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ASME Conference Presenter Attendance Policy and Archival Proceedings

2016;():V001T00A001. doi:10.1115/JRC2016-NS.
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This online compilation of papers from the 2016 Joint Rail Conference (JRC2016) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Railroad Infrastructure Engineering

2016;():V001T01A001. doi:10.1115/JRC2016-5710.

The Washington Metropolitan Area Transit Authority (WMATA) provides passenger rail service to the nation’s capital. Although the rail system carries only passenger trains, the rail integrity issues that WMATA must manage are similar to those that freight railroads also face. These issues include occurrences of broken rail from internal rail head defects, detection of such defects, and repair of the rail to restore service. Another example is the development of damage on the running surface of the rail, called rolling contact fatigue (RCF). Such surface damage is known to adversely affect the detection of internal rail head defects beneath RCF conditions. While WMATA’s rail integrity issues may be similar to those that freight railroads also encounter, the management of such issues are different, which are also discussed in this paper.

This paper describes the recent experience of broken rails on the WMATA rail system. In addition, results from engineering fracture mechanics analyses are presented to help understand how operational, environmental, design, and maintenance factors influence rail failure.

Topics: Rails
Commentary by Dr. Valentin Fuster
2016;():V001T01A002. doi:10.1115/JRC2016-5714.

This paper presents the equipment and Spectral Analysis of Surface Wave (SASW) approach for non-invasively characterizing railroad track ballast and foundation layers. Surface wave testing on a railroad track is more complicated than that on soil sites or pavements because of the presence of ballast, crossties, and rails as well as the complexity of ballast-soil foundation structure in terms of the variation of shear-wave velocity with depth. Using portable SASW equipment, the Young’s Modulus of the ballast was calculated for both clean and fouled ballast in wet and dry conditions. In addition, the local modulus is determined at different locations under the tie, e.g. tie center or edge, to investigate modulus variation and tie support under a single tie. Expansion of the system to measure the modulus under two adjacent ties is also discussed and may be suitable for evaluating ballast performance under §213.103, which requires ballast to perform the following serviceability functions: (1) transmit and distribute the load of the track and railroad rolling equipment to the subgrade; (2) restrain the track laterally, longitudinally, and vertically under dynamic loads imposed by railroad rolling equipment and thermal stresses exerted by the rail; (3) provide adequate drainage for the track; and (4) maintain proper track crosslevel, surface, and alignment”.

Commentary by Dr. Valentin Fuster
2016;():V001T01A003. doi:10.1115/JRC2016-5715.

This paper illustrates the impact of progressive settlement on a railway bridge transition using a three-dimensional dynamic numerical model that includes the train truck, rails, ties, ballast, subgrade, and bridge abutment and structure. A settlement law that relates tie load to ballast settlement is presented and demonstrated using an iterative fashion to evaluate bridge transition response to 28 MGT. The results illustrate: (1) development of the commonly observed dip about 2.5 to 3.7 m (8 to 12 feet) from the entrance bridge abutment, (2) tie-ballast gaps progressively increase in height and expand to ties outwards from the bridge abutment, (3) a redistribution of load to ties outwards from the bridge abutment as tie-ballast gaps develop and increase, and (4) a ballast surface profile that attempts to minimize tie loads by evenly distributing the wheel load amongst adjacent ties.

Commentary by Dr. Valentin Fuster
2016;():V001T01A004. doi:10.1115/JRC2016-5717.

This work presents the results of a parametric study on the dynamic amplification or impact factor due to transit vehicles. The study was performed on a single span simply supported bridge composed of prestressed concrete bulb tee girders with a concrete deck and direct fixation track. The study varied the key parameters affecting the structural response of the bridge, viz. stiffness of the bridge, vehicle speed and axle configuration. The bridge was numerically modeled using CSI-Bridge software. Stiffness was manipulated in the models by varying the elastic modulus of the concrete. Vehicle speed varied form quasi-static speed of 0.45 m/s (1 mph) to 35.32 m/s (79 mph) in increments of 1.34 m/s (3 mph). Different axle configurations were obtained by modeling trains consisting of different numbers of cars as well as considering different light rail vehicle types. Light rail vehicles defined by transit agencies in Denver, Boston, Washington DC, Phoenix and Houston were considered, which provided a total of 22 different configurations. Vehicle lengths as well the number of axles and spacing between axles varied. The moving loads were modeled using a linear elastic time history analysis. It was assumed that the rail was connected to the bridge deck at distinct points represented by the rail clip connections at approximately 0.76 m (30 inches) on-center. The magnitude of the axle load at a point ramped up from zero to maximum as the axle traveled from the preceding rail clip to the point under consideration and then decreased to zero as the axle traveled onto the following connection point. This triangular variation with time was modeled as a time dependent ramp function which was applied to the different light rail vehicle trains. The time between the start and end of the ramp function was dependent on the speed of the vehicles and train speed was modeled by changing the time base of the ramp function. Dynamic impact was estimated from the models from the ratio of the maximum deflection at midspan under time dependent moving load to the deflection due to a static load analysis. The results showed that the dynamic impact effects on the structure vary greatly with speed and configuration of the vehicle. While the effects generally increased with vehicle speed, the change was not linear and showed in general more than one peak value within the speed range selected. The maximum computed dynamic effect did not occur at the highest speed. The dynamic effect was also dependent on vehicle configuration, with a clear difference in responses between two axle and three axle cars. The overall length of the vehicle had less of an effect. The results were compared to the impact factors typically used by transit agencies and showed that in general for normal ranges of structure stiffness the Agency criteria are conservative or extremely close for vehicle speeds under 35.3 m/s (79 mph). However, the ACI equation for dynamic impact which is the only equation that incorporates vehicle speed and structural stiffness is usually conservative at higher speeds but may be unconservative at lower and medium speeds and does not reflect effects of axle configuration.

