Schematic illustration of an arch.
This diagram illustrates the structural support of an arch extended into a barrel vault. The dotted line extending downward from the keystone (1) shows the strength of the arch directing compressive stresses (represented by the downward-pointing arrows outside the arch) safely to the ground. Meanwhile, tensile stress (represented by the horizontal and diagonal-facing arrows) is contained by the surrounding wall.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"Arch illustration."
http://commons.wikimedia.org/wiki/File:Arch_illustration.svg
Wikimedia
GNU FDL.
