New bridge technique used for first time in Wisconsin
The side-by-side concrete bridges look virtually the same. One will handle northbound traffic, the other the southbound vehicles.
But it's what underneath the poured concrete — known as the bridge decks — that makes this highway project unique in Wisconsin.
The northbound bridge deck was built with a fiber-reinforced polymer material developed by Department of Civil and Environmental Engineering faculty members. The southbound bridge deck was built with traditional concrete and steel reinforcement.
It's the first time the Wisconsin Department of Transportation has used a polymer-based reinforcement system for a bridge deck.
"There are quite a few technological innovations," said Civil and Environmental Engineering Professor Larry Bank.
For more than a decade, Wisconsin's Department of Transportation has been upgrading state Highway 151 — one of the main traffic corridors between southern Wisconsin and the industrial Fox Valley. Including in the upgrade are several bridges that will replace intersections viewed by the DOT as dangerous.
The bridge utilizing the novel deck system was built at the intersection of state highways 151 and 26, near Waupun. The intersection is one of the busiest in the traffic corridor, because Highway 26 provides a direct shortcut between Highway 151 and Oshkosh and the northern Fox Valley.
Most bridges are built with concrete and steel reinforcement. But under the direction of Bank, researchers have developed a new bridge deck system that utilizes fiber-reinforced polymer (FRP). The FRP reinforcing grid was placed on the top of the concrete roadway, with an FRP stay-in-place panel positioned on the bottom of the roadway.
According to Bank, using fiber-reinforced polymer to reinforce a concrete bridge deck has several advantages over traditional steel reinforcement methods. Because of Wisconsin's harsh winter climate, and the use of salt on snow-covered roads, concrete that is reinforced with metal tends to crack and corrode over time. While the supporting piers and girders of a bridge may stay in good shape, the concrete-and-steel reinforcement usually has to be replaced at some point of the bridge's lifetime. Using FRP materials to reinforce bridges should cut down or eliminate the need to replace bridge deck supports, he said.
"It's not going to corrode and rust," he said. "It will lead to less maintenance and longer life of the structures. The idea is that this FRP system will prevent a lot of the cracking of the deck in the first place."
In addition, Bank hopes the use of FRP reinforcing materials will reduce the time and cost it takes to build a bridge. The FRP deck materials developed at UW-Madison can be brought to the work site pre-assembled, which will lessen the time it takes to construct a bridge. That will make drivers happier, as it should reduce the time that the bridge is closed to vehicle traffic. The FPR reinforcing materials are also lighter than traditional building materials, weighing about one-fifth of the steel reinforcement used on most bridges. That could reduce labor costs involved in building bridges, he said.
Adam Berg, a graduate student in civil and environmental engineering, has conducted several studies on the bridge project to assess the FRB bridge deck construction costs compared to a traditional bridge deck system.
DOT officials say they are anxious to see how construction of the Waupun bridge goes utilizing the FRP structures. If successful, the technology could be used on bridge projects throughout the state, according to Mark Klipstein, a project manager for the DOT's District 2 office in Waukesha.
"It gives us an alternative source of construction materials," he said. "It gives us an option for future bidding of bridges. Once this is done, and if it's proven effective, it creates more competitive bidding."
Although the cost of FRP materials is slightly more expensive than traditional steel reinforcing, Bank said the long-term cost savings of using well-designed FRP materials should make it a popular technology for future bridge projects. "That's really what we want to prove — that there's an advantage to using these FRP materials," he said.