Methods for strengthening flexural steel details in reinforced concrete bridge girders using a near-surface mounted retrofitting technique

Graduation date: 2015Many older reinforced concrete deck girder (RCDG) bridges contain straight bar terminations of flexural reinforcement. Common bridge design practice of the 1950s did not consider the additional demands on the terminated bars from shear and flexure. Moreover, more stringent code specifications and heavier permit trucks contribute to the insufficient ratings and presence of diagonal cracks in RCDG bridges. Replacement of these bridges is not economically feasible and thus strengthening methods are necessary.\ud \ud The goal of this research was to investigate anchorage strengthening methods using full-scale vintage girder specimens. The specimens were constructed with a flexural anchorage deficiency by terminating two flexural bars that extended only one-third of their development length past a 45° preformed diagonal crack.\ud \ud A common flexural strengthening technique called near-surface mounting (NSM) was applied to T-specimens. Two metallic materials were selected for the NSM reinforcement: titanium and stainless steel. These materials were chosen because of their high strength, ductility, environmental durability, and ability to fabricate mechanical anchorages. This study found that the NSM strengthening technique with metallic materials increased the midspan displacement by at least 85%, and load capacity by at least 31% for each specimen. In addition, a case study was performed to simulate the positive moment anchorage strengthening of the Mosier Bridge in Oregon