The three-dimensional dynamic interaction of surface foundations with structures buried in the ground or local geological inhomogeneities can have a significant impact on the structural responses and the wave propagation patterns in the ground. In particular, when amplification of ground motions occurs due to diffraction and scattering, it is essential to integrate these inclusions into prediction models and thus consider the Structure-Soil-Structure-Interaction (SSSI).
In this contribution an efficient 2.5D coupled Integral Transform Method (ITM) – Finite Element Method (FEM) approach is used to compute the complex, dynamic stiffness at the surface of a layered soil including a longitudinally invariant structure or inhomogeneity. Herein, the analytical ITM solutions of the dynamic wave equation allow to account for the infinite extension of the soil by satisfying the radiation condition. The FEM enables to model complex, spatially limited structures and a part of the surrounding soil within a cylindrical outer boundary, on which both methods are coupled. The foundation on the ground surface is modelled using 3D finite elements and is coupled to the soil substructure enforcing the compatibility conditions at the common interface.
By solving the overall system of equations in the frequency domain for an external load with unit amplitude over the entire frequency range, the transfer functions for the foundation compliances are calculated, weighted by the frequency spectrum of the transient load, and finally transformed to the time domain by an inverse Fourier transform.
The effect of soil stratification as well as embedment depth, size and stiffness of the inclusion on the transient foundation behaviour is investigated and interpreted by drawing correlations to the frequency spectra of the foundation compliances and power input at the soil-foundation interface. In addition, time-dependent displacement distributions on the soil surface are presented to illustrating the effects of the SSSI on wave propagation characteristics such as predominant wave types, propagation directivity, as well as interference and wave impeding effects due to the inclusion. For this purpose, a postprocessing procedure is used in which the interaction forces at the soil-foundation interface are applied as an external load to the soil substructure.
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The three-dimensional dynamic interaction of surface foundations with structures buried in the ground or local geological inhomogeneities can have a significant impact on the structural responses and the wave propagation patterns in the ground. In particular, when amplification of ground motions occurs due to diffraction and scattering, it is essential to integrate these inclusions into prediction models and thus consider the Structure-Soil-Structure-Interaction (SSSI).
In this contribution a...
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