definition
strict definition
retractable bridge
A movable bridge whose deck opens by sliding back from the channel over or under its approach.
A retractable bridge is a movable bridge whose deck opens by sliding back away from the channel. It requires a mechanism equal to the deck in length for fitting the deck above or below the approach deck while open.
The span slides away from the navigation opening rather than rotating upward or sideways. Its withdrawn position lies above or below the approach deck.
The arrangement needs space and a mechanism to receive the retracted span. The moving deck retains its form while its position changes.
Related definitions
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bascule bridge
A movable bridge with one or two leaves that rise on hinges with assistance from counterweights. -
curling bridge
A movable bridge with a flexible or segmented span which opens by curling vertically. -
drawbridge
A hinged bridge lifted at its free end by chains, cables, or ropes, without a counterweight at the hinge. -
folding bridge
A movable bridge with a segmented span that folds horizontally like an accordion to open the crossing. -
rolling bascule bridge
A movable bridge whose span rises as large gears roll along a shoreline rack, without a fixed hinge. -
submersible bridge
A movable bridge whose span sinks below water to allow boat traffic to move over it. -
swing bridge
A movable bridge with a span that turns horizontally about a fixed pivot at its center or one end. -
table bridge
A movable bridge whose span is pushed upward from below at both ends, usually by hydraulic pillars. -
tilt bridge
A movable bridge with a curved span that forms an arch when rotated at the ends. -
transporter bridge
A bridge which conveys traffic across its span via gondolas suspended from a high track or cables. -
vertical-lift bridge
A movable bridge whose level span is raised along towers at its ends, usually by counterweighted cables.