Optimum control of energy dissipation in support-pendulum seismic isolation system for large NPP equipment

Abstract

The paper presents the results of theoretical and experimental investigations of support-pendulum seismic isolation (SPSI) system, designed for protection of large NPP equipment against seismic, shock and vibration loads. SPSI is a set of separate supports, the composition of which includes pendulum bars with special fastener assemblies and plastic damper in the form of rod steel elements system.Full-scale seismic SPSI testing had been conducted on the Russia’s largest seismic platform ВСС-300. The tested SPSI had three supports, on which a 40-ton mockupup of NPP equipment had been installed. Mockupup size was 4.6×3.7×6.8 m. The testing reproduced three-component load input which corresponds to seismic input, intensity of which exceeded 9 as per the scale MSK-64. Decreasing horizontal accelerations and speeds on the NPP equipment mockupup were approximately 2 times, the amplitude of horizontal displacement had increased on 20% approximately. Relative horizontal displacements of the mockupup were of quick-damped vibrations type that demonstrates the efficiency of using plastic dampers in the form of deformable rods.The procedure for design and selection of rational damper structural parameters includes searching the optimal parameters of viscous damping for linear dynamic model on the basis of construction of spectral density of seismic input power and selection of for the damper, ensuring damping, equivalent to optimal viscous damping. Purpose-oriented function of optimization is the minimum of dispersion of seismic isolated object accelerations. This experiment had confirmed the correctness of damper structure choice procedure for provision of the required dissipation level.