Ibration Transmission Characteristic Of Rail Fastenings In Metro Track

To avoid the negative effect on sensitive area near metro lines by the vibration and noise caused by underground operation, various measures are applied widely to the metro lines, among which, vibration damping fastenings is a widespread medium measure. However, after taking these measures, some problems, such as rail corrugation and rail vibration increasing, still exist. In terms of field research, there is a close relationship between rail corrugation and the fastening in some section of the metro lines. Therefore, from perspective of fastening structure, also combined theory calculation and field test, analyses about the rail and fastening vibration property were carried out in this thesis, the main research details and conclusions are as follows:(1)Four kinds of fastening finite element model were built, which were type III egg fastening, GJ-III vibration damping fastening, DTVI2fastening and e fastening, vibration transmission characteristic were analyzed, which indicated that, the natural frequency of III egg fastening and GJ-III vibration damping fastening were126Hz and242Hz respectively, both of which were at the frequency related with rail corrugation.(2)Four track finite element models, with the four fastening introduced above, were developed. Through analyzing the vibration transmission characteristics, it was found that, vibration damping fastening track could only work at certain frequency band. Then, the mode shapes indicated, at some frequency, there would have anti-resonance between the rail and base plate, as a result, the stiffness under the rail was actually larger than static stiffness, and then it could lead to lose the vibration damping effect and increase the rail vibration.(3)Four vehicle-track coupling dynamic models were built, by analyzing the dynamic property, it was found that, the damping of fastening, vehicle speed, rail irregularity and the modeling ways of fastening could have an influence on the dynamic characteristics. Also, it was showed that, modeling the fastening as a spring was unreasonable because it was not able to show the vibration property itself.(4)Hammer tests were carried out on four track structures, which presented that, the natural frequency of III egg fastening was126Hz, agreed with theory computing. It was also found that the vibration damping effect of track with vibration damping fastening was corresponding to the exciting frequency. In the meantime, the fastening acceleration was higher than that of rail in track with III egg fastening (GJ-III vibration damping fastening)at119-732Hz(261-706Hz), which means anti-resonance happen and vibration damping effect does not work at these frequencies, also agreed with theory calculating.(5)Train running test of vibration was conducted on GJ-III vibration damping fastening and e fastening, the results showed that, rail vertical acceleration of this two tracks was very close, however, fastening acceleration of tack with GJ-III vibration damping fastening was much higher than that in track with e fastening, when the frequency of excitation was0～1000Hz, both of the acceleration of rail and fastening in track with GJ-III vibration damping fastening was higher than that in track with e fastening. In addition, because of the same laying environment of these two tracks, it could be indicated that, GJ-III vibration damping fastening did not work well as expected.