Seismic Protection of Statues. A Case Study

Abstract

The analysis of rocking behaviour is a key aspect of safety assessment the maintenance of artifacts, like statues vases, since the rocking itself can be the cause of damage at the base of the object, due to impact with the support. By seismic excitation, a freestanding object may in fact enter a rocking state which would cause overturning, so that often the sliding is desirable, given the possibility of evaluating relative displacements to avoid collisions. In the majority of cases, museum exhibitions are not equipped with isolation devices for every single contained object. This paper presents the theoretical numerical bases of a simple low cost isolation system to protect small art objects. Smaller artifacts are in fact the more prone to overturning since the rocking response is highly influenced by the size of the object. The insertion of a further rigid body between the moving base the statue can reduce the effect of base motion due to earthquakes. The case study is a real marble statue by Donatello, placed in the Museo dell'Opera del Duomo in Florence.

The Role of Friction in the Dynamic Behaviour of Freestanding Marble Objects

“…The Housner basic assumption for the rocking motion is however an infinite friction coefficient between the two contact surfaces. In real cases, and especially when the protection of statues and other cultural heritage objects is involved [16,17], and in all the cases in which the rocking motion is not an option and should be avoided [18,19] the rough hypothesis of infinite friction coefficient must be removed. Leaving apart the discussion about the possibility of passive or active protection systems [20,21], in all the cases in which isolation systems cannot be used, such low weight of the object to be protected, high financial commitment of the protection, a deep investigation on the real friction values should be performed.…”