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A masonry arch
1. Keystone 2. Voussoir 3. Extrados 4. Impost 5. Intrados 6. Rise 7. Clear span 8. Abutment

An arch is a structure that spans a space while supporting weight (e.g. a doorway in a stone wall). Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.

The semicircular arch was followed in Europe by the pointed Gothic arch or ogive whose centreline more closely followed the forces of compression and which was therefore stronger. The semicircular arch can be flattened to make an elliptical arch as in the Ponte Santa Trinita. The parabolic and catenary arches are now known to be the theoretically strongest forms. Parabolic arches were introduced in construction by the Spanish architect Antoni Gaudí, who admired the structural system of Gothic style, but for the buttresses, which he termed “architectural crutches”. The catenary and parabolic arches carry all horizontal thrust to the foundation and so do not need additional elements.

The horseshoe arch is based on the semicircular arch, but its lower ends are extended further round the circle until they start to converge. The first examples known are carved into rock in India in the first century AD, while the first known built horseshoe arches are known from Aksum (modern day Ethiopia and Eritrea) from around the 3rd–4th century, around the same time as the earliest contemporary examples in Syria, suggesting either an Aksumite or Syrian origin for the type of arch.[1]

Contents

Construction

An arch requires all of its elements to hold it together, raising the question of how an arch is constructed. One answer is to build a frame (historically, of wood) which exactly follows the form of the underside of the arch. This is known as a centre or centring. The voussoirs are laid on it until the arch is complete and self-supporting. For an arch higher than head height, scaffolding would in any case be required by the builders, so the scaffolding can be combined with the arch support. Occasionally arches would fall down when the frame was removed if construction or planning had been incorrect. (The A85 bridge at Dalmally, Scotland suffered this fate on its first attempt, in the 1940s). The interior and lower line or curve of an arch is known as the intrados.

Old arches sometimes need reinforcement due to decay of the keystones, known as bald arch.

The gallery shows arch forms displayed in roughly the order in which they were developed.

Technical aspects

The arch is significant because, in theory at least, it provides a structure which eliminates tensile stresses in spanning an open space. All the forces are resolved into compressive stresses. This is useful because several of the available building materials such as stone, cast iron and concrete can strongly resist compression but are very weak when tension, shear or torsional stress is applied to them. By using the arch configuration, significant spans can be achieved. This is because all the compressive forces hold it together in a state of equilibrium. This even applies to frictionless surfaces. However, one downside is that an arch pushes outward at the base, and this needs to be restrained in some way, either with heavy sides and friction or angled cuts into bedrock or similar.

This same principle holds when the force acting on the arch is not vertical such as in spanning a doorway, but horizontal, such as in arched retaining walls or dams.

Even when using concrete, where the structure may be monolithic, the principle of the arch is used so as to benefit from the concrete's strength in resisting compressive stress. Where any other form of stress is raised, it has to be resisted by carefully placed reinforcement rods or fibres. (See Arch bridge.)

Other types

The Delicate Arch, a natural arch in Moab, Utah

A blind arch is an arch infilled with solid construction so it cannot function as a window, door, or passageway.

A dome is a 360 degree application of the arch, rotated about its vertical axis.

Natural rock formations may also be referred to as arches. These natural arches are formed by erosion rather than being carved or constructed by man. See Arches National Park for examples.

A special form of the arch is the triumphal arch, usually built to celebrate a victory in war. A famous example is the Arc de Triomphe in Paris, France.

A vault is an application of an arch extended along an axis perpendicular to the its plane; the groin vault is the intersection of two vaults.

