Experimental Study of Rail Beam Joint Bolt Loosening Impact on Rail Structure Vibration in High-Speed Maglev Maintenance Base

Abstract

Objective During the train debugging process, significant vibrations may occur in the steel rail beams of high-speed maglev maintenance bases due to their unique structural characteristics, potentially leading to bolt loosening issues. This phenomenon could alter the vibration characteristics of the rail beams, and changes in the parameters of the vehicle-track coupling system might induce vehicle-track resonance, posing potential harm to rail structure. Therefore, it is essential to investigate the impact of bolt loosening on the vibration of rail structures. Method After expounding the experimental design scheme and principles, the impact of bolt loosening on the modal and dynamic response characteristics of the rail beam and structure are investigated. For structural modal analysis, pulse and ambient excitations are employed to test the track modal properties under both unloaded (the rail is unoccupied) and loaded (the rail is occupied by a train) conditions. Modal identification is carried out using the method of Stochastic Subspace Identification (SSI). Finally, the impact of loose bolt on rail modal properties under both conditions are analyzed through stability diagrams. In terms of dynamic response characteristics, levitation excitation is applied to the rail, and the bolt is gradually loosened during multiple times of static levitation process. Acceleration response signals of the steel beams are collected and a detailed analysis is conducted in both time and frequency domains. Result & Conclusion Bolt loosening, under both loaded and unloaded conditions, caused a decrease in modal frequencies and a change in mode shapes. But under the loaded condition, a considerable increase in the damping ratio is observed after bolt loosening. In the static levitation process, resonance occurred between the rail beam and the train, where bolt loosening not only affected the amplitude of the rail beam vibrations but also altered the symmetry of rail beam vibrations.

Keywords

• high-speed maglev transit
• rail beam
• bolt loosening
• rail structure vibration
• modal test