PSI - Issue 78

Simona Coccia et al. / Procedia Structural Integrity 78 (2026) 1318–1325

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unity — in other words, the difference in maximum rotations — increases with wall height. The significant variability observed in the results highlights the complexity of the phenomenon and reinforces the need for further investigation.

Table 3. Collapse occurrence considering or neglecting the vertical component. H=3m

H=5m H=10m

Collapse occurrence considering the vertical component

40 (50%)

27 (33.75%)

6 (7.5%)

Collapse occurrence neglecting the vertical component ( ϋ g =0 in Eq. (3))

43 (53.75%)

23 (28.75%)

7 (8.75%)

Total analyzed cases

80

80

80

Fig. 5. Ratio between the maximum rotation obtained with (  max1 ) and without (  max2 ) the vertical ground motion for the three considered wall geometries, plotted as a function of the horizontal PGA of the seismic input. Conclusions This study investigated the impact of vertical seismic excitation on the dynamic rocking behavior of free-standing masonry walls through a parametric analysis involving three wall geometries and a suite of natural ground motion records from the 2016 Central Italy earthquake sequence. The main conclusions can be summarized as follows: • The vertical component of ground motion can significantly affect the out-of-plane rocking response of masonry walls, influencing vibration frequency, peak rotation amplitude, and collapse occurrence. • The angle of incidence of the horizontal ground motion also plays a crucial role, with certain orientations amplifying or mitigating the response depending on the interaction with the vertical component. Overall, the findings suggest that vertical ground acceleration, often neglected in conventional seismic analyses, should be explicitly considered in the assessment of masonry structures, particularly in seismic scenarios characterized by high vertical-to-horizontal ( V/H ) PGA ratios. Future developments may involve extending the model to a broader range of wall geometries, accounting for variations in slenderness, height, and thickness, as well as investigating the behavior under one-sided rocking motion subjected to combined seismic inputs. References Berto, L., Favaretto, T., Saetta, A., Antonelli, F., Lazzarini, L., 2012. Assessment of seismic vulnerability of art objects: The “Galleria dei Prigioni” sculptures at the Accademia Gallery in Florence. Journal of Cultural Heritage, 13(1), 7-21. Bozorgnia, Y., Campbell, K. W., 2004. The vertical-to-horizontal response spectral ratio and tentative procedures for developing simplified V/H spectra. Journal of Earthquake Engineering, 8(2), 175 – 207 Bradley, B. A., Cubrinovski, M., 2011. Near-source strong ground motions observed in the 22 February 2011 Christchurch earthquake. Seismological Research Letters, 82(6), 853-865. Chen, W., Wang, J., Dai, K., Hassanein, M. F., Sharbati, R., 2025. Seismic rocking fragility analysis of unanchored nonstructural components under combined horizontal and vertical near-fault ground motions. Journal of Building Engineering, 107, 112645.