Gallery

See also

References

  1. ^ Stuart Munro-Hay, Aksum: A Civilization of Late Antiquity. Edinburgh: University Press. 199
  • Rasch, Jürgen (1985), "Die Kuppel in der römischen Architektur. Entwicklung, Formgebung, Konstruktion", Architectura 15: 117–139 
  • Roth, Leland M (1993). Understanding Architecture: Its Elements History and Meaning. Oxford, UK: Westview Press. ISBN 0-06-430158-3.  pp. 27–8

External links


File:Arch
A masonry arch
1. Keystone 2. Voussoir 3. Extrados 4. Impost 5. Intrados 6. Rise 7. Clear span 8. Abutment

An arch is a structure that spans a space while supporting weight (e.g. a doorway in a stone wall). Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture and their systematic use started with the Ancient Romans who were the first to apply the technique to a wide range of structures.

The semicircular arch was followed in Europe by the pointed Gothic arch or ogive whose centreline more closely followed the forces of compression and which was therefore stronger. The semicircular arch can be flattened to make an elliptical arch as in the Ponte Santa Trinita. The parabolic and catenary arches are now known to be the theoretically strongest forms. Parabolic arches were introduced in construction by the Spanish architect Antoni Gaudí, who admired the structural system of Gothic style, but for the buttresses, which he termed “architectural crutches”. The catenary and parabolic arches carry all horizontal thrust to the foundation and so do not need additional elements.

The horseshoe arch is based on the semicircular arch, but its lower ends are extended further round the circle until they start to converge. The first known built horseshoe arches are known from Aksum (modern day Ethiopia and Eritrea) from around the 3rd–4th century, around the same time as the earliest contemporary examples in Roman Syria, suggesting either an Aksumite or Syrian origin for the type of arch.[1][page needed]

Contents

History

[[File:|thumb|Roman arch architecture in Ostia Antica, Italy]]

True arches, as opposed to corbel arches, were known by a number of civilizations in the Ancient Near East and the Levant, but their use was infrequent and mostly confined to underground structures such as drains where the problem of lateral thrust is greatly diminished.[2] A rare exception is the bronze age arched city gate of Ashkelon, Israel, dating to ca. 1850 BC.[3] An early example of a voussoir arch appears in the Greek Rhodes Footbridge.[4]

The ancient Romans learned the arch from the Greeks and Etruscans, refined it and were the first builders to tap its full potential for above ground buildings:

The Romans were the first builders in Europe, perhaps the first in the world, fully to appreciate the advantages of the arch, the vault and the dome.[5]
Throughout the Roman empire, their engineers erected arch structures such as bridges, aqueducts, and gates. They also introduced the triumphal arch as a military monument. Vaults began to be used for roofing large interior spaces such as halls and temples, a function which was also assumed by domed structures from the 1st century BC onwards.

The segmental arch was first built by the Romans who realized that an arch in a bridge did not have to be a semicircle,[6][7] such as in Alconétar Bridge or Ponte San Lorenzo. They were also routinely used in house construction as in Ostia Antica (see picture).

Construction

An arch requires all of its elements to hold it together, raising the question of how an arch is constructed. One answer is to build a frame (historically, of wood) which exactly follows the form of the underside of the arch. This is known as a centre or centring. The voussoirs are laid on it until the arch is complete and self-supporting. For an arch higher than head height, scaffolding would in any case be required by the builders, so the scaffolding can be combined with the arch support. Occasionally arches would fall down when the frame was removed if construction or planning had been incorrect. (The A85 bridge at Dalmally, Scotland suffered this fate on its first attempt, in the 1940s). The interior and lower line or curve of an arch is known as the intrados.

Old arches sometimes need reinforcement due to decay of the keystones, forming what is known as bald arch.

The gallery shows arch forms displayed in roughly the order in which they were developed.

Technical aspects

The arch is significant because, in theory at least, it provides a structure which eliminates tensile stresses in spanning an open space. All the forces are resolved into compressive stresses. This is useful because several of the available building materials such as stone, cast iron and concrete can strongly resist compression but are very weak when tension, shear or torsional stress is applied to them. By using the arch configuration, significant spans can be achieved. This is because all the compressive forces hold it together in a state of equilibrium. This even applies to frictionless surfaces. However, one downside is that an arch pushes outward at the base, and this needs to be restrained in some way, either with heavy sides and friction or angled cuts into bedrock or similar.

