Field and Analytical Studies of the First Folded-Plate Girder Bridge

An innovative bridge that includes prefabricated folded-plate girders (FPGs), precast-posttensioned lower sections of the integral abutments, and a precast T-wall gravity wingwall system is studied. Some results are specific to the girder system, but others can be generalized to single-span integral-abutment bridges and to the durability of prefabricated elements. Data were collected during construction, static live-load testing, and long-term monitoring and were compared to finite-element modeling. Stresses in concrete and steel components remained low throughout construction, long-term data collection, and truck-load testing. Live-load test data indicate that the elastic neutral axis of the FPG is higher than that calculated and that positive shear lag (nonuniform girder flange stress) is observed under localized point loads. Limiting the movement of the wingwall and directing attention to the curing of cast-in-place elements would further improve the quality of future bridges. Observations on the daily thermal gradient are applicable to other single-span integral abutment bridges and show that reversed thermal gradient (superimposing day strains from a warmer deck than girder on cold days and night strains from a cooler deck on warm days) can lead to higher girder stresses than those observed on the hottest or coldest days.