by Jonathan P. Stewart
Stewart, Jonathan P. (1999). Evaluation of Soil-Structure Interaction Effects from Strong Motion Recordings. SMIP99
Seminar on Utilization of Strong-Motion Data, p. 83 - 96.
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This paper reviews the results of recent studies that have investigated the effects of soil-structure interaction
(SSI) on the seismic response of building structures using recorded strong motions. Two manifestations of SSI are
described: (1) inertial interaction effects on the effective first-mode period and damping ratio of buildings, and
(2) variations between foundation-level and free-field ground motions. Inertial interaction effects are seen to
increase with the ratio of soil-to-structure stiffness, and are reasonably well predicted with simplified analytical
formulations similar to those in the NEHRP Provisions (BSSC, 1997). Ground motions in structures are seen to
generally be less than free-field motions. Foundation embedment and frequency are shown to significantly affect the
variations between these motions.