Patch load resistance of longitudinally stiffened steel plate girders: A parametric study

In this paper, an in-depth nonlinear finite element analysis is carried out on longitudinally unstiffened and stiffened welded I-steel plate girders subjected to patch loading. The most realistic load case is during the incremental launching of multi-span steel and composite bridges over temporary or permanent supports. Bridge plate girders are usually reinforced by longitudinal and transverse stiffeners in order to prevent web panel buckling and to increase the bending and shear strength. The current European design standard EN 1993-1-5 also requires a stability control check for concentrated transverse forces (patch loading) since it can be a decisive design criterion. By using longitudinal stiffeners for flexural and shear resistance, the patch loading carrying capacity can be increased as well. Previous experimental studies showed that the EN1993-1-5 patch loading resistance model significantly underestimates the ultimate strength of longitudinally stiffened plate girders. The paper is primarily dealing with numerical research of the post-buckling behavior and ultimate strength of longitudinally stiffened I-steel plate girders reinforced by one longitudinal stiffener. The main objective of the present work is to investigate the influence of different geometrical parameters, including patch load length, web panel aspect ratio, and initial geometrical imperfections, on the ultimate strength of longitudinally stiffened plate girders. We showed in this study that for all the considered initial geometrical imperfections, the patch load resistance increases as the patch load length is increased. The lowest ultimate strength of longitudinally stiffened plate girders was determined for initial geometrical imperfections that resembled the deformed shape at collapse (collapse-affine imperfections). The web panel aspect ratio also influenced the patch load resistance and lower ultimate strengths were returned for bigger web panel aspect ratios. Finally, further research recommendations are presented. © 2021 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.