Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Pile group foundations are often used to support heavy structures. The capacity of the pile foundation to resist static and dynamic loads depends on the behavior of the piles which, in turn, is a product of pile-soil-pile interaction.;Dynamic analysis of pile groups is very recent and rather complex while corresponding experimental data are limited.;Field dynamic experiments and limited static tests with a large group of 102 piles are described and results are presented in order to verify the linear theories accounting for pile-soil-pile interaction.;The experimental data for vertical and horizontal excitation are compared with the theoretical predictions made on the basis of different approaches that account for the group effect, namely; static interaction factors, dynamic interaction factors, complete dynamic solution, direct static analysis and the equivalent pier. The comparison suggests that dynamic analytical techniques are able to predict the main features of dynamic behavior of pile groups, but tend to overestimate damping, i.e., underestimate the response. In addition to the difficulty involved in calculating the static interaction factors for large groups, the approach may underestimate the stiffness and does not yield any estimate of group geometric damping.;A method is formulated which avoids the use of the interaction factors while remaining simple and is computationally very efficient, facilitating a fast inexpensive computer analysis of very large pile groups. The method presented allows for an arbitrary soil profile, pile type and configuration, evaluates group stiffness, forces on individual piles and material damping making it suitable for static and low frequency dynamic loading. The direct analysis calculates the vertical, horizontal and rocking response; its results agree very well with those of field experiments and other direct methods available.



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