Modification of Dynamic Foundation Response Due to Soil-Structure Interaction

This paper presents the results from extensive parametric dynamic analyses of soil-structure systems that focus on the clear modification (increase or decrease) of the acceleration amplitude at the foundation with respect to the free-field, especially for squatty structures. Properties of the systems are selected such as to cover a wide range of meaningful geometries and materials for engineering practice. The results are presented in terms of weighted modification factors of the maximum foundation acceleration amplitude with reference to the corresponding maximum acceleration amplitude at free-field, for squatty and more slender structures. For the large majority of the studied systems, foundation acceleration decreases from the free-field by 10–15% on average. Nevertheless, acceleration demand at the foundation increases compared to the free-field, for 30% of squatty and for 15% of the more slender structures. Modification of the foundation acceleration amplitude is also correlated with the ratio of the predominant period of the input motion to the flexible-base system period. Finally, the findings of this study are compared with sparse available recorded data from the Seismic Hazard Harmonization in Europe database.