The Hampton Roads Bridge-Tunnel is one of the oldest prestressed concrete structures in the United States. The 3.5 mile long twin structure includes the world's first underwater tunnel between two man-made islands. Throughout its 60 years in service, the harsh environment along the Virginia coast has taken its toll on the main load carrying girders. Concrete spalling has exposed prestressing strands within the girders allowing corrosion to spread. Some of the more damaged girders have prestressing strands that have completely severed due to the extensive corrosion. The deterioration has caused select girders to fail the necessary load ratings. The structure acts as an evacuation route for the coast and is a main link for the local Norfolk Naval Base and surrounding industry. Because of these constraints, load posting is not a viable option. Live load testing of five spans was performed to investigate the behavior of the damaged spans. Innovative techniques were used during the load test including a wireless system to measure strains. Two different deflection systems were implemented on the spans, which were located about one mile offshore. The deflection data was later compared head to head. From the load test results, live load distribution factors were developed for both damaged and undamaged girders. The data was also used by the local Department of Transportation to validate computer models in an effort to help pass the load rating. Overall, this research was at the forefront of the residual strength of prestressed concrete girders and the testing of in-service bridges. / Master of Science / According to Federal law, each bridge across the United States must be inspected by a licensed engineer on a biennial cycle – meaning every two years. Roughly every ten years, or when major work is performed such as a bridge widening, a load rating must be performed. During a load rating, licensed structural engineers analyze every structural component of a bridge under various loads. These loads include general traffic loads, heavy design loads, as well as special permit truck loads. For each of these loadings, it is proven whether each structural component has enough strength to withstand the load entering the member. Inspection reports are incorporated into the load rating analysis to account for any deterioration in the members which will lower its strength. Recently, a load rating was performed on the Hampton Roads Bridge-Tunnel. The Bridge-Tunnel is a 3.5 mile long twin structure located in Southeastern Virginia. Throughout its 60 years in service, the harsh coastal environment has caused extensive deterioration to some of its main load carrying girders. The deterioration has caused the Bridge-Tunnel to fail its load ratings meaning load posting may have to be imposed. This means signs, and possibly security guards, would have to be implemented before the approach ramps preventing trucks over a certain weight limit from entering. The structure acts as an evacuation route for the coast and is a main link for the local Norfolk Naval Base and surrounding industry. Because of these constraints, load posting is not a viable option. The Bridge-Tunnel is one of the oldest structures of its type so the effects of the deterioration are not well understood causing conservative assumptions to be used within the load rating. This research describes load testing that was performed on the structure to understand the performance and deterioration effects of the bridge. The results and recommendations from this research were used by the load rating engineers to justify assumptions made and help pass the load rating.

Adjacent precast, prestressed box beam bridges have a history of poor performance and have been observed to exhibit common types of deterioration including longitudinal cracking, concrete spalling, and deterioration of the concrete top flange. The nature of these types of deterioration leads to uncertainty of the extent and effect of deterioration on structural behavior. Due to limitations in previous research and understanding of the strength of deteriorated box beam bridges, conservative assumptions are being made for the assessment and load rating of these bridges. Furthermore, the design of new box beam bridges, which can offer an efficient and economical solution, is often discouraged due to poor past performance. Therefore, the objective of this research is to develop improved recommendations for the inspection, load rating, and design of adjacent box beam bridges. Through a series of bridge inspections, deteriorated box beams were identified and acquired for experimental testing. The extent of corrosion was determined through visual inspection, non-destructive evaluation, and destructive evaluation. Non-destructive tests (NDT) included the use of connectionless electrical pulse response analysis (CEPRA), ground penetrating radar (GPR), and half-cell potentials. The deteriorated capacity was determined through structural testing, and an analysis procedure was developed to estimate deteriorated behavior. A rehabilitation procedure was also developed to restore load transfer of adjacent beams in cases where shear key failures are suspected. Based on the understanding of deterioration developed through study of deteriorated adjacent box beam bridges, improved inspection and load rating procedure are provided along with design recommendations for the next generation of box beam bridges.