Numerical study on post-fracture redundancy of the two-girder steel-concrete composite highway bridges

As the Japan bridge inventory ages and traffic volumes increase, the government is spending more on maintaining their existing structures to extend the service life of the current bridge inventory. This includes two-girder bridges that are classified as fracture critical and non-redundant. Owing to the increased inspection costs associated with these fracture-critical bridges, there is a need to evaluate alternate load paths and to implement retrofit methods on existing bridge structures to avoid bridge replacement. In this paper, fracture redundancy of the two-girder bridge is investigated through a case study for a three-span continuous twin I-girder bridge. The finite element analysis is carried out to evaluate the load-carrying capacity after fracture of a girder of the two-girder bridge. Damage of studs near the moment contra-flexure regions are also considered in this study. Spacing between the transverse beams is discussed as possible techniques to improve redundancy and reduce the fracture potential of two-girder bridge structures. The concrete slab is indicated to be a significant member for guarantying the redundancy of the two-girder steel-concrete composite bridges.