Keywords: railway substructure, Winkler foundation, Pasternak foundation, natural frequencies, mode shapes, acceleration function, railway sleeper, finite element analysis, Matlab.

This paper presents a numerical analysis of the railway substructure influence on the dynamic response of a railway sleeper. Potential use of modal and frequency data by means of a finite element analysis is presented within the paper. It is confirmed that substructure stiffness has a great influence on both the dynamic characteristics and the dynamic response of the railway sleeper in the lower frequency range. Hence, natural frequencies, mode shapes and acceleration functions are affected when ballast stiffness under the sleeper is not uniformly distributed. To represent different damage scenarios of the ballast layer, the spring stiffness is multiplied by different reduction factors. As a result the natural frequencies are reduced and mode shape curves show this discrepancy when compared with undamaged mode shape curves. Point acceleration curves also have different magnitudes and shapes. Two types of elastic foundation are considered and compared, namely the Winkler and Pasternak types.

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