BRIDGES

WHAT IS A BRIDGE?
A bridge is a structure built to span a gorge, valley, road, railroad track, river, body of water, or any other physical obstacle.

TYPES OF BRIDGES
There are four main types of bridges: beam bridges, cantilever bridges, arch bridges ,etc.

By use
A bridge is usually designed for trains, pedestrian or road traffic, a pipeline or waterway for water transport or barge traffic. In some cases there may be restrictions in use. For example, it may be a bridge carrying a highway and forbidden for pedestrians and bicycles, or a pedestrian bridge, possibly also for bicycles.

An aqueduct is a bridge that carries water, resembling a viaduct.

Decorative and ceremonial bridges

To create a beautiful image, some bridges are built much taller than necessary. This type, often found in east-asian style gardens, is called a Moon bridge, evoking a rising full moon.

Other garden bridges may cross only a dry bed of stream washed pebbles, intended only to convey an impression of a stream.

Often in palaces a bridge will be built over an artificial waterway as symbolic of a passage to an important place or state of mind. A set of five bridges cross a sinuous waterway in an important courtyard of the Forbidden City in Beijing, China. The central bridge was reserved exclusively for the use of the Emperor, Empress, and their attendants.

TECHNOLOGY INVOLVED IN BUILDING BRIDGES
New bridges are built either to replace old structures that no longer meet the demands of modern traffic or to cross obstacles on a new transportation route. Old bridges are replaced when repairs cannot be made economically or when traffic becomes too heavy for the old bridge. New transportation routes are built when traffic levels have outgrown the capacity of existing routes or simply to make it faster to get from one busy place to another. Often, new transportation routes are part of government programs to promote regional economic development.

In the United States, state and local transportation agencies determine where new bridges are needed and pay a small portion of the cost. The federal government usually pays for most of the construction expense, using money generated from taxes. Bridges funded by tax dollars are used free of charge. The few bridges for which a toll is charged to drivers for use are funded through the sale of bonds to raise money for construction. The money collected from the toll is used to pay back the bonds. The use of tolls and borrowing to finance bridge construction was more widespread in the past than it is today.

MARACAIBO'S LAKE BRIDGE

One of the longest bridges in the world (8km), built in 1962 over Lake Maracaibo, connected by a 55km strait to the Gulf of Venezuela. Developed since 1918 by foreign concerns keen to capitalize on the riches of oil production. A-frame pylons support a single cable at each side.

Name:
Lake Maracaibo Bridge,

General Rafael Urdaneta Bridge
Built:

1958 - 1962
Status:

in use
Location:

Maracaibo, Zulia, Venezuela
Crosses:

Lake Maracaibo

Designer:

Riccardo Morandi

Structural Type:
Cable-stayed bridge
Function / usage:
Motorway bridge / freeway bridge


Chronology
1957
International competition
24 August 1962
Opening
April 1964