Open Access Publications

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Open access publications by faculty, postdocs, and graduate students in the Department of Civil and Environmental Engineering.

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Rail Rollover-The State of the Art
(American Railway Engineering Association., 1977) Zarembski, Allan M.
This report presents a survey and description of work performed in the area of rail overturning. It includes analytical work, as well as test results, both field and laboratory. Comparisons between difficult tests and their results are made. The various causes and related phenomena are discussed, together with suggested techniques for dealing with this problem.
On the Prediction of the Fatigue Life of Rails
(American Railway Engineering Association, 1978-01) Zarembski, Allan M.; Abbott, Russell A.
This paper introduces a methodology for the calculation of the fatigue life of rails in service. The need for this methodology has arisen out of the trend towards increased wheel loads and the resulting fatigue-related problems. It is felt that this technique for the prediction of rail fatigue life will be of great value in both the construction and maintenance of main-line track. In this methodology, a service environment is represented by means of an environmental load spectra, which is then converted to stresses at the rail. Although this paper is restricted to flexural rail stresses, the methodology can be readily extended to other states of stress. Once the stress spectra is known, the fatigue life of the rail is calculated by means of Miner's linear cumulative damage theory, using appropriate material properties. In this analysis, the rail fatigue life at several stress levels is calculated for various rail sections. Additionally, the effect of track stiffness on the flexural fatigue life of different rail sections is determined. These results are presented as a set of curves. From these curves, the paper notes the detrimental effect of increased wheel loads on fail fatigue life. Furthermore, it is seen that a proper matching of rail size to anticipated wheel loads is necessary to reduce the occurrence of rail defects. Finally, it is seen that the sensitivity of the rail's flexural fatigue life to track stiffness is not as great as its sensitivity to wheel load, rail strength, or rail section size. The paper concludes with recommendations for additional work required to further develop and expand this technique.
Structural Dynamic Analysis & Fatigue Life Prediction of a Flat Car
(American Railway Engineering Association, 1978-03) Garg, V. K.; Prasad, B.; Zarembski, Allan M.
Dynamic characteristics of a trailer-on-flat car (TOFC) are investigated using finite-element techniques. Three different finite-element models of the flat car were developed. These models are validated in reference [1] by comparing the predicted vibration mode shapes and frequencies with test results. Further validation of the models is carried here by comparing the analytical transfer function with test results. The values of the transfer functions are computed using NASTRAN at four different locations along the center line of the flat car. Experimental values at these locations are found to be in good agreement with the computed results. Using the space beam model of the flatcar fatigue life prediction of an arbitrarily selected member of the flatcar is carried here to demonstrate the application of finite-element structural dynamics analysis to fatigue life prediction. The fatigue life values obtained using this approach are then compared with the so called ad hoc approach which uses a nominal stress value obtained from a pseudo-static analysis.
Fatigue Analysis of Rail Subject to Traffic and Temperature Loading
(Association of American Railroads, 1978-09) Zarembski, Allan M.; Abbott, R. A.
The maintenance of the track structure, and in particular, the prevention of rail failure is an area of continuing concern to the railroad industry. In view of the serious nature of rail failure, defined here to be the occurrence of rail defects, there exist, a need for the reliable prediction of rail service life in track. With the availability of this service life prediction capability, the track engineer would be in a position to anticipate rail defect occurrence and corresponding rail failure and consequently develop an inspection and maintenance cycle and schedule that would result in a safer and more efficient track structure. Recently, a fatigue analysis methodology for the prediction of rail service life was presented (1). This methodology utilizes a three dimensional characterization of the service load environment in conjunction with rail material fatigue properties to calculate an anticipated fatigue life of rail in mainline service. Reference (1) however, was restricted to rail bending stresses and utilized a hypothetical load environment. In this paper, the analysis is extended to include contact, and thermal stresses as well as bending stresses. The effect of rail head wear is also considered. The load spectrum that is utilized was developed from measurements taken on U.S. mainline track and the material properties are obtained from published laboratory test data. The fatigue life calculated by the presented method is compared with a survey of U.S. service rail fatigue failure (2). It is noted that mainline service life, in accumulated tonnage, is significantly greater for heavier rail sections than for lighter rail sections subject to similar traffic loading. This appears to support the contention that contact stress theory alone is not sufficient for the prediction of rail service life. Rather, a combination of longitudinal rail incenses due to contact loading at the wheel-rail interface, bending of rail on the track foundation, and thermal effects of temperature must be used for the proper prediction of rail defect, particularly transverse defect occurrence.
