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The buckling deformations (deflections) all lie in one of the principal planes of the column cross-section. No twisting of the cross-section occurs for flexural buckling.
The limit state of flexural buckling is applicable for axially loaded columns with, doubly symmetric sections such as bars, HSS and round HSS, and I-shapes and singly symmetric sections, such as T- and U-shapes. Flexural buckling is the simplest type of buckling.
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The buckling deformations consist of a combination of twisting and bending about two flexural axes of the member.
The symmetry axis is the y-axis, where the buckling around the y-axis is caused by the tilting and rotation of the element around its longitudinal axis. The limit state of flexural-torsional buckling is applicable to columns with singly symmetric shapes, such as double angle, T- and U-shapes and asymmetric cross-sections.
Design with AISC 360-16
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