Cyclic behavior of steel wide-flange columns subjected to large drift

During an earthquake, steel braced frame columns can be subjected to high axial forces combined with inelastic rotation demand resulting from story drift. Cyclic testing of nine full-scale W14 column specimens representing a practical range of flange and web width-to-thickness ratios were subjected to different levels of axial force demand (35, 55, and 75% of nominal axial yield strength) combined with up to 10% story drift. No global buckling was observed in all test specimens. Flange local buckling was the dominant buckling mode. Specimens achieved interstory drift capacities of 0.07-0.09 rad. These large deformation capacities were, in part, achieved due to the delay in flange local buckling resulting from the stabilizing effect provided by the stocky column web of the W14 section specimens. Testing indicated that the ASCE 41 predicted plastic rotation capacities are very conservative. The ASCE 41 criteria do not specify plastic rotation capacity at axial load ratios greater than 0.5; however, tested specimens exhibited significant plastic rotation capacities of approximately 15-25 times the member yield rotation.