Seismic Response of End-Bearing Piles

Flores-Berrones, Raúl; Whitman, Robert V.

doi:10.1061/ajgeb6.0001275

Cited by 78 publications

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“…The response of bridge-foundation systems such as those of Figure 1 can be computed as the superposition of two effects, as proved by Kausel and Roesset (see also References 9,[27][28][29]: (1) a so-called kinematic interaction effect (sometimes also referred to as 'wave scattering' effect), involving the response to base excitation of a hypothetical system which differs from the complete actual system of Figure 1 in that the mass of the superstructure is set equal to zero; (2) an inertial interaction effect, referring to the response of the complete pile-soil-structure system to excitation by D'Alembert forces,!Mu ( I , associated with the acceleration, u ( I , of the superstructure due to the kinematic interaction. This partition is exact for linear soil, pile, and structure if the analysis in both stages is performed rigorously.…”

Section: Outline Of Methods Of Analysis ¹He Superposition Of Kinematic and Inertial Responsementioning

confidence: 99%

Soil-Pile-Bridge Seismic Interaction: Kinematic and Inertial Effects. Part I: Soft Soil

Mylonakis

Nikolaou

Gazetas

1997

Earthquake Engng. Struct. Dyn.

174

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A substructuring method has been implemented for the seismic analysis of bridge piers founded on vertical piles and pile groups in multi-layered soil. The method reproduces semi-analytically both the kinematic and inertial soil-structure interaction, in a simple realistic way. Vertical S-wave propagation and the pile-to-pile interplay are treated with sufficient rigor, within the realm of equivalent-linear soil behaviour, while a variety of support conditions of the bridge deck on the pier can be studied with the method. Analyses are performed in both frequency and time domains, with the excitation specified at the surface of the outcropping ('elastic') rock. A parameter study explores the role of soil-structure interaction by elucidating, for typical bridge piers founded on soft soil, the key phenomena and parameters associated with the interplay between seismic excitation, soil profile, pile-foundation, and superstructure. Results illustrate the potential errors from ignoring: (i) the radiation damping generated from the oscillating piles, and (ii) the rotational component of motion at the head of the single pile or the pile-group cap. Results are obtained for accelerations of bridge deck and foundation points, as well as for bending moments along the piles.

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Section: Outline Of Methods Of Analysis ¹He Superposition Of Kinematic and Inertial Responsementioning

confidence: 99%

Soil-Pile-Bridge Seismic Interaction: Kinematic and Inertial Effects. Part I: Soft Soil

Mylonakis

Nikolaou

Gazetas

1997

Earthquake Engng. Struct. Dyn.

174

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“…It has been established that kinematic interaction effects can be predicted with reasonable accuracy, provided that the soil stiffness profile is evaluated through an equivalent linear viscoelastic analysis. [13][14][15] The filtering of seismic ground motion due to soil-pile interaction has been established using several closed form analytical solutions, 11,[16][17][18][19][20] boundary element formulations 21,22 as well as numerical models. [23][24][25][26][27][28][29][30] Studies by Gazetas and Dobry 19 and Kaynia and Kausel 20 showed that the filtering of the free-field motion was stronger in inhomogeneous soil profiles when compared to homogeneous profiles.…”

Section: Introductionmentioning

confidence: 99%

Investigation of pile‐induced filtering of seismic ground motion considering embedment effect

Varghese

Boominathan

Banerjee

2021

Earthq Engng Struct Dyn

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The Foundation Input Motion (FIM) arising out of kinematic soil-pile interaction forms an integral part of the seismic analysis of pile-supported structures. Several studies in the recent past have recognized the importance of the filtering effect produced by pile foundations. This paper presents a comprehensive investigation of the influence of raft embedment on the Foundation Input Motion from piled rafts. A hybrid numerical methodology based on the finite element-boundary element method is employed to rigorously model rectangular piled rafts in varying soil conditions. Analysis of transfer functions in the frequency domain suggests that the translational response is suppressed by increasing embedment of the raft. An increase in rocking response is also synchronous with this decrease in translational motion. A transient response analysis carried out using eight different earthquake time histories showed that the spectral acceleration curve is altered by the embedment effect. A set of simplified expressions are proposed to incorporate the embedment effects in the spectral acceleration ratio curve of a pile group. These proposed expressions have the potential to enable a quick estimation of the effect of embedment in the seismic design of pile-supported structures.

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“…It is well-known that in Winkler models pile-soil interaction is controlled by the key dimensionless parameter (Flores-Berrones and Whitman, 1982;Mylonakis, 1995) λL…”

Section: Static Responsementioning

confidence: 99%

“…Note that inertial interaction is affected by kinematic interaction as the input motion to the former problem is the output motion of the latter (Kaynia and Kausel, 1982;Mamoon and Banerjee, 1990;Fan et al, 1991;Rovithis et al, 2012). Starting with the pioneering work by Blaney et al (1976), a large number of analytical studies have demonstrated the importance of kinematic effects on piles (Margason, 1975;Flores-Berrones and Whitman, 1982;Dobry and O'Rourke, 1983;Kavvadas and Gazetas, 1993;Mylonakis, 1999Mylonakis, , 2001b.…”

