Acorbel arch (orcorbeled / corbelled arch) is anarch-like construction method that uses thearchitectural technique ofcorbeling to span a space or void in a structure, such as an entranceway in a wall or as the span of a bridge. Acorbel vault uses this technique to support the superstructure of a building's roof.
A corbel arch is constructed by offsetting successive horizontal courses of stone (or brick) beginning at the springline of the walls (the point at which the walls break off from verticality to form an arc toward the apex at the archway's center) 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 thepost and lintel design, corbeled arches are not entirely self-supporting structures, and the corbeled arch is sometimes termed afalse arch for this reason. Different from "true" arches, "false" or corbelled arches are built of horizontally laid stones or bricks, not of wedge-shapedvoussoirs converging towards, and being held together by a centralkeystone. Unlike "true" arches, not all of the structure'stensile stresses caused by the weight of the superstructure are transformed intocompressive stresses.
Corbel arches andvaults require significantly thickened walls and anabutment of other stone or fill to counteract the effects ofgravity, which otherwise would tend to collapse each side of the archway inwards.[citation needed]
Some arches use a stepped style, keeping the block faces rectangular, while other form or select them to give the arch smooth edges, usually with a pointed shape.
Corbelling is a technique first applied by the ancient Egyptians andChaldeans.[1]
TheNewgrange passage tomb, built sometime between 3200 and 2500 BC during theNeolithic period, has an intact corbel arch (vault) supporting the roof of the main chamber.[citation needed]
The medieval buildings of the monastery atSkellig Michael are also constructed using this method.[citation needed]
During theFourth Dynasty reign ofPharaohSneferu (c. 2600 BC), theAncient Egyptianpyramids used corbel vaults in some of their chambers. Thesemonuments include theMeidum Pyramid (around 2600 BC), theBent Pyramid (c. 2600 BC) and its satellite pyramid, and theRed Pyramid (c. 2590 BC). TheGreat Pyramid of Giza (c. 2580–2560 BC) uses corbel arches at the Grand Gallery. The Egyptians discovered the principle of thetrue arch early on, but continued to use the corbel arch in many buildings, sometimes mixing the two in the same building. In particular they avoided the true arch in temples as long as these were constructed,[2] preferring rectangular openings with a straightlintel.
Corbel arches and vaults are found in various places around the ancient Mediterranean. In particular, corbelled burial vaults constructed below the floor are found inMiddle Bronze II-IIIEbla in Syria, and inTell el-Ajjul,Hazor,Megiddo andTa'anach inCanaan (today'sIsrael andPalestine).[3]Ugarit, an ancient port city in northernSyria, also has corbelled structures.[citation needed]
Nuraghe constructions in ancientSardinia, dating back to the 18th century BC, use similar corbel techniques.[citation needed] The use ofbeehive tombs on theIberian Peninsula and elsewhere around the Mediterranean, going back to 3000 BC,[dubious –discuss] is also similar.[citation needed]
TheHittites in ancientAnatolia were also building corbelled vaults. The earliest ones date to the 16th century BC.
Some similarities are found between the Hittite and Mycenaean construction techniques. Yet the Hittite corbelled vaults are earlier by about 300 years.[4]
Greece has a long list of surviving or archaeologically studied corbelled arches and vaults used for bridges and a multitude of other structures, dating from theMycenean andMinoan, the lateClassical, and theHellenistic periods.[5]
The ruins of ancientMycenae feature many corbel arches and vaults, theTreasury of Atreus, built around 1250 BC, being a prominent example. TheArkadiko Bridge is one of four Mycenean corbel arch bridges, which are part of a former network of roads, designed to accommodate chariots, betweenTiryns andEpidauros in thePeloponnese, inGreece. Dating to the GreekBronze Age (13th century BC), it is one of the oldest arch bridges still in existence and use.[citation needed]
The well-preserved HellenisticEleutherna Bridge onCrete has an unusually large span of nearly 4 metres.[6] A second nearby bridge, which had survived until the late 19th century, is tentatively dated to the late Classical period.[6]
Corbeled arches are a distinctive feature of certainpre-ColumbianMesoamerican constructions and historical/regionalarchitectural styles, particularly in that of theMaya civilization. The prevalence of this spanning technique for entrances and vaults inMaya architecture is attested at a great manyMaya archaeological sites, and is known from structures dating back to theFormative or Preclassic era. By the beginning of the Classic era (ca. 250CE) corbeled vaults are a near-universal feature of building construction in the centralPetén Basin region of the central Maya lowlands.[7]
Before the true arch was introduced inIndo-Islamic architecture, almost all the arches in Indian buildings were eithertrabeated or corbelled. In North India in the state ofOrissa, "the later temples atBhubaneswar were built on the principle of corbelled vaulting, which is seen first in the porch of the Mukteswar [a temple said to epitomize North Indian architecture, circa AD 950] and, technically speaking, no fundamental change occurred from this time onwards."[8]
The earliest large buildings of theDelhi Sultanate established in 1206 after a Muslim invasion used Indian workers used toHindu temple architecture, but the patrons were used toCentral Asian styles that used true arches heavily. Corbel arches, the largest of exceptional size, were used in the massive screens in front of theQuwwat-ul-Islam Mosque inDelhi, begun in 1193, and theAdhai Din Ka Jhonpra mosque,Ajmer,Rajasthan, c. 1229. These are examples ofIslamic architecture drawing on Persia and Central Asia, where builders were well used to the true arch, that stick with the corbelled arch that Indian builders were used to.[9]
It took almost a century from the start of theDelhi Sultanate in 1206 for the true arch to appear. By around 1300 true domes and arches withvoussoirs were being built; the ruinedTomb of Balban (d. 1287) in theQutb complex in Delhi may be the earliest survival.[10]
Thecandi or temples ofIndonesia which were constructed between 8th to 15th century, made use of corbel arch technique to create a span opening for gate or inner chamber of the temple. The notable example of corbel arch in Indonesian classic temple architecture are the arches ofBorobudur. The interlocking andesite stone blocks creating the corbel arch, are notable for their "T" formed lock on the center top of the corbel arch.
All the temples inAngkor made use of the corbel arch, between the AD 9th and 12th centuries.
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