A comprehensive multi-level approach for seismic failure analysis of masonry churches in Sorrento (Naples, Italy)

Italy hosts a vast array of ecclesiastical buildings, many constructed well before the establishment of modern seismic design codes. As a result, these structures were built without consideration for seismic forces and frequently lack the box-like structural behavior essential for earthquake resistance. Recent seismic events have exposed their pronounced vulnerability to both local and global failure mechanisms, endangering human lives and threatening the conservation of invaluable architectural heritage. Against this backdrop, the present study evaluates the accuracy and applicability of the simplified mechanical model outlined in the Italian Guidelines for Cultural Heritage (IGCH), with a focus on Evaluation Level 1 (EL1). The investigation centers on a representative sample of masonry churches located in Sorrento, a municipality within the province of Naples. The study commenced with the application of the CarTiS first-level form to delineate sub-municipal sectors and classify the buildings according to their structural typologies. Subsequently, the CarTiS second-level form was employed to perform a detailed typological and structural characterization through comprehensive collection of geometric and construction-related data for each church. From this dataset, six churches were selected for an in-depth seismic vulnerability assessment conducted in multiple stages. Initially, the EL1 screening method was applied to facilitate large-scale preliminary evaluation. This was complemented by a more sophisticated analysis employing a macro-element modeling approach via the 3Muri software, enabling detailed assessment of both global and local structural responses. Two critical comparative analyses were then conducted: one between the EL1 acceleration factor and the αSLV coefficient derived from Evaluation Level 3 (EL3), and another comparing the EL1 damage index with damage indices obtained through local mechanism analyses. Although limited by a small sample size, the findings demonstrate a strong correlation across methodologies, validating the simplified EL1 approach as a reliable and efficient tool for preliminary seismic assessment of historic masonry churches exposed to earthquake risk.