This study aims to establish a framework for design target performance and safety level for twin steel box girder bridges after a full-depth fracture in one of the girders and to outline an approach for assessing their redundancy. For the purpose of this study, a simply-supported single-span bridge tested at the University of Texas at Austin was selected as a baseline model. A detailed finite element model was developed and validated to investigate the bridge failure mode and capacity. The results of this study indicated that concrete deck failure is the dominant failure mode of the bridge after the fracture. For the first time, a comprehensive and coherent reliability approach was used to assess the safety of these bridges after the fracture. This study shows that simply supported twin steel box girder bridges could indeed be safe and potentially be removed from the fracture critical list.
