drawbridge

drawbridge:

see bridge.

drawbridge

At the entrance to fortifications, a bridge over the moat or ditch, hinged and provided with a raising and lowering mechanism so as to hinder or permit passage.

See also: Bridge

Drawbridge

 

a bridge with a movable span to permit the passage of ships. Drawbridges are usually built across rivers traveled by large ships when conditions make it technically and economically inadvisable to construct a bridge on high piers and with long approaches. The movable span of a drawbridge can be of the vertical-lift, swing, bascule, balance-beam, or rolling-lift type; the choice of type depends on local conditions. Construction of a drawbridge span requires either massive piers or towers to house the mechanisms and engines required for moving the span. Electric and hydraulic drives are the most common, and drawbridges are often equipped with backup drives from internal-combustion engines. The movable span generally has light-duty structural members, with trusses or beams of steel or lightweight alloys.

REFERENCE

Kryzhanovskii, V. I. Razvodnye mosty. Moscow, 1967.

drawbridge

[′drȯ‚brij]

(civil engineering)

Any bridge that can be raised, lowered, or drawn aside to provide clear passage for ships.

drawbridge

drawbridge

At the entrance of fortifications, a bridge over the moat or ditch, hinged and provided with a raising and lowering mechanism so as to hinder or permit passage.

drawbridge

a bridge that may be raised to prevent access or to enable vessels to pass