Arch

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

An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, [1] or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it.

Contents

Arches may be synonymous with vaults, but a vault may be distinguished as a continuous arch [2] forming a roof. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture, [3] and their systematic use started with the ancient Romans, who were the first to apply the technique to a wide range of structures.

Basic concepts

Deformed arch at the Gozo Aqueduct, Malta Gozo fortified tower, windmills, aqueduct 16.jpg
Deformed arch at the Gozo Aqueduct, Malta

An arch is a pure compression form. [4] [5] [6] [7] It can span a large area by resolving forces into compressive stresses, and thereby eliminating tensile stresses. This is sometimes denominated "arch action". [8] As the forces in the arch are transferred to its base, the arch pushes outward at its base, denominated "thrust". As the rise, i. e. height, of the arch decreases the outward thrust increases. [9] In order to preserve arch action and prevent collapse of the arch, the thrust must be restrained, either by internal ties or external bracing, such as abutments. [10]

Fixed versus hinged arches

Rossgraben bridge (Rueggisberg) near Bern, Switzerland, showing the hinge at mid-span of this three-hinged arch. Rossgrabenbruecke 01 09.jpg
Rossgraben bridge (Rüeggisberg) near Bern, Switzerland, showing the hinge at mid-span of this three-hinged arch.

The most common kinds of true arch are the fixed arch, the two-hinged arch, and the three-hinged arch. [11]

The fixed arch is most often used in reinforced concrete bridges and tunnels, which have short spans. Because it is subject to additional internal stress from thermal expansion and contraction, this kind of arch is considered statically indeterminate. [10]

The two-hinged arch is most often used to bridge long spans. [10] This kind of arch has pinned connections at its base. Unlike that of the fixed arch, the pinned base can rotate, [12] thus allowing the structure to move freely and compensate for the thermal expansion and contraction that changes in outdoor temperature cause. However, this can result in additional stresses, and therefore the two-hinged arch is also statically indeterminate, although not as much as the fixed arch. [10]

The three-hinged arch is not only hinged at its base, like the two-hinged arch, yet also at its apex. The additional apical connection allows the three-hinged arch to move in two opposite directions and compensate for any expansion and contraction. This kind of arch is thus not subject to additional stress from thermal change. Unlike the other two kinds of arch, the three-hinged arch is therefore statically determinate. [11] It is most often used for spans of medial length, such as those of roofs of large buildings. Another advantage of the three-hinged arch is that the pinned bases are more easily developed than fixed ones, which allows shallow, bearing-type foundations in spans of medial length. In the three-hinged arch "thermal expansion and contraction of the arch will cause vertical movements at the peak pin joint but will have no appreciable effect on the bases," which further simplifies foundational design. [10]

Forms

Cathedral of St. Michael and St. Gudula in Brussels, Belgium, with a central pointed arch window, typical of Gothic architecture SteGudule.jpg
Cathedral of St. Michael and St. Gudula in Brussels, Belgium, with a central pointed arch window, typical of Gothic architecture
Semi-circular arches using brick and/or stone block construction at the Great Wall, China InsideGWWatchtower.jpg
Semi-circular arches using brick and/or stone block construction at the Great Wall, China
Roman aqueduct near Nimes, France: an arcade, employing the circular arch Pont du Gard - panoramio (11).jpg
Roman aqueduct near Nîmes, France: an arcade, employing the circular arch
Horseshoe arches in the 9th-century Mosque of Uqba, in Kairouan, Tunisia Arches and columns, Great Mosque of Kairouan.jpg
Horseshoe arches in the 9th-century Mosque of Uqba, in Kairouan, Tunisia

The many forms of arch are classified into three categories: circular, pointed, and parabolic. Arches can also be configured to produce vaults and arcades. [10]

