DESIGN OF THIN-WALLED COLUMNS WITH UNSTIFFENED FLANGES

The compression member rules of the American Iron and Steel Institute, load and resistance factor design (AISI LRFD) Specification are inves tigated. It is shown that it is not necessary to limit the axial capac ity of channel, single angle and Z-section columns with unstiffened fl anges to the load causing local buckling of the flanges, as is require d in the AISI Specification. Rules are proposed which greatly improve the AISI rules for concentrically and eccentrically loaded channel sec tion columns with unstiffened flanges. The proposed rules allow the lo cal buckling coefficient of the unstiffened flanges in bending to be d etermined on the basis of a rational buckling analysis when bending ca uses compression at the free edge of the unstiffened flanges. When ben ding causes tension at the free edge of the flanges, the proposed rule s allow the flanges to be treated as stiffened elements.