a field investigation on the effects of using usps in transition zone from ballasted track to bridges

Transition zone is one of the vulnerable sections in railway tracks. this study was conducted to assess the effects of using under sleeper pads (usps) in the transition zone from ordinary ballasted track to railway bridges. for this purpose, a railway bridge with two spans (with the length of 7 m) and an overall length of 15.5 m was selected, followed by designing and conducting field tests in three states: (1) without usp, (2) with usp only on bridge section, and (3) with usp on bridge section and transition zone. the vibrational behavior of the bridge and track components was monitored during train passage by the installation of accelerometers on the bridge, rail, sleeper, and installation of linear variable displacement transducer beneath the bridge deck. the results showed that the maximum effects of using usps in the transition zone were in the first span so that the average value of accelerations in all speeds decreased in the first span. the acceleration of the rails in the third experiment was 4% lower than the second one and 35% lower than the first one. this reduction for sleepers was 9% and 24%, respectively, and for the bridge deck, it was 48% and 66%, respectively.