Trestle bridge: Difference between revisions

Revision as of 22:07, 30 July 2005

Revision as of 22:08, 30 July 2005

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{{BridgeTypePix|type_name = Trestle|image=Image:Wooden trestle.jpg|image_title=Trestles are useful as approaches to bridges over marshes and shallows|sibling_names=[[Beam bridge]], [[Clapper bridge]]|descendent_names=[[Viaduct]]|ancestor_names=[[Log bridge]]|carries=Heavy rail|span_range=Short|material=Timber, iron, steel, reenforced concrete, post-stressed concrete|movable=No|design=low|falsework=No}}

A '''trestle''' is a [[bridge]] that consists of a number of short spans, supported by splayed vertical elements and is usually for [[railroad]] use. Timber trestles were extensively used in the nineteenth century in mountainous areas and to traverse [[floodplains]] adjacent to rivers as approaches to [[bridge|bridges]]. These were typically constructed using peeled logs preserved with [[creosote]] as vertical elements and with bolted and spiked sawn timbers for bracing.

[[Image:Wooden_trestle_bridge_approach.JPG|thumb|left|200px|A classic wood trestle using logs and beams]]<br style="clear:left;" />

==Many replaced in the mid Twentieth Century==

[[Image:AlhambraTrestle.jpg|thumb|left|200px|A Steel trestle with [[plate girder bridge|plate girder]] spans and [[steel]] towers]]

Twentieth century construction eliminated much of the need for trestles by using far more extensive grading and tunnelling. The trestle shown to the left is a modern structure with a long expected lifetime compared to a wood trestle. Being fireproof in this brushy ___location is also an advantage. One of the longest trestle spans in current use is for railroad traffic crossing the [[Great Salt Lake]] in [[Utah]].