective buckling length factor K. The results show that the formulas recommended by different approaches can give rather inaccurate values of K, especially in the case of asymmetric frames. The expressions used refer solely to local stiffness distributions, and not to the overall behavior of the structure.