St Peter’s Dome
Group 21
Richard Brady
Brendan Gallagher
Shane Ryan
Background Information:
• Vatican City, Rome
• Construction began in 1506 under
Pope Julius II and architect Donato
Bramate.
• However both died later and the
project was handed over to
Michelangelo who saw the project to
near completion dying two years
before the end of the project
Dome Interior
• Michelangelo
constructed the dome
using heavy masonry
and iron rings to
combat tensional
forces
• Diameter 42.6m
• Height 137.7m
Understanding Forces in
a Dome:
•Above 52˚ compression
• Below 52˚ tension
• Consider an arch
• The dome is simply an
arch rotated in 360˚
• However, the difference
is a dome naturally
produces hoop forces
along its parallels to
resist the tensional forces
experienced the lower
half
• BUT……………………
Failure Occured
• Self weight of the dome
was greater than the
yield strength of both the
iron rings and hoop
forces
• Failed by tensional fatigue
• ‘favorable’ failure as it is a slow
and evident
Actions Taken
• By the 18th century the cracks were
deemed to be serious enough
• Extra iron rings were inserted in this
problem area plus four chains.
• To this day these two strategies have
prevented any further cracking containing
the tensile force.
Any Questions??
Thanks for listening