Design strengths of steel beam–columns

Some of the present Canadian rules for designing steel beam–columns can be improved if different formulations are used for designing against in-plane failure and out-of-plane buckling. An extension of the present use of nonlinear elastic analysis methods allows a common formulation for the in-plane strengths of braced and unbraced beam–columns, and generally leads to predictions that are more accurate than the present forms. Two alternative methods are developed for improving the design rules for estimating the out-of-plane strengths of beam–columns. The first of these retains the present familiar form, while the second uses a new form that will lead, in some cases, to significant economies. A method is also proposed for combining the separate formulations for the in-plane and out-of-plane strengths in order to estimate the biaxial bending resistances of beam–columns. Key words: beams, buckling, columns, flexure, steel, structural design, structural engineering, torsion.