Vibration of railway bridges in the audible frequency range.
University of Southampton, Institute of Sound and Vibration Research,
The noise level associated with a train travelling on a bridge is normally greater than that for a train travelling on plain track. It is sometimes the bridge noise that causes the highest levels of disturbance to people in the vicinity or triggers action under
regulations such as the Environmental Noise Directive. Consequently, there is a need to study means of predicting noise levels from proposed bridges, noise control
measures for existing structures and principles of low-noise bridge design.
This thesis describes a programme of work in which an existing calculation model for bridge noise and vibration has been tested and alternative calculation methods have
been developed where required. The existing model is based on analytical models for wheel-rail interaction and the calculation of the power input to the bridge. The
response of the various component parts of the bridge for this power input is found using a simplified SEA scheme.
In this work, the existing model has been tested against measurements made on railway bridges and the results of an advanced method of structural analysis, the
Waveguide Finite Element (WFE) method. This method is well-suited to modelling some important types of railway bridge. Specifically, it allows a numerical modelling
approach to be used up to higher frequency than conventional Finite Element methods. It has been found to offer some significant advantages over the existing
bridge noise model, particularly for concrete-steel composite bridges and concrete
The track support structure has an important influence on bridge noise and vibration, through its role in the transmission of vibration from the rail to the bridge. Laboratory measurements have been made in this work to characterise the vibration transmission
properties of two important types of track support structure on bridges; ballasted track
and two-stage resilient baseplate track. Improved methods of modelling the dynamic behaviour of these track forms have been developed from the measurements, which
can be used in calculation models for both bridge noise and also for rolling noise.
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