Column Design in Steel Frames under Gravity Loads

In the last two or three decades, several methods have been proposed for the design of columns in steel rigid frames under gravity loads; one of them was proposed by Yura in 1971. In this note it is shown that Yura's method, adequate when applied to ordinary regular structures, can be overconservative in special cases, as it does not take adequately into account several important features of the problem. A new method is presented, based on the determination of the lateral stiffness of the frame or story under consideration, which takes into account both PΔ and P° second-order geometrical effects. The method is general in scope, does not require the use of K factors, and has the advantage that the frame or story first-order lateral stiffness can be easily computed with the information given by all commercial computer programs for structural analysis. The proposed method is compared with design methods available in the literature through its application to several numerical examples.