Piles-induced filtering action and its effect on the seismic response of buildings.

The inertial interaction analysis of a structure founded on piles is usually performed by taking that the support motion at the foundation level is merely that of the free field, thus neglecting the filtering action exerted by piles. By contrast, the existence of frequency filtering is confirmed through works referring to theoretical studies and experimental evidence, even if this effect has not been so far taken into consideration in design practice. Based on analytical and numerical studies, the importance of the filtering effect is highlighted. This paper focuses on the seismic performance of frame buildings, excited alternatively by the filtered input motion or the free-field input motion. The results of these analyses, expressed in terms of top displacements and base shear, allowed to assess the importance of the beneficial effect coming from the piles on the inertial response of the superstructure.