Railway impact-induced ground vibration in urban environments: fast hybrid prediction and experimental validation

Railway turnouts and rail discontinuities are important sources of localized ground-borne vibration, particularly in urban environments. Accurate prediction of vibration generated by wheel–rail impact typically requires computationally expensive modelling of vehicle–track-soil interaction, limiting its practical use to specific situations that require high accuracy and detailed analysis. To provide fast yet reliable predictions, a hybrid methodology is developed that combines simplified wheel-rail interaction models with detailed ground vibration assessment. Based on the wheel trajectory, the time history of the wheel-rail interaction forces is computed using a reduced 2-DOF track model tuned to match the rail receptance at the impact location. This model is coupled to the unsprung mass of the vehicle through a non-linear Hertzian contact stiffness. The interaction forces are subsequently transformed into an equivalent force density spectrum using Fourier analysis. Following the FTA/FRA procedure for Detailed Vibration Assessment, ground vibration velocity levels are predicted as the sum (in dB) of the force density and the line source transfer mobility (LSTM). The force density considers excitation due to both localized rail discontinuities and combined wheel-rail roughness, while the LSTM is calculated using a 2.5D finite element-boundary element track-soil model. Extensive measurements on the urban tramway network of Lyon, including rail receptance, wheel trajectories, LSTM and ground vibration near multiple rail joints, as well as detailed 3D non-linear vehicle–track models are used to assess the accuracy of the proposed hybrid methodology. The reduced computational effort also enables evaluation of variations in wheel trajectory, train speed and unsprung mass.