Finite element analyses (FEA) were conducted in this paper to understand the underlying mechanisms contributing to a commonly observed failure mode of cut spikes used with the elastic fastening systems for wood ties. This failure mode features fatigue cracking development in the internal cross-sectional spike surfaces located approximately 1.5 inches below the top surface of a tie. Previous computational studies applied elastic material properties with “perfect” material behaviors. The study presented in this paper adopted post-elastic failure models for both the steel spike and wood tie materials, which proved key to reconstructing the observed failure mode in modeling. The commercial FE software Abaqus was employed in this study. Continuum FE models were developed for a single cut spike embedded in a wood tie. The steel spike was modeled to yield plastically upon reaching a yield strength limit. A user material subroutine documented by Abaqus was adopted to simulate the 3D orthotropic failure of the wood tie. Both the elastic properties and strength limits of the wood material were orthotropic, with the properties in the transverse direction significantly lower than those in the fiber direction. Different combinations of vertical, lateral and longitudinal forces were applied in the analyses, deforming the spike in various bending modes. The forces were increased in magnitude until the steel reached its yield strength (i.e., developed permanent plastic deformations), and the yielding locations were recorded and compared with the observed failure mode. The FEA showed that damage initiated in the wood tie being pressed by the spike with sufficiently large forces and that wood damage preceded steel yielding. The farther the wood material deteriorated from the top down, the lower the steel yielding location was in the spike shaft. Longitudinal forces were reacted to in the weaker transverse direction of the wood tie and therefore resulted in lower damage initiation forces and lower steel yielding locations than lateral forces did. It was concluded that the orthotropic wood tie failure condition and a substantial presence of the longitudinal force were necessary conditions for the spike to initiate failure at about 1.5 inches below the top surface of a tie. This corroborated the findings in a derailment investigation involving the spike failure. The lateral force alone unlikely caused this failure mode, but the presence of a lateral force on the spike appeared to decrease the magnitude of the longitudinal force needed to initiate damage in the spike.

The reliability of finite element (FE) based deterministic structural analysis of railroad trackbed has improved significantly due to ever increasing computational powers. However, the application of probabilistic methods to incorporate the material and geometric variabilities in these FE analyses is still profoundly underworked. In this study, the influence of variability in granular layers’ modulus and thicknesses values on the railroad subgrade performance have been investigated by applying probabilistic method and using a 3-dimensional FE based numerical trackbed model previously developed and validated by the authors’ research group. The influence of these factors is accounted for by changing their coefficients of variance (COV) while keeping their means constant. Preliminary results revealed that the variation in subgrade modulus is the most influential factor for subgrade performance, both in terms of progressive shear failure and excessive plastic deformations, followed by ballast modulus. Variations in depths, for the range studied, remained passive to the subgrade performance. The findings of this work is of particular significance in evaluating the subgrade performance while including the material and geometric variations, which may be caused by construction imperfections, weather changes, and/or rail operations.

Laboratory tests are commonly used to investigate the performance and behavior of ballast in various conditions. In large part, these investigations use freshly quarried rock prepared to meet gradation requirements of AREMA or similar organizations as the ballast material. When worn ballast is desired, some studies run the fresh ballast through an apparatus, such as the one used in LA Abrasion, to create an artificially worn ballast. Past investigations of the effects of angularity on the strength properties of granular materials provide mixed results. There is a clear need for further understanding of the behavior of abraded ballast. In this investigation, a naturally abraded ballast, sourced from an active rail, is used in laboratory testing to assess its mechanical properties and behavior. Based on gradation testing, this material was most likely an AREMA #4 graded material when it was first placed into the track bed. However, particle breakage that occurred during the time that it was used in track led to a broader gradation that included smaller ballast pieces. Triaxial testing was performed to determine the strength properties, stress-strain behavior, and volumetric strain behavior of clean ballast in varying moisture conditions. Box testing was used to investigate the settlement of the ballast under dynamic loading. The ballast in the box test was prepared to the same density as the triaxial tests so that the results are analogous. The results of the triaxial tests exhibited typical behavior, with the samples undergoing initial contraction followed by dilation. However, the results showed that the deformations were larger than might be expected from a similar angular ballast. Additionally, strengths do not appear to be significantly reduced compared to angular ballast. The box tests also showed typical results, though less total settlement occurred than might be expected. The unexpected results from these tests could be explained by the broader gradation of the abraded ballast. It has been shown that a wider range of particle sizes in a granular material increases the strength. It is likely that this holds true for this particular ballast, despite the increased level of abrasion. However, the more rounded particles are still less likely to interlock, resulting in the high deformations exhibited in the triaxial tests. The introduction of water to the tests does not have hugely negative effects on the strength, likely because the lack of fouling prevents large amounts of water from being held by the ballast. Abraded ballast appears to achieve the desired strengths needed for support railroad loads, however the increased deformability of the material makes it less than ideal for use in track.

