Science Fair Project Encyclopedia
A dome is a common structural element of architecture that resembles the hollow upper half of a sphere. Domes do not have to be perfectly spherical in cross-section, however; it is sufficient that they simply be curved surfaces. A saucer dome is a dome section of large radius that caps a space with a low dome. A variant is the Onion dome that resembles more than half of a sphere, exemplified by Saint Basil's Cathedral in Moscow.
The concave triangular sections of vaulting that provides the transition between a dome and the square base on which it is set and transfer the weight of the dome are called pendentives. A less sophisticated version of a pendentive is a squinch..
A dome can be considered as an arch which has been rotated around its vertical axis. As such, domes have a great deal of structural strength. They can be constructed of ordinary masonry, held together by friction and compressive forces.
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