On the Nondestructive In Track Measuring the Longitudinal Force
(Association of American Railroads, 1979-02) Zarembski, Allan M.
A conventional railroad track consists of two long steel rails resting on and fastened to discretely spaced crossties, which in turn are embedded in a layer of crushed stone ballast. The ends of the rails either are connected by joint bars to form an expandable joint or are welded together to form long length of continuously welded rail (CWR). The track structure, when subjected to sufficiently high longitudinal compressive forces in the rail, can exhibit sudden and rapid lateral or vertical movement over a relatively short length. This lateral movement, or buckling of the track, results in a severe misalignment condition that may not permit the safe negotiation of train traffic (Figure 1). If buckling occurs under the train, a derailment is likely to occur. If it occurs between trains, traffic must either be stopped of slowed down until the buckled track condition is corrected. The magnitude of this problem can be seen in the fact that, during 1977, there were 109 train derailments attributed to buckling of the track. The reported damage for these derailments amounted to over $5.5 million. Furthermore, for every track buckle that resulted in a derailment, there were three to four instances of buckled track where the railroad maintenance forces were able to correct the problem before a derailment occurred. Consequently, countless hours of maintenance time are devoted to inspecting for and correcting buckled track. When the track structure is subjected to longitudinal tensile forces, pull-apart of the rail can occur. In CWR track, these , these pull-aparts, which generally occur at the welded joints, result in the appearance of a gap or separation in the rails. Such a gap, which can result in derailment or at the very least rail batter, requires the slowing down or halting of traffic until appropriate corrective action is taken. Although the detection of pull-aparts is signaled territory is facilitated by the interruption of the traffic signals, the maintenance cost of pull-aparts is appreciable. One of the greatest difficulties associated with the detection and prevention of track buckling or rail pull-apart is that it often occurs without real warning. This is because the buildup of longitudinal forces in track that is in good condition, particularly continuously welded rail track, will not be evident until it reaches the point where the track will fail. That can be too late. Yet, there is presently no practical method available for measuring the longitudinal force in the track without disturbing the track structure itself. Railroads currently rely on the subjective judgment of the maintenance-of-way man on the scene. It is the purpose of this paper to explore the various techniques used to date to measure longitudinal rail force and to lay the ground work for the continuing research effort aimed at developing a practical technique for the non-destructive in-track measurement of longitudinal force in rail.
Effect of Rail Section and Traffic on Rail Fatigue Life
(American Railway Engineering Association, 1979-03) Zarembski, Allan M.
