What is Bridge?
[[File:Ironbridge 6.jpg|thumb|[[The Iron Bridge]], 1781, was the first [[cast iron]] bridge]] [[File:Pont d'arcades de Móra d'Ebre (Ribera d'Ebre, Catalonia).jpg|thumb|Bridge crossing river d'Ebre, [[Catalonia]].]] [[File:Akashi-kaikyo bridge3.jpg|thumb|The longest suspension bridge in the world connects Honshu [[Shikoku|to Shikoku]], [[Japan]].]] {{otheruses}} A '''bridge''' is a [[structure]] to cross an open space or gap. Bridges are mostly made for crossing [[river]]s, [[valley]]s, or [[road]]s. Nowadays most big bridges are made to carry [[vehicle]]s 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.<ref>https://usatoday30.usatoday.com/news/nation/2010-11-22-bridges22_ST_N.htm</ref> == Types of bridges == There are five major structural types of bridges: * [[Beam bridge]]s<ref name=beambridge>{{cite web | url=http://www.design-technology.org/beambridges.htm | title=Beam bridges | publisher=Design Technology | accessdate=2008-05-14}}</ref> * [[cantilever bridge]]s, * [[arch bridge]]s<ref name=dubai>{{cite web | url=http://www.arabianbusiness.com/509621-worlds-longest-arch-bridge-for-dubai?ln=en | publisher=Arabian Business | accessdate=2008-05-14 | title=Dubai to build world's longest arch bridge | first=Amy | last=Glass}}</ref> * [[suspension bridge]]s and * [[cable-stayed bridge]]s<ref name=cable>{{cite web | url=http://www.newton.dep.anl.gov/askasci/eng99/eng99373.htm | title=Cable Stay vs Suspension Bridges | first=Andy | last=Johnson | publisher=U.S. Department of Energy}}</ref> == Note