Evaluation of Transverse Tie Rods in a 50-Year-Old Adjacent Prestressed Concrete Box Beam Bridge

Abstract

Adjacent prestressed concrete box beam bridges are one of the most popular bridges in the United States for short to medium spans. Recently, there has been concern about the structural capacity of these bridges as they age and show signs of deterioration. Unfortunately, limited research has been performed on the transverse ties because they are typically used for pulling the adjacent beam together during construction. Therefore, they are typically neglected in the overall performance of the bridge. Little, if any, information is known of the behavior and contribution of the transverse ties to load transfer and the ultimate capacity after failure of the longitudinal shear key joints. Instrumenting installed transverse tie rods has not been done in the past due to difficultly in accessing the rods, and no technique has been established to perform the installation of a sensor in the tie rods. In addition, instrumenting a tie rod that has already been installed from the fascia beam would only allow the monitoring of the rod at the outer edge of the bridge. In this study, a 50-year-old adjacent box beam bridge was instrumented and monitored under truck loading. A finite-element model was also created and verified with the field measurements. The results showed that the bridge behaved satisfactorily in transferring the load in spite of the corrosion at the exterior beams, and the tie rods did not exhibit high strain.