Development of a highway bridge load rating and assessment program

In the fall of 1999 a research project was initiated to develop a non-destructive testing system for highway bridges in the State of South Carolina. The State's aging bridge infrastructure consists of many load-restricted or posted bridges. The project included several phases. Discussed in this document are the findings of Phases 1 and 2. Phase 1 focused on the collection of background information regarding the condition of the existing bridge inventory, the available equipment for load testing, the most compatible computer modeling software, and the necessary support equipment for testing. Phase 2 combined the information gathered during Phase 1 and utilized that data to develop a load testing program. Various sensor technology, signal conditioning systems, and data collection software were compared and the preferred equipment was chosen. The mobile test facility (truck and enclosed trailer) were obtained and equipped. Several bridges were load tested using the new mobile testing facility. Data gathered for bridge responses to known test loads were then used to calibrate computer generated structural models. Various input parameters were considered during modeling. From information obtained during modeling and study of AASHTO recommended load rating procedures, methods were developed and discussed to incorporate field test data into the rating process. The known bridge response characteristics were found to increase the allowable load rating in some bridges.; This report concentrates on Phase 2 of this project, with primary emphasis on load rating considerations. Supporting documents have been written that discuss the field testing and modeling issues in more detail.