Effectiveness of HDRB isolation systems under low energy earthquakes

摘要

The experimental seismic behaviour of an isolation system, made of high damping rubber bearings, under low energy earthquakes is analysed. The seismically isolated building was instrumented by means of an accelerometer network. It was first characterized dynamically using also fifteen seismometers to record ambient vibrations. Then, all the events of the seismic sequence that struck Central Italy from August 2016 to January 2017 were recorded. These allowed evaluating the effects of earthquakes with different energy on the structure. Due to the long distances from the epicentres of these events, the analysis referred to the behaviour for very low shear strains in the rubber. The resonance frequencies of the base isolated building were much higher than those supposed in the design phase, but the filtering effect was still effective. One of the relative displacement history recorded during the strongest event was applied to the same devices used for the type tests at the construction time. The results obtained in terms of isolator stiffness were consistent with the experimental ones.