Bifurcation of locally buckled point symmetric columns—Experimental investigations

The bifurcation equations for locally buckled point symmetric sections are derived in a companion paper [Rasmussen KJR. Bifurcation of locally buckled point symmetric columns—analytical developments. Thin-walled Struct, submitted for publication]. In the present paper, two series of experiments are reported, one on narrow flange Z-sections and one on wide flange Z-sections. The main objective of the tests was to validate the bifurcation load predictions derived in [Rasmussen KJR. Bifurcation of locally buckled point symmetric columns—analytical developments. Thin-walled Struct, submitted for publication] against experimental values. A further objective of the tests on narrow flange sections was to investigate the change in the direction of overall buckling, as predicted by the theory, from principal axis directions to non-principal directions. A further objective of the tests on wide flange sections was to investigate the possible change of the critical overall buckling mode from a flexural mode to a torsional mode as a result of local buckling. Agreement is generally found between analytical and experimental results.