Experimental Validation of RE-Centering Capability Evaluation Based on Energy Concepts

Abstract eng:
Present Norms do not furnish an acceptable approach of general validity to evaluate the re-centring capability of seismic isolation systems and none of them is based upon solid theoretical fundamentals, but rather, make reference to empirical approaches. This author developed a theoretical approach to this problem, suggesting an energy-based criterion for its quantification, that also incorporates praiseworthy simplicity. It just involves the comparison of two calculable and measurable physical magnitudes, namely the elastically (or, better said, reversibly) stored and the irreversibly dissipated earthquake energy input. The newly proposed criterion was accepted for an oral presentation at the 13th World Conference (Vancouver, 2004) and since then gained an increasing consensus among the technical and scientific community. The validity of the new criterion has been confirmed by the results of several hundreds of step-by-step non-linear analyses conducted on real cases, as well as by a degree thesis at the University of Padua (Italy). Its experimental validation occurred only recently within the framework of the LESSLOSS Research Project funded by the European Commission, which lasted three years (2004-2007). Over 200 trials were conducted in two distinct testing campaigns at the shake-table facility of ENEA Casaccia near Rome. The results have fully substantiated the method for evaluating the re-centring capability of seismic isolated systems based on the energy approach. The scope of this paper is that of illustrating the testing program and reporting in detail the results thereof, as well as commenting on the blatant discrepancies with the criteria adopted in some international Norms.

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