Corbel arch
A corbel arch (or corbeled / corbelled arch) is an arch-like construction method that uses the architectural technique of corbeling to span a space or void in a structure, such as an entranceway in a wall or as the span of a bridge. A corbel vault uses this technique to support the superstructure of a building's roof.
A corbel arch is constructed by offsetting successive courses of stone (or brick) at the springline of the walls so that they project towards the archway's center from each supporting side, until the courses meet at the apex of the archway (often, the last gap is bridged with a flat stone). For a corbeled vault covering the technique is extended in three dimensions along the lengths of two opposing walls.
Although an improvement in load-bearing efficiency over the post and lintel design, corbeled arches are not entirely self-supporting structures, and the corbeled arch is sometimes termed a "false arch" for this reason. Unlike "true" arches, not all of the structure's tensile stresses caused by the weight of the superstructure are transformed into compressive stresses. Corbel arches and vaults require significantly thickened walls and an abutment of other stone or fill to counteract the effects of gravity, which otherwise would tend to collapse each side of the archway inwards.
Use in historical cultures
Ireland
The Newgrange passage tomb has an intact corbel arch (vault) supporting the roof of the main chamber, dating from about 3000BC.
Ancient Egypt
Egyptian pyramids from around the time of Sneferu used corbel vaults in some of their chambers. These include the Bent Pyramid and the Red Pyramid.
Ancient Greece
The ruins of ancient Mycenae feature many corbel arches and vaults, the "Treasury of Atreus" being a prominent example. The Arkadiko Bridge is one of four Mycenean corbel arch bridges which are part of a former network of roads, designed to accommodate chariots, between Tiryns and Epidauros in the Peloponnese, in Greece. Dating to the Greek Bronze Age (13th century BC), it is one of the oldest arch bridges still in existence and use. The well-preserved hellenistic Eleutherna Bridge on Crete has an unusually large span of nearly 4 m.[1]
Maya civilization
Corbeled arches are a distinctive feature of certain pre-Columbian Mesoamerican constructions and historical/regional architectural styles, particularly in that of the Maya civilization. The prevalence of this spanning technique for entrances and vaults in Maya architecture is attested at a great many Maya archaeological sites, and is known from structures dating back to the Formative or Preclassic era. By the beginning of the Classic era (ca. 250 CE) corbeled vaults are a near-universal feature of building construction in the central Petén Basin region of the central Maya lowlands.[2]
India
Before the true arch was introduced by the Mughals, the arches in Indian buildings were trabeated or corbelled. In North India in the state of Orissa, "the later temples at Bhubaneswar were built on the principle of corbelled vaulting, which is seen first in the porch of the Mukteswar [a temple said to epitomize N. Indian architecture, circa 950 AD] and, technically speaking, no fundamental change occurred from this time onwards."[3] The tomb of Sultan Ghori is an example of a corbelled arch from 1231 AD, located in New Delhi, India.
Cambodia
All the temples in Angkor made use of the corbel arch, between the AD 9th and 12th centuries.
Gallery
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Stone corbelled arch forms the hallways in the Palace at Palenque.
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Brickwork corbelled arch at Ubud in Bali, Indonesia.
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Stone corbelled arches at Borobodur in Java, Indonesia. Note the "T"-shaped central stones.
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Stone corbelled gateway arch to walls of Angkor Thom in Cambodia
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A brick corbelled arch disintegrating slowly at My Son in Vietnam.
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Stone corbelled arch in the Konark temple, India.
See also
References
- Coe, Michael D. (1987). The Maya (4th edition (revised) ed.). London: Thames & Hudson. ISBN 0-500-27455-X.