Full-scale testing and analysis of 20-year-old pretensioned concrete box girders

This research covers the testing of 2 full-scale precast, pretensioned box girders. The girders were removed from an existing bridge in Reno, Nevada, and had been in service for 20 years. The overall length of the girders was approximately 21.34 m (70 ft). The girders were tested monotonically to failure, while monitoring strain profiles deflection crack opening, and strand strain. Several methods were used to test the remaining level of prestress in the girders. Ultimate moments and measured level of prestress were compared to code equations. Measured ductility was compared to ductility behavior as predicted by the code by considering strain profiles, ultimate deflection, and ultimate concrete strain. There was good agreement between code predicted and measured ultimate load. However both ductility and prestress loss differed significantly from code predictions. Explanations for these differences are proposed in the main body of this paper.