Analysis of the Relationship Between Rail Seat Load Distribution and Rail Seat Deterioration in Concrete Crossties

Abstract

One of the most common failure modes of concrete crossties in North America is the degradation of the concrete surface at the crosstie rail seat, also known as rail seat deterioration (RSD). Loss of material beneath the rail can lead to wide gauge, rail cant deficiency, and an increased risk of rail rollover. Previous research conducted at the University of Illinois at Urbana-Champaign (UIUC) has identified five primary failure mechanisms: abrasion, crushing, freeze-thaw damage, hydro-abrasive erosion, and hydraulic pressure cracking. The magnitude and distribution of load applied to the rail seat affects four of these five mechanisms; therefore, it is important to understand the characteristics of the rail seat load distribution to effectively address RSD. As part of a larger study funded by the Federal Railroad Administration (FRA) aimed at improving concrete crossties and fastening systems, researchers at UIUC are attempting to characterize the loading environment at the rail seat using matrix-based tactile surface sensors (MBTSS). This instrumentation technology has been implemented in both laboratory and field experimentation, and has provided valuable insight into the distribution of a single load over consecutive crossties. A review of past research into RSD characteristics and failure mechanisms has been conducted to integrate data from field experimentation with existing knowledge, to further explore the role of the rail seat load distribution on RSD. The knowledge gained from this experimentation will be integrated with associated research conducted at UIUC to form the framework for a mechanistic design approach for concrete crossties and fastening systems.

Evaluation of Laboratory and Field Experimentation Characterizing Concrete Crosstie Rail Seat Load Distributions

“…It is hypothesized that this increase is due to deformation of the rail pad assembly as the rail rotates under higher L/V force ratios. By contrast, the worn fastener case exhibits a loss of up to 42% of initial contact area once the L/V force ratio exceeds a critical "threshold" value [4]. These data support the hypothesis that the ability of the worn fasteners to restrict rail rotation was reduced, which resulted in the observed lower contact areas under worn fasteners.…”

“…Therefore, researchers at UIUC have undertaken an effort to better understand the distribution of the rail seat load, the factors that affect it, and its effect on rail seat deterioration. Previous research has highlighted the effect of pad modulus, fastening system type, loading environment, and RSD on the rail seat load distribution [3,4,5]. Researchers at UIUC hope to incorporate the findings on RSD failure mechanisms with other FRA-funded research to generate a framework for the mechanistic design of concrete crossties and their fastening systems, in which components are designed from expected outputs and observed relationships.…”

Examination of the Effect of Concrete Crosstie Rail Seat Deterioration on Rail Seat Load Distribution

“…To obtain a control case, the results from this experimentation were compared with data gathered at TTC as part of an earlier experimentation effort (5). The control rail seats were untreated and the original rail seat geometry was intact; the rail sets were tested in tangent track on TTC's railroad test track.…”

“…Hence, UIUC researchers have undertaken an effort to better understand the distribution of the rail seat load and its effect on RSD. Previous research highlighted the effect of rail pad modulus, fastening system type, and loading environment on the rail seat load distribution (4,5).…”

Effect of Design Rail Cant on Concrete Crosstie Rail Seat Pressure Distribution

“…As a result, considerable research has been undertaken to better understand the distribution of the rail seat load, and its effect on rail seat deterioration. Previous research at UIUC has highlighted the effect of rail pad modulus, fastening system type, loading environment, and negative rail cant on the rail seat load distribution [1,4,5].…”