Friday, 15 April 2016

Bridges  


Bridges are very strong and are made to create a path over any obstacle. There are lots of different styles of bridges made for different reasons.The materials they use are very interesting and they are often well designed.The history of bridges dates back thousands of years with some very old bridges still standing today.

Types
There are lots of different types of bridges designed carefully for all sort of purposes. The truss bridges are designed for heavy weights and therefore are often used for trains. The beam bridge is normally used for cars to go over and is used for cars or boats to travel under. The arch and cantilever bridges are used to travel over long lengths of water. The suspension and cable stay are very similar bridges and are both used for long spans of land or water.

Material and Planning
Traditionally bridges were built with timber, rope and stone. More recently they use iron, steel and concrete. Bridges take a lot of theses materials and therefore company's value this. A lot of planning goes into bridges involving lots of different engineers testing dirt and material even before the bridge-building begins. The original designer needs a lot of second Apennines. It may take up to seven months to put the final plan on paper and then another   months up to a year until building even starts. A bridge can take up to __ years to build from start to finish.
History
Bridges have been used for over 3000 years. The first bridges were as simple as fallen trees creating a path over a river or stone pushed up to create a dam-like bridge. Later in time, concrete was introduced to the building world. Now most bridges are made with concrete and iron. The first iron bridge was made in 1779 and was over 100 feet long and used 378 tonnes of metal.

Bridges are used all over world. Their strength is incredible and some are very fantastic pieces of art and are big tourist attractions. Bridges are very important in this world making travel a lot easier.


Bibliography  

World History, viewed on 31 March 2016,   http://www.historyworld.net/wrldhis/PlainTextHistories.asp?historyid=ab97
Bridge structure http://autocww2.colorado.edu/~toldy4/E64ContentFiles/Construction/Bridge.ml  veiwed 31.3.16 and 6.4.16

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