This work intends to lay the groundwork for Computer Aided Engineering (CAE)-based occupant safety of a typical tier-III Indian Railway (IR) passenger coach in a collision accident. Our previous work presented in International Crashworthiness Conference 2010 under the title “Simulation of Crash Behaviour of a Common Indian Railway Passenger Coach” provided crashworthiness assessment of a typical tier-III passenger coach structure for representative head-on collision scenarios namely, against an identical passenger coach and against a stationary locomotive. These scenarios were envisioned to be part of a bigger accident scenario e.g - head-on collision between two trains moving towards each other. Analysis of involved chain of events for entire rolling stock and resulting internal collisions between individual passenger cars was out of scope of this work and necessary inputs were obtained from available literature on the same. This work used a full scale Finite Element (FE) simulation model and commercial explicit solver LS-Dyna. FE model was validated using International Railway Union (UIC) code OR566 specified proof loads for design. Simulation methodology used for dynamic impact was validated by component level crushing experiments using a drop tower facility. Material modelling incorporated strain rate effect on yield strength which is essential for obtaining accurate structural deformations under dynamic impact loading. Contacts were modelled using the penalty method option provided by the solver. This model was simulated for collisions at 30, 40 and 56 km/h against a stationary rigid barrier. Collision speeds were chosen to simulate impact energies involved in collision scenarios as mentioned above. The structure was found to exhibit global bending deformation and jackknifing with pivot position at the door section. In this paper, we present an extension of this work — coupled occupant safety simulation and injury assessment. It was accomplished by recording head, neck, chest and knee responses of a Hybrid-III 50 th percentile male Anthropomorphic Test Device (ATD) FE model, seated in passenger position on lower berth of the first cabin of a passenger car. Interiors were modelled to represent the actual structure. Dummy model was adapted to passenger cabin’s excessive mobility conditions and responses were revalidated against Federal Motor Vehicle Safety Standards (FMVSS) limits. Injury interpretation was based on Abbreviated Injury Scale (AIS), automotive injury criteria and injury risk curves for Head Injury Criterion (HIC), thoracic spine acceleration, neck bending moment in flexion and extension and knee force. This study provides with estimates of injury and fatality based on computer simulation of accident scenarios. However, attempts of correlating to any available injury and fatality statistics were out of scope of this study.

The ballast layer in a railroad track helps distribute loads from the superstructure to the formation; a well-designed ballast layer is also meant to prevent excessive vertical, lateral and longitudinal movement of the track under loading. When subjected to repeated loading, the granular ballast particles often undergo breakage leading to significant changes in the shear strength as well as drainage characteristics of the ballast layer. Excessive ballast degradation leads to increased vertical settlements, and is often associated with speed restrictions and increased passenger discomfort. Several researchers in the past have studied the phenomenon of ballast breakage in a laboratory setting. However, due to complexities associated with these large-scale laboratory tests, detailed parametric studies are often not feasible. In such cases, numerical modeling tools such as the Discrete Element Method (DEM) become particularly useful. This paper presents findings from an ongoing research effort at Boise State University aimed at studying the phenomenon of ballast breakage under repeated loading using a commercially available Discrete Element Package (PFC3D ® ). Ballast particles were simulated as clusters of balls bonded together, and were allowed to undergo breakage when either the maximum tensile stress or the maximum shear stress exceeded the corresponding bond strength value. Different factors studied during the parametric analysis were: (1) load amplitude; (2) loading frequency; (3) number of cycles of loading; (4) bond strength; and (5) particle size distribution. The objective was to identify the relative importance of different factors that govern the permanent deformation behavior of railroad tracks under loading.

