Buckling Strength of Single Angle Struts Part 1: Angles Subject to Axial Compression

Abstract

Hot rolled angles are classified into two categories: equal-legged and unequal legged. They behave differently when subjected to axial compression owing to the difference in section symmetry: the equal-leg angle has one axis of symmetry while the unequal-leg one is asymmetric. This article aims at providing practical approaches for determining buckling strength of the two kinds of single angle struts subject to axial compression. For equal-leg angles, the first issue of concern is the failure mode. Although most researchers agree that equal-leg single angle buckles flexurally about the minor axis in the inelastic range as well as in the elastic range, some others got different conclusion. Through meticulous analysis based on tangent modulus concept, it is shown in this study that flexural-torsional buckling about the major axis is not the dominant failure mode. On the other hand, leg plate buckling may occur before the flexural buckling. So, a factor of effective yield strength is suggested for calculating the interactive local-flexural buckling, and the approach is verified with available test data. For unequal-leg angles, which always buckle in flexural-torsional mode, attention is focused on the simplification of the formula for calculating the critical load. Simplified formula of equivalent slenderness ratio is derived to transform the flexural-torsional buckling problem into a flexural one and is verified with available test data. The results arrived at in this study are recommended for routine design use.