FORCES IN-PILE FOUNDATIONS UNDER SEISMIC LOADING

The purpose of this paper is to study the relative significance of kin ematic and inertial interaction on the magnitude of forces induced in pile foundations by a seismic disturbance. The structure is modeled as a single-degree-of-freedom (SDOF) oscillator and the foundation is a typical pile group embedded in a homogeneous half-space. A three-dimen sional Green's function-based formulation, which rigorously models the pile-soil-pile interaction, is used to calculate the forces in the pi les during the seismic kinematic- and inertial-interaction phases. Dif ferent structures, represented by their aspect ratios and natural freq uencies, and different pile foundations, characterized by their pile r igidities and spacings, are considered in this study. The results show that the seismic shear force and bending moment in a pile are strongl y contributed by the kinematic seismic interaction, except in a band a pproaching the natural frequency of the pile-soil-structure system. in this frequency band, the inertial interaction dominates the pile forc es. The extent of contribution from the inertial interaction is govern ed by the damping of the foundation.