LATERAL POSTBUCKLING ANALYSIS OF BEAM-COLUMNS

The elastic lateral postbuckling response of geometrically perfect beams, under simultaneously uniform bending and axial compression, is examined in the vicinity of the critical bifurcational state. The field equations, which include the warping effect of the cross section, are highly nonlinear due to the nonlinear bending-moment-curvature relationship. The stability of the critical state associated with a stable bifurcation point is analytically established using a comprehensive approach. Therefore, these beam columns are not sensitive to initial imperfections. exhibiting postbuckling strength. However, the postbuckling equilibrium path is quite shallow (becoming more shallow with the increase of the axial force), so the load-carrying capacity of such beam columns above the critical state is rather limited. The analysis is supplemented by illustrative examples for I-beam columns for which the effect of various parameters on the initial postbuckling path is also discussed.