Buckling Resistance of Longitudinally Stiffened Panels with Closed Stiffeners under Direct Longitudinal Stresses

AbstractThe buckling behaviour of panels may be determined according to EN 1993‐1‐5 [1]. Most of the design rules relating to stiffened panels in EN 1993‐1‐5 were derived on the basis of open‐section stiffeners. Several recent investigations have shown that the application of the design rules according to EN 1993‐1‐5 [1] taking into account the torsional stiffness of the stiffeners may overestimate the resistance of the panels. Therefore, the recent Amendment A2 to EN 1993‐1‐5 states that the torsional stiffness of stiffeners should generally be neglected in determining critical plate buckling stresses. In addition, prEN 1993‐1‐5 [2] provides rules for considering the torsional stiffness of stiffeners. However, in this paper it will be shown that even the rules of prEN 1993‐1‐5 are not reliable as far as torsional stiffness is concerned. The paper focuses on the investigation of the buckling behaviour of stiffened panels with closed section stiffeners subjected to constant longitudinal compression stresses and shows improved rules to consider the torsional stiffness of the stiffeners. For this purpose, a new interpolation equation between column‐like and plate‐like behaviour is proposed, based on an extensive numerical parametric study. The proposal provides a safe and economic solution, as it considers the torsional stiffness of stiffeners when applying the rules of prEN1993‐1‐5.