This same principle holds when the force acting on the arch is not vertical such as in spanning a doorway, but horizontal, such as in arched retaining walls or dams.

Even when using concrete, where the structure may be monolithic, the principle of the arch is used so as to benefit from the concrete's strength in resisting compressive stress. Where any other form of stress is raised, it has to be resisted by carefully placed reinforcement rods or fibres. (See Arch bridge.)

Other types

[[File:|thumb|The Delicate Arch, a natural arch in Moab, Utah]] A blind arch is an arch infilled with solid construction so it cannot function as a window, door, or passageway.

A dome is an arch rotated 360 degrees about its vertical axis.

Natural rock formations may also be referred to as arches. These natural arches are formed by erosion rather than being carved or constructed by man. See Arches National Park for examples.

A special form of the arch is the triumphal arch, usually built to celebrate a victory in war. A famous example is the Arc de Triomphe in Paris, France.

A vault is an arch extended along the axis perpendicular to the its plane; the groin vault is the intersection of two vaults.

Gallery

See also

References

  • Boyd, Thomas D. (1978), [Expression error: Unexpected < operator "The Arch and the Vault in Greek Architecture"], American Journal of Archaeology 82 (1): 83–100 (91) 
  • Galliazzo, Vittorio (1995), [Expression error: Unexpected < operator I ponti romani], Vol. 1, Treviso: Edizioni Canova, ISBN 88-85066-66-6 
  • O’Connor, Colin (1993), [Expression error: Unexpected < operator Roman Bridges], Cambridge University Press, ISBN 0-521-39326-4 
  • Rasch, Jürgen (1985), [Expression error: Unexpected < operator "Die Kuppel in der römischen Architektur. Entwicklung, Formgebung, Konstruktion"], Architectura 15: 117–139 
  • Roth, Leland M (1993). Understanding Architecture: Its Elements History and Meaning. Oxford, UK: Westview Press. ISBN 0-06-430158-3.  pp. 27–8

External links


Study guide

Up to date as of January 14, 2010

From Wikiversity

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Some class activities...

Contents

Find the Colour

Music Color

Email Review test

Hunt the Wumpus

  • The aim is to create a ppt presentation representing the famous text-based maze adventure - see wikipedia
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Go to wikipedia & search for arch, then


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

ARCH, in building, a constructional arrangement of blocks of any hard material, so disposed on the lines of some curve that they give mutual support one to the other.

The blocks, which are technically known as voussoirs, should be of a wedge shape, the centre or top block (see fig. I, A) being the keystone A; the lower blocks B B which rest on the supporting pier are the springers, the upper surface of which is called the FIG. I.

skewback, C C; the side blocks, as D, are termed the haunches. The lower surface or soffit of the arch is the intrados, E, and the upper surface the extrados, F. The rise of the arch is the distance from the springing to the soffit, G, the width between the springers is called the span, H, and the radius I. The triangular spaces between the arches are termed spandrils, K.

The arch is employed for two purposes: - (r) to span an opening in a wall and support the superstructure; (2) when continuous to form a vault known as a barrel or waggon vault.

The arch has been used from time immemorial by every nation, but owing to the tendency of the upper portion to sink, especially when bearing any superincumbent weight, it requires strong lateral support, and it is for this reason that in the earliest examples in unburnt brick at Nippur in Chaldaea, c. 4000 B.C., and at Rakakna (Requagna) and Dendera in Egypt, 3500-3000 B.C., it was employed only below the level of the ground which served as an abutment on either side.

