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49793.  Wed Feb 08, 2006 10:58 am Reply with quote

Before the 20th century, when was the largest dome ever constructed?

The dome of the cathedral of Santa Maria del Fiore in Florence, finished in 1436.

The foundation stone for the cathedral (or Duomo) was laid in 1296 by the master mason Arnolfo di Cambio who died soon after. Construction continued despite problems, including the Black Death, until 1366 when nave had been vaulted and the east end of the church, which included the dome, was ready to be planned.

Arnolfo probably intended a dome, but no plans survive since sometime in the 14th century his model of the cathedral collapsed under its own weight. Excavations in the 1970's revealed the foundations for a dome that would have been 119 feet in diameter.

In 1366, two architects created designs for the cathedral. One, the resident architect-in-chief (or capomaestro) named Giovanni di Lapo Ghini, designed a gothic structure with thin walls, tall windows, and huge buttresses to support the dome on top.

However a rival architect, named Neri di Fioravanti, belonged to a group who rejected the ugly external buttresses of gothic designs, partly for aesthetic reasons but possibly also due to political ones, since such styles were popular with Florence's traditional enemies; Germany, France, and Milan. Neri's designs were very ambitious and largely untested incorporating a series of stone or wooden chains which would support the dome in the same way bands of metal support a barrel.

The people in charge of making the decisions (the wardens of the Opera del Duomo) were concerned about this design since this was an age where there were no guarantees that a large building wouldn't just fall over a year or two after it had been built. Thus, although they opted for Neri's design, concerns raised by Giovanni caused them to specify that the pillars that supported the dome should be enlarged.

However, though it sounds like a good idea, enlarging the supporting pillars created another problem. The pillars themselves formed the outer edges of the octagon on which the dome was to sit. By increasing the size of the pillars, the outer circumference of the octogon was also increased, requiring an even wider dome to cover it. After a referendum of the citizens (possibly an attempt to shift the blame if it went wrong) it was decided to increase the size of the dome. At a mean diameter of 143 feet 6 inches this would be the biggest dome in the world, exceeding even the pantheon in Rome which had held the record for over 1,000 years.

Not only would it be the largest dome, it would also be the highest. The walls of the cathedral were already 140 feet high, but there were plans to erect a tambour (or drum) on top of this to serve as a pedestal for the dome. Thus the vaulting of the dome would begin at a height of 170 feet.

The highest Gothic vault in existance at the time was the cathedral of Saint-Pierre at Beauvais. This began at a height of 126 feet and rose to a maximum height of 157 feet, still 13 feet below where the vaulting for the dome of Santa Maria del Fiore would start. The floor beneath the vault at Beauvais was only 51 feet wide, compared to the 143 feet in Florence. The fact that the main vaults in Beauvais had collapsed little more than a decade after completion can't have settled people's nerves in Florence any.

Neri created a model of his design, 15 feet high and 30 feet long, and it became an object of veneration in Florence. So much so that, years later when they actually got 'round to building the thing (the dome's construction finally began in 1420), there was great resistance to changing any part of the design even when it appeared that it would be impossible to build as it stood.

One major problem posed was the question of centring, constructing a scaffold to support the dome while it was being constructed. This was the traditional way to build domes since it stopped the dome falling in on itself before it was finished and became self supporting. However, given the size and height of the dome, one estimate claimed that it would require as many as 700 trees just to produce enough wood to make the scaffold. Timber was second only to marble in terms of expense in those days.

The only person who was able to pull off such a remarkable feat of engineering was Filippo Brunelleschi. Already known throughout Florence for his pioneering work on persepctive (a new concept and one that would pave the way for the artistic revolution of the Renaissance), he invented a way of constructing the dome such that each row of bricks was supported by the one below, thus removing the need for any centring.

As well as this, Brunelleschi invented several machines to aid construction, including an ox-powered hoist with a reverse gear so that stones could be lifted or lowered without having to change the direction in which the ox walked. He also made great improvements to the working conditions of the builders such as installing a cookshop on top of the tambour (at the base of the dome) to serve the builders a meal at noon. His strict rules for safety ensured that, in the 16 years it took to construct the dome, only 1 person was killed on the site.

After its construction, the dome was never really surpassed. Despite Michelangelo's boasting at the time, the dome of St Peter's in Rome, completed in 1590, is almost 10 feet narrower. Christopher Wren's pretend dome on St Paul's is 30 feet smaller, and the Capitol in Washington DC is only 95 feet in diameter, less that two-thirds of the size of Brunelleschi's dome. Wider vaults were only raised in the 20th century when modern materials such as plastic and aluminium allowed the construction of larger structures.

Source: Brunelleschi's Dome by Ross King

49843.  Wed Feb 08, 2006 6:35 pm Reply with quote

Thanks for the work that went into that, Dr Bob. I like the bit about the reverse gear on the hoist particularly.

49844.  Wed Feb 08, 2006 6:43 pm Reply with quote

Google results on the collapse of a ‘campanile’ or bell tower are rare

whither lieth truth

Just realised that this isn't necessarily relevant to domes *sharp intake of breath*

49859.  Wed Feb 08, 2006 7:45 pm Reply with quote

Not only did Brunelleschi install a kitchen between the inner and outer dome, he also installed toilets. Better than having the workmen pee over the side, I suppose...

49872.  Wed Feb 08, 2006 9:26 pm Reply with quote

I bet it didn't stop them, though

49888.  Thu Feb 09, 2006 5:34 am Reply with quote

Flash wrote:
Thanks for the work that went into that, Dr Bob

No probs. Brunelleschi really was an amazing man, especially when you consider that all the things he did involved in the building of the Duomo's dome were done before all the intellectual advances of the Renaissance, and that the feat of building a dome that size was unsurpassed for 500 years (and just think how much technology advanced in those 500 years). No wonder Leonardo was a fan.

