Bridge Types - Pros and Cons: Four Types of Bridges

July 8,2015

Bridges Project

~ Pros and Cons: Four Types of Bridges

Beam (Girder) Bridges:

Beam bridges are bridges that are sturdy and simple in design. These bridges are useful in situations where a simple and cost efficient bridge is needed to cross a small to medium sized gap over a river or treacherous land. Beam bridges, also referred to as Girder bridges because they use large steel or wooden beams for support, use a truss to help dissipate the weight of the load placed on them. The truss makes it possible for these bridges to support a heavier load and to be built on larger scales.

Beam bridge, although cost efficient, are only efficient to a certain height and over a certain distance. The added requirement of a truss in order to construct a sturdy beam bridge also causes disfavor of these bridges, The larger the bridge becomes, the heavier the bridge becomes, and the larger the truss necessary to maintain the bridge’s structural integrity. After a certain point, the bridge is no longer able to support its own weight and is ineffective at carrying a load.

Arch Bridges:

Arch bridges were introduced to the public by early Roman architects. These bridges are very stable when constructed properly, and are pleasing to the eye, which is why we see the arch used in structures for aesthetic as well as functional purposes. The design of these bridges works in a way that allows the weight of the load on the bridge’s peak to be evenly dispersed across the bridge, and increases the bridge’s structural integrity and strength over time.

On another note, while these bridges are nice to look at, they are equally difficult to construct. Arch bridges must be built into a solid surface, and engineers must take into account how the ground supporting the bridges may erode over time. The size of these bridges is also limited, as wider and longer bridges generally are taller as well. Because construction is more difficult, arch bridges tend to take a long time to build.

Cantilever Bridges:

Cantilever bridges are the strongest and most sturdy of the four bridges mentioned in this document, so they are able to support heavier loads with ease. These bridges don't require too many supports, so they can be built over longer distances and remain rigid and sturdy. While being constructed, these bridges cause a minimal amount of disruption to traffic flow and general life processes, making them common in busy areas. The sturdy design of these bridges also makes them common in places that are especially treacherous or prone to flooding.

While cantilever bridges are strong, they are just as heavy.

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