In the building of an arch, the voussoirs have to be temporarily 1 The ultimate derivation of "arch" is the Latin arcus, a bow, or arch, in origin meaning something bent, from which through the French is also derived "arc," a curve. In French there are two words arche, one meaning a chest or coffer, from Latin area (arcere, to keep close), hence the English "ark"; the other meaning a vaulted arch, such as that of a bridge, and derived from a Low Latin corruption of arcus, into arca (du Cange, Glossarium, s.v.). The word "arch," prefixed to names of offices, seen in "archbishop," "archdeacon," "archduke," &c., means "principal" or "chief," and comes from the Greek prefix apxor &pv.- from tipxety, to begin, lead, or rule; it is also prefixed to other words, and usually with words implying hatred or detestation, such as "arch-fiend", "arch-scoundrel"; it is from an adaptation of this use, as seen in such expressions as "arch-rogue," extended to "arch-look," "archface," that the word comes to mean a mischievous, roguish expression of face or demeanour.

supported, until the keystone is inserted. This at the present day is effected by means of centreing an assemblage of timbers framed together, with its upper surface of the same form as the arch required; the voussoirs are laid on the centreing till the ring of the arch is completed. In the case of arches of small span, such as the early examples referred to, limited to about 6 ft., such centreing might be dispensed with in various ways, but it is difficult to see how the arches of the great entrance gateways, shown in the Assyrian bas-reliefs, could have been built without temporary support of some kind. In those days, when any amount of labour could be obtained, even the erection of a temporary wall might have been less costly than the employment of timber, of which there was great scarcity.

The Assyrian tradition would seem to have descended first to the Parthian builders, who in the palace of El Hadr built semicircular arches with regular voussoirs decoratively treated. The Sassanians who followed them employed the elliptical or eggshaped arch, of which the lower part was built in horizontal courses up to about one-third of the height, which lessened the span of the arched portion.

In Europe the earliest arches were those built by the Etruscans, either over canals (see article Architecture: Etruscan), or in the entrance gateways of their towns. The skew-arch in the gateway at Perugia shows great knowledge in its execution. From the Etruscans the adoption of the arch passed to the Romans, who certainly employed centreing of some kind, but always economized its use, as is clearly shown by Choisy. Although their walls from the Augustan age were built in concrete, arches of brick were always turned over their entrance doorways, sometimes in two or three rings. The Romans utilized the arch in other ways, sometimes burying it in their concrete construction, as in their vaults, and sometimes introducing it as a veneer only, as in the Pantheon. In their monumental structures in stone, the arch was sometimes built with regular voussoirs, i.e. with a semicircular extrados, and sometimes with the joint carried far beyond. The latter was not done in the early examples of the Tabularium and the Theatre of Marcellus, but in the Colosseum and all the arches of triumph the joints run through the spandrils, notwithstanding the recognition of the arch proper by its moulded archivolt.

Although the value of the pointed arch as a stronger constructional feature than the semicircular (owing to the tendency to sink in the keystone of the latter) had been recognized by the Assyrian builders, who employed it in their drains, it was not used systematically as an architectural feature till the gth century, in the mosque of Tulun at Cairo; it seems to have been regarded by the Mahommedans as an emblem of their faith, and its use spread through Syria to Persia, was brought to Sicily from Egypt, and was taken back by the Sicilian masons to Palestine and employed throughout theCrusaders'churches during the' 2 th century. As the pointed arch had already, for constructional reasons, been employed in Perigord from the commencement of the 11th century, it does not follow that the Crusaders brought it from Palestine, but there is no doubt that its universal employment in France early in the 12th century may have been partly due to its adoption in the Crusaders' churches. At first in Gothic work both the semicircular and pointed arches were used simultaneously in the same building, the larger arches being pointed, the smaller ones and windows being semicircular. The great value of the pointed arch in vaulting is described in the article Vault.

