TIME-HARMONIC RESPONSE OF LARGE-SCALE PILE GROUPS UNDER SEISMIC EXCITATION

Resumo

Models of the dynamic response of embedded pile groups are fundamental for our under-
standing of their interaction with the surface structure. This understanding is especially important when

the surface structure has particularly strict vibration requirements, such as particle accelerators, nuclear
powerplants, and concert halls. This work presents an implementation of the impedance matrix method
for the vibration of pile groups. Especial attention is given to the case of large-scale pile groups, due
to our goal of modeling and understanding the response of the foundations of a large synchrotron-light
source. The impedance matrix method comprises deriving the flexibility matrix of each layer of soil and
of discretized segments along the body of the pile, and obtaining the impedance matrix of the pile-soil
system by establishing direct kinematic compatibility and equilibrium conditions at their interface. The
soil part is modeled as a isotropic, three dimensional half-space, the solution of which is obtained by the
superposition of classical Green’s functions for such medium. The piles are modeled as one-dimensional
finite beam elements. Vertically-propagating time-harmonic shear seismic waves are incorporated as

excitation sources. The paper presents strategies to deal with the high computational cost of such large-
scale models involving the integration of Green’s functions for soil media. The response of different

constitutive and geometric parameters of the embedded pile group and layered soils are highlighted in
the response of the system to such excitations.