PSI - Issue 78

Roberta Di Chicco et al. / Procedia Structural Integrity 78 (2026) 497–504

498

1. Introduction Earthquakes represent a severe threat to the safety of cities and their communities, as even moderate events can cause devastating economic and social consequences. Recent seismic events in Italy have highlighted the vulnerability of historic centres , which constitute a significant portion of the nation’s architectural heritage. This fragility stems from multiple factors, including the age of construction, the lack of adequate seismic design, and insufficient maintenance over time. Seismic risk exposure in Italy is further exacerbated by high population density and, above all, the concentration of valuable historical assets (Sorrentino et al., 2019, Dolce et al., 2021). Masonry buildings in historic centres are often arranged in aggregates. These structures were built in continuity one to each other using traditional techniques, involving heterogeneous masonry types (e.g. multi-panel walls with rubble infill) and poor construction details (e.g. weak connections between perimeter walls or between walls and floors), which frequently result in significant vulnerabilities. Moreover, due to their historical development, masonry aggregates are often characterised by complex structural systems and geometrical irregularities (Valente et al., 2019). For instance, the presence of adjacent buildings with differing number of storeys and inter-storey height within aggregates can lead to irregular dynamic behaviour and localised stress concentrations under seismic loading (Pinasco et al., 2025). For all these reasons, the seismic assessment of masonry aggregates within historical centres is an open and challenging issue and, thus, several approaches have been developed in recent decades. In current literature, empirical, analytical-numerical and hybrid methods are traditionally identified. The first are large-scale approaches based on statistical processing of post-earthquake data leading to the definition of vulnerability classes based on building key typological and structural features. In this perspective, the CARTIS survey form (Zuccaro et al., 2015)- developed in the framework of the Italian DPC-ReLUIS project- represents a useful tool to detect structural types in homogeneous urban sectors and it can be used within the well-known vulnerability-index based procedures (e.g. Benedetti and Petrini, 1984, Milutinovic et al., 2003, Formisano et al., 2015, Di Chicco et al., 2024, Amitrano et al., 2025, Pianese et al., 2025). On the other hand, numerical methods involve simulations on structural models to relate a building’s characteristics to its seismic response, leading to the derivation of vulnerability functions that correlates structural capacity with seismic demand. (e.g. Angiolilli et al, 2021, Acito et al., 2023, Di Trapani et al., 2024). Nevertheless, although the seismic behaviour of such structures has been widely studied, certain methodological gaps remain, particularly regarding the so-called "aggregate effect" and the combined consideration of in-plane and out-of-plane failure modes. Within this general framework, the present study proposes a multi-scale analysis of the historical residential building stock in Lavello (PZ), a small town located in the Basilicata region of southern Italy. The structural characteristics of the building stock were collected using the CARTIS form. A taxonomic classification of the aggregates was performed in parallel with an analysis of the urban evolution of the historic fabric. The investigation then moved to the building scale, where non-linear static analyses were conducted on a macro-element model of a prototype aggregate-developed using the 3Muri software-with the final aim of deriving seismic vulnerability curves for building aggregates at the municipal level. 2. Analysis of the municipality of Lavello (PZ): the CARTIS procedure Lavello is a small municipality located at 313 m above sea level in the middle valley of the Ofanto river, at the northernmost edge of the Basilicata region. The town has a population of approximately 13,000. Over the centuries, Lavello has been impacted by major seismic events, including the 1851 and 1857 Vulture earthquakes, the 1930 Irpinia earthquake and the 1980 Irpinia-Basilicata earthquake. These events led to its formal designation as a seismic-prone zone in 1981. It is classified as seismic zone 2 (medium-to-high seismicity) according to the current national seismic zoning system. The town has very ancient origins, as demonstrated by the discovery of remains from an Iron Age village and the historical urban development traces back to the Daunian-Roman settlement of “ Forentum ” . The configuration of the historic centre dates to the medieval period and developed around the urban poles of the Mother Church and the Ducal Palace; the latter currently serves as the city hall. The site presents a complex topography with distinctive morphological traits. The initial urban core was founded on a steep ridge carved by the upper branches of the stream, but subsequent urban expansion extended significantly on flat land to the south-west. Understanding the genesis of the building fabric is fundamental for the development of exposure