Ancient Persian Dome Technique Used in Florence Cathedral

Absolutely fascinating.  I wonder how old this Persian technique was and how it was that Filippo Brunelleschi (1377-1446) discovered the technique?  Did he travel in the Middle East?  Did he come across ancient texts describing the technique in some obscure library or other?  And how did he successfully employ it in building the magnificent dome at the Santa Maria del Fiore, the highest and widest (143 feet in diameter) masonry dome in the world?

From Discovery News Online

Scale Model Discovered for Florence Cathedral

Jan 10, 2013// by Rossella Lorenzi

 

Italian archaeologists have unearthed the remains of a mini dome near Florence’s cathedral — evidence, they say, that the structure served as a scale model for the majestic structure designed by Filippo Brunelleschi (1377-1446).

Found during excavations to expand the Cathedral museum, the model measures 9 feet in circumference and it’s made of bricks arranged in a herringbone pattern.

“This building technique had been previously used in Persian domes, but Brunelleschi was the first to introduce it into Europe when he worked at the dome,” Francesco Gurrieri, professor of Restoration of Monuments at the University of Florence, told Discovery News.

“Although at the moment we cannot confirm the small dome was the demostration model for Brunelleschi’s plans, it did belong to the yard he created between 1420 and 1436, when he worked at one of the most incredible feats of engineering,” Gurrieri said.

One of the most instantly recognizable churches in the world, the dome of Santa Maria del Fiore is the highest and widest (143 feet in diameter) masonry dome in the world.

For centuries scholars have wondered how the Florentine architect could roof the huge octagonal of the Cathedral using not concrete and steel, but 25,000 tonnes of stone, timber and brick — and no scaffoldings.

Indeed Brunelleschi won the right to build the dome by saying that he wouldn’t need any internal scaffolding.  He raised sandstone and marble slabs hundreds of feet into the air and boldly constructed the huge masonry bubble without relying on a centering wooden framework.

To do so, the Renaissance genius used complex techniques — still debated by experts — and inventive brickwork which included creating a new way of sharing the weight around the dome so that it wouldn’t collapse.

Laying the bricks in the herringbone pattern was a crucial aspect as it allowed the bricks to convey the forces downward along the curving of the dome.

(This is a line drawing of the scale-model dome discovered in the Cathedral yard.  Look at the pattern that the brickwork was laid in:  it reminds me of the Fibonnaci Spiral.  Notice that there are EIGHT spirals around this dome structure.  Obviously, the technique worked -- the Cathedral still stands today, dome intact.  It was completed in 1436, although construction continued on various parts of the Cathedral into the 19th century!  More information on the Cathedral.) 

“The small dome could be the first example of an herringbone pattern structure in Europe,” Gurrieri said.

Roberto Cecchi, the undersecretary of the Ministry of Cultural Heritage, agreed that the finding is important.

“The herringbone tecnique is very much linked to Brunelleschi and Florence. Outside the city we have only a couple of examples of this technique, and they date later to the 16th century,” Cecchi said.

Once it is fully excavated and restored, the mini dome will be permanently displayed at the new museum of the “Opera di Santa Maria del Fiore,” which is set to open in October 2015.

 

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Can modern engineers explain how/why this technique works, and if it works so well -- the dome is nearly 600 years old, so I would say that qualifies as working well -- why did we abandon the building technique?  Will anything our modern engineers are designing and building today be around in 600 years???