Experimental and analytical studies of a deeply embedded reactor building model considering soil-building interaction. Pt. 2

This paper describes the dynamic characteristics of a deeply embedded reactor building model revealed from the forced vibration tests, earthquake observation and the simulation analyses. The outline of the whole experimental studies and the vibration test results were discussed in the previous report Part I in 1979, in which authors confirmed that the analytical results obtained using mathematical model of a soil-building interaction system had agreed quite well with the results of the forced vibration tests performed before backfill. In this paper, the results of simulation of forced vibration tests after backfill are presented, and are compared with those before backfill to investigate the embeddment effects on the dynamic characteristics of a soil-building interaction system. This system can be represented by a lumped mass model, in which soil medium in the three-dimensional domain with viscous boundary is assumed same as the former case to consider the energy dissipation due to the wave propagation outward the modeled soil domain. One of the assumptions additionally taken for the backfill is to include the backfilled sand in the analytical model of soil-building system. Another one is that the value of frequency-dependent rocking spring used in the analyses of the forced vibration tests before backfill is multiplied by 1.5 considering an increase in stiffness due to backfill. The calculated results shows a good agreement with test results in regard to the resonance and phase lag, and the following conclusions are derived from the series of forced vibration tests and simulation analyses. (orig./RW)