Among the most interesting domes structurally and architecturally are those shown in the accompanying table. The size of a dome can be measured by the span of its base, and this measurement has been rounded off in the table. What is remarkable is that the oldest of these domes is also the largest. The 2nd-century Pantheon that stands in Rome today was a brick-faced concrete replacement for a temple that was destroyed by fire. The Pantheon’s spherical dome with the famous oculus at its apex rests on a circular drum structure that forms the building’s main vertical enclosure. Although there are many penetrations of and alcoves in the drum’s wall, its general 20-foot thickness provides morethan-ample strength to support the dome and resist its outward thrust.
Pantheon, Rome
location Regione IX Circus Flaminius
year 126 AD
patron Publius Aelius Hadrianus
type of structure Roman temple
related Marcus Vipsanius Agrippa, Hadrian, Apollodorus of Damascus
Pantheon History No other single building has capFor many historians, the Pantheon
represents
a
kind
of
culmination of the “Roman architectural revolution” brought to fruition during the course of the first century through the adoption of high-quality concrete that could be more readily used for the construction of curvilinear architectural forms. Unlike simple lime mortar, which is produced by adding water to a mixture of quicklime and sand, and sets when all the water has been evaporated
tured the attention of architects, particularly since the Renaissance, as has the Pantheon. Constructed between ca. 118 and 128, it has an interior space of awesome scale, and it is the most completely preserved building of the Imperial Roman capital. The 43.4-meter clear span of the dome was un-matched for well over a millennum, and not substantially surpassed until the adoption of steel and reinforced concrete in the modern era. The enormous influence of the Pantheon is easily traced through numerous buildings from the later Roman period, and again from the beginning of the Renaissance well into the twentieth century. Earlier prototypes, though, are not so readily identified. Domed buildings were not uncommon before the time of the Pantheon, but we know of none that even approached its scale. The largest of the earlier, extant domes seems to have been part of a bath complex at Baiae. Dating
into the atmosphere or absorbed into the surrounding masonry. Roman pozzolana (after Pozzuoli, where it was first diseovered) sets by eombining ehemieally with water in the same way as modern Portland eement. These eements do not need to dry out as does lime mortar; in faet they are "hydraulie" in that they will set even when immersed. In addition to the obvious advantage for underwater eonstruetion, large batehes of pozzolana eement will eure relatively rapidly, even in damp eonditions. It eould thus be used for the massive, primary struetural elements of large buildings. Furthermore, the early eompressive strength of pozzolana eement is far superior to that of lime mortar. Nonetheless, one must be eautious in eharaeterizing the resistance of eonerete to eraeking eaused by tension forées tending to pull it apart. Although modem concrete based on eontrolled-eured, high-quality Portland eement exhibits measurable tensile strength (the level of stress causing a material to fail in tension), its tensile strength is taken to be nil in reinforeed eonerete design. Experience has dietated that reinforeing steel is always required in regions of a strueture where ealeulations indieate that tension will be present. Even more important, in view of our later diseussion of the state of the Pantheon fabrie, it is also required where temperature changes are likely to be encountered.
Since the time of its construction, the bold, brilliantly
The dome itself
simple schema of Hadrian's Pantheon
is supported by
has inspired much emulation, commendation, and even fear. Modern commentators tend to view the building as a high point in an “architectural revolution” brought about mainly through the Roman development of a superior poz-
lightening of the dome by coffering and gradated, light-weight aggregates. To investigate these theories, and thereby to understand late Roman design rationale better, a numerical computer modeling study of the dome structure was undertaken. It yielded several surprises. Analysis revealed that the stepped rings induced higher, rather than lower, critical stresses in an uncracked dome model. But by allow-
features of the
ing the model to crack freely, a salutary
Pantheon is the
effect was caused by the rings. The
Architecture. The
cracked model closely simulated the
structure of
behavior of the actual dome, which
the Pantheon is
was discerned to act structurally as an
arches. The arches rest on eight piers which support eight round-headed arches which run through the drum from its innerto its outer face. The arches correspond to the eight bays on the floor level that house statues.
sustain the weight of their magnani-
on include the use of a series of mas-
series of intersecting
which helped
mous buildings.
sive, concentric stepped rings and the
comprised of a
had perfected the use of arches
forming of unitary, three-dimensional structures. Other factors cited for
most fascinating
round. Romans
zolana concrete that lent itself to the
the technical success of the Panthe-
Probably one of the
a series of arches that run horizontally
array of arches. In fact, the configuration of the dome seems to indicate that the builders understood this — which points to the conclusion that late Roman architectural development was not so closely tied to structural innovation as has been generally believed.
