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An Architectural Miracle: Brunelleschi’s Dome

Brunelleschi’s Dome




Santa Maria del Fiore is a historically crucial cathedral with a background of a challenging dome design. Various competitions over diverse parts of the cathedral were made throughout its construction years. Architecture evolved fast and construction devices developed relatively slowly. It was an essential for Florence to complete the dome and create it in a well-constructed strong way that people could rely on the design and safely visit this building. Filippo Brunelleschi, a man with unique technical knowledge and a constructive mind, a so-called, “madman” (King, 2000) for his refined skills, would be the one to solve Santa Maria del Fiore’s dome puzzle.


On August 19, 1418, a competition was announced for the construction of a dome in Florence. After over a century of construction, Santa Maria del Fiore was in need of a dome that would perfectly fit with the overall silhouette of the entire cathedral. The prize for this design would be two hundred gold florins, which is more than any craftsmanship could earn in two years (King, 2000). The time frame was six weeks, the design would be accepted in the conditions of solving constructive problems while being in harmony with the cathedral’s rest. The proposals could be verbal, as a model or in a form of a drawing. However, architectural design requires both imagination, which would suffice the aesthetical needs, and skill for the construction process. The directory for the competition also included defining the details of the wooden structure which would carry the bricks of the dome in the process and also to the top (King, 2000).


A Brief Background


In the 15th century Florence was economically developed and wealthy. At that time, Italy was divided into two sides regarding the management of the city-states, those were: nobility regimes and republics. Florence was among the states controlled by the commercial elite as Republic (Haakonssen, as cited in Manetti, Belluci, Bagnoli, 2019). The wealth of the city should have been portrayed through construction, despite Florence being an economically inclining city, it still had rural areas contained within the borders. This necessary transformation of the city could be done with the construction of a human-scaled city which would last in the future and the current state. This is why the Cathedral carried such importance for the overall interpretation of Florence for the outsiders. Extraordinary wealth accumulated has concluded in the project of Santa Maria del Fiore (Haakonssen, as cited in Manetti, Belluci, Bagnoli, 2019).


Figure 1: Roselli F., (14??) Carta della Catena [Painting]. florenceforfree. https://florenceforfree.wordpress.com/2012/12/20/traces-of-florence/

The Process for the Cathedral and the Dome


By 1418, the grandest building project of Florence still had to be finished, that was the replacement of the ancient church of Santa Reparata. It was expected to be one of the largest in Christendom (King, 2000). The initiative for this dome project was an artist’s illustration of the cathedral which depicted that the dome would be one of the highest and the widest domes if it was ever built. This situation might have concluded with a high risk of collapsing. During the construction process nobody had a clear idea of how it is possible to raise a dome that high. It was essential for the cathedral to be completed, as major alterations were made within the city to create the perfect outcome. The surrounding districts' inhabitants were evicted in order to demolish the prior church and create an open piazza in front of the cathedral. Besides evicting citizens, bones of the dead Florentines were also removed to keep the construction on the west side of the cathedral. A street near the construction site (Corso Degli Adamari) has been lowered to create a better atmosphere for the height of the cathedral. In this way, Santa Maria del Fiore would look more impressive to anyone who’s approaching from the nearby streets. (King, 2000)


In 1347, black death approached Florence and the population started decreasing while the city itself also regressed and its developments lowered. The construction of the cathedral remained the same for a long time with exposed foundations and minimal interior construction. Even one of the close streets has been named “Lungo di Fundomanti” which meant “Along the Foundations” (King, 2000).


Figure 2: Tosi, M. (n.d.) Reconstruction of Sant Reparata [Illustration], Retrieved December 16, 2022. artslife. https://www.artslife.com/wp-content/uploads/2017/11/Ricostruzione-di-Santa-Reparata-illustrazione-di-Massimo-Tosi-courtesy-Opera-di-Santa-Maria-del-Fiore.jpg

During the next decade, the city started to recover and regain the confidence to finally continue construction in 1366. The construction of the cathedral was being administrated by the “wool merchants” at that time. As it was not among their specialty to build churches, the cathedral was in need of an architect-in-chief or a capomaestro, Giovanni di Lapo Ghini (King, 2000). He submitted a model for the dome, however, the wardens of the guild "wool merchants" had requested other options from another group of artists. After this, the faith of Santa Maria del Fiore would have been altered. (King, 2000).


