LATERAL POSTBUCKLING ANALYSIS OF BEAM-COLUMNS

The elastic lateral postbuckling response of geometrically perfect bea ms, under simultaneously uniform bending and axial compression, is exa mined in the vicinity of the critical bifurcational state. The field e quations, which include the warping effect of the cross section, are h ighly nonlinear due to the nonlinear bending-moment-curvature relation ship. The stability of the critical state associated with a stable bif urcation point is analytically established using a comprehensive appro ach. Therefore, these beam columns are not sensitive to initial imperf ections. exhibiting postbuckling strength. However, the postbuckling e quilibrium path is quite shallow (becoming more shallow with the incre ase of the axial force), so the load-carrying capacity of such beam co lumns above the critical state is rather limited. The analysis is supp lemented by illustrative examples for I-beam columns for which the eff ect of various parameters on the initial postbuckling path is also dis cussed.