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Tuned rail-damper: inherent property and effectiveness on railway vibration and noise reduction
Last modified: 2017-05-18
Abstract
The operational noise from viaduct railway is composed of both the viaduct-borne sound and the rolling noise that is associated with the rolling of the wheel on the rail. The roughness on the wheel and rail treads forms the relative displacement excitation and causes vibration of the wheel and rail. When the vibration propagates in the wheel and rail, they radiate noise. To the overall A-weighted sound the contribution of the rolling noise dominants, whereas that of the viaduct-borne sound is low and might be omitted, as it is mainly consists of low frequency components and will dramatically be reduced by the weighting factors. Moreover, as the train speed in the city transit system is not very high (usually below 100km/h), the rail radiated sound is dominant compared with the wheel radiation.
The components of rail vibration are mostly in the middle frequency range 500-1500Hz. In this region the damping introduced by the rail fasteners is low. An alternative way adding damping to the rail vibration is use of the tuned rail dampers, which are designed to have a resonance and around it the rail vibration energy is transmitted to the rail dampers, which store and dissipate the rail vibration energy and thus reduce the rail radiation. As the tuned rail dampers effectively function around the resonance, their practical effects on mitigation of the rolling noise may vary with the excitation and environmental conditions. In some circumstances a 6-8dB reduction in A-weighted noise may be achieved by use of the rail dampers, whereas in other cases only a 2-3dB reduction is obtained. This will cause confusion for assessment of the rail dampers’ performance.
In this paper a new developed type of rail damper, which is applied for reducing the rolling noise of a viaduct line in Shanghai transit system, is chosen to be studied. A simple railway track model with the rail dampers applied is developed to predict the performance of the rail dampers. Two criteria are proposed to judge the inherent ability to reduce the rail vibration and radiation and to predict the practical effects of the rail damper on reduction of the rolling noise, respectively. The inherent ability of the rail damper does not vary with the environment conditions in use, whereas the practical effects vary with the environment conditions. The model predictions are validated by the measurements in situ. The methodology proposed and the model developed in the study is useful in the engineering practice of rolling noise and vibration control.
The components of rail vibration are mostly in the middle frequency range 500-1500Hz. In this region the damping introduced by the rail fasteners is low. An alternative way adding damping to the rail vibration is use of the tuned rail dampers, which are designed to have a resonance and around it the rail vibration energy is transmitted to the rail dampers, which store and dissipate the rail vibration energy and thus reduce the rail radiation. As the tuned rail dampers effectively function around the resonance, their practical effects on mitigation of the rolling noise may vary with the excitation and environmental conditions. In some circumstances a 6-8dB reduction in A-weighted noise may be achieved by use of the rail dampers, whereas in other cases only a 2-3dB reduction is obtained. This will cause confusion for assessment of the rail dampers’ performance.
In this paper a new developed type of rail damper, which is applied for reducing the rolling noise of a viaduct line in Shanghai transit system, is chosen to be studied. A simple railway track model with the rail dampers applied is developed to predict the performance of the rail dampers. Two criteria are proposed to judge the inherent ability to reduce the rail vibration and radiation and to predict the practical effects of the rail damper on reduction of the rolling noise, respectively. The inherent ability of the rail damper does not vary with the environment conditions in use, whereas the practical effects vary with the environment conditions. The model predictions are validated by the measurements in situ. The methodology proposed and the model developed in the study is useful in the engineering practice of rolling noise and vibration control.