Rotation Capacity of Beams under Moment Gradient

Abstract

This investigation attempts to relate the flange slenderness ratio to the rotation capacity of steel wide-flange beams subjected to a moment gradient. The steel used was CSA G 40.12, a low alloy steel having a specified minimum yield stress of 44 ksi. The reported tests were performed on simply-supported beams, subjected to a concentrated load at midspan. The flange and web geometry were varied, while the laterally unbraced slenderness ratio was held constant. All tests were continued until substantial unloading had occurred due to the effects of instability. In all cases rotation capacity was terminated by local buckling of the compression flange accompanied by large lateral deformations of the unbraced span. For beams under high moment gradient the length of the local buckle was restricted by the extent of yielding, while for beams under lower moment gradient the local buckle occupied only part of the yielded length.