Résumé

The present paper focuses on the rotational capacity of H-shaped steel sections; in particular, the influence of local buckling is accounted for by means of a generalized cross-sectional slenderness, which is used as a new parameter to characterize the cross-sectional rotational capacity, and, by extension, the available deformation capacity. Careful shell modelling of wide flange beams in bending was used in extensive F.E. parametric studies that included many parameters such as various materials (up to high strength steel), load and support arrangements, length-to-height ratios and web/flange slenderness. Specific attention was paid to the introduction of initial geometrical (local) imperfections. The paper then analyzes the numerical results and points out the various influences of shear, moment gradient, yield stress, static system and length-to-height ratio on the available rotational capacity. In a second step, the rotational capacity demand vs. stability criterion is detailed, and related to the proposed generalized cross-sectional slenderness, which is shown to be more appropriate than the b / t ratios usually proposed in design codes. Finally, suggestions for new ways of allowing for plastic analysis through such approaches are given.

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