History

Bridge is a structure that provides passage over obstacles such as valleys, rough terrain or bodies of water by spanning those obstacles with natural or manmade materials. They were first used in ancient times when first modern civilizations started rising in the Mesopotamia. From that point on, knowledge, engineering, and manufacture of new bridge building materials spread beyond their borders, enabling slow but steady adoption of bridges all across the world.

In the beginning bridges were very simple structures that were built from easily accessible natural resources- wooden logs, stone and dirt. Because of that, they had ability only to span very close distances, and their structural integrity was not high because mortar was not yet invented and rain slowly but constantly dissolved dirt fillings of the bridge. Revolution in the bridge construction came in Ancient Rome whose engineers found that grinded out volcanic rocks can serve as an excellent material for making mortar. This invention enabled them to build much sturdier, powerful and larger structures than any civilization before them. Seeing the power of roads and connections to distant lands, Roman architects soon spread across the Europe, Africa and Asia, building bridges and roads of very high quality. (Source: http://www.historyofbridges.com/)

Types of Bridges

There are six main types of bridges:

1. Beam bridges,

2. Arch bridges,

3. Truss bridges.

4. Suspension bridges,

5. Cantilever bridges, and

6. Cable-stayed bridges

Beam Bridges: The most basic type of bridges that are supported by several beams of various shapes and sizes.

Arch Bridges: These bridges use an arch as a main structural component. The arch is always below the bridge deck. They are made with one or more hinges, depending of what kind of load and forces they must endure.

Truss Bridges: This type of bridge design uses a diagonal mesh of posts above the bridge. The two most common designs are the king posts (two diagonal posts supported by single vertical post in the center) and queen posts (two diagonal posts, two vertical pots and horizontal post that connect two vertical posts at the top).

Suspension Bridges: Bridges that use ropes or cables from the vertical suspender to hold the weight of bridge deck and traffic. A great example of a suspension bridge is the famous Golden Gate Bridge in San Francisco.

Cantilever Bridges: Similar in appearance to arch bridges, but they support their load not through vertical bracing but through diagonal bracing. They often use truss formation both below and above the bridge deck.

Cable-stayed Bridges: Bridge that uses deck cables that are directly connected to one or more vertical columns. Cables are usually connected to columns in two ways – harp design (each cable is attached to the different point of the column), and fan design (all cables connect to one point at the top of the column).