BRIDGING THE GAP Lisa-Jayne Heading

For this practical we will be researching, building and testing a range of designs of bridges. Bridges are a very important in modern society; we use them to go over rivers, valleys and get anywhere with more convenience. Bridges have been around since the simplest of bridges like a fallen log over a creek. It was only when the romans started building bridges from stone is when they became a part of civilized society.

The Arch Bridge

Arch bridges are one of the oldest types of bridges, have been around for thousands of years and have great natural strength. An arch bridge uses a curved, semi-circular structure for support. They are are one of the most stable bridges and one of the most used because they’re very attractive and grand however, the construction of an arch bridge can be fairly difficult since the structure is completely unstable until the two spans meet in the middle. They were originally built of stone or brick, as seen in the picture below of the ‘Pond De Gard’, but these days are built for reinforced concrete or steel and due to the introduction of these new materials arch bridges could be built over longer distances.

Brooklyn Bridge

Pond De Gard (south of France)

Example of a stone Arch Bridge built by the romans over two thousand years ago

The Beam Bridge

The beam bridge is one of the most commonly used bridges along with arch bridges and is most effective over short distances. They are very common due to the fact they’re cheap and easy to build and they are very strong over short distances as opposed to other types. However the drawbacks of this type of bridge are that they’re weak over long distances and are not as pleasing the eye as some other bridges such as Arch or Suspension. Beam bridges can be made out of basically any material.

The Cantilever Bridge

The Cantilever bridge is basically a variation of a beam bridge. The

roadway of the bridge is held in place by cantilevers, which are long pieces going out into the water, but which are only anchored at one end. The positives of a Cantilever Bridge is that its able to carry large amounts of weight and the span can be greater than that of a simple beam, because a beam can be added to the cantilever

arms. However the construction of this bridge can be challenging and expensive.

The Cable-Stayed Bridge

The cable-stayed bridge is a type of suspension bridge using its cables to keep it up. Even this bridge is very similar to the suspension bridge its a lot cheaper. Along with this there are a lot of other positives including the fact this bridge is aesthetically pleasing and very modern looking, strong temperatures don’t affect the cables in any way and the bridge has a low center of gravity which makes it less venerable to earthquakes. There are negatives though, which includes the constant maintenance needs of the cables and the bridge is easily affected by the wind.

A basic beam bridge

Longest Cantilever Bridge in the world in Quebec