Ag : Gross cross-sectional area of member

Ae : Effective area

c1, c2 : Effective width imperfection adjustment factor determined from Table E7.1

Fcr : Critical stress

Fe : Elastic buckling stress determined according to Equation E3-4,

Fy : Specified minimum yield stress of the type of steel being used,

K : Effective length factor

L: Laterally unbraced length of the member

Lc : Effective length of member, (= KL)

r: Radius of gyration

λ: Width-to-thickness ratio for the element as defined in Section B4.1

λr : Limiting width-to-thickness ratio as defined in Table B4.1a

Flexural Buckling Limit State

  • 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.

Design with AISC 360-16

  • The compressive strength of the elements is determined according to the axial force acting from the section center of gravity. According to the regulation, the flexural buckling limit state is taken into account in all compression elements, regardless of cross-section properties. The equations used for this are given below in order.

  • First of all, local buckling control should be done. The calculation is made to determine whether the elements are compact or non-compact.

Flexural Buckling Members without Slender Elements

Flexural Buckling Members with Slender Elements

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Torsional Buckling