Section: Introductionmentioning

confidence: 99%

“…Note that even though λ is complex-valued, no superscript ( ) * is used to distinguish it from real-valued counterparts for the sake of simplicity.The general solution to the above equation is w(z, ω) = (A cos λz + B sin λz) e −λz + (C cos λz + D sin λz) e λz + Γ u ff (z, ω) (9.15) where A, B, C, D are integration constants dependent on the boundary conditions; Γ is a dimensionless response coefficient given byFlores-Berrones and Whitman (1982) …”

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Contribution to kinematic and inertial analysis of piles by analytical and experimental methods

Ανωγιάτης¹

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The problem of pile - soil interaction is examined in the Thesis at hand by means of both theoretical analyses and experimental investigations. Pile foundations in seismically prone areas are subjected to both direct loading, such as axial and lateral forces imposed at their heads, resulting from a phenomenon known as inertial interaction, and indirect loading along their body, such as imposed displacements due to the passage of various types of seismic waves, resulting from a phenomenon known as kinematic interaction. Along this vein, a family of analytical models of the Tajimi type are presented in the framework of linear elastodynamic theory to explore the effects of axial and lateral pile - soil interaction in homogeneous and inhomogeneous soil under static and dynamic (kinematic and inertial) loading. Apart from simplified two-dimensional models of the Baranov - Novak type, few analytical solutions are available to tackle these problems in three dimensions, the majority of which are restricted to the analysis of an elastic half space under static conditions.The proposed models are based on a continuum solution pioneered by Japanese investigators (notably Matuso & Ohara and Tajimi) in the 1960’s. In the realm of this approach the soil is modelled as a continuum, while the pile is conveniently modelled as a rod or a beam by strength-of-materials theory. Displacements and stresses are expressed through Fourier series in terms of the natural modes of the soil medium.Fundamental to the analysis presented in this study is that the influence of horizontal soil displacement on axial pile response and vertical displacement on lateral response, respectively, are negligible. However, their effect on stresses is not negligible which differentiates the proposed models from the classical Tajimi solutions in which the aforementioned displacements are set equal to zero. The above approximations are attractive, as they lead to a straightforward uncoupling of the equations of motions, even in inhomogeneous media, unlike the classical elastodynamic theory where the uncoupling is generally impossible in presence of inhomogeneity.Although approximate, the proposed models are advantageous over available analytical models and rigorous numerical schemes, as they require relative simple computations and provide excellent predictions of pile response at the frequency ranges of interest in earthquake engineering and geotechnics. In addition, they are advantageous over existing simplified analytical approaches of the Winkler type, as they are more accurate, self - standing, free of empirical constants and provide more realistic simulation of the problem. The main advantage over numerical methods (finite and boundary elements) lies in the derivation of the solution in closed form and the elucidation of complex mechanisms related to the dynamic interaction phenomenon, such as radiation damping and wave propagation in in homogeneous media.The main goal of the theoretical effort lies in the derivation of solutions in closed - form for: (i) the static stiffness and the dynamic impedances (dynamic stiffness and damping coefficients) at the pile head, (ii) translational and rotational kinematic response factors (pile head displacement or rotation over free-field response), (iii) actual, depth- dependent, Winkler moduli (spring and damping coefficients), (iv) corresponding average, depth- independent, Winkler moduli to match the pile head stiffness. In addition, simple approximate formulae for Winkler moduli to be used in engineering practice are proposed, to improve the predictions of Winkler models.Pile-to-pile interaction is investigated on the basis of the superposition method for axially loaded piles. Closed-form expressions for attenuation functions are derived to be used individually or in conjunction with more elaborate methods providing more accurate predictions for static and dynamic interaction factors to assess the vertical stiffness of pile groups. New dimensionless frequency ratios controlling pile response are introduced.Finally, new solutions are added in the context of analytical Winkler models for investigating the behaviour of piles under kinematic loading due to vertically-propagating S waves. Emphasis is given on the influence of boundary conditions of the pile. With reference to kinematic pile bending, insight into the physics of the problem is gained through a rigorous superposition scheme involving an infinitely-long pile excited kinematically, and a pile of finite length excited by a concentrated force and a moment at the tip. Contrary to the classical elastodynamic theory where pile response is governed by six dimensionless ratios, in the realm of Winkler theory three only ratios suffice to fully describe the interaction problem, from which the mechanical slenderness and the effective dimensionless frequency are introduced for the first time. The selection of an appropriate value for the Winkler modulus in the accuracy of the kinematic Winkler model is demonstrated.The theoretical results are compared to new experimental data obtained from a series of tests on piles carried out on scaled models performed on the shaking table at University of Bristol Laboratory (BLADE) within the framework of the Seismic Engineering Research Infrastructures (SERIES) program, sponsored by FP7, and contribute in the investigation of pile - soil interaction.

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Seismic Response of End-Bearing Piles

Cited by 78 publications

References 0 publications

Soil-Pile-Bridge Seismic Interaction: Kinematic and Inertial Effects. Part I: Soft Soil

Soil-Pile-Bridge Seismic Interaction: Kinematic and Inertial Effects. Part I: Soft Soil

Investigation of pile‐induced filtering of seismic ground motion considering embedment effect

Contribution to kinematic and inertial analysis of piles by analytical and experimental methods

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