Papers by Keyword: Railway Track

Abstract: The operation of railway tracks is historically confirmed that the classic structure of the railway superstructure is capable to ensure operational capability of standard railway tracks for a relatively long period of time (railways tracks to speed of 160 km.h^-1). Such a railway track and its track is considered the railway track with a classic structure of the railway superstructure, where track removal is stored in the ballast. In the case of high operating and axle load, increasing track speed and requirements for safety of operation, which are associated with high requirements on the track geometry, it appears that such structure has its operational (in terms of guaranteeing the long-term safety and reliability of the railway track) and economic (in terms of the cost of maintenance of railway track) limits. "Floating" placement of the track removal during each passage of a rail vehicle, or train leads to the growth of dynamic horizontal and vertical forces that cause gradual degradation of track geometry, what subsequently leads to restless journey of moving rail vehicles. Elimination of imperfections in track geometry - the quality of the railway track - forces the operators to remove such imperfections of railway track in time and financially consuming maintenance work in certain periods. However, it is sufficient if only the weakest element of classic railway superstructure is replaced in the railway, and it is the track ballast using other more appropriate component representing no elastic and plastic behaviour. The structure is such replacement, in which the track removal is concreted (monolithic structure) or stored on a concrete or asphalt bearing layer (layered structure), namely structural design, which is referred to as unconventional railway superstructure. The structure of railway superstructure is characterized by cross sleepers used in a modified shape or they are not part of it at all. Currently, thus conceived railway track is referred to as a slab track (hereinafter referred to as the "ST"), which requires flexibility of the railway superstructure for the system of the wheel/rail secured using elastic elements disposed between the rail and the sleeper and/or under the sleeper. In general, the structure of ST has been currently applied mainly to high-speed track and the tracks that have high operational load, where the cost of maintaining the track with the classic structure of the railway superstructure strongly grows. At the same time, however, this structure also promotes in the upgraded sections of the standard tracks (track speed to 160 km.h^-1), especially in track sections conducted in tunnels, as there are located the required properties of the ballast that do not demonstrate subsidence. The subgrade without a drop also offers for application of the ST structure bridges, and therefore, the application of this structure is also possible in these track sections.

Abstract: To avoid an unnecessary catastrophic accident due to a failure of a railway track, it is important to have a reliable condition monitoring system for the railway track. The integrity of the railway track can be assessed by monitoring the displacement field of the track, which can then be used to determine the strain and stress field. By knowing the stress history of the track and the S–N curves of the track material, the remaining life of the railway track can be predicted. In the present work, a simple system to monitor and record the displacement field of the railway track has been developed by using Digital Image Correlation (DIC) technique. The set–up to monitor the displacement field of the railway track was developed using a high speed video camera of Nikon J1 to capture the image of the railway track when the train passing through. The DIC technique was then employed off line to measure the displacement field of the 2D image captured. The results showed that the full field displacement measured by using DIC technique gives a good agreement compared to the finite element results. The full field displacement can be used to calculate the strain-stress field, and later on the remaining life assessment can be conducted based on the results.

Abstract: Considering local sleepers supported invalidly, the dynamic analysis is presented for ballastless railway track system subjected to moving loads. The track is modeled as an infinitely Euler-Bernoulli beam with Kelvin viscoelastic foundation. The restrain conditions of system change suddenly at unsupported sleepers. Numerical simulating was carried out by the finite element discrete and Newmarks-method. Dynamic responses of system were analyzed in the case of single or multi-sleeper to be not working properly. Results show that the maximum value of displacement of track is going up 50% approximately due to an invalid sleeper occurring. The amplitude of vibration is two times increase when three sleepers to be hung up. Hence, there would be a bad effect on the vibration control of ballastless railway track system as some sleepers lose efficacy continuously.

Abstract: Applied theory of vehicle/track coupled dynamic, random vibration properties of high-speed railway vehicles are researched in random parameters of fastener and ballast stiffness obeyed normal distribution and track irregularity combined the sample of artificial shortwave and the sample of low disturbance irregularity of high-speed railway in German with train speed increase. The results show that dynamic interaction of vehicle/track system and vibration responses of railway vehicle are increased with train speed increase, but the increase of wheel-set acceleration is much more. The parameters of high speed railway track structure (especially fastener and ballast stiffness) had much more impact to random vibration responses of vehicle/track system, so they should be optimized and remained in a narrow range.

Abstract: A new technique is present in this paper that transforms the railway track irregularity power spectral density of left and right rails into the excitation power spectral density of wheelset of train, compared with the railway track irregularity spectrums of left and right rails which are not the direct inputs of simulation dynamic model of trail. A parameter model is chosen as the model of excitation spectrum and parameters fitting result shows that this model is suitable for the excitation spectrums of traversing, floating and head shaking, and the method present in this paper is effective.