Moveable bridge
Encyclopedia
A moveable bridge is a bridge
that moves to allow passage for (usually) boats or barges. An advantage of making bridges movable include lower price, 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 passages. 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; a few remotely using video-cameras and loudspeakers. Generally, the bridges are powered by electric motors, whether operating winches, gearing, or hydraulic pistons. While moveable bridges in their entirety may be quite long, the length of the moveable portion is restricted by engineering and cost considerations to a few hundred feet.
There are often traffic light
s for the road and water traffic, and moving barriers for the road traffic.
In the United States, regulations governing the operation of moveable bridges, for example, hours of operation and how much advance notice must be given by water traffic, are listed in title 33 of the Code of Federal Regulations
; temporary deviations are published in the Coast Guard's Local Notice to Mariners.
Bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
that moves to allow passage for (usually) boats or barges. An advantage of making bridges movable include lower price, 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 passages. 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; a few remotely using video-cameras and loudspeakers. Generally, the bridges are powered by electric motors, whether operating winches, gearing, or hydraulic pistons. While moveable bridges in their entirety may be quite long, the length of the moveable portion is restricted by engineering and cost considerations to a few hundred feet.
There are often traffic light
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...
s for the road and water traffic, and moving barriers for the road traffic.
In the United States, regulations governing the operation of moveable bridges, for example, hours of operation and how much advance notice must be given by water traffic, are listed in title 33 of the Code of Federal Regulations
CFR
CFR can refer to:* Code of Federal Regulations of the United States* Council on Foreign Relations, U.S. foreign policy think tank* Campaign finance reform in the United States* Cost and Freight, word used in international commerce...
; temporary deviations are published in the Coast Guard's Local Notice to Mariners.
Types of moving bridges
- DrawbridgeDrawbridgeA drawbridge is a type of movable bridge typically associated with the entrance of a castle surrounded by a moat. The term is often used to describe all different types of movable bridges, like bascule bridges and lift bridges.-Castle drawbridges:...
- the bridge deck is hinged on one end - Bascule bridgeBascule bridgeA bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....
- a drawbridge hinged on pins with a counterweight to facilitate raising - Folding bridgeFolding bridgeA folding bridge is a type of movable bridge.An example of a folding bridge is the Hörnbrücke in the city of Kiel in the German state of Schleswig-Holstein. It is a three-segment bascule bridge that folds in the shape of the letter N.-See also:*Movable bridge for a list of other movable bridge types...
- a drawbridge with multiple sections that collapse together horizontally - Curling bridgeThe Rolling BridgeThe Rolling Bridge is a type of curling movable bridge completed in 2004 as part of the Grand Union Canal office & retail development project at Paddington Basin, London...
- a drawbridge with multiple sections that curl vertically - Vertical-lift bridge - the bridge deck is lifted up by counterweighted cables mounted on towers
- Table bridgeTable bridgeA table bridge is a moveable bridge in which the deck moves along the vertical axis. Hydraulic pillars under the bridge raise the bridge deck to allow barge traffic to pass beneath it. In contrast to a lift bridge, where the deck is pulled upwards along towers, the deck of a table bridge is pushed...
- a lift bridge with the lifting mechanism mounted underneath it - Retractable bridgeRetractable bridgeA retractable bridge is a type of movable bridge in which the deck can be rolled or slid backwards to open a gap for crossing traffic, usually a ship on a waterway. This type is sometimes referred to as a thrust bridge....
(Thrust bridge) - the bridge deck is retracted to one side - Rolling bascule bridgePegasus BridgePegasus Bridge is a bascule bridge , built in 1934, that crossed the Caen Canal, between Caen and Ouistreham, in Normandy, France....
- an unhinged drawbridge lifted by the rolling of a large gear segment along a horizontal rackRack and pinionA rack and pinion is a type of linear actuator that comprises a pair of gears which convert rotational motion into linear motion. A circular gear called "the pinion" engages teeth on a linear "gear" bar called "the rack"; rotational motion applied to the pinion causes the rack to move, thereby... - Submersible bridgeSubmersible bridgeA submersible bridge is a type of movable bridge that lowers the bridge deck below the water level to permit waterborne traffic to use the waterway. This differs from a lift bridge or table bridge, which operate by raising the roadway. Two submersible bridges exist across the Corinth Canal, one at...
