Keywords: vehicle induced vibrations, dynamic soil-structure interaction, three-dimensional numerical analysis, time domain, finite element method, Green functions.

The implementation and validation of a numerical analysis methodology which can be used in the prediction of vehicle induced vibrations is described. This methodology is formulated in the time domain for the three-dimensional case. Although presented in the context of vehicle induced vibrations, it can be adopted in the study of general problems of dynamic soil-structure interaction in which the structure lies on the surface of the soil [1]. The method is based on the coupling of the fundamental Green functions to a finite element code (FEMIX). These functions describe the behaviour of the unbounded soil, while the use of finite elements enables an adequate simulation of the part of the domain where inhomogeneities or nonlinearities occur. The advantages of this procedure are related to the possibility of modelling structures with complex geometries which are not invariant along any direction, as well as the capability of performing nonlinear analyses. The main drawback of these models is their high cost in terms of time and computational resources.

Some details about the implementation are discussed and two numerical examples are presented, corresponding the former to the analysis of the dynamic response of a rigid square surface foundation and the latter to the study of the dynamic response of a slab resting on a homogeneous halfspace due to a passage of a moving load. The tool developed can be used in the prediction of vibrations induced by trains (in the track as well as in the surface of the adjacent soil), corresponding to the tests presented as part of the validation procedure based on several steps of increasing complexity. The comparison of the results obtained with those presented in the literature [1] as well as with those obtained by means of a different validated method [2] demonstrates good agreement. However, since this tool was developed in order to be used in the prediction of vehicle induced vibrations, some tests with increasing complexity are still required for that goal to be achieved.

1

C. Bode, R. Hirschauer, S. Savidis, "Soil-structure in the time domain using halfspace Green's functions", Soil Dynamics and Earthquake Engineering, 22, 283-295, 2002. doi:10.1016/S0267-7261(02)00020-9

2

P.A. Costa, "Moving loads on the ground: a numerical model based on 2.5D FEM/ITM for dynamic analyses", Internal Report, FEUP, Portugal, 2008.

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