What is "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.

Bascule bridge, a counterpoise or balanced drawbridge, which is opened by sinking the counterpoise and thus lifting the footway into the air.

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, pavement, and possibly to E. brow.]

1. A structure, usually of wood, stone, brick, or iron, erected over a river or other water course, or over a chasm, railroad, etc., to make a passageway from one bank to the other.

2. Anything supported at the ends, which serves to keep some other thing from resting upon the object spanned, as in engraving, watchmaking, etc., or which forms a platform or staging over which something passes or is conveyed.

3. (Mus.) The small arch or bar at right angles to the strings of a violin, guitar, etc., serving of raise them and transmit their vibrations to the body of the instrument.

4. (Elec.) A device to measure the resistance of a wire or other conductor forming part of an electric circuit.

5. A low wall or vertical partition in the fire chamber of a furnace, for deflecting flame, etc.; -- usually called a bridge wall.

   Aqueduct bridge. See Aqueduct.

   Asses' bridge, Bascule bridge, Bateau bridge. See under Ass, Bascule, Bateau.

   Bridge of a steamer (Naut.), a narrow platform across the deck, above the rail, for the convenience of the officer in charge of the ship; in paddlewheel vessels it connects the paddle boxes.

   Bridge of the nose, the upper, bony part of the nose.

   Cantalever bridge. See under Cantalever.

   Draw bridge. See Drawbridge.

   Flying bridge, a temporary bridge suspended or floating, as for the passage of armies; also, a floating structure connected by a cable with an anchor or pier up stream, and made to pass from bank to bank by the action of the current or other means.

   Girder bridge or Truss bridge, a bridge formed by girders, or by trusses resting upon abutments or piers.

   Lattice bridge, a bridge formed by lattice girders.

   Pontoon bridge, Ponton bridge. See under Pontoon.

   Skew bridge, a bridge built obliquely from bank to bank, as sometimes required in railway engineering.

   Suspension bridge. See under Suspension.

   Trestle bridge, a bridge formed of a series of short, simple girders resting on trestles.

   Tubular bridge, a bridge in the form of a hollow trunk or rectangular tube, with cellular walls made of iron plates riveted together, as the Britannia bridge over the Menai Strait, and the Victoria bridge at Montreal.

   Wheatstone's bridge (Elec.), a device for the measurement of resistances, so called because the balance between the resistances to be measured is indicated by the absence of a current in a certain wire forming a bridge or connection between two points of the apparatus; -- invented by Sir Charles Wheatstone.

n. A movable bridge consisting of one or two opening leaf equipped with balancing counterweight that ease and speedy up their operation.

A bascule bridge (commonly referred to as a drawbridge) is a moveable bridge with a counterweight that continuously balances a span, or "leaf", throughout its upward swing to provide clearance for boat traffic. It may be single or double leafed.

The name comes from the French term for balance scale, which employs the same principle. Bascule bridges are the most common type of movable span because they open quickly and require relatively little energy to operate, while providing the possibility for unlimited vertical clearance for marine traffic.