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Arch

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File:St Louis Gateway Arch.jpg
Gateway Arch

An arch is a curved vertical structure spanning an open space underneath it.Template:Sfn Arches may support the load above them, or they may perform a purely decorative role. As a decorative element, the arch dates back to the 4th millennium BC, but structural load-bearing arches became popular only after their adoption by the Ancient Romans in the 4th century BC.Template:Sfn

Arch-like structures can be horizontal, like an arch dam that withstands the horizontal hydrostatic pressure load.Template:Sfn Arches are usually used as supports for many types of vaults, with the barrel vault in particular being a continuous arch.Template:Sfn Extensive use of arches and vaults characterizes an arcuated construction, as opposed to the trabeated system, where, like in the architectures of ancient Greece, China, and Japan (as well as the modern steel-framed technique), posts and beams dominate.Template:Sfn

Arches had several advantages over the lintel, especially in the masonry construction: with the same amount of material it can have larger span, carry more weight, and can be made from smaller and thus more manageable pieces.<ref name=britannica/> Their role in construction was diminished in the middle of the 19th century with introduction of the wrought iron (and later steel): the high tensile strength of these new materials made long lintels possible.

Basic conceptsEdit

TerminologyEdit

Template:Redirect A true arch is a load-bearing arch with elements held together by compression.Template:Sfn In much of the world introduction of the true arch was a result of European influence.Template:Sfn The term false arch has few meanings. It is usually used to designate an arch that has no structural purpose, like a proscenium arch in theaters used to frame the performance for the spectators, but is also applied to corbelled and triangular arches that are not based on compression.Template:SfnTemplate:Sfn

File:Arch illustration.svg
Masonry arch elements

A typical true masonry arch consists of the following elements:Template:SfnTemplate:SfnTemplate:Sfn

  1. Keystone, the top block in an arch. Portion of the arch around the keystone (including the keystone itself), with no precisely defined boundary, is called a crown
  2. Voussoir (a wedge-like construction block). A compound arch is formed by multiple concentric layers of voussoirs. The rowlock arch is a particular case of the compound arch,<ref>Template:M-W</ref> where the voussoir faces are formed by the brick headers.Template:Sfn
  3. Extrados (an external surface of the arch)
  4. Impost is block at the base of the arch (the voussoir immediately above the impost is a springer). The tops of imposts define the springing level. A portion of the arch between the springing level and the crown (centered around the 45° angleTemplate:Sfn) is called a haunch. If the arch resides on top of a column, the impost is formed by an abacus or its thicker version, dosseret.Template:Sfn
  5. Intrados (an underside of the arch, also known as a soffitTemplate:Sfn)
  6. Rise (height of the arc, distance from the springing level to the crown)
  7. Clear span
  8. AbutmentTemplate:Sfn The roughly triangular-shaped portion of the wall between the extrados and the horizontal division above is called spandrel.Template:Sfn

A (left or right) half-segment of an arch is called an arc, the overall line of an arch is arcatureTemplate:Sfn (this term is also used for an arcade).<ref>Template:M-W</ref> Archivolt is the exposed (front-facing) part of the arch, sometimes decorated (occasionally also used to designate the intrados).Template:Sfn If the sides of voussoir blocks are not straight, but include angles and curves for interlocking, the arch is called "joggled".Template:Sfn

Arch actionEdit

File:Arch action English.png
Arch (A) action diagram in comparison with a beam (B)

A true arch, due to its rise, resolves the vertical loads into horizontal and vertical reactions at the ends, a so called arch action. The vertical load produces a positive bending moment in the arch, while the inward-directed horizontal reaction from the spandrel/abutment provides a counterbalancing negative moment. As a result, the bending moment in any segment of the arch is much smaller than in a beam with the equivalent load and span.Template:Sfn The diagram on the right shows the difference between a loaded arch and a beam. Elements of the arch are mostly subject to compression (A), while in the beam a bending moment is present, with compression at the top and tension at the bottom (B).

In the past, when arches were made of masonry pieces, the horizontal forces at the ends of an arch (so called thrustTemplate:Sfn) caused the need for heavy abutments (cf. Roman triumphal arch). The other way to counteract the forces, and thus allow thinner supports, was to use the counter-arches, as in an arcade arrangement, where the horizontal thrust of each arch is counterbalanced by its neighbors, and only the end arches need to buttressed. With new construction materials (steel, concrete, engineered wood), not only the arches themselves got lighter, but the horizontal thrust can be further relieved by a tie connecting the ends of an arch (bowstring arch).<ref name=britannica>Template:Britannica</ref>

Funicular shapesEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} When evaluated from the perspective of an amount of material required to support a given load, the best solid structures are compression-only; with the flexible materials, the same is true for tension-only designs. There is a fundamental symmetry in nature between solid compression-only and flexible tension-only arrangements, noticed by Robert Hooke in 1676: "As hangs the flexible line, so but inverted will stand the rigid arch", thus the study (and terminology) of arch shapes is inextricably linked to the study of hanging chains, the corresponding curves or polygons are called funicular. Just like the shape of a hanging chain will vary depending on the weights attached to it, the shape of an ideal (compression-only) arch will depend on the distribution of the load.Template:Sfn

  • Analogy between an arch and a hanging chain and comparison to the dome of St Peter's Cathedral in Rome.png

    Analogy between an arch and a hanging chain and comparison to the dome of Saint Peter's Basilica in Rome (Giovanni Poleni, 1748)

  • Maqueta funicular.jpg

    A complex funicular model (Church of Colònia Güell by Gaudi, 19th century)

File:Pressure polygon.png
Arch diagram with pressure polygons drawn. A defect at the R-S portion of the intrados makes the arch susceptible to extra force along the line M-N, where the polygon curve can be pushed out of the envelope of the arch causing a collapse

While building masonry arches in the not very tall buildings of the past, a practical assumption was that the stones can withstand virtually unlimited amount of pressure (up to 100 N per mm2), while the tensile strength was very low, even with the mortar added between the stones, and can be effectively assumed to be zero. Under these assumptions the calculations for the arch design are greatly simplified: either a reduced-scale model can be built and tested, or a funicular curve (pressure polygon) can be calculated or modeled, and as long as this curve stays within the confines of the voussoirs, the construction will be stableTemplate:Sfn (a so called "safe theorem").

