Suspension bridges have benefited our everyday lives since John A. Roebling perfected the suspension bridge design in 1845 and built the Allegheny Suspension Bridge in Pittsburgh, Pennsylvania (Placzek). These bridges are better than previous bridges in many ways. Suspension bridges can span greater distances and are much cheaper than other types of bridges, such as beam bridges, which are simply constructed of beams supporting the deck of the bridge, they cannot span as long as these suspension bridges, and are more costly due to …show more content…
The supporting cables, running between the two anchorages, are the recipients of the tension forces. The cables are stretched from the weight of the bridge and its traffic as they run from anchorage to anchorage. The anchorages are also under tension, but since they, like the towers are held firmly to the earth, the tension is placed into the earth. Almost all suspension bridges also have a truss system underneath the bridge deck to help stiffen the bridge and prevent swaying.
There are two types of suspension bridges. The more common "M" design where the cables are strung in a "M"- like fashion. The other, and the more rare design of the two, is the "A" design. In this design, two towers and four anchorages are not needed, like the "M" design, but the wires run up from the roadway to a single tower where they are secured. (Brain) Current suspension bridge designs have many types of wires and the type of wire used depend on the size of the bridge. Galvanized Bridge Wire is the basic wire. Galvanized Bridge Wire is twisted together to form Galvanized Bridge Strands. Galvanized Bridge Rope is formed by twisting Galvanized Bridge Strands. These different "strengths" of wire are used in making the actual cables of the bridges. There are five main types of cables