PSI - Issue 78

Ciro Canditone et al. / Procedia Structural Integrity 78 (2026) 379–386

384

This scenario proved to be, as expected, a quite destructive one, with collapse quickly occurring at 1.9 s due to the occurrence of axial- bending failures within the Loggia’s base piers and the columns of the arched passageway (Figure 5a). The main façade detached from its side walls at 2.3 s, with failure planes being located along the pre-existing cracks implemented within the model (Figure 5b). This produced, in turn, the complete loss of support for the vaulted ceiling system, which completely collapsed, leaving only some residual stumps at their springing sections (Figure 5b). Hence, in this scenario, collapse of the whole Loggia was observed by the end of the analysis. Analysis results under corner scenarios are depicted in Figure 5. With regards to the corner scenario involving L x /12 and L y /12, foundation-level failure leads to the spread of cracking within the corner itself, as well as within the rising barrel vault and at cross- vaults’ springing (Figure 5a), due to support displacement. Eventually, the barrel vault sagged due to relative displacements between the Loggia’s transverse walls , before debris impact induced by the partial collapse of a cross vault (Figure 5b) triggered the barrel vault’s complete collapse (Figure 5c). In the corner scenario involving L x /6 and L y /6, lack of support translated into the corner base macro-element detaching from the rest of the structure (Figure 5d), hence leading to an increase in axial-bending demand on the leftmost column of the lower colonnade. This, in turn, led to support displacements for both the barrel and cross vaults; changes in their geometrical configuration caused an increase in horizontal thrust, and hence in the façade and flange walls’ OOP displacements. Eventually, this triggered axial-bending failure of the leftmost column and partial collapse of the rising barrel vault (Figure 5e). Increases in vault thrusts also favoured the occurrence of an overturning mechanism for the upper columnade, favoured by the presence of pre-existing cracks, hence leading to complete loss of support and collapse of the vaults (Figure 5f). Hence, the final volume involved in the collapse included not only the whole elevation of Loggia’s corner, but also the whole vaulted system. A similar collapse sequence was also observed under the corner scenario involving L x /3 and L y /3 , so it is not be discussed in detail here. (a) (b) (c)

L x /12 – L y /12

0.50 s

13.15 s

15.00 s

(d)

(e)

(f)

4.00 s

9.05 s

12.75 s

L x /6 – L y /6

Figure 5. Progressive collapse sequences under corner foundation-level failure scenarios.