bridge, structure: Truss, Arch, and Cantilever Bridges

The truss can span even greater distances and carry heavy loads; it is therefore commonly used for railroad bridges. A large truss span like that over the Columbia River at Astoria, Oreg., can extend to 1,232 ft (376 m); the Ikitsuki Bridge, connecting Ikitsuki and Hirado islands in SW Japan, has a continuous-truss span of 1,312 ft (400 m), the longest in the world. If the truss is shaped into an arch, even longer bridges are possible; the Chaotianmen Bridge in Chongqing, China, the Lupu Bridge, Shanghai, China, the New River Bridge in West Virginia, the Bayonne Bridge between New York and New Jersey, and the Sydney Harbor Bridge in Australia have the longest steel arch spans, at 1,811 ft (552 m), 1,804 ft (550 m), 1,700 ft (518 m), 1,675 ft (510 m), and 1,670 ft (509 m), respectively. Concrete arch bridges tend to be somewhat smaller, the largest being the Wanxian Bridge in China and the Krk Bridge in Croatia at 1,378 ft (420 m) and 1,280 ft (390 m), respectively. The longest concrete arch bridge in the United States is the Natchez Trace Parkway Bridge in Franklin, Tenn., at 582 ft (177 m), although the concrete and steel O'Callaghan-Tillman Memorial Bridge, Nev.-Ariz., near Hoover Dam, has the largest concrete arch, at 1,079 ft (329 m). The cantilever, however, is more common for spans of such lengths. The cantilevered Forth Bridge (1890) in Scotland was the first major structure built entirely of steel, the material that made possible its two record-setting spans of 1,710 ft (521 m) each. They remained the longest in existence until 1917, when the St. Lawrence River at Quebec Bridge was built; it has an 1,800-ft (549-m) span. The longest cantilever bridge in the United States is the Commodore John Barry Bridge in Chester, Penn., which has an 1,644 ft (501 m) span.

Sections in this article:

• Introduction
• Military Bridges
• Movable Bridges
• Cable-Stayed, Suspension, and Combination Bridges
• Truss, Arch, and Cantilever Bridges
• Modern Bridge Designs
• Early Bridges
• Bibliography

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