Topics: Vehicles , Stiffness
Commentary by Dr. Valentin Fuster
2016;():V001T01A005. doi:10.1115/JRC2016-5718.

Rail grinding has become a widely accepted practice in the railroad industry to not only remove surface defects but to also shape the head of the rail to achieve a specific wheel/rail contact interface. Optimal wheel/rail contact is paramount for a variety of reasons including (but not limited to): reduced rail wear and fatigue defects with associated increased rail life, improved steering, and reduced wheel/rail noise. Historically, the process of profile grinding has been performed through the selection of a grinding pattern from a predefined library of preset motor angles and power settings, as well as grinder traveling speed. By applying calibrated metal removal equations created to estimate the metal removal of a single grinding stone on a specific grinding vehicle and a measured shape of the rail, it is possible to iteratively create a grinding pattern and estimate the post-grind rail shape in both real-time and offline. These dynamically created grinding patterns position and power grinding motors to remove metal only where it needs to be removed to achieve the desired rail shape (template). Over grinding and extraneous grinding is minimized using this grind optimization technique.

The concept of dynamic rail grinding pattern generation was applied to optimize grinding for the VLI railroad in Brazil. Based on a survey of both wheel profiles and rail profiles throughout the VLI network (in which digital coordinates of the transverse cross-sections were recorded using handheld profile measurement devices), new rail grinding templates (desired rail shape dependent upon rail curvature and elevation) were developed to control the wheel/rail interface. These new rail grinding templates were aligned to measured rail profiles categorized by curvature and high/low rail types to create representative average metal removal curves. The resulting metal removal curves were then used as inputs to the dynamic grinding pattern generation functions to create custom grinding patterns specifically calibrated to the grinder in operation on VLI.

Results showed that applying dynamic grinding pattern generation resulted in increased productivity of the grinder (faster speeds and less passes) with corresponding improvement of the post-grind rail shape, i.e., increased quality of the final rail shape.

This paper will discuss the background theory behind dynamic pattern generation and how it can be applied to normal grinding operations. Additionally, an application of this process will be presented which utilized dynamic pattern generation to create targeted corrective grinding patterns for the VLI railroad.

Commentary by Dr. Valentin Fuster
2016;():V001T01A006. doi:10.1115/JRC2016-5724.

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.

Topics: Water
Commentary by Dr. Valentin Fuster
2016;():V001T01A007. doi:10.1115/JRC2016-5725.

Ballast fouling is a problematic track condition that can lead to inadequate ballast performance. Prioritizing remediation of fouled ballast sites is difficult because no relationship between ballast fouling and track performance exists and fouled ballast performance depends on the amount, grain-size, type, plasticity, and moisture content of the fouling material. This paper provides results of an international industry survey on fouled ballast definitions, parameters, limits/standards, and laboratory test results to aid development of a procedure for quantitatively assessing ballast fouling and assessing the ability to: transmit applied train loads to the subgrade, allow drainage, and maintain proper track geometry as required under §213.103.

Commentary by Dr. Valentin Fuster
2016;():V001T01A008. doi:10.1115/JRC2016-5731.

Degrading permafrost conditions around the world has resulted in stability issues for civil structures founded on top of them. Railway lines have very limited tolerance for differential settlements, making it a priority for railway owners in permafrost regions to consider embankment stabilization measures that ensure smooth and safe operations.

Several passive and active engineered solutions have been developed to address the permafrost stability issues, such as awnings, shading boards, crushed rock embankments, ventiduct embankments, and thermosyphons. Local site conditions, including soil type, soil temperature, ice content, and precipitation determines which method is selected for a particular site and in most cases the best stabilization solution is a combination of two or more alternatives. When potential solution can be identified, it will only be implemented if perceived benefits exceed the implementation and maintenance costs.

