The Cracking of St. Peter’s Dome
Location: Vatican City,
Italy
Completion Date: 1626
Diameter: 42.3 metres
Type: Ribbed
Purpose: Religious
Materials: Concrete
Architect: Donato
Bramante, Michelangelo
The Cracking of St. Peter’s Dome
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St. Peter’s Basilica is
situated in the Vatican
City.
The Dome of St. Peter’s
Basilica was
commissioned in 1506.
The principal designer of
the dome was
Michelangelo.
Design of the Dome
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The original plan was for
a single shelled dome.
However, this was
proved unfeasible.
Michelangelo’s design
was a double shell dome
made of heavy masonry.
Design of the Dome
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The dome would be
42.3 metres in diameter
and would rise 120
metres above floor
level.
Iron tension rings were
built into base of dome
to contain outward
force.
Dome Diameters
St Peter’s Dome
138’
Problems Arise
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Early 18th Century.
Dome began cracking.
When a dome is too
heavy, the sides push
outward, and cracks
appear throughout the
bottom portion of the
structure.
Solution
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Vatican engineers tied
several tension rings
around the structure.
These acted like hoops
on a barrel.
This proved successful.
Present Day
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The hoop design of the
Vatican engineers has
stood the test of time.
Outward forces have
caused no further
damage to the dome.
Group 21
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