Influence mechanism of vertical dynamic track irregularity on train operation stability of long-span suspension bridge

The track needs to maintain sufficient foundation stiffness to ensure its smoothness and meet the operation stability requirements of high-speed trains. However, the train-induced deformation of flexible suspension railway bridge will inevitably induce the obvious vertical dynamic track irregularity and threaten train operation stability. Combined with a long-span suspension bridge with a main span of 1092 m, this paper provides a new analysis framework for evaluating the track smoothness on the long-span bridge from the perspective of train operation stability. The comprehensive train-track-bridge coupling vibration analysis is conducted to highlight the impact factors on train operation stability and identify the dynamic track irregularity. The simplified evaluation framework of dynamic track irregularity are then proposed to evaluate the track smoothness. The results show that the vertical dynamic track irregularity of long-span bridges is obviously affected by action of train, random track irregularity and overall temperature load. It is quite different from the static track irregularity in terms of alignment and spatial frequency. By separating the dynamic track irregularity according to the wavelength limit of 200 m, two alignment evaluation methods are proposed, namely the mid-chord measurement within 200 m wavelength and curvature method above 200 m wavelength, to reveal the different contributions of dynamic track irregularity component to the vertical car-body acceleration. The influence mechanism of dynamic track irregularity caused by different factors on the stability of train operation is finally identified from the perspectives of vibration acceleration and centrifugal acceleration.