This paper aims to provide a brief literature review on some common embankment stabilization solutions with consideration to the Hudson Bay Railway (HBR) in northern Manitoba, Canada which has been witnessing thaw settlements for extensive time period. It will discuss the applicability of the different methods, the advantages and disadvantages of the different methods, as well as the benefits to be derived by utilizing a combination of methods.

Commentary by Dr. Valentin Fuster
2016;():V001T01A009. doi:10.1115/JRC2016-5733.

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.

Topics: Stress , Traffic
Commentary by Dr. Valentin Fuster
2016;():V001T01A010. doi:10.1115/JRC2016-5735.

The magnitudes and relative distributions of pressures at the tie/ballast interface are important trackbed engineering design and analysis aspects. The pressures produced by millions of load applications ultimately affect the long-term performance of the track and the service lives of the component materials and layers. Ideally the interstitial pressure intensities can be reduced by distributing pressures uniformly over large areas thereby reducing abrasion of the bottom of the tie and crushing of the surface layer of the ballast.

Multiple earth pressure cells and granular materials pressure cells were used in a series of laboratory tests to ascertain the applicability of using these types of sensors for accurate measurement of the vertical pressures at the tie/ballast interface. Test loads were applied through a section of a tie that was positioned on the ballast. In addition, the effects of several variables were evaluated; — primary variables included the type of granular support — ranging from new and worn ballast size to fine sand size aggregate and the type of cushioning — including resilient pads and thin rubber membranes. These tests were conducted to validate or negate the relative effects of variables on test results.

Pressures calculated from the controlled testing, using a 50,000-lbf (222 kN) MTS hydraulic servo system test machine, were compared to simultaneously measured pressures indicated by the outputs from the pressure cells for machine test loads typical of in-track train loadings. Near perfect correlations were obtained. Furthermore, test repeatability was consistent with little variability of replicated tests. The results indicated that the cells were capable of accurately recording known pressure inputs and therefore applicable for in-track measurement of tie/ballast interfacial pressures.

In-track tests were conducted under typical locomotive and freight car loadings with cells positioned at the tie/ballast interfaces directly under the rail/tie intersection — the point of maximum pressure intensities on the ballast layer. These values were very consistent over periods of elapsed time as the track experienced typical loadings from normal train operations. These test results are described in detail as related to measured pressure intensities and distributions from typical locomotive and freight car wheel loadings of 33,000 and 36,000 lbs. (15,000 and 16,300 kg).

Commentary by Dr. Valentin Fuster
2016;():V001T01A011. doi:10.1115/JRC2016-5739.

Analyzing track geometry defects is of crucial importance for railway safety. Understanding when a defect will need to be repaired can help in both planning a preventive maintenance schedule and reducing the probability of track failures. This paper discusses the data cleaning and analysis processes for modeling track geometry degradation. An analytical data model named the Support Vector Machine (SVM) was developed to model the deterioration of track geometry defects. This paper mainly focuses on the following three defect types — surface, cross level and dip. The model accounts for traffic volume, defect amplitude, track class, speed and other potential factors. Results demonstrate that the proposed analytical data model can have a prediction accuracy above 70%.

Commentary by Dr. Valentin Fuster
2016;():V001T01A012. doi:10.1115/JRC2016-5748.

Railway regulators require that track geometry measurements meet a specific set of minimum safety thresholds. A proper interpretation of track geometry survey data is fundamental for the detection of track exceeding these thresholds and in need of corrective maintenance. Irregular track geometry independent of the minimum safety thresholds can also be used as evidence of degradation in the railway foundation. Therefore, multiple evaluation methods must be applied to the track geometry survey data when assessing foundation degradation. In this study, we compare multiple track geometry evaluation methods in order to assess if they equally identify sections of irregular track geometry along a 335 kilometer section of a Canadian freight railway. The track geometry evaluation methods investigated are the Transport Canada Class 5 minimum safety threshold exceedances and three literature-suggested track quality indices; the Overall Track Geometry Index, the Polish J Index and the Swedish Q Index. Furthermore, this study also investigates the ability of the track quality indices to provide additional insight into track geometry variability in sections without a minimum safety threshold exceedance. The track under investigation is not a Class 5, however, Class 5 minimum safety thresholds were used to produce enough threshold exceedances to allow for the comparison to the track quality indices. The results of the analysis reveal that while the large-scale variability in the three track quality indices is similar, the individual equivalency with the occurrence of Class 5 threshold exceedances is highly variable. Furthermore, only the Overall Track Geometry Index demonstrates the potential to provide consistent additional track geometry variability information.

Topics: Geometry , Railroads
Commentary by Dr. Valentin Fuster
2016;():V001T01A013. doi:10.1115/JRC2016-5749.

