A methodology for the safety assessment of protective roofs covering archaeological sites: the case of the Villa dei Misteri at Pompeii

Pompeii is the largest archaeological site in the world and one of the most visited as well. Villa dei Misteri is a great suburban villa just outside the ancient city. Every year, thousands of visitors are attracted by the superb frescoes from which the domus takes its name. In the course of excavations, the most significant rooms were roofed with the dual purpose of providing weather protection and returning the monument to its ancient state. The results of the restoring interventions display a wide range of roof structure typologies: reinforced concrete frame, reinforced concrete tiles mixed floor, timber and steel frame. The evaluation of their health status requires a detailed study by means of a multidisciplinary approach, which should include historical research, geometrical and structural surveys, damage assessment based on both in situ and laboratory diagnostic tests, UAV (Unmanned Aerial Vehicles) remote sensing to inspect area and coverings not easy to reach in safe, and, as basis for seismic safety assessment, ambient vibration measurement (discussed in a separate paper). In this paper the preliminary results of the survey are presented. In particular, the main causes of decaying have been identified and preventive measures to reduce risk of damage have been suggested. Furthermore, considering that the described methodology has been developed also with the aim to qualify a standard procedure in view of further applications to similar roofing typologies, very common in the archaeological site of Pompeii, a more detailed diagnostic campaign has been planned in order to gather adequate data for a comprehensive safety assessment including seismic vulnerability analysis.