 A plate deck suspension bridge over the Chang Jiang ( Yangtze) river in ChinaA suspended-deck suspension bridge is a modern vehicle-carrying suspension bridges use towers to support the main load bearing cables. These cables must be securely anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. The roadway is supported by vertical suspender cables. This type of bridge is the only practical type usable for very long spans, where topography prohibits or it is hazardous to maritime traffic to add temporary or permanent central supports. This kind of bridge is particularly pleasing to the visual senses, with one beautiful example of the type being the Golden Gate Bridge at the entrance to San Francisco Bay. It is generally not suited for heavy rail applications as the bridge will flex under the concentrated load of a locomotive. Most suspension bridges have used light truss structures to support the roadbed (particularly owing to the unfavorable effects of using plate girders, discovered accidentally). Recent developments in bridge aerodynamics have allowed the re-introduction of plate structures. In the illustration to the right, note the very sharp entry edge and sloping undergirders in the suspension bridge shown. This enables this type of construction to be used without the danger of vortex shedding and consequent aeroelastic effects such as those that destroyed the Tacoma Narrows Bridge.
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