ClassificationsEdit

There are multiple ways to classify arches:Template:Sfn

  1. by the geometrical shape of its intrados (for example, semicircular, triangular, etc.);Template:Sfn<ref name=treccani>Template:Treccani</ref>
  2. for the arches with rounded intrados, by the number of circle segments forming the arch (for example, round arch is single-centred, pointed arch is two-centred);Template:Sfn
  3. by the material used (stone, brick, concrete, steel) and construction approach.Template:Sfn For example, the wedge-shaped voussoirs of a brick arch can be made by cutting the regular bricks ("axed brick" arch) or manufactured in the wedge shape ("gauged brick" arch);Template:Sfn
  4. structurally, by the number of hinges (movable joints) between solid components. For example, voussoirs in a stone arch should not move, so these arches usually have no hinges (are "fixed"). Permitting some movement in a large structure allows to alleviate stresses (caused, for example, by the thermal expansion), so many bridge spans are built with three hinges (one at each support and one at the crown) since the mid-19th century.Template:Sfn

ArrangementsEdit

A sequence of arches can be grouped together forming an arcade. Romans perfected this form, as shown, for example, by arched structures of Pont du Gard.Template:Sfn In the interior of hall churches, arcades of separating arches were used to separate the nave of a church from the side aisle,<ref>Günther Wasmuth (ed.): Wasmuths Lexikon der Baukunst, vol. 4: P - Zyp. Wasmuth, Berlin 1932, Template:P..</ref> or two adjacent side aisles.<ref>Template:Ill: Baustilkunde - Europäische Baukunst von der Antike bis zur Gegenwart. Sonderausgabe, Orbis Verlag, München 1988, Template:ISBN, Template:P..</ref>

Two-tiered arches, with two arches superimposed, were sometimes used in Islamic architecture, mostly for decorative purposes.Template:Sfn

An opening of the arch can be filled, creating a blind arch. Blind arches are frequently decorative, and were extensively used in Early Christian, Romanesque, and Islamic architecture.Template:Sfn Alternatively, the opening can be filled with smaller arches, producing a containing arch, common in Gothic and Romanesque architecture.Template:Sfn Multiple arches can be superimposed with an offset, creating an interlaced series of usually (with some exceptions) blind and decorative arches. Most likely of Islamic origin, the interlaced arcades were popular in Romanesque and Gothic architecture.Template:Sfn Rear-arch (also rere-arch) is the one that frames the internal side of an opening in the external wall.Template:Sfn

  • Pont du Gard - panoramio (11).jpg

    Arcades of Pont du Gard (Roman)

  • REI St Zeno 23.jpg

    Separating arches in the Template:Ill

  • ES Cordoba 1104 (150) (17245613545).jpg

    Two-tiered arches in the Mosque-Cathedral of Córdoba (Islamic)

  • Blind venetian arch, Chapel Milton Viaduct.jpg

    Large blind arch containing three smaller blind arches

  • Castle Acre Priory 05.jpg

    Interlaced arcade of blind arches at Castle Acre (Romanesque)

  • LangfordOxon StMatthew ChancelWindow.JPG

    Rear arch around three lights at St Matthew's Church, Langford

StructuralEdit

Structurally, relieving arches (often blind or containing) can be used to take off load from some portions of the building (for example, to allow use of thinner exterior walls with larger window openings, or, as in the Roman Pantheon, to redirect the weight of the upper structures to particular strong points).Template:Sfn Transverse arches, introduced in Carolingian architecture, are placed across the nave to compartmentalize (together with longitudinal separating arches) the internal space into bays and support vaults.Template:Sfn A diaphragm arch similarly goes in the transverse direction, but carries a section of wall on top. It is used to support or divide sections of the high roof.Template:Sfn Strainer arches were built as an afterthought to prevent two adjacent supports from imploding due to miscalculation. Frequently they were made very decorative, with one of the best examples provided by the Wells Cathedral. Strainer arches can be "inverted" (upside-down) while remaining structural.Template:SfnTemplate:Sfn When used across railway cuttings to prevent collapse of the walls, strainer arches may be referred to as flying arches.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:NHLE</ref> A counter-arch is built adjacent to another arch to oppose its horizontal action or help to stabilize it, for example, when constructing a flying buttress.Template:Sfn

  • Back of the Pantheon, Walking Tour, Rome (45506980035).jpg

    Relieving blind arches made of bricks at the Roman Pantheon

  • Kaiserdom Speyer Germany - panoramio (1).jpg

    Transverse arches in Speyer Cathedral

  • Firenze kosciol San Miniato 4.jpg

    Diaphragm arch in San Miniato al Monte

  • Wells Cathedral (St. Andrew) (17087358042).jpg

    "Scissors" strainer arch arrangement in Wells Cathedral includes an inverted arch

