Seismic performance upgrading of containment structures using a negative-stiffness amplification system

As an efficient and crucial energy-generation facility, a nuclear power plant requires a high level of seismic safety as its failure can lead to catastrophic events. In this study, a novel negative-stiffness amplification system-strengthened isolation system (NSAS-IS) is constructed for seismic performance upgrading of containment structures. Moreover, a multiperformance-oriented design principle is developed for the NSAS-IS to enable enhanced energy dissipation and robust control during multi-intensity seismic excitations. The NSAS-IS comprises an NSAS and parallelly arranged isolators; in particular, the NSAS comprises a tuning spring in series with a sub-configuration including a negative-stiffness device and dashpot in parallel. Herein, the mechanical models and physical realization of the NSAS and isolators are established, based on which the equivalent negative-stiffness effect and enhanced energy dissipation capacity are elucidated. A mechanical model of an NSAS-IS-equipped containment structure, as the last safety defense of the inner structure of a nuclear power plant, and its governing equation and finite element model are established. A design principle, aimed at multiperformance upgrading, is developed for the NSAS-IS. Considering the typical containment structure as an example, the advantages of the proposed NSAS-IS and design principle are investigated for multiple seismic performances, including the deformation and shear force responses of the isolation layer as well as the deformation and acceleration responses of the containment shell. The results obtained indicate that installing the NSAS-IS at the bottom of the containment structure provides improved isolation owing to the equivalent negative-stiffness effect; consequently, the multiple responses of the superstructure and isolation layer are reduced more significantly than with conventional isolators. Benefiting from the multiperformance-oriented design and deployed NSAS, the new isolation system exhibits an enhanced energy dissipation efficiency and capacity, simultaneously maintaining the isolation phenomenon. Thus, the total energy dissipation burden on the primary structures can be relieved by the NSAS, which robustly dissipates intense vibrational energies during multi-intensity excitations.