Dome (architecture)

I. Introduction

Dome (architecture), a roof or vault, usually hemispherical in form. Until the 19th century, domes were constructed of masonry, of wood, or of combinations of the two, frequently reinforced with iron chains around the base to counteract the outward thrust of the structure. Since then, as industrial technology developed, domes have been constructed of cast iron, reinforced concrete, steel, aluminum, laminated wood, or plastic.

II. Origins

The dome seems to have developed as roofing for circular mud-brick huts in ancient Mesopotamia about 6000 years ago. In the 14th century BC the Mycenaean Greeks built tombs roofed with steep corbeled domes in the shape of pointed beehives (tholos tombs). Otherwise, the dome was not important in ancient Greek architecture.

The Romans developed the masonry dome in its purest form, culminating in the Pantheon, a temple built (AD 118-128) by the emperor Hadrian. Set on a massive circular drum 6 m (20 ft) thick that conceals eight interlocked masonry piers, the coffered dome rises 43 m (142 ft) to form a perfect hemisphere on the interior, with a large oculus (eye) in its center to admit light.

The use of domes was continued in the Early Christian period for relatively small circular structures such as mausoleums and baptisteries. A typical example is the Church of Santa Costanza (350?), Rome, originally the tomb of Constantia, daughter of the emperor Constantine the Great. Byzantine architects were far more inventive in their use of domes. In the Byzantine capital of Constantinople (present-day Istanbul), a succession of large domed churches reached its apogee in Hagia Sophia (Church of the Holy Wisdom), built (532-537) for the emperor Justinian I. Its shallow dome, 31 m (100 ft) wide and ringed with windows at its base, is supported on four pendentives (spherical triangles) backed by immense exterior piers and by a series of half-domes.

After the fall (1453) of Constantinople to the Seljuk Turks, Hagia Sophia was converted to a mosque and became the model for a number of vast domed mosques built throughout the Ottoman Empire in subsequent centuries. Even before that, however, there was a long tradition of Islamic domed buildings (palaces, mosques, tombs, and baths); the Dome of the Rock (691) in Jerusalem is one of the earliest examples. Set on a pillared arcade, its double dome is of timber construction. Perhaps the most famous Islamic structure is the Taj Mahal in Agra, India, built (1632-1648) by the Mughal ruler Shah Jahan as a mausoleum for his favorite wife. Its slightly bulbous white marble dome rises on a tall drum over a spacious equilateral building.

III. Renaissance, Baroque, and Neoclassical Domes

The first great Italian Renaissance dome was the majestic octagonal dome built (1420-1436) by the architect Filippo Brunelleschi for Florence Cathedral. The immense structure, 39 m (130 ft) in diameter and 91 m (300 ft) tall, is topped with a lantern 16 m (52 ft) high, and consists of an outer roof shielding an inner masonry shell. The 8 primary ribs and 16 secondary ribs form a tightly interlocked masonry cage. In Rome the rebuilding of Saint Peter's Basilica occupied several generations of Renaissance architects. A plan for a Greek-cross (equal-armed) church, with a monumental dome over the crossing, was finally begun (1546) under the supervision of Michelangelo. Its awesome multiribbed dome, 41.7 m (137 ft) in diameter, became the prototype for domes throughout the world.

The most notable baroque domes in northern Europe were built in Paris and London. Jules Hardouin-Mansart built (1676-1706) the resplendent Church of Saint Louis des Invalides in Paris. Its dome (28 m/92 ft wide) is set on two unusually tall drums pierced with large windows that flood the interior with light. Sir Christopher Wren's noble dome for Saint Paul's Cathedral (1675-1711), London, incorporates a shallow inner dome, a conical masonry shell supporting the high lantern, and an outer lead-sheathed dome of timber.

The 1792 competition for the design of the U.S. Capitol in Washington, D.C., was won by an amateur architect, Dr. William Thornton, whose scheme called for a central block topped with a hemispherical dome–like that of the Roman Pantheon–flanked by two legislative wings. After this structure was burned by the British in 1814, the architect Benjamin Latrobe planned its reconstruction, which was finally finished under Charles Bulfinch's direction in 1830. Thomas U. Walter was commissioned to enlarge it in 1850. Dominating the sprawling white marble building and the city's skyline is Walter's soaring cast-iron dome, 27.4 (92 ft) in diameter (completed in 1863), which has served as the model for many state capitol buildings. Another neoclassical example is the domed Rotunda created between 1817 and 1825 by statesman and architect Thomas Jefferson for the University of Virginia in Charlottesville.

IV. 20th-Century Domes

The technological developments of the 20th century have radically changed the concept and construction of the dome. Thus the geodesic dome, patented by the American inventor R. Buckminster Fuller in 1947, is composed of a lattice of interlocking tetrahedrons and octahedrons made of lightweight materials, leaving the interior free of structural supports. Its many uses are exemplified by the Climatron, the gigantic climate-controlled botanical garden completed in St. Louis, Missouri, in 1960. Demand for geodesic domes increased in the 1990s because of their energy efficiency. Steel-dome construction dates to the late 19th century but was spectacularly adapted to sports arena use in the Astrodome, completed in Houston, Texas, in 1965. Its plastic roof is 195 m (642 ft) wide at the bottom tension ring of the structure. Reinforced concrete is also used in modern dome construction, as in the Palazetto dello Sport created in Rome by the Italian architect-designer Pier Luigi Nervi for the 1960 Olympic Games; its precast units are united by poured-in-place concrete ribs.

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"Dome (architecture)," Microsoft® Encarta® Online Encyclopedia 2000

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