Further Studies of the Strength of Beam-Columns

To afford a larger number of “exact solutions” for comparison with approximate interaction curve expressions, this paper presents the results of a continuing investigation of the ultimate carrying capacity of beam-columns. Two basically different loading conditions have been examined, and the results have been presented in interaction curve form. The first of the assumed loading conditions is that of a column subjected to an axial thrust and end moments M₀ and β M₀. The values of β that have been considered are +1.0, +0.5, 0, −0.5 and −1.0. The maximum strengths of columns subjected to lateral loads applied at their center-line sections have also been determined. In all cases it has been assumed that the member is an “as-rolled” wide-flange shape that is subjected to bending moments in the plane of its web. It has further been assumed that the member is constrained to deform only in the plane of the web. Failure is therefore characterized by “excessive bending” in the plane of the applied moments. For the case in which the imposed moments result in a double curvature type of deformation, the possibility of “unwinding” and thereby failing in a single curvature mode exists. A method for the examination of this situation is discussed and the presented interaction curves include this possibility.