Torosional buckling experimentals on wide-flange thin-walled z-section columns

Abstract

The chapter addresses the problem of mode-switching in thin-walled point-symmetric sections. It is well-known that the torsional and flexural overall buckling modes are uncoupled in point symmetric section columns, and that the minor axis flexural mode is generally critical. Theoretically, this result remains true when the section is locally buckled at incipient overall buckling. However, local buckling may change the critical mode from the minor axis flexural mode to the torsional mode. The chapter presents a series of experiments conducted to substantiate this theoretical result. Fixed-ended column tests are performed over a range of lengths on wide-flange Z-sections brake-pressed from high strength steel. Most columns failed by interaction of local buckling with overall torsional buckling and/or overall flexural buckling. Comparisons are made between the test strengths and theoretical buckling curves obtained using the theory for the overall buckling of locally buckled members.