The Benson Street Bridge, spanning Mill Creek between Reading and Lockland, Ohio, holds a unique place in the state’s engineering history. Completed in 1910, it was the first concrete “pony arch” bridge of its type in Ohio, and among the earliest examples in the nation.
Designed by E. A. Gast, deputy county surveyor, under County Surveyor Clinton Cowen, and assisted by Hugo Eichler, the Benson Street Bridge was constructed by contractor Peter Praechter for $7,127. Its graceful concrete arches soon earned it the nickname “rainbow arch.”
It replaced a Howe truss that had long struggled against the Mill Creek’s frequent flooding. Because the new structure could not restrict the creek’s channel, a filled concrete arch was dismissed, and reinforced concrete emerged as the most practical solution, cheaper than steel yet durable and modern for its time. Gast’s design predated James Barney Marsh’s 1911 patent for a similar arch form. Unlike Marsh’s later designs, which incorporated expansion plates to accommodate thermal movement, Gast’s bridge used hingeless arches that relied on heavy transverse beams and rigid abutments to manage stress.
Though an identical span built in 1911 across the West Fork of Mill Creek was demolished in 1983, the Benson Street Bridge endured. It was rehabilitated in 1992 under the direction of the Hamilton County Engineer’s Office, preserving one of the earliest surviving examples of a rainbow arch bridge in the United States.
I guess I always just lumped this in with the Marsh bridges. Nice to learn the difference.