Cable-Stayed Bridge Types

History

• The basic design of cable-stayed bridges was first recorded in the book "Machinae Novae" in 1595, according to NOVA Online. Despite the long history of the design, the use of cable-stayed bridges did not become common until the bombed-out bridges of Europe were rebuilt following World War II. The lack of available steel for construction in postwar Europe and the presence of foundations that were in place and usable led to the use of cable-stayed bridges due to economic and time restraints. Cable-stayed bridges become popular in the U.S. in the latter half of the 20th century, commonly for medium length bridge spans of between 500 and 2,800 feet, NOVA Online reports. Cable-stayed design is also used for large bridges, such as the Normandy Bridge in Northern France, which upon its completion in 1995 was the longest bridge in the world.

Types

• Two commonly used types of cable-stayed bridges are the parallel pattern and radial pattern styles. The design of a parallel pattern cable-stayed bridge requires the attachment of the cables from different points on the roadway to different points on the support towers so that the cables are parallel. A radial pattern cable-stayed bridge has cables attached to the support towers at a single point on the tower that fan out to attach to various points along the roadway of the bridge.

Support

• The various design differences among cable-stayed bridge designs include the types of struts and supports used in the construction of the bridge, the Federal Highway Administration reports. Support struts include locked coil struts, structural struts and parallel struts. In the U.S. parallel and locked coil struts are no longer used to construct bridges. Support bars are usually encased in piping, with polyethylene or steel sheathing used to stop corrosion of the support bars. Galvanized steel sheathing is recommended by the FHA despite few corrosion problems being found with polyethylene sheathing.

Advantages

• One advantage of cable-stayed bridges is the reduced time for construction because of the use of prefabricated sections fitted together over a short period of time. Wind damage is also less of a problem in cable-stayed bridges because the load of the bridge weight is positioned on the support towers. In comparison, suspension bridges allow the load to be placed on the attachments at either end of the cable, a less stable form of attachment than a cable-stayed design.