This paper examines alternative, improved materials for truck castings. The first part looks at steels that would not require post-weld heat treatment after repair welding. The second part investigates specific applications for temperatures below −50 °F. The rapid, dramatic temperature changes that occur during welding can form brittle phases or cracking in some steels. The weld has three areas of differing structure: the weld, the heat affected zone (HAZ), and the parent metal. The maximum hardness occurs in the HAZ and is the limiting factor in determining weldability. An ultraweldable steel is a steel that does not require post-weld heat treatment. Many steels were evaluated for their chemical composition and susceptibility to cracking; those that were likely to form brittle phases were eliminated from consideration. Four low alloy steels and one carbon steel were selected as being potentially ultraweldable. To evaluate the ultraweldability of these steels, groove welds and two types of spot welds were made on the five candidate alloys. The welds were then sectioned and prepared for microstructural and microhardness evaluation. Microhardness readings were taken across the weld, spanning the weld, HAZ, and base material. Three of the steels formed hard, brittle phases during most of the tests. This indicates these materials are not ultraweldable. Two of the low alloy steels did meet the requirements for ultraweldability. Future work in this area would include producing truck castings from these materials. At low temperatures, plain carbon steels, such as the types used in truck castings, can fracture in a brittle manner, with no visible deformation. The material property of deforming without fracture is toughness or ductility. Using materials that retain their toughness in low temperatures could prevent brittle failures of truck castings. Six grades of steel currently used in low temperature applications were selected for this research. Specimens from each of the six materials were evaluated for tensile properties at multiple temperatures. Charpy impact specimens were tested at temperatures ranging from −20 °F to −120 °F. The measured room temperature tensile properties of each of the six steels met or exceeded the requirements for Grade B+, the steel currently used for truck castings. Four of the steels showed impact energies far above that of the current Grade B+, but two of them gave consistently higher impact energies than all others. These would be the best candidates for future work in this area. Future work would involve producing full size truck castings from one or more of these alloys, then testing them for fatigue performance, preferably at low temperatures.

Rail switches are critical infrastructure components of a railroad network, that must maintain high-levels of reliable operation. Given the vast number and variety of switches that can exist across a rail network, there is an immediate need for robust automated methods of detecting switch degradations and failures without expensive add-on equipment. In this work, we explore two recent machine learning frameworks for classifying various switch degradation indicators: (1) a featureless recurrent neural network called a Long Short-Term Memory (LSTM) architecture, and (2), the Deep Wavelet Scattering Transform (DWST), which produces features that are locally time invariant and stable to time-warping deformations. We describe both methods as they apply to rail switch monitoring and demonstrate their feasibility on a dataset captured under the service conditions by Alstom Corporation. For multiple categories of degradation types, the baseline models consistently achieve near-perfect accuracies and are competitive with the manual analysis conducted by human switch-maintenance experts.

