Prioritizing Bridge Structures for Underwater Inspections: Summary Report

About the report:

In the last decade, there has been increasing national concern about the adequacy of underwater inspection of bridge substructures. A number of factors have contributed to this concern, in particular the collapse of several major spans, some of which led to loss of life. Substructure failures have been the cause of bridge collapses and the subject of at least five National Transportation Safety Board (NTSB) highway bridge investigations. In at least four instances, deficiencies in the substructure could have been identified by underwater inspection. During this project, 425 bridges in Virginia were identified as requiring underwater inspection. It was concluded that assessments of the type and extent of damage to structures below the waterline prior to inspection are highly inaccurate. Prioritizing bridges for inspections must be based on an established history of underwater inspections. Trends in the deterioration of underwater structures indicate several factors to be considered in developing a priority system for an underwater inspection program. These trends are described, and time intervals for the inspection of bridges with a previous inspection history are suggested.

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