Classifying Cyclic Buckling Modes of Steel Wide-Flange Columns under Cyclic Loading

Wide-flange sections are routinely used for the construction of seismic force-resisting systems in the U.S. For braced frames, shallow, stocky sections are commonly used. However, deep sections are used nowadays in order to achieve economy when designing moment frames. Recent cyclic testing of deep, slender steel columns under varying degrees of axial compression showed that the failure mode can be very different between shallow and deep sections. Since the hysteretic response of a column is associated with the governing failure mode, for analytical modelling purposes it is essential that a straightforward criterion be established to identify the governing buckling mode. This paper proposes one criterion based on the full-scale test results. The proposed criterion is also verified by finite element simulation of wide-flange columns with a wide range of geometric properties.