Self-centring Capability Evaluation of Seismic Isolation Systems Based on Energy Concepts

摘要

It was not until the most recent years that self-centring capability was identified as a fundamental function of an isolation system. This tardy occurrence can perhaps be explained by the fact that, historically, the first seismic isolators were simple rubber bearings - which are endowed with an optimal self-centring capability. With the introduction in the market of other types of isolators, that are generally not fitted with an intrinsic self-centring capability, the problem of providing this function has re-asserted its vital role. Notwithstanding, the latter was never paid sufficient attention by seismic engineering experts, to the point that the formulation of a criterion to quantify it was only acknowledged for the first time in 1991 by the AASHTO Guide Specification for Seismic Isolation Design. Then other criteria were developed, but none of them is based upon solid theoretical fundamentals, but rather make reference to an empirical approach, valid for only one class of devices. The scope of this document is that of attempting a first theoretical approach to the self-centring problem of seismic isolation systems, suggesting an energy-based criterion for its quantification, without pretending to exhaust the subject nonetheless.