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