Innovative technologies for the vibration control of equipment in critical facilities

The present thesis settles in the framework of the dynamic modelling, seismic mitigation and permanent health monitoring of equipment in critical facilities. The main objective is to assess the feasibility and the effectiveness of innovative mitigation Technologies including: the passive isolation of a single equipment (equipment isolation systems); the passive isolation of a raised floor, on which a group of several equipment is anchored (isolated raised-floor systems); a non-conventional Tuned Mass Damper (TMD), realized by converting a large mass already present on the structure, e.g. the mass of an equipment, into a tuned mass, in order to reduce the structural response. The area of research is believed to have the potential for a wide application, since a still limited number of authors has addressed the theoretical and technical issues associated with the seismic design and protection of equipment. As a result, international seismic codes and standards also appear to be inadequate in this regard. Furthermore, the proposed technologies give the opportunity of addressing topics of significant scientific interest: the analysis of the dynamic interaction between an equipment and its supporting structure, generally neglected in current Literature and seismic codes; the definition of reduced-order generalized models, introduced for design purposes; the constitutive modelling of nonlinear hysteretic isolation systems; the dynamic analysis of non-proportionally damped systems and nonlinear hysteretic systems; the stochastic analysis of the dynamic response, given the probabilistic nature of the earthquake excitation; the proper definition of energy indices to assess, in a synthetic and effective way, the performance of the proposed mitigation technologies. A distinctive aspect of the work is eventually given by the use of shaking table tests on reduced scale models, for the sake of dynamic identification and seismic analysis. In the end, the thesis aims at defining criteria and methodologies to harmonize the seismic design of equipment with the one of the structure, in a joint and coordinated effort to achieve the operational performance objectives prescribed to critical facilities by international seismic codes.