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A continuous truss bridge
is a truss bridge
A truss bridge is a bridge composed of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges...
which extends without hinges or joints across three or more supports. A continuous truss bridge may use less material than a series of simple trusses because a continuous truss distributes live loads across all the spans; in a series of simple trusses, each truss must be capable of supporting the entire load.
Although some continuous truss bridges resemble cantilever bridges and may be constructed using cantilever techniques, there are important differences between the two forms. Cantilever bridges need not connect rigidly mid-span, as the cantilever arms are self-supporting. Although some cantilever bridges appear continuous due to decorative trusswork at the joints, these bridges will remain standing if the connections between the cantilevers are broken, or if the suspended span (if any) is removed. Conversely, continuous truss bridges rely on rigid truss connections throughout the structure for stability. Severing a continuous truss mid-span endangers the structure. However, continuous truss bridges do not experience the tipping forces that a cantilever bridge must resist, because the main span of a continuous truss bridge is supported at both ends.
It is possible to convert a series of simple truss spans into a continuous truss. For example, the northern approach to the Golden Gate Bridge
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...
was originally constructed as a series of five simple truss spans. In 2001, a seismic retrofit
Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers,...
project connected the five spans into a single continuous truss bridge.
Some notable continuous truss bridges, with main span lengths http://www.aisc.org/Content/ContentGroups/Documents/NSBA5/20_NSBA_LongestSpans.PDF
- Ikitsuki Bridge, 1312 ft
- Astoria-Megler Bridge
The Astoria–Megler Bridge is a steel girder continuous truss bridge that spans the Columbia River between Astoria, Oregon and Point Ellice near Megler, Washington, in the United States. The span is from the mouth of the river, and was the last segment of U.S. Route 101 between Olympia, Washington...
, 1232 ft
- Francis Scott Key Bridge
The Francis Scott Key Bridge, also known as the Outer Harbor Bridge or simply the Key Bridge, is a continuous truss bridge spanning the Patapsco River in Baltimore, Maryland, USA. The main span of is the third longest span of any continuous truss in the world.The bridge was opened in March 1977...
, 1,200 ft
- Taylor-Southgate Bridge
The Taylor–Southgate Bridge is a continuous truss bridge that was built in 1995. It has a main span of 850 feet , and a total span of 1850 feet . The bridge carries U.S...
, 850 ft
- Julien Dubuque Bridge
The Julien Dubuque Bridge traverses the Mississippi River. It joins the cities of Dubuque, Iowa, and East Dubuque, Illinois. The bridge is part of the U.S. Highway 20 route...
, 845 ft
- Charles M. Braga Jr. Memorial Bridge, 840 ft
- Governor Harry W. Nice Memorial Bridge
The Governor Harry W. Nice Memorial Bridge is a , two-lane continuous truss bridge that spans the Potomac River between Newburg in Charles County, Maryland and Dahlgren in King George County, Virginia, USA....
, 800 ft
- Sciotoville Bridge
The Sciotoville Bridge is a steel continuous truss bridge carrying tracks of the CSX railroad across the Ohio River between Siloam - a junction located north of Limeville, Kentucky and east of South Shore, Kentucky - and Sciotoville, Ohio in the United States...
, 775 ft
- Glover Cary Bridge
The Glover H. Cary Bridge is a continuous truss bridge that spans the Ohio River between Owensboro, Kentucky and Spencer County, Indiana. It was named for the late U.S. Congressman Glover H. Cary , and opened to traffic in September 1940...
, 750 ft
- Carroll C. Cropper Bridge, 750 ft
- Sewickley Bridge
The Sewickley Bridge is a steel continuous truss bridge spanning the Ohio River at Sewickley, Pennsylvania and Moon Township, Pennsylvania carrying State Route 4025 and the Orange Belt. It was built by American Bridge Company and opened October 21, 1981. Its center span is long and the side spans...
, 750 ft
- Betsy Ross Bridge
The Betsy Ross Bridge is a continuous truss bridge spanning the Delaware River from Philadelphia to Pennsauken, New Jersey. It was originally planned as the Delair Bridge, after a paralleling vertical lift bridge owned by Pennsylvania Railroad , but was instead named for Betsy Ross, reputed creator...
, 729 ft
- Champlain Bridge
The Champlain Bridge was a long vehicular bridge in the United States that traversed Lake Champlain between Crown Point, New York and Chimney Point, Vermont. It was opened to traffic in 1929 as a toll bridge; the tolls were removed in 1987...
, 450 ft