• 한국전산구조공학회논문집
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• 제12권3호
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• pp.417-426
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• 1999

쉘형 구조물의 동적 불안정 문제를 다룬 연구결과는 다소 발표되고 있으나, 위상면을 이용하여 카오스 생성에 관해 기본적 현상을 다룬 연구는 아직 없는 실정이다. 동적 비선형 문제에서, 여러 가지 초기조건에 의해 불안정 현상이 민감하게 발생하는 이유를 파악하기 위해 위상면에서의 끌개의 특성을 조사하여 동적 불안정 생성과정을 검토하는 일은 매우 중요하다. 본 연구에서는 기하학적 비선형을 고려한 얕은 아치의 직접/간접 좌굴을 수치적 기법으로 조사하고, 이를 정적 좌굴하중과 비교한다.

• Structural Engineering and Mechanics
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• 제13권5호
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• pp.543-556
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• 2002

A dynamic elastic local buckling analysis is presented for a pile subjected to an axial impact load. The pile is assumed to be geometrically perfect. The interactions between the pile and the surrounding soil are taken into account. The interactions include the normal pressure and skin friction on the surface of the pile due to the resistance of the soil. The analysis also includes the influence of the propagation of stress waves through the length of the pile to the distance at which buckling is initiated and the mass of the pile. A perturbation technique is used to determine the critical buckling length and the associated critical time. As a special case, the explicit expression for the buckling length of a pile is obtained without considering soil resistance and compared with the one obtained for a column by means of an alternative method. Numerical results obtained show good agreement with the experimental results. The effects of the normal pressure and the skin friction due to the surrounding soil, self-weight, stiffness and geometric dimension of the cross section on the critical buckling length are discussed. The sudden change of buckling modes is further considered to show the 'snap-through' phenomenon occurring as a result of stress wave propagation.

• 한국농공학회지
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• 제34권4호
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• pp.97-105
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• 1992

The main purpose of this paper is to present the buckling loads of tapered columns due to dynamic concept. The ordinary differential equation governing the bucking loads for tapered columns is derived on the basis of dynamic concept. Three kinds of cross sectional shape are considered in the governing equation. The Improved Euler method and Determinant Search method are used to perform the integration of the differential equation and to determine the buckling loads, respectively. The hinged-hinged, hinged-clamped, clamped-clamped and free-clamped end constraints are applied in numerical examples. The buckling loads are reported as the function of section ratio, and the effects of cross-sectional shapes are investigated. The buckling load equation, which are fitted by numerical data, are proposed as a function of section ratio. It is expected that these equations can be utilized in structural engineering field.

• Steel and Composite Structures
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• 제52권1호
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• pp.89-107
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• 2024

This article focuses on the static and dynamic analysis and optimization of an anisogrid lattice plate subjected to axial compressive load with simply supported boundary conditions. The lattice plate includes diagonal and transverse ribs and is modeled as an orthotropic plate with effective stiffness properties. The study employs the first-order shear deformation theory and the Ritz method with a Legendre approximation function. In the realm of optimization, the Non-dominated Sorting Genetic Algorithm-II is utilized as an evolutionary multi-objective algorithm to optimize. The research findings are validated through finite element analysis. Notably, this study addresses the less-explored areas of optimizing the geometric parameters of the plate by maximizing the buckling load and natural frequency while minimizing mass. Furthermore, this study attempts to fill the gap related to the analysis of the post-buckling behavior of lattice plates, which has been conspicuously overlooked in previous research. This has been accomplished by conducting nonlinear analyses and scrutinizing post-buckling diagrams of this type of lattice structure. The efficacy of the continuous methods for analyzing the natural frequency, buckling, and post-buckling of these lattice plates demonstrates that while a degree of accuracy is compromised, it provides a significant amount of computational efficiency.

• Structural Engineering and Mechanics
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• 제14권6호
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• pp.661-677
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• 2002

The subject of this investigation is to study the buckling of cross-ply laminated orthotropic cylindrical thin shells with variable elasticity moduli and densities in the thickness direction, under external pressure, which is a power function of time. The dynamic stability and compatibility equations are obtained first. These equations are subsequently reduced to a system of time dependent differential equations with variable coefficients by using Galerkin's method. Finally, the critical dynamic and static loads, the corresponding wave numbers, the dynamic factors, critical time and critical impulse are found analytically by applying a modified form of the Ritz type variational method. The dynamic behavior of cross-ply laminated cylindrical shells is investigated with: a) lamina that present variations in the elasticity moduli and densities, b) different numbers and ordering of layers, and c) external pressures which vary with different powers of time. It is concluded that all these factors contribute to appreciable effects on the critical parameters of the problem in question.

