Simple Model for Shear Capacity of Webs

Abstract

The ultimate load capacity of shear webs in a plate girder is modeled as the sum of the contributions of the web and the flanges. After initial elastic buckling due to a uniformly distributed shear stress, the web provides an increasing shear resistance by virtue of a changing shear stress distribution along the boundary, in which the shear stress remains at the critical stress in the compression corner, and increases toward the tension corner until shear yielding occurs. At this point, there is no stress normal to any boundary. As the web yields and distorts in the tension corners, the flanges are compelled to bend, and their resistance creates a normal force between the flange and web at the boundary, making an additional contribution to the shear capacity. Design expressions based on this model of the collapse mechanism give a direct prediction of the ultimate shear force, with no need for empirical adjustments.