• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.1-4
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• 2000

This paper presents the analytical results of local - global interaction buckling of orthotropic I-shape compression members. Employing the equilibrium approach, the characteristic equation for local and global interaction buckling of I-shape compression member is derived. Using the derived equation, the buckling coefficients with respect to the ratio of length to width for the I-shape column are suggested as a graphical form. In addition, graphical forms of local, global and FEM results are presents, and they are compared with those in published document.

• 한국기계가공학회지
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• 제20권1호
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• pp.7-15
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• 2021

Buckling of cylindrical structures has been extensively researched, because it is an important phenomenon to be considered in structural design. However, the evaluation of thermal effects on the buckling of cylindrical structures has been insufficient; therefore, this study evaluates this thermal effect using shell elements. In addition, the thermal effect on the buckling of temperature-dependent nonlinear materials was evaluated. Nonlinear and linear buckling analyses were performed using the arc-length method to investigate the behavioral characteristics of a cylindrical structure. The basic theory of the linear buckling analysis of a cylindrical structure subjected to thermal stress was derived and presented by applying the thermal stress basic theory.

• Structural Engineering and Mechanics
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• 제50권5호
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• pp.697-708
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• 2014

The intentional buckling design of micro-films has various potential applications in engineering. The buckling amplitude and critical strain of micro-films are the crucial parameters for the buckling design. In the reported studies, the film parameters were regarded as deterministic. However, the geometrical and physical parameters uncertainty of micro-films due to manufacturing becomes prominent and needs to be considered. In the present paper, the probabilistic nonlinear buckling analysis of micro-films with uncertain parameters is proposed for design accuracy and reliability. The nonlinear differential equation and its asymptotic solution for the buckling micro-film with nominal parameters are firstly established. The mean values, standard deviations and variation coefficients of the buckling amplitude and critical strain are calculated by using the probability densities of uncertain parameters such as the film span length, thickness, elastic modulus and compressive force, to reveal the effects of the film parameter uncertainty on the buckling deformation. The results obtained illustrate the probabilistic relation between buckling deformation and uncertain parameters, and are useful for accurate and reliable buckling design in terms of probability.

• Smart Structures and Systems
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• 제26권2호
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• pp.213-226
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• 2020

In this manuscript, static and dynamic behaviors of geometrically imperfect carbon nanotubes (CNTs) subject to different types of end conditions are investigated. The Doublet Mechanics (DM) theory, which is length scale dependent theory, is used in the analysis. The Euler-Bernoulli kinematic and nonlinear mid-plane stretching effect are considered through analysis. The governing equation of imperfect CNTs is a sixth order nonlinear integro-partial-differential equation. The buckling problem is discretized via the differential-integral-quadrature method (DIQM) and then it is solved using Newton's method. The equation of linear vibration problem is discretized using DIQM and then solved as a linear eigenvalue problem to get natural frequencies and corresponding mode shapes. The DIQM results are compared with analytical ones available in the literature and excellent agreement is obtained. The numerical results are depicted to illustrate the influence of length scale parameter, imperfection amplitude and shear foundation constant on critical buckling load, post-buckling configuration and linear vibration behavior. The current model is effective in designing of NEMS, nano-sensor and nano-actuator manufactured by CNTs.

• Steel and Composite Structures
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• 제22권3호
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• pp.691-712
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• 2016

In this editorial, buckling analytical investigation of the nanocomposite plate with square cut out reinforced by carbon nanotubes (CNTs) surrounded by Pasternak foundation is considered. The plate is presumed has square cut out in center and resting on Pasternak foundation. CNTs are used as amplifier in plate for diverse distribution, such as uniform distribution (UD) and three patterns of functionally graded (FG) distribution types of CNTs (FG-X, FG-A and FG-O). Moreover, the effective mechanical properties of nanocomposite plate are calculated from the rule of mixture. Domain decomposition method and orthogonal polynomials are applied in order to define the shape function of nanocomposite plate with square cut out. Finally, Rayleigh-Ritz energy method is used to obtain critical buckling load of system. A detailed parametric study is conducted to explicit the effects of the dimensions of plate, length of square cut out, different distribution of CNTs, elastic medium and volume fraction of CNTs. It is found from results that increase the dimensions of plate and length of square cut out have negative impact on buckling behavior of system but considering CNTs in plate has positive influence.

• Structural Engineering and Mechanics
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• 제71권6호
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• pp.669-682
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• 2019

We in this article study nonlinear thermal buckling of bi-directional functionally graded beams in the theoretical frameworks of nonlocal strain graded theory. To begin with, it is assumed that the effective material properties of beams vary continuously in both the thickness and width directions. Then, we utilize a higher-order shear deformation theory that includes a physical neutral surface to derive the size-dependent governing equations combining with the Hamilton's principle and the von $K{\acute{a}}rm{\acute{a}}n$ geometric nonlinearity. It should be pointed out that the established model, containing a nonlocal parameter and a strain gradient length scale parameter, can availably account for both the influence of nonlocal elastic stress field and the influence of strain gradient stress field. Subsequently, via using a easier group of initial asymptotic solutions, the corresponding analytical solution of thermal buckling of beams is obtained with the help of perturbation method. Finally, a parametric study is carried out in detail after validating the present analysis, especially for the effects of a nonlocal parameter, a strain gradient length scale parameter and the ratio of the two on the critical thermal buckling temperature of beams.