Soon after Hadrian became emperor, work began on the Pantheon, the temple of all the gods, one of the bestpreserved buildings of antiquity and most influential designs in architectural history. The Pantheon reveals the full potential of concrete, both as a building material and as a means for shaping architectural space. Originally, visitors approached the Pathon from a columnar courtyard, and the temple itself, like temples in Roman forums, stood at one narrow end of the enclosure. Its facade of eight Corinthian columns—almost all that could be seen from ground level in antiquity—was a bow to tradition. Everything else about the Pantheon was revolutionary. Behind the columnar porch is an immense concrete cylinder covered by a huge hemispherical dome 142 feet in diameter. If the Pantheon’s design is simplicity itself, executing that design required all the ingenuity of Hadrian’s engineers. They built up the cylindrical drum level by level using concrete of varied composition. Extremely hard and durable basalt went into the mix for the foundations, and the builders gradually modified the “recipe” until, at the top, featherweight pumice replaced stones to lighten the load. Below the dome, much of the original marble veneer of the walls, niches, and floor has survived. In the Pantheon, visitors can get a sense, as almost nowhere else, of how magnificent the interiors of Roman concrete buildings could be. But despite the luxurious skin of the Pantheon's interior, the sense experienced on first entering the structure is not the weight of the enclosing walls but the space they enclose. In pre-Roman architecture, the form of the enclosed space was determined by the placement of the solids, which did not so much shape space as interrupt it. Roman architects were the first to conceive of architecture in terms of units of space that could be shaped by the enclosures. The Pantheon's interior is a single unified, self-sufficient whole, uninterrupted by supporting solids. It encloses visitors without imprisoning them. opening through the oculus to the drifting clouds, the blue sky, the sun, and the gods. In this space, the architect used light not merely to illuminate the darkness but to create drama and underscore the interior shape's symbolism. On a sunny day as the sun moves across the sky itself. Escaping from the noise and torrid heat of a Roman summer day into the Pantheon's cool, calm, and mystical immensity is an experience alsmost impossible to describe and one that should not be missed.
pantheon patterns
Modeling the Pantheon
Analysis of the Pantheon structure was carried out using a
A second simphfication made for the modeled, typical
three-dimensional, numerical-computer (finite-element)
building section concerns the structural effect of the dome
modeling code developed by Jean-Hervé Prévost at Princ-
coffering. The coffering, which forms a waffle pattern begin-
eton University.« In this approach, the configuration of
ning just above the springing and ending several meters from
a building structure is described by a series of coordinates
the oculus, is actually relatively shallow compared to the full
taken at finite intervals. These coordinates define a mesh
dome thickness, which is taken to be uniform at 1.5 meters
that becomes the geometric model for the computer. A
above the stepped rings. A volumetric analysis indicated
series of equations related to loading conditions and the
that less than five percent of the total dome weight is taken
properties of the building materials are then used to cal-
out by the coffering. And since it decreases the stiffness of
culate the displacements of all the mesh points in order to
the dome to only a small degree, the coffering effect could
obtain an overall deflection pattern for the model. Through
be neglected in the finite-element model. Another consid-
equations of elasticity, the deflection pattern then gives
eration, evident from the building plan, is that the porch
information about the distribution of structural forces
plays no role in the supporting structure of the dome. The
throughout the building.
