Swing bridge

A swing bridge (or swing span bridge) is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its center of gravity, about which the swing span (turning span) can then pivot horizontally as shown in the animated illustration to the right. Small swing bridges as found over canals may be pivoted only at one end, opening as would a gate, but require substantial underground structure to support the pivot.

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Swing bridge

Ancestor	Truss bridge, cantilever bridge
Related	Other moving types: Bascule bridge, drawbridge, jetway, vertical-lift bridge, tilt bridge
Descendant	Gate-swing bridge – see Puente de la Mujer
Carries	Automobile, truck, light rail, heavy rail
Span range	Short
Material	Steel
Movable	Yes
Design effort	Medium
Falsework required	No

In its closed position, a swing bridge carrying a road or railway over a river or canal, for example, allows traffic to cross. When a water vessel needs to pass the bridge, road traffic is stopped (usually by traffic signals and barriers), and then motors rotate the bridge horizontally about its pivot point. The typical swing bridge will rotate approximately 90 degrees, or one-quarter turn; however, a bridge which intersects the navigation channel at an oblique angle may be built to rotate only 45 degrees, or one-eighth turn, in order to clear the channel.