Minimising track degradation through managing vehicle/track interaction

Hawari, Haitham M. (2007) Minimising track degradation through managing vehicle/track interaction. PhD thesis, Queensland University of Technology.

Abstract

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.

Impact and interest:

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ID Code: 16366
Item Type: QUT Thesis (PhD)
Supervisor: Murray, Martin & Ferreira, Luis
Keywords: railway track, vertical forces, vertical profile, rail roughness, train characteristics, vehicle/track interaction, track degradation or deterioration, track maintenance, coal wagon, track recording vehicle (TRV), corrugation analysis trolley (CAT), signal processing techniques, coherence correlation, NUCARS, rate of deterioration
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Past > Schools > School of Urban Development
Department: Faculty of Built Environment and Engineering
Institution: Queensland University of Technology
Copyright Owner: Copyright Haitham M. Hawari
Deposited On: 03 Dec 2008 04:02
Last Modified: 22 Mar 2016 04:45

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