PSI - Issue 78

Caterina Balletti et al. / Procedia Structural Integrity 78 (2026) 1823–1830

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and emergency areas (Giuliani et al., 2020), as well as choice, which, with higher numbers, indicates the potential of a spatial element to be on the shortest paths connecting all others and is important for predicting evacuation and access flows (Giuliani et al., 2020). To process the indicators, street segments were converted into axial lines to represent all navigable pedestrian routes in the layout. To increase accuracy, the calculation incorporated angular measures and weighted segment length, as such parameters have been shown to correlate strongly with movement patterns, especially in historic centres characterised by narrow and winding streets (Hillier & Iida, 2005; Turner, 2007; Giuliani et al., 2020). The analysis was enriched by introducing additional variables related to physical vulnerability, in accordance with UNDRR (2009) definitions, such as street width (measured at the narrowest point using orthophotos to a 0.1m precision), slope, the presence of stairs, and blockage elements (such as underpasses, rails, and supports). These data were processed within QGIS, by combining the normalised value of each variable. The vulnerability index was defined as a weighted average of these variables. Streets with reduced width, increased numbers of blockage points, presence of stairs, or significant slope were categorised as more vulnerable to seismic hazards, especially given their diminished accessibility for people with reduced mobility and the increased likelihood of obstruction during earthquakes. This comprehensive vulnerability measure was then combined with normalised integration and choice values, similarly to the study of Giuliani et al. (2020), to suggest possible intervention priorities - respectively, strategic facilities and emergency areas and the most strategic paths for evacuating. Fig. 8 shows preliminary results for the case study.

Fig. 7 Seismic capacity in terms of return period of: (a) masonry buildings; b) a portion of the castle.

Fig. 8 First outcomes of the analysis of street network