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

Abstract

One of the more critical 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 gage, cant deficiency, reduced clamping force of the fastening system, and an increased risk of rail rollover. Previous research conducted at the University of Illinois at Urbana–Champaign (UIUC) identified five primary failure mechanisms associated with RSD: abrasion, crushing, freeze–thaw damage, hydroabrasive erosion, and hydraulic pressure cracking. Because the magnitude and distribution of load applied to the rail seat affects four of these five failure mechanisms, effectively addressing RSD requires an understanding of the factors affecting rail seat load distribution. As part of a larger study aimed at improving concrete crossties and fastening systems, UIUC researchers are attempting to characterize the loading environment at the rail seat by using matrix-based tactile surface sensors (MBTSS). This instrumentation technology has been implemented in both laboratory and field environments and has provided valuable insight into the distribution of a single load over consecutive crossties. This paper focuses on the analysis of data gathered from MBTSS experiments designed to explore the effect of manufactured RSD on the load distribution and pressure magnitude at the rail seat. The knowledge gained from these experiments will be integrated with associated research conducted at UIUC to form the framework for a mechanistic design approach for concrete crossties and fastening systems.

Dynamic Vehicle–Track Model to Study the Effects of Track Geometry and Vehicle–Track Interaction on Concrete Tie Rail Seat Load Environment

“…While rail seat pressures were not directly measured, the agreement between in-track testing data and simulation results suggests the model could be used to estimate maximum rail seat pressures for various track conditions (Figures 7 and 8). The matrix-based tactile surface sensors technology is an applicable sensing technology that has been used for in-track measurements of component contact pressures (8)(9)(10)21). However, limitations of the technology, including cost, sensor durability, and maximum sample rate, have limited its application particularly in higher-speed, higher-frequency response situations.…”

“…Finite element analyses have also been conducted that considered specific fastening systems and fine-scale stress distributions on tie and fastening system components (6,7). Rapp et al (8) and Greve et al (9,10) have studied the application of matrix-based tactile surface sensors to measure pressure distributions at the rail seat area in-track under various load magnitudes and lateral to vertical (LV) force ratios. These studies have shown that higher LV ratios concentrate pressure on the outer half to one-third of the rail seat but have not documented pressures exceeding 7,000 psi.…”

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

“…By Equation 1, this means that more than half of the rail seat load is concentrated in the critical area of the rail seat, indicating a severely nonuniform load confirmed by the analysis detailed in this paper. Lastly, Figure 11 also includes RSLI data from joint experimentation with TTCI examining the effect of rail seat deterioration on the rail seat load distribution [5]. This data is representative of extreme RSLI that may occur in the field as a result of 0.75 inches (19.1 mm) of RSD: at 0.0 L/V, the data shows an RSLI of 2.8 and increases to 4.1 under a 0.6 L/V force ratio.…”

“…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.…”

Experimental investigation on the characteristics of the dynamic rail pad force and its stress distribution in the time and frequency domain

“…In addition to the aforementioned studies, Greve et al. 10 also examined the effect of the rail seat deterioration itself on the rail seat load distribution. In their laboratory tests, they observed a correlation between the reduced contact area and the increased wear depth of the deteriorated rail seat with a triangular wear profile, which thus resulted in a significant increase in the load pressure on the rail seat.…”