• Structural Engineering and Mechanics
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• 제73권2호
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• pp.181-190
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• 2020

In this paper, non-linear dynamic buckling behaviour of laminated composite curved panels subjected to dynamic in-plane axial compressive loads is studied using finite element methods. The work is carried out using the finite element software ABAQUS. The curved panels are modelled with S4R element and the nonlinear dynamic equilibrium equations are solved using the ABAQUS/Explicit algorithm. The effect of aspect ratio, radius of curvature and thickness are studied. The importance of orientation of plies in the direction of loading is also reiterated in this study. Vol'mir's criterion is used to calculate the dynamic buckling loads. The panels are subjected to rectangular pulse load of various amplitude and durations and the responses are observed. For particular loading amplitude, a critical value of loading duration is observed beyond which the variation of dynamic buckling load is insignificant. It is also observed that, the value of dynamic bucking load reduces as the loading duration is increased though the reduction is not much after a particular loading duration.

• 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.

• 한국소음진동공학회논문집
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• 제16권10호
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• pp.1074-1081
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• 2006

This paper deals with the dynamic stability analysis of clamped-hinged columns with constant volume. Numerical methods are developed for solving natural frequencies and buckling loads of such columns, subjected to an axial compressive load. The parabolic taper with the regular polygon cross-section is considered, whose material volume and column length are always held constant. Differential equations governing both free vibrations and buckled shapes of such columns are derived. The Runge-Kutta method is used to integrate the differential equations, and the Regula-Falsi method is used to determine natural frequencies and buckling loads, respectively. The numerical methods developed herein for computing natural frequencies and buckling loads are found to be efficient and robust. From the numerical results, dynamic stability regions, dynamic optimal shapes and configurations of strongest columns are reported in figures and tables.

• Structural Engineering and Mechanics
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• 제15권4호
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• pp.463-476
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• 2003

This paper deals with nonlinear asymmetric dynamic buckling of clamped laminated angle-ply composite spherical shells under suddenly applied pressure loads. The formulation is based on first-order shear deformation theory and Lagrange's equation of motion. The nonlinearity due to finite deformation of the shell considering von Karman's assumptions is included in the formulation. The buckling loads are obtained through dynamic response history using Newmark's numerical integration scheme coupled with a Newton-Raphson iteration technique. An axisymmetric curved shell element is used to investigate the dynamic characteristics of the spherical caps. The pressure value beyond which the maximum average displacement response shows significant growth rate in the time history of the shell structure is considered as critical dynamic load. Detailed numerical results are presented to highlight the influence of ply-angle, shell geometric parameter and asymmetric mode on the critical load of spherical caps.

• Structural Engineering and Mechanics
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• 제9권5호
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• pp.483-490
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• 2000

After manufacturing a structure, the assembly of structural components is often not as perfect as expected due to the immaturity of current engineering techniques. Thus the actual buckling load for an element is sometimes not consistent with that predicted in the design. For design considerations, it is necessary to establish an analytical method for determining the buckling load experimentally. In this paper, a dynamic method is described for determining the linear buckling loads for elastic, perfectly flat plates. The proposed method does not require the application of in-plane loads and is feasible for arbitrary types of boundary conditions. It requires only the vibrational excitation of the plate. The buckling load is determined from the measured natural frequencies and vibration mode shapes.

• 대한토목학회논문집
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• 제31권1A호
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• pp.1-7
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• 2011

이 연구는 일정표면적 기둥의 좌굴하중에 관한 연구이다. 기둥단면의 변화깊이의 형상함수로는 선형 변단면을 채택하였다. 이러한 기둥의 좌굴형상을 지배하는 상미분방정식을 유도하기 위하여 축방향 압축력을 받는 기둥의 동적 평형방정식을 이용하였다. 수치해석 예에서는 회전-회전, 회전-고정, 고정-고정의 지점조건을 고려하였다. 수치해석의 결과로 각종 기둥변수들이 좌굴하중에 미치는 영향을 분석하였다. 특히, 일정표면적으로부터 최대 좌굴하중을 발생시킬 수 있는 기둥의 최강단면비와 그에 대응하는 최강좌굴하중을 산정하였다. 기둥 축에 횡방향 내부지점을 설치하여 좌굴하중을 증가시킬 수 있는 무변위 위치를 찾기 위하여 기둥의 좌굴형상을 산출하였다.

• 한국강구조학회 논문집
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• 제12권6호
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• pp.727-736
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• 2000

본 연구에서는 궤도의 좌굴해석 및 그 결과를 통해 열차하중이 직선 및 곡선 장대레일 궤도의 온도좌굴 거동에 미치는 영향에 대해 평가하였다. 차량을 고려한 온도좌굴 해석은 바퀴하중하에서 장대레일 궤도의 수직 처짐에 기인한 상향처짐을 결정하기 위해 유사정적 하중모델을 가정하였으며, 차량의 무게와 속도, 궤도의 곡률, 캔트, 그외의 열차와 궤도의 동적인 상호작용으로 인한 횡방향하중은 열차의 수직하중에 대한 수평하중 비에 포함하여 수행하였다. 수치적 해석을 통해 장대레일의 상부 및 하부좌굴온도를 구하였고, 이런 해석결과들을 기존의 열차하중을 포함하지 않은 정적 좌굴해석결과들과 비교하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2001년도 춘계학술대회 논문집
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• pp.295-302
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• 2001

The lateral stability of curved continuous welded rail (CWR) is studied fur buckling prevention. This study includes the influences of vehicle induced loads on the thermal buckling behavior of straight and curved CWR tracks. quasi-static loads model is assumed to determine the uplift region, which occurs due to the vertical track deformation induced by wheel loads of vehicle. Parametric numerical analyses are performed to calculate the upper and lower critical buckling temperatures of CWR tracks. The parameters include track lateral resistance, track curvature, longitudinal stiffness, tie-ballast friction coefficient, axle load, truck center spacing, and the ratio of lateral to vertical vehicle load. This study provides a guideline for the improvement or stability for dynamic buckling in on tracks.

• 한국공간구조학회논문집
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• 제20권2호
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• pp.77-85
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• 2020

This paper examined the dynamic instability of a shallow arch according to the response characteristics when nearing critical loads. The frequency changing feathers of the time-domain increasing the loads are analyzed using Fast Fourier Transformation (FFT), while the response signal around the critical loads are analyzed using Hilbert-Huang Transformation (HHT). This study reveals that the models with an arch shape of h = 3 or higher exhibit buckling, which is very sensitive to the asymmetric initial conditions. Also, the critical buckling load increases as the shape increases, with its feather varying depending on the asymmetric initial conditions. Decomposition results show the decrease in predominant frequency before the threshold as the load increases, and the predominant period doubles at the critical level. In the vicinity of the critical level, sections rapidly manifest the displacement increase, with the changes in Instantaneous Frequency (IF) and Instant Energy (IE) becoming apparent.

• 소음진동
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• 제7권3호
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• pp.439-447
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• 1997

In this study, the dynamic instabilities of a nonlinear elastic system subjected to follower forces are investigated. The two-degree-of-freedom double pendulum model with nonlinear geometry, cubic spring, and linear viscous damping is used for the study. The constant, the initial impact forces acting at the end of the model are considered. The chaotic nature of the system is identified using the standard methods, such as time histories, power density spectrum, and Poincare maps. The responses are chaotic and unpredictable due to the sensitivity to initial conditions. The sensitivities to parameters, such as geometric initial imperfections, magnitude of follower force, direction control constant, and viscous damping, etc., are analysed. Dynamic buckling loads are computed for various parameters, where the loads are changed drastically for the small change of parameters.