A bridge is a structure to cross an open space or gap. Bridges are mostly made for crossing rivers , valleys , or roads . Nowadays most big bridges are made to carry vehicles but people have also walked across bridges for thousands of years. Bridges called highway overpasses carry a road over another road.

Military bridges are portable , so that they may be easily moved to where they are needed. This makes them much more complex than most civilian bridges.

The first man-made bridges were probably made from cut wood or stones. Some stone bridges have lasted thousands of years. In recent centuries large bridges are made mostly of steel . They do not last as long. Many bridges are in a state of disrepair. ^[1]

Types of bridges [ change | change source ]

There are five major structural types of bridges:

• Beam bridges ^[2]
• cantilever bridges ,
• arch bridges ^[3]
• suspension bridges and
• cable-stayed bridges ^[4]

Notes [ change | change source ]

Media related to Bridges at Wikimedia Commons