The rate at which a railway track deteriorates depends on the response of the track under different static and repeated dynamic forces. These wheel/rail forces lead to imperfections in the rail surface and deviation in track geometry alignment. The wheel/rail forces are dependent upon the quality of maintenance of the characteristics of both train and track. If train components such as wheelsets and suspensions are maintained to a high standard, less dynamic forces are generated at the wheel/rail interface and less damage is caused over time. Therefore, the amount and cost of maintenance of track are reduced. However, there is little known about how the characteristics of train components affect time-dependent track degradation. Track degradation through deviation of track from its ideal position has the most effect on maintenance costs. Therefore, the present research aims to investigate this track degradation and improve understanding of the effects of train characteristics (such as train mass and speed, suspension stiffness and damping) on railway tracks. The research is conducted by looking into the relationship between wheel/rail forces and track degradation on one hand and between wheel/rail forces and train characteristics on the other hand, with the objective of assisting in managing vehicle/track interaction in order to minimise track degradation. This aim is achieved by investigating the above two relationships to attain the desired relationship between track degradation and train characteristics. The research focuses on wheel/rail vertical forces (both amplitudes and frequencies), vertical track alignment (longitudinal vertical profile), and rail head defects. The study started by collecting wheel/rail vertical forces data in addition to data on vertical track degradation under sustained traffic loads on a heavy haul railway section of track in Central Queensland. Also, five years of degradation and maintenance history data were collected on three other test sections of railway track under variety of traffic conditions and loads in Central Queensland. There were four main analyses of this data employed to probe the study. The first analysis was performed by examining the track degradation history data. The standard deviation method was used in this first analysis to acquire the rate of deterioration in terms of its relationship to track profile (roughness). The second analysis was accomplished by correlating the vertical wheel/rail forces to both vertical track profile and rail roughness using signal processing principles and a function know as coherence. The third analysis was carried out by using the computer simulation software NUCARS to obtain the link between wheel/rail forces and the deterioration of the vertical track profile. The fourth analysis was achieved by combining the results obtained from the above three analyses to acquire the rate of track deterioration in terms of its relationship to varying train characteristics. The first analysis mentioned above quantified the relationship between the level of roughness of the track and rate at which that roughness deteriorated. An important outcome of this relationship is that there is a threshold of roughness below which track deterioration is minimal. The track maintenance planners can now use that threshold for cost effective targeting of tamping activities. The correlation study between track roughness and wheel/rail forces using the coherence function found, surprisingly, that the overall deterioration of the track roughness, in the absence of frequencies of forces above 30 Hz, is due to the so-called quasi-static lower frequency oscillations of dynamic forces. This conclusion together with the relationship between vehicle characteristics and track forces, established in the analyses above, has significant implications for the design of wagon bogies and for charges track owners might levy on trains using their tracks. This research is part of a larger Rail CRC project 11/4 called 'Enhancing the Optimisation of Maintenance/Renewal' being carried out in the School of Urban Development in Queensland University of Technology.
| Identifer | oai:union.ndltd.org:ADTP/265358 |
| Date | January 2007 |
| Creators | Hawari, Haitham M. |
| Publisher | Queensland University of Technology |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
| Rights | Copyright Haitham M. Hawari |
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