ShapesEdit

File:Types of arches.png
Types of arches

The large variety of arch shapes (left) can mostly be classified into three broad categories: rounded, pointed, and parabolic.<ref name="Building Structures">Template:Cite book</ref>

RoundedEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} "Round" semicircular arches were commonly used for ancient arches that were constructed of heavy masonry,<ref name="ambrose32">Template:Cite book</ref> and were relied heavily on by the Roman builders since the 4th century BC. It is considered to be the most common arch form,Template:Sfn characteristic for Roman, Romanesque, and Renaissance architecture.<ref name=treccani/>

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} A segmental arch, with a rounded shape that is less than a semicircle, is very old (the versions were cut in the rock in Ancient Egypt Template:Circa 2100 BC at Beni Hasan). Since then it was occasionally used in Greek temples,Template:Sfn utilized in Roman residential construction,Template:Sfn Islamic architecture, and got popular as window pediments during the Renaissance.Template:Sfn

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} A basket-handle arch (also known as depressed arch, three-centred arch, basket arch) consists of segments of three circles with origins at three different centers (sometimes uses five or seven segments, so can also be five-centred, etc.). Was used in late Gothic and Baroque architecture.Template:SfnTemplate:Sfn

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} A horseshoe arch (also known as keyhole arch) has a rounded shape that includes more than a semicircle, is associated with Islamic architecture and was known in areas of Europe with Islamic influence (Spain, Southern France, Italy). Occasionally used in Gothics, it briefly enjoyed popularity as the entrance door treatment in the interwar England.Template:Sfn

  • InsideGWWatchtower.jpg

    Semi-circular arches using brick and/or stone block construction at the Great Wall, China

  • Puente de Alconétar, Cáceres Province, Spain. Pic 03.JPG

    Segmental arch of the Alconétar Bridge

  • Fichtelnaab Bahnstrecke Regensburg–Oberkotzau bei Pappenfabrik.jpg

    Bridge with a basket handle arch

  • Great Mosque of Cordoba, mihrab area, 10th century (7) (29211135964).jpg

    Horseshoe arch in the Great Mosque of Cordoba

PointedEdit

File:Spitzbogen.png
Pointed arches, 1 - equilateral with trefoil treatment, 2 - blunt, 3 - lancet, 4 - ogee, 5 - four-centred, 6 - curtain (inflexed), 7 - pointed horseshoe

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} A pointed arch consists of two ("two-centred arch"Template:Sfn) or more circle segments culminating in a point at the top. It originated in the Islamic architecture, arrived in Europe in the second half of the 11th century (Cluny Abbey)Template:Sfn and later became prominent in the Gothic architecture.<ref>Template:Cite book</ref> The advantages of a pointed arch over a semicircular one are flexible ratio of span to riseTemplate:Sfn and lower horizontal reaction at the base. This innovation allowed for taller and more closely spaced openings, which are typical of Gothic architecture.<ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Equilateral arch is the most common form of the pointed arch, with the centers of two circles forming the intrados coinciding with the springing points of the opposite segment. Together with the apex point, they form an equilateral triangle, thus the name.Template:Sfn If the centers of circles are farther apart, the arch becomes a narrower and sharper lancet arch that appeared in France in the Early Gothic architecture (Saint-Denis Abbey) and became prominent in England in the late 12th and early 13th centuries (Salisbury Cathedral).Template:Sfn If the centers are closer to another, the result is a wider blunt arch.

The intrados of the cusped arch (also known as multifoil arch, polyfoil arch, polylobed arch, and scalloped arch) includes several independent circle segments in a scalloped arrangement. These primarily decorative arches are common in Islamic architecture and Northern European Late Gothic, can be found in Romanesque architecture.Template:Sfn A similar trefoil arch includes only three segments and sometimes has a rounded, not pointed, top. Common in Islamic architecture and Romanesque buildings influenced by it, it later became popular in the decorative motifs of the Late Gothic designs of Northern Europe.Template:Sfn

Each arc of an ogee arch consists of at least two circle segments (for a total of at least four), with the center of an upper circle being outside the extrados. After European appearance in the 13th century on the facade of the St Mark's Basilica, the arch became a fixture of the English Decorated style, French Flamboyant, Venetian, and other Late Gothic styles.Template:Sfn Ogee arch is also known as reversed curve arch, occasionally also called an inverted arch.Template:Sfn The top of an ogee arch sometimes projects beyond the wall, forming the so-called nodding ogee popular in 14th century England (pulpitum in Southwell Minster).Template:Sfn

Each arc of a four-centred arch is made of two circle segments with distinct centers; usually the radius used closer to the springing point is smaller with a more pronounced curvature. Common in Islamic architecture (Persian arch), and, with upper portion flattened almost to straight lines (Tudor archTemplate:Sfn), in the English Perpendicular Gothic.Template:SfnA keel arch is a variant of four-centred arch with haunches almost straight, resembling a section view of a capsized ship. Popular in Islamic architecture, it can be also found in Europe, occasionally with a small ogee element at the top,Template:Sfn so it is sometimes considered to be a variation of an ogee arch.Template:Sfn

Curtain arch (also known as inflexed arch, and, like the keel arch, usually decorative<ref name=treccani/>) uses two (or more) drooping curves that join at the apex. Utilized as a dressing for windows and doors primarily in Saxony in the Late Gothic and early Renaissance buildings (late 15th to early 16th century), associated with Template:Ill.Template:Sfn When the intrados has multiple concave segments, the arch is also called a draped arch or tented arch.Template:Sfn A similar arch that uses a mixture of curved and straight segmentsTemplate:Sfn or exhibits sharp turns between segmentsTemplate:Sfn is a mixed-line arch (or mixtilinear arch). In Moorish architecture the mixed-line arch evolved into an ornate lambrequin arch,<ref>Template:Cite book</ref> also known as muqarnas arch.

