Three-Dimensional Nonlinear Seismic Analysis of Pile Groups Using FE-CIFECM Coupling in a Hybrid Domain and HISS Plasticity Model.

This paper reports the three-dimensional (3D) nonlinear dynamic analysis of floating pile groups subjected to seismic loading. For the nonlinear dynamic analysis of foundations in general, and pile foundations in particular, a perfect accuracy in modeling the frequency dependence of the unbounded soil support, as well as the local temporal nonlinearities, was ensured. In the current work, the finite elements (FEs) and boundary FEs were coupled in a hybrid domain of alternating frequency-time domains, to analyze the nonlinear dynamics of pile foundations in a 3D space. The frequency dependence of the stiffness and the damping of the unbounded far-field soil were completely accounted for by the consistent infinitesimal finite-element cell method (CIFECM) in the frequency domain, whereas the nonlinearities and transient conditions of the near-field were accounted for by the FE in the time domain. The hybrid frequency time domain algorithm is used for coupling the two domains. For the evaluation of nonlinear effects, an advanced, plasticity-based, hierarchical single surface (HISS) soil model was used. The applicability of this rigorous approach to pile foundations was validated using well-established results in the literature. The transient dynamic response of a 232 pile group embedded in clayey soils was performed. Using the results, the frequency response of the pile foundations is presented under elastic and inelastic soil conditions in terms of dynamic impedances and kinematic interaction factors for different pile spacings. The results showed significant reduction, caused by soil plasticity, in both the lateral stiffness and the damping of the pile groups. [ABSTRACT FROM AUTHOR]