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Civil-Comp Proceedings
ISSN 1759-3433 CCP: 77
PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON CIVIL AND STRUCTURAL ENGINEERING COMPUTING Edited by: B.H.V. Topping
Paper 46
Finite Element Simulations of Lateral Torsional Buckling of Tapered Cantilever Beams P. Buffel, G. Lagae, R. Van Impe, W. Vanlaere and M. De Beule
Laboratory for Research on Structural Models, Ghent University, Belgium Full Bibliographic Reference for this paper
P. Buffel, G. Lagae, R. Van Impe, W. Vanlaere, M. De Beule, "Finite Element Simulations of Lateral Torsional Buckling of Tapered Cantilever Beams", in B.H.V. Topping, (Editor), "Proceedings of the Ninth International Conference on Civil and Structural Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 46, 2003. doi:10.4203/ccp.77.46
Keywords: lateral torsional buckling, tapered beam, cantilever beam, buckling curve, design rule, Eurocode 3.
Summary
Adapting the height of a beam to the distribution of the internal forces results in material saving and can lead to an economic advantage. The resulting slender constructions must be verified against lateral torsional buckling. No simple design rules are available for tapered beams in the Eurocode 3 documents. The results presented in this paper show that the clause "General method for lateral torsional buckling of frames" may be used as a safe design criterion for tapered cantilevers loaded in their tip section with a point load at the upper flange.
Simulations are made with Abaqus [1]. Tapered beams are welded and residual stresses in accordance to [2] and [3] are included in the model. A simulation step was added to attain the stress free ends of the beam before adding an end plate at the higher end and a stiffener at the tip. A parabolic imperfection with bow
The width-to-thickness ratios of the web and the flanges correspond to the limits of class 2 and class 3 sections. Two ratios
The same dense mesh is used for all the simulations. This ensures that the influence of local buckling modes on the elastic critical load is automatically taken into account. Three magnitudes of the load are defined: the plastic load The results are compared to the 2 sets of buckling curves available in the final draft version of Eurocode 3 part 1-1 (date feb. 2002) [4]; the standard set (STD-set) and the alternative set (ALT-set). For clarity both sets are compared to each other.
The values of
The lowest positive eigenvalue of a linearised bifurcation analysis is used as
The value of
The lower bound of all the simulation results is compared to the available buckling curves. It is shown that within the ALT-set curve c is the best fit and is always on the safe side. From the STD-set curve b is to be used. The results indicate that there is no need to make a distinction between different values of
References
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