Abstract
With dynamic behaviour different from that of traditional discretely supported tracks, continuously supported embedded rail systems (ERSs) have been increasingly used in railway bridges, level crossings, trams, and high-speed lines. However, studies on ERSs have been limited, and none of them have addressed the wheel-rail impact-induced dynamic response, although wheel-rail impact is a main cause of ERS degradation. This paper studies, numerically and experimentally, the wheel-rail impact at an insulated rail joint (IRJ) used in the ERS. As a weak spot of the track, the IRJ results in discontinuities in the track support stiffness and wheel-rail contact geometry. This study first develops an explicit finite element model to simulate the vibration responses of the IRJ in the ERS when excited by a hammer and passing wheel loads. The simulated dynamic behaviours (represented by the hammer-excitation frequency response function) at a frequency up to 5 kHz and a wheel-rail impact vibration frequency up to 10 kHz are then validated with a field hammer test and a train pass-by measurement, respectively. Both the experimental study and numerical modelling reveals that the major frequencies of the impact vibration at the IRJ in the ERS depend mainly on geometric irregularities in the IRJ region and the train speed, rather than on the resonances of the track structure, as in the case of the discretely supported IRJ. This finding is meaningful to the engineering practice because it indicates a continuously supported IRJ in the ERS is more impact resistant, especially when the IRJ geometry is adequately maintained, e.g. by timely grinding.
Highlights
An embedded rail system (ERS) presents an innovative constraint mechanism for the rail by providing continuous elastic support [1,2,3]
By comparing the dynamic behaviour and the impact vibration of the EIRJ to those of the discretely supported insulated rail joint (IRJ) reported in [23], this study finds that the dominant frequencies of the impact vibration at the EIRJ depend mainly on the geometric irregularities in the IRJ region and on the train speed rather than on the resonances of the track structure, as in the case of the discretely supported IRJ
WhereHij(f) is the FRF measured with the accelerometer Si (i = 1,2,3,4,5,6) when hitting the position close to the accelerometer Sj (j = 3,4); SaiFj is the cross-spectrum between the force Fj and the acceleration ai, and SFjFj is the auto-spectrum of the force Fj
Summary
An embedded rail system (ERS) presents an innovative constraint mechanism for the rail by providing continuous elastic support [1,2,3] In this system, the rail is enclosed and bonded by an elastic poured com pound (EPC) in a steel or concrete groove (see Fig. 1). Compared with the traditional track supported by sleepers and ballasts, the ERS reduces the track height and weight and requires less maintenance work [4] It has the advantage of providing an obstacle-free surface with a lower construction height for crossing traffic. Owing to these advantages, the ERS has been increasingly used in railway bridges, level crossings, trams and high-speed lines since the 1970s [5,6,7,8,9]. Worth noting that when severe degradation occurs, e.g., cracks and debonding [10], the replacement cost of the ERS can be much higher than that of the traditional track
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