ParabolicEdit

The popularity of the arches using segments of a circle is due to simplicity of layout and construction,Template:Sfn not their structural properties. Consequently, the architects historically used a variety of other curves in their designs: elliptical curves, hyperbolic cosine curves (including catenary), and parabolic curves. There are two reasons behind the selection of these curves:Template:Sfn

  1. they are still relatively easy to trace with common tools prior to construction;
  2. depending on a situation, they can have superior structural properties and/or appearance.

The hyperbolic curve is not easy to trace, but there are known cases of its use.Template:Sfn The non-circumferential curves look similar, and match at shallow profiles, so a catenary is often misclassified as a parabolaTemplate:Sfn (per Galileo, "the [hanging] chain fits its parabola almost perfectly"Template:Sfn). González et al. provide an example of Palau Güell, where researchers do not agree on classification of the arches or claim the prominence of parabolic arches, while the measurements show that just two of the 23 arches designed by Gaudi are actually parabolic.Template:Sfn

Three parabolic-looking curves in particular are of significance to the arch design: parabola itself, catenary, and weighted catenary. The arches naturally use the inverted (upside-down) versions of these curves.

A parabola represents an ideal (all-compression) shape when the load is equally distributed along the span, while the weight of the arch itself is negligible. A catenary is the best solution for the case where an arch with uniform thickness carries just its own weight with no external load. The practical designs for bridges are somewhere in between, and thus use the curves that represent a compromise that combines both the catenary and the funicular curve for particular non-uniform distribution of load.Template:Sfn The practical free-standing arches are stronger and thus heavier at the bottom, so a weighted catenary curve is utilized for them. The same curve also fits well an application where a bridge consists of an arch with a roadway of packed dirt above it, as the dead load increases with a distance from the center.Template:Sfn

OtherEdit

Unlike regular arches, the flat arch (also known as jack arch, lintel arch, straight arch, plate-bande<ref>Template:Cite book</ref>) is not curved. Instead, the arch is flat in profile and can be used under the same circumstances as lintel. However, lintels are subject to bending stress, while the flat arches are true arches, composed of irregular voussoir shapes (the keystone is the only one of the symmetric wedge shape),Template:Sfn and that efficiently uses the compressive strength of the masonry in the same manner as a curved arch and thus requires a mass of masonry on both sides to absorb the considerable lateral thrust. Used in the Roman architecture to imitate the Greek lintels, Islamic architecture, European medieval and Renaissance architecture. The flat arch is still being used as a decorative pattern, primarily at the top of window openings.Template:Sfn

False archesEdit

The corbel (also corbelled) arch, made of two corbels meeting in the middle of the span, is a true arch in a sense of being able to carry a load, but it is false in a structural sense, as its components are subject to bending stress. The typical profile is not curved, but has triangular shape. Invented prior to the semicircular arch, the corbel arch was used already in the Egyptian and Mycenaean architecture in the 3rd and 2nd millennium BC.Template:Sfn

Like a corbel arch, the triangular arch is not a true arch in a structural sense. Its intrados is formed by two slabs leaning against each other.Template:Sfn Brick builders would call triangular any arch with straight inclined sides.<ref>Template:Cite book</ref> The design was common in Anglo-Saxon England until the late 11th century (St Mary Goslany).Template:Sfn Mayan corbel arches are sometimes called triangular due to their shape.Template:Sfn

  • Cucinone di palazzo pitti, cappa con piattabanda attr. al dis. del buontalenti 02.jpg

    Flat arch in the kitchen of Pitti Palace

  • Refugi pedra Tales.jpg

    Triangular arch

  • White Castle, arrow slit.jpg

    A triangular arch built using masonry

  • Kabah Arch 2002.12.29 27.jpg

    Mayan corbelled arch

VariationsEdit

Few transformations can be applied to arch shapes.

If one impost is much higher than another, the arch (frequently pointed) is known as ramping arch, raking arch,Template:Sfn or rampant arch (from Template:Langx).Template:Sfn Originally used to support inclined structures, like stairs, in the 13th-14th centuries they appeared as parts of flying buttresses used to counteract the thrust of Gothic ribbed vaults.<ref name=treccani1991/>

A central part of an arch can be raised on short vertical supports, creating a trefoil-like shouldered arch. The raised central part can vary all the way from a flat arch to ogee. The shouldered arches were used to decorate openings in Europe from medieval times to Late Gothic architecture, became common in Iranian architecture from the 14th century, and were later adopted in the Ottoman Turkey.Template:Sfn

In a stilted arch (also surmounted<ref>Template:M-W</ref>), the springing line is located above the imposts (on "stilts"). Known to Islamic architects by the 8th century, the technique was utilized to vertically align the apexes of arches of different dimensions in Romanesque and Gothic architecture.Template:Sfn Stilting was useful for semicircular arches, where the ratio of the rise fixed at Template:Frac of the span, but was applied to the pointed arches, too.

