Analysis of T-bolts Abnormal Fracture of DTⅥ2 fastener Based on Metro Pass-by Dynamic Monitoring

Abstract

For the problem of T-bolts abnormal fracture in DTⅦ2 fastener at a bridge section of Beijing metro line, dynamic monitoring is done which includes vibration acceleration and rail corrugation. The monitoring results indicate that there exists short-wave corrugation of 25mm at this section. And in the fracture section rail and T-bolts vibration increase abnormally. The vibration resonance peak is around 700-800 Hz. There is a significant correlation between characteristic wavelength, resonance frequency and train speed. Rail and T-bolts vibration transfer ratio shows that there exist the phenomenon of vibration amplification and asynchronous phase at 700-800 Hz. Further analyses indicate that the main reason of T-bolts abnormal fracture is fastener system abnormal matching. It causes vibration transfer ratio amplification at 700-800 Hz, and the vibration asynchrony of rail and T-bolts which causes abnormal interaction force. The short wave corrugation of 25mm leads to wheel-rail vibration, which inputs too much vibration energy to the fastener system.