The current trend towards increasing traffic and wheel loads has focused industry attention on maintenance of the track structure. In particular, the problem of rail failure and replacement has emerged as a key issue in the track maintenance, safety, and economics arenas. The ability to reliably predict rail service life for different traffic and track conditions is of paramount importance in examining and developing suitable maintenance procedures. Furthermore, the proper matching of rail section size with traffic and track conditions is essential for any cost effective maintenance program. Traditionally, the dominant criterion for the replacement of rail in mainline track has been either rail end batter or rail head wear. Increasing use of continuously welded rail has significantly decreased the occurrence of rail head batter. Thus rail head wear remained as the dominant rail replacement criterion. However, with the increasing traffic loads, particularly the increasing wheel loads, that the track structure is being called upon to support, the development of fatigue "defects" in the rail is emerging as a major replacement criterion for mainline tangent track. In fact, current and proposed safety criteria now emphasize the detection of fatigue defects as they develop in tangent track. Thus, it appears that in many instances, fatigue, rather than wear, is the replacement criterion for rail in service. Recent development of a fatigue analysis methodology for prediction of rail service life in mainline tangent track was reported in References (1) and (2). This methodology utilizes a characterization of the service load environment together with rail material fatigue properties to calculate the service life of the rail. Reference (2) presented the complete analysis methodology and compared the calculated results with data obtained from service experience. The correlation was quite good. The objective of this paper is to extend the results presented previously to study the effect of changing the rail section size on the rail service life. Additionally, the effect of different traffic loadings, specifically mixed freight vs. unit train traffic, and the effect of varying track support conditions will be investigated.
Railroad Freight Equipment Load Environment Testing
(Instrument Society of America, 1979-05) Zarembski, Allan M.; Darien, N. J.
Freight equipment in interchange service on the North American Continent is called upon to tolerate extremes of operating conditions throughout a service life that can span four decades. Consequently, freight car design must consider not only short-term structural requirements, but also long-term fatigue behavior. The classical design approach has been to increase structural member size to decrease stresses, thereby avoiding both short-term and long-term failure. However, with the continued increase in freight car payload, with a corresponding limit on maximum permissible gross wheel load, has come the realization that more efficient design and more detailed analysis are required. Thus the addition of fatigue analysis to the freight car design procedure gives the industry a powerful and valuable tool. Proper utilization of this tool permits more efficient design of freight cars, as well as better and more realistic "fixes" for existing cars encountering premature failure problems. Recently the Mechanical Division of the Association of American Railroads adopted a fatigue analysis methodology for the calculation of expected fatigue life for freight cars and their components (1). This technique considers the anticipated load environment that the freight car is expected to experience as well as the material and structural properties of the components under investigation. This load environment must be representative of that experienced by a freight car operating in unlimited interchange service during the period of its full service life, which can be 1,000,000 miles (1) or 40 years (2). It is the purpose of this paper to describe the procedure for acquisition and analysis of the rail service environmental load data for use as the input for freight car fatigue design.
Dynamic Rail Overturning: Modelling and Application
(1979-09) Torkamani, M. A. M.; Bhatti, M. H.; Zarembski, Allan M.
The problem of rail overturning, which constitutes one of the many causes of derailments, is of growing concern to the railroad industry. A better understanding of the rail overturning mechanism can prove to be an important step towards the development of safe and adequate railroad track systems. An analytical model for examining the dynamic behavior of rail overturning is developed in Ref. [1]. The mathematical model of the rail track system and dynamic equilibrium utilized to determine the lateral deflection and rotation of the rail subjected to time-dependent lateral and vertical forces and constant axial force. The analysis is based on linear elastic theory.
Track Gage Widening A Model Study
(American Society of Civil Engineers, 1979-11) Rassasian, M.; Zarembski, Allan M.
