Synthesis of Rating Methodologies for Concrete Bridges without Plans

Abstract

In response to Federal Highway Administration requirements, many states are confronted with assigning load ratings to large numbers of concrete bridges that do not have plans. The AASHTO Manual for Bridge Evaluation does not specify which methodologies should be used to establish load ratings for concrete bridges without plans, nor does it clearly state how extensive the evaluation of such structures should be. To inform engineers responsible for load rating structures without plans, this report highlights available non-destructive evaluation methods that are able, to varying extents, to locate and determine the size of concrete reinforcing bars. It also provides a survey of current and emergent methodologies for establishing load ratings for concrete bridges without plans. Finally, to characterize the state-of-the-practice, results are reported from a survey distributed to state bridge engineers. There are large differences among states in terms of the specificity of established procedures and overall methodologies employed to assign load ratings to the more than 25,000 bridges without plans located in the 24 states that responded to the survey. Recommendations for approaching this problem in a rational and cost-effective manner are made after considering both published evidence and ease of implementation across large inventories of structures.