Reliability and Redundancy of Two-Girder, Steel-Concrete Composite Bridges under Uncertainty

As the bridge inventory ages and traffic volumes increase, the bridge owners are spending more on maintaining their current structures. AASHTO considers virtually all two-girder bridge systems as non-redundant, and each girder is considered as the fracture-critical member (FCM). Redundancy analysis of the two-girder bridges considering the uncertainty (damage scenarios) is investigated through a case study on a three-span, continuous twin I-girder bridge. The FE analysis is employed to evaluate the load-carrying capacity after fracture of one main girder of the twin girder bridge. The damage locations are chosen at the mid-span section of the middle span, the side span, and the section near the continuous pier support. Damage to shear connectors near the moment contra-flexure regions and missing one bearing at the middle and end support locations are also considered as potential damage scenarios in this study. On the basis of the direct redundancy analysis results, the present continuous two-girder composite bridge can be classified as redundant.