Bifurcation of locally buckled channel columns

Abstract

The report derives the governing equations for the fundamental and bifurcated states of members with singly symmetric cross-sections that locally buckle in the fundamental state. The members are subject to pure compression and assumed to be geometrically perfect in the overall sense. The method of analysis uses elastic and inelastic geometric nonlinear finite strip buckling analyses to determine the tangent rigidities of the locally buckled section. These rigidities are substituted into the equations for overall flexural and flexural-torsional buckling to obtain the bifurcation loads. The effect of yielding is highlighted through a parametric study. The overall bifurcation loads are compared with a series of tests of fixed-ended plain channel columns. The variation of the bifurcation loads with the length is shown to be in good agreement with the tests. The bifurcation loads are shown to be sensitive to the magnitudes of local and overall geometric imperfections.