Occurrences of gage widening and rail overturning are of growing concern to the railroad industry. These problems occur at the interface between the rail and the tie, which is often considered to be the weakest point in conventional track structure. Consequently, a better understanding of the failure mechanisms and model of deformation associated with these problems can help the track engineer deal more effectively with these problems and improve the track structure. Recent examinations of these problems have shown that rail overturning, which is the extreme case of rail rotation and gage widening, are closely interrelated (6). In fact, gage widening can be defined as consisting of rail rotation combined with rail translation, which is the lateral displacement of the rail base relative to the ties. It can be observed that each of these two modes of deformation, rail rotation [rail roll (6)] and rail translation, can occur for the same type of loading environment. However, the relative magnitude of the deformation is dependent on the properties and conditions of the fasteners, tie plates, and ties. Consequently, the question arises as to whether, in fact, these problems are truly independent of each other, or whether they are in fact interdependent. The purpose of this paper is to present two simple models which represent the deformation mechanisms of gage widening and rail rotation. These models exhibit the essential features of the deformation mechanisms, and are amendable to exact solution. Consequently, they can be readily used to examine the general behavior characteristics of these two modes of deformation and their sensitivity to various loading combinations. Definition of Problem. -- The problem of gage widening occurs when the gage, measured 5/8 in. (0.016 m) below the top of the rail head, increases beyond the standard value for tangent track of 4 ft 8-1/2 in. (1.435 m). This deflection, at the rail head, can be due to rail translation, which is the rigid body displacement of the rail with respect to the tie, or to rail roll, which is the rotation of the rail section from the original "vertical" axis of the rail. Thus, rail translation can be considered to be the lateral deflection of the rail base with respect to the tie; rail roll can be considered to be the lateral deflection of the rail head with respect to the rail base; and gage widening can be considered to be the lateral deflection of the rail head with respect to the tie.
Future Directions in Track Evaluation and Inspection
(Association of American Railroads, 1979-11) Lovelace, W. S.; Zarembski, Allan M.
Research, development and innovation in track evaluation and inspection techniques are very important and necessary, if improvements in track performance are to be made. This area represents one that will pay dividends to the railroad industry, both now and in the future. Although strong track does not always represent a strong railroad, a weak track and structure does, in fact, represent a weak railroad, and seriously limits it's performance abilities. Improvements in the performance of track, or the strength of track, have been sporadic, and, in general, late in coming. Many of our present day "improvements" had their origin in situations in which the existing technology was simply not adequate for the requirements of the day. Example would include the advent of control-cooled rail in the 1930's, to overcome the problem of transverse fissures from hydrogen embrittlement, the development of welded rail to reduce jointed track problems, the development of thermite weld technology for the field welding of rails, the development of alloy and heat-treated rails to reduce the problem of rapid bend wear, the refinement of bonding insulated joints to extend service life and the hardening of manganese steel to provide a longer lasting insert frog structure. Very little has been accomplished in defining, quantitatively, the required strength or performance of track, and the partial vacuum in this area has been filled only by various improvements in the service lives of individual track components. To be sure, research work in the field of track structures has been undertaken, both in this country and in Europe, as, for example, Talbot's work on vertical track modulus in 1918, the French National Railway's (SNGF) work in the late 1940's on their detailer wagon [2], and the U.S. Track Train Dynamics effort that began in 1972, which consolidated and expanded recent track-related research. In the United States. it has only been in the last ten years that railroads began to take a serious look at measuring the geometric deficiencies in their track by automated means (Figure 1). Even today, less than twelve Class 1 railroads own and operate their own track geometry cars. These cars measure the track irregularities, such as deviations in line, surface, gage and elevation, but not the strength of the track itself. These track geometry cars have probably been worth over one thousand times their initial cost to the railroads because they have been extremely successful in finding track locations that are unsafe, and in need of repairs. To a lesser degree, they have been successful in the statistical evaluation of geometrical data to compare the relative qualities of long segments of track [3]. No definition or measurement of track strength, however, has been undertaken. In this paper, the authors would like to discuss present work and future trends in techniques for the evaluation of track performance and strength.
Freight Car Fatigue Analysis: Guidelines and Application
(Association of American Railroads, 1979-11) Halcomb, S.; Zarembski, Allan M.
