Track Modulus Assessment of Engineered Interspersed Concrete Sleepers in Ballasted Track

Abstract

Ballasted railway track is typically constructed using sleepers that are manufactured from a common material type within a given length of track. Timber and concrete are the two most common sleeper materials used internationally. Evidence from historical installations of interspersed concrete sleepers in timber sleeper track in North America has indicated inadequate performance, due largely to the heterogeneity in stiffnesses among sleepers. Theoretical calculations reveal that interspersed installation, assuming rigid concrete sleepers and supports, can result in rail seat forces more than five times as large as the force supported by the adjacent timber sleepers. Recently, engineered interspersed concrete (EIC) sleepers were developed using an optimized design and additional layers of resiliency to replace timber sleepers that have reached the end of their service lives while maintaining sleeper-to-sleeper stiffness homogeneity. To confirm that the concrete sleepers can successfully replicate the stiffness properties of the timber sleepers installed in track, field instrumentation was installed under revenue-service train operations on a North American commuter rail transit agency to measure the wheel–rail vertical loads and track displacement. The results indicated that there are minimal differences in median track displacements between timber (2.26 mm, 0.089 in.) and EIC sleepers (2.21 mm, 0.087 in). Using wheel-load data and the corresponding track displacements associated with each wheel load, track modulus values were calculated using the single-point load method based on beam on elastic foundation (BOEF) fundamentals. The calculated values for the track modulus indicated similar performances between the two sleeper types, with median values of 12.95 N/mm/mm (1878 lbs./in./in.) and 12.79 N/mm/mm (1855 lbs./in./in.) for timber sleepers and EIC sleepers, respectively. The field results confirmed the suitability of the new EIC sleeper design in maintaining a consistent track modulus for the location studied, thus evenly sharing loads between and among sleepers manufactured from both concrete and timber.

Special Issue “Extreme Sciences and Engineering II”

“…Lima et al [12] evaluated that railway-engineered interspersed concrete (EIC) sleepers can successfully replicate the stiffness of timber sleepers installed in tracks using field instrumentation installed under revenue-service train operations on a North American commuter rail transit agency to measure the wheel-rail vertical loads and track displacement. The results indicated that there are minimal differences in median track displacements between timber (2.26 mm, 0.089 in.)…”

Multi-Hazard Effects of Crosswinds on Cascading Failures of Conventional and Interspersed Railway Tracks Exposed to Ballast Washaway and Moving Train Loads

“…Previous studies have shown that the interspersed method is more economical than fully replacing aged timber sleepers [ 9 ]. The interspersed railway systems have enough track quality to operate with a considerable train speed under normal weather conditions [ 13 , 14 , 15 , 16 , 17 , 24 ]. Nevertheless, the approach would result in inconsistent track stiffness due to the elasticity difference between the renewed concrete sleepers and the unreplaced aged timber sleepers [ 15 , 25 ].…”

Response of Strain-Gauge-Based Tie Reaction Measurement Circuits under Dynamic Loading and Variable Support Conditions

“…These sensors do not require significant modification to track components during the installation process. Over the past few decades, research on strain-gauge-based systems for track response monitoring has been noticeable ( 1 – 33 ). Although the use of strain-gauge-based systems for train-induced wheel-load measurement is relatively common, only a few studies have recently reported the use of these systems for rail–tie interaction force measurement ( 2, 5, 7, 9, 13, 14, 26, 27, 29–33 ).…”