Effect of the torsional stiffness of closed‐section stiffeners on plate buckling in Eurocode 3, Part 1‐5

Abstract

AbstractLongitudinally stiffened plates are commonly used to increase the resistance to plate buckling. Closed cross‐section stiffeners provide high values of the torsional stiffness and thus are very efficient to avoid their premature lateral torsional buckling. With the current software tools, it is easy to assess the critical stress for the elastic global mode, taking into account the beneficial effect of these high values of torsional stiffness for stiffeners with closed cross‐sections. However, the torsional stiffness of longitudinal stiffeners is not considered in the analytical formula proposed by Annex A of EN 1993‐1‐5 for the assessment of the global buckling critical stress. A study is presented here where the effect of the torsional stiffness of longitudinal stiffeners on the plate buckling criterion of EN 1993‐1‐5 has been analysed. 216 configurations of stiffened plates were calculated through finite element GMNIA non linear analyses. Their compressive strength thus obtained were compared to their resistance to plate buckling as predicted by EN 1993‐1‐5, either by considering their torsional stiffness with EBPlate software or by completely ignoring it. The study clearly shows that EN 1993‐1‐5 leads to unsafe results when the torsional stiffness is taken into account in the calculations. Finally, it is concluded that the torsional stiffness of longitudinal stiffeners has to be ignored in the design of stiffened plates according to EN 1993‐1‐5.