Testing and Evaluation of Posttensioned Concrete Beams with Bonded Curved Tendons Extracted from an Existing 50-Year-Old Viaduct

Extensive public infrastructure was built in many countries in the 1960s–1980s. As a result, in the coming decade, a large number of aging structures will require safety assessment. The structural assessment is of prime importance given the increase of loads over the last few decades, as well as outdated designs that do not satisfy the strength and detailing requirements of modern design code provisions. Particularly challenging is the shear strength assessment of prestressed concrete bridges, which nowadays is carried out according to modern shear provisions based on mechanical models. Typically, prestressed concrete structures built more than 50 years ago do not adhere to the prescribed rules because existing members possess light shear reinforcement with lacking end anchorages and tend to result in shear strength deficiency when assessed according to current codes. This paper presents the results of three full-scale tests of 1.90-m-deep posttensioned bridge girders with bonded curved tendons extracted from a 50-year-old viaduct in Belgium. The main test variable is the position of the applied point load. Global and local deformation measurements, crack diagrams, and deformed shapes at different loads were examined to establish a comprehensive picture of the behavior of the beams. It is shown that the failure of the beams is governed by concrete crushing in the top flange after yielding of the main flexural reinforcement. The girders also showed a significant reserve shear capacity not captured by shear models in current codes. Such built-in conservatism can require very disruptive and costly interventions, which are not economically and environmentally sustainable.