A suspension bridge is a bridge that consists of two pairs of pillars, one on either end of the span, with two or more cables slung between them. The bridge deck is suspended from vertical cables or rods attached to the main cables. The main cables continue beyond the pillars, and are anchored in the ground. The bridge also has two smaller spans, running between either pair of pillars and the land. The design was developed in the 19th century (the first Hammersmith Bridge (1827) in west London was an early example), and has become widely used since.

The slender lines of the Severn Bridge, near Bristol, England (best seen on this ).
For another Severn Bridge picture, click here.

The main forcess in a suspension bridge are the tension in the main cables and the compression in the pillars. Since almost all the force on the pillars is vertically downwards, they can be made quite slender.

Two main reasons for building a suspension bridge, instead of, for instance, a cheaper low bridge, are:

The center span may be made very long, allowing the bridge to span a very wide, deep rift, and
It can be built high over water to allow the passage of very tall ships.

The largest suspension bridges in the world

(by length of centre span)

Akashi-Kaikyo Bridge (Japan) 1,990 meters or 6,529 feet - 1998
Great Belt Bridge (Denmark) 1,624 meters or 5,328 feet - 1998
Humber Bridge (England) 1,410 meters or 4,624 feet - 1981
Jangyn Bridge (China, Yangtse River) 1,385 meters - 1997
Tsing Ma Bridge (Hong Kong) 1,377 meters - 1997
Verrazano Narrows Bridge (USA) 1,298 meters or 4,260 feet - 1964
Golden Gate Bridge (USA) 1,280 meters or 4,200 feet - 1937
Hoga Kusten (Sweden) - 1,210 meters - 1997
Mackinac Bridge (USA) 1,158 meters or 3,800 feet - 1958
Minami Bisan-Seto Bridge (Japan) 1,118 meters or 3,668 feet - 1988
Second Bosporus Bridge (Turkey) 1,090 meters or 3,576 feet - 1988
First Bosporus Bridge (Turkey) 1,074 meters or 3,524 feet - 1973
George Washington Bridge (USA) 1,067 meters or 3,500 feet - 1931
Third Kurushima-Kaikyo Bridge (Japan) 1,030 meters - 1999
Second Kurushima-Kaikyo Bridge (Japan) 1,020 meters - 1999

A bridge with a center span of 3,290 m or 10,800 feet is proposed to connect Italy and Sicily but construction has not yet begun. Another has been proposed for the Strait of Gibraltar.

Other famous suspension bridges

Wheeling Suspension Bridge (USA, 1849)
Menai Suspension Bridge (north Wales, 1826)
Conwy Suspension Bridge (north Wales, 1826)
Clifton Suspension Bridge (England, 1864)
Brooklyn Bridge (USA, 1883)
Forth Road Bridge (Scotland, 1964)
Tacoma Narrows Bridge, (USA, 1940). The Tacoma Narrows are prone to sustained and moderately strong winds, with which the bridge had a tendency to resonate, leading to its collapse only months after completion.