Design of steel wide-flange members for torsion applied through one flange

In industrial structures, it is common for steel wide-flange members to be subjected to torsional moments, which when applied through one flange can cause local cross-sectional distortion. Even when these moments are relatively small, the pragmatic design solution often chosen is to install stiffeners at the joint to engage the entire cross-section. However, these stiffeners may add unnecessary costs, which can be a significant portion of the overall cost of the structure in some cases. As such, elimination of these stiffeners wherever justifiable is desirable from an economic standpoint. Behaviour of unstiffened wide-flange members subjected to torsional loading through one flange is explored in this paper. Parametric numerical analysis studies have been performed to distinguish the effects of cross-sectional dimensions on the response of the member. In addition, nine full-scale laboratory tests were conducted to further the existing knowledge. The results of these studies provide the basis of a design procedure presented for determining whether or not the applied torque can be resisted locally without installing stiffeners.