In recent years, the increase in occurrences of fatigue-induced failures in freight car structures has led to a need for the development of suitable fatigue analysis and prediction tools. In order to fill that need, the Track Train Dynamics Program initiated a project to develop a set of industry guidelines for fatigue analysis of freight car body components. This analysis was intended to complement the existing freight car design specifications, and fill an existing gap in the car design process. The outgrowth of this project was the development of Interim Guidelines for Fatigue Analysis of Freight Cars, which have recently been adopted by the Mechanical Division of the Association of American Railroads (AAR) as an Industry Specification (M-1003). These guidelines introduce a fatigue analysis methodology which can be incorporated into the freight car design procedure. Thus, these guidelines represent an analytical tool, with which the freight car design engineer can determine the fatigue life of critical freight car components that are subjected to the fluctuating stresses experienced in railroad service. It is the purpose of this paper to briefly introduce the methodology presented in the fatigue life analysis guidelines, and to discuss their validation, implementation and limitations.
On the Measurement and Calculation of Vertical Track Modulus
(American Railway Engineering Association, 1979-11) Zarembski, Allan M.; Choros, John
This paper presents the results of a series of tests and analyses directed towards the characterization of the track structure under vertical loads. It also presents and evaluates different analytical techniques for the calculation of the vertical track modulus. In a series of tests at the Association of American Railroads' Track Structures Dynamic Test Facility, the response of the track was obtained by monitoring track deflection under increasing vertical loads. This load and deflection data was then used to calculate vertical track modulus, track stiffness and track compliance. Three widely used techniques were utilized to calculate the vertical modulus. The results of the tests indicate that the modulus of the track is related to the level of loading; thus identical track can give different modulus values for different load levels. Of the three different techniques used to calculate track modulus, the beam-on-elastic-foundation technique was found to be the most applicable to field measurements since it requires a minimum number of track deflection values.
Rail Research: Meeting the Challenge of Modern Traffic Loading
(Transportation Research Board, 1980-01) Zarembski, Allan M.
In light of the current trend in railroading toward heavier cars and trains, the railroad track structure is being called on to perform under an increasingly sever loading environment. As a result, the very nature of rail failure has changed. This change in the modes of rail failure has resulted in changes in criteria for fail replacement and consequently in changes in inspection and maintenance practices. Track rail once lasted until it literally wore out. Under today's severe loads, however, fatigue-initiated cracks in the railhead can result in premature fracture of the rail. Furthermore, it is often not possible to see the fatigue crack, even at its critical point. Ultrasonic or magnetic inspection techniques must be used to detect these hidden defects so that they can be removed. Rail-end batter, the traditional replacement criterion for tangent track, has been significantly reduced by the increasing use of continuously welded rail. In its place, however, fatigue-induced defects, either in the rail or at a weld, have emerged as the dominant rail-replacement criterion for tangent track. On curves, severe gage face wear, plastic flow of the railhead, and even crushed rail are all major problems that combine with initiation of fatigue defects to shorten the service life of rail. To better understand the problem, one must only consider that a stationarly 91-Mg (100-ton) car with a static wheel load of 146 kN [33000 Ibf (33 kips)] transmits a contact stress of 1200 MPa (175000 lbf/in^2) to the head of the rail. The yield strength of the rail steel is only 520 MP (75000 lbf/in^2)/ The result can be seen in Figure 1: rail wear, fatigue defects, or both. Thus, in recent years, rail research has been directed toward the problem of defining, quantifying, and ultimately extending rail service life. It is the purpose of this paper to briefly define and quantify some of these modes of rail failure and to discuss the current and future directions of rail research in North America.
Laboratory Investigation of Track Gauge Widening
(American Railway Engineering Association, 1980-01) Zarembski, Allan M.; Choros, J.
This paper presents the results of a series of track gauge widening tests conducted at the Association of American Railroad's Track Structures Dynamic Test Facility. The tests investigated the gauge widening behavior of conventional track structure under various combinations of vertical, lateral and longitudinal loads. The effect of single axle vs dual-axle loading and static vs dynamic lateral loading were also examined. The tests indicated that under loading representative of that imposed by traffic, significant widening of the track gauge can occur. It was further observed that the level of damage to the tie-fastener interface can be measured and evaluated by means of gauge widening type testing and that the potential exists for conducting "nondestructive" gauge widening tests in service track.
