A dynamic beam on a nonlinear Winkler foundation (or “dynamic p-y”) analysis method for analyzing seismic soil-pile-structure interaction was evaluated against the results of a series of dynamic centrifuge model tests The centrifuge tests included two different single-pile-supported structures subjected to nine different earthquake events with peak accelerations ranging from 002 to 07g The soil profile consisted of soft clay overlying dense sand Site response and dynamic p-y analyses are described Input parameters were selected based on existing engineering practices Reasonably good agreement was obtained between calculated and recorded responses for both structural models in all earthquake events Sensitivity of the results to dynamic p-y model parameters and site response calculations are evaluated These results provide experimental support for the use of dynamic p-y analysis methods in seismic soil-pile-structure interaction problems

Seismic Soil-Pile-Structure Interaction Experiments and Analyses

A simple analytical solution is developed for computing the dynamic impedances of floating rigidly-capped pile groups with due consideration to pile-soil-pile interaction. The method introduces some sound physical approximations and considers the interference of cylindrical wave fields originating along each pile shaft and spreading radially outward. Axial, lateral, and rocking oscillations of rigidly-capped pile groups are studied parametri-cally. Results are presented for the dynamic stiffness and damping of the whole group, and for the distribution of dynamic loads amongst the individual piles. The predictions of the simple method for vertical and rocking oscillations compare extremely well with rigorous numerical solutions, thereby offering a valuable insight into the nature of pile-soil-pile interaction. It is demonstrated and explained how the dynamic efficiency may far exceed unity at certain resonant frequencies due to destructive wave interference. The proposed method can be readily applied by en...

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Simple method for dynamic stiffness and damping of floating pile groups

The main objective of this work is to examine the effect of nonlinear soil behavior on the axial and lateral response of piles to monotonic and cyclic loading with a view towards developing simplified, yet realistic models for representing pile‐soil‐pile interaction effects. The specific role of pile‐soil slippage and separation, and the overall nonlinear soil behavior on the response of single piles and pairs of piles is studied by means of a three‐dimensional finite element elastoplastic model that includes interface elements for representing slippage and pile‐soil separation. Numerical results indicate that material nonlinearity can significantly affect pile and soil response. Pile‐soil slippage is dominant under purely axial loading, while for lateral loads pile‐soil separation and generalized inelastic soil deformation are the crucial factors. In fact, ignoring these sources of nonlinearity can lead to greatly overestimating the amount of interaction between piles. Guided by the results of this work,...

Three-dimensional nonlinear study of piles

A rational dynamic soil‐pile interaction model is presented. The model is developed adopting Winkler's hypothesis with a special attention to the conditions in which the strong nonlinearity is induced in the vicinity of the pile shaft under dynamic loading. It is formulated in a simple system of frequency independent mass, springs, and dashpots. Therefore, the model enables us to conduct the time‐domain nonlinear analysis in a relatively simple manner. Since the model can reproduce the dynamic effects by itself, its parameters are defined from the static behavior of a soil‐pile system or reasonable p‐y curves developed under the static condition. With a special consideration of a gap formed at the soil‐pile interface, the proposed model and procedure to define its parameters have successfully predicted the dynamic pile response observed in the field dynamic pile load tests. The nonlinear condition and dynamic condition are coupled with each other to produce the complex soil action to the pile shaft motion.

Nonlinear soil-pile interaction model for dynamic lateral motion

Nonlinear analysis for dynamic lateral pile response

Adopting a Winkler assumption, a simple mechanical soil model is developed for the flexural response analysis of dynamically loaded piles. The model is defined by examining a frequency-domain analytical expression of the dynamic response of a massless cylinder in an infinite previously developed medium. The expression is based on the plane strain assumption. Using this soil model, the time-domain transfer matrix is developed for the flexural response of a single pile. The steady-state harmonic response of a single pile is computed by both the present approach and a previously developed frequency-domain solution. Good agreement between the two computed results validates the present approach. The dynamic response of single piles subjected to the lateral impulse load is computed for piles in both homogeneous and inhomogeneous soil, in order to demonstrate the capability of the present approach. It is confirmed that the developed soil model and pile response formulation are very efficient in numerical computation.

Time domain flexural response of dynamically loaded single piles.

Nonlinear conditions are implemented in the time domain formulation for the dynamic response of pile foundations previously developed by the writers. Both single and group piles subjected to vertical dynamic load are considered. In the present study, the nonlinear effects in the vertical response are assumed to result from slippage of the pile from the soil. In order to demonstrate the capability of the present formulations and to see the effects of nonlinearity on the dynamic response of pile foundations, pile foundation responses are computed for both harmonic and transient load. Various interesting observations are made based upon the computed results.

Dynamic Response of Vertically Loaded Nonlinear Pile Foundations

Analytical expressions for soil stiffness for a group of piles were obtained for both plane strain and three dimensional conditions. A comparison between these two expressions revealed that a concept of a Winkler soil model could be applicable to pile group problems for the frequency range higher than the fundamental natural frequency of the soil deposit. A simple solution of dynamic pile group response was developed using a Winkler soil model extended to pile group problems and a transfer matrix method. Natures of dynamic group effect were studied for various cases. Using a simple structure supported by a pile group, it was demonstrated how the dynamic conditions in a group effect affects dynamic response of a pile-supported structure.

Toyoaki Nogami

Papers

Nonlinear soil-pile interaction model for dynamic lateral motion

Time domain flexural response of dynamically loaded single piles.

Dynamic Response of Vertically Loaded Nonlinear Pile Foundations

Dynamic Group Effect in Axial Responses of Grouped Piles

Dynamic Group Effect in Axial Responses of Grouped Piles