Foundation impedance functions from full-scale soil-structure interaction tests

The paper presents and discusses the dynamic foundation impedance functions calculated from full-scale field tests on soil-structure interaction at the prototype facility of EuroProteas at Euroseistest in Greece. The experimental campaign included ambient noise, free- and forced-vibration tests throughout a wide frequency and amplitude range. The response of the soil-structure system was observed to be dominated by rocking. Hence, the impedances were derived under two hypotheses, i.e. considering or neglecting the foundation swaying in the dynamic equilibrium of the soil-structure system. The trend of the back-calculated impedance at high frequencies was observed to vary depending on the interpretation model and turned out to be in satisfying agreement with the available analytical solutions. Conversely, values at resonance were found almost independent of the test type and of the interpretation model. These findings imply that i) the currently widespread non-destructive tests (for instance ambient noise tests) can be effectively used to derive impedance functions; ii) the uncertainties are minimized for the resonance frequency traditionally used to calibrate the flexible-base models for soil-structure interaction analyses.