Wave scattering effect in soil-structure interaction

The authors have developed the nonlinear soil-structure interaction analysis program HASSI-8 which was completed by implementing the capabilities to consider both spatial variations of the free-field ground motions and wave scattering into HASSI-7. A typical PWR reactor building with embedment depth equal to its foundation radius on soft to stiff soil was analyzed using the above both programs. If spatial variations of free-field ground motions and wave scattering effects were neglected, the transfer function of the reactor building amplifies high frequency components anomalously and tends to give large acceleration response and the near-field soil measured at the ground surface showed anomalous response when the shear wave velocity of the foundation soil decreases to show the wave length close to the dimension of the foundation structure embedded by the same amount of depth equal to its radius. The current PWR reactor buildings having similar dimensions and dynamic characteristics to the numerical model adopted here and having been constructed usually on the foundation rocks of which shear wave velocities are larger than 1,000 m/s, could be considered not sensitive to the spatial variation of free-field input ground motions due to embedment, including wave scattering effects. (author)