The principal master mason of Florence, Neri di Fioravanti rejected the dome proposal of Giovanni di Lapo Ghini. (King, 2000). His plan was to place external buttresses to support the dome while allowing an excessive amount of light inside of the cathedral. As the height of the dome was extraordinary, openings were only possible with some external adjustment. The goal was to provide an intense amount of light from the top to create a “holy” environment, almost like a connection with God. Although the plan carried out characteristics that would fit with the general idea, it was refused for political and aesthetic reasons. Flying buttresses were not common in Italy as they were pointed out as “ugly and awkward” (King, 2000). Alternatively, this structural element was common in Florence’s architectural enemies, France, Germany, and Milan (King, 2000).


Figure 3: Bartholomew, (1840). A leaning human model representing the cooperation of a flying buttress, pinnacle and external buttress trio in supporting a Gothic cathedral [Illustration]. researchgate. https://www.researchgate.net/figure/A-leaning-human-model-representing-the-cooperation-of-flying-buttress-pinnacle-and_fig1_349857950

Neri suggested a dome with a double shell as this style was common in mosque designs to create a human-scale design inside and magnificent outside. But it would be different because the inner shell would be a smaller one supporting the outer shell. In addition, this style would provide protection for the inner shell considering weather conditions. This model would be the highest and widest dome ever built since antiquity with a diameter of one-hundred forty three feet and six inches. (King, 2000). Neri’s design for the dome was accepted despite the high chance of collapsing. Every year, the administrators of the project architects and wardens, were obligated to swear they would follow the designated instructions for the constructions while putting their hands on a copy of the Bible. (King, 2000). However, when the competition was released by 1418, tremendous amounts of projects were submitted by many citizens,and one of them had particularly struck the attention of the competition executives with an unorthodox solution for the vaulting of the dome. A goldsmith and clock maker, Filippo Brunelleschi. (King, 2000).


Filippo Brunelleschi’s Solution


Brunelleschi had a unique way to manage a larger-scale space rather than utilizing the traditional way of “centering” the dome. In this case, building a wood structure that would hold the structure until it is set, would require intense amounts of forest destruction. Even if the centering technique was used, forests in the Tuscany district would not be enough to provide for such construction for only one dome (Hamerman, Rossi, 1989). Filippo Brunelleschi suggested omitting the wooden structure that supported the masonry design for the dome or the vaults and instead, to increase the reliability of the project he built a model of the dome cooperating with Opera del Duomo (Cathedral Works). By the time the model was built, the current capomaestro, Giovanni d’Ambrogio, was fired (Hamerman, Rossi, 1989).


Figure 4: Inson, N., (2021). Renaissance architecture: imposing structure of the dome of the Basilica of Santa Maria del Fiore [Photograph]. exploringart. https://www.exploringart.co/brunelleschi-santa-maria-fiore-dome/

It is necessary to understand how vaults and arches complement the structure’s static to understand Brunelleschi’s idea. The construction of any arch is only possible with the scaffolding, the structure needs to be strongly held until the last piece has been placed (brick in that case). While arches could be better followed with a geometrical plan, the issue was that a traditional dome would follow the rules of circular shapes. It was not essential to follow the rules of a traditional dome in cases where the domes created a major problem for the overall project. According to Leon Battista Alberti, Brunelleschi’s admirer, architect, and theorist, there is a perfect cupola (dome) that does not require scaffolding tools (Foraboschi, 2016). Combining arches and cornices results in a structure that can carry its weight during construction. By using angular vaults there would be no need for a framework (center) to turn the angular cupolas around itself.


Filippo left no certain drawings, plans, or a piece of writing to grasp the extraordinary nature of the dome. This design also had two shells as Neri proposed before. A thicker interior shell exists within the outer part which is relatively thin. (Bartoli, Chiarugi, Gusella, 1996). The exterior and interior are mainly covered so the idea could not be also observed through a basic survey of the building. The minor observations highlight the quality of the bricks and the precise work. All of the operations were supervised by the master architect throughout the process.


Figure 5: Yudi, A. (2015). Cathedral Santa Maria del Fiore [Illustration]. medium. https://medium.com/retronator-magazine/archipics-when-digital-art-becomes-pixel-art-d791d5b8d5a3#.ejg3f3e7t

The outer shell and the inner shell are linked within joint elements which are formed by masonry walls. And to follow the main rules of the construction of a dome, it always begins where the basis of the dome is laid (tambour), and continues till where the structure starts to have openings in the upper part. Twenty-four elements exist, eight of them are on the corners which outline the octagonal shape of the dome, and the others are placed as two in each corner. Since Brunelleschi had to follow the rules of excluding buttresses and constructing a dome that would carry the lantern - the lantern design was also chosen by announcing a competition that was also won by Brunelleschi - it was decided to crown the cathedral. His design allowed the construction to be completed as successive rings, so it would have the required strength. Without the use of successive arches, it would not have been possible to meet the requirements. A completed ring would be able to carry its own weight and also could be carried by the prior rings. Even though the weight distribution has been done wisely, the lack of framework still was a problem. According to Foraboschi (2016), “Brunelleschi included bricks laid in a herringbone pattern along some loxodromical curves from the springing to the crown. In so doing, the dome could be constructed without any temporary construction support”. The construction of a spherical dome would not be able to carry the thrust and it would have a high possibility of collapsing.


