Bridge-Condition Assessment and Load Rating Using Nondestructive Evaluation Methods

In most cases, bridge-condition assessment is made according to visual inspections, and bridge-load ratings are determined with fairly simple analytical methods and without site-specific, live-load, bridge-response data. As a result, estimates of bridge load-carrying capacity are often quite conservative. The increased weight of today’s trucks compared with design loads that are used for older bridges, combined with the continued aging and deterioration of our nation’s bridges, has resulted in a significant number of them being classified as structurally deficient. Reliable condition assessments are essential to ensure the safety of the traveling public. Furthermore, because load-carrying capacity is often used to prioritize bridges for repair, rehabilitation, and replacement, and because funds for these actions are limited, it is more important than ever that these estimates be as accurate as possible. To achieve this goal, researchers at the University of Delaware have been working with engineers at the Delaware Department of Transportation to develop methods for improving the accuracy of bridge-capacity evaluation through use of nondestructive evaluation techniques. Among the methods currently used are diagnostic load testing and in-service monitoring. These methods are described, and a detailed case study that illustrates the applied methodologies is discussed.