dome

dome,

a roof circular or (rarely) elliptical in plan and usually hemispherical in form, placed over a circular, square, oblong, or polygonal space. Domes have been built with a wide variety of outlines and of various materials.

Early Domes

The earliest domes were probably roofed primitive huts and consisted of bent-over branches plastered with mud. Another primitive form, called a beehive dome, is constructed of concentric rings of corbeled stones and has a conical shape. Ancient examples have been found in the tombs of Mycenae and can also still be seen in the folk architecture of Sicily. Although there is evidence of widespread knowledge of the dome, its early use was apparently restricted to small structures built of mud brick.

Roman and Byzantine Domes

It was the Romans who first fully realized the architectural potentialities of the dome. The Roman development in dome construction culminated in the pantheon (2d cent. A.D.). The Romans, however, failed to discover a proper handling of the pendentive—the device essential to placing a dome over a square compartment—that was finally achieved by the Byzantine builders of Hagia Sophia at Constantinople (A.D. 532–37). The other solution to placing a dome over a square was the squinch, which in the form of stalactites was to receive superb expression in Islamic architecture. Under Byzantine influence the Muslims early adopted the use of the dome; one of their first important monuments is the Dome of the Rock in Jerusalem. They often used the so-called Persian or onion dome. The most celebrated example is the Taj Mahal (A.D. 1630) at Agra, India.

Renaissance Refinements

Both the influence of the Roman Pantheon and of the Byzantine pendentive came to bear on the designers of the Italian Renaissance, and the crossings of many churches of the period were covered by masonry domes on pendentives. Between pendentive and dome a circular drum usually was interposed, serving to give greater elevation and external importance as well as a space for the introduction of windows. By the addition of an outer shell, the exterior came to be independently designed for maximum effectiveness, and the placing of a lantern at the top of this outer shell provided an apex for the entire composition.

Modern Domes

The dome in modern architecture utilizes such materials of construction as reinforced and thin-shell concrete, glass and steel, and plastic. An innovative contemporary approach to the form is the geodesic dome. These are low-cost, geometrically determined hemispherical forms as promoted by architect Buckminster Fuller.

Outstanding Domes

Celebrated examples are Brunelleschi's octagonal ribbed dome for the Cathedral of Florence (1420–36); St. Peter's, Rome, designed by Michelangelo, with two masonry shells (completed 1590), internal diameter 137 ft (42 m); the church of the Invalides, Paris, by J. H. Mansart (1706), 90 ft (27 m); St. Paul's Cathedral, London, by Sir Christopher Wren (1675–1710), 112 ft (34 m); and the Panthéon, Paris, by J. G. Soufflot (1775–81), 69 ft (21 m). The last three domes are built with triple shells, the middle shells serving to support the crowning lanterns.

In the United States the dome of the Massachusetts state capitol, designed (1795) by Charles Bulfinch, established the dome as a distinctive feature for numerous later state capitols as well as for the national Capitol at Washington, D. C. The dome of the latter, however, is of cast iron instead of masonry. The design, by T. U. Walter, has an inner diameter of 90 ft (27 m) and possesses great external impressiveness.

Bibliography

See E. B. Smith, The Dome: A Study in the History of Ideas (1975).

dome

1. The insulated roof of an observatory, which protects the telescope and associated equipment from bad weather and from the heating effect of the Sun. The telescope has access to the sky through a shutter in the dome, which is closed when the telescope is not in use. A delicate motorized mechanism ensures that, where necessary, the telescope is kept pointing through the opening at the same object throughout prolonged observations as the dome turns to compensate for the Earth's axial rotation. Where the telescope has an equatorial mounting the dome is movable and hemispherical. Rotation of the dome on a circular track allows different areas of the sky to be brought into view. Built into the observatory's design and engineering is a complicated interaction between the dome's rotation and the movement of the telescope about its inclined axis. The dome must be much larger than the telescope so that it will be able to swing freely inside the structure.

For a telescope with an altazimuth mounting the rotation rates of dome and telescope are the same. The dome needs only to be slightly larger than the telescope, and can be square or oblong. The cost of the dome is thus greatly reduced.

2. A low hill with a gentle convex-upward profile, of probable volcanic origin, on a planetary or satellite surface. Lunar domes are confined to the maria and are generally less than 15 km in diameter.

