The Belle Isle Bridge | Detroit, MI
March 26, 2011
Wikipedia notes that the official name of the bridge across the Detroit River to Belle Isle from Detroit is the MacArthur Bridge. The bridge uses nineteen arches to span the 2,193 feet to Belle Isle. Completed in 1923 for $2,635,000, it replaced a mostly wooden bridge that was destroyed by fire in 1915. See The day the bridge to Belle Isle burned down for more on that. While it was once known as the Belle Isle Bridge, was renamed in honor of General Douglas MacArthur in 1942.
Belle Isle Bridge “Douglas MacArthur Bridge” at HistoricBridges.org explains:
This is an extremely long multi-span concrete arch bridge that gives people access to Belle Isle, and the structure is the longest arch bridge in the state of Michigan.
This bridge is extremely significant not only because of its length, but because it is a very early example of a cantilevered concrete arch. A cantilevered concrete arch does not function like a traditional arch. Traditional arch bridges require the arch to be a complete and connected arch to function. This arch bridge does not function in that way. Each half of each arch spans is a cantilever arm that is structurally independent from the other half of the arch in that span. Standing under a span of this bridge, a clear gap at the center of the span is visible. Indeed, on the outermost part of the arch, a decorative “keystone” was placed for aesthetic reasons to cover up this gap.
Wayne County Road Commission was among Michigan’s counties, an innovative and creative road commission and they apparently made significant use of concrete cantilever arch structures. Other examples of concrete cantilever bridges in the county remain. These other examples are different from the Belle Isle Bridge, and feature a third central “suspended” span between the cantilever arms.