M-26: Eagle River Timber Bridge Eagle River MI
"The Eagle River Timber Bridge
Reprinted from the June 1991 issue of "Mates" (Issue No. 54), produced by the Michigan Department of Transportation.
A recent point of pride in the town of Eagle River, on Michigan's beautiful Keweenaw Peninsula, is a glue-laminated timber bridge which carries M 26 over the Eagle River. Aesthetically, the new bridge blends in well with the scenic Copper Country, and structurally it was designed to carry the same traffic loads as our State trunkline concrete and steel bridges.
The total length of the wooden bridge is just over 152 ft, and it stands 50 ft above the Eagle River. Supported by two, side-by-side arches spanning 74 and 79 ft, the bridge is primarily made of timber, with the connecting components fabricated of steel. An asphalt wearing course carries traffic across the wooden deck. All wood components were pressure treated with a preservative (pentacholorphenol in oil) an include the pedestrian railing and posts and deck support columns, wheel guards, beams and stringers, deck and the arches themselves. Enough lumber was used in the bridge to build three or four average sized houses.
Each of the two arches supporting the structure is actually made of two arched segments, joined at the top with a crown hinge, and measure 60 in. deep and 14 in. wide. The largest of the four segments is 42 ft from end-to-end, with a crown height of 25 ft, and weighs about 10,600 lb. The other three segments are 37 ft long, 18 ft to the crown, and weigh about 8,700 lb each. The base hinges that attach the arches to the concrete abutments and the two crown hinges, pivot on 4-in. diameter steel pins which are chrome plated to provide corrosion protection and lower friction resistance to any rotational movement of the arches.
All the steel in the structure (except the hinge pins) was hot-dipped galvanized, then covered with a tie-coat, an intermediate epoxy coating, and a brown urethane top coat. This coating system is designed to protect the steel for 30 years. Any timber members that were cut or drilled during construction were treated with two coats of copper naphthenate to protect the cut areas. The entire structure's wooden members will be recoated with preservative every three years, and at that time all bolts will be checked and retightened if necessary.
The timber bridge at Eagle River provides motorists with an aesthetically pleasing, functional structure. To one side is the vast expanse of Lake Superior and on the other side are splendid trees with a cascading waterfall. The bridge's appearance blends into the surrounding environment and was an idea choice for such a scenic location.
— Brian Ness" (
visit link)