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, aimed to evaluate kinematic bending moments developing during earthquakes. A quasi 3D finite element program has been used to perform dynamic analyses in the time domain. The pile has been considered as an elastic beam, while the soil has been modelled using a linear elastic constitutive model. The aims of the paper are: (i) to evaluate kinematic bending moments in single pile and piles groups with dynamic analyses in the time domain, in different subsoil conditions; (ii) to review some existing design methods; (iii) to propose a simplified analysis procedure to evaluate maximum kinematic bending moments between two subsequent soil layers. The results of the dynamic analyses have shown that some of the simplified approaches provided in literature tend to be conservative and can predict bending moments at the soil layer interface with adequate accuracy only within certain depths of the soil layer interface. On the basis of the obtained results a modified criterion to evaluate the transient peak bending moments at interfaces between layers is finally proposed.