A bascule bridge (also referred to as a drawbridge or a lifting bridge ) is a moveable bridge with a counterweight that continuously balances a span , or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed.
6-605: The Market Street Bridge , officially referred to as the John Ross Bridge , is a bascule bridge that spans the Tennessee River between downtown Chattanooga, Tennessee , and the Northshore District. It carries North Market Street (formerly designated as U.S. Route 127 ), and was named in honor of Cherokee Chief John Ross . The bridge was completed in 1917 at a cost of $ 1.1 million. In
12-571: A "Chicago" bascule) rotates around a large axle that raises the span(s). The Chicago bascule name derives from the location where it is widely used, and is a refinement by Joseph Strauss of the fixed-trunnion. The rolling lift trunnion (sometimes a "Scherzer" rolling lift), raises the span by rolling on a track resembling a rocking-chair base. The "Scherzer" rolling lift is a refinement patented in 1893 by American engineer William Donald Scherzer . The rarer Rall type combines rolling lift with longitudinal motion on trunnions when opening. It
18-465: The mid-1970s, the southern terminus of US 127 was moved several miles north to the intersection of Dayton Boulevard and Signal Mountain Boulevard in the nearby suburb of Red Bank . The bridge has concrete arch spans flanking a center draw span, which is a steel truss with double-leaf Scherzer rolling lift bascule mechanism. The double-leaf bascule lift span stands approximately 70 feet above
24-425: The possibility for unlimited vertical clearance for marine traffic. Bascule bridges have been in use since ancient times, but until the adoption of steam power in the 1850s, very long, heavy spans could not be moved quickly enough for practical application. There are three types of bascule bridge and the counterweights to the span may be located above or below the bridge deck. The fixed- trunnion (sometimes
30-547: The water. At the time of its completion in 1917, the 300-foot (91 m) main span was the longest rolling-lift bascule span in the world. Vehicular traffic originally included streetcars , but streetcar service across the bridge ended in the 1930s. The bridge was formally renamed the Chief John Ross Bridge in 1950. The bridge closed in 2005 for a renovation, but reopened on August 4, 2007, ahead of its originally scheduled September completion date. The bridge
36-662: Was listed on the National Register of Historic Places on December 20, 2010. Four times per year, the bridge is closed for a brief inspection to test its hinge mechanism, as mandated by the US Coast Guard . Bascule bridge The name comes from the French term for balance scale , which employs the same principle. Bascule bridges are the most common type of movable span because they open quickly and require relatively little energy to operate, while providing
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