A procedure for evaluating the soil-structure interaction effects on the system period and damping of pile-supported structures

Abstract

Soil-structure interaction involves kinematic and inertial effects that affect thedynamic behaviour of the structures. Thus, a proper assessment of their dynamic responserequires the development of models that incorporate, in a rigorous manner, the interaction be-tween the structure and the soil on which it is founded. Theseinteraction phenomena dependon factors such as: the foundation type, its geometry and embedment depth, the soil type andstratigraphy as well as the characteristics of the structure. In line with other authors’ studiesfor shallow [7] and embedded foundations [15], a simple substructuring model of soil-structureinteraction in the frequency domain is proposed herein to evaluate the influence of these factorson the dynamic response of structures founded on pile groupswhen subjected to seismic loads.A BEM-FEM coupling model [5] is used to compute the impedancefunctions and the kinematicinteraction factors. A simple and stable procedure is developed in order to estimate the pe-riod and damping of structures supported by different configurations of pile groups consideringsoil-structure interaction. For this purpose, several modifications are introduced in the strategypresented by Avil ́es and P ́erez-Rocha [15] for embedded foundations. A diagonal impedancematrix that takes into account the cross-coupled impedances of pile groups, which allows get-ting manageable equations, is obtained in the lines of Maravas et al. [16] in the case of singlepiles. All equations are expressed in terms of dimensionless parameters. An analysis of theinfluence of some of the main characteristics of the foundation affecting the system response isaccomplished. The results show that cross-coupled impedances and soil-structure interactioneffects should not be neglected.