Seismic structure-soil-structure interaction between pairs of adjacent building structures

Structure-soil-structure interaction between adjacent structures, which may occur in densely populated urban areas, has received little attention compared to the soil-structure interaction of single isolated structures. Additionally, recent earthquakes in/near such areas (e.g. the Christchurch series, 2010-2011) have shown that large motions can be followed by strong aftershocks. In this paper, the seismic behaviour of isolated structures and pairs of adjacent structures under a sequence of strong ground motions has been investigated using a combination of centrifuge and finite-element modelling. The latter utilised an advanced constitutive model that can be parameterised from routine test data, making it suitable for use in routine design. The finite-element models were shown to accurately simulate the centrifuge-measured response (in terms of surface ground motion and structural sway, settlement and rotation) even after multiple strong aftershocks, so long as the buildings' initial conditions were reproduced accurately. For the case of a building structure with a close neighbour, structural drift and co-seismic settlement could be reduced or increased as a result of structure-soil-structure interaction, depending chiefly on the properties of the adjacent structure. This suggests that careful arrangement of adjacent structures and specification of their properties could be used to control the effects of structure-soil-structure interaction. In all cases where adjacent structures were present, permanent rotation (structural tilt) was observed to increase significantly, demonstrating the importance of considering structure-soil-structure interaction in assessing the seismic performance of structures.