Evaluation of Elastic Local Buckling Strength of Lipped Channel Section Members Considering Shear Bending Interaction

Recently in Japan, thin-walled cold-formed steel with thickness less than 2.3 mm is commonly used in steel houses. Lipped channel section member is one of the typical cross-sections. The members have large width–thickness ratios which cause elastic local buckling. The buckling determines the post-buckling behaviours and ultimate strength. Therefore, it is important to investigate the buckling strength to accurately evaluate the structural performance of the members.

The several previous studies on the elastic local buckling strength of lipped channel section members under shear bending have been conducted. For example, the buckling strength is analytically examined by finite element method. However, the buckling strength is not theoretically examined sufficiently. Especially, the coupled effects of plate elements are not sufficiently understood.

The purpose of this paper is to evaluate the elastic local buckling strength of lipped channel section members under shear bending. The buckling strength of 5 all plate elements is theoretically derived by energy method considering shear bending interaction and coupled effects of plate elements. The effects of loading conditions, member shapes, and boundary conditions (simply supported/considering coupled effects/elastically supported/clamped along longitudinal edges) on the buckling strength and buckling modes are investigated. It is revealed that consideration of coupled effects of plate elements is necessary, and the buckling strength increases due to shear bending interaction and complicatedly changes due to the flange-web and lip-web aspect ratios. Reasonable approximations for the buckling coefficients corresponding to the gradient of bending moment, aspect ratio of member length, and flange-web aspect ratio, and lip-web aspect ratio are presented. Furthermore, using the general-purpose FEM program Abaqus, the elastic buckling modes such as local buckling, distortional buckling, and torsional buckling are also investigated. Finally, the application range of the provided evaluation is defined.