PSI - Issue 78

Giuseppe Brandonisio et al. / Procedia Structural Integrity 78 (2026) 2147–2153

2151

The combinations involving seismic force distributions proportional to the vibration modes (Combinations 1–4) are generally more demanding than Combinations 5–8, which use force distributions proportional to the masses. The seismic vulnerability indices evaluated on the global model are lower than those computed on the local models of the individual isolated bodies. For the global model (blue bars in the histograms), the seismic vulnerability index ranges from a minimum value of ζ E,SL-Pushover 3 = 0.648, associated with Pushover 3 (+Y, modal), to a maximum value of ζ E,SLV Pushover 7 = 0.844, associated with Pushover 7 (+Y, mass).

Fig. 4 Pushover curves for the analysed FEM models

The corresponding seismic vulnerability indexes ξ E,SLV are summarised in Table 1 and of Fig. 5.

Table 1 Comparison of the Seismic Vulnerability Indexes

ξ E Body1 Body2 Body3 Body4 Body5 Body6 Body7

Combination

Global model

1 Mode X+

1.134 0.850 0.820 1.170 0.888 1.264 0.859 0.850 1.119 1.023 0.878 0.923 0.778 1.014 0.628 0.866 0.903 0.786 0.977 1.125 1.113 1.464 0.970 0.941 1.151 1.080 1.464 1.217 0.906 1.125 1.059 0.998 1.021 0.759 1.464 1.143 1.028 1.037 0.897 1.411 0.866 0.850 0.778 0.759 0.628 1.264 1.464 1.217 1.170 1.464

1.464 1.464 1.404 1.387 1.464 1.464 1.404 1.387 1.387 1.464

1.222 1.190 1.464 1.464 1.222 1.190 1.464 1.464 1.190 1.464

0.781 0.752 0.648 0.724 0.773 0.811 0.844 0.757 0.648 0.844

2

Mode X-

3 Mode Y+

4 5 6 7 8

Mode Y- Mass X+ Mass X- Mass Y+ Mass Y-

Max Min

For Body 1 (orange bars), the index ranges from ζ E,SLV-Pushover 4 = 0.866 (Pushover 4, - Y, modal) to ζ E,SLV-Pushover 2 = 1.264 (Pushover 2, +X, modal). For Body 2 (grey bars), it varies from ζ E,SLV-Pushover 1 = 0.850 (Pushover 1, +X, modal) to ζ E,SLV-Pushover 5-6 = > = 1.464, associated with Pushovers 5 and 6 (±X, mass). For Body 3 (yellow bars), it ranges from ζ E,SLV-Pushover 3 = 0.778 (Pushover 3, +Y, modal) to ζ E,SLV-Pushover 6 = 1.217 (Pushover 6, -X, mass). For Body 4 (light blue