NOTATION

The effects of the depth of the embedment on the system response, under plane-strain conditions, have been studied for buildings supported by rigid circular foundations embedded into a homogeneous, i otropic and elastic half-space. The building has been represented byan equivalent single degree-of-freedom oscillator with a rotational spring and viscous damping. A linear analysis and the substructure approach ave been used to calculate the system response. The wave passage effects have also been included. Results are shown for incident plane SV-waves. The system damping ratio and the system frequency have been measured directly from the transfer-function f the relative building response. The system damping ratio has been measured by the width of the peak response, normalized by the system frequency. The results have shown that, during soil-structure interaction, deeper foundations act 'stiffer', and reduce less the system frequency, relative to the fixed-base frequency. The relative response, for the two-dimensional model, is smaller when the depth of the foundation is smaller. Except for heavy and tall buildings, the system damping ratio is smaller when the foundation isdeeper. The results of this study have been compared with the results for three-dimensional rectangular p ismatic foundations and for hemispherical foundations