Flexural and Flexural-Torsional bifurcation of locally buckled beam-columns

摘要

The paper describes the overall bifurcation behaviour of locally buckled I- sections in combined compression and major axis bending. The overall bifurcation loads are calculated using the tangent rigidities of the locally buckled cross-section for minor axis flexure and warping torsion. The expression for the overall bifurcation load is analytic while the tangent rigidities are calculated numerically using an elastic nonlinear finite strip local bucklinng analysis. It is shown that while the interaction curves for local buckling and overall flexural-torsional buckling of the undistorted cross-section are convex, the interaction curves for the flexural torsional bifurcation of locally buckled beam-columns may be convex, linear or concave depending on the cross-section geometry and the extent of local buckling.