The use of weathering steel in highway bridges has historically been a source of controversy, despite the potential for significant increases in cost-effectiveness. The first weathering steel bridges in America were constructed in the mid-1960s, with a significant percentage of the early weathering steel bridges constructed in Michigan. Numerous problems with weathering steel bridges in that state, along with problems reported in other states, led many states to question the performance of these structures. In the past two decades, research has attributed the majority of these past problems to: the use of weathering steel bridges in inappropriate environments, excessive salt contamination from deicing salts or marine environments, or problems with design details (such as leaky joints). Therefore, when these problems are controlled or eliminated, weathering steel bridges are an attractive alternative that can provide substantial cost savings to bridge owners. While the initial material cost of weathering steel is more expensive than that of traditional (non-weathering) steels, considering the cost of painting causes weathering steel to be a cost-effective alternative. In addition to the cost savings offered, implementation of weathering steel provides environmental benefits such as preventing the release of volatile organic compounds into the atmosphere during maintenance painting as well as eliminating concerns with containment and disposal of removed paint. This paper will provide an overview of a comprehensive assessment of the performance of the weathering steel bridge inventory in West Virginia. It will present findings from an evaluation that was used to categorize locations and site conditions that may lead to less than favourable performance of weathering steel bridges, if applicable. It will also present recommendations regarding detailing procedures to be incorporated with weathering steel bridges.
A588 weathering steel is formed by alloying additional elements (2% or less of various combinations of copper, phosphorus, chromium, silicon, and/or nickel) with traditional steels (A36 or A572), which cause the corrosion resistance of the steel to be significantly increased. The behaviour of weathering steel exposed to appropriate environments is fundamentally different from that of traditional steel in that in contrast to the formation of iron oxide (rust) that occurs when traditional steels are exposed to atmospheric conditions, weathering steel forms a protective oxide coating that reduces the rate of corrosion of the steel. However, this protective oxide coating will form only if the weathering steel is not subjected to extended period of moisture. Additionally, proper detailing of the structure is critical to maintain the integrity of the protective coating.