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A cable-stayed bridge is a bridge that consists of one or more columns (normally referred to as towers or pylons), with cables supporting the bridge deck.
There are two major classes of cable-stayed bridges: In a harp design, the cables are made nearly parallel by attaching cables to various points on the tower(s) so that the height of attachment of each cable on the tower is similar to the distance from the tower along the roadway to its lower attachment.
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A cable-stayed bridge is a bridge that consists of one or more columns (normally referred to as towers or pylons), with cables supporting the bridge deck.
There are two major classes of cable-stayed bridges: In a harp design, the cables are made nearly parallel by attaching cables to various points on the tower(s) so that the height of attachment of each cable on the tower is similar to the distance from the tower along the roadway to its lower attachment. In a fan design, the cables all connect to or pass over the top of the tower(s).
The cable-stay design is the optimum bridge for a span length between that of cantilever bridges and suspension bridges. Within this range of span lengths a suspension bridge would require a great deal more cable, while a full cantilever bridge would require considerably more material and be substantially heavier. Of course, such assertions are not absolute for all cases.
History of development
Cable-stayed bridges can be dated back to the 1784 design of a timber bridge by German carpenter C.T. Loescher. Many early suspension bridges were of hybrid suspension and cable-stayed construction, including the 1817 footbridge at Dryburgh Abbey, and the later Albert Bridge (1872) and Brooklyn Bridge (1883). Their designers found that the combination of technologies created a stiffer bridge, and John A. Roebling took particular advantage of this to limit deformations due to railway loads in the Niagara Falls Suspension Bridge.
The earliest known example of a true cable-stayed bridge in the United States is E.E. Runyon's extant steel (or perhaps iron) bridge with wooden stringers and decking in Bluff Dale, Texas (1890). In the twentieth century, early examples of cable-stayed bridges included A. Gisclard's unusual Cassagnes bridge (1899), where the horizontal part of the cable forces is balanced by a separate horizontal tie cable, preventing significant compression in the deck, and G. Leinekugel le Coq's bridge at Lezardrieux in Brittany (1924). Eduardo Torroja designed a cable-stayed aqueduct at Tempul in 1926. Albert Caquot's 1952 concrete-decked cable-stayed bridge over the Donzére-Mondragon canal at Pierrelatte is one of the first of the modern type, but had little influence on later development. The steel-decked bridge designed at Strömsund by Franz Dischinger (1955) is therefore more often cited as the first modern cable-stayed bridge.
Other key pioneers included Fabrizio de Miranda, Riccardo Morandi and Fritz Leonhardt. Early bridges from this period used very few stay cables, as in the Theodor Heuss Bridge (1958). However, this involves substantial erection costs, and more modern structures tend to use many more cables to ensure greater economy.
Comparison with suspension bridge
A multiple-tower cable-stayed bridge may appear similar to a suspension bridge, but in fact is very different in principle and in the method of construction. In the suspension bridge, a large cable is made up by "spinning" small diameter wires between two towers, and at each end to anchorages into the ground or to a massive structure. These cables form the primary load-bearing structure for the bridge deck. Before the deck is installed, the cables are under tension from only their own weight. Smaller cables or rods are then suspended from the main cable, and used to support the load of the bridge deck, which is lifted in sections and attached to the suspender cables. As this is done the tension in the cables increases, as it does with the live load of vehicles or persons crossing the bridge. The tension on the cables must be transferred to the earth by the anchorages, which are sometimes difficult to construct due to poor soil conditions.
Image:Bridge-suspension.svg|Suspension bridge
Image:Bridge-fan-cable-stayed.svg|Cable-stayed bridge, fan design
Image:Bridge-harp-cable-stayed.svg|Cable-stayed bridge, harp design
In the cable-stayed bridge, the towers form the primary load-bearing structure. A cantilever approach is often used for support of the bridge deck near the towers, but areas further from them are supported by cables running directly to the towers. This has the disadvantage, compared to the suspension bridge, that the cables pull to the sides as opposed to directly up, requiring the bridge deck to be stronger to resist the resulting horizontal compression loads; but has the advantage of not requiring firm anchorages to resist a horizontal pull of the cables, as in the suspension bridge. All static horizontal forces are balanced so that the supporting tower does not tend to tilt or slide, needing only to resist such forces from the live loads.
Key advantages of the cable-stayed form are as follows:
- much greater stiffness than the suspension bridge, so that deformations of the deck under live loads are reduced
- can be constructed by cantilevering out from the tower - the cables act both as temporary and permanent supports to the bridge deck
- for a symmetrical bridge (i.e. spans on either side of the tower are the same), the horizontal forces balance and large ground anchorages are not required
A further advantage of the cable-stayed bridge is that any number of towers may be used. This bridge form can be as easily built with a single tower, as with a pair of towers. However, a suspension bridge is usually built only with a pair of towers.
