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CivilComp Proceedings
ISSN 17593433 CCP: 83
PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping, G. Montero and R. Montenegro
Paper 191
Generalised Beam Theory Formulation to Analyse the PostBuckling Behaviour of FRP Composite ThinWalled Members N.F. Silva, N. Silvestre and D. Camotim
Department of Civil Engineering and Architecture, ICIST/IST, Technical University of Lisbon, Portugal N.F. Silva, N. Silvestre, D. Camotim, "Generalised Beam Theory Formulation to Analyse the PostBuckling Behaviour of FRP Composite ThinWalled Members", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", CivilComp Press, Stirlingshire, UK, Paper 191, 2006. doi:10.4203/ccp.83.191
Keywords: generalized beam theory, geometrically nonlinear formulation, elastic postbuckling analysis, FRP composite thinwalled members, geometric imperfections.
Summary
This paper presents a geometrically nonlinear generalised beam theory (GBT)
formulation intended to analyse the elastic postbuckling behaviour of arbitrary
thinwalled composite prismatic members. This formulation is an extension to recent GBT
developments in areas of (i) postbuckling analysis of isotropic members [1] and (ii)
linear (first order) and buckling analyses of orthotropic FRP composite members [2,3].
However, the crosssection analysis, a key task in the performance of a GBT analysis,
was carried out by means of a novel approach, (i) based on the solution of a series of
auxiliary eigenvalue problems involving constitutive tensors and (ii) able to handle
any type of crosssection shape. Its application was illustrated through the determination
of the deformation modes of a crosssection combining a closed cell with a branched
open wall assembly. The output of this analysis consists of a complete set of deformation
modes that includes global, distortional, localplate, warping shear and transverse
extension modes, (Figure 1 shows the most relevant ones for the case of a lipped channel section).
A GBTbased nonlinear beam finite element is developed and its implementation leads to the definition of a system of nonlinear equilibrium equations which (i) is valid in the large deformation range, (ii) accounts for the presence of initial geometrical imperfections and (iii) takes advantage of the unique GBT mode decomposition features. The geometrically nonlinear equilibrium equations, which take into account all material (mechanical) coupling effects, are derived from an energy approach and numerically implemented by means of a standard incrementaliterative procedure. In order to validate and illustrate the application of the proposed geometrically nonlinear formulation, numerical results concerning the distortional postbuckling behaviour of simply supported initially imperfect FRP composite lipped channel columns (uniformly compressed members) with crossply orthotropy are presented and discussed (see Figures 1 and 2). For validation purposes, the postbuckling results are also compared with values yielded by ABAQUS shell finite element analyses. References
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