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Retractile Drawbridge
A retractile drawbridge is a rare type of moveable bridge in which the span is pulled away diagonally on rails. It is a variant of the retractable bridge. Only four examples are known to exist in the United States. It is believed to have been invented by T. Willis Pratt in the 1860s. References {{Bridge-type-stub Bridges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moveable Bridge
A moveable bridge, or movable bridge, is a bridge that moves to allow passage for boats or barges. In American English, the term is synonymous with , and the latter is the common term, but drawbridge can be limited to the narrower, historical definition used in some other forms of English, in which ''drawbridge'' refers to only a specific type of moveable bridge often found in castles . An advantage of making bridges moveable is the lower cost, due to the absence of high piers and long approaches. The principal disadvantage is that the traffic on the bridge must be halted when it is opened for passage of traffic on the waterway. For seldom-used railroad bridges over busy channels, the bridge may be left open and then closed for train passages. For small bridges, bridge movement may be enabled without the need for an engine. Some bridges are operated by the users, especially those with a boat, others by a bridgeman (or bridge tender); a few are remotely controlled using video- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retractable Bridge
A retractable bridge is a type of moveable bridge in which the deck can be rolled or slid backwards to open a gap while traffic crosses, usually a ship on a waterway. This type is sometimes referred to as a thrust bridge. Retractable bridges date back to medieval times. Due to the large dedicated area required for this type of bridge, this design is not common. A retractable design may be considered when the maximum horizontal clearance is required (for example, over a canal). Two remaining examples exist in New York City: the Carroll Street Bridge (built 1889) in Brooklyn, and the Borden Avenue Bridge in Queens. A recent example can be found at Queen Alexandra Dock in Cardiff, Wales, where the bridge is jacked upwards before being rolled on wheels. Helix Bridge at Paddington Basin in London is a more unusual example of the type, consisting of a glass shell supported in a helical steel frame, which rotates as it retracts. The Summer Street Bridge over Fort Point Channel in B ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
