Essay by PaperNerd ContributorJunior High, 8th grade August 2001

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The article "Why Bridges Stand Up" discusses three types of bridges, which are the suspension, arch, and beam bridge. Each is described by how they stand up, what they look like, and how the load is applied to each part of the bridge. Examples of each bridge are given, making it easier to understand how it was built and how it stands up.

Ropes or cords hold up a suspension bridge. It undergoes a lot of tension, but can be put under a great deal of force. In order to make a suspension bridge, two or four cables are hung between two towers. Numerous strands make up the cables, strengthening the weight the bridge can withhold. The cables are secured into the ground at each end of the bridge. Smaller cables are attached in order to hold up the road of the bridge. An example of a suspension bridge is the Golden Gate Bridge, which is four thousand two hundred feet long.

An arch bridge is almost shaped like an upside-down suspension bridge. This type of bridge is made from steel, stone, or concrete, so it will be very strong. An arch bridge is undergoing compression, meaning that it is being pushed on. The cars and trucks push down on the bridge even more, but the arches hold the weight.

Beam bridges are the most common bridge because they are the oldest. A beam bridge is basically a beam supporting the roadway, and usually also supported at each end. The beam bridge is simpler than the other two, and therefore shorter, due to the lack of support. Beam bridges are still efficient and have dated back to the ancient times when a human or animal crossed a stream on a log.