PSI - Issue 78

Maria Eleonora Pipistrelli et al. / Procedia Structural Integrity 78 (2026) 1911–1918

1914

Figure 2: (a) schematic representation oof the historical evolution of the aggregate; (b) schematic representation of the portion of the aggregate that underwent reinforcement interventions.

Between 2004 and 2006, the Province of Perugia conducted a series of reinforcement interventions on the building aggregate. Based on the vulnerabilities identified, a set of intervention strategies was proposed. These included local consolidation of the foundations, confinement of selected openings with steel frames, injection grouting and extensive masonry repairs, use of steel tie rods to counteract lateral thrusts, and the complete removal of heavy or moderately heavy suspended ceilings. These measures were specifically planned for critical areas, as shown in Fig. 2-b. However, the proposed interventions were never implemented for the north-east corner building. 2.2 The north-east corner The historical analysis confirms that the north-east corner has been part of the aggregate since its earliest development phase. However, it underwent several uncoordinated vertical expansions during the 19th and 20th centuries, disconnected from the structural logic of the adjacent parts. This lack of integration has been further compounded by the irregular distribution of past reinforcement interventions across the aggregate (see Fig. 2-b). Among all the sections of the complex, the north-east corner exhibits the most severe and concentrated damage. The Level 1 AeDES form filled out after the 2016 seismic events by the Province of Perugia classified the first and second floors of this corner unit as uninhabitable, in contrast to the adjacent portions, which remained largely accessible. This differential behavior clearly points to distinct structural performance, supporting the interpretation of the corner as an independent seismic unit. A crack pattern survey was developed for this corner portion (Fig. 3), based on in-situ observations. Diagonal cracks on the north and east façades suggest in-plane shear failure, while signs of out-of-plane instability indicate an incipient mixed overturning mechanism. These phenomena are likely exacerbated by poor wall-to-floor connectivity. Vertical cracks at the interfaces with adjoining buildings highlight the absence of effective structural integration, reinforcing the interpretation that the north-east corner responds independently under seismic loads. A particularly critical element is the arch on the north façade, likely built for slope stabilization. It appears disconnected from the masonry wall and inadequately counters horizontal thrusts, as evidenced by cracks along its extrados and in the keystone. The already compromised condition of this unit has been further worsened by the 2013 landslide affecting the eastern slope of the hill.