Posts Tagged ‘keystone’
This arch one of the stronger arches. The keystone bears the weight of the stones pressing down from above. This pressure in turn pushes on the stones or bricks next to the keystone on both sides. This pressure is relayed from stone to stone, down both sides of the arch until it reaches the bottom blocks and then is carried down the piers to their foundations and into the ground. If the arch is too long, or if the piers at the ends are too light, the outward thrust will push the sides out and the top will cave in. If the arch is too light at the top, or too heavy at the sides, the sideward thrust of the arch walls will push the top up, and the sides will cave in.
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An arch that is equal to half a circle. A semicircular arch without voissoirs. Keystones are sometimes used for decoration but has nothing to do with the structure of the arch.
A flat arch having voussoirs inclined to the same angle on each side of the center keystone.
The central wedge-shaped stone at the crown of an arch that locks all parts together.