Bridge Types

There are 5 (main) different types of bridges:

1.     Arch Bridges:

2.     Beam Bridges

3.     Suspension Bridges

4.     Cantilever bridges

5.     Cable stay bridges

1.     Arch Bridges:

 They are call arch bridges because they have an arch in them. These bridges were originally built by bricks and stone. However now they are built of steel and reinforces concrete. This allows the bridges to be longer and lower. Unlike other bridges the key stone holds the bridge in place. This means that the weight of the bridge is transferred to the two ends of the bridge. The support at the end of the bridge that stop the ends from spreading out is called the abutments.

2.     Beam Bridges:

These types of bridges are known to man the most because they are so short and easy to build. They are also known as Girder bridges. They used to be as simple as a log across a stream but now there are many different types of Beam bridges. As the bridge is horizontal it is supported by piers to stop it from bending when there is a lot of weight on it or twisting.  

3.     Suspension Bridges:

These types of bridges are the longest bridges in the world. They were once made of wood and rope. However, steel is now used in place of the rope. Each cable is made up of thousands of steel wires each approximately 0.1 inch think. Steel is used as it is very strong and therefor be able to hold the weight of the bridges. Bridges that are light and strong can have a distance of up to 2,000 to 7,000 feet, ideal for covering waterways. Suspension bridges are often the most expensive types of bridges to build.

4.     Cantilever bridges:

Cantilever bridges are also long but they are mostly used for trains. Huge pillars that are held up by the narrow top members, take up the compression. Cross bracing prevents the bridge from twisting and bending. To maintain the balance of the bridge there are counterweights on either end of the bridge.

5.     Cable stay bridges:

Cable stay bridges and suspension bridges look similar. They both have cable which hang up a roadway and they both have towers. However they are different because of the way in which they support the load of the roadway. They are attached to the towers which form a triangle shape (which makes it strong) which holds the load. The cables are attached to the towers from different points on the bridge.

Bibliography:

*       http://www.design-technology.org/archbridges.htm

*       http://www.design-technology.org/beambridges.htm

*       http://www.design-technology.org/suspensionbridges.htm

*       http://www.design-technology.org/cantileverbridges.htm

*        http://www.pbs.org/wgbh/nova/lostempires/china/meetcable.html