The ever growing demand for public transportation and the need to integrate effective transport systems into urban life have led to an increase in the planning and construction of new railway systems in many countries around the world. These projects boast immense economic benefits, including high passenger capacity and reduction in commuting times. However, they are strongly opposed from an environmental point of view, not least the noise and vibration that are generated from their operations and subsequently transmitted into nearby buildings. In order to reduce the level of impact of the rail vehicles on the tracks, and subsequently the environment, railway tracks are commonly constructed with resilient elements, e.g. railpads. The dynamic properties of these elements have significant effects on noise generation, track and ground-borne vibration. It is important to develop understanding of the dynamic behaviour of railway tracks, through numerical modelling and/or experimental testing, in order to devise effective vibration countermeasures. To this end, many numerical models have been developed, most of which assumed linear and homogeneous track properties. However, many studies have shown that resilient elements exhibit pronounced nonlinear behaviour and that variability in track properties exists along the length of the track. In this study, novel approaches for incorporating nonhomogeneous and non-linear railpad properties in the modelling of railway track dynamics have been developed. A new method, called the Double Fourier Summation, have been used to account for nonhomogeneity in track foundation properties. To account for nonlinearity, on the other hand, constitutive relationships have been derived for the static and dynamic rail pad properties based on experimental data. These are then included into a time domain finite elements track model in order to study the effects of nonlinearity on track dynamics. The key findings of this research emphasise the necessity of including non-homogeneous and nonlinear behaviour of track resilience into the modelling of track dynamics. Large disparities in the track displacement, reaction-forces and wheel/rail interaction forces (more than 20 dB in some cases), have been observed between simplified linear homogeneous models and the more complex nonhomogeneous and nonlinear models presented in this work.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:756108 |
| Date | January 2014 |
| Creators | Koroma, Samuel Gerald |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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