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BRICK 16century ARCHED ROOF in Florence ..I can`t figure how it works!

BRICK 16century ARCHED ROOF in Florence ..I can`t figure how it works!

BRICK 16century ARCHED ROOF in Florence ..I can`t figure how it works!

(OP)
In the Centre of FLORENCE there is an eight-curved-sided roof ontop of the cathedral. It`s not a round "arched dome" but eight curved sections meeting at a point...the top.
So each each section is bent over (in only one plane) to form the "appearance" of a dome but in reality its eight "leaning-over" walls of bricks !

For the life of me I cant figure why it doesn`t sag (horizontally) across each wall and collapse.

Any help from the experts here? Im a civil engineer so can understand a little structural stuff.
Thanks
Andy in England

[Google The Duomo Florence for an image]

RE: BRICK 16century ARCHED ROOF in Florence ..I can`t figure how it works!

Andy - there was a fantastic television documentary on this just the other night in my area (central US). There is a man named Massimo Ricci from Italy who has been researching this for some time.

He is actually constructing a smaller scale of the same dome. What he discovered was that Brunelleschi (the designer/builder) used a special masonry pattern where every so often the horizontal bricks would turn vertical - sort of a herringbone pattern, that added stability to the arching masonry and prevented a full stretch of mortar joint from opening in tension.

Here are some links:

Nat Geographic Link 1

Nat Geographic Link 2

NOVA Documentary Link

You can purchase the 52 minute documentary here for US$1.99

The whole story is pretty captivating from an engineering viewpoint.

RE: BRICK 16century ARCHED ROOF in Florence ..I can`t figure how it works!

(OP)
Thanks! What a coincidence! I looked and saw that I wasn`t the only one wondering how it stood up. It is quite startlingly wrong looking.
I did try to ask a few Florentine guides but got roundly ignored in their rudeness... tuned to a fine level ! So have been wondering about this ever since then.

It would seem to me that the brickwork ..created into almost a cast concrete slab-like material.. has an inherent strength too.
The taper of the roof is not entirely domelike either. And I suspect he "got away with it"... tapering the forces against the narrowing profile as it gets higher. A scale model would have given a great deal of feel beforehand..

I wonder how many "genius talents" like him DIDN`T get away with it and watched their structures all fall down!!

RE: BRICK 16century ARCHED ROOF in Florence ..I can`t figure how it works!

Andy - a couple of points that came out in the documentary (I strongly recommend it - I was captivated by it).

1. The dome isn't 8 sided - it just looks that way because of the added ribs.
2. The brickwork didn't have flat mortar joint lines - he used a "flower" pattern on the floor below and used lines to create a series of dipping joint lines - like waves - in addition to the herringbone pattern.
3. They found a buried dome nearby that was built exactly like the large dome. They speculate that this is where Brunelleschi built a mock-up to convince his masons to trust his plan.

My wife and I climbed up to the top a few years ago and it is a spectacular experience. Highly recommend it.

RE: BRICK 16century ARCHED ROOF in Florence ..I can`t figure how it works!

(OP)
Umm thanks. My main interest is the lack of horizontal plane curvature. Even with a few intermediate ribs a straight line of brickwork is pretty weak in that plane. I still cant see any curve... though you may be right when you get close up.

The other thing is I doubt very much if a DIY goldsmith would have been given the job without a least some experience and authority..even then.

I was there for a conference, so never got up the top. Next time !
Thanks for the replies. I`m not sure I can get it here in UK ... `legal reasons` come up...
Kind regards
Andy

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