Large-scale experiment of floating seismic isolation system

Yamamoto, Tomohiko  ; Imai, Yoshiyuki  ; Marufuji, Takato; Akasaka, Naoaki; Yan, X. ; Otani, Akihito*; Kai, Satoru*; Mori, Takashi*; Uoji, Tomoki*; Ueno, Tomohiro*; Motegi, Haruki*; Fukui, Hirohisa*; Sato, Eiji*; Nakamura, Izumi*

A new seismic isolation concept called Floating Seismic Isolation System (FSIS) has been proposed that is designed to reduce both horizontal and vertical earthquake motions. The 3-dimensional seismic isolation system is primarily intended for SMR-class nuclear power plants. The FSIS is essentially a floating platform structure that embeds a number of air cavities and orifices at the bottom. In principle, the cavity acts to reduce peak vibration response of the structure to vertical seismic input whereas the orifice adds damping for residual vibration reduction. In our past studies, the vertical excitation tests using a small-scale model simulating a floating seismic isolation building were carried out. The test results showed that the air cavities and the orifices can reduce the response of the structure to vertical seismic motions and that the seismic isolation and damping effects due to the structure are significant. In the present study, the authors conducted a series of large-scale shaking tests using the 3D Full-Scale Earthquake Testing Facility called "E-Defense" in Japan. The experimental model is a 1/15 scale mockup down-sized by similarity from a FSIS-paired SMR plant design for floating in a pool. The objective of the experiment is to produce a complete set of data required for verification of the system performance and for validation of the analysis methods for the design of FSIS-paired SMR plants. This paper describes the similarity design of the large-scale experiment, the series of shaking tests performed, and the key measurements.