Rounded, i. e. semicircular, arches were commonly used for ancient arches that were constructed of heavy masonry. [13] Ancient Roman builders relied heavily on the rounded arch to span great lengths. Several rounded arches that are constructed in-line and end-to-end in a series form an arcade, e. g. in Roman aqueducts. [14]

Pointed arches were most often used in Gothic architecture. [15] The advantage of a pointed arch, rather than a circular one, is that the arch action produces less horizontal thrust at the base. This innovation allowed for taller and more closely spaced openings, which are typical of Gothic architecture. [16] [17]

Interior vaulted ceiling of Notre Dame de Paris, showing the ribs at the intersection of several arches Notre-dame-de-paris-vue-interieure-salle-nord.jpg
Interior vaulted ceiling of Notre Dame de Paris, showing the ribs at the intersection of several arches

Vaults are essentially "adjacent arches [that] are assembled side by side." If vaults intersect, their intersections produce complex forms. The forms, along with the "strongly expressed ribs at the vault intersections, were dominant architectural features of Gothic cathedrals." [13]

The parabolic arch employs the principle that when weight is uniformly applied to an arch, the internal compression resulting from that weight will follow a parabolic profile. Of all forms of arch, the parabolic arch produces the most thrust at the base yet can span the greatest distances. It is commonly used in bridges, where long spans are needed. [13]

Tyne Bridge in Newcastle upon Tyne, England: a parabolic arch Tyne Bridge - Newcastle Upon Tyne - England - 2004-08-14.jpg
Tyne Bridge in Newcastle upon Tyne, England: a parabolic arch

The catenary arch has a different shape from the parabolic arch. Being the shape of the curve that a loose span of chain or rope traces, the catenary is the structurally ideal shape for a freestanding arch of constant thickness.

Forms of arch displayed chronologically, roughly in chronological order of development:

History

Bronze Age: ancient Near East

True arches, as opposed to corbel arches, were known by a number of civilizations in the ancient Near East including 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. [18] An example of the latter would be the Nippur arch, built before 3800 BC, [19] and dated by H. V. Hilprecht (1859–1925) to even before 4000 BC. [20] Rare exceptions are an arched mudbrick home doorway dated to circa 2000 BC from Tell Taya in Iraq [21] and two Bronze Age arched Canaanite city gates, one at Ashkelon (dated to c. 1850 BC), [22] and one at Tel Dan (dated to c. 1750 BC), both in modern-day Israel. [23] [24] An Elamite tomb dated 1500 BC from Haft Teppe contains a parabolic vault which is considered as one of the earliest evidences of arches in Iran.

Classical Persia and Greece

In ancient Persia, the Achaemenid Empire (550 BC–330 BC) built small barrel vaults (essentially a series of arches built together to form a hall) known as iwan , which became massive, monumental structures during the later Parthian Empire (247 BC–AD 224). [25] [26] [27] This architectural tradition was continued by the Sasanian Empire (224–651), which built the Taq Kasra at Ctesiphon in the 6th century AD, the largest free-standing vault until modern times. [28]

An early European example of a voussoir arch appears in the 4th century BC Greek Rhodes Footbridge. [29]

Ancient Rome

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

The Romans were the first builders in Europe, perhaps the first in the world, to fully appreciate the advantages of the arch, the vault and the dome. [30]

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 that was also assumed by domed structures from the 1st century BC onwards.

Arch of Caracalla at Theveste Porte Caracalla - Tebessa bb krkl - tbs@ 3.jpg
Arch of Caracalla at Theveste

The segmental arch was first built by the Romans who realized that an arch in a bridge did not have to be a semicircle, [31] [32] such as in Alconétar Bridge or Ponte San Lorenzo. They were also routinely used in house construction, as in Ostia Antica (see picture).

