Performance of Uncoated Weathering Steel Highway Bridges Throughout the United States

Because uncoated weathering steel (UWS) bridges have been in use in the United States for nearly 50 years, the long-term performance of these structures can now be assessed. An assessment was completed by surveying the varied experiences of 52 U.S. transportation agencies and analyzing the data on all UWS bridges known within these and other agencies, which totaled nearly 10,000 structures. It was established that the superstructure condition ratings system (based on a standard national rating system) of these structures was a valid means of assessing UWS performance in a quantitative manner on the basis of a comparison of these ratings to qualitative information received from bridge owners in the 52 agencies surveyed. Of the most significant findings from the analysis, first, was that the superstructure condition ratings of the majority of UWS bridges were classified as excellent or very good, on the basis of the national criteria for these qualitative descriptors. Second, a comparison of the ratings of UWS bridges and other steel bridges within representative agencies while accounting for differences in ages of the various populations indicated that UWS displays increased or similar performance relative to other steel. UWS bridges performed quite well in most cases. Considering their economic and environmental benefits, continued or increased use of UWS bridges is regarded as sound engineering practice.