Suspension bridge types
Encyclopedia
A suspension bridge is any type of bridge
that makes significant use of tension rather than or in addition to compression. A suspension bridge usually has main cables (else ropes or chains), anchored at each end of the bridge. Any load applied to the bridge is transformed into a tension in these main cables. The earliest suspension bridges had the cables anchored in the ground at either end of the bridge, but some modern suspension bridges anchor the cables to the ends of the bridge itself. The earliest suspension bridges had no towers or piers, but these are present in the majority of larger suspension bridges. Although the earlier types of suspension bridges are suitable only for relatively short spans, all of the 14 longest bridges in the world are suspension bridges (see List of longest suspension bridge spans). Ignoring the possibility of pre-Columbian trans-oceanic contact
, there were two independent inventions of the suspension bridge, in Eurasia
(probably in China) and in Central and South America.
A pure suspension bridge is one without additional stay cables and in which the main cables are anchored in the ground. This includes most simple suspension bridges and suspended-deck suspension bridges, and excludes self-anchored suspension bridges.
of the viaduct has a cable support below the deck, with one end of the cable anchored at a pier and the other end tied into a conventional cable stay. The underspanned portion of the span is 172 metres (564.3 ft) long and has three vertical members.
The Akashi-Kaikyō Bridge, one of the longest suspension bridges in the world, is a suspended-deck suspension bridge with a stiff truss girder
deck. Its main span
is 1,991 meters long.
. In many cases, the main cables are constructed first, then the deck is added. This often involves the use of a pilot cable. For details of their construction methods, see the articles about each type of bridge.
Provided the cables are of sufficiently high quality, suspension bridges are suitable for the longest spans. However, their construction costs are high, so that usually they are economical only for spans in excess of 1000 feet. Shorter spans often are constructed for esthetic reasons. The economy of longer span suspension bridges is due to their relatively low weight, but because of the greater flexibility that comes with low weight these bridges are more suitable as road bridges than railroad bridges.
Bridge
A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle...
that makes significant use of tension rather than or in addition to compression. A suspension bridge usually has main cables (else ropes or chains), anchored at each end of the bridge. Any load applied to the bridge is transformed into a tension in these main cables. The earliest suspension bridges had the cables anchored in the ground at either end of the bridge, but some modern suspension bridges anchor the cables to the ends of the bridge itself. The earliest suspension bridges had no towers or piers, but these are present in the majority of larger suspension bridges. Although the earlier types of suspension bridges are suitable only for relatively short spans, all of the 14 longest bridges in the world are suspension bridges (see List of longest suspension bridge spans). Ignoring the possibility of pre-Columbian trans-oceanic contact
Pre-Columbian trans-oceanic contact
Theories of Pre-Columbian trans-oceanic contact are those theories that propose interaction between indigenous peoples of the Americas who settled the Americas before 10,000 BC, and peoples of other continents , which occurred before the arrival of Christopher Columbus in the Caribbean in 1492.Many...
, there were two independent inventions of the suspension bridge, in Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
(probably in China) and in Central and South America.
Types
Types of suspension bridge include the following:| Simple suspension bridge Simple suspension bridge A simple suspension bridge is an early type of bridge that is supported entirely from anchors at either end, and has no towers or piers. However, it may have saddles... : the earliest known type of suspension bridge, and usually a footbridge Footbridge A footbridge or pedestrian bridge is a bridge designed for pedestrians and in some cases cyclists, animal traffic and horse riders, rather than vehicular traffic. Footbridges complement the landscape and can be used decoratively to visually link two distinct areas or to signal a transaction... . The deck is flexible and lies on the main cables, which are anchored to the earth. |
 |
| Underspanned suspension bridge Underspanned suspension bridge An underspanned suspension bridge is a rare type of suspension bridge that was developed in the early 19th century. It differs from its ancestor, the simple suspension bridge, in that the deck is raised on posts above the main cables... : an early 19th century descendant of the simple suspension bridge. The deck is raised on posts above the main cables. |
 |
| Stressed ribbon bridge Stressed ribbon bridge A stressed ribbon bridge is a tension structure . The suspension cables are embedded in the deck which follows a catenary arc between supports. Unlike the simple span the ribbon is stressed in compression, which adds to the stiffness of the structure... : a modern descendant of the simple suspension bridge. The deck lies on the main cables, but is stiff, not flexible. |
 |
| Suspension bridge Suspension bridge A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century... : the most familiar type. Though technically all the types listed here are suspension bridges, when unqualified with adjectives the term commonly refers to a suspended-deck suspension bridge,. This type is suitable for use by heavy vehicles and light rail Light rail Light rail or light rail transit is a form of urban rail public transportation that generally has a lower capacity and lower speed than heavy rail and metro systems, but higher capacity and higher speed than traditional street-running tram systems... . The main cables are anchored to the earth. The deck is carried below the main cables by "suspenders" and usually is stiff. |
 |
| Self-anchored suspension bridge Self-anchored suspension bridge A self-anchored suspension bridge is a suspension bridge in which the main cables attach to the ends of the deck, rather than to the ground via large anchorages... : a modern descendant of the suspension bridge, combining elements of a cable-stayed bridge Cable-stayed bridge A cable-stayed bridge is a bridge that consists of one or more columns , with cables supporting the bridge deck.... . The main cables are anchored to the ends of the decks. |
 |
A pure suspension bridge is one without additional stay cables and in which the main cables are anchored in the ground. This includes most simple suspension bridges and suspended-deck suspension bridges, and excludes self-anchored suspension bridges.
Hybrid types
Some suspension bridges are of unusual hybrid types. Among these are suspension bridges that have an "intermediate deck". These bridges have a portion of deck that resembles an underspanned suspension bridge. Some of the earliest suspended-deck suspension bridges were of this type, and they continue to be constructed. Examples constructed in the 20th century include a viaduct over the river Oberargen near Wangen, Germany. A 258 metres (846.5 ft) spanSpan (architecture)
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...
of the viaduct has a cable support below the deck, with one end of the cable anchored at a pier and the other end tied into a conventional cable stay. The underspanned portion of the span is 172 metres (564.3 ft) long and has three vertical members.
The Akashi-Kaikyō Bridge, one of the longest suspension bridges in the world, is a suspended-deck suspension bridge with a stiff truss girder
Truss bridge
A truss bridge is a bridge composed of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges...
deck. Its main span
Span (architecture)
Span is the distance between two intermediate supports for a structure, e.g. a beam or a bridge.A span can be closed by a solid beam or of a rope...
is 1,991 meters long.
Construction
Unlike many other types of bridge, suspension bridges often can be built without use of falseworkFalsework
Falsework consists of temporary structures used in construction to support spanning or arched structures in order to hold the component in place until its construction is sufficiently advanced to support itself...
. In many cases, the main cables are constructed first, then the deck is added. This often involves the use of a pilot cable. For details of their construction methods, see the articles about each type of bridge.
Provided the cables are of sufficiently high quality, suspension bridges are suitable for the longest spans. However, their construction costs are high, so that usually they are economical only for spans in excess of 1000 feet. Shorter spans often are constructed for esthetic reasons. The economy of longer span suspension bridges is due to their relatively low weight, but because of the greater flexibility that comes with low weight these bridges are more suitable as road bridges than railroad bridges.
External links
- "Suspension bridge" Encyclopædia Britannica