M-28 / E. Br. Tahquamenon River
City/Township: Chippewa Twp.
Location: M-28 / E. Br. Tahquamenon River
Year Built: 1926
About this Bridge:
Located on M-28, about a mile southeast of the village of Strongs, this single-span concrete/steel bridge crosses the East Branch of the Tahquamenon River. The structure is configured as a 55-foot, steel deck girder bridge, with nine lines of built-up I-beams encased in concrete.
The structural type that MSHD delineated for this bridge was one that the agency had only recently begun using. The highway department had developed a standard design for a steel stringer bridge as early as the 1905-1906 biennium and for a steel plate girder two years later.
Additionally, MSHD had begun encasing the stringers partially in concrete as part of the deck in the 1905-1906 biennium. But it was not until about 1926 that MSHD engineers began encasing the webs of steel girders in concrete. The purpose for this in unclear: the concrete does not appear to add structural strength to the beams, and concrete diaphragms are still employed to brace them laterally. MSHD illustrated the new configuration in its Twelfth Biennial Report with a photo of a bridge over the Maple River on US-27 (since demolished), describing it as “one of the latest types of encased girder design.” MSHD soon discontinued wrapping the interior girders in concrete, limiting the concrete to the exterior spandrel walls. The Tahquamenon River Bridge is one of only two such encased girders identified by survey sample. It is thus noteworthy as a formative exercise in what would evolve into a state standard design. Carrying a regionally important route over a major watercourse, it is both historically and technologically significant - an important transportation-related resource.