Buckling of Beams with Concentrated Moments

Abstract

Present methods for approximating the elastic lateral buckling load of a continuous beam are unnecessarily conservative when the beam is loaded by concentrated moments. This is because the significant warping restraints which may develop at points of concentrated moment are neglected. In this paper, an improved approximate method is developed which allows for these warping restraints. The method uses an effective length concept to allow for the warping and minor axis flexural interactions between adjacent segments at brace points and supports. The warping restraint effective length factors are estimated from the concentrated moments and the anti‐symmetry of the bending moment distribution about the brace point, and initial estimates are made of the buckling loads of the individual segments. These estimates are then improved by allowing approximately for the flexural interaction between adjacent segments. The accuracy of the new method is demonstrated for a wide variety of cases.