Dome

A curved roof structure that spans an area on a circular base, producing an equal thrust in all directions. A cross section of the dome can be semicircular, pointed or segmented.

bell-shaped dome

A dome in which the cross section is shaped in the form of a bell.

double dome

An outer dome built over an inner dome, with a space between them; used to provide a supporting structure for the outer dome, or a different shape or architectural treatment to each one individually.

elliptical dome

A dome with a cross section in the shape of an arc of an ellipse; may have a circular or an elliptical base.

geodesic dome

Consisting of a multiplicity of similar straight linear elements, arranged in triangles or pentagons; the members in tension have a minimal cross section and make up a spherical surface usually in the shape of a dome.

hemispherical dome

A dome with a constant radius of curvature that comes vertically from its springing line; the horizontal component of the thrust is absorbed by a continuous ring or chain at the base of the dome.

imperial dome

A round roof in the shape of an onion with a flared skirt at the base; it is commonly found in Greek Orthodox churches; also known as an onion dome.

interdome

The space between the inner and outer shells of a dome.

lattice dome

A steel dome structure having members which follow the circles of latitude and two sets of diagonals replacing the lines of longitude and forming a series of isosceles triangles.

melon dome

A melon-like ribbed dome, either on the interior or on the exterior.

onion dome

In Russian Orthodox church architecture, a bulbous dome which terminates in a point and serves as a roof structure over a cupola or tower.

radial dome

A dome built with steel or timber trusses arranged in a radial manner and connected by polygonal rings at various heights.

saucerdome

A dome whose rise is much smaller than its radius.

semicircular dome

A dome in the shape of a half sphere.

semidome

A dome equivalent to one-quarter of a hollow sphere, covering a semicircular area, such as an apse.

Turkish dome

An onion-shaped dome with a pointed top and a cylinder base; named for its use in Byzantine architecture.

Dome

 

a covering of buildings and structures, serving as a roof over spaces, normally those with a circular, polygonal, or elliptical floor plan. The shape of the dome follows a curve that is convex to the exterior of the building. Stresses existing in a dome consist not only of the basic compression loads, which transmit the weight of the roof to the supports, but also of horizontal thrusts. To accommodate the horizontal forces, special tension structures are sometimes provided, such as support rings at the base of the dome. Such structures were first introduced in the 15th century.

It is possible that the first domes were parts of thatched huts made of pliable material (reeds, branches) and clay. In antiquity, domes were built of stone and fired brick. These domes were actually corbel vaults with horizontal circles of masonry that progressively diminished in diameter in such a way that no horizontal thrust was transmitted to the walls (buildings in the town of Eshnunna in Mesopotamia, dating back to the early third millennium B.C.; the Treasury of Atreus in Mycenae, 14th century B.C. [?]). Corbel vaults were widely used in the popular architecture of many countries, for example, the gvirgvini, the stepped roof of Georgian folk dwellings.

In ancient Rome the true dome attained great importance after the introduction of squinches and particularly after the invention of concrete. In centrally planned buildings, domes with large spans enhanced the role of the covered spaces within the architectural composition and imparted to them spaciousness and solemn grandeur. The power and firmness of religious beliefs often found expression in such architecture (for example, the imposing dome of the Pantheon in Rome).

In Byzantine architecture, pendentive domes and squinch domes were widely used. (Both had appeared earlier in the architecture of ancient Rome and of Iran during the age of the Sassa-nids.) Squinches and pendentives made it possible to erect a dome above a space with any type of floor plan (for example, Hagia Sophia in Constantinople). During the Middle Ages various types of domes were used in Europe and the Caucasus, predominantly in cruciform domed churches (for instance, Dzhvari Church near Mtskheta in Georgia; Ripsime Church in Echmiadzin in Armenia). In the feudal states of Middle Asia and the Middle East, buildings appeared with large central domes.

As the role of the dome became understood in terms of its effect not only on the interior but also on the exterior of the building, the outer contour of the dome changed in its relation to the inner contour. Later the false dome appeared—an external shell with an outline differing from that of the dome proper. Such a shell usually consisted of curvilinear roofing supported by wooden rafters; an early example is the dome of St. Mark’s Church in Venice (ninth to 11th centuries). Domes with outer shells, which usually crowned the vertical space of religious buildings and were calculated to be in harmony with their architectural or natural surroundings, were particularly popular in the architecture of medieval Russia and of Middle Asia (for example, the mosque of Bibi Khanum in Samarkand, 1399–1401, which has an inner and an outer dome).

During the Renaissance the treatment of the dome as a plastic shape in space and as a dominant feature of urban design became widespread in the architecture of Western Europe. An example is the dome of Santa Maria del Fiore in Florence (1420–36, architect F. Brunelleschi), where for the first time the two shells of the dome were connected by stiffening stone ribs and by wooden rings, thus forming a unified structure.

