Torsional Stiffening of I-Girder Webs

The torsional response of box stiffened I-sections has been predicted by two analytical procedures. These methods utilize basic torsion theory and compatibility relationships. One method (approximate) is only applicable for L/a≤1.0 The other method (exact) is valid for all ranges of L/a. The analytical results for a cantilever stiffened beam are compared to experiments test giving excellent correlation. The results indicate that one stiffener can reduce rotations by 44% and two stiffeners by 55%. The induced warping stress is reduced by 20% and 30% for one and two stiffeners, respectively. A study of a fixed-fixed beam in uniform torsion with one stiffener, has shown that rotations are reduced by 50% and warping stress by 25%. The pinned-pinned beam response to uniform load and one stiffener gave a reduction of 25% in rotation and 50% in warping.