Behaviour Of Seismic Isolated Building During Central Italy 2016 – 2017 Earthquakes

The seismic sequence during years 2016 and 2017 involved a great area In Central Italy, involving four regions and more than 100.000 buildings. Many main shock events occurred, namely Amatrice earthquake (Mw 6.0 on August 24th, 2016), Valnerina earthquakes (Mw 5.9 and 5.4 on October 26th, 2016), Norcia earthquake (Mw 6.5 on October 30th 2016), and Montereale – Capitignano earthquakes (Mw 5.0, 5.5 on January 18th 2017) About 80.000 buildings were damaged in the seismic events. In particular, some areas were involved also in the 2009 seismic events (L’Aquila earthquake). After L’Aquila earthquake, during reconstruction period, many buildings with base isolation (both existing and new ones) have been realized in the city area. Furthermore, collapsed buildings, or heavily damaged buildings, were demolished and reconstructed with base isolation (both in foundation and above first elevation columns). The isolation systems were generally composed by both rubber high damping isolators, and plane friction isolators (sliding). Some buildings, which reported less structural damage during 2009 L’Aquila earthquake, were retrofitted with isolation systems, both with rubber high damping isolators, and plane friction isolators. All these isolated buildings were completed before year 2016, that is before the new strong seismic events in Central Italy. Several different dynamic and seismic behaviour were observed in those buildings, depending upon isolation system (noticeable differences have been observed between curved sliding isolators and rubber high damping isolators) and upon soil – structure interaction. Significant displacement has been observed caused by soft soil, and inverse velocity seismic soil profile. Also, frequency response influenced isolated building behaviour. In the work several buildings are examined, analysing the seismic behaviour both in the 2009 earthquake (with no isolation system) and during 2016 – 2017 seismic events (with isolation system).