Inelastic Lateral Buckling of Beam‐Columns

Abstract

An accurate line model based on the finite‐element method is developed for analyzing the inelastic lateral buckling of I‐section beams and beam‐columns. The prebuckling in‐plane bending is analyzed using a geometrically nonlinear finite‐element method that accounts for the effects of prebuckling displacements and residual stresses on yielding. The results of the prebuckling analysis allow the distributions of yielding and strain‐hardening throughout the beam to be determined. The out‐of‐plane flexural‐torsional buckling of the inelastic beam is analyzed by adapting an elastic tapered monosymmetric finite element. For this element, the deflections and twists are referred to an arbitrary straightline axis along the midheight of the web, instead of the shear center or centroidal axes. The elastic element is adapted for inelastic buckling by using reduced out‐of‐plane stiffnesses that allow for yielding and strainhardening. The method is used to give some indications of the accuracy of earlier studies based on less accurate assumptions.