Corrosion Investigation, Evaluation, and Pier Replacement Scheme for the Long Key Bridge

Abstract

Reconstruction of U.S. Highway 1 from Miami to Key West, Florida, marked the first use of epoxy-coated reinforcing in several new bridges in Florida, including the Long Key Bridge. Since then, increasing corrosion has been found in all splash zones. The novel V-piers of the Long Key Bridge received much attention; nevertheless, the superstructure, upper parts of the V-piers, and fully submerged and cased drilled shaft foundations have no corrosion at all. In 1996, a corrosion investigation was undertaken to determine the mechanisms and rate of corrosion, develop prognoses, and evaluate various courses of action. The corrosion conditions and rate were established by on-site and laboratory analyses. Historical records provided corrosion damage with time. Chloride penetration and corrosion damage were correlated with resistivity and other observations to give a relationship between the corrosive conditions and time to initial corrosion, first cracking, and critical damage. Prognoses were developed and evaluated by life cycle cost-benefit analyses for various courses of action, from “do nothing” to full-scale replacement of the piers for a service life in excess of 75 years. The techniques developed for this project could benefit maintenance monitoring and prognoses for other structures in similar corrosive environments. Contingency plans were prepared for pier replacement with precast modified V-piers to respect both the structural configuration and the historical significance of this bridge. A temporary support system was designed for rapid removal and replacement of each pier while the structure remains open to traffic on this sole route to the Florida Keys.