The skew arch (also known as an oblique arch) is used when the arch needs to form an oblique angle in the horizontal plane with respect to the (parallel) springings,Template:SfnTemplate:Sfn for example, when a bridge crosses the river at an angle different than 90°. A splayed arch is used for the case of unequal spans on the sides of the arch (when, for example, an interior opening in the wall is larger than the exterior one), the intrados of a round splayed arch is not cylindrical, but has a conical shape.<ref>Template:MW</ref>Template:Sfn

  • Palau Dalmases.jpg

    Ramping arches at Template:Ill in Barcelona

  • Frauenstein Lorenziberg Filialkirche hl Laurentius Vorlaube Schulterbogenportal 25042017 7964.jpg

    Shouldered arch around the door of Template:Ill. The raised portion is a flat arch.

  • Doges Palace 5 (7243239310).jpg

    Shouldered arch above the main entrance of Doge's Palace in Venice. The vertical supports separate the segments of an ogee arch.

  • St John's Chapel, Tower of London.jpg

    The smaller arches at the lower level are stilted to match the wider arches on the left (St John's Chapel, London)

  • Nave and left aisle - Cathedral of Monreale - Italy 2015.JPG

    Stilted pointed arches at the Monreale Cathedral)

  • Sickergill Skew Bridge in 1898.jpg

    Skew arch (Sickergill Bridge) with helicoidal masonry courses

  • All Saints Church - splayed tower window - geograph.org.uk - 1361830.jpg

    Splayed arch over a window opening in the All Saints Church in Chedgrave

A wide arch with its rise less than Template:Frac of the span (and thus the geometric circle of at least one segment is below the springing line) is called a surbased arch<ref>Template:M-W</ref> (sometimes also a depressed archTemplate:Sfn). A drop arch is either a basket handle archTemplate:Sfn or a blunt arch.<ref>Template:M-W</ref>

Hinged archesEdit

{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}}

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

Practical arch bridges are built either as a fixed arch, a two-hinged arch, or a three-hinged arch.<ref name="Reynolds's Reinforced Concrete Designer's Handbook, p 41" /> 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 statically indeterminate (the internal state is impossible to determine based on the external forces alone).<ref name="Building Structures"/>

The two-hinged arch is most often used to bridge long spans.<ref name="Building Structures" /> This kind of arch has pinned connections at its base. Unlike that of the fixed arch, the pinned base can rotate,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="Building Structures" />

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.<ref name="Reynolds's Reinforced Concrete Designer's Handbook, p 41">Template:Cite book</ref> 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 reaction of the pinned bases is more predictable than the one for the fixed arch, allowing 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.<ref name="Building Structures" />

HistoryEdit

The arch became popular in the Roman times and mostly spread alongside the European influence, although it was known and occasionally used much earlier. Many ancient architectures avoided the use of arches, including the Viking and Hindu ones.Template:Sfn

Bronze Age: ancient Near EastEdit

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.<ref name="Jürgen Rasch 117">Template:Harvnb</ref> An example of the latter would be the Nippur arch, built before 3800 BC,<ref>John P. Peters, University of Pennsylvania Excavations at Nippur. II. The Nippur Arch, The American Journal of Archaeology and of the History of the Fine Arts, vol. 10, no. 3, pp. 352–368, (Jul. – Sep., 1895)</ref> and dated by H. V. Hilprecht (1859–1925) to even before 4000 BC.<ref>New Schaff-Herzog Encyclopedia of Religious Knowledge, Vol. I: Babylonia: V. The People, Language, and Culture.: 7. The Civilization. Retrieved 9 April 2020.</ref> Rare exceptions are an arched mudbrick home doorway dated to Template:Circa from Tell Taya in Iraq<ref>Template:Cite journal</ref> and two Bronze Age arched Canaanite city gates, one at Ashkelon (dated to Template:Circa),<ref>Template:Cite news</ref> and one at Tel Dan (dated to Template:Circa), both in modern-day Israel.<ref name="FinkelsteinMazar2007">Template:Cite book</ref><ref>Frances, Rosa: The three-arched middle Bronze Age gate at Tel Dan - A structural investigation of an extraordinary archaeological site, retrieved 9 April 2020.</ref> An Elamite tomb dated 1500 BC from Haft Teppe contains a parabolic vault which is considered one of the earliest evidences of arches in Iran.

The use of true arches in Egypt also originated in the 4th millennium BC (underground barrel vaults at the Dendera cemetery). Standing arches were known since at least the Third Dynasty, but very few examples survived, since the arches were mostly used in non-durable secular buildings and made of mud brick voussoirs that were not wedge-shaped, but simply held in place by mortar, and thus susceptible to a collapse (the oldest arch still standing is at Ramesseum). Sacred buildings exhibited either lintel design or corbelled arches. Arches were mostly missing in Egypt temples even after the Roman conquest, even though Egyptians thought of the arch as a spiritual shape and used it in the rock-cut tombs and portable shrines.Template:Sfn Auguste Mariette suggested that this choice was based on a relative fragility of a vault: "what would remain of the tombs and temples of Egyptians today, if they had preferred the vault?"<ref name=treccani/>

Mycenaean architecture utilized only the corbel arches in their beehive tombs with triangular openings.Template:Sfn Mycenaeans had also built probably the oldest still standingTemplate:Cn stone-arch bridge in the world, Arkadiko Bridge, in Greece.

