Determination of the end of functional service life for concrete bridge components
The transportation engineering community of the United States faces a tremendous problem: the gradual deterioration of the nation's bridges. A major component of the overall bridge deterioration problem is the corrosion-induced deterioration of reinforced concrete bridge components that are exposed to de-icing salts. The progression of events resulting from corrosion of the reinforcing steel includes cracking, delamination, spalling, and patching of the surface concrete.
Bridge components reach the end of their functional service life when the level of damage warrants rehabilitation. The objective of this study was to determine the end of functional service life for concrete bridge decks, piers, and abutments by quantifying terminal levels of physical damage. The approach for quantifying terminal damage levels involved obtaining recommendations from state Department of Transportation (DOT) bridge engineers via an opinion survey.
A field study of 18 existing concrete bridges that had been designated for rehabilitation was conducted to develop concrete bridge component maps showing areas of physical damage. Deck damage maps were produced using a ground-based photogrammetry system developed in this study, while pier and abutment damage maps were drawn by hand in the field. Survey Kits based on the component damage maps were distributed to bridge engineers in 25 states that use de-icing salts. The engineers evaluated the maps and recommended when each component should be, or should have been, rehabilitated~ Based on the engineers' responses, linear regression prediction models were developed to relate the recommended bridge component rehabilitation time point to the physical damage level. Based on the prediction models, two viable terminal damage levels for concrete bridge decks, and a partial terminal damage level for concrete bridge piers, were quantified.