Swing span
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| 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 |
A swing 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 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.
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.
The "Abtsewoudsebrug" in Delft, close to the Technische Universiteit Delft, is a bridge of this type. 52°0′5.71″N 4°21′50.10″E / 52.0015861°N 4.3639167°E
There's another one on the channel between Ghent (Belgium) and Terneuzen (The Netherlands) at Sas Van Gent.
Many inner cities have swing bridges, since these require less street space than other types of bridges.
(n.b. "swing bridge" in New Zealand refers to a flexible walking track bridge which "swings" as you walk across)
In the UK, there is a legal definition in current statute as to what is, or is not a 'swing bridge'
The largest double swing-span bridge in the United States is the 3,250 feet (990 m) long, 450 feet (140 m) navigable span, 60 feet (18 m) clearance George P. Coleman Memorial Bridge.
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Wikipedia