porch is in fact hardly connected to the rotunda. The base
To simplify the analysis, a typical meridional section for the
in the cylindrical wall—fully one-quarter of its volume is taken out by statue bays, passageways, and other voidsno typical section actually exists (see Figs. 3 and 4). But since our interest is centered on the functioning of the dome and the conceptual design of the basic structural configuration, we need not here deal in detail with the walL’ In fact, it is possible to design a solid wall that provides support to the dome which is similar to that provided by the actual, voided wall. It was determined that a 5.5-meterthick, solid cylindrical wall provides the same overall structural stiffness as the six-meter-thick actual wall; and this equivalent wall was used
dations, that is, held rigidly against all displacements. The dome itself is assumed to have been erected on timber centering so that, in effect, dome forces were "turned on" all at once with the removal of the centering. Most important, for the first series of model tests, tensile stresses throughout are assumed to be of low enough magnitude so that the structural fabric of the building remains integral; that is, cracking is nowhere permitted.i° Finally, dimensions and data on the gradation of materials used in the construction were those reported by K. de Fine Licht." The density of the brick-faced concrete used in the cylindrical wall is taken to be 1750 kg/m. This value is reduced to 1600 kg/m in the lower region of the dome, and to 1350 kg/m^ for the upper region of the dome (compared with the 2200 kg/m^ density of the concrete used in the Pantheon foundations, which is also the density of standard modern concrete).
Philadelphia, 1973, 46).
Construction in Italy from
Nerva through the Antonines,
theories of [internalribbed]
dome construction" (Roman
tastic but utterly erroneous
arches that led to so many fan-
throughout the analysis. dome. It was these relieving
too strongly that the framework of the arches . . . was part of [the] wall construction and
structure was specified. Because of the extensive openings
did not follow the curve of the
Blake and D. Taylor- Bishop draw attention to the fact that "it cannot be emphasized
relieving arches, is complex and has received much attention in the literature (see, e.g.,
MacDonald, 1982, 106ff.). But this construction is not carried into the dome. M.E.
The actual structure of the wall, which incorporates as well a large number of great
three-dimensional finite-element model of the Pantheon
of the rotunda is assumed to be fixed to perfectly rigid foun-
0 50 75 100 feet
0 15 30 meters
Lateral section of the Pantheon, Rome, Italy, 118-125CE
structural analysis techniques, was aimed at evaluating these theories, and thereby gaining some new insight into ancient techniques of largescale building.
of the great vault and function as buttresses, helping to bring the
structure into stability through compression."' Indeed, the reproduc-
tion of the rings on many of the Pantheon derivatives would seem to
imply that later designers shared in this view. A final, usual observation
building, whose density is significantly less than that of the lower, supporting structure. Our investigation of the dome, based on modern
arrayed about the outer surface of the dome." According to W.L. Mac-
use of a new structural device, the series of concentric stepped rings
Donald, "the rings add to the load over the critical or haunch portion
is that the designer aimed for lightness by coffering the underside of the dome and using a lightweight aggregate in the upper reaches of the
Another reason given for the success of the Pantheon dome was the
Behind the columnar porch is an immense concrete cylinder covered by a huge hemispherical dome 142 feet in diameter. The dome’s top is also 142 feet from the floor. The design is thus based on the intersection of two circles (one horizontal, the other vertical).
PO
LY GO
N
_Hagia Sophia
AL DOME
_Location: Istanbul (Constantinople) Turkey _Designer Isidore of Miletus Anthemius of Tralles _Type Eastern Orthodox Cathedral (537–1204) Roman Catholic Cathedral (1204–1261) Eastern Orthodox Cathedral (1261–1453) Imperial Mosque (1453–1931) Museum (1935–present) _Material Ashlar, brick _Length: 82 m (269 ft) _Width: 73 m (240 ft) _Height: 55 m (180 ft) _Beginning date: 532
The Church was dedicated to the Wisdom of God, the Logos, the second person of the Holy Trinity,its patronal feast taking place on 25 December, the commemoration of the Birth of the incarnation of the Logos in Christ.[3] Although sometimes referred to as Sancta Sophia (as though it were named after Saint Sophia), sophia being the phonetic spelling in Latin of the Greek word for wisdom, its full name in Greek means “Shrine of the Holy Wisdom of God”.] Famous in particular for its massive dome, it is considered the epitome of Byzantine architectureand is said to have “changed the history of architecture.”It remained the world’s largest cathedral for nearly a thousand years thereafter, until Seville Cathedral was completed in 1520. The current building was originally constructed as a church between 532 and 537 on the orders of the Byzantine Emperor Justinian and was the third Church of the Holy Wisdom to occupy the site, the previous two having both been destroyed by rioters. It was designed by the Greek scientists Isidore of Miletus, a physicist, and Anthemius of Tralles,
a mathematician.
