Florence Cathedral

This is Florence Cathedral, located in Florence, Italy completed in 1436. Over time, the cathedral has had many additions added to it over hundreds of years, the most famous being the dome built by Filippo Brunelleschi. Here is a diagram of the major additions:

When the people of Florence voted to build a dome, none of the artisans in the city were skilled enough to build such a large dome. Half a century later, the city brought together a group of artisans and held a competition for the design of the dome. Brunelleschi won the contract to build the dome. His design was a thick brick inner dome, with a light shell of a dome on top for protection against the elements. He was up against a monumental task. Why? For a number a reasons. The first was that the dome was taller than it was wide. This created more "hoop stress" (the tendency to buckle in a dome). The second reason was there wasn't enough wood in all of Tuscany to build centering for the huge dome. (centering being wooden arches used to support the dome during construction.) He remained undaunted by the task. The first of his solutions was to use brick as opposed to stone, thus lightening the load. This also made it easier to lift the building material up to the construction level. He built the dome as the dome of the Hagia Sophia was built: by have concentric circles of bricks in successive layers that were held together by compression. The problem with this was that   the bricks slid of before the mortar dried. He solved this problem by using the "herringbone" brick pattern which looked something like this:

The zig-zag pattern left bricks from one layer sticking up into the next layer. These bricks sticking up gave the next layer some thing to brace against. He then undertook solving the problem of the height of the dome. He did this by placing 5 chains inside the dome. The top four were stone, and the bottom one wood. They were arranged like railing road ties and held the dome together. Since the dome was octagonal, the chains were octagonal so that corners of the dome wouldn't buckle. Also, the chains were wider than the inner dome which they were strengthening, so the protruded into the space between the inner and outer dome. The cross-ties of the lowest chain can be seen protruding out from the masonry:

(the cross-ties are the squarish things sticking out between the red dome, and the white marble)

Brunelleschi even added a heavy stone lantern on top of the dome. 

The dome is considered to be Filippo Brunelleschi's masterpiece because of the genius it took to build it. 

In this blog post, you saw why. I really enjoyed posting on this cathedral, having watched a lecture on it by Prof. Ressler.