The Arch Bridge

    The Romans pioneered the building of arch bridges, which with their familiar parabolic shape allowed for longer spans than beam bridges.  Because the reach of the beam bridge is limited, arch bridges provide a natural mechanism for spanning greater distances.  Gravity holds the elements of the bridge in place as they are pressed against each other by the downward force.  Stone was an apt material for arch bridges due to is compressive strength.  Two basic types of stone arches exist: the corbel arch, created by stones or bricks laid on top of each other in a kind of stairway formation, and the voussoir arch (the "true arch"), based on the parabolic placement of like-sized components.  Elizabeth Mock, in her book The Architecture of Bridges, writes that "it was in stone that the building of bridges became a conscious art . . . " Steel arch bridges do not employ the voussoirs.

    To see examples of stone arch bridges, including concrete ones, click on Stone Arch Bridges, and to see examples of steel and iron arch bridges, click on Steel Arch Bridges.   Each contains archives with more images.

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