Luca de Sanctis

Kinematic response analysis of piled foundations under seismic excitation

This paper presents the results of an extensive parametric study on single piles and pile groups embedded in a two-layer subsoil profile, and is aimed to evaluate kinematic bending moments developi...

REDUCTION OF SEISMIC LOADING ON STRUCTURES INDUCED BY PILES IN INHOMOGENEOUS SOIL

The kinematic response of flexible piles in inhomogeneous soil is explored under harmonic and seismic excitation. The system under investigation consists of a long fixed-head pile embedded in viscoelastic soil with stiffness varying continuously with depth. A generalized power-law function is employed to describe the variable soil stiffness. The problem is treated numerically by means of a Beam-on-Dynamic-Winkler-Foundation (BDWF) model based on a layer transfer-matrix (Haskel-Thompson) formulation. This study aims at: (a) investigating numerical and modeling aspects related to Winkler analyses of soil-pile kinematic interaction in a non-homogeneous soil; (b) exploring soil-pile kinematic interaction as affected by varying subsoil conditions under harmonic oscillations; (c) providing a novel closedform expression for the kinematic interaction factor of pile-head over free-field response as a function of a single dimensionless frequency controlling the physical phenomenon and (d) elucidating the beneficial role of piles in the reduction of seismic loading imposed on pilesupported structures in terms of spectral acceleration for different pile-soil configurations and earthquake motions. Results show that: (a) large-diameter piles in soils with very low stiffness at shallow depths may substantially reduce the seismic acceleration imposed on structures and (b) the role of pile diameter becomes less important for strongly inhomogeneous soils. The latter indicates that even small-diameter piles may induce substantial filtering of ground motion if embedded in soft clays, which may be of importance in pile design practice. 1203 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 1203-1215

Centrifuge Modelling of Retaining Walls Embedded in Saturated Sand Under Seismic Actions

This paper describes the experimental work carried out under ‘PROPWALL’, a research project on the seismic performance of embedded walls in saturated sand carried out by Transnational Access to the Turner Beam Centrifuge of the University of Cambridge. The experimental equipment, the model preparation and the monitoring devices are described in detail. The results are presented in terms of accelerations, wall deflections, bending moments and excess pore pressures, as monitored by means of the devices installed on the walls and within the soil mass.

Effects of the filtering action exerted by piles on the seismic response of RC frame buildings

Abstract The inertial interaction analysis of a structure founded on piles is usually performed assuming the free-field motion as seismic action at the foundation level, thus neglecting the filtering action often exerted by piles. By contrast, the existence of frequency filtering is confirmed through works referring to theoretical and experimental studies, even if this effect is generally neglected in design practice. In this paper the seismic performance of frame buildings, excited by filtered and free-field input motions is evaluated. The results of these analyses, expressed in terms of top displacement and base shear, allow for assessing the importance of the beneficial effect coming from the piles on the inertial response of the superstructure.