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7.4TheMedieval Period (477-1492) 137
Figure7.5:HagiaSophia
dieval masons'e ortsto solve theproblemsassociatedwithsupportingheavymasonryceiling
vaultsover widespans. Theproblemwas thattheheavystoneworkof thetraditionalarched
barrelvaultandthegroinvaultexerteda tremendousdownwardandoutwardpressurethat
tendedto pushthewallsuponwhich thevaultrestedoutward,thus collapsingthem.A build-
ing'sverticalsupportingwalls thushadtobe madeextremelythick andheavyin orderto
containthebarrelvault'soutwardthrust.
Medieval masonssolvedthisdicultproblemabout 1120 witha number of brilliant inno-
vations. Firstandforemosttheydevelopeda ribbedvault,in which archingandintersecting
stoneribssupporta vaultedceilingsurfacethatis composedof merethinstonepanels. This
greatlyreducedtheweight (andthustheoutwardthrust)of theceilingvault,andsincethe
vault'sweight was now carriedat discretepoints (theribs)ratherthanalonga continuouswall
edge,separatewidelyspacedverticalpiersto supporttheribscould replacethecontinuous
thick walls. Theroundarchesof thebarrelvaultwerereplacedby pointed(Gothic)arches
which distributedthrustin moredirectionsdownwardfromthetopmostpoint of thearch.
Sincethecombinationof ribsandpiersrelieved theinterveningverticalwallspacesof their
supportive function,thesewallscouldbe builtthinnerandcouldeven be openedupwithlarge
windowsor otherglazing. A crucialpoint was thattheoutwardthrustof theribbedceiling
vaultswas carriedacrosstheoutsidewallsof thenave, rstto anattachedouterbuttressand
thento a freestandingpierby meansof a halfarch knownas a
yingbuttress. The
ying
buttressleanedagainsttheupper exteriorof thenave (thus counteractingthevault'soutward
thrust),crossedover thelow sideaislesof thenave, andterminatedin thefreestandingbuttress
pier,which ultimatelyabsorbedtheceilingvault'sthrust.
Theseelements enabledGothicmasonsto buildmuch largerandtallerbuildingsthantheir
Romanesquepredecessorsandto give theirstructuresmorecomplicatedgroundplans. The
skillfuluseof
yingbuttressesmadeit possibleto buildextremelytall,thin-walledbuildings
whoseinteriorstructuralsystemof columnarpiersandribsreinforcedanimpressionof soaring
verticality.
19 Vilet-Le-Ducclassicalbook,(leDuc1977)providedan in depthstudyof Gothicarchitecture.