ARCHS , VAULTS AND DOMES

Arches always generate the section of vaulted structures.
• Vaults are generated by the projection of the arch section on a plan, which is most of the time horizontal.
• Domes are basically shaped by the rotation of the arch section around a vertical axis. They can be built on circular or quadrangular plans.

The main exceptions to this principle are:
• Domes on squinches are made by a succession of increasing arches starting from the corners. The squinche looks like a half cone or portion of a cone, if the generating arch is not pointed.
• Faceted domes are generated by the intersection of vaults, like the cloister dome. But it is built on a faceted plan and not a square or quadrangular plan like the cloister dome.
• Groined vaults or domes are the intersection of two vaults crossing each other. Most of the time, they cross perpendicularly.
• Cloister domes are also generated by the intersection of two vaults crossing each other, like the groined vault. The groin of the groined vault is identical to the inner edge of the cloister dome. The arch section of the cloister dome is not seen on the side of the dome, but only the cross sections.
The Etruscans originated the arch (always semi-circular), the vault (an arched covering of stone), and the dome. The best preserved of the Etruscan arches is in the Porta all’Arco gateway at Volterra.

Adopted and developed extensively by the Romans, the arch, vault and dome played an important part in their architecture. The Romans combined the trabeated system (a style of architecture in which a structure is supported over openings by beams or lintels) of the Greeks with the arch, vault, and dome of the Etruscans, constructing buildings that were structurally more complex and ambitious than those of either. The result was arcuated structures (supported on arches), built on the pier and arch system. Orders (a column with the entablature its supports) were used, often with arches, to face these arcuated structures. This was not entirely to serve a decorative purpose for the orders were carefully placed and adapted so that they contributed to the scale and proportion of the whole design.
Vault
The evolution of the vault begins with the discovery of the arch, because the basic “barrel” form, which appeared first in ancient Egypt and the Near East, is simply a deep, or three-dimensional, arch. Since the barrel vault exerts thrust as the arch does, it must be buttressed along its entire length by heavy walls in which openings must be limited in size and number. This is a disadvantage, since it inhibits light and circulation.
But Roman builders discovered that openings could be made by building two barrel vaults that intersected at right angles to form the groin vault, which is square in plan and may be repeated in series to span rectangular areas of unlimited length. This vault has the additional advantage that its thrusts are concentrated at the four corners, so that the supporting walls need not

1. ARCHS , VAULTS AND DOMES
THEIR TYPES AND USES
SITE EXPOSURE AND YARD CONSTRUCTION
SUBMITTED BY - SUBMITTED TO -
ABDURRAB ANSARI ER.UMA PRASAD PANDEY

2. ARCH :
Anarchisacurvedstructuralformthatcarries
loadsaroundanopening,transferringthemaround
theprofileofthearchtoabutments,jambsorpiers
oneitherside.
Archesarecompressivestructures,thatis,there
arenotensilestresses.Theyareself-supporting,
stabilisedbytheforceofgravityactingontheir
weighttoholdthemincompression.Thismakes
themverystableandefficient,capableoflarger
spans,andsupportinggreaterloadsthanhorizontal
beams.

3. Thedownwardloadofanarchmustbetransferredtoitsfoundations.The
outwardthrustexertedbyanarchatitsbasemustberestrained,eitherbyitsown
weightortheweightofsupportingwalls,bybuttressingorfoundations,orbyan
opposingtiebetweenthetwosides.Theoutwardthrustincreasesastheheight,or
rise,ofthearchdecreases.
ARCH CONSTRUCTION -
❏Sincemanybuildingmaterials,suchasmasonryandconcrete,canresistcompression,archesare
commonlyconstructedusingthesetypesofmaterial.
❏Theconstructionoftraditionalmasonryarchesisdependentonthearrangementofthebricks,blocks
orstonesovertheopening.Wedge-shapedblocks,calledvoussoirs,aresetflank-to-flankwiththe
upperedgebeingwiderthantheloweredge.Downwardpressureonthearchhastheeffectofforcing
thevoussoirstogetherinsteadofapart.Thevoussoirthatispositionedinthecentreofthearchis
knownasthekeystone.

