Timber bridge
| Truss bridge | |
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| Characteristics | |
| Material | wood, with a steel center truss |
| Beam bridge | |
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The Beam bridge
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| Characteristics | |
| Material | wood |
Trestles are useful as approaches to bridges over marshes and shallows
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| Material | Timber, iron, steel, reinforced concrete, prestressed concrete |
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A timber bridge or wooden bridge is a bridge that uses timber or wood as its principal structural material. One of the first forms of bridge, those of timber have been used since ancient times.
Most ancient form of timber bridges are log bridges, which are employed by felling a tree over a gap needed to be crossed.
Among the oldest timber bridges is the Holzbrücke Rapperswil-Hurden crossing upper Lake Zürich in Switzerland; the prehistoric timber piles discovered to the west of the Seedamm date back to 1523 B.C. The first wooden footbridge led across Lake Zürich, followed by several reconstructions at least until the late 2nd century AD. when the Roman Empire built a 6 metres (20 ft) wide wooden bridge. Between 1358 and 1360, Rudolf IV, Duke of Austria, built a 'new' wooden bridge across the lake that has been used to 1878 – measuring approximately 1,450 metres (4,760 ft) in length and 4 metres (13 ft) wide. On April 6, 2001, the reconstructed wooden footbridge was opened, being the longest wooden bridge in Switzerland. The Kapellbrücke is a 204 metres (669 ft) long bridge crossing the Reuss in the city of Lucerne in Switzerland. It is the oldest wooden covered bridge in Europe, and one of Switzerland's main tourist attractions.
Recently timber bridges have received attention in the United States because they are environmentally friendly compared to other bridge types. Until 1991, the Federal Highway Administration has concentrated on major highways and other primary roads; rural highways and local roads, where timber bridges are mostly found, have received less attention.
Local and state agencies prefer timber bridges because timber is a renewable resource, it is relatively economical, and there have been rapid improvements in design, construction, and preservative treatment. The US Congress emphasized timber bridges by passing the Timber Bridge Initiative (TBI) in 1988 and the Intermodal Surface Transportation and Efficiency Act (ISTEA) in 1991.
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Wikipedia