Ancient China

In ancient China, most architecture was wooden, including the few known arch bridges from literature and one artistic depiction in stone-carved relief. [33] [34] [35] Therefore, the only surviving examples of architecture from the Han Dynasty (202 BC – 220 AD) are rammed earth defensive walls and towers, ceramic roof tiles from no longer existent wooden buildings, [36] [37] [38] stone gate towers, [39] [40] and underground brick tombs that, although featuring vaults, domes, and archways, were built with the support of the earth and were not free-standing. [41] [42]

Roman and Chinese bridges in comparison

China's oldest surviving stone arch bridge is the Anji Bridge, built between 595 and 605 during the Sui Dynasty; it is the oldest open-spandrel segmental arch bridge in stone. [43] [44]

However, the ancient Romans had virtually all of these components beforehand; for example, Trajan's Bridge had open spandrels built in wood on stone pillars. [45]

Gothic Europe

The first example of an early Gothic arch in Europe is in Sicily in the Greek fortifications of Gela. The semicircular arch was followed in Europe by the pointed Gothic arch or ogive, whose centreline more closely follows the forces of compression and which is therefore stronger. The semicircular arch can be flattened to make an elliptical arch, as in the Ponte Santa Trinita. Parabolic arches were introduced in construction by the Spanish architect Antoni Gaudí, who admired the structural system of the Gothic style, but for the buttresses, which he termed "architectural crutches". The first examples of the pointed arch in the European architecture are in Sicily and date back to the Arab-Norman period.

Horseshoe arch: Aksum and Syria

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 from the Kingdom of Aksum in modern-day Ethiopia and Eritrea, dating from ca. 3rd–4th century. This is around the same time as the earliest contemporary examples in Roman Syria, suggesting either an Aksumite or Syrian origin for the type. [46]

India

Vaulted roof of an early Harappan burial chamber has been noted from Rakhigarhi. [47] S.R Rao reports vaulted roof of a small chamber in a house from Lothal. [48] Barrel vaults were also used in the Late Harappan Cemetery H culture dated 1900 BC-1300 BC which formed the roof of the metal working furnace, the discovery was made by Vats in 1940 during excavation at Harappa. [49] [50] [51]

C34B9768 Lady in the Arch Lady in arch of Shahi Mosque, Chitral.jpg
C34B9768 Lady in the Arch

In India, Bhitargaon temple (450 AD) and Mahabodhi temple (7th century AD) built in by Gupta Dynasty are the earliest surviving examples of the use of voussoir arch vault system in India. [52] The earlier uses semicircular arch, while the later contains examples of both gothic style pointed arch and semicircular arches. Although introduced in the 5th century, arches didn't gain prominence in the Indian architecture until 12th century after Islamic conquest. The Gupta era arch vault system was later used extensively in Burmese Buddhist temples in Pyu and Bagan in 11th and 12th centuries. [53]

Corbel arch: pre-Columbian Mexico

This article does not deal with a different architectural element, the corbel arch. However, it is worthwhile mentioning that corbel arches were found in other parts of ancient Asia, Africa, Europe, and the Americas. In 2010, a robot discovered a long arch-roofed passageway underneath the Pyramid of Quetzalcoatl, which stands in the ancient city of Teotihuacan north of Mexico City, dated to around 200 AD. [54]

Construction

A series of parabolic arches on the Mora d'Ebre bridge, Catalonia Pont d'arcades de Mora d'Ebre (Ribera d'Ebre, Catalonia).jpg
A series of parabolic arches on the Móra d'Ebre bridge, Catalonia

Since it is a pure compression form, the arch is useful because many building materials, including stone and unreinforced concrete, can resist compression, but are weak when tensile stress is applied to them (ref: similar to the AL-Karparo [8:04]). [55]

An arch is held in place by the weight of all of its members, making construction problematic. 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. Voussoirs are laid on it until the arch is complete and self-supporting. For an arch higher than head height, scaffolding would be required, so it could be combined with the arch support. Arches may fall when the frame is removed if design or construction has been faulty. The first attempt at the A85 bridge at Dalmally, Scotland suffered this fate, in the 1940s.[ citation needed ] 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.

