Flexural–torsional buckling of fiber-reinforced plastic composite cantilever I-beams

Article (PDF Available)inComposite Structures 60(2):205-217 · May 2003with352 Reads
DOI: 10.1016/S0263-8223(02)00304-5
A combined analytical and experimental study of flexural–torsional buckling of pultruded fiber-reinforced plastic (FRP) composite cantilever I-beams is presented. An energy method based on nonlinear plate theory is developed for instability of FRP I-beam, and the formulation includes shear effect and bending–twisting coupling. Three different types of buckling mode shape functions of transcendental function, polynomial function, and half simply supported beam function, which all satisfy the cantilever beam boundary conditions, are used to obtain the eigenvalue solution, and their accuracy in the analysis are investigated in relation to finite element results. Four different geometries of FRP I-beams with cantilever beam configurations and with varying span lengths are experimentally tested under tip loads to evaluate their flexural–torsional buckling response. The loads are applied at the centroid of the tip cross-sections, and the critical buckling loads are obtained by gradually adding weight onto a loading platform. A good agreement among the proposed analytical solutions, experimental testing, and finite element method is obtained, and simplified explicit formulas for flexural–torsional buckling of cantilever beams with applied load at the centroid of the cross-section are developed. The effects of vertical load position through the cross-section, fiber orientation and fiber volume fraction on buckling behavior are also studied. The proposed analytical solutions can be used to predict the flexural–torsional buckling loads of FRP cantilever beams and to formulate simplified design equations.
    • "(Dentro do leque de funções de forma existentes na literatura [18,19], que permitem aproximar a deformação de elementos por encurvadura (e.g., funções transcendentais, polinomiais, etc.), apenas se consideram funções trigonométricas simples (seno e cosseno) de modo a obter expressões analíticas aproximadas também simples, cf. Quadro 1. Uma vez definida a energia potencial do sistema contínuo (12), a aplicação do método de Rayleigh-Ritz para cada caso de estudo envolve a substituição do vetor definido em (20), com as respetivas funções de forma, no funcional energia Π 2 . "
    [Show abstract] [Hide abstract] ABSTRACT: The use of glass fibre reinforced polymer (GFRP) pultruded profiles in structural applications has been increasing consistently. However, there is still some reluctance about the use of such elements due to several aspects, among which their susceptibility to instability phenomena. This paper presents the results of a numerical, analytical and experimental study on the behaviour of lateral-torsional buckling of GFRP beams. A formulation is developed and implemented numerically, which allows analysing any type of instability on I or H-section beams under 3- and 4-point bending. The lateral buckling (flexural-torsion) case is particularized and a simple expression that allows estimating critical loads considering the influence of the conditions of support and lateral bracing is derived. The numerical results of the formulation and analytical results obtained with the simplified expression are validated by comparison with experimental and numerical values from the literature, with a good agreement having been obtained.
    Full-text · Article · Jul 2016 · Composite Structures
    • "In the fundamental theory for LTB instability [20, 21] that leads to a closed form solution it is assumed that the height of loadings remains unchanged relative to the deforming cross-sections, and that its line of action moves parallel to the initial undeformed position. This theoretical condition was not always satisfied in the testing from previous studies234567891011. Furthermore, LTB specimens have been loaded through a steel fixture that is in contact with the top flange. "
    [Show abstract] [Hide abstract] ABSTRACT: This paper presents test results for Pultruded FRP (PFRP) beams failing by elastic Lateral-Torsional Buckling (LTB) under various loading and displacement boundary conditions. Beams are simply supported at both ends for major-axis flexure. Results are presented for 114 tests, comprising 19 beams of four PFRP sections at four or five spans, and six groups for mid-span load applied at three heights, with or without end fixity of lateral flexure. Buckling resistance is established either by the Southwell plot method or from the peak load. Measured LTB loads are compared with predictions obtained using closed form equations to show that these expressions will provide a safe resistance for design when the moduli of elasticity are those taken directly from pultruder’s design manual.
    Full-text · Article · Apr 2014
    • "Linear elastic flat shell elements have successfully been adopted in previous FE studies with thin-walled FRP structures [10, 12, 29, 30] . The element chosen is the secondorder ABAQUS/Standard thick shell element S8R, having 8-nodes and six degrees of freedom per node. "
    [Show abstract] [Hide abstract] ABSTRACT: Presented are results from geometric non-linear finite element analyses to examine the Lateral Torsional Buckling (LTB) resistance of a Pultruded Fibre Reinforced Polymer (FRP) I-beam when initial geometric imperfections associated with the LTB mode shape are introduced. A data reduction method is proposed to define the limiting buckling load and the method is used to present strength results for a range of beam slendernesses and geometric imperfections. Prior to reporting on these non-linear analyses, Eigenvalue FE analyses are used to establish the influence on resistance of changing load height or displacement boundary conditions. By comparing predictions for the beam with either FRP or steel elastic constants it is found that the former has a relatively larger effect on buckling strength with changes in load height and end warping fixity. The developed finite element modelling methodology will enable parametric studies to be performed for the development of closed form formulae that will be reliable for the design of FRP beams against LTB failure.
    Full-text · Article · Jun 2013
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