The Federal Railroad Administration’s Office of Research and Development is conducting research into passenger locomotive fuel tank crashworthiness. A series of impact tests is being conducted to measure fuel tank deformation under two types of dynamic loading conditions — blunt and raking impacts. The results of this research program assist in development of appropriate standards for puncture resistance requirements to be applied to alternatively-designed fuel tanks, such as on diesel multiple unit (DMU) passenger rail equipment. This paper describes the results of the first blunt impact test performed on a DMU fuel tank. On June 28, 2016, FRA performed a dynamic impact test of a fuel tank from a DMU rail vehicle. The test was performed at the Transportation Technology Center (TTC) in Pueblo, Colorado. An impact vehicle weighing approximately 14,000 pounds and equipped with a 12-inch by 12-inch impactor head struck the bottom surface of a DMU fuel tank mounted vertically on an impact wall. The impact occurred on the bottom of the fuel tank at a location centered on two baffles within the fuel tank. The target impact speed was 11.5 mph, and the measured impact speed 11.1 mph. The test resulted in a maximum indentation of approximately 8 inches, the bottom of the tank bending away from the wall, and buckling of several internal baffles. Following the test, the tank was cut open to inspect the damage to the internal structure. This revealed that the buckling behavior of the baffles was isolated to the baffles immediately adjacent the impact location, each one buckling as the tank deformed inward. Prior to the test, finite element analysis (FEA) was used to predict the behavior of the tank during the test. The FE model of the tank required material properties to be defined in order to capture plastic deformation. The combination of metal plasticity, ductile failure, and element removal would permit the model to simulate puncture for this tank at sufficiently-high impact speeds. The pre-test FE model results compared very favorably with the test measurements, and both the pre-test model and the test resulted in similar modes of deformation to the DMU fuel tank. Following the test, material coupons were cut from undamaged areas of the fuel tank and subjected to tensile testing. The post-test FE model was updated with the material behaviors from the post-test material testing. This test is part of a research program investigating puncture resistance of passenger locomotive fuel tanks. The objective of this research program is to establish the baseline puncture resistance of current locomotive fuel tanks under dynamic impact conditions and to develop performance requirements for an appropriate level of puncture resistance in alternative fuel tank designs, such as DMU fuel tanks. Future tests are planned within this research program. The lessons learned during the series of tests support finite element (FE) modeling of impact conditions beyond what was tested. Additional tests investigating the puncture resistance of fuel tanks during sideswipe or raking collisions are also planned.

This paper presents the result of an evaluation program for the condition of the SEPTA Broad Street subway car shells and their capability to perform during an extended period of revenue service. SEPTA currently is evaluating various system upgrades to address equipment obsolescence and reliability, and wanted to verify that the current car shells are expected to be serviceable during this extended period. The evaluation focused on two aspects of the 1982-built car shells. First, what is the current and predicted condition of the shells and, second, how does the performance of the current car shell design compare to present day designs and requirements? Four sets of activities were done as part of this project. One-third of the fleet was randomly chosen for visual inspections. Service-induced cracks were identified at two locations: in ring welds below the doors, and on the side sill between the corner posts and the anti-climbers. The ring weld cracks have been identified on a small number of cars in the past, and SEPTA continues to monitor and reinforce these areas. The cracks between the corner posts and anticlimbers are also being monitored; to date, none of these cracks has progressed to the point that repair is required. In parallel with the visual inspections, the car shell camber and doorway dimensions were measured on approximately 10% of the fleet. All the measured vehicles had positive camber; doorway dimensions were uniform, except for scattered individual measurements that were car-specific. This part of the evaluation concluded that the car shells are not undergoing significant degradation or cracking. One car was instrumented with strain gauges in potential high-stress areas, and then operated at simulated full passenger-load weight over the Broad Street route. Cyclic strains imposed by simulated revenue service were measured and converted to stresses. This testing confirmed high stresses at the joint between the side sill and the body bolster. The lifetime limiting location on the car shells is in the ring welds below the doors, consistent with the results of the visual inspections. Using conservative assumptions of continuous full passenger loading and minimum material properties, the predicted lifetime to the initiation of visible cracks in this area is 7–14 years of service. This independent evaluation is consistent with the actual experience, and provided confidence in the analysis protocol. SEPTA is monitoring this location and repairing cracks as required. Evaluation of the car shell design with regard to performance in a collision revealed that, unlike most other cars of its era, the Broad Street car shell contains provisions to manage energy absorption during a low-speed collision. Records obtained from a car repair shop showed that, when a Broad Street car had a significant non-revenue end collision, these provisions worked as intended to localize the deformation. In similar collisions, the Broad Street car shell will not perform significantly different from cars built to current industry practices. Results from this study indicate that with continued attention to car shell condition, including regular inspections and limited repairs, the Broad Street car shells will continue to be safe and serviceable for an extended period.

