Book Description

Catastrophic failures of non-composite prestressed precast concrete adjacent-box beam bridges have occurred in several states due to corrosion of the prestressing steel. These failures have highlighted the need to improve methods used to detect corrosion damage and subsequently load rate the damaged members. In light of this, PennDOT initiated a research program aimed at improving inspection techniques through evaluation of off-the-shelf non-destructive testing (NDT) technologies and correlation of surface conditions with non-visible strand corrosion. Funding for the project was provided by the departments of transportation of Pennsylvania (the lead agency), New York, and Illinois. Currently, the inspection of concrete box girder sections relies on visual methods which correlate longitudinal and transverse cracking, spalling, and exposed strands with the rated level of performance of the member. While the visual method provides a qualitative estimate of the amount of damage, the specific location along a strand and the amount of damage to the strands is not clearly defined. As a result, the assessment of the condition of the bridge could in some cases result in an un-conservative or overly-conservative estimate of remaining strength. Furthermore, without a high level of accuracy in locating damage to the strands, remediation and rehabilitation is difficult to accomplish. To improve on the current inspection techniques the visual inspection requirements are revisited through an extensive destructive evaluation study. In addition, NDT methods are evaluated and compared with actual damage present in a group of 40- 50 year old box beams removed from service. The goal of this project is to determine if visual inspection techniques or currently available NDT technologies will allow for accurate identification of non-visible corrosion of prestressing strands.