2691
Three Dimensional Finite Element Nonlinear Dynamic Analysis of Full-Scale Piles
under Vertical Excitations
Analyse dynamique non linéaire en 3D par éléments finis des pieux à grande échelle soumis
à des vibrations verticales
S. Biswas, B. Manna
Research Scholar, Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi - 110016, India
ABSTRACT: The present investigation emphasised on a comparative study between vertical vibration tests of full-scale single piles
(length of 22 m and diameter of 0.45 m) with the three-dimensional (3-D) finite element (FE) analysis using Abaqus/CAE. A 3-D
finite element model was developed to predict the nonlinear dynamic response of pile foundations in layered soil medium based on
field data. First, the FE analysis was carried out for static load for the validation of the finite element model and the results were
compared with the test results. Then, the vertical vibration analyses were conducted on the finite element model to determine the
frequency-amplitude response of the pile and the FE results were compared with the vertical vibration test results of full-scale pile. It
was found that the resonant frequency and amplitude obtained from the 3-D FE analysis were very close to the field test results of the
full-scale single pile. Based on the FE analysis the variation of the soil-pile separation length with the depth was presented in this
paper for different eccentric moments. It was found that the 3-D finite element model was found to be very efficient for the prediction
of the nonlinear frequency-amplitude response considering complex nonlinear phenomena of soil-pile system in layered soil medium.
RÉSUMÉ : La présente étude a mis l'accent sur une étude comparative entre les essais de vibrations verticales à grande échelle des
pieux simples (longueur de 22 m et un diamètre de 0,45 m) à l’aide d’une analyse par élément finis (EF) à trois dimensions (3D) en
utilisant Abaqus / CAE. Un modèle des éléments finis 3D a été développé pour prédire la réponse dynamique non linéaire des pieux
dans les sols multicouches en utilisant les données in-situ. Tout d'abord, l'analyse par éléments finis a été réalisée pour la charge
statique à fin de valider le modèle et les résultats ont été comparés avec les mesures in-situ. Ensuite, les analyses de vibrations
verticales ont été modélisées par éléments finis pour déterminer la réponse en fréquence d'amplitude du pieu et les résultats EF ont
été comparés avec les résultats d'essais aux vibrations verticales des pieux à pleine échelle. Il a été constaté que la fréquence de
résonance et l'amplitude obtenues à partir de l'analyse ont été très proches des résultats des essais in-situ du pieu à pleine échelle. La
variation de la longueur de la séparation sol-pieu avec la profondeur a été calculée dans ce papier pour différents moments
excentriques. Il a été constaté que le modèle 3D est très efficace pour la prédiction de la réponse de fréquence non linéaire-amplitude,
compte tenu des phénomènes complexes non linéaires du système sol-pieu dans un milieu multicouches.
KEYWORDS: Layered soils; Nonlinear response; Soil-pile separation; Vertical vibration; 3-D finite element analysis.
1 INTRODUCTION
Vibration of pile foundation from the operation of machine
produces elastic waves within the soil mass. The determination
of pile stiffness and damping parameters is an important step in
the analysis of pile-supported structures subject to dynamic
loading due to machinery and vibrating equipments etc. A key
step to a successful design of the machine-pile foundation
system is the careful engineering analysis of the pile foundation
response to the dynamic loads from the anticipated operation of
the machine. In recent years, a considerable amount of
theoretical research has been accumulated in the area of
dynamic behavior of piles, especially under linear elastic
assumptions. On the other hand, the available literature on
nonlinear soil-pile system subject to dynamic loading is limited.
The finite element method (FEM) was appropriate to study
the response analysis of the pile by considering the nonlinearity
of the soil medium and separation at the pile-soil interface.
Kuhlemeyer (1979) introduced the finite element results of soil-
pile system by a simple lumped mass model. Then Dobry et al.
(1982) made a parametric study (stiffness and damping
coefficients) of the dynamic response of single pile. Lewis and
Gonzalez (1985) was investigated the nonlinear soil response of
soil-pile system and soil-pile gapping using FE analysis.
Bentley and El Naggar (2000) developed a 3-D finite element
model that considers the soil nonlinearity, discontinuity
conditions at the soil-pile interface, energy dissipation, wave
propagation, and actual in-situ stress conditions, to evaluate the
kinematic soil-pile interaction. Maheshwari et al. (2004, 2005)
studied the significance of nonlinearity of soil-pile system by a
three dimensional finite element programme. Ayothiraman and
Boominathan (2006) was performed two-dimensional analysis
using Mohr-Coulomb soil model to determine the soil-pile
response by FE software package, PLAXIS. Manna and Baidya
(2009) used a simple axisymmetric two-dimensional finite-
element model for the prediction of the dynamic response of
full-scale single pile. It was observed that the finite-element
model predicted the natural frequency and peak displacement
amplitude of pile reasonably well.
It can be concluded based on literature review that a very
few studies are available to model of the full-scale pile-soil
system using rigorous 3-D finite element model. Prediction of
the boundary zone parameters and the soil-pile separation
lengths are another key aspect of nonlinear response of pile
foundation which has not been studied in details.Hence in the
present study, the nonlinear response of the soil-pile system was
investigated by a 3-D finite element package. Parametric study
was performed based on the comparison between finite element
analysis results and vertical vibration test results of full-scale
single pile.
Piles under Vertical Excitations
Biswas S. Manna B.
India
