Lateral distortional buckling of monosymmetric I-beams under distributed vertical load

Abstract

An energy method is developed for analyzing the lateral buckling behaviour of beams subjected to distributed vertical load, with full allowance for distortion of the web. The paper presents a simple method which uses nonlinear elastic theory to obtain the external work due to buckling, and which obtains a new formulation of total potential energy for a monosymmetric I-beam. The method is validated by comparison with the classical energy methods when distortion of the web is suppressed (rigid web case). For both uniform distributed load and end moments the solution matches the critical lateral load obtained from the classical energy equations. For the case when the web is flexible, a 5th order polynomial shape function is used to describe the web buckling shape. The accuracy of the method is verified by results obtained from ABA QUS. The paper shows that for short beams the classical method seriously overestimates the critical load.