Field Evaluation of Mainline Quality Track Using a Track Strength Test Vehicle
(American Railway Engineering Association, 1980-11) Zarembski, Allan M.; Choros, John
This report presents the results of field evaluation test of the prototype Track Strength Test Vehicle, the DECAROTOR, on mainline quality track. This work is part of the ongoing Track Strength Characterization Program, directed at measurements of the load-carrying capacity of railway track structures, the development of suitable measurement techniques, the demonstrations of the usefulness of such measurements, and ultimately the matching of the track strength with the vehicle loading. The tests reported here are the second in a series of field tests aimed at evaluating the capabilities and limitations of the Track Strength Testing concept. The objectives of these tests were to: (a)investigate the ability of the Decarotor to evaluate mainline quality track and to detect weaknesses in the track, (b)determine if the track strength testing concept could detect differences in mainline track "strength," normally permitted by railroads, and (c)evaluate the ability of stationary load-deflection tests to determine tie or fastener conditions. In order to achieve these objectives, a series of moving and stationary lateral track strength tests were conducted in March 1980 on the Southern Railway's mainline near Charlottesville, VA. The test section included two adjacent test zones. One zone was timbered and surfaced in late 1979 and was considered to represent "strong" standard mainline track. The second zone was last timbered in 1974, and was at the end of its six years maintenance cycle. It represented the "weakest" standard mainline track permitted by the railroad. The results of the tests showed that continuous track strength measurements were feasible. These measurements consistently and repeatedly identified weaknesses in the track, such as clusters of poor ties. In addition, these measurements were able to differentiate between the different levels of lateral track strength found in both mainline and yard quality track. These testing activities could be performed nondestructively by means of a moving inspection vehicle, so as to permit the evaluation of relatively long stretches of track. Finally, it was shown that stationary load-deflection tests can help identify the general condition of tie or fasteners. Further testing, however, is necessary in order to demonstrate the practical value of this testing technique.
The Response Equations for a Cross-Tie Track
(ACTA Mechanica, 1981) Zarembski, Allan M.; Kerr, A. D.
The Response Equations for a Cross-Tie Track. Early analyses of the lateral response of cross-tie railroad tracks are based on the assumption that the rail-tie structure responds like a beam in bending. Because of the difficulties encountered in determining the lateral bending stiffness of a cross-tie track, a more recent approach is to model the rail-tie structure as a beam in bending that is also subjected to continuous resistance moments, transmitted to the rails by the fasteners. Also this approach exhibits a number of shortcomings. To date there are no generally accepted equations for the lateral response of the cross-tie track. The main purpose of the present paper is to derive such equations. Since the rail-tie structure consists of a repeated pattern of identical units, the corresponding difference equations are derived first. Then, by a limiting process, in which the tie spaces tend to zero. The difference equations are reduced to differential equations. This approach yields equations with well-defined coefficients, in terms of the geometrical and mechanical parameters of the track structure. Difference and differential equations are derived for the track response in the lateral, as well as the vertical plane. The derived equations are then discussed and compared with those suggested by other investigators.
An Investigation of Railroad Maintenance Practices to Prevent Track Buckling
(American Railway Engineering Association, 1981-03) Magee, G. M.; Zarembski, Allan M.
