The Collapse and Restoration of the Church of Saint Mary of Itria in Piazza Armerina (Sicily, Italy)

The paper illustrates the damages occurred to masonry buildings due to incorrect consolidation interventions dated back to the 1980s that, according to the culture of the time, were oriented to the replacement of structural elements with new heavy ones, thus changing the static scheme. The case study concerns the seventeenth century church of Saint Mary of Itria in Piazza Armerina, affected in 2007 by the collapse of the one side wall of the apse. After illustrating the historical evolution and the actual state of the building, the investigations carried out to identify the causes of collapse and provide for appropriate reconstruction interventions are reported. The results of hydro-geological and geotechnical surveys lead to exclude foundations subsidence from the causes of the collapse. The study is focused on the analysis of the interventions carried out between 1980 and 1985 for the replacement of the existing wooden covering with girder and hollow block floors, connected with RC curb. The structural analysis was carried out under two load conditions before the collapse with the existing RC roof and with the previous wooden one, showed irrelevant load increase. Thus, the cause of collapse was identified in a variation on the load distribution. The planned intervention concerned the reconstruction of the wall with collapse recovery stones and blocks of similar physical-mechanical properties, the improvement of the walls resistance with mortar injections, the construction of curbs on the top of the walls, the stretching of transversal tie-rods and the introduction of new ones.