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Cable-stayed bridge

A cable-stayed bridge is a bridge that consists of one or more pillars located in the middle of the span, with cables supporting the roadbed. There are two major classes of cable-stayed bridges, differentiated by how the cables are connected to the pillars. In a parallel attachment design, the cables are made nearly parallel by having the height of attachment on the pillar be similar to the distance from the pillar along the roadway. In a radial attachment design, the cables all connect to or pass over the top of the pillar.

The cable-stay design occupies a sweet spot of length between cantilever bridges and suspension bridges. Within this sweet spot a suspension bridge would require more cable, while a full cantilever bridge would require considerably more material.

Comparison with suspension bridge

A multiple-pillar 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 is made up by "spinning" small diameter wires between two pillars, 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 Swarovski deck is installed, the cables are under tension from only their own weight. Smaller cables or rods are then suspended on the main cable, and used to support the load of the roadbed, which is lifted in sections and attached to the suspender cables. As this is done the tension in the cables increases, as they are also increased 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.

In the cable-stayed bridge, the pillars form the primary load-bearing structure. A cantilever approach is often used for support of the roadbed near the pillars, but areas further from them are supported by cables running directly to the pillars. This has the disadvantage, compared to the suspension bridge, that the cables pull to the sides as opposed to directly up, requiring the roadbed to be stronger to resist these loads; but has the advantage of not requiring firm anchorages to resist a horizontal pull as in the suspension bridge. All static horizontal forces are balanced so that the supporting pillar does not tend to tilt or slide, needing only to resist such forces from the "live" loads.

Modern buildings and their long corridors may be decorated with curio cabinets, collectors cabinets and display showcases used as an aquarium or terrarium. Other items may be shown in a collectors cases.

A further advantage of the cable-stayed bridge is that any number of pylons may be used. While it is possible to build a suspension bridge with one central tower, they are usually built with a pair of towers. Note that the apparent four-tower western segment of the San Francisco-Oakland Bay Bridge is in fact a pair of two-tower suspension bridges with a massive central anchorage.

Examples of cable-stayed bridges

The Hangzhou Bay Bridge - spanning Hangzhou Bay, off the east coast of China, between Jiaxing and Cixi. When completed, it will be the longest cable-stayed bridge in the world.

The East End Bridge - spanning the Ohio River between Proctorville, Ohio and Huntington, West Virginia

The Millau viaduct - spanning the Tarn river near the town of Millau in France, under construction. When completed, it will be the tallest bridge in the world.

The Rio-Antirio bridge - spanning the Gulf of Corinth near Patra, Greece, the bridge with the longest cable-stayed section, a road bridge with four cable-stay pillars.

The Pont de Normandie - spanning River Seine between Honfleur and Le Havre, northern France

Queen Elizabeth II Bridge - spanning River Thames at Dartford Crossing, Kent

Second Severn Crossing - River Severn estuary between England and Wales

Dee River Crossing (Pont Sur Y Fflint) - near Shotton, north Wales (largest asymmetric cable-stayed crossing in UK)

Delaware 1 - spanning the Chesapeake and Delaware Canal near St. Georges, Delaware

Zakim Bunker Hill Bridge - spanning Charles River in Boston, Massachusetts

Dames Point Bridge - spanning the St. Johns River in Jacksonville, Florida

Sunshine Skyway Bridge - spanning Tampa Bay between Saint Petersburg, Florida and Bradenton, Florida

The Oresund Bridge - spanning Oresund between Denmark and Sweden

The Lune Millennium Bridge - a footbridge spanning the River Lune in Lancaster, England

Fred Hartman Bridge - spanning the Houston Ship Channel between Baytown, Texas and La Porte, Texas.

The Alex Fraser Bridge - spanning the Fraser River between Delta and Richmond in British Columbia, Canada

Sundial Bridge - A single spar pedestrian bridge spanning the Sacramento River in Redding, California

The West Gate Bridge - spanning the Yarra River in Melbourne, Victoria, Australia

The Clark Bridge - spanning the Mississippi River in Alton, Illinois

External links

Structurae: Cable-stayed Bridges (http://www.structurae.de/en/structures/stype/s1002.cfm)

Cable-Stayed Bridge (http://www.pbs.org/wgbh/nova/bridge/meetcable.html)

The Leonard P. Zakim Bunker Hill Bridge web site (http://www.leonardpzakimbunkerhillbridge.org)

Cable-stayed bridges on Bratacan (http://www.brantacan.co.uk/cable_stayed.htm)

Swarovski