Under sleeper pads—Influence on dynamic train–track interaction

The influence of under sleeper pads (USP) on dynamic train–track interaction is investigated in a parameter study. Two numerical models that are valid in different frequency intervals are used. The time-domain model DIFF is used to study wheel–rail contact forces, rail bending moments, rail vibrations (displacements, velocities and accelerations), sleeper vibrations and loads on sleepers at high frequencies, here 50–3000 Hz. The frequency-domain model GroundVib is adopted to calculate sleeper vibrations at low frequencies. Frequency-dependent material properties of rail pads, USP and ballast/subgrade are accounted for by viscoelastic spring–damper models that are calibrated with respect to measured data. It is found that USP influence dynamic train–track interaction mainly in the frequency range 0–250 Hz. Similar sleeper responses are calculated by the two models, although some differences in magnitudes are present.