Residential Drive

MDOT Historic Bridge Eaton County Residential Drive

County: Eaton

City/Township: Walton Twp./private

Location: Residential Drive

Year Built: 1875

About this Bridge:
This bowstring truss bridge is eligible for the National Register as an excellent example of the bowstring pony truss, a once common bridge type that is now extremely rare.

There is no information about the history of the Residential Drive Bridge in county or local records. According to its owner, Zygmunt Brzycki, the bridge was moved to this site from Bennett Park in Charlotte in 1968. A photograph in a booklet prepared for Charlotte's centennial in 1963 appears to show the bridge in the park. The bridge was probably originally erected in another location in the late nineteenth century, then salvaged by the city for park use when it became inadequate to handle farm machinery and car traffic in the twentieth century.

Inveterate bridge designer Squire Whipple obtained a patent for a bowstring truss in 1841. Other bowstring designs soon joined the many truss forms developed in the nineteenth century. As bridge engineer and historian J. A. L. Waddell observed: "For many years, American bridge-designers exercised their ingenuity in devising new forms of trusses and girders, the principal object of their endeavors being to find forms involving the use of the smallest amount of metal." The bowstring's curved top chord, which was in compression, required less material than the more common truss form with a horizontal top chord and inclined end posts. The lower chord, which tied together the bow's two ends, was also relatively light, as were the vertical members that dropped from the top chord to support the deck.

While adequate for traffic in the horse-and-buggy era, the bowstring truss could not handle the heavier and faster traffic that developed in the late nineteenth and early twentieth centuries. "Each form as it appeared," Waddell noted, "was tested by subjecting it to the ordeal of actual use, which showed conclusively both its merits and its defects; hence by a process of elimination, based upon the principle of the survival of the fittest, a few forms have been retained and the others have been relegated to the history of bridge-building." The latter was the fate of the bowstring truss. Stronger and more efficient truss forms prevailed, particularly after structural steel became widely available in the 1890s.

By the end of the 1930s, truss bridges of almost any design had fallen out of favor as steel stringer and other bridge types became easier and cheaper to produce. In the last half of the twentieth century, the population of truss bridges in Michigan has declined rapidly. The loss of bowstrings is even more dramatic: by the early 1990s, only one bowstring truss, the Elm Circle Drive Bridge over the Lower Rouge River in Wayne County, still carried highway traffic.