Repair, Strengthening, and Re-use of Steel Girder Bridges: Two Case Studies

Bridge repairs and strengthening techniques require careful consideration of the behavior of the structure and load paths through the repairs and construction sequencing. This presentation will discuss two case studies that required unique solutions to repair, strengthen, modify, and extend the service life of the steel superstructure, and the challenges associated with these unique solutions.

The first case study is a three-span continuous steel plate girder bridge that originally had span lengths of 59.0'-91.25'-88'.5', with all supports skewed at 13.5 degrees. To accommodate a new lane arrangement underneath the bridge, the first interior pier was relocated nearly 10 feet closer to the rear abutment, increasing the center span length. The girders were strengthened in the center span positive moment region and in the end span for negative moment, and concrete counterweights were added in the end span. Phased construction was necessary to accomplish these repairs, as one lane of traffic was maintained on the bridge.

The second case study focuses on repairs necessitated by a full-depth fracture of a fascia beam due to repetitive vehicle impacts. The bridge is a curved four-span continuous chorded steel beam bridge, with supports skewed between30 and 45 degrees, and spans of 64'-91'-84'-59'. Repair work included the replacement of the damaged beam section and connecting cross frames while providing temporary support and removing a portion of the concrete deck slab, and raising the entire superstructure. A three-dimensional LARSA finite element model was used to determine member forces, temporary support locations and reactions, and screed elevations necessary for partial deck replacement.

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