One of the key issues facing rail maintenance crews today is the successful identification and removal of rail corrugations (a sinusoidal, longitudinal rail surface deformation). Typically, rail corrugations are identified through visual inspection (which look for regular surface patterns) or audio methods (which listen for high frequency noise). Once identified, removal is accomplished through rail grinding and consists of running standard “peak-and-plow” grind pattern(s), whereby the corners of the rail are angled upwards to peak the rail, then the top of the rail is ground down (plowed) by placing numerous stones around the top of the rail. “Peak-and-plow” corrugation removal can require multiple passes depending upon the depth of the measured corrugation as well as the type of grinder (available horsepower) and the number of stones present on the grinder being utilized. The above methodology is typically applied whenever corrugation removal is required and since the grind patterns are static, significant extraneous metal removal can occur both during corrugation removal and during rail profiling. An integrated system has been developed to identify and aid in the removal of rail corrugations. To assist in the detection and understanding of the severity of corrugations in the rail, a bogie frame mounted, accelerometer based measurement system was developed. The measured accelerations are filtered and transformed into displacement measurements which can be further processed to understand the primary wavelength and amplitude of the corrugations. These values can then be fed into specialized grinder control software which makes decisions on how to proceed with grinding; be it to remove corrugations then establish profile, only reestablish profile, or do nothing. Note that grinding may still be required to repair the rail surface due to other deformation such as rolling contact fatigue, shelling, spalling, etc. If corrugation removal grinding is required, the specialized software will create (in real-time) dynamic “peak-and-plow” grind patterns utilizing calibrated metal removal equations which estimate the amount of material one grinding stone can remove, based on the instantaneous radius of the rail, grinding motor horsepower, grinder speed, etc. The site specific, dynamic corrugation removal pattern contains calculated motor powers and orientations (angles) which will remove metal from the rails in such a way to both minimize metal removal required to eliminate the corrugations and minimize metal removal when establishing the desired post-grind rail profile. This paper explores recent developments in the identification and subsequent managed removal of rail corrugations with an end goal of the reestablishment of rail profile with minimal metal removal and maximum preservation of rail life. The principal behind the corrugation identification system is described with supporting experimental evidence. Also presented in this paper are the basis behind dynamic corrugation removal, modeling results of applying a dynamic “peak-and-plow” pattern, and a comparative study describing the simulated post-grind outcomes of applying dynamic corrugation removal versus applying traditional methods.

The main purpose of this ongoing study is to investigate the effect of heat generation within a railroad thermoplastic elastomer suspension element on the thermal behavior of the railroad bearing assembly. Specifically, the purpose of this project is to quantify the heat generated by cyclic loading of the elastomer suspension element as a function of load amplitude, loading frequency, and operating temperature. The contribution of the elastomer pad to the system energy balance is modeled using data from dynamic mechanical analysis (DMA) of the specific materials in use for that part. DMA is a technique that is commonly used to characterize material properties as a function of temperature, time, frequency, stress, atmosphere or a combination of these parameters. DMA tests were run on samples of pad material prepared by three different processes: injection molded coupons, transfer molded coupons, and parts machined from an actual pad. The results provided a full characterization of the elastic deformation (Energy Storage) and viscous dissipation (Energy Dissipation) behavior of the material as a function of loading frequency, and temperature. These results show that the commonly used thermoplastic elastomer does generate heat under cyclic loading, though the frequency which produces peak heat output is outside the range of common loading frequency in rail service. These results can be combined with a stress analysis and service load measurements to estimate internally generated heat and, thus, enable a refined model for the evolution of bearing temperature during operation.

