Torsional Bracing of Columns

Abstract

Many column bracing details employed in steel construction do not prevent twist, and subsequently, torsional buckling may control the column capacity. This mode of buckling is not adequately considered in design codes and is often overlooked. This paper documents a finite-element investigation of the torsional buckling behavior of columns with lateral bracing located at different points on the cross section. The location of the lateral bracing on the cross section has a significant effect on torsional buckling. Equations are developed for the stiffness and strength requirements of bracing to control torsional buckling. Details for torsional bracing are discussed and presented. A connection detail must be provided between the column and the brace that controls cross-sectional distortion. A design example illustrates the use of the bracing recommendations.