Relevance of Dynamic Soil-Foundation-Structure Interaction for Pile-Supported Buildings

The paper examines the problem of the soil-structure interaction for buildings founded on piles throughout the comparative analysis between the seismic demand in compliant base and fixed base models. The aim of the work is to introduce a simple approach for evaluating the effects of soil-foundation-structure interaction (SFSI) for buildings founded on piles and, hence, to quantify the relevance of SFSI effects for this kind of structure. Inertial interaction analyses are carried out by idealizing the complete system as a linear SDOF on a deformable base represented by frequency dependent springs and dashpots. An application of the proposed methodology to a case study of a nine-story building resting on two well-studied subsoils, a deep clay layer from Piana del Fucino (Italy) and a pyroclastic deposit from Napoli, is presented and discussed. Reference is made to a complete seismic risk analysis in which the input signals are grouped into strips according to the conditional spectrum method. As a further objective, the effect of wall infills on the seismic demand in the reference buildings is investigated. The results show that for the pyroclastic deposit the seismic demand in the compliant model is comparable with that in the fixed base. By contrast, SFSI leads to a relevant reduction of the seismic demand for buildings on the clay layer. It is concluded that, contrary to the common belief, SFSI may also be relevant for tall buildings if they rest on soft soils.