Survey and Evaluation of Damaged Concrete Bridges

Abstract

It is well known that the U.S. bridge inventory stands in need of repair. For a rational allocation of U.S. investment resources to bridge maintenance, life cycle cost and probabilistic methods must be used. This requires a quantitative estimate of the remaining strength over the intended lifespan for a given bridge. Although nondestructive evaluation methods are becoming established for bridge inspection purposes, specific recommendations for the application of these methods for individual bridges do not exist. This study focuses on reported damage and damage modeling for concrete bridges, with particular attention to Colorado bridges. A survey on degradation mechanisms is briefly presented. Bridge damage is reviewed for a variety of concrete bridges based on information in the literature and from field studies performed by the Colorado Department of Transportation. A catalog of damages and examples that illustrate the variety and severity of damage in these bridges are presented. For the bridges considered in the survey, the most common source of damage is water leaking through deck joints. A method for predicting strength loss is applied to a typical bridge in Colorado. It is shown that corrosion initiation occurs more quickly and normalized strength loss is much greater for shear than for flexure. It is also shown that many reinforced concrete bridges under corrosion attack may be more vulnerable to shear than to bending failure. The results can be used to identify critical elements for inspection and repair, and to assist in the development of rational maintenance planning strategies for concrete bridges.