The most important monument of Early Byzantine art is Hagia Sophia, the Church of Holy Wisdom, in Constantinople. Anthemius of Tralles and Isidorus Of Miletus, a mathematician and a physicist—neither man an architect in the modern sense of the word—designed and built the church for Justinian between 532 and 537. They began work immediately after fire destroyed an earlier church on the site during the Nika riot in January 532. Justinian intended the new church to rival all other churches ever built and even to surpass in scale and magnificence the Temple of Solomon in Jerusalem. The result was Byzantium’s grandest
Hagia Sophia
building and one of the supreme accomplishments of world architecture. Hagia Sophia’s dimensions are formidable for any structure not built of steel. In plan, it is about 279 feet long and 240 feet wide. The dome is 108 feet in diameter, and its crown rises some 180 feet above the pavement. (The first dome collapsed in 559. It replacement required repair in the 9th and 14th centuries. The present dome is greater in height and more stable than the original.) In scale, Hagia Sophia revals the architectural wonders of Rome: the Pantheon, the Baths of Caracalla, and the Basilica of Constantine. In exterior view, the great dome dominated the structure, but the building’s present external aspects are much changed from their original appearance. Huge buttresses were added to the Justinianic design, and after the Ottoman conquest of 1453m when Hagia Sophia became a mosque, the Turks constructed four towering minarets. The building, secularized in the 20th century is now a museum.
Who… shall sing the marble meadows gathered upon the mighty walls and spreading pavement… [There is stone] from the green flanks of Carystus [and] the speckled Phrygian stone, sometimes rosy mixed with white, sometimes gleaming with purple and silver flowers. There is a wealth of porphyry stone, too, besprinkled with little bright stars… You may see the bright green stone of Laconia and the glittering marble with sawy veins found in the deep gullies of the Iasian peaks, exhibiting slanting streaks of bloodred and livid white; the pale yellow with swirling red from the Lydian headland; the glittering crocus-like golden stone [of Libya]; … glittering [Celtic] black [with] here and there an abundance of milk; the pale onyx with glint of precious metal; and [Thessalian marble] in parts vivid green not unlike emerald… It has spots resembling snow next to flashes of black so that in one stone various beauties mingle. The characteristic Byzantine plainness and unpretentiousness of the exterior (which in this case also disguise the massive scale) scarcely prepare visitors for the building’s interior. A poet and member of Justinian’s court, Paul the Silentiary (an usher responsible for maintaining silence in the palace), vividly described the original magnificence of Hagia Sophia’s interior:
The feature that distinguishes Hagia Sophia from equally
and described the vaulting as covered with “gilded tesserae
lavishly revetted Roman buildings such as the Pantheon is
from which a glittering stream of golden rays pours abun-
the special mystical quality of the light flooding the interi-
dantly and strikes men’s eyes with irresistible force. It is
or. The soaring canopy-like dome that dominates the inside
as if one were gazing at the midday sun in spring.”3 Thus,
as well as the outside of the church rides on a halo of light
Hagia Sophia has a vastness of space shot through with
from windows in the dome’s base. Visitors to Hagia Sophia
light, and a central dome that appears to be supported by
from Justinian’s time to today have been struck by the light
the light it admits. Light is the mystic element—light that
within the church and its effect on the human spirit. The
glitters in the mosaics, shines forth from the marbles, and
40 windows at the base of the dome create the illusion the
pervades and defines spaces that escape definition. Light
dome rests on the light pouring through them.
seems to dissolve material substance and transform it into
Procopius observed that the dome looked as if it were
an abstract spiritual vision. Pseudo-Dionysius, perhaps
suspended by “a golden chain from Heaven” and that “the
the most influential mystic philosopher of the age, wrote
space is not illuminated by the sun from the outside, but
in The Divine Names: “Light comes from the Good and .
that the radiance is generated within, so great an abundance
. . light is the visual image of God.” “Light comes from the
of light bathes this shrine all around.”2 Paul the Silentiary
Good and . . . light is the visual image of God.”
compared the dome to “the firmament which rests on air”
“Light comes from the Good and . . . light is the visual image of God.”
pendentives
To achieve this illusion of a floating “dome of Heaven,” The diverse vistas and screenlike ornamented surfaces
Anthemius and Isidorus used pendentives (see “Pendentives
mask the structural lines. The columnar arcades of the nave
and Squinches,” above) to transfer the weight from the great
and secondstory galleries have no real structural function.
