Seismic Risk Assessment of Ruins in Pompeii’s Archaeological Site through the reference case study of the Stabian Baths.

Unlike the numerous studies on historical centres which have been deeply addressed, the seismic risk of archaeological sites is a topic not much discussed in the scientific literature. It represents a complex assessment aimed at mitigating the vulnerability ancient artefacts to earthquakes and, therefore, to reduce the loss of inestimable historic and artistic heritage. The archaeological site of Pompeii - and in general of the Vesuvius centres - since the discovery in the Eighteenth century has been, and it is still today, the field of a battle, which attempts to ensure the survival of artefacts characterized by “fatigued” materials, without roof structures and therefore lacking in constraints, exposed to the strongly aggressive atmospheric pollution of the cities of the 21th century and located in areas where the expected ground acceleration values are of medium degree. Moreover, the methods necessarily of “integral” conservation aimed at preserving both the material and the original configuration allow “soft interventions” that moderately improve the response of ruins to the stresses deriving from gravitational loads and, in particular, from seismic actions. This paper describes the research project Analysis, interpretation and evaluation of the seismic vulnerability of the construction elements constituting the archaeological apparatus of the Pompeii site, signed in March 2018 between the Department of Architecture of the University of Florence and the Parco Archeologico di Pompei. The purpose of the study is the definition of a thematic reference map based on the definition of the values of the site risk indices. The research consists of several phases. Preliminarily, the developed methodology includes investigations on the seismic behaviour of the single construction elements - arches, vaults, colonnades, free walls and walls with various types of constraints, non-structural elements etc. - in their variability of geometry, masonry organization and material characteristics, crack and deformation pattern, considering the evolutionary aspect of the construction, with particular regard to the strategies put in place by the ancient Romans to repair or reinforce the damaged buildings. Such a detected potential level of damage, in terms of limit states, is obtained through calculation codes (some of them have also been developed by the authors) selected to predict the behaviour of ancient artefacts. Subsequently, the achieved data are related and implemented considering the occurrences of single construction elements in the archaeological site, the interactions with contiguous buildings as well as possible site-effects, thus creating a seismic risk map for each individual insula. Aimed at extending the methodology proposed herein to other insulae of the archaeological site in future studies, its effectiveness and validity are assessed by analysing the reference case study of the Stabian Baths, a block whose seismically vulnerability has already been analysed by the authors in a previous paper.