• Structural Engineering and Mechanics
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• 제15권6호
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• pp.653-668
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• 2003

Many papers which deal with the dynamic instability of shell-like structures under the STEP load have been published. But, there have been few papers related to the dynamic instability of hybrid cable domes. In this study, the dynamic instability of hybrid cable domes considering geometric nonlinearity is investigated by a numerical method. The characteristic structural behaviour of a cable dome shows a strong nonlinearity, so we determine the shape of a cable dome by applying initial stress and examine the indirect buckling mechanism under dynamic external forces. The dynamic critical loads are determined by the numerical integration of the nonlinear equation of motion, and the indirect buckling is examined by using the phase plane to investigate the occurrence of chaos.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.254-260
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• 2000

The spacer grid is one of the main structural components in fuel assembly, which supports the fuel rods, guides cooling water, and protects the fuel assembly from the external impact load such as earthquakes. The nonlinear dynamic impact analysis is conducted by using the finite element code ABAQUS/Explicit. Boundary condition for dynamic analysis is well applied to the test condition. Simulation results also similarly predict the local buckling phenomena. In addition to the buckling parameter, the local buckling cause is examined by both simulation and test method. It is found to correspond well with the test results. Impact tests are also carried out for some specimens of the spacer grid in order to compare the results between the test and the simulation. This test is accomplished by a free fall dummy weight onto the specimen. From this test, only the uppermost and lowermost layers of the multi-cell are buckled, which implies the local buckling at the weakest point of the grid structure.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.69-76
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• 2003

We investigate the fundamental mechanisms of the dynamic instability when the sinusoidal shaped arch structures subjected to sinusoidal harmonic excitation with pin-ends. In nonlinear dynamics, examining the characteristics of attractor on the phase plane and investigating the dynamic buckling process are very important thing for understanding why unstable phenomena are sensitively originated by various initial conditions. In this study, the direct and the indirect snap-buckling of shallow arches considering geometrical nonlinearity are investigated numerically and compared with the step excitation critical load.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.55-60
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• 2012

The purpose of this study is to investigate the buckling load of filament-wound composite towers for large scale wind-turbine using finite element method(FEM). To define material properties, we used both the effective property method and the stacking properties method. The effective properties method is to assume that composite consists of one ply. The stacking properties method is to assume that composite consists of some stacked plies. First, linear buckling analysis of the tower, filament-wounded with angles of [${\pm}30$] was carried out by two methods for composite material properties, the stacking method and the effective method. and FE analysis was performed for the composite towers according to filament winding angles of [${\pm}30$], [${\pm}45$], [${\pm}60$]. FE analysis results using the stacking properties of the composite were in good agreement with the results by the effective properties. The difference between FEM results by material properties methods was approximately 0~2.3% in buckling Analysis and approximately 0~0.6% in modal analysis. And above the angle of [${\pm}60$], there was a little change of buckling load.

• 한국강구조학회 논문집
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• 제19권1호
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• pp.99-106
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• 2007

이 논문은 일정체적 양단고정 기둥의 정 동적 최적형상에 관한 연구이다. 기둥의 단면은 정다각형이며, 단면깊이는 포물선으로 변화하는 변단면이다. 축방향 압축하중이 작용하는 기둥의 고유진동수 및 좌굴하중을 산정하는 수치해석 기법을 개발하였다. 그러한 기둥의 자유진동을 지배하는 미분방정식을 유도하고 Runge-Kutta법과 Regula-Falsi법을 이용하여 고유진동수를 산정하였다. 수치해석의 결과로부터 얻어진 하중-고유진동수 사이의 관계를 이용하여 기둥의 좌굴하중을 산정하였다. 기둥의 변수연구를 통하여 동적 안정영역, 동적 최적형상 및 최강기둥의 형상을 산출하였다.