First seismic retrofit by base isolation of a strategic building in use implemented in Umbria

The issue of mitigating the seismic vulnerability of public and strategic buildings is of fundamental importance. Current regulations require the achievement of seismic adaptation of the structure and performances compatible with the full operation. It is also fundamental to maintain operational conditions during construction works. An appropriate design strategy allowing such scenarios can be represented by seismic base isolation. It consists in decoupling the superstructure from the substructure (integrated with the ground) reducing the response accelerations up to 10 times compared to those in the ante-operam (fixed base) conditions. Reducing the seismic action on the structure also allows the protection of the contents with the removal of the damage states (“Near Zero Damage”), a relevant aspect for a strategic building. The strategy can also avoid the evacuation of the occupants, and the contents functional to the operational activities carried out, during the works. In fact, the intervention is generally characterized by a concentration of the construction site activities in the basement without further interventions in the rest of the structure. Offices and workrooms are not directly affected by limitations or interferences, thus allowing their full use. The paper illustrates the emblematic seismic retrofitting by base isolation of a strategic building located in Perugia (Central Italy). The full seismic retrofitting of the building is achieved together with the removal of potential damage to non-structural elements and contents. The required works allowed the full use of the building and its functionality.