Pack Rust Mitigation Strategies for Flange Splice Connections in Steel Bridges

Abstract

One of the main causes of infrastructure deterioration is corrosion. Different types of corrosion such as surface and pitting corrosion have been researched and addressed by industry. However, pack rust is another type of corrosion that requires attention because of its complexity and lack of research. Pack rust occurs between overlapping plates, which makes it difficult to remove and treat. A previous survey in the State of Indiana highlighted that a significant number of steel bridges exhibit some level of pack rust in the bottom flange of splice connections. Consequently, this study focuses on evaluating mitigation strategies that can delay further development of pack rust at the interface between the connected elements in a typical tension splice. Additionally, this study also examines the effects of pack rust on the tensile strength of a flange splice connection. The ultimate goal is to develop a series of guidelines that can be implemented in the field to address pack rust. To accomplish this, specimens were created to model the bottom splice connection. These specimens were exposed to a corrosive environment for different periods, and later tested under tension to evaluate any strength reduction. The level of pack rust developed in this study, which correlates to an exposure in the field of 20 to 40 years, increased the slip resistance of the specimens tested and did not decrease the ultimate strength. Finally, out of the three mitigation products tested, two had satisfactory results that merit further research and field testing.