Self-anchored suspension bridge
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 Three self-anchored suspension bridges in Pittsburgh |
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| Ancestor | Suspension bridge |
|---|---|
| Related | None |
| Descendant | None |
| Carries | Pedestrians, automobiles, trucks, light rail |
| Span range | Medium |
| Material | Steel rope, steel eyebar, concrete spar, post-tensioned concrete deck |
| Movable | No |
| Design effort | high |
| Falsework required | Sometimes |
A self-anchored suspension bridge is a suspension bridge in which the main cables attach to the ends of the road, rather than to the ground via large anchorages. The design is well-suited for construction atop elevated piers, or in areas of unstable soils where anchorages would be difficult to construct.
 Suspension bridge with the main cables attached to the ground (black squares) |
 Self-anchored suspension bridge; the main cables are attached to the end of the road deck |
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[edit] History
The self-anchored suspension bridge form originated in the mid-19th century, with a published description by Austrian engineer Josef Langer in 1859 and U.S. Patent No. 71,955 by American engineer Charles Bender in 1867. The form was applied to a handful of Rhine River crossings in Germany during the first half of the twentieth century.[1]
[edit] Examples
The Three Sisters Bridges of Pittsburgh are the earliest examples (1924-28) of this bridge type in the US. Currently the largest self-anchored suspension bridges are the Konohana Bridge in Japan and the Yeoungjong Grand arcitecture Bridge in South Korea. Both of these bridges have a central span of 300 meters. The eastern span replacement of the San Francisco – Oakland Bay Bridge (currently under construction) will be larger when completed.
[edit] Construction method
Because the primary cables cannot be anchored until the bridge deck is completed, a self-anchored suspension bridge requires some falsework during construction. This falsework may take the form of compression struts (pictured here [1] and in the above diagram) which hold up the main cables (or the parts of them which have already been constructed), allowing the ends of the span to be constructed first in the fashion of a cantilever bridge, or it may be in the form of underdeck falsework.
[edit] Cable anchors
As in a traditional suspension bridge, the primary cable type may be multiple parallel independent cables as in the image at right of the Hutsonville Bridge, or eyebars, or a more conventional composite cable.
[edit] See also
- Eastern span replacement of the San Francisco–Oakland Bay Bridge - a single tower, asymmetrical bridge under construction
[edit] References
- ^ John A. Ochsendorf and David P. Billington, "Self-Anchored Suspension Bridges," ASCE Journal of Bridge Engineering, vol. 4, No. 3 (August 1999): 151-156.
[edit] External links
- Yeonglong Grand Bridge A two tower, three span self-anchored bridge
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![[1]](http://pghbridges.com/pittsburghW/0584-4477/7th1927clpgh1.jpg){kind=link}