Seismic Retrofit of Existing Buildings by Means of Seismic Isolation: Some Remarks on the Italian Experience and New Projects

Abstract eng:
Seismic isolation (SI) has been used in Italy for several applications, which include important retrofits of civil structures and cultural heritage. Some new hospitals, all new civil defence centres and most new schools have already been (or are being) isolated, together with a significant number of dwelling buildings and other constructions. The 2009 Abruzzo earthquake caused an increase of the number of the Italian isolated buildings from about 70 to over 300. Prior to the aforesaid event, the Italian SI systems consisted in High Damping Rubber Bearings (HDRBs) or Lead Rubber Bearings, to which plane surfaces steel-PTFE Sliding Devices (SDs) were added in the last years. Now, Curved Surface Slider devices are also in use. The first Italian building to be retrofitted with SI was a reinforced concrete (r.c.) civic centre in Naples in 2004. Its foundation pillars and walls were cut, approximately 600 HDRBs were installed and a steel beams floor was added above the isolators to stiffen the superstructure base as necessary. In the same year, two 4-storey r.c. dwelling buildings were retrofitted, each with 12 HDRBs and 13 SDs, in Solarino, near Syracuse. In 2005 the first European retrofit with SI in a sub-foundation was completed: it concerned a 3-storey r.c. house in Fabriano that had suffered severe but non-structural damage in the 1997-98 Marche & Umbria quake. For this intervention 56 HDRBs were used. Further retrofits with SI were also performed for churches, schools, further dwelling buildings, tanks, single masterpieces, etc. The significant extension of the use of SI after the Abruzzo quake concerns this and other Italian regions. The new applications include numerous retrofits: at L’Aquila they mainly concern civil and monumental buildings damaged by the quake. In the latter, the SI system will be inserted in a sub-foundation, not to cut the structural elements or existing foundations, and a new method patented by ENEA and Polytechnic of Torino in 2010 will also be used.

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