Trackbeds are typically composed of all granular materials comprised of ballast and subballast over compacted subgrade. Most poor performances of railroads can be attributed to poor and unstable subgrade conditions. Below the surface, the instability of the subgrade material can propagate through the granular zone leading to excessive settlements and deformations of the railway. Conventional subgrade restoration in the trackbed system requires the removal of the granular materials and over-excavation of soft unstable subgrade materials, moisture adjustment, re-compaction, and sometimes chemical stabilization of the subgrade soils. Since these procedures are considered very expensive in terms of construction equipment, railway outage time, and labor force, alternative solutions for consideration and evaluation are essential. Injection of expansive foam (polymer based) materials is a relatively recent method that has been used in various applications of soil stabilization in the roadway industry. This technique relies on the injection of rigid-polyurethane foam, which is a high-density, expanding, thermoset, hydro-insensitive and environmentally neutral polyurethane-resin product, into the soft and unstable soil to improve their shear strength and stability index. In addition, the stabilized zone acts as a waterproof membrane protecting moisture sensitive subgrade, and acting as a separation layer to eliminate pumping and contamination of the granular subballast at saturated fine grained conditions. The objective of this paper is to evaluate the practicability of polyurethane stabilized soft and unstable subgrade under unbounded granular trackbeds to mitigate future deformation, restore railway foundation, and reduce trackbed repair cost and outage time.

Railway transitions like bridge approaches experience differential movements related to differences in track system stiffness, track damping characteristics, foundation type, ballast settlement from fouling and/or degradation, as well as fill and subgrade settlement. A recent research study at the University of Illinois has used advanced geotechnical instrumentation to identify and quantify different factors contributing to recurrent differential movement problems at three different bridge approaches along Amtrak’s Northeast Corridor (NEC) near Chester, Pennsylvania. Field instrumentation data have indicated excessive ballast movement to be the primary factor contributing to the “bump” development at these bridge approaches. Among the different remedial measures applied to mitigate the recurrent track geometry issues were: (1) Chemical Grouting, (2) Stone Blowing, and (3) Under-Tie Pads. This paper will discuss the implementation methods using track geometry records and instrumentation data, and highlight the effectiveness of chemical grouting and stone blowing to mitigate the differential movement problem at railroad bridge approaches. According to the trends in the transient ballast deformation data collected under train loading, both remedial measures were effective in significantly reducing excessive ballast deformation, which was the primary mechanism behind the bump development at these locations. Ballast degradation and presence of excessive fine particles in the ballast layer adversely affected the ability of the grout to bond with aggregate particles. A “clean” ballast layer, on the other hand, facilitated adequate bonding between the grout and ballast particles leading to significantly improved long-term track performance.

Indented wires have been increasingly employed by concrete crosstie manufacturers to improve the bond between prestressing steel reinforcements and concrete, as bond can affect several critical performance measures, including transfer length, splitting propensity and flexural moment capacity of concrete ties. While extensive experimental testing has been conducted at Kansas State University (KSU) to obtain bond characteristics of about a dozen commonly used prestressing wires, this paper develops macro-scale or phenomenological finite element bond models for three typical wires with spiral or chevron indent patterns. The steel wire-concrete interface is homogenized and represented with a thin layer of cohesive elements sandwiched between steel and concrete elements. The cohesive elements are assigned traction-displacement constitutive or bond relations that are defined in terms of normal and shear stresses versus interfacial dilatation and slip within the elasto-plastic framework. A yield function expressed in quadratic form of shear stress and linear form of normal stress is adopted. The yield function takes into account the adhesive mechanism and hardens in the post-adhesive stage. The plastic flow rule is defined such that the plastic dilatation evolves with the plastic slip. The mathematical forms of the yield and plastic flow functions are the same for all three wire types, but the bond parameters are specific for each wire. The adhesive, hardening and dilatational bond parameters are determined for each wire type based on untensioned pullout tests and pretensioned prism tests conducted at KSU. Simulation results using these bond models are further verified with surface strain data measured on actual concrete crossties made with the three respective prestressing wires at a tie manufacturing plant.

