Iowa Demonstration Project: Accelerated Bridge Construction on US 6 over Keg Creek

As part of a national initiative sponsored by the Federal Highway Administration (FHWA) under the Highways for LIFE program, the Iowa Department of Transportation (DOT) was awarded a $400,000 grant to demonstrate the use of proven, innovative accelerated bridge construction (ABC) technologies to deliver this $2.7 million project in less time than conventional construction. This project represents a cooperative effort among the FHWA, Iowa DOT, and the Strategic Highway Research Program (SHRP 2) project R04 research team to demonstrate the latest advances in ABC methods. This report details the ABC innovations used to replace the US 6 bridge over Keg Creek featuring prefabricated superstructure and substructure systems, high- and ultra-high-performance concrete, self-consolidating concrete, and fully contained flooded backfill. The new bridge was completely prefabricated off-site and installed into place—a first in Iowa and in the United States. The ABC approach and innovations in this project increased safety, enhanced quality, and allowed the contractor to replace the bridge during a 16-day road closure instead of 6 months, as would have been required under traditional construction methods. Using prefabricated bridge systems and innovative materials nearly doubled the initial bridge construction cost compared to traditional construction. However, a comprehensive economic analysis including user cost savings shows that the project saved road users about $0.44 million (or about 29 percent less than conventional construction). The experience gained on this successful project will help the Iowa DOT implement these innovations more routinely on future projects.