PERFORMANCE OF WEATHERING STEEL IN HIGHWAY BRIDGES
A Third Phase Report

I. INTRODUCTION

Weathering steel has been a primary construction material for bridges in the United States since 1964. However, its widespread application has not been without controversy. As such, the American Iron and Steel Institute (AISI) initiated a long-term project to study the performance of weathering steel in different structures and environments. Phase-I was initiated in 1980, and consisted of field inspections of 52 highway bridges. The results of this inspection have been documented in an AISI report, Performance of Weathering Steel Bridges-A First Phase Report, August 1982.

The second phase of the long-term project focused on maintenance coatings which could be applied to salt-contaminated weathering steel. Phase-II was conducted by the Steel Structures Painting Council (SSPC) working under contract for the Federal Highway Administration (FHWA). Based on this study, the FHWA issued a report RD-92-055 entitled, "Maintenance Coatings of Weathering Steel: Field Evaluation and Guidelines," March 1995.

In 1988, the FHWA convened a forum where more than 130 federal and state government and industry representatives met to discuss their experiences with the performance of weathering steel in bridges. The proceedings of this forum are included in the FHWA Report TS-89-016, "Forum on Weathering Steel for Highway Structures: Summary Report," June, 1989. The information presented at the forum was used by the FHWA to develop and issue a Technical Advisory (TA) entitled, Uncoated Weathering Steel in Structures, T5140.22, October, 1989 which provides specific guidance and recommendations about the use of weathering steel in highway structures.

In 1993, AISI began Phase-III of this project. This included revisiting the 52 bridges that were initially inspected in 1980 as part of Phase-I, and following 13 more years of exposure.

In addition to the original bridges, eleven others were added for inspection: five in Iowa; one in California; and five in Puerto Rico with tow parallel bridges at each site. Exhibit A includes the results of both Phase-I and Phase-III inspections. Fifty-six of the 63 bridges carry highway traffic; three are railroad bridges; one is a combination pedestrian and equestrian bridge and two are part of the West Virginia University Personal Rapid Transit System. Bridge #14 and #21 listed in Exhibit A are located in Michigan and have already been painted. One of the Iowa bridges, Route 28 over the Raccoon River, has also been painted.

What follows are a few historical notes on the use of weathering steel in bridges and a summary of the major findings of the Phase-III inspections.

Next: History

Back to Table of Contents