- also called a ducking bridge, the bridge deck is lowered down into the water - Tilt bridgeTilt bridgeA tilt bridge is a type of moveable bridge which rotates about fixed endpoints rather than lifting or bending, as with a drawbridge. For this rotation to serve a useful purpose, namely facilitating boat traffic underneath, its deck must follow a curved shape...
- the bridge deck, which is curved and pivoted at each end, is lifted up at an angle - Swing bridgeSwing bridgeA swing bridge is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its centre of gravity, about which the turning span can then pivot horizontally as shown in the animated illustration to the right...
- the bridge deck rotates around a fixed point, usually at the center, but may resemble a gate in its operation - Transporter bridgeTransporter bridgeA transporter bridge is a type of movable bridge that carries a segment of roadway across a river. The gondola is slung from a tall span by wires or a metal frame. The design has been used to cross navigable rivers or other bodies of water, where there is a requirement for ship traffic to be...
- a structure high above carries a suspended, ferryFerryA ferry is a form of transportation, usually a boat, but sometimes a ship, used to carry primarily passengers, and sometimes vehicles and cargo as well, across a body of water. Most ferries operate on regular, frequent, return services...
-like structure - Jet bridge - a passenger bridge to an airplane. One end is mobile with height, yaw, and tilt adjustments on the outboard end
Accidents
- April 23, 1853 – Rancocas CreekRancocas CreekRancocas Creek is a tributary of the Delaware River in southwestern New Jersey in the United States. The creek's main stem is long, with a North Branch of and a South Branch flowing...
, New Jersey: Engineer of Camden & Amboy's 2 p.m. train out of Philadelphia, Pennsylvania missed stop signals and ran his train off an open drawspan at Rancocas Creek. There were no fatalities.
- September 15, 1958 - Elizabethport, New Jersey: Central Railroad of New JerseyCentral Railroad of New JerseyThe Central Railroad of New Jersey , commonly known as the Jersey Central Lines or CNJ, was a Class I railroad with origins in the 1830s, lasting until 1976 when it was absorbed into Conrail with the other bankrupt railroads of the Northeastern United States...
(CNJ) commuter train #3314 from Bay Head JunctionBay Head (NJT station)Bay Head is a railway station in Bay Head, New Jersey. This station is served by trains on New Jersey Transit's North Jersey Coast Line, and it is the southern terminus for the line. The rail yard contains of wetland inside the loop formed by the tracks used to turn around the trains. The rail...
to Jersey City ran a stop signal and an open derail protecting the Newark Bay 4-span lift bridge, and the train's two diesel locomotives and two of five passenger cars went into Newark Bay through one of the open spans. Four crewmen, including the engineer and fireman, and 44 passengers died by drowning.
See also
- Bailey bridgeBailey bridgeThe Bailey bridge is a type of portable, pre-fabricated, truss bridge. It was developed by the British during World War II for military use and saw extensive use by both British and the American military engineering units....
, Medium Girder BridgeMedium Girder BridgeThe Medium Girder Bridge is a lightweight, man portable bridge and can be assembled without help from heavy equipment. In addition, it is also a deck type, two-girder bridging system capable of carrying loads up to and including Main battle tanks .MGB was originally produced by Fairey Engineering...
, and Armoured vehicle-launched bridgeArmoured vehicle-launched bridgeAn armoured vehicle-launched bridge is a combat support vehicle, sometimes regarded as a subtype of combat engineering vehicle, designed to assist militaries in rapidly deploying tanks and other armoured fighting vehicles across rivers. The AVLB is usually a tracked vehicle converted from a tank...
- transportable or relocatable bridges. - Barton Swing AqueductBarton Swing AqueductThe Barton Swing Aqueduct is a moveable navigable aqueduct in Barton upon Irwell in Greater Manchester, England. It carries the Bridgewater Canal across the Manchester Ship Canal. The swinging action allows large vessels using the Manchester Ship Canal to pass underneath and smaller narrowboats to...
, a swing bridge carrying barge traffic over a ship canal. - Pontoon bridgePontoon bridgeA pontoon bridge or floating bridge is a bridge that floats on water and in which barge- or boat-like pontoons support the bridge deck and its dynamic loads. While pontoon bridges are usually temporary structures, some are used for long periods of time...
- may be built with a barge or boat-like section that may be moved for passage. - Lists of rail accidents