• Title/Summary/Keyword: buckling design

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A Study on Shape Optimization for Buckling and Postbuckling Behavior of Stiffened Laminated Composite Panels (보강된 복합적층 패널의 좌굴 및 좌굴후 거동의 형상 최적설계에 관한 연구)

  • Lee, Gwang-Rok;Jeong, Gi-Hyeon;Heo, Seong-Pil;Yang, Won-Ho;Jo, Myeong-Rae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.1
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    • pp.106-114
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    • 2001
  • In this study, a shape optimization of stiffener was conducted to increase buckling load or failure load in each case with a different design value and a different objective function for stiffened laminated composite panel of I-type under compression loading. Regarding each of buckling load or failure load as objective function, optimum design was carried out. In respect of optimum design, the effects of relative length of web and cab of stiffener on buckling load or failure load of postbuckling were investigated.

A Proposed method of the Strength Calculation of Pipe Support (파이프 서포트의 내력 산정 방안)

  • 이영욱;최순주
    • Journal of the Korean Society of Safety
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    • v.16 no.1
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    • pp.59-64
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    • 2001
  • Even though there is a guideline for the required strength of pipe support in inspection, it does not mean the nominal strength which can be used for the form work design. And, Concrete Specification defines that the pipe support should be designed according to the steel design guidelines but the design details are not provided, such as buckling length and the sectional modulus, etc. For the better prediction of strength of pipe support, the slenderness ratio of support which reflects the boundary condition should be considered. In this paper, the elastic buckling formula based on the slenderness is derived. The formula contains the strength reduction factor that consider the strength deduction caused by initial lateral deformation and is 0.65 consistently regardless of boundary conditions. And the coefficient of effective buckling length is calculated from the experiment.

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Buckling lengths of unbraced multi-storey frame columns

  • Ozmen, Gunay;Girgin, Konuralp
    • Structural Engineering and Mechanics
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    • v.19 no.1
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    • pp.55-71
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    • 2005
  • In several design codes and specifications, simplified formulae and diagrams are given for determining the buckling lengths of frame columns. It is shown that these formulae may yield rather erroneous results in certain cases. This is due to the fact that, the code formulae utilise only local stiffness distributions. In this paper, a simplified procedure for determining approximate values for the buckling loads of multi-storey frames is developed. The procedure utilises lateral load analysis of frames and yields errors in the order of 10%, which may be considered suitable for design purposes. The proposed procedure is applied to several numerical examples and it is shown that all the errors are in the acceptable range and on the safe side.

Optimal Stacking Sequence Design of Laminated Composites under Buckling Loads (좌굴하중하에서 복합적층판의 최적 적층 설계)

  • 윤성진;김관영;황운봉;하성규
    • Korean Journal of Computational Design and Engineering
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    • v.1 no.2
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    • pp.107-121
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    • 1996
  • An optimization procedure is proposed to determine the optimal stacking sequence on the buckling of laminated composite plates with midplane symmetry under various loading conditions. Classical lamination theory is used for the determination of the critical buckling load of simply supported angle-ply laminates. Analysis is performed by the Galerkin method and Rayleigh-Ritz method. The approximate solution of buckling is replaced by the algorithms that produce generalized eigenvalue problem. Direct search technique is employed to solve the optimization problem effectively. A series of computations is carried out for plates having different aspect ratios, different load ratios and different number of lay-ups.

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Strength buckling predictions of cold-formed steel built-up columns

  • Megnounif, A.;Djafour, M.;Belarbi, A.;Kerdal, D.
    • Structural Engineering and Mechanics
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    • v.28 no.4
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    • pp.443-460
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    • 2008
  • The aim of this paper is to propose a design procedure for predicting the buckling strength of built-up, cold-formed steel columns based on the two well known methods; the effective width method and the Direct Strength Method. Several design approaches, based on different elastic buckling solutions, were considered in this investigation. Traditional hand methods, without interaction effects between the different modes, and a new numerical spline finite strip method were used to predict the buckling stresses. All of the proposed methods were compared with experimental data on plain and lipped, built-up columns. Results have shown that the effective width approaches are more accurate than the Direct Strength Method. However, both methods can be investigated using more experimental data to assess a practical design method for built-up columns.

Multi-Objective Design Optimization of Composite Stiffened Panel Using Response Surface Methodology

  • Murugesan, Mohanraj;Kang, Beom-Soo;Lee, Kyunghoon
    • Composites Research
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    • v.28 no.5
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    • pp.297-310
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    • 2015
  • This study aims to develop efficient composite laminates for buckling load enhancement, interlaminar shear stress minimization, and weight reduction. This goal is achieved through cover-skin lay-ups around skins and stiffeners, which amplify bending stiffness and defer delamination by means of effective stress distribution. The design problem is formulated as multi-objective optimization that maximizes buckling load capability while minimizing both maximum out-of-plane shear stress and panel weight. For efficient optimization, response surface methodology is employed for buckling load, two out-of-plane shear stresses, and panel weight with respect to one ply thickness, six fiber orientations of a skin, and four stiffener heights. Numerical results show that skin-covered composite stiffened panels can be devised for maximum buckling load and minimum interlaminar shear stresses under compressive load. In addition, the effects of different material properties are investigated and compared. The obtained results reveal that the composite stiffened panel with Kevlar material is the most effective design.

