OBSERVED SEISMIC BEHAVIOR OF A HDRB AND SD ISOLATION SYSTEM UNDER FAR FAULT EARTHQUAKES

The behavior of a reinforced concrete building, seismically isolated with High Damping 14 Rubber Bearing (HDRB) and Sliding Devices (SD), observed during the most important events of 15 the seismic sequence that struck Central Italy from August 2016 to January 2017, is analyzed. Due 16 to the epicenter distances, all the events had quite light effects at the site, so the isolation system was 17 not always put in action. A previous very low energy earthquake and the ambient vibration analysis 18 are used for comparison. The study of the isolation system response is first carried out and the var-19 iability of the resonance frequencies with the input energy at the site is pointed out. These frequen-20 cies are quite close to those of the superstructure considered as fixed base. Small cracks were ob-21 served after the sequence in some partition walls of the building. The analysis of the superstructure was done by means of a finite element model, assuming a non-linear model for the isolators, based 23 on previous experimental data. The importance a suitable decoupling between the superstructure 24 and the ground and the contribution of the sliding devices under low energy earthquake is pointed out.