Bascule bridge
Overview
 
A bascule bridge is a moveable bridge
Moveable bridge
A moveable bridge is a bridge that moves to allow passage for 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...

 with a counterweight that continuously balances the span
Span (architecture)
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...

, or "leaf," throughout the entire upward swing in providing clearance for boat traffic.

Bascule is a French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 term for seesaw
Seesaw
A seesaw is a long, narrow board pivoted in the middle so that, as one end goes up, the other goes down.-Mechanics:Mechanically a seesaw is a lever and fulcrum....

 and balance
Weighing scale
A weighing scale is a measuring instrument for determining the weight or mass of an object. A spring scale measures weight by the distance a spring deflects under its load...

, and bascule bridges operate along the same principle. They are the most common type of movable bridge
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...

 in existence because they open quickly and require relatively little energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 to operate.

Bascule bridges may be single or double leaf.
Encyclopedia
A bascule bridge is a moveable bridge
Moveable bridge
A moveable bridge is a bridge that moves to allow passage for 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...

 with a counterweight that continuously balances the span
Span (architecture)
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...

, or "leaf," throughout the entire upward swing in providing clearance for boat traffic.

Bascule is a French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 term for seesaw
Seesaw
A seesaw is a long, narrow board pivoted in the middle so that, as one end goes up, the other goes down.-Mechanics:Mechanically a seesaw is a lever and fulcrum....

 and balance
Weighing scale
A weighing scale is a measuring instrument for determining the weight or mass of an object. A spring scale measures weight by the distance a spring deflects under its load...

, and bascule bridges operate along the same principle. They are the most common type of movable bridge
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...

 in existence because they open quickly and require relatively little energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

 to operate.

Bascule bridges may be single or double leaf. Both have any truss
Truss
In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...

 structure and counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...

s below the deck.

History

Although the bascule bridge has been in use since ancient times, it was not until the 1850s that engineers developed the ability to move very long, heavy spans quickly enough for practical application. The Blagoveshchensky Bridge across the Neva River
Neva River
The Neva is a river in northwestern Russia flowing from Lake Ladoga through the western part of Leningrad Oblast to the Neva Bay of the Gulf of Finland. Despite its modest length , it is the third largest river in Europe in terms of average discharge .The Neva is the only river flowing from Lake...

 in Saint Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

 was the first large bascule bridge, opened in 1850. Since then, all bridges across the Neva and other major rivers in the city (21 in total) were bascule to facilitate navigation, which prevented the city's inhabitants from travelling across the river at night (this remained so until 2003 when the first cable-stayed bridge
Cable-stayed bridge
A cable-stayed bridge is a bridge that consists of one or more columns , with cables supporting the bridge deck....

 across the Neva was opened).

Design

Counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...

s may be located above the bridge or below the deck of the bridge. There are two common designs of bascule bridge. One is the fixed-trunnion bascule design, which is where the bridge rotates around a large axle
Axle
An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...

 called a trunnion to raise. This bridge type is sometimes called the 'Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...

 bascule' as this type was developed and perfected there and is used for many of that city's river crossings. Joseph Strauss was a key person who worked on improving the trunnion bascule bridge. Another form of bascule bridge is the Scherzer rolling lift bridge, also known as a Rolling Bascule Bridge. The city of Joliet, Illinois
Joliet, Illinois
Joliet is a city in Will and Kendall Counties in the U.S. state of Illinois, located southwest of Chicago. It is the county seat of Will County. As of the 2010 census, the city was the fourth-most populated in Illinois, with a population of 147,433. It continues to be Illinois' fastest growing...

 has a number of this structure type. The Scherzer rolling lift bridge essentially rolls or rocks like a simple rocking chair on a track to raise.

Types

  • Scherzer rolling lift bascule bridge
  • Rall bascule bridge, patented by Theodore Rall in 1901.
  • Strauss bascule bridge, patented by Joseph Strauss.
  • Chicago or fixed-trunnion bascule bridge.

Tower Bridge


Tower Bridge across the Thames in London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

, UK is a famous bascule bridge. Originally, Tower Bridge was a hydraulically
Hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...

 operated bridge, using steam power from coal-burning boilers to pump river water into six hydraulic accumulators so that power was readily available when required. The water for the boilers was provided by a well. The hydraulic accumulators powered the bascule engines, which raised and lowered the bascules. Today, the bascule mechanism is driven by oil and electricity rather than by water and steam.

See also

  • Bridge
    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...

  • Drawbridge
    Drawbridge
    A 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:...

  • Joseph Strauss
  • List of bascule bridges
  • Moveable bridge
    Moveable bridge
    A moveable bridge is a bridge that moves to allow passage for 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 a list of other movable bridge types.
  • Pegasus Bridge
    Pegasus Bridge
    Pegasus Bridge is a bascule bridge , built in 1934, that crossed the Caen Canal, between Caen and Ouistreham, in Normandy, France....

     for an example of a rolling bascule bridge, employing a rack and pinion
    Rack and pinion
    A 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...

     rather than hinge
    Hinge
    A hinge is a type of bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation. Hinges may be made of flexible material or of moving components...

    pins.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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