The suspension bridge is a structure built to hold the roadway, railway or path, etc. across a road, valley or other obstacles. There are many types of bridge designs that every serve a specific cause subjecting to the exclusive situations. Consequently, for longer span purpose, suspension and cable-stayed bridges are very much appropriate.
Suspension bridges are sort of bridge that has cables (suspension cables) running among two pylons and from them a chain of vertical hangers (suspender cables) that hold the deck. In their best form suspension bridges had been more often than not crafted from timber and rope. But contemporary suspension bridges are made from a box section roadways carried by high tensile strength cables. The distinction between suspension bridges and the cable-stayed bridge is that in suspension bridge the cables supporting the deck are suspended vertically from main cables whereas, in cable-stayed, deck assisting cables are connected directly from towers.
Suspension bridges are most expensive to build, but this type is most appropriate for very long-span bridges. And represents more than 20 longest span bridges in the world. As these are long and flexible structures most exposed to dynamic loading. The vibration analysis becomes very significant in predicting the behavior of bridge under various dynamic loads such as wind load, vehicular load, and Earthquake load.
Suspension bridges can span distances from 2000ft to 7000ft longest than any other type of bridge. The world’s longest suspension bridges are Akashi-kaikyo Bridge in Japan, having the main span of 1991m. It has 6 lanes with a complete length of 3911m. And the smallest suspension bridge is Wiggly Bridge in York, England.
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Evolution of Suspension Bridges
Suspension Bridges are one of the earliest sorts formulated by man. The primary and basic form of this type is vine rope connecting two sides of the chasm which are still being utilized in some rural areas. These bridges may span about 200-300m. After that in 18th-century Chinese engineers started the construction of suspension bridge by connecting timber boards to the pair of suspended iron chains. In 1801, the first iron chain suspension bridge was made across Jacob’s Creek in Westmoreland County which is located in the U.S state of Pennsylvania. This is referred to as the earliest bridge to possess all the essential parts of the modern suspension bridge and was designed by James Finley who patented this system in 1808. So that this year is considered as a beginning era to the modern suspension bridges.
Even though Finley constructed some small bridges, the main significant bridge integrated with his technique was built over Menai straits in England by Thomas Telford. These suspension bridges have stone towers with a span of 177m which is still in use but, even though the iron chains were replaced with steel bar links after some years. After the failure of Tacoma Narrow Bridge due to a wind of just 65 Kmph, the study of wind behavior (aerodynamics) in the analysis of suspension bridge becomes very significant. Brooklyn Bridge was the former bridge built with cables consisting of several parallel strands of steel wire rather than the regular wrought chain. This type is strong enough to carry modern traffic.
World’s longest suspension bridges
| Sl.No | Bridge Name | Location | Year opened | Main Span(in meters) |
|---|---|---|---|---|
| 1 | Akashi Kaikyo Bridge | Japan | 1998 | 1,991 |
| 2 | Xihoumen Bridge | China | 2009 | 1,650 |
| 3 | Great Belt Bridge | Denmark | 1998 | 1,624 |
| 4 | Osman Gazi Bridge | Turkey | 2016 | 1,550 |
| 5 | Yi Sun-sin Bridge | South Korea | 2012 | 1,545 |
| 6 | Runyang Bridge | China | 2005 | 1,490 |
| 7 | Second Dongtinghu Bridge | China | 2018 | 1,480 |
| 8 | Nanjing Fourth Yangtze Bridge | China | 2012 | 1,418 |
| 9 | Humber Bridge | United Kingdom | 1981 | 1,410 |
| 10 | Yavuz Sultan Selim Bridge | Turkey | 2016 | 1,408 |
| 11 | Jiangyin Bridge | China | 1999 | 1,385 |
| 12 | Tsing Ma Bridge | China | 1997 | 1,377 |
| 13 | Hardanger Bridge | Norway | 2013 | 1,310 |
| 14 | Verrazzano-Narrows Bridge | United States | 1964 | 1,298 |
| 15 | Golden Gate Bridge | United States | 1937 | 1,280 |
Classification of Suspension bridges
The suspension bridge category is listed as below
- Simple Suspension Bridges
- Stressed Ribbon bridges
- Suspended Deck Suspension Bridge
- Self -anchored Suspension Bridge
- Under spanned Suspension Bridge.
Simple Suspension Bridges
It is a sort of bridge that has no tower or pier and is suspended on cables that are secured at their ends. These simple suspension bridges are the most established variation of suspension bridges. This is, for the most part, developed with rope and timber and is known as a rope bridge, Swing Bridge, hanging bridge and catenary bridge. The bridge deck is bent downwards and upwards and has extra ropes at upper dimensions fill in as handrail. It is utilized uniquely for the pedestrian way and can’t convey present day overwhelming streets and railways.
Stressed Ribbon Bridges
It is a modern and improved variation of the established basic suspension bridges. It has an inflexible deck slab that is suspended from cables which are thus inserted in the deck. To prevent the swaying and bouncing of this bridge, similar to simple suspension bridges, stiffness of bridge is improved by designing the deck section in arc shape between the supports which is stressed in traction. Typically this bridge is comprised of concrete reinforced by steel tensioned cables and can convey vehicle traffic. Read More
Suspended Deck Suspension bridge
This is considered as a modern designed suspension bridge. It has a road deck which is held up by cables which are suspended from the towers. This sort of bridge is appropriate for substantial vehicles and light rail. In the sixteenth-century structure of this kind of bridge is seemed first at the same time, worked after the eighteenth century. World’s most of the longest suspension bridges designed are of this type only.
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Self-anchored Suspension Bridge
It is another sort of bridge wherein the suspension cables (main cables) join to the ends of the deck, instead of the ground through huge anchorages. This structure is appropriate in zones of unstable soils where construction of anchorages would be troublesome and furthermore for the construction of atop elevated piers. In this framework balancing of forces is done internally without the requirement of any external anchorages making it reasonable for sites where there is trouble to anchor the large horizontal forces.
Under Spanned Suspension bridges
An under spanned suspension bridges is one that has its main cables running underneath the deck slab and these cables are secured at their ends. This is a rare sort of bridge that was created in the mid-nineteenth century. This suspension bridge is practical however unfit to convey a huge measure of weight since this kind of configuration makes the road deck unsteady.
This article covers definition, evolution, list of longest suspension bridges, and classification of suspension bridges. We hope this article was informative.
