EXPERIMENTAL AND NUMERICAL DETERMINATION OF THE DYNAMIC PROPERTIES OFTHE REACTOR BUILDING OF ATUCHA II NPP

Determination of the dynamic properties of the reactor building of Atu cha II NPP is carried out in order to: (i) obtain valuable information for seismic qualification of the plant and (ii) access some procedure s for testing and analysis that are used in the process of seismic eva luation of existing nuclear facilities founded on Quaternary soil depo sits. Both steady state and impulsive dynamic tests were performed but attention is centered here in the techniques used to determine natura l frequencies and modal damping ratios with impulsive tests. Numerical analyses were performed by means of a 3-D model of the superstructure together with foundation stiffness coefficients derived in a separate paper from steady state vibration tests, and also from analysis with a 2-D FE model of the soil layers capable of approximating the 3-D fea tures of the problem. The computed foundation stiffness coefficients a re compared both with those obtained from the tests and from an axisym metric FE model: results indicate that foundation stiffness coefficien ts calculated with FE models with soil parameters given by laboratory tests performed on cored samples are significantly lower than those gi ven by the steady state vibration tests. (C) 1998 Published by Elsevie r Science S.A. All rights reserved.