Building Model Bridges Following the Engineering Process
Joe Lewis
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Introduction to the Different Types of Bridges
Even though bridges have different styles and designs, they all are constructed to support their own weight (dead weight) and the weight of the traffic that must go across them. Bridge designers or civil engineers must also consider other factors such as the weather, strong winds and earthquakes when designing bridges. There are several elements that all bridges have in common. All bridges consist of piers that hold up the center of the bridge and abutments that support the end of the bridge. The distance between the two supports is identified as the span. Each support is a foundation that transfers forces into the substrata of the earth. Civil engineers decide which type of bridge to build based on the weight or load that the bridge must support, the distance the bridge has to span, and the forces of nature that the bridge will have to endure. According to which source that you read, there are three or four different types of bridges, the beam bridge, suspension bridge, arch bridge and the truss bridge. Some sources categorize the truss bridge as a type of beam bridge. For the purposes of this paper, we classify the truss bridge as a type of beam bridge. Therefore, the major difference between the three types of bridges is the distance that they can cover in a single span. For example, a beam bridge can span up to 200 feet, if trusses are added it can span as far as 1200 feet. The arch bridge can span up to 1800 feet, whereas a suspension bridge can span up to 7,000 feet. Each of the different types of bridges holds weight in different ways.
