Inelastic Buckling Gradient

The inelastic buckling gradient is defined in relation to the behavior of a geometrically perfect column, considering both the continuously strain-hardening material (typified by a structural aluminum alloy) and structural steel in the presence of residual stress. For the continuously strain-hardening material and for a column of monosymmetric cross section, buckling in the plane of symmetry may be initiated in either direction. However, inelastic buckling gradient will have different values for buckling in the alternative directions. A tee section, buckling with the flange on the convex side (with the lesser buckling gradient), will become increasingly stable with respect to lateral buckling out of the plane of symmetry, provided that inelastic lateral-torsional buckling does not develop. Buckling with the flange on the concave side will lead to inelastic lateral and torsional instability before reaching the maximum load obtainable with full lateral and torsional support. Formulas for the inelastic buckling gradient of structural steel columns with initial residual stresses are developed.