4. ❏This arrangement means that the arch is self-supporting, but temporary supports from below,
usually in the form of timber 'centres' (sometimes called 'centreing' or 'arch formers'), must be
provided until the keystone has been set in place.
❏The interior, lower curve of the arch is known as the intrados. The exterior, upper curve of the arch
is known as the extrados. The spring, or springing line, is the point from which the arch starts to rise
from its vertical supports.
TYPES OF ARCH -
Mostarchesarecircular,pointedorparabolic,however,thereareagreatmanyvariations
ofthesebasicformsthathavedevelopedduringdifferentperiods.AncientRomanarchitects
favouredroundedarches,whereasGothicarchitectspreferredpointedarchesandinthis
respectmayhavebeeninfluencedbyIslamicarchitecture.

5. Triangular arch-
Firstdevelopedbythe
Mayans,thetriangular
archisformedbytwo
largediagonalstonesthat
spananopeningby
mutuallysupportingeach
other.

6. Round arch-
Alsoknownasasemi-circular
arch,thisisformedinacontinuous
curveandwasdevelopedbythe
Romans.Theywereoftenusedside
bysideinaseriestocreatean
arcade.Anadaptationistherampant
roundarchwhichhasunequal
lengthsofsupportoneitherside.

7. Segmental arch-
Thisisanarchthathasarise
thatislessthanasemi-circle.Ina
flatterform,segmentalarches
werecommonlyusedforbridges
aslargerspansarepossible
withoutexcessivelyincreasing
height.Sincetheflatterthearch
getsthemorethrustisdelivered
sidewaystotheabutments,there
bridgesrequirelargeabutmentsat
eitherside.

8. Lancet arch-
Thiswasaformof
pointedarchthatwas
developedduringthe
Gothicperiod.Itwasoften
usedforwindowsandroof
structuresinchurchesand
cathedrals.Thearchistall
andnarrowwithapointed
apex.

9. Equilateral arch-
AlsofromtheGothicperiod,
equilateralarcheswereoftenused
fordecorativeentrancesand
windows.Thetwospringingpoints
andthecrownoftheintradosform
anequilateraltriangle,meaningthat
eachcurvehasachordlengthequal
tothespan.

10. Camber arch-
Alsoknownasajack
arch,acamberarchis
similartoalintelinthatit
isflat,oralmostflat,in
profile,however,the
voussoirsusetheir
compressivestrengthinthe
samewayasaregulararch.

11. Trefoil arch-
Thetrefoilarchwas
commonly usedin
religiousbuildings,and
incorporatedtheshapeof
threeoverlappingrings,
knownasatrefoil.

12. Horseshoe arch-
Thecurvesofthe
horseshoearchbulgeout
fromthespringingpoints
tocreateahorseshoe
profile.Theywerewidely
used in Islamic
architectureinregions
suchasSpainandNorth
Africa

13. Three-centred arch-
The three-centred
archissimilartothe
segmentalarchbuthas
morethantwocentres,
providingitwithan
ellipticalorovalprofile.

14. Four-centred arch-
Thefour-centredarch,
alsoknownasaTudor
archordepressedarch,is
lowandwidewitha
pointedapex.Itis
normallymuchwider
thanitsriseandwas
commonly usedin
Englisharchitecture.

15. Ogee arch-
Theogeearchformwas
developedduringthe
EnglishGothicperiodand
followsaconcavearcthat
flowsintoaconvexarc
withpointedcrown.Itwas
oftenusedfordecorative
purposesabovedoorways.

16. Parabolic and catenaryarch-
Aparabolicarchfollowsthe
principlethatwhenthereisa
uniformlyappliedloadfromabove,
theinternalcompressionthatresults
willfollowaparaboliccurve.
Parabolicarchesproducethemost
thrustatthebase,butcanspanthe
greatestdistance,andsoare
commonlyusedinbridgedesign.

17. A catenary arch looks very similar to a parabola, but is slightly more 'flat' at the bottom, and rises
faster than the parabola. The catenary is the solution to a differential equation that describes a shape that
directs the force of its own weight along its own curve, so that, if hanging, it is pulled into that shape, and
if standing upright it can support itself. The parabola does not have the same property, but is the solution
of other important equations that describe other situations.
*The Gateway Arch in St. Louis, Missouri, US (pictured above) is a catenary arch.