Beginning at the end of the 18th century, domes were used in secular buildings. In the second half of the 19th century, domes of stone and brick were replaced by domes constructed of glass and metal frames or of wood or reinforced concrete. Masonry domes were at a disadvantage because of their great weight and the large amount of labor required for their construction. In the 20th century, with the development of monolithic and precast reinforced concrete, thin-walled shell vaults, and metal structures, the diversity of domical shapes and structures increased drastically. New types that appeared included ribbed domes, rib-and-ring domes, domes with rippled inner surfaces, geodesic domes (designed by B. Fuller, with diameters up to 150 m), and prefabricated domes creating the impression of a monolithic whole (designed by P. L. Nervi). Other innovative types include domes built of polymeric materials and those with an inflated double shell.

REFERENCES

Kuznetsov, A. V. Svody i ikh dekor. Moscow, 1938.
Kuznetsov, A. V. Tektonika i konstruktsiia tsentricheskikh zdanii. Moscow, 1951.
Spravochnik proektirovshchika promyshlennykh, zhilykh i obshchestven-nykh zdanii i sooruzhenii: Rashchetno teoreticheskii. Moscow, 1960.
Dereviannye konstruktsii, 3rd ed. Edited by G. G. Karlsen. Moscow, 1961.
Zhelezobetonnye konstruktsii: Spetsial’nyi kurs. Edited by P. L. Pasternak. Moscow, 1961.
Gokhar’-Kharmandarian, I. G. Bol’sheproletnye kupol’nye zdaniia. Moscow, 1972.
Mukhanov, K. K. Metallicheskie konstruktsii. Moscow, 1963.
Smith, E. B. The Dome. New York, 1950.

V. F. MARKUZON

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Dome

 

(geology), mode of occurrence of rock. (1) Volcanic (or magmatic) dome, a mode of occurrence of igneous rock in the form of a bun-shaped body. It forms on the earth’s surface when very viscous acid lava is extruded from a volcanic vent. It often has a characteristic radial and concentric jointing.

(2) Granite-gneiss (or gneiss) dome, an uplift of layers of the earth’s crust; the central part of the uplift is composed of granite-gneisses and gneisses, sometimes cut by granites, occurring in relatively gently sloping beds. The periphery of the gneiss core is composed of crystalline schists of increasingly lower degrees of metamorphism, crushed into small folds that are often tilted toward the center of the dome. Granite-gneiss domes form as a result of the floating up of granite material during regional metamorphism and granitization or repeated heating of the ancient granite-gneiss base. These domes are found mainly in the shields of ancient platforms. They may be many dozens of kilometers in diameter.

(3) Tectonic dome, a more or less rounded uplift of layers of the earth’s crust, which slopes down in all directions from the center of the dome. They may be dozens of kilometers (and sometimes up to 100) in diameter. Tectonic domes are found on platforms for the most part.

(4) Salt dome, a rounded uplift of rock layers with a nucleus of rock salt or other kind of salt. It forms when, owing to its lower density and high plasticity as compared to other sedimentary rocks, salt rises and is intruded. These domes are common in areas of deep submersion of the crystalline crust in platform basins and in the foredeeps and intermontane areas of mountain belts. In the USSR they are found in the Caspian, Dnieper, Donets, Tadzhik, and other basins.

V. E. KHAIN

dome

[dōm]

(architecture)

A hemispherical roof.

(astronomy)

A shallow raised structure on the moon's surface with a smooth convex cross section and a diameter anywhere from a few kilometers up to about 80 kilometers (50 miles).

(crystallography)

An open crystal form consisting of two faces astride a symmetry plane.

(engineering)

The portion of a cylindrical container used in a filament-winding process that forms an integral end of the container.

(engineering acoustics)

An enclosure for a sonar transducer, projector, or hydrophone and associated equipment; designed to have minimum effect on sound waves traveling underwater.

(geology)

A circular or elliptical, almost symmetrical upfold or anticlinal type of structural deformation.

A large igneous intrusion whose surface is convex upward.

(ordnance)

The mound of water spray created in air when the shock wave from an underwater detonation of an atomic weapon reaches the surface.

dome

1. A curved roof structure spanning an area; often spherical in shape.

2. A square prefabricated pan form; used in two-way joist (waffle) concrete floor construction.

3. A vault substantially hemispherical in shape, but sometimes slightly pointed or bulbous; a ceiling of similar form. also see geodesic dome and saucer dome.

dome

1. a hemispherical roof or vault or a structure of similar form

2. Crystallog a crystal form in which two planes intersect along an edge parallel to a lateral axis

3. Geology

a. a structure in which rock layers slope away in all directions from a central point

b. another name for pericline