The water content of fouled ballast is important when considering the shear strength and deformability of the ballast, and therefore critical in evaluating whether the track is at risk of excessive deformations warranting a speed restriction order. Fouled ballast from northeastern United States was tested in the laboratory to assess changes in shear strength and deformability as a function of water content. X-ray fluorescence analysis determined that the fouling material was 95% by weight basalt in origin. No more than 5% of the fouling material could be attributed to the abraded concrete ties. The field capacity of the fouled ballast was measured to be at a water content of 10%. Freezing and thawing tests indicated that approximately 4% of mass loss could be expected as a result of 25 freeze/thaw cycles. 6-inch triaxial tests, TX-CIDC, were conducted on the ballast at water contents between dry and field capacity (10%). As the ballast was partially saturated, volume change was measured using circumferential string potentiometers. The water content had an influence on the shear strength and the modulus of elasticity of the fouled ballast. The Mohr-Coulomb friction angle decreased from 47.3° for the dry ballast to 42.5° for the field capacity ballast. The Mohr-Coulomb cohesion decreased from 3.38 psi to nearly zero with initial addition of water, but increased to 6.18 psi as the water content reached field capacity. This is likely attributable to changes in capillary tension of the partially saturated fouling material. The average shear strength, Mohr-Coulomb friction angle, Mohr-Coulomb cohesion, modulus of elasticity and Poisson’s Ratio all showed weakening and strengthening effect by addition of water.

The interaction between the train, track, and bridge was considered as an interaction between two decoupled subsystems. A first subsystem consisted of the train vehicle simulated as a four-wheelset mass-spring-damper system having two layers of suspensions and ten degrees of freedom. A second subsystem consisted of the track-bridge system assumed to be a top rail beam and a bottom bridge beam coupled by continuous springs and dampers representing the elastic properties of the trackbed smeared over the spacing of the railway ties. The bridge supports were assumed to be rigid or flexible. The equations of motion of a finite element form were derived for each subsystem independently by means of the Newton’s second law. The dynamic interaction between the moving vehicle of the first subsystem and the stationary underlying track-bridge structure of the second subsystem was established by means of a no-separation constraint equation in the contact points between the wheels and the rails. The proposed two-dimensional analysis was intended to accurately describe the vertical behavior of short span bridges subjected to high-frequency excitations due to the passage of high speed trains; therefore, shear deformations, rotational inertia effects, and consistent mass matrices were adopted in the mathematical model. Numerical solutions of the decoupled equations of motion for both subsystems were obtained with the step-by-step direct integration in the time domain using HHT alpha method with a special scheme in the contact interface. The solution accuracy of the proposed method was validated against responses obtained from a semi-analytical method of a train car travelling over a simply supported bridge. The practical engineering application was demonstrated with a case study investigating effects of key parameters in the behavior of a ballasted short span railway bridge. Compared with the moving force model, results showed that for bridges with rigid supports both the vehicle interaction and trackbed produce lower peak responses at resonance speeds with the latter being more significant. However an increase in support flexibility had a greater impact across all speeds in increasing the bridge responses.

Excessively fouled ballast can result a high amount of plastic settlement and reduction of vertical and lateral resistance of the track. A significant portion of railroad maintenance costs is associated with degraded fouled ballast. Therefore, it is important to understand the effects of ballast fouling at different moisture levels on the behavior of ballast under repeated loading conditions. Development of the testing equipment and procedure to better simulate and evaluate the performance of ballast under heavy loading and high traffic conditions can help the railroad industry to better understand the track risk factors. In this study a modified railroad ballast box test apparatus has been used to evaluate the effect of fouling on the plastic deformation of ballast in different moisture conditions up to 2,500,000 cycles, or the equivalent of 300MGT of heavy axle load traffic. The tests have been conducted under equivalent Heavy-Axle Load (HAL) loading conditions and for ballasts with <5%, 15% and 30% fouling. The tests simulate the gradual elastic and plastic deformation of fouled ballast by increase in repetitive cycles of load from dry condition to saturated condition. This paper presents the design and construction of the ballast box device with initial results of the tests. The results show a clear effect of water content and fouling percentage on the amount and rate of both plastic and elastic deformation in cyclic loading. Also, the factor of safety against track failure has been evaluated in highly fouled ballast at saturated conditions.

