Experimental and Analytical Evaluation of Residual Capacity of Corrosion-Damaged Prestressed Concrete Bridge Girders

About the report:

The durability of infrastructure components, such as prestressed concrete bridge beams, can be significantly affected by long-term deterioration associated with corrosion.  Corrosion is a major concern for bridges in Virginia, due to the frequent use of deicing salts during the winter, as well as the number of structures in marine environments.  The residual capacity of corrosion damaged prestressed I-beams and box beams needs to be accurately estimated to determine if damaged bridges need to be posted, and to help with making informed decisions related to repair, rehabilitation and replacement of damaged bridges.

This report presents the results of testing of six corrosion-damaged prestressed beams removed from existing bridges during their demolition.  Three beams were Type II AASHTO I-beams extracted from the Lesner Bridge in Virginia Beach, and three were 48 in wide by 27 in deep box beams extracted from the Aden Road Bridge near Quantico, Virginia. Prior to testing, the beams were visually inspected and two types of non-destructive evaluations were performed to identify corrosion activity: resistivity measurements and half-cell potential measurements.  The beams were then tested in the lab to determine their flexural strength. Following testing, samples of strand were removed and tested to determine their tensile properties. Cores were taken from the Aden Road beams and from both the beams and decks of the Lesner Bridge beams to determine compressive strength.  Powdered concrete samples were removed to perform chloride concentration tests.

The tested strengths of the beams were compared to calculated strengths using two methods for damage estimation and two different calculation approaches.  The methods for damage estimation relied exclusively on visual inspections; one was the set of methods recommended by Naito et al. (2010), while the second was a modified method developed in this study from the current tests.  The two calculation approaches were a strain compatibility method and the AASHTO LRFD method.  Overall, the results yielded reasonable estimates of residual strength, except for one of the box beams that was discovered to have considerable water within the hollow cells.  The final recommendations are that bridge inspectors develop detailed damage maps of corrosion-damaged beams, and that load raters use the Naito et al. method to get a conservative estimate of damage for both box beams and I-beams.  Either method for calculating strength is valid, however the AASHTO LRFD method is simpler.

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