Mechanics-based model to predict ballast-related maintenance timing and costs

A mechanics-based model has been developed which predicts the timing of required ballast maintenance based on track settlement and roughness. With user-defined track material properties, loading characteristics, and maintenance technique to be applied, the model determines the rate of track roughness increase and applies the desired maintenance when such roughness exceeds a limit. This analysis is continued, usually over the life of the ballast, and the related life cycle cost is calculated. For another ballast material or maintenance technique, a lower or higher cost may be realized. In this way, the model user may observe the effect upon ballast maintenance and cost of using concrete rather than wood ties, a heavier axle load, or increasing the track stiffness. Because the life cycle cost is used, the frequent mistake of determining purchasing decisions based upon the least cost in the present is avoided. Instead, the model allows the user to optimize by considering the associated costs incurred during the component life

A Method to Characterize Cyclic Error in the Track Geometry Waveform

A method [1] has been found to identify the presence of multiple cycles of harmonic error within track geometry measurement waveforms. This cyclic track geometry error can produce a buildup of resonant motion in vehicles, but may not be readily apparent from viewing the geometry error because it is often masked by the complexity of the waveform. However, due to the resulting large accelerations and poor ride quality, the dynamic rail vehicle response to the cyclic error will be unmistakable when the wavelength is at or close to a resonant frequency of the car body. Cyclic geometry error usually is unobserved and left uncorrected by maintenance because the associated mid-chord offset geometry error is typically far less than the safety limit per FRA. However, by using a band-pass filtering function on profile and alignment space curve data from the Amtrak geometry car, the presence and magnitude of any cyclic error becomes apparent. Further, it was found that shortcomings in the software used to calculate instructions for the tamper limit the effectiveness of tampers to remove the longer wavelengths commonly associated with this cyclic error. Therefore, improved methods to surface track with longer wavelength error are also being investigated.</jats:p

Comparing Geometry Correction Capability of AGGS and TGCS Tamper Control Systems on Amtrak’s Northeast Corridor

One of Amtrak’s high-speed continuous action tampers has been fitted with TGCS (Track Geometry Control System) tamper control software to compare the quality and durability of geometry correction it provides with that of the existing tamper control system, AGGS. Comparison between the two systems is made by reviewing measured track geometry data from before and after maintenance, and by reviewing changes in ride quality accelerations of instrumented passenger cars. Although the testing program is in its early stages and the number of test locations so far is limited, results to date are very much in favor of TGCS.</jats:p