Monitoring of Base Isolated Building Subjected to Far Fault Earthquake

Dynamic monitoring of base isolated buildings is analyzed to evaluate structural behavior during earthquakes and gain experience on the specific behavior of rubber isolators. Some structures with seismic base isolation have been monitored during recent strong earthquakes in Italy, namely Amatrice earthquake (2016/08/24, Mw=6.0) and Norcia earthquake (2016/10/30, Mw=6.5) and aftershocks. For these structures, amplification phenomena have been observed up to about twice the accelerations on the superstructure, for very low energy value inputs. In these cases, however, monitoring revealed amplified accelerations extremely small, and very far from being able to damage the structure. Records from the ENEA permanent accelerometric network, installed on these structures, and the tests carried out on the same isolators during qualification tests of the same rubber isolators positioned below the analyzed structure, describe the behavior of the isolators in terms both of force and displacement defining two non-linear laws, for small and large displacement, derived from experimental data.