Major Types of Bridges
Engineers across the globe use bridges as a means to get people "from here to there." Geography usually demands the use of bridges in most instances. For centuries, man has used the idea of the bridge to his advantage, always improving on and innovated the idea of the bridge.
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Types
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Altogether, there are six different kinds of bridge types used around the world: girder, truss, arch, cantilever, cable-stayed and suspension bridges. All types of bridges can have subtle variations on their designs, but they all serve the same general function.
Function
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Bridges are structures that are used to provide a means of passage over a given terrain or obstacle. Designs are dependant on function (whether that is getting cars, people or whatever from one place to another) and the physical properties of the terrain where the bridge is to be built. Certain terrains demand special considerations.
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Features
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Arch bridges are arch shaped, the curved structure has a high tolerance to bending. Girder bridges, the oldest and most basic, are horizontal and support weight on both of its ends. Truss bridges are made up of many small beams that support great amounts of weight when put together. Cantilever bridges support weight in its middle. Suspension bridges use cables hung from towers to support weight. Cable-stayed bridges are similar to suspension bridges but using shorter cables, coming down diagonally, attached to shorter towers.
Forces
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All bridges mentioned have to overcome two basic obstacles: compression and tension. When compression reaches a critical level, buckling occurs. When tension reaches critical levels, snapping occurs. To overcome these forces, bridges have to either transfer or dissipate them. Spreading force over a large area "dissipates" it. Moving force from a weak area to a strong one "transfers" it.
Examples
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An example of a girder bridge is the Poplar Street Bridge. However, any fallen log spanning across a creek can be considered a girder bridge. The Old Chain of Rocks Bridge is an example of a truss bridge. The Eads Bridge is an example of an arch bridge. (These three bridges are in or around St. Louis, Missouri.) The Greater New Orleans Bridge is an example of a cantilever bridge. The Clark Bridge, which crosses the Mississippi River, is a cable-stayed bridge. One of the most famous bridges in the world, the Golden Gate Bridge is an example of a suspension bridge.
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