Seismic isolation is today largely used as passive mitigation system for seismic actions. While this technique can be easily implemented in new structures, more difficult, whenever possible, is the implementation in existing buildings, that can become a real challenge especially in countries where maintenance of old structures, sometimes of historical importance, is an important issue, such as Italy.

The use of seismic isolation in existing buildings presents interesting features. Using a base isolation system, the period of vibration can be chosen in order to allow input of low spectral amplitude, so that the superstructure can substantially remain in the elastic range. This possibility allows for limiting or even avoiding the conventional retrofit intervention in the superstructure. In fact, the intervention can be concentrated at the lowest level, while no intervention is necessary in the superstructures, so that it is not necessary to demolish non-structural elements.

As a result, an “operational seismic retrofit” would be possible, that is the superstructure could remain operative during the retrofit works. In order to do that, at least a safety degree not lower than the existing one should be guarantee. This can be obtained by using temporary fixing systems for the isolation devices or temporary structure for the columns.

After a brief overview on the available researches in this field, the paper proposes and discuses different solutions for “operational seismic retrofit”, pointing out also the convenience in terms of costs. Furthermore, a case of study is presented, in which some solutions are implemented.