Thursday, October 27, 2011

Michigan's Bridges: 20 Mile Road Bridge at the Historic Bridge Park

August 2011 (42.290 Degrees, -85.114 Degrees) 20 Mile Road Bridge
The next bridge is a little five panel Pratt truss. On Habs Haers Website there are some nice photos of the bridge when it spanned the St. Joseph River on Twenty Mile Road in Tekonsha, Calhoun County. Now it carries Bridge Park Trail over Dickinson Creek. I wonder what is a bridge's significance once it's removed from its home? This bridge was full of purpose but it seems less important sitting renovated and then abandoned in this park.
According to the Historic Bridges Website, it's a 64 ft long by 15.4 ft wide riveted pony truss that was built in 1906. Pratt trusses typically have pinned connections, but as can be seen above, all the members are riveted to plates. The website said it was unusual to see a riveted highway bridge, but at the beginning of the 20th century I think most bridges were riveted. I worked on the East Bay Bridge after the 1989 Loma Prieta earthquake and watched workers replacing thousands of rivets with high strength bolts.
I like the laced guard rails attached to the sides of the truss. I also like how the diagonal members meet in the center panel to form an 'X.'

Creative Commons License
Michigan's Bridges: 20 Mile Road Bridge at the Historic Bridge Park by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

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