A unified approach to numerical modelling of traffic induced vibrations

This paper presents a unified approach for the prediction of free field vibrations due to road or rail traffic. It is assumed that the road or track and the (horizontally layered) soil are invariant in the longitudinal direction so that the dynamic road/track-soil interaction equations can be formulated in the frequency-wavenumber domain. Dynamic train axle loads are computed accounting for the track compliance in the moving frame of reference; in the case of road traffic, the compliance of the tyres is much higher than the compliance of the road-soil system so that the latter can be disregarded. The free field response due to moving loads is computed applying the dynamic reciprocity theorem, which can be simplified when the vehicle speed is low with respect to the body wave velocities in the soil. A first numerical example illustrates how free field vibrations due to road traffic can efficiently be predicted on a large three-dimensional mesh of receiver points. A second example considers the vibration isolation efficiency of a floating slab track. For the unisolated and the floating slab track, the free field response is compared for the passage of a single tram axle on uneven rails.