Types+of+Bridges

Types of Bridges There are three main types of bridges; the beam, the arch, and the suspension. All three types of bridges are unique in their own way and provide an easier way to get over difficult obstacles.



Beam Bridge

Beam bridges are the most simple of structural forms being supported by an abutment at each end of the bridge deck. Beam bridges are the most common bridge and are usually used to span over smaller distances. Beam bridges were first built of wood or stone to get over a small stream or river. Beam bridges now are normally constructed out of steel, reinforced concrete, or a combination of both. The concrete used in making the bridge can either be reinforced, prestressed, or post-tensioned.The longest beam bridge over water in the world is the Lake Pontchartrain Causeway which consists of two parallel bridges crossing Lake Pontchartrain in southern Louisiana. The longer of the two bridges is 23.83 miles long. There are many different types of beam bridges. One basic type of beam bridge is the cantilever. A cantilever bridge is a beam that is only supported at one end and that extends beyond it's support. The cantilever bridge is basically a beam bridge with other features attached. A draw bridge is also a type of beam bridge used to span a water source. Draw bridges can open or raise in the middle and can draw back two sides to allow tall ships to pass through. There is also a box girder bridge which is a bridge in which the main beams comprise girders in the shape of a hollow box.

Arch Bridge

An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and the loads into a horizontal thrust. Arch bridges are one of the oldest types of bridges and have been around for thousands of years. They were first built from stone or brick. Now they are built from steel or reinforced concrete. The longest arch bridge in the world is called the Chaotianmen Bridge which is a rail-road bridge over the Yangtze river located in Chongqing, China and has a main span of 552 meters and a total length of 1,741 meters. It is made out of steel. A very well known arch bridge is the Alcantara Bridge in Spain which was built in 103-106 AD. One type of arch bridge is a through arch bridge which is also known as a half-through arch bridge or a through-type arch bridge. The through arch bridge is made from materials such as steel or reinforced concrete. The base in the through arch bridge is below the deck, but the top rises above it, so the deck passes through the arch. One of the most famous through arch bridge is the Sydney Harbour Bridge in Sidney, Australia. The Sydney Harbour Bridge carries trains, motor vehicles, pedestrians and bicycles. There is also the roman arch which contains voussoirs, or bricks. The keystone is the center voussoir that supports the other bricks. The push of the cemented voussoirs push outward and downward in the arch.

Suspension Bridge

A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. This arrangement allows the deck to be level or to arc upward for additional clearance. The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. Suspension bridges in their simplest form were first made from rope or wood. Today, the cables on suspension bridges are made of thousands of individual steel wires bound tightly together. Light, and strong, suspension bridges can span distances from 2,000 to 7,000 feet. Suspension bridges also tend to be the most expensive bridges to make. The Akashi-Kaikyo Bridge, also known as the Pearl Bridge has the longest central span of any other suspension bridge. The Pearl Bridge is located in Kobe-Awaji, Japan. A very well known suspension bridge is the Golden Gate Bridge in San Francisco, California. The Golden Gate Bridge opened in 1937 and is 4,200 feet long. One type of suspension bridge is the cable-stayed bridge which is a bridge that consists of one or more columns, with cables supporting the bridge deck. There are two types of cable stayed bridges, the fan design and harp design. In a harp design, the cables are made nearly parallel. In a fan design, the cables all connect to or pass over the top of the tower. There is also a stressed ribbon bridge which is a tension structure that has suspension cables embedded into the deck which follow a catenary arc between supports. There is also a simple suspension bridge and an underspanned suspension bridge which are rarely used today. In a simple suspension bridge the deck is flexible and lies on the main cables, which are anchored to the earth. In the underspanned suspension bridge the deck is raised on posts above the main cables.



The picture to the left is the Lake Pontchartrain Causeway in Southern Louisiana, it is listed as the longest beam bridge over water in the world. The picture in the center is the Alcantara Bridge in Alcantara, Spain. The Alcantara bridge has a total length of 194 meters.The picture to the right is the Rainbow Bridge in Tokyo, Japan which crosses northern Tokyo Bay and has a total length of 798 meters.