Experimental assessment of the dynamic behaviour of the train-track system at a culvert transition zone

This article describes the experimental assessment of the dynamic behaviour of the train-track system at a culvert transition zone located at the Northern line of the Portuguese railway network. Based on receptance tests, the dynamic flexibility of the track along the transition was characterised. From the full track resonance frequency, a reduction of 60% was observed on the dynamic flexibility of the track on the structure in relation to the track on the embankment; The dynamic response of the track was also monitored in different sections for the passage of the Alfa Pendular trains at a speed of 220 km/h. Based on these tests, it was concluded that the displacements of the track on the structure and on the transition wedge were, respectively, 45% and 30% lower than those of the track on the embankment. Despite the significant variations of the dynamic stiffness of the track, the accelerations of the sleepers, after the application of a low-pass filter for eliminating contributions from irregularities of the track and of vehicle wheels, did not exhibit relevant variations along the transition zone. Likewise, no substantial variations were registered in terms of the dynamic loads applied by the train at the monitored track sections. Finally, synchronized measurements of the dynamic response of the track and of the inspection vehicle EM 120 were made at a speed of 100 km/h, where no significant amplifications induced by the transition were recorded for the accelerations on the axles, on the bogies and on the vehicle box.