RETROFIT OF EXISTING BUILDINGS WITH SEISMIC ISOLATION: DESIGN ISSUES AND APPLICATIONS

The application of seismic isolation for new buildings is quite easy and almost always possible. It is also economically convenient, at least in medium and high seismicity areas both for reinforced concrete buildings and masonry buildings. Actually, the real challenge of seismic isolation is protection of existing buildings, especially in countries where maintenance of old structures is an important issue. It is worth reminding that, when using base isolation, the period of vibration can be chosen so as to allow input of low spectral amplitude, while the superstructure remains substantially in the elastic range. This possibility also allows for limiting or even avoiding the conventional retrofit intervention in the superstructure. In this paper the design issues for the application of base isolation in the retrofit of existing buildings are first discussed for the two cases of reinforced concrete and masonry buildings. These refer to the positioning of the isolation devices in plan and elevation and the transferring of the vertical actions during the building phases. Then the most relevant applications in Italy for existing reinforced concrete and masonry buildings are also shown. Finally, an isolation system is presented, which was set up for cultural heritage structures but is very suitable also for industrial plants.