dome to the piers beneath rather than to the walls. With
Like the walls they pierce, they are only part of a fragile “fill”
pendentives, not only could the space beneath the dome
between the huge piers. Structurally, although Hagia Sophia
be unobstructed but scores of windows also could puncture
may seem Roman in its great scale and majesty, the organi-
the walls. The pendentives created the impression of a dome
zation of its masses is not Roman. The very fact the “walls”
suspended above, not held up by, walls. Experts today can
in Hagia Sophia are concealed (and barely adequate) piers
explain the technical virtuosity of Justinian’s builders, but
indicates the architects sought Roman monumentality as an
it remained a mystery to their contemporaries. Procopi-
effect and did not design the building according to Roman
us communicated the sense of wonderment experienced
principles. Using brick in place of concrete was a further
by those who entered Justinian’s great church: “No matter
departure from Roman practice and marks Byzantine archi-
how much they concentrate their attention on this and that,
tecture as a distinctive structural style. Hagia Sophia’s eight
and examine everything with contracted eyebrows, they are
great supporting piers are ashlar masonry, but the screen
unable to understand the craftsmanship and always depart
walls are brick, as are the vaults of the aisles and galleries
fromthere amazed by the perplexing spectacle.”
and the dome and semicircular half-domes.
By placing a hemispherical dome on a square base instead
The ingenious design of Hagia Sophia provided the illumi-
of on a circular base, as in the Pantheon, Anthemius and
nation and the setting for the solemn liturgy of the Ortho-
Isidorus succeeded in fusing two previously independent
dox faith. The large windows along the rim of the great dome
and seemingly mutually exclusive architectural traditions:
poured light down upon the interior’s jeweled splendor,
the vertically oriented central-plan building and the lon- where priests staged the sacred spectacle. Sung by clerical gitudinally oriented basilica. Hagia Sophia is, in essence, a
choirs, the Orthodox equivalent of the Latin Mass celebrat-
domed basilica— a uniquely successful conclusion to several
ed the sacrament of the Eucharist at the altar in the apsi-
centuries of experimentation in Christian church architec-
dal sanctuary, in spiritual reenactment of Jesus’ crucifixion.
ture. However, the thrusts of the pendentive construction at
Processions of chanting priests, accompanying the patri-
Hagia Sophia made external buttresses necessary, as well as
arch (archbishop) of Constantinople, moved slowly to and
huge internal northern and southern wall piers and eastern
from the sanctuary and the vast nave. The gorgeous array of
and western half-domes. The semidomes’ thrusts descend,
their vestments rivaled the interior’s polychrome marbles,
in turn, into still smaller half-domes surmounting columned
complementing the interior’s finely wrought, gleaming
exedrae that give a curving flow to the design.
candlesticks and candelabra; the illuminated books bound in gold or ivory and inlaid with jewels and enamels; and the crosses, sacred vessels, and processional banners. Each, with its great richness of texture and color, glowing in shafts of light from the dome, contributed to the majestic ambience of Justinian’s great church. The nave of Hagia Sophia was reserved for the clergy, not the congregation. The laity, segregated by sex, had only partial views of the brilliant ceremony from the shadows of the aisles and galleries, restrained in most places by marble parapets. The emperor was the only layperson privileged to enter the sanctuary. When he participated with the patriarch in the liturgical drama, standing at the pulpit beneath the great dome, his rule was again sanctified and his person exalted. Church and state were symbolically made one. The church building was then the earthly image of the court of Heaven, its light the image of God and God’s holy wisdom. At Hagia Sophia, the intricate logic of Greek theology, the ambitious scale of Rome, the vaulting tradition of Mesopotamia, and the mysticism of Eastern Christianity combined to create a monument that is at once a summation of antiquity and a positive assertion of the triumph of Christian faith.
