Bascule bridge

Bascule bridge
This animation shows the movement of a double leaf bascule.
This animation shows the movement of a double leaf bascule.
Ancestor Drawbridge, Plate girder bridge, cantilever bridge
Related Lift bridge, swing bridge
Descendant None
Carries Pedestrian, automobile, truck, light rail, heavy rail
Span range Short
Material Steel
Movable Yes
Design effort Medium
Falsework required Site and prefabrication specific

A bascule bridge (sometimes referred to as a drawbridge) 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.

Bascule is a French term for seesaw and balance, and bascule bridges operate along the same principle. They are the most common type of movable bridge in existence because they open quickly and require relatively little energy to operate.

Bascule bridges may be single or double leaf. Both have any truss structure and counterweights below the deck.



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 in Saint Petersburg was the first large bascule bridge, opened in 1850.[citation needed] 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 across the Neva was opened).


Animation of a rolling lift bridge (such as the Pegasus Bridge)

Counterweights 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 called a trunnion to raise. This bridge type is sometimes called the 'Chicago 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 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.[1]


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

Tower Bridge

Tower Bridge across the Thames in London, UK is a famous bascule bridge. Originally, Tower Bridge was a hydraulically 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.[2]


See also


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Look at other dictionaries:

  • Bascule bridge — Bridge Bridge (br[i^]j), n. [OE. brig, brigge, brug, brugge, AS. brycg, bricg; akin to Fries. bregge, D. brug, OHG. brucca, G. br[ u]cke, Icel. bryggja pier, bridge, Sw. brygga, Dan. brygge, and prob. Icel. br[=u] bridge, Sw. & Dan. bro bridge,… …   The Collaborative International Dictionary of English

  • Bascule bridge — Bascule Bas cule (b[a^]s k[ u]l), n. [F., a seesaw.] In mechanics, an apparatus on the principle of the seesaw, in which one end rises as the other falls. [1913 Webster] {Bascule bridge}, a counterpoise or balanced drawbridge, which is opened by… …   The Collaborative International Dictionary of English

  • bascule bridge — n. a kind of drawbridge counterweighted so that it can be raised and lowered easily * * * …   Universalium

  • bascule bridge — n. a kind of drawbridge counterweighted so that it can be raised and lowered easily …   English World dictionary

  • bascule bridge — n. a type of drawbridge which is raised and lowered using counterweights. Etymology: F, earlier bacule see saw f. battre bump + cul buttocks * * * noun : a counterpoised or balanced drawbridge * * * bascule bridge noun A bridge with one or more… …   Useful english dictionary

  • Bascule Bridge — The Bascule Bridge is a paved one lane highway bridge in Westport, Massachusetts, USA. Route 88 passes over the bridge from Westport Point and Wood Point in southern Westport to the Horseneck Beach State Reservation, connecting with John Reed… …   Wikipedia

  • bascule bridge — bridge that is counterpoised in order to facilitate its raising and lowering, balanced drawbridge …   English contemporary dictionary

  • bascule bridge — [ baskju:l] noun a type of bridge with a section which can be raised and lowered using counterweights. Origin C19: from Fr. (earlier bacule), see saw , from battre to bump + cul buttocks …   English new terms dictionary

  • Mystic River Bascule Bridge — Facing west on the bridge Official name Mystic River Bascule Bridge Carries …   Wikipedia

  • Cherry Street Strauss Trunnion Bascule Bridge — The Cherry Street Bascule Bridge Other name(s) Cherry Street Bridge Carries vehicluar and pedestrian …   Wikipedia

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