Variations
Side-spar cable-stayed bridge
A side-spar cable-stayed bridge uses a central tower supported on only one side. The example shown in that article is not significantly different in structure from a conventional cable-stayed bridge, although this concept could allow the construction of a curved bridge.
Cantilever-spar cable-stayed bridge
Far more radical in its structure, the Redding, California Sundial Bridge is a pedestrian bridge that uses a single cantilever spar on one side of the span, with cables on one side only to support the bridge deck. Unlike the other cable stayed types shown this bridge exerts considerable overturning force upon its foundation and the spar must resist the bending caused by the cables, as the cable forces are not balanced by opposing cables. The spar of this particular bridge forms the gnomon of a large garden sundial. Related bridges by the architect Santiago Calatrava include the Puente del Alamillo (1992), Puente de la Mujer (2001), and Chords Bridge (2008).
Multiple span cable-stayed bridge
Cable-stayed bridges with more than three spans involve significantly more challenging designs than do 2-span or 3-span structures.
In a 2-span or 3-span cable-stay bridge, the loads from the main spans are normally anchored back near the end abutments by stays in the end spans. For more spans, this isn't the case, and the bridge structure is less stiff overall. This can create difficulties both in the design of the deck and the pylons.
Examples of multiple span structures where this is the case include Ting Kau Bridge, where additional 'cross-bracing' stays are used to stabilise the pylons; Millau Viaduct and Mezcala Bridge, where twin-legged towers are used; and General Rafael Urdaneta Bridge, where very stiff multi-legged frame towers were adopted. A similar situation with a suspension bridge is found at both the Great Seto Bridge and San Francisco – Oakland Bay Bridge where additional anchorage piers are required after every set of three suspension spans - this solution can also be adapted for cable-stayed bridges.
Extradosed bridge
The extradosed bridge is a cable-stayed bridge but with a more substantial bridge deck that being stiffer and stronger allows the cables to be omitted close to the tower and for the towers to be lower in proportion to the span.
Cable-stayed cradle system bridge
A cradle system carries the strands within the stays from bridge deck to bridge deck, as a continuous element, eliminating anchorages in the pylons. Each epoxy-coated steel strand is carried inside the cradle in a one-inch steel tube. Each strand acts independently, allowing for removal, inspection and replacement of individual strands. The first two such bridges are the Veterans' Glass City Skyway, completed 2007, and the Penobscot Narrows Bridge, completed 2006.
Related bridge types
Self anchored suspension bridge
A self-anchored suspension bridge has some similarity in principle to the cable stayed type in that tension forces that prevent the deck from dropping are converted into compression forces vertically in the tower and horizontally along the deck structure. It is also related to the suspension bridge in having arcuate main cables with suspender cables, although the self-anchored type lacks the heavy cable anchorages of the ordinary suspension bridge. Unlike either a cable stayed bridge or a suspension bridge, the self-anchored suspension bridge must be supported by falsework during construction and so it is more expensive to construct.
Notable cable-stayed bridges
See also: List of largest cable-stayed bridges and :Category:Cable-stayed bridges
- Arthur Ravenel, Jr. Bridge: the longest cable-stayed bridge in the Western Hemisphere, spanning the Cooper River in Charleston, South Carolina.
- Bandra Worli Sea-Link: The new 8-lane twin carriageway cable-stayed bridge of the sea-link project and the West Island Freeway system, under construction, connects Greater Mumbai, India to the western suburbs.
- Cable Bridge: The first cable-stayed bridge in the United States, crosses the Columbia River and connects Pasco, Washington to Kennewick, Washington
- Centennial Bridge: a six-lane vehicular bridge that crosses the Panama Canal with a total length of 1.05 km (3,451 ft).
- Denver Millennium Bridge: A long pedestrian bridge which won the Gold Award in 2003 from the New York Association of Consulting Engineers. The bridge is a focal point of the film "Nowhereland" starring Eddie Murphy.
- Kap Shui Mun Bridge carries both road and railway traffic, with a main span of 430 metres and an overall length of 1323 metres, connecting Ma Wan and Lantau Island in Hong Kong as part of the Lantau Link serving Hong Kong International Airport.
- Indiano Bridge over the Arno River in Florence, Italy, 1978, is the first earth-anchored cable-stayed steel bridge in the world with central planes of cables, single inclined masts, vented deck. Central span of 210 m.