In reinforced concrete construction, 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, such as tensile or torsional stress, it has to be resisted by carefully placed reinforcement rods or fibres. [56]

Other types

A depressed arch is one that appears "squashed" down at the top from the full arched shape. In pointed-arch styles, where there is a central point at the top of the arch, it may be a four-centred arch or Tudor arch.

A blind arch is an arch infilled with solid construction so it cannot function as a window, door, or passageway. These are common as decorative treatments of a wall surface in many architectural styles, especially Romanesque architecture.

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.

Rock formations may form natural arches through erosion, rather than being carved or constructed. [57] Structures such as this can be found in Arches National Park. Some rock balance sculptures are in the form of an arch.

The arches of the foot support the weight of the human body.

See also

Related Research Articles

Ancient Roman architecture Ancient architecture

Ancient Roman architecture adopted the external language of classical Greek architecture for the purposes of the ancient Romans, but was different from Greek buildings, becoming a new architectural style. The two styles are often considered one body of classical architecture. Roman architecture flourished in the Roman Republic and even moreso under the Empire, when the great majority of surviving buildings were constructed. It used new materials, particularly Roman concrete, and newer technologies such as the arch and the dome to make buildings that were typically strong and well-engineered. Large numbers remain in some form across the empire, sometimes complete and still in use to this day.

Dome An architectural element similar to the hollow upper half of a sphere; there are many types

A dome is an architectural element similar to the hollow upper half of a sphere; there is significant overlap with the term cupola, which may also refer to a dome or a structure on top of a dome. The precise definition of a dome has been a matter of controversy and there are a wide variety of forms and specialized terms to describe them.

Roman bridge

Roman bridges, built by ancient Romans, were the first large and lasting bridges built. Roman bridges were built with stone and had the arch as the basic structure. Most utilized concrete as well, which the Romans were the first to use for bridges.

Arch bridge

An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. A viaduct may be made from a series of arches, although other more economical structures are typically used today.

Triumphal arch Monumental structure in the shape of an archway

A triumphal arch is a free-standing monumental structure in the shape of an archway with one or more arched passageways, often designed to span a road. In its simplest form a triumphal arch consists of two massive piers connected by an arch, crowned with a flat entablature or attic on which a statue might be mounted or which bears commemorative inscriptions. The main structure is often decorated with carvings, sculpted reliefs, and dedications. More elaborate triumphal arches may have multiple archways.

Barrel vault Architectural element formed by the extrusion of a single curve

A barrel vault, also known as a tunnel vault or a wagon vault, is an architectural element formed by the extrusion of a single curve along a given distance. The curves are typically circular in shape, lending a semi-cylindrical appearance to the total design. The barrel vault is the simplest form of a vault: effectively a series of arches placed side by side. It is a form of barrel roof.

Theatre of Pompey Theatre in Ancient Rome

The Theatre of Pompey was a structure in Ancient Rome built during the latter part of the Roman Republican era by Pompey the Great. Completed in 55 BC, it was the first permanent theatre to be built in Rome.

Anji Bridge

The Anji Bridge is the world's oldest open-spandrel segmental arch bridge of stone construction. Credited to the design of a craftsman named Li Chun, the bridge was constructed in the years 595–605 during the Sui dynasty (581–618). Located in the southern part of Hebei Province, it is the oldest standing bridge in China. It is considered one of the Four Treasures of Hebei.

Pons Fabricius

The Pons Fabricius or Ponte dei Quattro Capi, is the oldest Roman bridge in Rome, Italy, still existing in its original state. Built in 62 BC, it spans half of the Tiber River, from the Campus Martius on the east side to Tiber Island in the middle. Quattro Capi refers to the two marble pillars of the two-faced Janus herms on the parapet, which were moved here from the nearby Church of St Gregory in the 14th century.

Corbel arch

A corbel 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.

