PSI - Issue 78

Somayeh Gholami et al. / Procedia Structural Integrity 78 (2026) 1459–1465

1460

and particularly in the central and southern regions such as Campania, the built heritage includes a vast number of unreinforced masonry (URM) buildings that are of cultural and architectural significance (Fabbrocino et al., 2024). Given their wide spreading, assessing the seismic vulnerability of these structures poses a considerable challenge, as detailed engineering analyses (e.g., nonlinear finite element analyses) often require detailed knowledge of material properties, internal layout, and boundary conditions information that is rarely available for heritage buildings (De Angelis et al., 2020, Lourenço, 2006, Lagomarsino and Cattari, 2014, Puncello and Caprili, 2023). To address these issues, the Italian Guidelines on Cultural Heritage (Ministero per i Beni e le Attività Culturali, 2011) introduced a multi-level framework for seismic assessment, where Level 1 (EL1) provides a simplified yet technically sound tool to estimate building capacity at the Limit State of Life Safety (LSLS), utilizing basic parameters such as wall geometry, total seismic mass, and shear strength of masonry. Although not as rapid as EL0 qualitative assessments, the EL1 model provides a mechanically consistent framework for vulnerability evaluation using simplified parameters Zizi et al. (2021). However, their outcomes are sensitive to several key variables including the assumed shear strength of masonry (τ 0 ), plan irregularity factors ( β ), effective resisting wall areas ( A ), mass estimation ( M ), and modal participation terms ( e ∗ , κ ) which may vary significantly depending on geometry, material condition, and construction details. These sensitivities can meaningfully affect the calculated seismic capacity and resulting safety index. In this study, the EL1 model is applied to a group of historic masonry buildings located in the medieval town of Casertavecchia, in Southern Italy. The objective is to evaluate the practical applicability of the model in real-world heritage conditions, highlighting both its potential and its inherent limitations. By working with available geometric and mechanical data, the study provides insights into the seismic capacity of representative unreinforced masonry buildings and discusses the factors that influence the calculated safety index. The study is part of the GENESIS project (Spacone et al., 2025) a national research initiative aimed at protecting historic structures in Southern Italy through advanced seismic assessment and risk mitigation strategies . 2. Overview of the Level 1 mechanical method: The Evaluation Level 1 (EL1) is based on an idealized global failure mechanism in which in-plane shear failure governs the seismic response of masonry walls. It assumes that failure occurs in the weakest direction at the most vulnerable floor. The seismic safety index ( I a , LSLS ) is defined as the ratio between the building's seismic capacity and the expected seismic demand, as per Equation (1): , = , (1) where: • a LSLS is the building’s seismic capacity in terms of spectral acceleration at LSLS, and • a g,LSLS is the design peak ground acceleration (PGA) for a given return period, defined by national codes (e.g., NTC2018(Ministero per le Infrastrutture e i Trasporti, 2018)). The capacity a LSLS is derived from the equivalent elastic spectral acceleration, using the following formulation in Equation (2): , = ∗ (2) where: • F LSLS is shear capacity of the structure (better detailed in the following); • q is behavior factor (which can be assumed in the range 2.25-3.6 depending on building typology and number of stories); • M is the total seismic mass of the building evaluated from the gravitational loads, including both permanent and a portion of variable loads (Equation (3)), in accordance with national standards (Ministero per le Infrastrutture e i Trasporti, 2018).