Some aspects of DSSI in the dynamic response of fully-coupled soil-structure systems

The seismic response of structures depends on many factors, among which the dynamic soil-foundation-overstructure inter- action (DSSI). Site effects can lead to a significant alteration of the seismic action established by the standard technical codes. In addition, DSSI can lead to significant modifications of the free-field motion, due to kinematic interaction. DSSI takes on an even more decisive role when sliding and uplift occur at the soil-foundation interface. Thus, fully-coupled soil-structure analyses should be performed to achieve at an appropriate anti-seismic structural design. DSSI phenomena have been studied for a long time, through reduced/full-scale tests, simplified approaches, and advanced nu- merical modelling. In recent years researchers have devoted greater attention to this subject, thanks to increased attention worldwide to performance-based design and more development of in-situ and laboratory monitoring equipment and numerical codes. The paper reports the main DSSI analysis results obtained by the authors with reference to a medium-scale shaking table test, a full-scale test, and a case study. The authors performed FEM modelling for all these soil-structure fully-coupled systems. Shallow foundations were a characteristic of all the systems investigated. The dynamic response of the soil-structure systems was investigated in the time and frequency domains, in terms of: accelerations, displacements, amplification/de-amplification factors, Fourier and response spectra, amplification functions and total shear forces per floor. The aim of this work is to focus on the importance of some aspects of DSSI when assessing the seismic response of fully-coupled, soil-structure systems in structures with shallow foundations. Particular attention has been given to the effects caused by sliding and uplift at the soil-foundation interface, as well as to the natural vibration periods of fully-coupled soil-structure systems. The results obtained offer some interesting ideas for less expensive seismic designs.