Numerical Model for the Dynamic Analysis of Pile Foundations

Abstract

A three-dimensional boundary element-finite element model for the dynamic analysis of pile foundations and pile supported structures has been formulated and implemented. It represents a direct approach to the problem in the frequency domain, and it is able to analyse the response of multiple multistorey pile supported structures founded on multilayered soils of generic stratigraphy and topography. In this coupling model, the Finite Element Method (FEM) is used to model piles and superstructures, while stratified soils are modelled by the Boundary Element Method (BEM), each stratum being considered as a continuum, semi-infinite, isotropic, viscoelastic medium. Therefore, the main objective of this work is the formulation and implementation of a BEM-FEM model for the time harmonic dynamic analysis of pile foundations embedded in viscoelastic soils and of pile supported structures. The idea is assuming that the soil continuity is not altered by the presence of the piles and that tractions at the pile-soil interface can be considered, from the integral equation point of view, as body forces. This implies computing a domain integral involving the body forces, which are usually considered to be zero in most applications. However, these new integrals are extended only to the pile-soil interface, so there is no need of discretizing the whole domain.

After formulating and validating the model, it will be applied to three different kinds of problems: (1) the computation of impedance functions and kinematic interaction factors of pile foundations; (2) the assessment of soil-structure interaction effects on pile supported structures, making use of previously computed dynamic stiffness and kinematic interaction factors in substructure methods; and (3) the evaluation of the influence of the presence of nearby structures on the seismic response of pile supported buildings.