As evidenced by their imitations of the parabolic arches, Hittites most likely were exposed to the Egyptian designs, but used the corbelled technique to build them.Template:Sfn

Classical Persia and GreeceEdit

The Assyrians, also apparently under the Egyptian influence, adopted the true arch (with a slightly pointed profile) early in the 8th century.Template:Sfn 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).<ref>Brosius, Maria (2006), The Persians: An Introduction, London & New York: Routledge, p. 128, Template:ISBN.</ref><ref>Garthwaite, Gene Ralph (2005), The Persians, Oxford & Carlton: Blackwell Publishing, Ltd., p. 84, Template:ISBN.</ref><ref>Schlumberger, Daniel (1983), "Parthian Art", in Yarshater, Ehsan, Cambridge History of Iran, 3.2, London & New York: Cambridge University Press, p. 1049, Template:ISBN.</ref> 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.<ref>Wright, G. R. H., Ancient building technology vol. 3. Leiden, Netherlands. Koninklijke Brill NV. 2009. p. 237. Print.</ref>

An early European example of a voussoir arch appears in the 4th century BC Greek Rhodes Footbridge.Template:SfnTemplate:Sfn Proto-true arches can also be found under the stairs of the temple of Apollo at Didyma and the stadium at Olympia.Template:Sfn .

  • Gabriel Tranchard-Foto 1853 Khorsabad.jpg

    Arch at the excavation in Dur-Sharrukin (Assyrian architecture, end of 8th century BC, photo taken in 1853)

  • Didyma, Temple of Apollo, Passageway under Temple, Turkey - panoramio.jpg

    Vault underneath the temple of Apollo in Didyma, Turkey (4th century BC)

  • 02Στάδιο Αρχαίας Ολυμπίας01.jpg

    Arch at the stadium of Olympia (4th century BC)

Ancient RomeEdit

The ancient Romans learned the semicircular arch from the Etruscans (both cultures apparently adopted the design in the 4th century BCTemplate:Sfn), 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.<ref name="Robertson">Template:Cite book</ref>

Throughout the Roman Empire, from Syria to Scotland, engineers erected arch structures. The first use of arches was for civic structures, like drains and city gates. Later the arches were utilized for major civic buildings bridges and aqueducts, with the outstanding 1st century AD examples provided by the Colosseum, Pont Du Gard, and the aqueduct of Segovia.Template:Sfn The introduction of the ceremonial triumphal arch dates back to Roman Republic, although the best examples are from the imperial times (Arch of Augustus at Susa, Arch of Titus).Template:Sfn

Romans initially avoided using the arch in the religious buildings and, in Rome, arched temples were quite rare until the recognition of Christianity in 313 AD (with the exceptions provided by the Pantheon and the "temple of Minerva Medica"Template:Check). Away from the capital, arched temples were more common (Template:Ill, temple of Jupiter at Sbeitla, Severan temple at Djemila).Template:Sfn Arrival of Christianity prompted creation of the new type of temple, a Christian basilica, that made a thorough break with the pagan tradition with arches as one of the main elements of the design, along with the exposed brick walls (Santa Sabina in Rome, Sant'Apollinare in Classe). For a long period, from the late 5th century to the 20th century, arcades were a standard staple for the Western Christian architecture.Template:Sfn

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.

The segmental arch was first built by the Romans who realized that an arch in a bridge did not have to be a semicircle,<ref>Template:Harvnb</ref><ref>Template:Harvnb</ref> such as in Alconétar Bridge or Ponte San Lorenzo. The utilitarian and mass residential (insulae) buildings, as found in Ostia Antica and Pompeii, mostly used low segmental arches made of bricks and architraves made of wood, while the concrete lintel arches can be found in villas and palaces.Template:Sfn

  • Falerii novi.JPG

    The Jupiter gate at Falerii Novi (Template:Circa 300 BC)

  • Acueduct of Segovia.jpg

    Arches of the aqueduct at Segovia

  • Laika ac Colosseum (9487556579).jpg

    Arches of the Colosseum

  • Arco di Augusto-Susa.jpg

    Arch of Augustus, Susa, Piedmont (Template:Circa 8 BC)

  • Tempio di Minerva Medica 21-09-2019.jpg

    Arches at the "temple of Minerva Medica" in Rome

  • The Temple of Hadrian (16127691050).jpg

    Temple of Hadrian at Ephesus combines a semicircular arch with the lintels (117 AD)

  • Trois temples 13 - cropped (Temple of Jupiter).png

    Temple of Jupiter at Sbeitla (Template:Circa 150 AD)

  • S Sabina - portico 1000013.JPG

    Arches in the narthex of Santa Sabina, Rome (Template:Circa 425 AD)

  • QDFV Basilica di Sant Apollinare in Classe - Ravenna.jpg

    Arches and dome in Sant'Apollinare in Classe (534-536 AD)

  • OstianInsula.JPG

    Segmental arches in an Ostian insula

Ancient ChinaEdit

Ancient architecture of China (and Japan) used mostly timber-framed construction and trabeated system.Template:Sfn Arches were little-used, although there are few arch bridges known from literature and one artistic depiction in stone-carved relief.<ref>Needham, Joseph (1986), Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 3, Civil Engineering and Nautics, Taipei: Caves Books, pp. 161–188, Template:ISBN.</ref><ref>Needham, Joseph (1986), Science and Civilisation in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering, Taipei: Caves Books, pp. 171–172 Template:ISBN.</ref><ref>Liu, Xujie (2002), "The Qin and Han dynasties", in Steinhardt, Nancy S., Chinese Architecture, New Haven: Yale University Press, p. 56, Template:ISBN.</ref> Since the only surviving artefacts 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,<ref>Wang, Zhongshu (1982), Han Civilization, translated by K.C. Chang and Collaborators, New Haven and London: Yale University Press, pp. 1, 30, 39–40, Template:ISBN.</ref><ref>Chang, Chun-shu (2007), The Rise of the Chinese Empire: Volume II; Frontier, Immigration, & Empire in Han China, 130 B.C. – A.D. 157, Ann Arbor: University of Michigan Press, pp. 91–92, Template:ISBN.</ref><ref>Morton, William Scott; Lewis, Charlton M. (2005), China: Its History and Culture (Fourth ed.), New York City: McGraw-Hill, p. 56, Template:ISBN.</ref> stone gate towers,<ref>Liu, Xujie (2002), "The Qin and Han dynasties", in Steinhardt, Nancy S., Chinese Architecture, New Haven: Yale University Press, p. 55, Template:ISBN.</ref><ref>Steinhardt, Nancy Shatzman (2005), "Pleasure tower model", in Richard, Naomi Noble, Recarving China's Past: Art, Archaeology, and Architecture of the 'Wu Family Shrines, New Haven and London: Yale University Press and Princeton University Art Museum, pp. 279–280, Template:ISBN.</ref> and underground brick tombs, the known vaults, domes, and archways were built with the support of the earth and were not free-standing.<ref>Wang, Zhongshu (1982), Han Civilization, translated by K.C. Chang and Collaborators, New Haven and London: Yale University Press, pp. 175–178, Template:ISBN.</ref><ref>Watson, William (2000), The Arts of China to AD 900, New Haven: Yale University Press, p. 108, Template:ISBN.</ref>

