Prediction of ground borne vibrations due to railway traffic

Alan, Salih
The aim of this thesis is to analyze the ground borne vibrations originating from railway traffic. A numerical prediction model is developed and elements of the railway structure are analyzed for ground vibrations due to railway traffic. The proposed prediction model is a time domain three-dimensional model. Modal parameters of track-and-ground-coupled structure and railway vehicle are obtained by modal analyses. Impulse response functions are calculated from modal parameters. The vibration responses are predicted by these impulse response functions. Modal coupling techniques are introduced to couple dynamic subsystems involving soil layers and track. Wave motion in ground layers are formulated by finite difference equations. A fourth-order staggered grid is implemented to extract system matrices from which modal parameters are obtained through eigenvalue analysis. Rayleigh damping model is implemented in time domain, for track and ground modeling. The developed model is compared and validated with in situ measurements available in literature. Time domain and frequency domain results as well as vibration indicators such as root mean square velocity level, peak particle velocity and maximum weighted severity predictions are shown to be in good agreement with existing measurement results taken from literature. Parametric studies of vehicle, track and ground parameters on ground vibration levels are presented. Ground vibration levels are compared for variation of the parameters: train type, train speed, rail unevenness, rail profile, sleeper spacing, ballast, subballast and subgrade stiffness, embankment material, Young’s modulus, Poisson’s ratio, density and damping ratio of ground layers. Effects of mitigation applications on ground vibration levels are analyzed. Under sleeper pad, under ballast mat and trench applications are modeled. The modular structure of the proposed method enables the user to modify and analyze the coupled system without going through the burden of remodeling of all the subsystems. This results in considerable reduction in computational times.
Citation Formats
S. Alan, “Prediction of ground borne vibrations due to railway traffic,” Ph.D. - Doctoral Program, Middle East Technical University, 2016.