Experimental Rotation Capacity of Steel Beam-Columns

The results of 31 tests on small scale mild-steel I-section stanchions are presented. The specimens were loaded by a constant axial load and bending moment acting at one end in the plane of the web. Minor axis and longitudinal rotations were prevented at both ends; the minor axis slenderness ratio varied between 75 and 195. Two sections were used, both rather thick-walled, so that there was no danger of local buckling. Consequently, failure occurred by either excessive (in-plane) bending or lateral-torsional buckling, mostly in the plastic range. A stiff bending device allowed the moment-rotation curve to be followed in the falling part of the curve. The experimental rotation capacity, defined as the angle of plastic rotation at nine-tenths of the maximum (collapse) moment has thus been obtained for each specimen. These rotation capacities, plotted versus the axial load and the slenderness ratio, suggest a regular pattern, irrespective of the type of failure which is similar to the theoretical pattern obtained by other authors. No theoretical analysis of the results is developed.