Recent development and application of seismic isolation and energy dissipation and conditions for their correct use

More than 23,000 structures, located in over 30 countries, have been so far protected by passive anti-seismic (AS) systems, mainly by the seismic isolation (SI) and energy dissipation (ED) ones. The use of such systems is going on increasing everywhere, although its extent is strongly influenced by earthquake lessons and the features of the design rules used. As to the latter, SI is considered as an additional safety measure (with consequent significant additional construction costs) in some countries (Japan, USA, etc.), while, in others (including Italy), the codes allow to partly take into account the reduction of the seismic forces acting on the superstructure that is induced by SI. Applications of the AS systems have been made to both new and existing civil and industrial structures of all kinds. The latter include some high risk (HR) plants (nuclear reactors and chemical installations). The applications in a civil context already include not only strategic and public structures, but also residential buildings and even many small private houses. In Italy, the use of the AS systems has become more and more popular especially after the 2009 Abruzzo earthquake (nowadays more than 400 Italian buildings are seismically isolated). Based on the information provided by the authors at the ASSISi 13th World Conference, held in Sendai (Japan) in September 2013, and on more recent data, the paper summarizes the state-of-the-art of the development and application of the AS systems and devices at worldwide level, by devoting particular attention to SI of buildings in Italy, in the context of recent seismic events. Moreover, it outlines the benefits of the aforesaid systems for ensuring the indispensable absolute integrity of strategic and public structures, as, primarily, schools, hospitals and HR plants, but also (for an adequate protection of cultural heritage) museums. Finally, based on Italian experience, it provides some remarks on costs of SI, stresses the conditions for the correct use of this technique and mentions some recent initiatives of the Italian Parliament to ensure such a correct use and to widely extend such an use to the HR chemical plants too (for which only very few applications already exist in Italy).