Keywords: GFRP composite members, GFRP pultruded beams, flexural behaviour, local buckling, lateral-torsional buckling, lateral-torsional post-buckling.

This paper deals with the numerical evaluation of the first-order, buckling and post-buckling behaviour of simply supported and cantilever beams built from pultruded I-section GFRP profiles. It addresses the beam (i) linear behaviour, (ii) shear deformation, (iii) local and lateral-torsional buckling behaviour and (iv) lateral-torsional post-buckling behaviour, including load point of application effects. The numerical results, obtained through (i) a novel generalised beam theory (GBT) beam finite element formulation and (ii) ABAQUS shell finite element analyses, are compared with the experimental values given in Part 1 of this paper [1].

Initially, the paper describes the main concepts and procedures involved in the formulation and implementation of GBT-based beam finite elements to perform thin-walled member first-order, buckling and post-buckling [2]. Then, these finite element models are employed to simulate some of the tests, concerning the (i) simply supported beam first-order, local buckling and lateral-torsional buckling behaviours and (ii) cantilever lateral-torsional buckling behaviour (various load application points). For comparison purposes, most GBT-based results are compared with ABAQUS shell finite element values ? excellent agreement is found in all cases and the high computational efficiency of the GBT analyses is clearly demonstrated. The paper also includes shell finite element simulations of the post-buckling behaviour of cantilevers loaded at the end section shear centre and top flange.

Concerning the comparison between the numerical and experimental results, the following remarks are appropriate:

• The experimental results for 1) simply supported beam first-order and local buckling and 2) cantilever lateral-torsional buckling (including load point of application effects) are numerically replicated with fairly good accuracy by the GBT and ABAQUS analyses: the rare cases in which discrepancies are found can be logically explained.
• The experimental results for simply supported beam lateral-torsional buckling cannot be properly simulated because of the additional stiffness introduced by the loading systems, which obviously cannot be modelled numerically.
• The experimental results for cantilever lateral-torsional post-buckling are reasonably replicated by the ABAQUS shell finite element analyses, although they cannot capture the hysteretic behaviour stemming from friction at the loading system mechanical fastening devices. Nevertheless, as expected, most numerical load-displacement curves fall inside the experimental hysteretic loop.

1

J.R. Correia, F.A. Branco, N. Silva, D. Camotim, N. Silvestre, "First-Order, Buckling and Post-Buckling Behaviour of GFRP Pultruded Beams: Part 1 Experimental Study", in B.H.V. Topping, L.F. Costa Neves, R.C. Barros, (Editors), "Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 31, 2009. doi:10.4203/ccp.91.31

2

N.M.F. Silva, R. Degenhardt, D. Camotim, N. Silvestre, "On the use of Generalised Beam Theory to assess the buckling and post-buckling behaviour of laminated CFRP cylindrical panels", International Journal of Structural Stability and Dynamics, accepted for publication, 2009.

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