We have suggested that the pointed arch became an emblem of Mahommedan faith, and it was introduced in India but not as a constructive feature, for the Hindus objected to the arch, which they say never sleeps, meaning that it is always exerting a thrust which tends to its destruction. In India therefore it was built in horizontal courses with vertical slabs leaning against one another to form the apex. The Moors of north Africa, however, never employed it, preferring the horseshoe arch which they brought into Spain and developed in the mosque of Cordova. In the additions made to this mosque the prayer chamber was enriched by the caliph Mansur, who, to eke out the height, raised arch upon arch. In the Alhambra it appears in the decorative plaster work, and travels northwards into the south of France, where at Le Puy and elsewhere it is found decorating doorways and windows; in England it was employed towards the end of the 12th century.

About the middle of the 14th century at Gloucester the fourcentred pointed arch was introduced, which became afterwards the leading characteristic feature of the Tudor style. In France they adopted the three-centred arch in the 15th century.

The ogee arch was the natural result of the development of tracery in the commencement of the 14th century, and in Gloucester (about 1310) the foliations were run one into the other without the enclosing circles. About the middle of the 14th century, in the arcade of the first storey of the ducal palace in Venice, flowing tracery is found, from which the ogee arch there was probably derived, as throughout Venice it becomes the favourite feature in domestic architecture of that, and the succeeding century.

2. Semicircular arch, the centre of which is in the same line with its springers.

3. Segmental arch, where the centre is be- low the springing.

4. Horseshoe arch, with the centre above the springing; em- ployed in Moorish architecture.

5. Stilted arches, where the centre is below the springing, but the sides are carried down vertically.

6. Equilateral point- ed arches, described from two centres, the radius being the whole width of the arch.

7. Drop arches, with centres within the arch.

8. Lancet arches, with centres outside the arch.

9. Three centre arches, employed in French Flamboyant.

so. Four centre arches, employed in the Perpendicular and Tudor periods.

11. Ogee arches,with curves of counter flex- ure, found in English Decorated and French Flamboyant.

12. Pointed horse- shoe arches, found in the mosque of Tulun, Cairo, 9th century.

13. Pointed foiled arches, in the arcades of Beverley Minster (c. 1230) and Netley Abbey.

14. Cusped arch; Christchurch Priory, Hants.

55. Multifoil cusped arch, invented by the Moors at Cordova in the Loth century.

16. Flat arch, where the soffit is horizontal and sometimes slightly combined (dotted line).

17. Upright elliptical arch, sometimes called the egg-shaped arch, employed in Egyptian and Sassanian archi- tecture.

2

4

5

7

8

9

Io

II

12

14

16

17

18. The Tuscan arch, where the extrados takes the form of a pointed arch.

19. The joggled arch used in medieval chimneypieces and in Mahommedan archi- tecture.

zo. The discharging or relieving arch, built above the architrave or lintel to take off the weight of the super- structure.

21. The relieving arch as used in Egypt, in the pyramid of Cheops; and in Saxon architecture, where it was built with Roman bricks or tiles, or con- sisted of two sloping slabs of stone.

a 19

18

20

21

The arches are of various forms as follows:


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Bible wiki

Up to date as of January 23, 2010

From BibleWiki


an architectural term found only in Ezek 40:16, 21, 22, 26, 29. There is no absolute proof that the Israelites employed arches in their buildings. The arch was employed in the building of the pyramids of Egypt. The oldest existing arch is at Thebes, and bears the date B.C. 1350. There are also still found the remains of an arch, known as Robinson's Arch, of the bridge connecting Zion and Moriah. (See TYROPOEON VALLEY.)

This entry includes text from Easton's Bible Dictionary, 1897.

what mentions this? (please help by turning references to this page into wiki links)

This article needs to be merged with Arch (Catholic Encyclopedia).

Simple English

[[File:|thumb|An arch]]
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An arch is an opening in a building that is curved on top. The curved part can be round, like part of a circle, or pointed, like two parts of circles next to each other. Arches are often used where buildings are made of lots of small stones or bricks. The stone at the very top of the arch, called the keystone, keeps the rest of the arch stones from falling down. Arches can go over doorways and windows.

Arch can also mean to be clever or to know something.








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