- Materials & Industrial Technology
Cable-Stayed Bridge Designs
John Audubon Bridge (Parallel) Crosses the Mississippi
Bridges are a significant part of the history of mankind’s development. The early hunters and gatherers used fallen trees to cross streams. Later man learned to pile rocks to form pillars for simple bridges, but bridges came into their own with the discovery and perfection of the Roman arch. In the late 1700’s the science of bridge-building took another giant leap when the first iron bridge was constructed. Today the most popular types of bridges are; beam, cantilever, suspension, arch and cable-stayed.
Worlds First Iron Bridge, in Shropshire, U.K.
Cable-Stayed and Suspension Cable Bridges
To the untrained eye, cable-stayed bridges and suspension bridges appear to be the same. From a technical and design viewpoint they are quite different. The support cables for a cable-stayed bridge are connected to the support tower or pylon whereas in a suspension bridge, such as the Golden Gate Bridge, the support cables are connected to the suspension cable.
There are several distinct advantages of cable - stayed bridges such as: They provide greater rigidity than suspension bridges, which in turn reduces platform deformations of the deck with variable load factors. Cable-stayed bridges are built by cantilevering out from the support tower. This way the cables support to the bridge deck during construction and provide both temporary and permanent utilization. For symmetrical bridges the forces on each side of the support are balanced which reduces the ground anchorages requirements. This cantilever characteristic allows a cable-stayed bridge to be constructed from the inside out
Radial and Parallel Cabling
The cables can be attached to the deck of the bridge in a variety of ways. In the commonly used radial pattern, the cables extend from multiple attachment points on the deck to a single point at or near the top of the pylon. In a parallel pattern, cables are attached at different points along the pylon and run in parallel to the attachment points on the deck. The parallel pattern configuration has certain advantages one of which is the reduced length of support cables required. Both the radial pattern and the parallel pattern are easy to visually identify.
The Sunshine Skyway Bridge is the world's longest bridge with a cable-stayed main span. The bridge is a total of 29,040 feet in length, Note the parallel cabling .Construction of the bridge took almost 5 years.
The bridge below it is the Dames Point Bridge in Jacksonville, Florida, also known officially as the Napoleon Bonaparte Broward Bridge, This cable-stayed bridge crosses the St. Johns river and also utilizes parallel cabling.
The second photo below is Florida's Sunshine Skyway at sunrise. The photo was taken by MIchael Libbe, a very talented photographer from Orlando, Florida.
The Normandie bridge is located in France.
Jacksonville's Dames Point Bridge Utilizes Parallel Cabling
Florida's Sunshine Skyway Bridge Utilizes Parallel Cabling
Normandie Bridge in France Utilizes Radial Cabling
Viaducto Envigado Cble-Stayed Bridge Utilizing Radial Cabling
Parallel and Radial Compared
Cable-Stayed bridge construction has become the preferred technology for most bridge building throughout the world. While each individual bridge has its own unique characteristics cable-stayed designs with parallel cabling seems to be the most efficient and practical.