Bridge Paragraph

Bridges, structures engineered for crossing mountain ranges, freeways, ocean bays, and rivers are much more complex than one might think. Did you know that there are four main types of bridges, and each one serves a completely different purpose?

{Pont de Gard, an arch bridge}

Let’s start with the arch bridge. This bridge goes far back into history, to the time of the Roman Empire, where they were built using only stone. Perhaps the most famous is the Pont du Gard, which is as old as the entire Christian religion. Because of this 2,000 year old history, we might guess that it is still around today for a reason. Its natural strength is amazing. Designed to span across canyon gorges or valleys, it can typically only span from 200 to 800 feet. This would be classified as a short-spanning bridge. The weight from the travelers on the bridge carries all along the arch to the ends, where the weight is split between two abutments, which are the end points of the arch.

There can be some weaknesses to this bridge. The arch design can be time consuming to build. The basic structure of the arch bridge hasn’t changed dramatically over time, only the outside design and materials, which proves how successful it is.

{Train traveling on a beam bridge}

The beam bridge, the most practical, dependable, and popular of the bridges, is considered a small bridge, spanning usually around 120 feet and is only good for a limited amount of distance. This fairly inexpensive bridge, in comparison to others, serves mainly as a highway overpass for trains and cars. If thought out perfectly, the beam bridge can span miles long, but only if there are enough beams to support it. The Lake Pontchartrain Causeway in Louisiana is almost 24 miles l...

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... cable-stayed bridges, the cables come up to support the towers, which then carry the load.

There are two main different ways of arranging the cables for the cable-stayed bridges: the radial pattern and the parallel pattern. For the radial pattern, all the cables meet up on the same place on the tower and at different positions on the road. For the parallel pattern, the cables are parallel to each other and all meet up at different heights and lengths.

{Parallel and Radial Cable Patterns}

The cable-stayed bridge is a medium-span bridge, running anywhere from 500 to 2,800 feet. They are quickly becoming the most popular modern bridge. There is only one main complaint for this bridge, and it is that they don’t run as far in length as the suspension. If they are as popular as the articles say they are, I am sure they will surpass the suspension length soon.