Distortional Strength and DSM Design of Cold-Formed Steel Lipped Channel Beams under Transverse Loadings

This paper reported the results of an ongoing numerical (ABAQUS shell finite element) investigation on the distortional buckling, post-buckling and ultimate strength behaviours and DSM (Direct Strength Design) Design of cold-formed steel beams subjected to major-axis non-uniform bending due to one midspan point load (transverse applied load). The beams analysed consisted of single-span lipped channel members exhibiting (i) 15 geometries, (ii) end sections that are locally and globally pinned and may warp freely, (iii) triangular bending moment diagrams, and (iv) 8 yield stresses, selected to cover a wide distortional slenderness range. After acquiring in-depth insight into how the triangular bending moment diagram influences the beam distortional buckling and post-buckling behaviours, an extensive numerical (shell finite element) parametric study is carried out in order to gather significant distortional failure moment data concerning lipped channel beams. These failure moments are then employed to assess the merits of the available DSM beam distortional strength curves in predicting them, namely (i) the one currently codified in North America (AISI 2016) and (ii) those proposed by Martins et al. (2017). The above curves were found to be inadequate for providing safe and accurate predictions of failure moments, highlighting the need to continue developing an efficient and reliable DSM-based design approach for beams failing in distortional modes under non-uniform bending.