- Luling Bridge over the Mississippi River in Destrehan, Louisiana; it was the first cable-stayed bridge in the United States carrying an interstate highway
- Millau Viaduct is the bridge with the tallest piers in the world: 341 metres tall (1,118 ft) and roadway 270 metres high (886 ft), spanning the Tarn River in France. With a total length of 2460 m and seven towers, it also has the longest cable-stayed suspended deck in the world.
- New Railroad Bridge: the first bridge in Europe to use cable-stayed girder system in the railroad industry, connects two banks of Sava river in Belgrade.
- North Avenue Bridge over the Chicago River in Chicago, Illinois, U.S.A. utilizes cable-stayed elements to avoid the full-size abutments required for a pure suspension bridge, while providing additional support via a suspension cable to minimize the height of the bridge's support towers.
- Nový Most: The world's longest cable-stayed bridge in category with one pylon and with one cable-stayed plane, spanning Danube river in Bratislava, Slovakia. The main span is 303 metres, total length 430.8 metres. The only member of World Federation of Great Towers that is primarily used as a bridge. It houses a flying-saucer restaurant at the top of pylon 85 metres high.
- Octavio Frias de Oliveira bridge over the Pinheiros River in São Paulo, 2008. It has a -high pylon under which two stayed roads cross each other turning 90° to the opposite bank of the river.
- Oresund Bridge, a combined two-track rail and four-lane road bridge with a main span of 490 metres and a total length of 7.85 km, crossing the Öresund strait between Malmö, Sweden and the Danish Capital Region.
- Penang Bridge in Malaysia is the longest bridge in South East Asia, with its longest span measuring 225 m. Currently being upgraded.
- Rande Bridge in Spain near Vigo is the highway cable stayed bridge with the longest and slenderest span in the world at the time of construction (1977). Three long spans of 148 m + 400m + 148 m. Pylons in concrete, girder in composite steel-concrete.
- Rio-Antirio bridge with a total length of 2880 m and four towers, this is the bridge with the second longest cable-stayed suspended deck (2258 m long) in the world, spanning the Gulf of Corinth near Patra, Greece.
- Second Severn Crossing between England and Wales is 3.186 miles (5.127 km) miles long, consisting of a single central navigation span over the "Shoots" channel and approach viaducts on either side.
- Skybridge is the world's longest transit-only bridge, spanning the Fraser River between New Westminster and Surrey, BC, Canada.
- Sundial Bridge is an award-winning single spar pedestrian bridge spanning the Sacramento River in Redding, California.
- Sunshine Skyway Bridge is the world's longest bridge with a cable-stayed main span; carries I-275 across Tampa Bay south of St. Petersburg, Florida, United States. The very similar looking Oresund bridge is slightly shorter but has a longer main span.
- Surgut Bridge is the longest one-tower cable-stayed bridge in the world, crossing the Ob River in Siberia.
- Sutong Bridge spans the Yangtze River Delta in eastern China. It will surpass Japan's Tatara Bridge for the world's longest cable-stay main span when it opens in 2008, but its overall length will be shorter than the Sunshine Skyway Bridge in the United States.
- Tatara Bridge has the largest span of any cable-stayed bridge at 890 metres (2,920 ft), part of a series of bridges connecting Honshu and Shikoku in Japan.
- Ting Kau Bridge is the world's first major four-span (three towers) cable-stayed bridge, forming part of the road network connecting Hong Kong International Airport to other parts of Hong Kong, China.
- Vasco da Gama Bridge in Lisbon, Portugal is the longest bridge in Europe, with a total length of 17.2 km (10.7 mi), including 0.829 km (0.5 mi) for the main bridge, 11.5 km (7.1 mi) in viaducts, and 4.8 km (3.0 mi) in extension roads.
- Vidyasagar Setu (2nd Hooghly Bridge) in Kolkata, West Bengal, India is the longest cable-stayed bridge in the Indian subcontinent, with the main span measuring 457.2 m (1,500 ft) and total length being 823 m (2,700 ft).
- Zakim Bunker Hill Bridge is the world's widest cable-stayed bridge; carries 10 lanes of Interstate 93 over the Charles River in Boston, Massachusetts. It is also the first cable-stayed bridge with an asymmetrical deck design.
- Zhivopisny Bridge in Moscow, Russia, is the highest cable-stayed bridge in Europe.
- Zarate-Brazo Largo Bridges' over the Paranà Guazù and Paranà de las Palmas Rivers in Argentina (1977). They are the two first road and railway long span cable-stayed steel bridges in the world. Spans: 110 m + 330m + 110 m.
Gallery
Further reading
- De Miranda F., et al., (1979), "Basic problems in long span cable stayed bridges", Rep. n. 25, Dipartimento di Strutture - Università di Calabria - Arcavacata (CS) Italy, (242 pagg.) September 1979.
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