Torsion of Rolled Steel Sections in Building Structures

Torsional stress in a steel framed building are rarely serious enough to require design analysis. Many torsional situations can be disregarded completely. There are conceivable conditions, however, in which torsional loads can produce stresses of sufficient magnitude to require torsional analysis of a framing member. It is important, therefore, that the structural engineer understand the principles of torsional behavior in rolled steel sections, and be able to recognize those special situations in which torsional loading may be significant to the design. The purpose of this paper is to provide practical guidance to the designer in the evaluation and analysis of the effects of torsional loading on steel framing members. Design examples illustrate both a "short" approximate method of torsional analysis and a more exact method. A brief review of basic torsional theory and the torsional properties of rolled steel sections are included.