University of Birmingham Aerodynamic forces on railway acoustic barriers

Aerodynamic measurements were conducted to assess the magnitude of pressures measured on a range of acoustic barriers during normal working traffic. A week of measurements were made at a number of tests sites, capturing data for a range of train types. The different test sites allowed for a novel assessment of the influence of barrier distance from centre of track and any influence from other trackside infrastructure. Results exhibited a characteristic pressure development measured on the acoustic barrier, as observed in previous studies, with similar magnitudes recorded for all high speed passenger trains. Pressure magnitudes were largest around the train nose and tail regions. A twelve car train had an additional large peak due to the coupling of two six car sets. As barrier distance from centre of track was increased the magnitude of pressures measured was shown to decrease. Fitting a curve of best fit to the results indicated that the same curve form could be used for both the positive and negative nose pressures. Differences in peak pressure magnitudes were observed for results measured underneath the footbridge suggesting a potential influence of the footbridge on the aerodynamic flow development. CEN standards were shown to offer a good estimation to the pressure coefficient measured on the barrier at most positions analysed. Analysis of peak pressure magnitudes in relation to the number of train passes across the barrier life span, calculated through a rainflow analysis, suggested that small pressure fluctuations were the dominant feature across all measurements. Larger fluctuations depended on train type and as such load calculations should account for the different types of traffic observed on the railway. This study presents a novel series of aerodynamic measurements undertaken by the University of Birmingham to assess the magnitude of pressures measured on a range of acoustic barriers during normal working traffic. The measurements were made to analyse the effects of high speed passenger train aerodynamics on acoustic barriers, to support the knowledge base of structures located on the high speed infrastructure. A week of measurements were made at a number of tests sites along the railway, as discussed in section 2.1. The train types recorded and experiment methodology are presented in section 2. The techniques and methodology for analysing the data are discussed in section 3. A discussion of experimental uncertainty is presented in section 4. An overview of the characteristic pressure development is given in section 5.1. This is expanded to discuss influencing factors on peak pressure magnitudes, sections 5.3 to 5.5. Peak pressure results are compared to values calculated using the CEN standards methodology, section 5.4, and an estimate to the load force measured on the acoustic barrier is made, were possible, in section 5.6. Finally, an analysis of fatigue loads is made by assessing the magnitude and frequency of dynamic pressure loads experienced by the acoustic barriers, given in section 5.7. The analysis is expanded to include for the first time a rainflow type analysis of pressure fluctuations, assessing how fluctuations relate to the types of barriers and