18. VAULT-
Anarchisacurvedstructuralformthatcarriesloadsaroundan
opening,transferringthemaroundtheprofileofthearchto
abutments,jambsorpiersoneitherside.Archarestructurallyvery
stableincompression,asloadsarerelativelyevenlybalanced
throughtheirform.
Avaultisastructuralformcomposedofaseriesofarches,
typicallyfoundintheconstructionofceilingsorroofs.
Theword'vault'mayalsobeusedtorefertoaroomorchamber
usedforstorage,inparticularifitisunderground,orsecure.

19. Vaultsmustbeabletowithstandtheoutwardpressureonthelowerpartsof
thevaultimposedbythestructureabove.Ifthevaultisunderground,thispressure
mightberesistedbythe‘fill’surroundingit.Ifitisaboveground,itcanberesisted
bythicksupportingwalls,supportingcolumns,buttresses,stiffeningdiaphragm
beams,sideanchorsorparallelwallsthatcandistributestress.
●The arrangement of arches relative to one another determines the type of
vault.

20. TYPE OF VAULT-
BARREL VAULT-
Abarrelvault(sometimesreferred
toasacradlevault,tunnelvault,or
wagonvault)isacontinuousarched
shapethatmayapproximateasemi-
cylinderinform,resemblingtheroof
ofatunnel,ormaybepointedatits
apex.Itistypicallyformedbyaseries
ofarchesplacedsidebyside(or
sometimesbyacontinuousshell).

21. Cloister vault-
Cloistervaults,also
knownasdomevaults,are
dome-shapedvaultsthat
maintainapolygonalshape
intheirhorizontalcross-
section.Theyarchtowards
thecentrefromaconstant
springpointalongawall.

22. Corbel vault-
Acorbelisanarchitecturalmemberthatprojectsoutfrom
awallandactsasatypeofbrackettocarryweight,suchas
thatimposedbyabalconyabove.
Corbel arches consist of two opposing sets of overlapping
corbels meeting at a peak, resembling an inverted staircase.
When these arches are formed in a series they are known as
a corbel vault. Both corbel arches and vaults were common
elements of Babylonian and Mayan architecture, where
curved structures had yet to be developed.

23. Rib vault-
Aribvaultisastructural‘skeleton’of
archesontowhichmasonrycanbelaid.
Thecrossed-archdomesisoneofthe
earliesttypesofribbedvault,formedwhere
theribs,insteadofmeetinginthedome’s
centre,areintertwinedtoformpolygons,
leavinganemptyspaceinthecentre.The
earliestknowncrossed-archdomeisin
Spain’sGreatMosqueofCordoba,dating
backtothe10thcentury

24. Groin vault-
Agroinvaultis
formedbytwobarrelvaults
intersectingatrightangles.
The‘groin’istheedge
betweentheintersecting
vaults.Aseriesofgroin
vaultscanbebuiltnextto
oneanothertocreatea
similareffecttoasimple
barrelvault.

25. Fan vault-
Afanvaultisformed
byaseriesofconcave
sectionsorribsthat
spreadoutfromaseries
ofspringpoints,
typicallyassociatedwith
Gothicarchitecture.

26. DOME-
Thedomehasalonghistoryinthebuiltenvironment,andhasbeenadesign
featureofmanydifferentkindsofarchitecturearoundtheworld.Domesare
prominentfeaturesofPersian,Roman,Byzantine,Islamic,andItalian
Renaissancedesign.
Initssimplestform,adomeisahollowsemi-sphericalstructuralelement.
However,therearemanyvariationsonthisbasicshape,andThe‘Building
ConstructionHandbook’describesdomesas:‘Doublecurvatureshellswhichcan
berotationallyformedbyanycurvedgeometricalplanefigurerotatingabouta
centralverticalaxis.’

27. Domesevolvedfromarches,originallybeingadaptedonlytosmallbuildings
suchashutsandtombs;however,asconstructionanddesigntechniques
developed,theybecamemorepopularasameansofshowcasinggrand
structuressuchascathedrals,legislativebuildingsand,morerecently,leisure
buildingssuchassportsstadia.
Intermsofsemiology,byreinforcingcentralityandsingularity,theformofthe
domerendersexplicittheprimacyofthecircleofspacedirectlybelow.
Inhistoricalterms,therepresentationalefficiencyofthedomehasmadeitpopular
amongthoseseekingtoreinforcethenotionofacentralisedandsingularpower
system,whetherabsolutemonarchy,monotheism,hegemonicdictatorship,fascism,
andsoon.

