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This paper concerns the Eurocode 3 Part 1-3 (EN 1993-1-3) methods for calculating the distortional buckling (bifurcation) load of cold-formed steel-lipped channels subjected to axial force, major and minor axis bending. More specifically, the paper presents the results of a parametric study that assesses the accuracy of the simplified method in EN 1993-1-3, which relies on direct/iterative hand calculations and an approximate mechanical model, through comparison with "exact" numerical results, obtained using semi-analytical linearized buckling analyses based on Generalized Beam Theory, which are also allowed by the code. Isoline error maps are presented for a wide range of geometric and material parameters, covering common commercial profiles and corresponding to a dataset of more than 24,000 cases. These maps make it possible to identify the parameter ranges leading to an acceptable error and, even though they strongly depend on the loading, general remarks concerning the expected error pertaining to the simplified method are drawn. [ABSTRACT FROM AUTHOR]

This paper concerns the Eurocode 3 Part 1-3 (EN 1993-1-3) methods for calculating the distortional buckling (bifurcation) load of cold-formed steel-lipped channels subjected to axial force, major and minor axis bending. More specifically, the paper presents the results of a parametric study that assesses the accuracy of the simplified method in EN 1993-1-3, which relies on direct/iterative hand calculations and an approximate mechanical model, through comparison with “exact” numerical results, obtained using semi-analytical linearized buckling analyses based on Generalized Beam Theory, which are also allowed by the code. Isoline error maps are presented for a wide range of geometric and material parameters, covering common commercial profiles and corresponding to a dataset of more than 24,000 cases. These maps make it possible to identify the parameter ranges leading to an acceptable error and, even though they strongly depend on the loading, general remarks concerning the expected error pertaining to the simplified method are drawn.

This paper presents an energy‐based approach to obtain the critical length and stress of local (L) and anti‐symmetric distortional (D2) modes of simply supported lipped channel columns. For each mode, deformed shapes are assumed and the Rayleigh Quotient Method is applied to obtain analytical expressions for the buckling stress. The shape functions adopted for local buckling ensure compatibility of rotation and bending moments at wall junctions and at the stiffener's free end. For the D2 mode, equilibrium of bending and twisting moments are considered leading to an analytical derivation of the mode's warping stress distribution. While for L mode it is not feasible to obtain a closed expression for the critical length (but a simple length testing procedure is sufficient), for D2 mode an expression dependent on geometrical properties is derived. The developed equations for L and D2 modes are validated against CUFSM's pure local modes and GBTul's pure D2 mode (mode 6 in GBTul convention) respectively. For sections with flange‐to‐web width ratio, bf/bw, ranging from 0.2 to 1.0 and lip‐to‐web width ratio, bs/bw, from 0.1 to 0.4 the average ratios obtained for critical stresses (σcr,reference/σcr,proposed) are 1.014±0.019 and 1.011 ± 0.014 for L and D2 modes respectively. [ABSTRACT FROM AUTHOR]