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|Jazyk:||Počet slov:||5 119|
|Referát vhodný pre:||Stredná odborná škola||Počet A4:||17.5|
|Priemerná známka:||2.95||Rýchle čítanie:||29m 10s|
|Pomalé čítanie:||43m 45s|
The cantilevered arms support the suspended span, and the downward force of the span is absorbed by the towers.
Cantilever bridges are self-supporting during construction. They are often used in situations in which the use of scaffolding or other temporary supports would be difficult. The Forth Bridge, a railway bridge across the Firth of Forth in Queensferry, Scotland, has two main spans of 521 m (1,710 ft) each. The Hâora (Howrah) Bridge in Calcutta, India, was opened in 1943, with a main span of 457 m (1,500 ft). The Québec Bridge across the Saint Lawrence River in Canada has a span of 549 m (1,800 ft).
C Arch Bridges
Arch bridges are characterized by their stability. In an arch, the force of the load is carried outward from the top to the ends of the arch, where abutments keep the arch ends from spreading apart. Arch bridges have been constructed of stone, brick, timber, cast iron, steel, and reinforced concrete.
Steel and concrete arches are particularly well suited for bridging ravines or chasms with steep, solid walls. The New River Gorge Bridge in West Virginia is the longest arch bridge, spanning a gap of 518 m (1,700 ft). Other long arch bridges include the Bayonne Bridge between New York and New Jersey, and the Sydney Harbor Bridge in Australia, with main spans of 504 m (1,652 ft) and 503 m (1,650 ft), respectively.
D Truss Bridges
Truss bridges utilize strong, rigid frameworks that support these bridges over a span. Trusses are created by fastening beams together in a triangular configuration. The truss framework distributes the load of the bridge so that each beam shares a portion of the load. Beam, cantilever, and arch bridges may be constructed of trusses. Truss bridges can carry heavy loads and are relatively lightweight. They are also inexpensive to build. The Astoria Bridge over the Columbia River in Oregon has a span of 376 m (1,232 ft).
E Suspension Bridges
Suspension bridges consist of two large, or main, cables that are hung (suspended) from towers. The main cables of a suspension bridge drape over two towers, with the cable ends buried in enormous concrete blocks known as anchorages. The roadway is suspended from smaller vertical cables that hang down from the main cables. In some cases, diagonal cables run from the towers to the roadway and add rigidity to the structure. The main cables support the weight of the bridge and transfer the load to the anchorages and the towers. Suspension bridges are used for the longest spans.
Zdroje: Microsoft Encarta 2003