The 1,104-meter-long main span of the Russky Island cable-stayed bridge will set a new length record when that Bosporus Strait crossing opens next year. Only two other cable-stayed-bridge main spans have surpassed the 1,000-m mark. But thanks to evolving technologies, materials and advanced methods of measuring external factors, all this could change, say bridge engineers.
For our first global edition of 2012, ENR has compiled a list of the top 10 longest bridges that use cable stays for structural support. Check out the slide show at left to see the list or continue reading below.
Traditionally, very long-span bridges tend to go the suspension route, because cable-stayed bridges are limited by the stiffness of their superstructure, says Joe Tse, manager of long-span bridges for Parsons Brinckerhoff, New York City.
“There is a point [at which] the current high-strength cables will exhibit some non-linear behavior. The weight creates a sag in the cable,” Tse says. “Once you get closer to 3,000 meters, typically you go for suspension bridges. But suspension bridges need fairly good ground conditions and fairly massive anchorages. In very poor soil conditions and with cost issues for concrete, then we might look at cable-stayed bridges.”
Advances in various materials may someday enable cable-stayed bridges to surpass 1,100-m-long main-span lengths. These materials include composites and lighter types of steel for the superstructure, says Craig Finley, founder of Finley Engineering Group, Tallahassee, Fla. Evolving software is improving measurements of wind impacts, which also will allow for longer cable-stayed spans, Finley adds.
Further, evolving concrete mixes are enabling longer-span bridges. “Cable forces are part of a closed force system permitting lighter elements as the compression forces are balanced within the deck,” says Jamey Barbas, global director of strategic projects for Hardesty and Hanover, New York City.
“The higher-strength concrete mixes allow designers to take full advantage of the compressive nature of the cable-stay system. Improved concrete mixes also yield benefits for composite designs by [using] steel-box superstructures for longer-span weight reduction.”
Construction methods and equipment also have advanced to meet design demands, Barbas says. “Climbing forms and larger cranes are enabling taller towers and longer spans to be constructed. The forms are reducing costs and provide for the more complex pylon shapes that are required to deal with the some of the large forces more effectively,” Barbas says.
Linda Figg, president and CEO of Figg Engineering Group, Tallahassee, points to the Penobscot Narrows Bridge as an example of new materials being tested: Three of its cables have fiber-reinforced polymer strands (ENR 7/10/06 p. 26).
- Longest Bridges;
- Cable Stay;
- Sutong Bridge;
- Stonecutters Bridge;
- Edong Bridge;
- Tatara Bridge;
- Pont De Normandie;
- Jingyue Bridge;
- Incheon Bridge;
- Shanghai Yangtze River Bridge;
- Minpu Bridge;
- Third Nanjing Yangtze River Bridge;
- Russky Island;
- Parsons Brinckerhoff;
- Finley Engineering Group;
- Figg Engineering Group;
- Veterans Glass City Skyway Bridge