PSI - Issue 78

Elisabetta Bersanetti et al. / Procedia Structural Integrity 78 (2026) 372–378

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Fig. 2 Building façade with the devices located under masonry pier (red arrow represent load

For the limited areas lacking a basement level, it was necessary to create a technical void below the floor slab to allow for the placement of the devices and the construction of a new overhead slab. Preliminary simulations were carried out to identify the number and positioning of the devices to be installed. These simulations considered both “friction pendulum” type isolators and a solution using elastomeric isolators combined with sliding devices. According to paragraph C7.10.1 of Circular 9/2019, an isolation system is considered effective when it increases the fundamental period of the fixed-base structure by at least a factor of 3. For the building in question, the fundamental period of the fixed-base structure is approximately 0.75 seconds; thus, the isolation period Tis must be at least 2.35 seconds. A target period of 2.7 seconds or greater was therefore selected, in order to limit the seismic forces transmitted to the superstructure and control displacement demands. A numerical model was then implemented including the devices needed to ensure proper load transfer from the overlying masonry to the discrete supports provided by the isolators. The placement took into account the layout of openings and piers, positioning the devices directly beneath the latter.

Fig. 3. Isolators and sliders floor (red for sliders, blue for isolators)

Fig.4 Response spectrum

The layout was designed to concentrate horizontal stiffness along the external perimeter, without limiting it exclusively to those zones. Given the presence of internal courtyards, part of the stiffness have been distributed across interior zones, promoting a more homogeneous isolation response. The average spacing between isolators is approximately 4,5 meters.