Brake heating of Railroad Wheels has been known to accelerate shelling, soften the wheel tread and contribute to stress reversal which is a requisite for generating thermal cracks. The effect brake heating has on shakedown has been investigated to a lesser extent, yet even here brake heating can be very important. This research combines field investigations and laboratory work in an attempt to quantify the thermal effects on wheel performance, especially as it relates to sub-surface shelling, microstructural changes and hardening mechanisms. Cyclic tensile tests were conducted at three temperatures to show the relationship between deformation at elevated temperatures and hardening response. Ductility measurements from both monotonic and cyclic tests were used to estimate residual stresses.

The Federal Railroad Administration’s Office of Research and Development is conducting research into passenger locomotive fuel tank crashworthiness. A series of impact tests is being conducted to measure fuel tank deformation under two types of dynamic loading conditions — blunt and raking impacts. This program is intended to result in a better understanding of design features that improve the puncture resistance of passenger locomotive fuel tanks. One reason for performing this program is to aid in development of appropriate standards for puncture resistance to be applied to alternatively-designed fuel tanks, such as on diesel multiple unit (DMU) passenger rail equipment. This paper describes the results of the third blunt impact test of retired F-40 locomotive fuel tanks. The test setup was designed for the Transportation Technology Center (TTC) in Pueblo, Colorado, to impart blunt impacts to the bottom of each fuel tank specimen. The specimens tested to date are from FRA-owned retired F-40 passenger locomotives. To conduct the test, each tank was emptied of fluid and mounted on a crash wall with the bottom surface exposed. A rail cart modified with a “rigid” indenter measuring 12 inches by 12 inches, was released to impact the bottom of fuel tank at a target impact speed. The first two tests, conducted on October 8 and 9, 2013, were designed to impact the center of two different tank designs. Tests were conducted at impact speeds of 4.5 and 6.2 mph and caused maximum residual dents of 5 inches and 1.5 inches, respectively. On August 20, 2014 the test of fuel tank 234 was conducted to impact the tank off-center between two baffles. Force-deformation measurements were collected for each tank during the three tests. The series of tests provide information regarding the influence of tank design on puncture resistance. In the test of tank 234, the target impact speed was 12.5 mph, and the actual impact occurred at 11.2 mph. The test resulted in a residual dent depth of approximately 9 inches, and buckling of several internal baffles. The impact did not result in puncture of the tank. Following the test, the tank was cut open to permit examination of the baffles. This examination revealed a different baffle geometry than was modeled based on pre-test measurements. Finite element analysis (FEA) was used to predict the behavior of the tank during the test. The FE model of the tank required several material properties to be defined in order to capture puncture behavior. The combination of metal plasticity, ductile failure, and element removal would permit the model to simulate puncture for this tank. Following the test, the tank was cut open, revealing a different baffle arrangement than had been initially thought. The post-test FE model was then updated to include the actual baffle arrangement of tank 234. With the actual baffle arrangement included in the model, the FE results are in fairly good agreement with the test. Additional changes to the ductile failure criterion were also made in the post-test model. The objective of this research program is to establish the baseline puncture resistance of current passenger locomotive fuel tanks under dynamic impact conditions and to develop performance requirements to ensure an appropriate level of puncture resistance in alternative fuel tank designs, such as DMU fuel tanks.

An advanced technology for measuring track substructure conditions has been developed by Sol Solution in France. This technology, referred to as the PANDA® and Geo-Endoscopy® technique, comprises driving a variable energy cone penetration device into the track substructure using an instrumented anvil to collect strength (and modulus by correlation) profile with depth. Condition monitoring of the track substructure layers is accomplished through insertion of a camera into the same hole, also called Geoendoscopy®. The tests are commonly faster than Dynamic Cone Penetration (DCP) testing and cause negligible damage to the track substructure with the use of light and portable devices. This paper presents data from PANDA® and Geo-Endoscopy® testing efforts recently carried out under the scope of an ongoing research study at the University of Illinois. The primary objective was to relate the substructure layer properties to plastic layer deformations measured through advanced geotechnical instrumentation. Combined analysis of the PANDA®, Geo-Endoscopy®, and field instrumentation data has been used to highlight the reliability of this innovative technique towards improved evaluation of track substructure layer conditions.