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a wooden bridge in Minnesota.

U researchers are working with the U.S. Department of Agriculture's Forest Service and county road departments to save wooden bridges from rotting.

Looking out for Minnesota's wooden bridges

By June Kallestad

From eNews, August 19, 2004

Minnesota's back roads are peppered with some 4,000 wooden bridges for vehicles and recreational use, such as snowmobiles. Sure, these bridges can take a beating, but like anything made of wood, water is their worst enemy. And when timber support beams start to rot, especially from within, it's often hard to tell how much damage they've sustained.

"There are literally thousands of timber bridges out there in need of a better inspection method," says Bob Ross, project leader for the U.S. Department of Agriculture's (USDA) Forest Service. "The current method is a visual assessment, but that often will miss what's going on inside the timber."

So the USDA Forest Service turned to the forest products experts at the University of Minnesota, Duluth's Natural Resources Research Institute (NRRI). These experts, who study everything from trees to veneer, scoured the globe for the latest in wood-rot detection technologies. They found seven types of equipment that could check wood for rot--without cutting into it. NRRI researcher Bob Vatalaro was responsible for comparing the technologies using old timbers collected from decaying bridges.

"Each piece of equipment has its own unique capabilities, which provides options for the inspection professionals to select which will do the best job for their situation," says Brian Brashaw, director of NRRI's wood products program. "The more we know about the bridge, the better we can take care of it, and the longer it will last."

Working with the Northland Advanced Transportation Systems Research Laboratory-comprising experts from the U and the Minnesota Department of Transportation (MnDOT)-Brashaw organized what they learned about the seven technologies into training courses for MnDOT field inspectors and Minnesota county highway department inspectors. So far, NRRI has trained more than 250 inspectors and engineers in the new technologies.

The researchers hope to eventually build testing equipment right into the bridges. NRRI engineers will help the USDA Forest Service build several pilot bridges with the built-in detection technologies at Michigan Technological University (MT). Brashaw is also collaborating with researchers at MT and the Forest Products Laboratory in Madison, Wisconsin, to use the equipment in other products or areas where wood rot could pose a problem, such as boats, historic buildings, and even trees.

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