Postbuckling mechanics in slender steel plates under pure shear: A focus on boundary conditions and load path

Slender steel plates used in buildings, bridges, aircraft, and ships have postbuckling shear strength that is mobilized in design. Despite a century of research on this topic, the mechanics (load path and failure mechanisms) of the postbuckling behavior are still not fully understood. Proper boundary conditions are vital for studying the mechanics in finite element (FE) models, yet several different boundary conditions have been proposed by researchers. This paper uses FE models to examine various boundary conditions on a slender plate under pure shear loading. The models are benchmarked against 16 experimental tests, with a range of web depths (D), panel aspect ratios, and web slenderness ratios. The effects of boundary conditions on the normal stresses on the web plate edges and principal stresses in the web are examined for panel aspect ratios of 1, 2, and 3. The flanges, stiffeners, and "panel extensions'' (which extend the web and flange a distance D/2 beyond the stiffener on either side of the panel) are used as boundary conditions (with axially free vertical edges at the ends of the panel). The analysis results show negligible participation from the stiffeners and flanges in the load path up to the ultimate postbuckling shear load, while compressive membrane stresses in the web are observed to redistribute and continue to increase after elastic buckling, in some regions at a greater rate than before buckling. This study advances the understanding of postbuckling shear load path that can be used in code development and performance enhancements for shear buckling in slender plates.