Pons Cestius Roman stone bridge in Rome, Italy

The Pons Cestius is an ancient Roman bridge connecting the right bank of the Tiber with the west of the Tiber Island in Rome, Italy. In Late Antiquity, the bridge was replaced and renamed the Pons Gratiani. It is also known as the Italian: Ponte San Bartolomeo, lit. 'Bridge of Saint Bartholomew'. No more than one third of the present stone bridge is of ancient material, as it was entirely rebuilt and extended in the 19th century, after numerous earlier restorations.

Parabolic arch Type of arch shape

A parabolic arch is an arch in the shape of a parabola. In structures, their curve represents an efficient method of load, and so can be found in bridges and in architecture in a variety of forms.

Roman Bridge (Saint-Thibéry)

The Roman Bridge at Saint-Thibéry was a Roman bridge on the Via Domitia in southern France. The partly surviving structure crossed the river Hérault in Saint-Thibéry, 17 km (11 mi) east of Béziers.

White Bridge (Mysia)

The White Bridge was a Roman bridge across the river Granicus in Mysia in the north west of modern-day Turkey. Presumably constructed in the 4th century AD, it belonged in Ottoman times to the important road to Gallipoli on the Dardanelles. The structure was praised by early European travellers for its fine construction and marble facing, but was plundered for building material during the 19th century.

The Ponte San Lorenzo is a Roman bridge over the river Bacchiglione in Padua, Italy. Constructed between 47 and 30 BC, it is one of the very earliest segmental arched bridges in the world. It is also notable for the slenderness of its piers, unsurpassed in antiquity.

Bridge near Limyra

The Bridge near Limyra is a late Roman bridge in Lycia, in modern south-west Turkey, and one of the oldest segmented arch bridges in the world. Located near the ancient city of Limyra, it is the largest civil engineering structure of antiquity in the region, spanning the Alakır Çayı river over a length of 360 m (1,181.1 ft) on 26 segmental arches. These arches, with a span-to-rise ratio of 5.3:1, give the bridge an unusually flat profile, and were unsurpassed as an architectural achievement until the late Middle Ages. Today, the structure is largely buried by river sediments and surrounded by greenhouses. Despite its unique features, the bridge remains relatively unknown, and only in the 1970s did researchers from the Istanbul branch of the German Archaeological Institute carry out field examinations on the site.

Macestus Bridge

The Macestus Bridge or Bridge of Sultançayır was a Roman bridge across the Macestus River at Balıkesir, in the northwestern part of modern-day Turkey. Its flattened arches, slender piers and the hollow chamber system documented the progress made in late antique bridge building. A first cursory investigation of the 234 m long structure was conducted in the early 20th century, but since then its existence has been largely neglected by scholars. Current photos from 2009 show that the bridge has collapsed in the meantime.

History of early and simple domes

Cultures from pre-history to modern times constructed domed dwellings using local materials. Although it is not known when or where the first dome was created, sporadic examples of early domed structures have been discovered. Brick domes from the ancient Near East and corbelled stone domes have been found from the Middle East to Western Europe. These may indicate a common source or multiple independent traditions. A variety of materials have been used, including wood, mudbrick, or fabric. Indigenous peoples around the world produce similar structures today.

Segmental arch

A segmental arch is a type of arch with a circular arc of less than 180 degrees. It is sometimes also called a scheme arch.

Pointed arch (architecture) History and construction of pointed arch

A pointed arch, ogival arch, or Gothic arch is an arch with a pointed crown, whose two curving sides meet at a relatively sharp angle at the top of the arch. This architectural element was particularly important in Gothic architecture. It first appeared in Indian architecture and Islamic architecture as a way of making more decorative windows and doorways, but in the 12th century it began to be used in France and England as an important structural element, in combination with other elements, such as the rib vault and later the flying buttress. These allowed the construction of cathedrals, palaces and other buildings with dramatically greater height and larger windows which filled them with light.

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Further reading