Influence of initial geometric imperfections in the lateral buckling problem of thin walled pultruded GFRP I-profiles

This paper aims at investigating the influence of some typical manufacturing geometric imperfections on the pre-buckling behaviour of transversally loaded GFRP I-beam. One dimensional mechanical approach is proposed by modelling each panel of the cross section as a Timoshenko rectangular beam. In addition to the usual displacement and rotational degrees of freedom used in conventional beam models, few extra degrees of freedom are introduced in order to account for sectional distorsions. The model is based on the common assumptions of linear elasticity with small strains and moderate rotations. Two kinds of manufacturing imperferction are taken into account: minor axis out-of-straightness and web/flange planes non-orthogonality the latter representing a particular feature of the present model. Numerical analyses, developed via finite elements, show that such kind of imperfections can significantly influence the pre-buckling behaviour making deformability requirements a fundamental design rule.