PSI - Issue 78

Giulia Giuliani et al. / Procedia Structural Integrity 78 (2026) 952–959

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Motion Model (GMM) developed by Sgobba et al. (2021), while the vertical component is derived by applying the vertical-to-horizontal (V/H) spectral ratio proposed by Ramadan et al. (2021). Spectral acceleration in terms of RotD50, representing the median of spectral accelerations across all horizontal orientations, is adopted as the intensity measure (IM) for the horizontal response spectra, as it provides a robust and orientation-independent representation of seismic demand (Boore, 2010). The target spectra derived are reported in Fig. 1, more detail could be found in Giuliani et al. (2025).

a) b) Fig. 1. Response spectra in terms of pseudo-acceleration for a) horizontal and b) vertical component.

To design base-isolated structures, nonlinear dynamic analyses were performed, according to Eurocode 8 provision, with a set of seven three-component ground motion records spectra-compatible with target spectra for each distance scenario. The records are drawn from the same strong-motion database used in the development of the GMMs, ensuring consistency between the target spectra and the selected records. This approach allows for the selection of unscaled ground motions whose spectral content naturally matches the target spectra at the periods relevant to base isolated structures. The selected records for distances of 0 and 5km are listed in Tables 1 and 2, and their spectral responses are compared to the target spectra in Figures 2 and 3.

a) b) Fig. 2. Horizontal (a) and vertical (b) response spectra of the records for R JB =0 km.