Dynamic through-the-soil interaction between adjacent piled structures by bem-fem model

Abstract

Not only the dynamic response of structures is highly dependent on the flexibility of the soil-foundation system and on the kinematic interaction between the foundation and the incident wave field, but it also may be significantly influenced by the presence of neighbouring structures by means of through-the-soil interaction. To address this problem in the case of adjacent piled structures, a previously developed 3D BEM-FEM coupling model for the dynamic analysis of pile foundations, where the Boundary Element Method (BEM) is used to model the soil, and the Finite Element Method (FEM) is used to model the piles as Euler-Bernoulli beams, has been enhanced to include the presence of piled structures (modeled by FEM) made up by vertical extensible piers and horizontal rigid slabs. The resulting code allows the analysis in the frequency domain of the dynamic behaviour of groups of structures, three-dimensionally arranged, founded on multilayered viscoelastic soils through one or more pile caps. This way, the dynamic behaviour of different configurations of structures subjected to S and Rayleigh waves is analysed in this paper. As a first step, the structures have been modeled as one-storey shear structures founded on 3×3 pile groups on a viscoelastic halfspace. It is shown that through-the-soil interaction between structures of similar dynamic properties affects the system response, mainly around its fundamental frequency. The seismic response of any of the structures can either increase or decrease in presence of other structures depending on the distance between adjacent buildings, i.e., there are values of this distance for which the seismic response of the system is amplified, but there are other values for which the response is attenuated, so that the structural risk diminishes in case of a seismic event.