Study on control limits for track longitudinal irregularities measured by 60 m chord on high-speed railway

The high-speed railway (HSR) operates at a high velocity, and the long-wavelength track irregularities can affect its safety and stability. The study was conducted to address control and management issues related to long-wavelength track irregularities on HSRs. It achieved this by establishing a vehicle-track dynamic analysis model based on the multi-rigid-body dynamics theory, aiming to provide recommendations for the development of standards for managing the track irregularities on HSRs. A simulation was conducted to analyze how the train speed, wavelength, and amplitude of track longitudinal irregularities affect the vehicle body’s dynamic response. The variation of the vehicle body’s dynamic response under different working conditions was analyzed, and the most unfavorable wavelength and sensitive wavelength ranges of the track longitudinal irregularities on HSR were studied. The control limits for track longitudinal irregularities measured by a 60 m chord were then determined. The findings indicate that the car body's vertical acceleration gradually decreased with the increase of wavelength but increased linearly with the increase of amplitude. The findings also indicate a gradual increase in the vehicle body’s vertical acceleration as the train speed increases. When the train speed is 250 km/h∼350 km/h, the sensitive wavelength range of long-wavelength track irregularities is 60 m∼110 m. Based on the results, the relationships between the wavelength and the amplitude of track irregularities, train speed, and the vehicle body’s vertical acceleration were acquired by the nonlinear least square method. Finally, a formula for calculating the control limits for track longitudinal irregularities measured by a 60 m chord is proposed.