Modeling and testing of the anti-vibration base for Michelangelo’s Pietà rondanini

The famous statue Pietà Rondanini by Michelangelo Buonarroti (sculpted in the second half of 1500) was recently moved to a new position in a museum in Castello Sforzesco, Milan. In this new location, the vibration levels, due to the close presence of underground tracks, has been considered worthy of specific attention; therefore both the Municipality of Milan and the Cultural Heritage ministry asked for the design of a new base capable of mitigating the vibration input to the statue. In addition, since Milan is a seismic area (although with moderate risk), it was also required to include in the base design an anti-seismic device. The protection from the underground action (which is in the range between 16 and 80 Hz) requires the development of a system with low natural frequency and rather limited damping, to have a steep filtering after resonance. However in case of an earthquake, the low frequency range would be strongly excited, with the eventual risk of an extreme event like a fall. A second device is thus introduced to protect the statue from earthquakes, which consists of a low friction slide of the same type as those used to protect buildings from the same kind of events. The coupling between the two types of protection imposed a careful design and testing of the complete system made up of the base and the statue. The design of the base was developed by means of an experimental and numerical approach. A measuring campaign using a large 6 of freedom shaking table was used to test a full scale prototype of the base supporting a marble 1:1 copy of the statue. A multibody model of the full installation (complete base and statue) was developed, qualified by means of experimental data, and used to optimize the parameters, such as the mass distribution, positions of the elastomeric supports and the damping of the devices. The final system is now installed in the museum, protecting the Pietà.