Posted
on August 7, 2014
The
ancient civilizations of Greece and Rome were times of great art,
great science and mathematics, great learning. Many other times and
places are known for their flowering of art, invention, and
science—the Egyptian pharaonic age in Africa, the Mayan and Incan
civilizations in Central and South America, the Islamic Golden Age in
Arabia and surroundings, the Indian and Chinese civilizations in
Asia—but much of Europe struggled through centuries of what some
call the “Dark Ages.” More often called the Middle Ages or
medieval times, there was more burning books and smiting than we
might like, and a little less scientific collaboration and artistic
sharing than we might desire.
Until
the Renaissance!
The
Renaissance – a cultural rebirth, a flowering of exploration,
innovation, and discovery that started in Italy in the late 1300s –
impacted philosophy, science, music, and of course art, including
painting and sculpture.
And
including architecture.
The
construction of the dome of Santa Maria del Fiore, in Florence,
Italy, which began on this date in 1420, is considered the beginning
of the Renaissance in architecture.
Actually,
by 1400, the cathedral had been under construction for a century and
still lacked a dome. The design for the dome had been completed long
before, and a scale model that was 15 feet high and 30 feet long (4.6
m by 9.2 m) had been standing in a side aisle and was considered
almost sacred at that point. But the dome design was a tricky one –
it was an octagonal dome that was higher and wider than any ever
built before – but it had no external buttresses to keep in from
spreading and falling under its own weight.
Why
no buttresses?
Apparently,
because buttresses were used by Italy's enemies to the north, they
were considered ugly and undesirable.
Architect
Brunelleschi was supposed to build the dome, even though the internal
invention needed to prevent spreading without buttresses had yet to
be invented! He looked to the Ancient Roman dome called the Pantheon
for a solution to the problem of building the impossible dome. The
dome of the Pantheon was a single shell of concrete; a wooden form
held the dome aloft while the concrete set. But there was not enough
wood in all of Tuscany to build all the scaffolding and a form big
enough to create the dome designed for this cathedral.
So
Brunelleschi innovated. He created four internal horizontal stone and
iron chains that were rigid octagon shapes; they served as barrel
hoops, of sorts. The largest chain was placed at the bottom and
embedded within the inner dome, and the smallest was located at the
top; the other two were spaced at equal intervals within the body of
the dome. There are also vertical ribs set on the corners of the
octagon, curving toward the center point; the visible ribs are
supported by 16 concealed ribs. The ribs had slits to support beams,
which in turn supported the platforms that workers stood on to
complete the higher and higher portions of the dome.
Brunelleschi
also used a herringbone brick pattern to transfer the weight of the
freshly laid bricks to the nearest of those vertical ribs, while the
mortar was drying.
There was also an outer dome that relied on its attachment to the inner dome at its base to counteract hoop stress. The hoops were nine masonry rings that can only be seen in the finished cathedral from the space between the two domes.
There was also an outer dome that relied on its attachment to the inner dome at its base to counteract hoop stress. The hoops were nine masonry rings that can only be seen in the finished cathedral from the space between the two domes.
The
dome is crowned with an octagonal lantern that features eight
high-arched windows. The cone-shaped roof of the lantern was topped
with a gilt copper ball and cross – but in 1600 the ball was struck
by lightning and fell down. Two years later, an even larger ball was
made to replace the top piece.
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