A bridge is a structure or construction as a fixed or movable connection for traffic over an obstacle without obstructing passage under the connection. The obstacle may include a river, canal, gorge, valley, road, or railroad. The traffic in many cases is road traffic and rail traffic, but in a general sense can also be the passage of wildlife (ecoduct) or of a watercourse (aqueduct). A bridge may be designed to carry a railroad, roadway, canal (canal bridge), or waterway (aqueduct). A long bridge, when it crosses another road or railroad, is also called a viaduct. Bridges over a waterway sometimes have a movable part; when crossing with a road or railroad, they will make the bridge high enough or else construct a level crossing.
Bridges are generally constructed of reinforced concrete, masonry, steel (rather cast iron). For short and smaller bridges, other materials such as wood and bamboo may be used. A bridge essentially consists of two parts:
the superstructure, over which traffic and the like passes, and
the substructure, with piers and foundations, which transfers the forces of the bridge to the ground.
I walk, I stop, I look, I click... Read more…