Out-of-flatness of steel plate girder webs, Part II: Shear strength and behavior

This paper presents a series of validated finite element (FE) models geared to parametrically examine the effects of initial web out-of-flatness imperfections on the shear strength and behavior of steel plate girders under pure shear. The prototype girder models are based on field measured imperfection shapes and magnitudes, with variations in web slenderness (93, 109, and 118) and panel aspect ratio (0.89, 2.02, 2.22, and 2.29). Additional model cases are analyzed by incorporating idealized eigenmode shapes and scaled to web out-of-flatness tolerance limits per AASHTO/AWS D1.5. The FE strength results are compared against various code-based nominal shear strength predictions. The following key findings are derived: (1) field measured and eigenmode imperfections exhibit similar shear behavior and deformation response throughout all shear mechanism stages; (2) the yield mechanism of a stiffened web panel in shear is negligibly impacted by the initial imperfections of the web and is triggered by second-order flexural bending from in-plane shear-induced compression; (3) an initial imperfection with an eigenmode shape and a maximum magnitude ranging from d/300 to d/600 (where d equals to the least panel dimension) can suitably approximate the shear strength of plate girders when compared with field measured imperfections; and (4) code-based nominal shear strength predictions demonstrate to be conservative for web panel aspect ratios ≥2.0.