Dynamic Comparison of Conventional Ballasted Track Versus Ballasted Ladder Track
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Date
2015-11
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Addis Ababa University
Abstract
In railway transport system there is a continuous demand for railway capacity enhancement. In order to meet the demands in many countries more axle load and higher speed of the train is applied. As a result of these the track responses are becoming big issues that have a great effect on track service. Therefore to develop and utilize appropriate tracks that cover relevant vibration effect, it is necessary to critically analyze and comparatively describing dynamic response of the tracks.
The main purpose of this research is to study and compare dynamic response of ballasted ladder and conventional ballasted of railway tracks by using finite element method. Both tracks are completely different depends on rail support system. Ladder track is continuous support system while conventional ballasted track is discrete support system. Depending on structural nature of tracks, both of tracks have been simulated in two dimensional finite elements by using commercial software Abaqus. Rail is considered as a solid element on discrete support in a conventional ballasted track while in the ballasted ladder track as continuous support system. Spring and dashpot has been used for the simulation of railpads and ballast.
In the model dynamic explicit analysis has been used for the simulation of a moving load and Eigen frequencies and corresponding vibration modes were extracted from both of the models. Finally by using simulation output, dynamic responses of both of tracks are compared in terms of time and frequency domain.
Dynamic responses of both tracks are relatively compared and found that the ballasted ladder track under different speed has lower vibration responses than conventional ballasted track, even if its level of responses at different frequency range is not the same. On contrary, conventional ballasted track shows higher vibration responses irrespective of frequency range. Ballasted ladder track at higher frequency range effectively reduce vibration of track components more than conventional ballasted track. However, at very low frequency range there is no great difference observed. In general the simulations indicate that the ballasted ladder track is effective in reducing vibration at high speed and frequency. Finally this thesis indicates the possible extensive comparative study of dynamics of both tracks by improving the assumption and the modeling approach applied in this research.
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Keywords
Dynamics of track, ladder track, conventional ballasted track, finite element analysis, discrete support system, continuous support system