One year after the collapse of Minneapolis’ I-35W bridge brought home the need for safer, more durable bridges and faster, less expensive bridge repair, a series of Wisconsin projects is marking significant progress toward those goals.
The bridge designs developed by University of Wisconsin-Madison researchers in cooperation with the Wisconsin Department of Transportation (DOT) include new techniques and materials that promise to cut construction times from weeks to days, and extend bridge lifespan by 20 to 30 percent, says UW-Madison civil engineering Professor Mike Oliva.
The team has built four such bridges in Wisconsin over the past three years, and will break ground on a fifth project later this month.
Wide deployment of these “accelerated” bridge designs could mean faster, more efficient repair of aging infrastructure at a much lower cost to taxpayers, says Oliva. The new designs should also improve worker safety and minimize traffic disruptions.
The bridge replacement project starting later this month is located in St. Croix County about 30 miles from the Twin Cities, where U.S. Highway 63 crosses over the Rush River. For the first time ever in Wisconsin, the bridge’s supporting structure, or abutment, will be assembled from pre-cast concrete parts, rather than from concrete that is cast in place. Not only is pre-cast concrete of higher quality, but the use of pre-cast components is also expected to cut support construction time from 3-4 weeks to days, says Oliva.
Past projects include:
– When road salt-laden water seeps into a bridge’s concrete deck, it begins to corrode the steel reinforcing bars inside, eventually reducing the bridge’s ability to take traffic load, says Oliva. To prevent this, Oliva working with fellow UW-Madison engineer Lawrence Bank and a research team has created designs that replace the steel rods with fiber-reinforced polymer – basically, an extremely strong, high-tech plastic that completely resists corrosion. The decks of two bridges on Highway 151 near Waupun and Fond du Lac now contain these plastic rods in place of steel.
– In a variation on this theme, the team designed a bridge deck that lacks reinforcing rods entirely. Instead, galvanized steel bars are placed between the bridge beams, allowing them to be easily inspected and keeping them away from damaging salt water on the deck. A bridge near Black River Falls now sports this type of construction.
– The deck of a bridge on I-90/39 near McFarland was rebuilt entirely of pre-cast components in 2006. This meant that construction workers were able to place the deck panels in just one day, whereas standard practices typically take 2-3 weeks.
