Railway Bridge-Nawalapitiya,Sri lanka

A bridge is a structure built to span physical obstacles without closing the way underneath such as a body of water, valley, or road, for the purpose of providing passage over the obstacle.

 Until the end of the 18th Century, bridges were made out of timber, stone and masonry. Modern bridges are currently built in concrete, steel, fiber reinforced polymers (FRP), stainless steel or combinations of those materials.

 Iron and Steel bridges are used today and most of the worlds major rivers are crossed by this type. The picture shows the first iron bridge in the world. It was built in Telford in 1779 by Abraham Darby (the third) and was the first large structure in history to be constructed from iron.

 In a common variant, the suspended span, the cantilever arms do not meet in the center; instead, they support a central truss bridge which rests on the ends of the cantilever arms. The suspended span may be built off-site and lifted into place, or constructed in place using special traveling suppor