ABSTRACT
Damage caused by past and recent earthquakes to the historic centres in Italy and abroad has highlighted the need to investigate the seismic response of structures built in aggregate or very close together. The close spacing among buildings could promote a mutual interaction through the underlying and surrounding soil, a phenomenon known as structure–soil–structure interaction or cross interaction. Like ordinary problems of soil-structure interaction, the substructure approach, in which the structure is endowed with springs and dashpots at its base to reproduce soil compliance, may turn useful even in solving cross-interaction problems. The paper tries to shed light on the modifications of the impedance functions of a shallow foundation when it is in-group with other footing systems. Indications on the proper calibration of the impedance matrix for a system of two or more nearby structures will be provided.
