(Also known as cable bridges)
The Beginning of Suspension Bridges
Suspension bridges in their simplest form were originally made from rope and wood. Modern suspension bridges use a box section roadway supported by high tensile strength cables. In the early nineteenth century, suspension bridges used iron chains for cables. The high tensile cables used in most modern suspension bridges were introduced in the late nineteenth century. Today, the cables are made of thousands of individual steel wires bound tightly together. Steel, which is very strong under tension, is an ideal material for cables; a single steel wire, only 0.1 inch thick, can support over half a ton without breaking.
The main forces in a suspension bridge of any type are tension in the cables and compression in the pillars. Since almost all the force on the pillars is vertically downwards and they are also stabilized by the main cables, the pillars can be made quite slender, as shown in the pictures above. In a suspended deck bridge(suspension bridge), cables suspended via towers hold up the road deck. The weight is transferred by the cables to the towers, which in turn transfers the weight to the ground. This is a type of bridge that is able to stretch to extreme lengths and be capable of lasting a very long time. It also, since it is suspended in the air, is able to withstand natural disasters such as earthquakes or tornadoes better than another type of bridge.