Abstract
As an artificially engineered metamaterial, locally resonant phononic crystals (LRPCs) exhibit great potential for the vibration reduction of urban rail transit due to their capability to prohibit the propagation of elastic waves with long wavelengths. This study proposes a wave-resistance sleeper with negative dynamic mass density by periodically embedding LRPCs into the concrete sleeper and provides new approaches to improve its bandgap property. Furthermore, the vibration reduction effect of the wave-resistance sleeper applied in a slab track was evaluated with a three-dimensional half-track model. The results show that the wave-resistance sleeper has two bandgaps below the frequency of 2000 Hz and can effectively prohibit the vibration within the bandwidth from transmitting to the track bed. Setting intervals in the rubber coating and increasing the void fraction can significantly reduce boundary frequencies of the first bandgap, whereas the second bandgap attenuates completely as the vibration can no longer be localized in the discontinuous rubber coating. A larger metal core is beneficial for obtaining a wider bandgap in the low-frequency range, whereas a thicker rubber coating can be used to obtain a wider bandgap in the medium-frequency range. To obtain wider bandgaps, the steel tube used should be as thin as possible and the use of an oval metal core should be avoided. It is hoped that the research results can provide a useful reference for the vibration reduction of track in rail transit.
Highlights
In recent years, the development of urban rail transit has effectively relieved the pressure of urban passenger traffic and accelerated the prosperity of cities
The environmental vibration induced by train operation has considerable effects on the routine life and work of residents living along traffic-lines as well as on the safety of ancient buildings under key protection
The working mechanism of ordinary vibration reduction measures in tracks, such as vibration-damping fastener, elastic sleeper track, and floating slab track (FST), is suppression of vibration transmission based on the vibration isolation principle by inserting elastic pads between components of the track
Summary
The development of urban rail transit has effectively relieved the pressure of urban passenger traffic and accelerated the prosperity of cities. 21 and 22 discussed the effects of dynamic vibration absorbers (DVAs) on the dispersion and vibration properties of the track, in which DVAs were considered as locally resonant units attached periodically to the rail. In order not to affect the original stiffness of the track, new vibration reduction concepts that have minor effects on the track stiffness, such as embedding the LRPCs in the concrete components of the track or attaching the locally resonant units on rails, could be considered in the design. A wave-resistance sleeper is proposed by periodically embedding two-dimensional ternary LRPCs into a concrete sleeper to improve the vertical vibration mitigation performance of the track, and the physical mechanism of the bandgap property is studied through the analysis of its dynamic mass density. The theoretical vibration reduction effect of the proposed wave-resistance sleeper applied in the slab track is discussed using a three-dimensional half-track model
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