A Procedure for Evaluating the Soil-Structure Interaction Effects on the System Period and Damping of Pile-Supported Structures

Abstract eng:
Soil-structure interaction involves kinematic and inertial effects that affect the dynamic behaviour of the structures. Thus, a proper assessment of their dynamic response requires the development of models that incorporate, in a rigorous manner, the interaction between the structure and the soil on which it is founded. These interaction phenomena depend on factors such as: the foundation type, its geometry and embedment depth, the soil type and stratigraphy as well as the characteristics of the structure. In line with other authors’ studies for shallow [7] and embedded foundations [15], a simple substructuring model of soil-structure interaction in the frequency domain is proposed herein to evaluate the influence of these factors on the dynamic response of structures founded on pile groups when subjected to seismic loads. A BEM-FEM coupling model [5] is used to compute the impedance functions and the kinematic interaction factors. A simple and stable procedure is developed in order to estimate the period and damping of structures supported by different configurations of pile groups considering soil-structure interaction. For this purpose, several modifications are introduced in the strategy presented by Avil´es and P´erez-Rocha [15] for embedded foundations. A diagonal impedance matrix that takes into account the cross-coupled impedances of pile groups, which allows getting manageable equations, is obtained in the lines of Maravas et al. [16] in the case of single piles. All equations are expressed in terms of dimensionless parameters. An analysis of the influence of some of the main characteristics of the foundation affecting the system response is accomplished. The results show that cross-coupled impedances and soil-structure interaction effects should not be neglected.

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