Visual Rating and Strength Testing of 40-Year-Old Precast Prestressed Concrete Bridge Piling

Abstract

The rating of bridge piles is primarily visual and requires judgment to quantify damage levels and, ultimately, to estimate the pile's remaining structural capacity. A series of tests was run to evaluate the existing capacity of piles that have been in service in a harsh saltwater environment for more than 40 years. In 2004, the Bryant Patton Bridge over Apalachicola Bay in the Florida Panhandle was replaced with a new bridge. The original bridge, which was demolished as part of the construction project, was constructed in 1963. During demolition, 12 pre-stressed concrete piles with varying levels of corrosion damage were recovered. Two of the selected piles were equipped with cathodic protection at the time of their installation in 1994 as part of a repair project that involved most of the pilings supporting the bridge. Visual inspections were conducted by Florida Department of Transportation divers on the selected piles before they were removed. After recovery of the piles, they were cleaned and flexurally tested to failure in a four-point bending test. The results of the flexural tests are presented along with a visual rating of the piles from the divers’ inspection. Flexural capacities of the existing piles were compared with the calculated moment capacities and the undamaged flexural capacities (determined from testing). A few piles that showed little outward sign of damage had a severe reduction in the actual flexural capacity, indicating that assessments by visual inspection do not necessarily correlate well with the actual flexural capacity of piles.