Bridges

Bridges were designed to allow people or other items to pass over an area without making it difficult or disturbing that particular area. For example, a bridge over a river allows passage over it very easy, but does not disrupt the flow of the water.

The first bridges were made of wood and stones. Crossbeams were designed to help them stay in place and hold the weight. The Roman’s began building their bridges out of cement. Brick and mortar soon followed. The Inca’s made bridges out of rope and wood. Bridges took a giant step forward in the 1900’s with the Industrial Revolution. Bridges for equipment and trains were built out of wrought iron and steel to support the weight.

There are four main types of bridges. Beam bridges rest horizontal on 2 piers. The weight pushes down on the beams. This causes compression on the top beam and tension on the bottom beam. Such bridges are approximately 200 feet. This type of bridge is used for pedestrian crossings and highway overpasses. Cantilever bridges use beams that are only supported at one end. They are built from steel and able to withhold several tons. This type of bridge can span over 1,500 feet.

The pretties bridges are



called arch bridges. While they are nice to look at, they also serve their purpose. The weight on the bridge is transferred into horizontal openings in the bridge. These bridges were often built by the Romans. Many early arch bridges are still standing today. Suspension bridges combine steel, metal, and rope to create a very long, pretty bridge that can withstand constant use. The main contributor to the suspension of such bridges are steel cables. The most popular suspension bridge is the Golden Gate Bridge in California.

While bridges are built to carry people and other materials over them, some are designed for the appearance. They are built taller or longer than necessary to create a design people enjoy looking at.

Bridges are classified into 4 forces. Tension involves tightening. Compression involves releasing. Bending relates to flexibility. Shear is the physics involved. Regardless of the design of a bridge, the main reason for it is the same. Technology allows us to enjoy bridges that are made of various materials and have unique designs. However, the real important issue is that the bridge stands up to the elements and is able to handle the traffic coming its way.


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