dral dedicated to Saint Reparata. According to Bartlett, the cojonied by Arnolfo di Cambio and approved by city council in 1294. Arnolfo di Cambio was also architect of the church of Santa Croce and the Palazzo Vecchio. He designed three wide naves ending under the octagonal dome, with the middle nave covering the area of Santa Reparata. The first stone was laid on September 9, 1296 by Cardinal Valeriana, the first papal legate ever sent to Florence. The building of this vast project was to last 140 years, the collective efforts of several generations; Arnolfo’s plan for the eastern end, although maintained in concept, was greatly expanded in size. The Duomo, as if completed, in a fresco by Andrea di Bonaiuto, painted in the 1360s, before the commencement of the dome. After Arnolfo died in 1302, work on the cathedral slowed for the following thirty years. When the relics of Saint Zenobius were discovered in 1330 in Santa Reparata, the project obtained new impetus. In 1331, the Arte della Lana, the guild of wool merchants, took over exclusive patronage for the construction of the cathedral and in 1334 appointed Giotto to oversee the work. Assisted by Andrea Pisano, Giotto continued di Cambio’s design. His major accomplishment was the building of the campanile. When Giotto died in 1337, Andrea Pisano continued the building until work was again
ment of the dome.
in the 1360s, before the commence-
fresco by Andrea di Bonaiuto, painted
3.2 The Duomo, as if completed, in a
during the 18th century.
halted due to the Black Death in 1348.
3.1 Procession outside the cathedral
History of Florence Cathedral
Santa Maria del Fiore was built on the site of an earlier cathe-
In 1349 work resumed on the cathedral under a series of
Work started on the dome in 1420 and was completed in
architects, commencing with Francesco Talenti, who fin-
1436. The cathedral was consecrated by Pope Eugene IV on
ished the campanile and enlarged the overall project to
March 25, 1436 (the first day of the year according to the Flo-
include the apse and the side chapels. In 1359 Talenti was suc-
rentine calendar). It was the first ‘octagonal’ dome in history
ceeded by Giovanni di Lapo Ghini (1360–1369) who divided
to be built without a temporary wooden supporting frame:
the center nave in four square bays. Other architects were
the Roman Pantheon, a circular dome, was built in 117–128
Alberto Arnoldi, Giovanni d’Ambrogio, Neri di Fioravante
AD with support structures. It was one of the most impres-
and Andrea Orcagna. By 1375 the old church Santa Reparata
sive projects of the Renaissance. During the consecration
was pulled down. The nave was finished by 1380, and by 1418
service in 1436, Guillaume Dufay’s similarly unique motet
only the dome remained incomplete.
Nuper rosarum flores was performed. The structure of this
On 18 August 1418, the Arte della Lana announced a struc-
motet was strongly influenced by the structure of the dome.
tural design competition for erecting Neri’s dome. The two
The decoration of the exterior of the cathedral, begun in
main competitors were two master goldsmiths, Lorenzo
the 14th century, was not completed until 1887, when the
Ghiberti and Filippo Brunelleschi, who was supported by
polychrome marble façade was completed to the design of
Cosimo de Medici. Ghiberti had been winner of a compe-
Emilio De Fabris. The floor of the church was relaid in mar-
tition for a pair of bronze doors for the Baptistery in 1401
ble tiles in the 16th century.
and lifelong competition between the two remained acute. Brunelleschi won and received the commission.
The exterior walls are faced in alternate vertical and horizontal bands of polychrome marble from Carrara (white),
Ghiberti, appointed coadjutator, was drawing a salary equal
Prato (green), Siena (red), Lavenza and a few other places.
to Brunelleschi’s and, though neither was awarded the
These marble bands had to repeat the already existing bands
announced prize of 200 florins, would potentially earn equal
on the walls of the earlier adjacent baptistery the Battistero
credit, while spending most of his time on other projects.
di San Giovanni and Giotto’s Bell Tower. There are two lat-
When Brunelleschi became ill, or feigned illness, the proj-
eral doors, the Doors of the Canonici (south side) and the
ect was briefly in the hands of Ghiberti. But Ghiberti soon
Door of the Mandorla (north side) with sculptures by Nanni
had to admit that the whole project was beyond him. In 1423
di Banco, Donatello, and Jacopo della Quercia. The six lat-
Brunelleschi was back in charge and took over sole respon-
eral windows, notable for their delicate tracery and orna-
sibility.