China's oldest surviving stone arch bridge is the Anji Bridge. Still in use, it was built between 595 CE and 605 CE during the Sui dynasty.<ref>Knapp, Ronald G. (2008). Chinese Bridges: Living Architecture From China's Past. Singapore: Tuttle Publishing. pp. 122–127. Template:ISBN.</ref><ref>Needham, Joseph. The Shorter Science and Civilisation in China. Cambridge University Press, 1994. Template:ISBN. pp. 145–147.</ref>

  • Anji Bridge, Zhao County, 2020-09-06 05.jpg

    Anji Bridge: segmental arch, open-spandrel design

IslamicEdit

Islamic architects adopted the Roman arches, but had quickly shown their resourcefulness: by the 8th century the simple semicircular arch was almost entirely replaced with fancier shapes, few fine examples of the former in the Umayyad architecture notwithstanding (cf. the Great Mosque of Damascus, 706–715 CE). The first pointed arches appear already at the end of the 7th century AD (Al-Aqsa Mosque, Palace of Ukhaidhir, cisterns at the White Mosque of RamleTemplate:SfnTemplate:Sfn). Their variations spread fast and wide: Mosque of Ibn Tulun in Cairo (876-879 AD), Nizamiyya Madrasa at Khar Gerd (now Iran, 11th century), Kongo Mosque in Diani Beach (Kenya, 16th century).Template:SfnTemplate:Sfn

Islamic architecture brought to life a large amount of arch forms: the round horseshoe arch that became a characteristic trait of the Islamic buildings, the keel arch, the cusped arch, and the mixed-line arch (where the curved "ogee swell" is interspersed with abrupt bends).Template:Sfn The Great Mosque of Cordoba, that can be considered a catalogue of Islamic arches, contains also the arches with almost straight sides, trefoil, interlaced, and joggled. Mosque of Ibn Tulun adds four-centred and stilted version of the pointed arch.Template:Sfn

It is quite likely that the appearance of the pointed arch, an essential element of the Gothic style, in Europe (Monte Cassino, 1066–1071 AD, and the Cluny Abbey five years later) and the ogee arch in Venice (Template:Circa 1250) is a result of the Islamic influence,Template:Sfn possibly through Sicily.Template:Sfn SaoudTemplate:Sfn also credits to Islamic architects the spread of the transverse arch. Mixed-line arch became popular in the Mudéjar style and subsequently spread around the Spanish-speaking world.Template:Sfn

  • CSC 0117 (5299538961).jpg

    Semicircular arches at the Umayyad mosque

  • Cisterns of the White Mosque, Ramla IMG 5271.JPG

    Pointed arches in the cisterns of the White Mosque in Ramla

  • Cordoue - Mosquée - arcature 2.JPG

    Trefoil arches at the Cordoba Mosque

  • CordobaMezquita01.jpg

    Interlaced arches at the Cordoba Mosque

  • Cordoue - Mosquée - arcature.JPG

    Horseshoe arches at the Cordoba Mosque

  • Córdoba 2014.06.jpg

    Ogee arch at the Cordoba Mosque

  • Detalle de la Puerta del Perdón - Mezquita de Córdoba.jpg

    Cusped arhes at the Cordoba Mosque

  • Mixed line arches.png

    Mixed line arches at Palacio de Torre Tagle, Lima, Peru (1735)

Western EuropeEdit

The collapse of the Western Roman Empire left the church as the only client of major construction; with all pre-Romanesque architectural styles borrowing from Roman construction with its semicircular arch. Due to the decline in the construction quality, the walls were thicker, and the arches thus heavier, than their Roman prototypes. Eventually the architects started to use the depth of the arches for decoration, turning the deep opening into recessed orders (or rebated arch, a sequence of progressively smaller concentric arches, each inset with a rebate).Template:Sfn

Romanesque style started experiments with the pointed arch late in the 11th century (Cluny Abbey). In few decades, the practice spread (Durham Cathedral, Basilica of Saint-Denis). Early Gothic utilized the flexibility of the pointed arch by grouping together arches of different spans but with the same height.Template:Sfn

While the arches used in the mediaeval Europe were borrowed from the Roman and Islamic architecture, the use of pointed arch to form the rib vault was novel and became the defining characteristic of Gothic construction. At about 1400 AD, the city-states of Italy, where the pointed arch had never gotten much traction, initiated the revival of the Roman style with its round arches, Renaissance. By the 16th century the new style spread across Europe and, through the influence of empires, to the rest of the world. Arch became a dominant architectural form until the introduction of the new construction materials, like steel and concrete.Template:Sfn

