1. Geometry In Bridge Design
A Photo Essay by Justin Neil
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2. Types of Bridges
Reference: Telford, J. (n.d.) Bridge Types. Post Dispatch. Retrieved from

3. 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

4. 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

5. 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 Retrieved from

6. 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

7. 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