Investigation on dynamic response with foundation uplift

In order to rationalize the aseismatic design of nuclear power stations, it is necessary to elucidate the characteristics of effective input when the earthquake motion for the design is inputted in the foundations of nuclear power stations. In this study, among the research subjects concerning the reduction of effective earthquake input, regarding the uplift of foundations, its response characteristics and the method of the rational evaluation of earth contact ratio were experimentally examined, and the method of analysis which can evaluate the damping effect due to the uplift was proposed. The experimental method is reported. It was found that accompanying the uplift of foundations, vertical motion was induced, and horizontal motion showed nonlinear response. It was confirmed that the nonlinear response accompanying the uplift can be approximately evaluated by the conventional analysis technique using the S-R model. The current equation for evaluating earth contact ratio is adequate for a soft ground model, and tends to undervaluate for a hard ground model. The S-R analysis model introducing the experimentally obtained characteristics in the dampling coefficient of a nonlinear rocking spring was newly made. (Kako, I.)