The first criterion for the design was weight reduction of the dome without decreasing its thickness. For this, his plan was to have a ring and spring system between the shells which would allow a significant part of the volume to be empty. (Foraboschi, 2016).


Figure 6: Hayk, N. (n.d.). Lantern of Santa Maria del Fiore [Photograph]. Pinterest. https://ar.pinterest.com/pin/23995810507256378/

The second mandatory fixation was to reduce the springing thrust (forces that push or pull quickly which also include the mass of the object) which could cause some particular cracks, or even cause the collapse of the dome. As mentioned before his use of rings within the structural circumference was indeed the solution. Unlike the external additions, these rings were invisible and did not create any visual confusion. (Foraboschi, 2016).


Most importantly, predetermined cracks (Figure 7) are placed within the design to prevent any unexpected negative outcomes, as well, placing them beforehand also provided some benefits. As Foraboschi (2016) commented, “In so doing, the thickness of the resisting system would have been much greater than that of the shell, and, in turn, the springing thrust much lower.” This means dividing the octagonal shape into “C” shaped sections to create a better weight distribution, which would help with decreasing the overall chances of destruction.

Figure 7: Foraboschi, P. (2016). "The four passing-through cracks split the dome into four pointed semi- arches with ‘‘C”-shaped cross section (drawn in bright). The actual thickness of each ‘‘C”-section is the distance between the rotation axes of the potential hinges at the extrados and intrados of a section. Thus, the thickness of the arches that the dome split into was drastically greater than the thickness of dome." [Diagram]. reader.elsevier. https://reader.elsevier.com/reader/sd/pii/S0950061816303889?token=D1F9584887AC864DAB237B91C791E91480B3B01CD2E4CAD646BAAB2CEF47FC5DA525CECC105D9C1056545753CD794EFD&originRegion=eu-west-1&originCreation=20221216173726

The dome by Brunelleschi demonstrates that avoiding safety assessments is the only method to prevent the invasion of protected areas. Building structural adjustment on cultural structures should only be done if there is a significant structural problem, or if it is necessary to rebuild the building until an adequate balance between safeguarding and conservation is reached. Solely and exclusively when the verbs to conserve and to assess are united into a single word "restore", can structural works - that only aim to assure safety including seismic upgrading - be executed (Foraboschi, 2016). For this reason, he tried to be in harmony with the previously built part while decreasing the chances of damage and increasing the durability in such ways that no craftsman, architect, or other individual has ever thought of.



BIBLIOGRAPHICAL SOURCES

Bartoli, G., Chiarugi, A., & Gusella, V. (1996). Monitoring Systems on Historic Buildings: The Brunelleschi Dome. Journal of Structural Engineering, 122(6). https://ascelibrary.org/doi/epdf/10.1061/%28ASCE%290733-9445%281996%29122%3A6%28663%29


Como, M., (2021). Brunelleschi’s Dome: A New Estimate of the Thrust and Stresses in the Underlying Piers. Applied Sciences. 11. 4268. 10.3390/app11094268.


Foraboschi, P., (2016). The Central Role Played by Structural Design in Enabling the Construction of Buildings that Advanced and Revolutionized architecture. Construction and Building Materials, 114, 956–976. https://doi.org/10.1016/j.conbuildmat.2016.03.092


Hamerman, N., & Rossi, C. (1989). The Apollo Project of the Golden Renaissance: Brunelleschi's Dome. https://doi.org/chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://21sci-tech.com/Articles_2014/Brunelleschi.pdf


King, R., (2001). Brunelleschi's Dome: How a Renaissance Genius Reinvented Architecture. Penguin Books.


Mainstone, R., (2009). Brunelleschi's Dome Revisited. Construction History, 24, 19-30. Retrieved from https://www.proquest.com/scholarly-journals/brunelleschis-dome-revisited/docview/863487996/se-2

Manetti, G., Bellucci., M., & Bagnoli, L. (2019). The Construction of Brunelleschi’s Dome in Florence in the Fifteenth Century: Between Accountability and Technologies of Government. Accounting History Review, 30(2), 141–169. https://doi.org/10.1080/21552851.2019.1686036


Warren, C., W., (1973). Brunelleschi’s Dome and Dufay’s Motet. The Musical Quarterly, 59(1), 92–105. http://www.jstor.org/stable/741461

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