Seismic incidence on base-isolated nuclear power plants considering uni- and bi-directional ground motions

Abstract

The effects of bi-directional ground motions of the input seismic on base-isolated Nuclear Power Plants are investigated by comparing to the responses under uni-directional ground motion. For this aim, an analytical model is used to calculate the incidence angle (IA) of ground motions that vary from 0 to 360 degrees, with the interval of 15 degrees, and to show their effects on diverse engineering demand parameters. The observed responses corresponding to the displacement, the rotation and the element force are determined. In addition, the critical angles of the structure under two components with respect to one component are obtained. It is found that the maximum responses of the base-isolated structure for individual records may be decreased at some angles while increased at other angles. In case of bi-directional ground motions, the effect of IA is less considerable than uni-directional ground motion. Moreover, the critical responses under bi-directional seismic excitations are more adequate than uni-directional one. The displacement and shear force responses from one component are less than corresponding values from two components.