IndiaEdit

The history of arch in India is very long (some arches were apparently found in excavations of Kosambi, 2nd millennium BC. However, the continuous history begins with rock-cut arches in the Lomas Rishi cave (3rd century BC).Template:Sfn Vaulted roof of an early Harappan burial chamber has been noted at Rakhigarhi.<ref>Template:Cite book</ref> S.R Rao reports vaulted roof of a small chamber in a house from Lothal.<ref>Template:Cite book</ref> 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.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref>

The use of arches until the Islamic conquest of India in the 12th century AD was sporadic, with ogee arches and barrel vaults in rock-cut temples (Karla Caves, from the 1st century BC) and decorative pointed gavaksha arches. By the 5th century AD voussoir vaults were used structurally in the brick construction. Surviving examples include the temple at Bhitargaon (5th century AD) and Mahabodhi Temple (7th century AD), the latter has both pointed arches and semicircular arches.Template:Sfn<ref>Template:Cite book</ref> These Gupta era arch vault system was later used extensively in Burmese Buddhist temples in Pyu and Bagan in 11th and 12th centuries.<ref>Template:Cite book</ref>

With the arrival of Islamic and other Western Asia influence, the arches became prominent in the Indian architecture, although the post and lintel construction was still preferred. A variety of pointed and lobed arches was characteristic for the Indo-Islamic architecture, with the monumental example of Buland Darwaza, that has pointed arch decorated with small cusped arches.Template:Sfn

  • Barabar Caves inside Lomas Rishi cave.jpg

    The insides of the Lomas Rishi cave

  • 029 Chaitya and Roof (33563756881).jpg

    Arches at Karle (Great Chaitya, 1st century AD)

  • Ajanta Caves, Aurangabad s-7.jpg

    Decorative ogee arches (gavaksha) in Ajanta Caves

  • Inner sanctum of Mahabodhi temple at Bodhgaya in Bihar. 07.jpg

    Pointed vault at the Mahabodhi temple

  • Fatehput Sikiri Buland Darwaza gate 2010-color change.jpg

    Arches at Buland Darwaza (16th century AD)

Pre-Columbian AmericaEdit

Mayan architecture utilized the corbel arches. The other Mesoamerican cultures used only the flat roofs with no arches whatsoever,Template:Sfn although some researchers had suggested that both Maya and Aztec architects understood the concept of a true arch.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Revival of the trabeated systemEdit

The 19th-century introduction of the wrought iron (and later steel) into construction changed the role of the arch. Due to the high tensile strength of new materials, relatively long lintels became possible, as was demonstrated by the tubular Britannia Bridge (Robert Stephenson, 1846-1850). A fervent proponent of the trabeated system, Alexander "Greek" Thomson, whose preference for lintels was originally based on aesthetic criteria, observed that the spans of this bridge are longer than that of any arch ever built, thus "the simple, unsophisticated stone lintel contains in its structure all the scientific appliances [...] used in the great tubular bridge. [...] Stonehenge is more scientifically constructed than York Minster."<ref>Template:Cite journal</ref> Use of arches in bridge construction continued (the Britannia Bridge was rebuilt in 1972 as a truss arch bridge), yet the steel frames and reinforced concrete frames mostly replaced the arches as the load-bearing elements in buildings.

  • Britanniabruecke Postkarte coloriert2.jpg

    Original Britannia bridge (a colored postcard)

  • Pont Britannia - geograph.org.uk - 692277.jpg

    Britannia bridge (2008)

ConstructionEdit

File:Pont d'arcades de Móra d'Ebre (Ribera d'Ebre, Catalonia).jpg
A series of parabolic arches on the Móra d'Ebre bridge, Catalonia, Spain (2005)

As a pure compression form, the utility of the arch is due to many building materials, including stone and unreinforced concrete, being strong under compression, but brittle when tensile stress is applied to them.<ref>Template:Cite book</ref>

MasonryEdit

The voussoirs can be wedge-shaped or have a form of a rectangular cuboid, in the latter case the wedge-like shape is provided by the mortar.<ref name=treccani1991>Template:Treccani</ref>

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.Template:Citation needed

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

Reinforced concreteEdit

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.<ref>Template:Cite book</ref>

Architectural stylesEdit

The type of arches (or absence of them) is one of the most prominent characteristics of an architectural style. For example, when Heinrich Hübsch, in the 19th century, tried to classify the architectural style, his "primary elements" were roof and supports, with the top-level basic types: trabeated (no arches) and arcuated (arch-based). His next division for the arcuated styles was based on the use of round and pointed arch shapes.Template:Sfn

Cultural referencesEdit

The steady horizontal push of an arch against the abutments gave rise to a saying "the arch never sleeps", attributed to many sources, from HinduTemplate:Sfn to Arabs.<ref name=treccani/> This adage stresses that the arch carries "a seed of death" for itself and the structure containing it, a statement that can be made upon observation of the Roman ruins.<ref name=treccani/> The plot of The Nebuly Coat by J. Meade Falkner, inspired by a collapse of a tower at the Chichester Cathedral plays with the idea while dealing with the slow disintegration of a church building.Template:Sfn SaoudTemplate:Sfn explains the proverb by chain-like self-balancing of the horizontal and vertical forces in the arch and its "universal adaptability".Template:Sfn

See alsoEdit

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ReferencesEdit

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SourcesEdit

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External linksEdit

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