ments, are separated by pilasters. Only the four windows closest to the transept admit light; the other two are merely ornamental. The clerestory windows are round, a common feature in Italian Gothic. During its long history, this cathedral has been the seat of the Council of Florence (1439), heard the preachings of Girolamo Savonarola and witnessed the murder of Giuliano di Piero de’ Medici on Sunday, 26 April 1478 (with Lorenzo Il Magnifico barely escaping death) in the Pazzi conspiracy. 3.2
3.1
structure & plan The cathedral of Florence is built as a basilica, having a wide central nave of four square bays, with an aisle on either side. The chancel and transepts are of identical polygonal plan, separated by two smaller polygonal chapels. The whole plan forms a Latin cross. The nave and aisles are separated by wide pointed Gothic arches resting on composite piers. The dimensions of the building are enormous: length 153 metres (502 ft), width 38 metres (124 ft), width at the crossing 90 metres (295 ft). The height of the arches in the aisles is 23 metres (75 ft). The height of the dome is 114.5 m.
By the beginning of the 15th century, after a hundred years of construction, the structure was still missing its dome. The basic features of the dome had been designed by Arnolfo di Cambio in 1296. His brick model, 4.6 metres (15 ft) high 9.2 metres (30 ft) long, was standing in a side aisle of the unfinished building, and had long ago become sacrosanct.[5] It called for an octagonal dome higher and wider than any that had ever been built, with no external buttresses to keep it from spreading and falling under its own weight.
dome
The commitment to reject traditional Gothic buttresses had been made when Neri di Fioravante’s model was chosen over a competing one by Giovanni di Lapo Ghini.That architectural choice, in 1367, was one of the first events of the Italian Renaissance, marking a break with the Medieval Gothic style and a return to the classic Mediterranean dome. Italian architects regarded Gothic flying buttresses as ugly makeshifts and since the use of buttresses was forbidden in Florence, in addition to being a style favored by central Italy’s traditional enemies to the north.[8] Neri’s model depicted a massive inner dome, open at the top to admit light, like Rome’s Pantheon, but enclosed in a thinner outer shell, partly supported by the inner dome, to keep out the weather. It was to stand on an unbuttressed octagonal drum. Neri’s dome would need an internal defense against spreading (hoop stress), but none had yet been designed.
The building of such a masonry dome posed many technical problems. Brunelleschi looked to the great dome of the Pantheon in Rome for solutions. The dome of the Pantheon is a single shell of concrete, the formula for which had long since been forgotten. A wooden form had held the Pantheon dome aloft while its concrete set, but for the height and breadth of the dome designed by Neri, starting 52 metres (171 ft) above the floor and spanning 44 metres (144 ft), there was not enough timber in Tuscany to build the scaffolding and forms.[9] Brunelleschi chose to follow such design and employed a double shell, made of sandstone and marble. Brunelleschi would have to build the dome out of bricks, due to its light weight compared to stone and easier to form, and with nothing under it during construction. To illustrate his proposed structural plan, he constructed a wooden and brick model with the help of Donatello and Nanni di Banco which is still displayed in the Museo dell’Opera del Duomo. The model served as a guide for the craftsmen, but was intentionally incomplete, so as to ensure Brunelleschi’s control over the construction. Brunelleschi’s solutions were ingenious. The spreading problem was solved by a set of four internal horizontal stone and iron chains, serving as barrel hoops, embedded within the inner dome: one each at the top and bottom, with the remaining two evenly spaced between them. A fifth chain, Length
Width
Crossing Width
153m 38m
Arch Height
90m
Dome Height
23m 114.5m
made of wood, was placed between the first and second of the stone chains. Since the dome was octagonal rather than round, a simple chain, squeezing the dome like a barrel hoop, would have put all its pressure on the eight corners of the dome. The chains needed to be rigid octagons, stiff enough to hold their shape, so as not to deform the dome as they held it together.
Each of Brunelleschi’s stone chains was built like an octagonal railroad track with parallel rails and cross ties, all made of sandstone beams 43 centimetres (17 in) in diameter and no more than 2.3 metres (7.5 ft) long. The rails were connected end-to-end with lead-glazed iron splices. The cross ties and rails were notched together and then covered with the bricks and mortar of the inner dome. The cross ties of the bottom chain can be seen protruding from the drum at the base of the dome. The others are hidden. Each stone chain was supposed to be reinforced with a standard iron chain made of interlocking links, but a magnetic survey conducted in the 1970s failed to detect any evidence of iron chains, which if they exist are deeply embedded in the thick masonry walls. He was also able to accomplish this by setting vertical “ribs� on the corners of the octagon curving towards the center point. The Ribs, 13 feet (4 meters) deep, are supported by 16 concealed ribs radiating from center.[10] The ribs had slits to take beams that supported platforms, thus allowing the work to progress upward without the need for scaffolding.
