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.
Bushcraft swing bridge
Advantages
As this type requires no counterweights, the complete weight is significantly reduced as compared to other moveable bridges.
Where sufficient channel is available to have individual traffic directions on each side, the likelihood of vessel-to-vessel collisions is reduced.
The central support is often mounted upon a berm along the axis of the watercourse, intended to protect the bridge from watercraft collisions when it is opened. This artificial island forms an excellent construction area for building the movable span as the construction will not impede channel traffic.
Disadvantages
For a symmetrical bridge, the central pier forms a hazard to navigation. Asymmetrical bridges may place the pivot near one side of the channel.
Where a wide channel is not available, a large portion of the bridge may be over an area that would be easily spanned by other means.
A wide channel will be reduced by the center pivot and foundation.
When open, the bridge will have to maintain its own weight as a balanced double cantilever, while when closed and in use for traffic, the live loads will be distributed as in a pair of conventional truss bridges, which may require additional stiffness in some members whose loading will be alternately in compression or tension.
If struck from the water near the edge of the span, it may rotate enough to cause safety problems (see Big Bayou Canot train disaster).
Belize City Swing Bridge, Belize City, Belize. Oldest such bridge in Central America and one of the few manually operated swing bridge in world still in operation. (Restored in 2000s)
Le pont tournant rue Dieu, across the Canal Saint-Martin in Paris, is a distinctive location in the 1938 film Hôtel du Nord, and is featured in the opening shot of the film.
Germany
Kaiser-Wilhelm-Brücke in Wilhelmshaven, built in 1907, with the length of 159m, it was once Europe's biggest swing bridge
India
Garden Reach Road Swing Bridge, for Calcutta Port, Kidderpore, Kolkata
Poira-Corjuem Bridge, for GSIDC, Corjuem, Goa by Rajdeep Buildcon Pvt. Ltd.
Portumna bridge, between County Galway and County Tipperary, Ireland
Italy
Ponte Girevole, Taranto (built in 1887) – a very unusual type, with two spans that separate at the bridge's center and pivot sideways from the bridge's outer ends.
Latvia
Kalpaka Tilts, Liepāja, connecting the city with the former Russian/Soviet port Karosta.
The Netherlands
The "Abtsewoudsebrug" in Delft, close to the Technische Universiteit Delft, is a bridge of this type. 52°0′5.71″N4°21′50.10″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)
Panama
A swing bridge at the Gatun Locks provides the only road passage over the Atlantic side of the Panama Canal. This is a small bridge that swings out from each side. Another larger swing bridge at the Miraflores Locks is on the Pacific side but is rarely used, having been supplanted by the Bridge of the Americas and the Centennial Bridge.
Ukraine
Varvarivskyi Bridge over Southern Bug in Mykolaiv, with Europe's largest span (134 m)
United Kingdom
In the UK, there is a legal definition in current statute as to what is, or is not a 'swing bridge'
Boothferry swing bridge at Boothferry, Yorkshire (see article for image)
Caernarfon swing bridge
Connaught Crossing in London Docklands, built as a low-rising swing bridge to allow marine traffic in the Royal Docks to pass at a place when the proximity of London City Airport meant a higher fixed bridge was not practicable.
Crosskeys Bridge - carries the A17 road over the River Nene in Lincolnshire
Kincardine Bridge - crossing the Firth of Forth from Falkirk council area to Kincardine-on-Forth, Fife
Leeds and Liverpool Canal Has a large number of swing bridges, especially between Bingley and Skipton and Burscough and Liverpool. Many are manually operated, carrying only farm tracks, but a significant number carry road traffic and are mechanised for boater operation.
Manchester Ship Canal at Latchford, Stockton Heath and Lower Walton in Warrington, and also slightly further west at Moore. Near the eastern end of the canal in Salford, the Barton Road Swing Bridge is adjacent to the Barton Swing Aqueduct - a 234-foot, 800-ton trough holding some 800 tons of water (retained by gates at either end) swings so that it is at right angles to the Bridgewater Canal to allow ships to pass up the Ship Canal.
Tyne swing bridge at Newcastle Upon Tyne, which has an 85.7 metre cantilevered span with a central axis of rotation able to move through 90° to allow vessels to pass on either side of it.
Operation of the Sulhamstead Tyle Mill swing bridge on the Kennet & Avon Canal
United States
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.
Alanson Swing Bridge, billed as the world's shortest swing bridge, crossing the Crooked River in Alanson, Michigan
Berkley–Dighton Bridge (1896), connecting the towns of Berkley and Dighton, Massachusetts, crossing the Taunton River; removed in 2010. The replacement bridge is not a swing structure.
Gasparilla Island Bridge, Built in 1958, this bridge is used for passage between Placida, FL to the island of Boca Grande. A replacement bridge is under construction, with projected completion in August 2016.
North Landing Bridge, built in 1950s, on the Atlantic Intracoastal Waterway where it forms part of the border between Chesapeake and Virginia Beach, Virginia,
Songo Locks Bridge, Naples, Maine; carries Songo Lock Road over the Songo River just upstream of the lock. Not to be confused with a former swing bridge about two miles upstream which carried US 302 until replaced with a fixed span in May 2012.
South Bristol, Maine Asymmetric swing bridge connecting Rutherford Island to the mainland.
Southport, ME connects Southport Island to Boothbay Harbor on Route 27.
Spokane Street Bridge over the Duwamish Waterway in Seattle, Washington, built 1991. Features two reinforced concrete, serial swing spans, each rotating 45 degrees
Woods Memorial Bridge over the Beaufort River in Beaufort, South Carolina
Yancopin Bridge, Arkansas River, southeastern Arkansas. Former Missouri Pacific railroad bridge with separate vertical-lift and swing trusses now part of rail-trail; swing span now manually operated
State Hwy 87 northbound bridge the eastern boundary of Bridge City, Texas
