Nonlinear Train-Track-Bridge Interaction With Unsupported Sleeper Group

One of the main characteristics of the ballasted track compared to the slab track is the ability to reduce the level of vibration on the bridge surface. however, due to factors such as the asymmetric or permanent settlement of the ballast layer (compaction), crushing, or moving of ballast particles, a gap between sleeper and ballast appears. this problem intensifies vibrations in the track and, as a result, can affect the dynamic response of the bridge. so far, the lack of scientific attention to this issue on the railway bridge is noticeable. hence, in this article, by examining a nonlinear dynamic model of traintrackbridge interaction, the effect of the unsupported sleeper on the dynamic behavior of a concrete railway bridge is studied. for this purpose, the influence of a suspended sleepergroup at the different positions along the bridge span, in a range of train speed and gap size, are investigated. it is demonstrated that for the case of the unsupported sleepergroup within the 2/8 and 5/8 of the bridge span, the acceleration of the bridge reaches its maximum. also, the maximum load on the deck of the bridge increases by 45 to 60%.