Formulation and calibration of a Pasternak model for seismic analysis of pile foundations

Abstract

Boundary and Finite Elements Methods (BEM and FEM) based models are accurate, but often require heavy computational costs. A simplified, analytical model is presented to obtain a faster yet reliable response of single pile foundations subjected to vertically-incident shear waves. This will enable us to analyse and incorporate in an intuitive way the most relevant dynamic properties of a determined system. More specifically, the soil is assumed to be a homogenous, linear, viscoelastic half space, while the pile foundation is considered as a Timoshenko beam with circular cross-section. Soil-Structure Interaction (SSI) is represented through a Pasternak model [1], instead of a usual Winkler. The reason lies in Winkler weaknesses. Although it is conveniently simple, considering independent linear springs would create discontinuities in a charged surface boundary, which means that Winkler model does not represent properly SSI in many cases. By approaching the problem through a Pasternak model, it is expected to achieve a better response, introducing soil cohesion and a more efficient force transmission through near field without losing simplicity. The aim of this study is the calibration of this Pasternak model for seismic analysis, using multidomain BEM model as the reference.