Abstract The determination of stiffness and damping of piles is an important step in the
analysis of pile-supported structures subjected to dynamic loading.; The first part of this
study examines the use of approximate methods to evaluate the impedance functions of
single piles and pile groups. The group impedances derived from the superposition of the
two-pile solution are compared with those obtained from direct analysis. Good agreement is
observed for floating piles in homogeneous and nonhomogeneous soil profiles.