Verification of an Empirical Prediction Method for Railway Induced Vibration

Summary

The Detailed Vibration Assessment is an empirical procedure developed by the U.S. Federal Railroad Administration (FRA) for the prediction of railway induced vibration and re-radiated noise. The vibration velocity level in the free-field is predicted with a force density, characterizing the source, and a line transfer mobility, characterizing the transfer of vibration due to a line load. The line transfer mobility is determined with in situ measurements of transfer functions. The force density is obtained by subtracting the line transfer mobility from the vibration velocity level due to a train passage. It is assumed that the resulting force density can be used to predict the vibration velocity level at other sites with similar train and track characteristics. In this paper, the influence of the soil characteristics on the force density and the resulting vibration velocity level predicted with the FRA procedure is investigated. Numerical simulations are used to compute the vibration velocity level and the line transfer mobility at three sites with different soil characteristics. From these results, the force density due to a train passage is determined for each site. Finally, the three force densities are used to investigate the influence of the soil characteristics on the predicted vibration velocity level due to a train passage.