Research On Effects Of Improvements And Parameters On Vibration Characteristics Of Ladder Track System On Bridge

ABSTRACT:More and more vibration reduction measures are being used in subway lines, among which the ladder track is one of the most popular ways. However, serious track vibration and noise incidents were observed in some ladder track subway line, even some rail corrugation were also observed. In this circumstance, some research institutes proposed a new type of ladder track improved. On the basis of related domestic and aboard research, the transfer and running dynamic characteristics are studied in this paper, then the effects of the parameters on vibration characteristics of ladder track are also studied. The main research contents and conclusions are as follows:1) Models of transfer characteristics of ladder track on bridge before and after improved are developed respectively in ANSYS FEM Software and then the vibration transfer characteristics are studied. It shows that:compared with ladder track before improved, the after-improved one has hardly effects on the rail vibration at the rail corrugation frequency, but it can reduce the sleeper vibration at that frequency. From the aspect of vibration mode, the before-improved sleeper has great deformation with "M" or "W" shape at the rail corrugation frequency, however, torsion deformation come out for the after-improved sleeper.2) Models of running dynamic characteristics of ladder track on bridge before and after improved are developed respectively in ANSYS/LS-DYNA Software and then the dynamic characteristics are studied. It shows that:the rail, sleeper, bridge maximum acceleration decreased in turn, which illustrates the vibration in the vertical propagation path obtained the attenuation, vibration acceleration level attenuates18dB,34dB for the before-improved ladder track, it is25dB,38dB for the after-improved ladder track. Then the sixth grade track irregularity of U.S. is taken into consideration, the result shows that, the acceleration is much larger than the one without track irregularity, but the attenuation amount is closed,18dB,33dB for before-improved and22dB,37dB for after-improved in turn.3) The effects of support parameters under the sleeper (spacing of pads, end pads, pads stiffness, pads damping)and sleeper size parameters(cross-section width, sleeper length) on ladder track vertical vibration characteristics, especially on the second order vertical resonance of sleeper, the main reason of rail corrugation, are carried out. The conclusions show that:spacing of pads, pads stiffness has litter effect on vibration of rail and sleeper at rail corrugation frequency. End pads, increasing pads damping, increasing cross-section width can control the vibration of rail and sleeper at rail corrugation frequency. In the meantime, although decreasing the pads spacing and increasing pads damping can reduce the vibration of rail and sleeper at some frequency, the vibration of bridge increased. Increasing pads damping can reduce the rail vibration at rail corrugation frequency, but the vibration of sleeper and bridge at low frequency will increased. Different sleeper length has different degree effect on the vibration of rail and sleeper at rail corrugation frequency.