Suspension bridges

Suspension bridges are, arguably, one of the most artistic of civil engineering endeavors. Their simple lines and pleasing symmetry belie their strength and their ability to span long distances. (The world's longest, measuring 3,911 meters, is the Akashi Kaikyo bridge in Japan). Suspension bridges have been around for centuries and more primitive ones use vines or ropes for cables.

But how does a suspension bridge work? Typically, there are anchors on the extreme ends of the bridges. These weighted anchors serve as counterweights and hold the ends of the cables. Moving in toward the center of the bridge are the towers. The cables pass over these towers and attach to the anchors on either end. These main cables give the suspension bridge their beautiful curved lines. Vertical hanger cables are attached to the main cables and actually hold up the span of the bridge.

Obviously, the cables must be extremely strong but also flexible; and care must be taken to avoid extreme sway or vibration in heavy winds.

Some of the more famous suspension bridges include the Golden Gate Bridge (San Francisco); the Brooklyn Bridge (New York); the Sydney Harbor Bridge (Australia); the Akashi Kaikyo Bridge (Japan); and the Tower Bridge (London).

References: matsuo bridge co.; thinkquest.org