3.3
A circular masonry dome, such as
A modern understanding of physi-
The commission for this bronze ball
that of Hagia Sophia in Istanbul can
cal laws and the mathematical tools
[atop the lantern] went to the sculptor
be built without supports, called cen-
for calculating stresses was centuries
Andrea del Verrocchio, in whose work-
tering, because each course of bricks
into the future. Brunelleschi, like all
shop there was at this time a young
is a horizontal arch that resists com-
cathedral builders, had to rely on intu-
apprentice named Leonardo da Vinci.
pression. In Florence, the octagonal
ition and whatever he could learn from
Fascinated by Filippo’s [Brunelleschi’s]
inner dome was thick enough for an
the large scale models he built. To lift
machines, which Verrocchio used to
imaginary circle to be embedded in it
37,000 tons of material, including over
hoist the ball, Leonardo made a series
at each level, a feature that would hold
4 million bricks, he invented hoisting
of sketches of them and, as a result, is
the dome up eventually, but could not
machines and lewissons for hoisting
often given credit for their invention.
hold the bricks in place while the mor-
large stones. These specially designed
Leonardo might have also participat-
tar was still wet. Brunelleschi used a
machines and his structural innova-
ed in the design of the bronze ball, as
herringbone brick pattern to transfer
tions were Brunelleschi’s chief contri-
stated in the G manuscript of Paris
the weight of the freshly laid bricks to
bution to architecture. Although he
“Remember the way we soldered the
the nearest vertical ribs of the non-cir-
was executing an aesthetic plan made
ball of Santa Maria del Fiore”.
cular dome.
half a century earlier, it is his name,
The decorations of the drum gallery by
The outer dome was not thick enough
rather than Neri’s, that is commonly
Baccio d’Agnolo were never finished
to contain embedded horizontal cir-
associated with the dome.
after being disapproved by no one less
cles, being only 60 centimetres (2 ft)
Brunelleschi’s ability to crown the
than Michelangelo.
thick at the base and 30 centimetres (1
dome with a lantern was questioned
A huge statue of Brunelleschi now sits
ft) thick at the top. To create such cir-
and he had to undergo another compe-
outside the Palazzo dei Canonici in the
cles, Brunelleschi thickened the out-
tition. He was declared the winner over
Piazza del Duomo, looking thoughtful-
er dome at the inside of its corners at
his competitors Lorenzo Ghiberti and
ly up towards his greatest achievement,
nine different elevations, creating nine
Antonio Ciaccheri. His design (now on
the dome that would forever dominate
masonry rings, which can be observed
display in the Museum Opera del Duo-
the panorama of Florence. It is still the
today from the space between the two
mo) was for an octagonal lantern with
largest masonry dome in the world.The
domes. To counteract hoop stress, the
eight radiating buttresses and eight
building of the cathedral had started
outer dome relies entirely on its attach-
high arched windows. Construction
in 1296 with the design of Arnolfo di
ment to the inner dome at its base; it
of the lantern was begun a few months
Cambio and was completed in 1469
has no embedded chains.
before his death in 1446. Then, for 15
with the placing of Verrochio’s copper
years, little progress was possible, due
ball atop the lantern. But the façade
to alterations by several architects.
was still unfinished and would remain
The lantern was finally completed by
so until the 19th century.
Brunelleschi’s friend Michelozzo in 1461. The conical roof was crowned with a gilt copper ball and cross, con-
3.4
taining holy relics, by Verrocchio in 1469. This brings the total height of the dome and lantern to 114.5 metres (375 ft). This copper ball was struck by lightning on 17 July 1600 and fell down. It was replaced by an even larger one two years later.
3.3 Dome seen from the Giotto’s Campanile (Giotto’s Campanile is a free-standing campanile that is part of the complex of buildings that make up Florence Cathedral on the Piazza del Duomo in Florence, Italy.) 3.4 Duomo Dome.