Abstract
As train speeds, axle loads, and tonnage increase on North American freight railroads, improved sleeper and fastener designs that are both economical and serviceable may be necessary to maintain acceptable track safety and quality in these high demand environments. TTCI continues to evaluate the performance of various sleeper and fastener systems at its Facility for Accelerated Service Testing (FAST) High Tonnage Loop (HTL) under heavy axle load (35.4-tonne) traffic. The objective of this testing is to assess the relative performance of these sleeper and fastener systems throughout their lifecycle and how certain failure modes affect track performance. Working with North American railroads, specific sleeper and fastener designs were chosen for this testing. The test section includes zones of hardwood and softwood sleepers with and without elastic fasteners, polymer composite sleepers with both elastic and cut spike fastening systems, and a variety of concrete sleepers and fastening systems. These test sections are located in a 290 meter radius curve on the HTL. TTCI is documenting the observed failure modes and assessing performance of these systems with the following performance tests: gage restraint measurement system (GRMS) testing; lateral track loading fixture (LTLF) testing; and track geometry measurement. The GRMS and LTLF testing are two ways to apply a gage widening load to the track to assess the fastening system’s ability to resist gage widening. GRMS testing is performed using an in-motion vehicle with a deployable loading axle, while LTLF testing involves a statically applied load. The systems being tested have exhibited various failure modes including severe plate cutting on the softwood sleepers, raised cut spikes and broken sleeper plates on polymer composite sleepers, and broken concrete tie insulators, particularly on narrower field side insulators. The track geometry, GRMS and LTLF results demonstrate the manifestation of these failure mechanisms in track performance. Currently, the results of this study are being used to develop a novel dynamic vehicle/track simulation model that incorporates connections at the sleeper and fastening system level. The application of this modelling approach to predicting service failures and guiding sleeper and fastener purchasing and maintenance decisions is presented.