August/September 2017 August/September 2017 - Page 7

FRP WRAP GIVES OLD BRIDGE NEW LIFE By Kevin Wilcox May 9, 2017—East Lynn Lake, in scenic Wayne County, West Virginia, is a popular destination for outdoor enthusiasts, drawn by the reservoir's many species of stocked fish as well as boating and camping opportunities. The reservoir is part of a flood control project completed in 1970 and is operated by the U.S. Army Corps of Engineers district headquartered in Huntington, West Virginia. The only route to the lake crosses a 126 ft long concrete bridge founded on steel bents, and over the decades, those steel H-pile bents have corroded significantly. In 2013, roughly 44 years after the bridge was completed, the Corps reduced the span's capacity from 15 tons to 6 and limited traffic to a single lane. Replacing the bridge would have been complex and expensive. It would also have required discarding a reinforced-concrete deck that was still in good condition. Instead, a team of researchers from West Virginia University (WVU), working with the Corps in an initiative sponsored by the National Science Foundation called the Center for the Integration of Composites into Infrastructure, successfully rehabilitated the bridge and in the process validated a process for renewing the rusted steel bents with fiber-reinforced polymer (FRP) jackets. The FRP composite used in the project begins with a flexible sheet of glass fiber that is bonded with a polymer resin. The resulting material is exceptionally strong and airtight, two qualities needed for the East Lynn Lake bridge. The team was led by Hota GangaRao, Ph.D., P.E., F.SEI, F.ASCE, the Maurice A. and Joann Wadsworth Distinguished Professor of Civil and Environmental Engineering in WVU's Benjamin M. Statler College of Engineering and Mineral Resources. GangaRao directs the school's composites center and has been experimenting with FRP for decades, but this was the first time he had used it to rehabilitate rusted steel structural members. "The challenge was how [we were] going to use this kind of material without disturbing the basic configuration of the steel bridge structure," GangaRao recalls. "The steel wide-flange columns were badly corroded. How do I transfer the forces from the bridge deck to the columns [and] from the columns on down to the foundation? That was a challenge. Then how do I wrap this inconvenient cross section?" So he contacted material suppliers and selected a fiber jacket manufactured by Simpson Strong-Tie Company, Inc., of Pleasanton, California, that could encase a column as a continuous unit, as well as a fiber wrap from Air Logistics Corporation, of Monrovia, California, that could be installed around that jacket. Early exploratory work found that the steel bents were well preserved just 2 ft below the mud line. The team used a power washer to remove rust scales from the bents, treated them with a