32 - A Man, A Bridge, And A Vision: The Mackinac Bridge

The Mackinac Bridge is the State of Michigan’s single largest asset and one of the world’s leading suspension bridges. Opened in 1957, the 26,372-foot-long bridge is the longest suspension bridge between anchorages in the Western Hemisphere. The bridge provides safe, pleasurable, and expedient passage for Interstate 75 (I-75) over the Straits of Mackinac for economic benefit and improved quality of life. The design of the Mackinac Bridge was directly influenced by the lessons from the first Tacoma Narrows Bridge, which failed in 1940 because of its instability in high winds. To counter the potential aerodynamic issues the bridge’s lead designer David B. Steinman, as he wrote in Scientific American faced, “the creation of a new science, combining the essentials of three different fields of specialized knowledge: the deflection theory of suspension bridges, the science of aerodynamics, and the mathematical theory of vibration analysis.” His solution recommended that future bridge designs include deep stiffening trusses to support the bridge deck and an open-grid roadway to reduce its wind resistance. Both features were incorporated into the design of the Mackinac Bridge. The result of Mr. Steinman’s vision as he wrote in his poem the Bridge at Mackinac is a colossal bridge and, There it spans the miles of water/ Speeding millions on their way/ Bridge of vision, hope and courage/ Portal to a brighter day.