The Leaning Tower of Pisa… Just seeing it, in real life, for the first time-standing alone, on it’s own , character abundant and unparalleled… that is what struck me.

Upon climbing the tower I found it hard not to think that at any point it could fall, carrying with it all of us starry-eyed tourists gazing at the rooftops. I know it is rather morbid, but I actually thought that it would be an epic way the die- to fall to ones death with the Leaning tower of Pisa. I am not sure, still, if, in fact, this could be an actual possibility. According to Joan Steen, the tower will “collapse before long.” She gives an example of the acceleration of the lean, which has gone from a .04 inch lean per year to a .06 inch lean. At this rate, she says, the tower won’t last another generation. This was, I think, before the onset of the soil extraction, which has now significantly decreased the pressure exerted on the tower by gravity.

I also wondered how much stress is put on the tower by the constant torrent of tourists upon it. I thought about the college shenanigans of all rushing to one side of an airplane to make it tip over; could this also happen with the leaning tower? And how much extra weight would it take? I thought about the variance of soil. How is it that the soil is softer on one side of the tower ? Was it just a matter of the soil, of was the weight distribution of the tower off to begin with, causing the lopsided nature of the tower from the beginning. In Steen’s article, she mentioned that one scientist was thinking about inserting chemicals in the soil to change its make-up to be able to sustain the weight of the tower more effectively. Would that have worked in the beginning, when they first thought of the soil as the culprit for the sinking? And if the soil is, in fact, the reason for the sinking, how come the constant pressure from all the walking above isn’t enough to make the streets sink in the same way?

I was also intrigued by the interest of the different artists, engineers and thinkers in the tower, among who were Bonanno Pisano, Giovanni Of Simone, Thomas Pisano, and the many academics who formed the Committee to aid the tower. They practically dedicated their lives to the vigilance of the Leaning tower of Pisa. I think is amazing that so many minds would be drawn to fix one problem. It also strikes me that the very demise of the tower of Pisa (its crookedness) is the same thing that has made it so famous, and one could even argue, the thing that gives it its beauty.

-- EutimiaMontoya? - 05 Apr 2005

Class Presentation: Tension in The Cupola of Il Duomo di Piazza Santa Maria del Fiore

It was very interesting for me to read time and again that the predominate reason for the cracks in the dome, aside from any other structural defect or extraneous occurence such as severe weather or traffic noise, is simply its dead weight. The Cupola, itself, weighs anywhere from 22,000- 35,000 meric tonnes! The pull of all of this dead weight on particular part s of the structure causes tension and. sunsequently, cracks.

The concepts of "a fixed -end bending moment" and "tensile stresses" were the most helpful for me in visualizing and understanding the possible places of tension in Filipo Brunelleschi's design for his cupola ar Santa Maria del Fiore. Basically, a fixed-end is the point from which an object is being pulled. We illustrated this point in class when we took wooden rods, fastened them to the edge of a table, and applied force to the free side. At a certain pressure, the rod would break. The place and time where it broke is called the fixed-end bending moment. It is these bending moments that cause the tensile stresses on other parts of the dome.

These bending moments are where the major cracks occur in the dome. They are located on the 4 even numbered panels of the dome ( panels named 1-8 going counter clockwise from front entrance facing west) which are the panels that do not have arches. The bending moments occur down the midline of these panels which recieve pressure caused by the pull of the arches on the adjacent panels, and therefore, foster full tensile stresses which, eventually turn into cracks. Where are there other stresses? What causes these stresses? You can find all the information you need in these two books:

Fanelli, Giovanni and Fanelli Michele. Brunalleschi's Cupola: Past and Present of an Architectural Masterpiece. Mandragora. Florence, Italy. 2004

Prager, Frank D. and Scaglia, Gustina. Brunalleschi: Studies of his Technology and Inventions. The MIT Press, Cambridge, Massachusettes. 1970

Below are some pictures of the Cupola, its layout and its stresses. Enjoy!

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