The St. Joseph County Road Commission has begun the process of post-tensioning a timber bridge. The work on the Heimbach Road Bridge, which started Monday, is a pioneering technique for the state of Michigan.
The bridge between Hutchinson and North Fisher Lake roads will be closed for about two weeks; the detour is North Fisher Lake Road to Moorepark Road to Hutchinson Road. The Road Commission has been having a tough time with the Heimbach Road bridge, as heavy traffic has been beating it up badly, and “we are trying to preserve its life as long as we can,” Road Commission managing director Chris Minger said.
The technique was presented at a bridge meeting in Lansing last winter, Minger said. It has been used in Canada, but never before in Michigan, so the Michigan Department of Transportation is watching the Road Commission’s process with interest. It involves brackets being fit on the outside, full-length rods attached on the top and underneath, then squeezing the bridge together to apply post-tension so the whole deck acts as a single unit.
The process is regularly used on concrete bridges.
Of St. Joseph County’s 97 bridges, more than 50 are timber, more than 40 are concrete and the rest are a conglomeration of the two.