Geometry In Bridge Design A Photo Essay by Justin Neil Certain materials are included under the fair use exemption of the U.S. Copyright Law and have been prepared according to the multimedia fair use guidelines and are restricted from further use.

Types of Bridges Reference: Telford, J. (n.d.) Bridge Types. Post Dispatch. Retrieved from http://scienceprep.org/bridges.htm

Beam Bridge Beam bridges are built using large rectangular beams (usually steel or steel-reinforced concrete) Because of the simplicity of the shape, beam bridges are subject to compression, tension and torsion forces, making un-reinforced concrete an unsuitable material The amount of material required make beam bridges impractical for long spans Beam bridge over the Colorado River Reference: Beam, G. L. (1934) New Bridge, Eagle County Colorado. Retrieved from http://cdm15330.contentdm.oclc.org/cdm/ref/collection/p15330coll22/id/28503

Truss Bridge Truss bridges use small members (usually steel) arranged in triangles to distribute weight evenly Truss construction eliminates most torsion forces, making the bridge stable over longer distances Karthaus Truss Bridge, Karthaus Pennsylvania Reference: Nicholas, T. (2010) Karthaus Truss Bridge . Retrieved from http://commons.wikimedia.org/wiki/File:Karthaus_Truss_Bridge_Steelwork.jpg

Arch Bridge Arch bridges use a quarter-circle arch design to redirect weight outward and downward, eliminating tension forces Arch bridges can be built from materials with poor tensile strength, such as concrete or stone The Romans constructed arch bridges using unmortared stone Modern arch bridges are usually made of steel The oldest standing arch bridge is the 1400-year-old Anji Bridge in Zhao County, China. Reference: Crazlei (2011) Anji Bridge 2011. Retrieved from http://commons.wikimedia.org/wiki/File:Arch_bridge_2011.jpg

Cantilever Bridge Cantilever bridges use multiple T-shaped, symmetrical sections to span long distances with minimal support Because each section is symmetrically balanced on a central girder, the weight of the structure is directed toward the middle Cantilever bridge at Niagara Falls Reference: Rand, McNally and Co. (1895) Cantilever Bridge at Niagara Falls. Retrieved from http://en.wikipedia.org/wiki/File:NU_RM30_Niagara_Cantilever_Bridge.jpg

Suspension Bridge Suspension bridges use steel cables to direct tension forces to load-bearing towers Catenary (inverted arch) design eliminates compression forces except directly under towers Suspension bridges are practical for areas without hard compressed footings, such as over bodies of water Golden Gate Bridge, San Francisco California Reference: Niewiroski, R. (n.d.) Golden Gate Bridge. Retrieved from http://teachers.egfi-k12.org/lesson-bridge-swe/