Prevention of Derailments Due to Concrete Tie Rail Seat Deterioration

Abstract

Concrete tie rail seat abrasion/deterioration (RSA) has been an issue since the inception of concrete ties. As a result of recent derailments involving abraded concrete ties on curved track, the Federal Railroad Administration set up a task force to study abrasion/deterioration mechanisms and develop automated detection methods using existing research vehicles. A portion of this study reviews historical development of concrete abrasion due to moisture or foreign materials incorporated under the rail seat that tend to abrade concrete ties evenly across the rail seat area. This report discusses a newly identified concrete tie deterioration mechanism characterized by material loss in a triangle toward the field side of the rail seat, resulting from wheel rail interaction involving track geometry variations.The NUCARS™ model was used to evaluate the vertical and lateral loading at one of the recent derailment sites using the track geometry measured approximately one month before the derailment. Wheel loads predicted from the model, based on P-42 Amtrak Locomotive, were used to evaluate the pressure distribution at the rail concrete tie interface and were compared with allowable design bearing pressure for concrete used in the manufacture of concrete ties. The results indicate that applied stress on the field side of a concrete tie due to outward rail roll can exceed the design values. Applied pressure distribution exceeding the design strength on the field side tends to abrade concrete ties in a triangular wear pattern that produces wide gage. Charts were developed to convert measured field side abrasion/deterioration to additional gage widening under an applied vertical load for identifying critical locations with wide gage defects. Further, techniques for field inspectors to detect, measure, and evaluate rail seat abrasion/deterioration (RSA) based on commonly used inspection technology are discussed.

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

“…In addition to research at UIUC, the John A. Volpe National Transportation Systems Center (hereafter referred to as "Volpe") modeled RSD to evaluate its consequences on track geometry. The work concluded that under high lateral loads, the rail could rotate, creating a pressure concentration at the field side which could exceed the crushing strength of the concrete [4].…”

“…According to a survey of North American Class I freight railroads conducted by researchers at the University of Illinois at Urbana-Champaign (UIUC), RSD was ranked as the most critical problem with concrete crossties and fastening systems [2]. RSD is defined as the loss of material from the concrete crosstie beneath the rail, and is exacerbated by the demanding loading environments in which concrete crossties are typically deployed [3,4]. RSD typically manifests as a triangular loss of material, with depth of wear increasing towards the field side of the rail seat ( Figure 1).…”

Effect of Wheel/Rail Loads on Concrete Tie Stresses and Rail Rollover

“…2 compressive strength of the concrete tie at the rail seat field side. In normal operation, compressive overloading (crushing) and repeated wheel loading produced stresses that initiated breakdown at the tie surface [2,3]. NUCARS simulations were conducted using measured track geometry taken prior to derailments to estimate the dynamic wheel loads.…”

Investigation of Material Improvements to Mitigate the Effects of the Abrasion Mechanism of Concrete Crosstie Rail Seat Deterioration

“…The feasible mechanisms are abrasion, crushing, freeze-thaw cracking, hydraulic-pressure cracking, and hydro-abrasive erosion (Joh et al 2010;Zeman et al 2009). Of these mechanisms, hydraulic-pressure cracking and hydro-abrasive erosion were investigated at UIUC and found to be feasible mechanisms resulting in RSD (Zeman 2010;Choros et al 2007;Bakharev 1994). According to another study, RSD resembled damage that is typically caused by abrasion, with hydraulic-pressure cracking and freeze-thaw cracking also being identified as possible contributors (Bakharev 1994).…”