28. Some of the terminology that is often associated with domes include:
●Apex: The uppermost point of a dome (also known as the ‘crown’).
●Cupola: A small dome located on a roof or turret.
●Extrados: The outer curve of a dome.
●Haunch: Part of an arch that that lies roughly halfway between the base
and the top.
●Intrados: The inner curve of a dome.
●Springing: The point from which the dome rises.

29. TYPE OF DOME-
Corbel dome-
DatingbacktoPaleolithic
construction,thisisoneofthe
earliestdomeforms,alsoknown
asa‘beehivedome’.Theyare
notdomesinthestrictsense,as
theyareformedbyhorizontal
masonrylayersthatareslightly
cantilevereduntilmeetinginthe
centre.

30. Cloister vault-
Cloister vaults, also
known as dome vaults,
maintain a polygonal
shape in their horizontal
cross-section. They arch
towards the centre from a
constant spring point
along a wall.

31. Crossed-arch dome-
Thisisoneofthe
earliesttypeofribbedvault
wheretheribs,insteadof
meetinginthedome’s
centre,areintertwinedto
formpolygons,leavingan
emptyspaceinthecentre.
Theearliestknownexample
isinSpain’sGreatMosque
ofCordoba,datingbackto
the10thcentury.

32. Geodesic dome-
Geodesicdomesaresphere-
likestructuresconsistingofa
networkoftriangleswhich
provideaself-balancingstructural
frameworkwhilstusingminimal
materials.Theyweredeveloped
bytheAmericanengineerand
architectBuckminsterFullerin
thelate1940s.

33. Monolithic dome-
Thisisadomestructure
thatiscastinaone-piece.
Amonolithicdomeisathin-
shellstructurecastinaone-
pieceform.Theformmaybe
permanentortemporaryand
mayormaynotremainpartof
the finishedstructure.
Monolithicdomesareaform
ofmonolithicarchitecture.

34. Onion dome-
These domes are
characterisedbythewaythey
bulgeoutbeyondtheirbase
diametersandtapersmoothlyin
anogee(S-curve)profile.Their
heightusuallyexceedstheir
widthandtheyareoftengilded
orbrightlypainted.Theseare
traditionallyassociatedwith
Russianarchitecture,in
particulartheirmulti-domed
churches.Formoreinformation,
seeSt.Basil’sCathedral.

35. Oval dome-
Anovaldomemaybe
definedasadomewhose
planorprofile(orboth)
hasanovalform.The
geometryisdefinedas
usingcombinationsof
circulararcsthat
transitionattangential
points.

36. Rotational dome-
Alsoknownas
‘hemisphericaldomes’,
theseareonehalfof
asphere,constructed
onacircularring
beam.

37. Saucer dome-
Intermsofareathese
areoftensomeofthe
largestdomes,andare
shallowerinprofilethan
otherformsofdome.

38. Umbrella dome-
Alsoknownasa
‘ribbed’,‘parachute’or
‘scalloped’dome.These
aredividedintocurved
segmentsthatfollowthe
elevation’scurve.Radial
linesofstructurethatactas
thedome’s‘ribs’extend
downthespringingfrom
theapex.

39. Cablenet dome-
Whilstnotconventional
domesinthattheyarenot
compressionstructures,but
tensionstructures,cablenet
structurescanadoptanoverall
domedshape,albeitindividual
sectionsaregenerallyflator
anticlasticinform(ratherthan
thesynclasticformof
compressiondomes).The
MillenniumDomeinLondonis
acablenetdomestructure,and
at320mindiameter,isoneof
thelargestdomesintheworld.

40. Inflated domes-
Inflatedstructuresare
formedbypressurisinga
volumeofairenclosedbya
lightweightfabricmembrane.
Inflatedstructurescanadopta
domedshape,andare
typicallyusedforspaces
requiringalargeenclosure
uninterruptedbycolumns,
suchasradomes,warehouses,
sportingfacilities,stadiaand
soon.

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