Forced vibration test of BWR type nuclear reactor buildings considering through-soil coupling between adjacent buildings

The forced vibration test on two adjacent BWR type reactor buildings in the Hamaoka Nuclear Power Station, Chubu Electric Power Co., Inc., was carried out in 1977. The experiment on No. 1 reactor building had been made in 1973 and 1974 to evaluate the dissipation of vibrational energy to the earth. In 1977, No. 2 reactor building was under construction and nearly completed adjacently to the No. 1 reactor building, in which the reactor has been in operation since 1975. Three large vibration exciters with maximum exciting force of 150 tons each were installed on the 5th floor of the No. 2 reactor building, and the vibration ranging from 1 to 20 Hz was applied to the building in north-south, east-west and vertical directions. For obtaining the responses of the buildings, 24 and 33 pickups were placed on the floors of No. 1 and No. 2 buildings, respectively, and 17 dynamic earth pressure cells buried under the foundation of the No. 2 building were also employed. The natural frequency, viscous damping ratio and natural mode were analyzed by the regression analysis of many degrees of freedom, using the resonance curves with complex forms and many peaks. The vibrational behaviors of two adjacent reactor buildings coupled through the earth were given as the result of experiment. (J.P.N.)