The use of continuous welded rail (CWR) increases the likelihood of track failure through buckling (sun-kink***) or pull-apart. Over 100 derailments occur each year, which are attributed to buckled track, with many more instances of buckled track being detected and corrected before an accident occurs. Although most railroads have formal established procedures for the laying and maintenance of CWR, significant variations exist among these practices. This report compares the practices of ten major North American railroads and the recommended practice of the American Railway Engineering Association. In addition, two surveys of railroad track buckling incidents were conducted. The first was a series of internally reported, track buckling occurrences on a major U. S; Class One Railroad. A total of 479 buckling events were examined. The second was a study of derailments, attributed to track buckling, that occurred on seven North American railroads. A total of 65 cases were examined. The survey information was then compared with the various railroad practices, as well as with current theory. Based on these comparisons, it was noted that railroads are starting to take into account differences in climatic conditions in defining rail laying temperature requirements. A critical temperature increase zone of 35 to 55 degrees Fahrenheit above the laying temperature was observed. The effect of curvature, particular heavy curvature of between five and ten degrees, was seen to be a significant factor in increasing the likelihood of track buckling. A wide variation in railroad practices, both in rail laying policies on curves and ballast shoulder widths on curves, was noted. Finally, the significance of ballast condition and the effect of maintenance operations was observed, together with the differences in maintenance practices among the railroads. Although no specific recommendations are made, general and specific observations about the surveyed track buckling failures are made and compared to current railroad practices and theory.
Determination of Track Gage Widening Parameters
(American Railway Engineering Association, 1981-05) Zarembski, Allan M.; Bhateja, Rajiv
Gage widening is a serious railroad track problem related to the condition of the ties and fasteners. Recently, an improved analytical model for track gage widening was developed. This model predicts the response of the rail to applied external loading and the results agree well with laboratory and field test data. This paper summarizes this improved analytical model and presents a numerical computation technique for the determination of the fastener stiffness parameters. This technique, which utilizes static load-deflection test data, permits a closer correlation between the test and analytical results. A set of fastener stiffness parameters for conventional U.S. track is also presented.
Effect of Increasing Axle Loads on Rail Fatigue Life
(American Railway Engineering Association, 1982) Zarembski, Allan M.
This report presents the results of an investigation into the effects of increasing axle loads on the fatigue life of tangent, continuous welded rail (CWR). Two independent studies were conducted. The first utilized a statistical analysis technique, which obtained probability distribution curves for rail defect data. The second utilized a fatigue analysis methodology for the prediction of rail service life. Both techniques have shown good correlation between calculated results and service experience. For the first study, rail defect data was obtained from two mining railroads: one operating 100-ton car unit trains; the other 70-ton car unit trains. These were then compared with data from both a "typical" mixed freight traffic railroad and from FAST (l00-ton cars). For the second study, a rail fatigue life model was used to calculate the rail life under loadings that were representative of the same three types of operations. The results of both analyses show that increasing the axle loadings results in increased rail defect occurrences, with a corresponding decrease in rail fatigue life for tangent CWR. This reduction is by about 40% of the life of the rail, in million gross tons (MGT), when the loading is increased from 70-ton car (200,000 lb.)** to 100-ton car (236:000 lb.) loading conditions. This effect, which is seen for both heavy (132 lb.) and medium (119 lb.) rail sections is quite significant, and must be taken into account in any future studies and economic analysis.
Development of an Improved Vehicular Loading Characterization Associated with the Gage Strength of Track
(American Railway Engineering Association, 1982-01) Manos, W. P.; Scott, J. F.; Choros, J.; Zarembski, Allan M.
This report describes the development and application of a simplified technique for presenting vehicular loading information in a consistent and uniform manner. The load data, both lateral (L) and vertical (V), is used to develop a "loading severity", value (5), with which the level of loading can be equated with the associated level of damage to the track, as defined by a given rail head deflection. Specifically, it addresses the gage retaining strength of the track structure, in general, and the tie-fastener-rail system, in particular. This is done by means of a linear relationship S=L–μV where μ is the effective friction coefficient between the rail and the tie. Data were taken from five sets of fie1d and laboratory tests of track gage widening, used to validate this relationship and to determine the effective friction coefficient for conventional track. The linear relationship between lateral (L) and vertical (V) loads indicates that the equation shown above is a good approximation to the equivalent levels of loading. Examination of the test data and analysis of the effective friction for the numerous individual tests in the five series shows a normal effective friction distribution, with a mean value of 0.4 and a standard deviation of 0.1.

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