• 대한토목학회논문집
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• 제32권4A호
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• pp.217-225
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• 2012

본 연구에서는 비대칭 연결재를 갖는 조립식 압축부재의 연결재 종류에 따른 좌굴 거동을 알아보기 위한 실 대형 실험을 실시하였다. 압축부재인 H-300 형강 10 m 부재 3개를 볼트 연결하여 총 길이 30 m가 되도록 2 m 간격으로 2열 배치한 후 연결재 종류가 띠판, ㄷ형강, 복 ㄷ형강인 경우에 대하여 압축 실험을 실시하였다. 본 논문에서는 연결재 종류에 따른 실험 좌굴 하중을 평가하고 이를 유한요소해석 결과인 좌굴하중과 Timoshenko 식에 의한 좌굴하중과 비교 분석 하였으며, 연결재 종류에 따른 조립식 압축부재의 좌굴 거동으로 인한 종방향 변위, 횡방향 변위, 변형률 등을 분석하였다. 실험 결과 비대칭 연결재를 갖는 조립식 압축부재의 연결재가 띠판일 때 보다 복 ㄷ형강일 때의 좌굴 하중은 4.2%, ㄷ형강일 때는 36.6% 감소하는 것으로 나타났다.

• 한국지반공학회논문집
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• 제31권9호
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• pp.39-51
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• 2015

근래 구조물 기초보강을 위한 마이크로파일공법의 적용사례가 점차 증가하고 있으며, 이에 따른 관련 연구가 다수 수행되고 있다. 그러나 국내 연구는 대부분 Case. I, II-Type의 지지거동에 국한되어 마이크로파일 자체의 구조적 검토에 대한 연구는 미미한 실정이다. 따라서 본 논문에서는 국내에서 주로 사용되는 마이크로 파일에 대한 각각의 강봉 및 그라우트조건에 따른 좌굴특성을 검토하였다. 검토결과 마이크로파일 직경이 작을수록 지반의 임계좌굴점착력($C_{ucr}$)는 증가하게 되며, 특히 임계좌굴길이($L_{cr}$) 이하에서는 마이크로파일 길이가 길수록 임계좌굴하중($P_{cr}$)이 감소함을 알 수 있었다. 또한 축하중을 받는 마이크로파일의 좌굴파괴와 압축파괴 가능성을 구분, 평가할 수 있는 방법을 제시하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제18권6호
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• pp.11-20
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• 2014

본 연구는 정현형 주름과 마름모형 주름 형상의 전단좌굴 특성을 비교, 분석하는 것이 목적이다. 이를 위해서 동일한 길이의 마름모꼴 주름과 정현파주름을 해석대상모델로 채택하였으며, 선형좌굴해석을 통한 전단좌굴특성과 이론식에 의한 특성을 분석하였다. 일반적으로 주름강판의 전단좌굴 형태는 국부좌굴, 전체좌굴 및 두 좌굴에 의한 연성좌굴로 분류된다. 그러나 마름모꼴주름과는 달리 정현파주름형상은 평평한 면이 없기 때문에 전단좌굴의 양상에 대한 경향이 달라진다. 특히 국부좌굴과 전체좌굴의 경계에서 나타나는 전단응력변화와 양상은 주름형태에 의해 차이가 난다. 분석 결과에서 볼 때, 제형 (마름모꼴)의 경우는 이론식내의 전체좌굴과 국부좌굴의 경계에서 연성좌굴모드가 발생했다. 그러나 정현파형의 경우 전체좌굴이 발생하는 구간에서 연성좌굴모드가 발생하는 양상을 보였다. 또한 국부좌굴 구간에는 제형형상이 그리고 전체좌굴 구간에서는 정현파형상이 전단좌굴에 저항하는데 유리하게 작용하였다.

• 복합신소재구조학회 논문집
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• 제5권3호
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• pp.1-7
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• 2014

Buckling, a form of failure happened to plated structures, is investigated in this study. The main focus is to investigate the effects of thickness of the plates having through-thickness holes on buckling when the plate is subjected to in-plane compression. Plates having length of 200mm and width of 100mm are chosen to have thickness in range from 0.50mm to 10mm. Two holes of diameters of 20mm are implemented in plates. The finite element procedure using ABAQUS is applied for analyses. Then using the Gerard and Becker equation compressive buckling coefficients, Kc, are calculated and presented to enable engineers to calculate buckling load for the desired plate with holes in specific dimension. In order to generalize the obtained results, verification analysis has been performed by taking plates having different dimensions from the original ones used in this study. The verification showed the capability of buckling coefficients to predict buckling stresses of plates in various dimensions.