Laboratory Evaluation of Concrete Bridge Girders Flexural Strengthened with Near-surface Mounted Titanium Alloy Hooked Bars

Abstract

The use of near-surface mounted (NSM) titanium alloy bars (TiABs) has emerged as a potential solution to provide flexural strengthening to in-service, reinforced-concrete bridge girders with flexural strength deficiencies. An experimental program was performed to evaluate the behavior of large-scale, reinforced-concrete bridge girders using NSM TiABs with hooked ends for both positive- and negative-moment flexural-strengthening purposes. The experimental program involved testing four positive-moment strengthened specimens including one control specimen while also testing two TiAB types. Additionally, three negative-moment strengthened specimens were tested including one control specimen using one TiAB type. Specimens were strengthened in accordance with the AASHTO Guide for the Design of Near-surface Mounted Titanium Alloy Bars, and the requirements of ACI 318-19 were used to handle the effect of stress concentrations at TiAB termination locations. The test results indicate that flexural strengthening using NSM TiABs with hooked ends is effective when the effect of stress concentrations at the TiAB termination locations and the potential formation of inclined shear cracks in the flexural tension region are considered in the design. ACI 318-19, which has provisions to account for the impact of stress concentrations at internal reinforcement termination locations, should be used in addition to the AASHTO Guide for the Design of Near-surface Mounted Titanium Alloy Bars. Additionally, the two TiAB types that were evaluated provided similar flexural behavior and either type can be used to strengthen bridge girders.