Optimization for Buckling and Postbuckling Behavior of Stiffened Fiber Reinforced Composite Panels (보강된 섬유강화 복합재료 패널의 좌굴해석 및 파손강도의 최적 설계)

  • Lee, Gwang-Rog;Yang, Won-Ho;Cho, Mung-Rae;Sung, Ki-Deug
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.913-919
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    • 2001
  • In this study, fiber orientation of stiffener was conducted to increase buckling load or failure load in each case with a different design value and a different objective function for stiffened laminated composite panel of I-type under compression loading. Regarding each of buckling load or failure load as objective function, optimum design was carried out. In respect of optimum design, it was investigated that optimum shape for buckling could improve fail load for postbuckling, because it was difficult to investigate the optimization of postbuckling which need long analysis times for nonlinear analysis.

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Simplified approach to estimate the lateral torsional buckling of GFRP channel beams

  • Kasiviswanathan, M.;Anbarasu, M.
    • Structural Engineering and Mechanics
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    • v.77 no.4
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    • pp.523-533
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    • 2021
  • The present study investigates the lateral torsional buckling behaviour of pultruded glass fiber reinforced polymer (GFRP) simply supported channel beams subjected to uniform bending about their major axis. A parametric study by varying the sectional geometry and span of channel beams is carried out by using ABAQUS software. The accuracy of the FE models was ensured by verifying them against the available results provided in the literature. The effect of geometric nonlinearity, geometric imperfections, and the dependency of finite element mesh on the lateral torsional buckling were carefully considered in the FE model. Lateral torsional buckling (LTB) strengths obtained from the numerical study were compared with the theoretical LTB strengths obtained based on the Eurocode 3 approach for steel sections. The comparison between the numerical strengths and the design procedure proposed in the literature based on Eurocode 3 approach revealed disagreements. Therefore, a simplified improved design procedure is proposed for the safe design strength prediction of pultruded GFRP channel beams. The proposed equation has been provided that might aid the structural engineers in economically designing the pultruded GFRP channel beams in the future.

Optimisation of symmetric laminates with internal line supports for maximum buckling load

  • Walker, M.
    • Structural Engineering and Mechanics
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    • v.6 no.6
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    • pp.633-641
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    • 1998
  • Finite element solutions are presented for the optimal design of symmetrically laminated rectangular plates with various types of internal line supports. These plates are subject to a combination of simply supported, clamped and free boundary conditions. The design objective is the maximisation of the biaxial buckling load. This is achieved by determining the fibre orientations optimally with the effects of bending-twisting coupling taken into account. The finite element method coupled with an optimisation routine is employed in analysing and optimising the laminated plate designs. The effect of internal line support type and boundary conditions on the optimal ply angles and the buckling load are numerically studied. The laminate behavior with respect to fibre orientation changes significantly in the presence of internal line supports as compared to that of a laminate where there is no internal supporting. This change in behavior has significant implications for design optimisation as the optimal values of design variables with or without internal supporting differ substantially.

Derivation of Knockdown Factors for Composite Cylinders with Various Initial Imperfection Models (초기 결함 조건 모델에 따른 복합재 원통 구조의 좌굴 Knockdown factor 도출)

  • Kim, Do-Young;Sim, Chang-Hoon;Park, Jae-Sang;Yoo, Joon-Tae;Yoon, Young-Ha;Lee, Keejoo
    • Composites Research
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    • v.34 no.5
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    • pp.283-289
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    • 2021
  • This paper derives numerically the buckling Knockdown factors using two different initial imperfection models, such as geometric and loading imperfection models, to investigate the unstiffened composite cylinder with an ellipse pre-buckling deformation pattern. Single Perturbation Load Approach (SPLA) is applied to represent the geometric initial imperfection of a thin-walled composite cylinder; while Single Boundary Perturbation Approach (SBPA) is used to represent the geometric and loading imperfections simultaneously. The buckling Knockdown factor derived using SPLA is higher than NASA's buckling design criteria by approximately 84%, and lower than buckling test result by 9%. The buckling Knockdown factor using SBPA is higher than NASA's buckling design criteria by about 75%, and 14% lower than the buckling test result. Therefore, it is shown that the buckling Knockdown factors derived in this study can provide a lightweight design compared to the previous buckling design criteria while they give reasonably a conservative design compared to the buckling test for both the initial imperfection models.