Analytical Study on Flexural Ductility Performance of Steel Girder Bridges

In this study, 3 dimensional nonlinear finite element analyses was conducted to investigate the ultimate strength and flexural ductility performance of steel box girders fabricated with mild steel and high strength steel. It was also examined the applicability of current LRFD design specifications of compactness for the box girders. Analysis for the full-scale box girder models subjected pure bending were conducted to investigate the behavior of members with a variety of slenderness of panels due to one or more longitudinal stiffeners that divided the panel. Several variables were also considered in the analysis such as the web slenderness, the stiffness of longitudinal and transverse stiffener, the distance of transverse stiffener. It was confirmed that the slenderness (w/t) of sub-panels, the stiffness of longitudinal stiffeners, and the slenderness of webs are the key parameter governing the ductility of box girders. However, the finite element analysis results indicated that steel box girders fabricated from high strength steel and designed to meet or exceed the current LRFD compact slenderness limits may not attain the required flexural ductility and rotation capacity necessary to be compact section. It is recommended that the improved design provisions are needed for the ductility of high strength steel box girders.