Jenny wrote:
Better than having the workmen pee over the side, I suppose...

Especially if there was a service going on below! :)

I don't think the cathedral was generally used before it was finished, but I think they did hold certain ceremonies there on special occasions.

49916.  Thu Feb 09, 2006 7:05 am Reply with quote

I've walked (climbed) up the inside of that dome, between the skins, and even the stairs are a work of maniacal genius. The view from the top isn't bad either.

Inside the inner dome, visible from the centre of the cathedral, are huge and gruesome depictions of hell:
The dome has eight segments, and here the pictorial scheme uses the eighth segment to depict the eighth, or final day. Here Zuccari has employed symbolism and allegorical figures to represent concepts, as was common in the late Renaissance. In the lower part of this segment, in the centre, the old woman with many breasts is nature, and she is going to sleep with her children, because at the end of time there will be no more need for her. Similarly, Death, the skeleton to the right is breaking his scythe over his knee, and Time, to the left, is breaking his hourglass. All around the lower level are the regions of hell, where Christ the judge is sending the sinners. Zuccaro seems to have been quite excited by the visual possibilities of such a representation because he has devoted the most space to this. It is here that we see the demons at work inflicting ingenious tortures on the damned souls.

From the gallery in the dome, there's an ingeniuos perspecive trick in the way the floor marbles have been chosen and laid that makes it look like it's stretching down to hell:

49934.  Thu Feb 09, 2006 8:00 am Reply with quote

Wow! The second picture really gives you an appreciation of the scale involved.



49943.  Thu Feb 09, 2006 8:37 am Reply with quote

It can also induce vertigo :)

54648.  Wed Feb 22, 2006 10:27 pm Reply with quote

I was thinking of Domes earlier today (yesterday) strangely enough but I was thinking more along the lines of this one

The £768 million Millennium Dome, the world's largest enclosed space, opened on the first day of the new millennium, January 1, 2000.

this sort (Eden project)

or this sort (Omaha Zoo)

The world's largest indoor desert, the Desert Dome, located under the world's largest glazed geodesic dome has become a landmark of Omaha.

This leads to Richard Buckminster-Fuller and his unusual outlook and ideas, eg the aerodynamic Dymaxion (dynamic maximum tension) car, house and map. Whilst I'm short on Buckminster-Fuller anecdotes myself Wiki suggests links with polyphasic sleep, John Denver and diaries (for 68 years, 1915-83, he chronicled his life every 15 mins apparently).

There's also 'Buckyballs' (spherical fullerenes) which are QI and goodness knows what factoids we can dredge up about them by trawling our collective seams of accumulated factlets.

Buckminsterfullerene (C60) 1996 Nobel Prize for Chemistry - Curl, Kroto and Smalley.

If heading towards religious architecture I guess we shouldn't forget this sort

which I've been to and is pretty impressive.

It is not the worlds largest however
At the foothills of the Margalla Hills in Pakistan's capital of Islamabad, the Shah Faisal Mosque is one of the core places of Muslim worship in Southern Asia. It was erected from foundations to prayer in just 5 years in 1976.

which looks like this

54662.  Thu Feb 23, 2006 4:54 am Reply with quote

I've been to the Blue Mosque in Istanbul (not Constantinople) and it is simply wonderful.

54669.  Thu Feb 23, 2006 5:25 am Reply with quote

I seem to remember there being some interesting facts about the dome on the Radcliffe Camera in Oxford, although I cannot remember them specifically and would not want to post untruths. Anyone know some QI factoids about the building?

54816.  Thu Feb 23, 2006 9:29 am Reply with quote

djgordy wrote:
I've been to the Blue Mosque in Istanbul (not Constantinople) and it is simply wonderful.

QIly the Greeks and native Byzantines called it 'Istanbul' as well or at least
Emperor Constantin made it the capital of the new Roman empire of the East, but paradoxically the Greeks refused this naming and continued to call it Byzance or even sometimes simply ' this city ' : in Greek ' isten polis ' which, for the Ottomans after the conquest of the city in 1453 became Istanbul.

Somewhere I've got a photograph of sunset over the Blue Mosque taken from a cruise-ship on the Bosphorus with a very cheap camera. It's quite possibly the best photograph I've ever taken or perhaps ever will take, the subject matter helped a lot.

Last edited by Celebaelin on Thu Feb 23, 2006 9:32 am; edited 2 times in total

54817.  Thu Feb 23, 2006 9:30 am Reply with quote

The only other dome I know somethign quite interesting about is the Houston Astrodome. I'm sure everyone already knows this, but it's the source of AstroTurf and indeed gave it its name.

I saw a TV show recently about designing stadiums (stadia, whatever) and how very difficult it was to make sure the grass grew properly. When the astrodome was built everyone was very surprised to find that the grass just died off, so they had to invent artificial grass to play on.

It turns out that, as well as light, grass needs free flowing air as well. There are some open-topped stadiums which have patches at the sides or in the corners where the grass won't grow because the air doesn't move around enough. There's even a stadium in Germany (I think) where the entire pitch can be slid outside to sit next to the stadium and get some decent fresh air between games.

Air flow around stadiums is now a well-understood science and is vitally important when designing new sporting venues.

54822.  Thu Feb 23, 2006 9:38 am Reply with quote

The turf at the Millenium Stadium is on palettes too. Presumably, since the roof can be closed, for this reason at least in part. It also allows the floor area to be used for events where turf would not be suitable. I think some/one of the football stadia built for the World Cup in Japan has a similar arrangement, although something at the back of my mind suggests that their system is motorised and I can't say I've heard that about any other.


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