Application of regression models for the estimation of the flexible-base period of pile-supported structures in continuously inhomogeneous soils

Abstract

Although many research efforts have focused on analyzing the effects of soil-structure interaction considering homogeneous soil profiles and relevant achievements have been made under this assumption, reality is much more complex and structures are usually founded on stratified soils. It would be really interesting to be able to continue taking advantage of the knowledge and models available for homogeneous soils by developing strategies enabling to correct their results in order to consider the actual soil stratigraphy. This paper aims at estimating the flexible-base fundamental period of slender and non-slender structures supported on several pile group configurations embedded in different Gibson soils through a substructuring model which takes into account soil-structure interaction effects. The foundation dynamic impedances are obtained through a numerical model based on the integral formulation of the elastodynamic problem and the use of Green's functions for the layered half space. The results corresponding to each one of these variable-with-depth profiles are compared to those obtained for a homogeneous soil with the same average shear wave velocity in order to assess the effects of soil non-homogeneity. A significant influence of the soil profile on the structural flexible-base period is observed. A polynomial regression model is applied to obtain closed-form formulae and associated charts for estimating the flexible-base period of a pile-supported structure on different soil profiles. Moreover, these formulae can also be used for computing correction factors needed to estimate the fundamental period of structures supported on layered soils from those obtained with simplified models assuming a homogeneous soil profile.