Built in 1949, the Spokane River Bridge (formerly the De Tillian Bridge) at Long Lake Dam is an outstanding example of a graceful concrete arch bridge, one of the few built during the 1940s. This structure is located in a remote part of eastern Washington, where rugged basalt cliffs present a pleasing contrast to the elegant lines of the bridge. Its use in this location enhances the natural beauty of the rugged environment in a particularly effective blend of a man-made structure with its natural surroundings. The structure is also an example of innovative engineering technology—it features the considere hinge in the arch design of the bridge. Under this system, the arch acts as a two-hinged arch to support the dead load of the structure. After all concrete in the superstructure is cast, the falsework is released and the arch ribs then support the total dead load of the structure. The arch rib steel is then welded together and the concreting of the hinge is completed, thus causing the arch to act as a fixed arch under live load conditions. The Spokane River Bridge at Long Lake Dam is the only concrete arch bridge built by Washington State in the 1940s using this system; it cost $215,400 to construct. Clarence B. Shain was the Director of Highways at the time the Spokane River Bridge was built, George Stevens was the Bridge Engineer, and Henry Hagman of Cashmere, Washington, builder of numerous bridges in the Pacific Northwest, was the contractor.
Spokane River Bridge
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