Ballast compaction and particle rearrangement cause ballast to rotate and move vertically and horizontally. Ballast movement, including translation and rotation, has a significant effect on track performance. Large movement of ballast particles leads to track geometry roughness, e.g., hanging ties, and thus increases potential of damage and deterioration to rails, ties and fastening components. This study investigated ballast particle movement at different locations beneath a crosstie. In the paper, a wireless device — “SmartRock” was utilized to monitor ballast movement under cyclic loading in laboratory tests. The SmartRock has a shape of a realistic ballast particle. Inside the SmartRock was imbedded a tri-axial accelerometer, tri-axial gyroscope, and tri-axial magnetometer with 9 degrees of freedom so that particle translation, rotation and orientation can be interpreted, relatively. The real-time measurements were recorded by the SmartRock and then sent to a computer via Bluetooth. In the laboratory tests, a ballast box was constructed. In the ballast box, a half section of a typical railroad track was constructed. Five hundred cyclic load repetitions were applied on the top of the rail. Translational and rotational accelerations of the particle were recorded by the “SmartRock”. Three ballast box tests were conducted. Two SmartRocks were placed beneath the middle of tie and the edge of tie, respectively but at different depths during each test — right under the tie, 12 cm beneath the tie and 25 cm beneath the tie. The results indicated that (1) ballast particles had translational as well as rotational modes under cyclic loading; (2) ballast particles had rotation together with horizontal translation; (3) particle rotation were higher beneath the edge of tie than those beneath the middle of tie; (4) Ballast movement were significantly reduced with depth. The paper also further confirmed that the SmartRock was capable of recording real-time translational and rotational accelerations, which would not have altered the motions of surrounding ballast particles due to its realistic shape of a particle, hence, provided a new means to monitor ballast particle movement in railroad engineering.

Commentary by Dr. Valentin Fuster
2016;():V001T01A014. doi:10.1115/JRC2016-5751.

Accurate knowledge of transfer length has been shown to be crucial to the goal of maintaining continuous production quality in the modern manufacture of prestressed concrete railroad ties. Traditional manual laboratory methods, such as the conventional Whittemore method which requires the use of embedded reference points, are clearly not suitable for production operation or for use in reliable production quality-control.

This paper presents the results of another advance in the development of automated transfer length measurement systems for practical in-plant operation. The new device offers a significant improvement over the previously successful automated Laser-Speckle Imaging (LSI) system developed by the authors. The earlier automated LSI strain measurement system has been modified to provide significantly improved optical resolution of longitudinal surface strain, with the ability to resolve longitudinal prestressed concrete crosstie surface strain without time-consuming special surface preparation. More importantly, the new system is also capable of making measurements of strain in a real-time “on-the-fly” manner over the entire distance range of interest on the tie associated with transfer length development. It features both a “jog” mode of operation, similar to its predecessor in which measurements of longitudinal surface strain are automatically captured in arbitrary spatial increments over the entire range of the computer-controlled traverse, and an “on-the-fly” mode in which measurements of longitudinal surface strain are captured without the need for stopping at each measurement location. This latter mode offers the potential of a much faster capture of the strain profile and should prove to be very beneficial for field testing and in-plant diagnostic applications.

The performance of this new system is first demonstrated using a new calibrated step-wise uniform strain field setup which has been developed specifically for verification of this and other automated transfer length measurement systems. This verification system produces a calibrated step change in surface deflection, effectively subjecting the automated strain measurement system to an ideal step change in longitudinal strain for a given gauge length. In addition, the new automated system is demonstrated by conducting measurements of longitudinal surface strain on prestressed concrete crossties in a manufacturing plant. For this latter experimental in-plant testing, strain measurements using the new system are also compared directly with those from the recently introduced 6-camera transfer length measurement system, as well as with the traditional Whittemore gauge measurements. The agreement between these independent measurement systems is remarkable, and it is shown to even be possible to discern differences in strain profile and associated transfer length between adjacent crossties within a given casting bed. This new automated and high-resolution device should provide a very convenient and fast diagnostic tool for the manufacturer to quickly identify the need to modify production (e.g., concrete mix) if transfer length specifications fall out of desired range.

Commentary by Dr. Valentin Fuster
2016;():V001T01A015. doi:10.1115/JRC2016-5753.

Accurate unbiased assessment of transfer length for prestressed concrete railroad ties requires detailed knowledge of the longitudinal variation of geometrical cross-section parameters responsible for establishing the resulting surface strain profile. This is because the complex cross-sectional shape produces a non-uniform strain plateau region, which makes the accurate evaluation of transfer length more difficult. In particular, human judgment of a “plateau region” for assessment of the average maximum strain becomes subject to large uncertainty, and clearly this procedure cannot be used in any type of automated in-plant transfer length diagnostics. The important geometrical tie parameters include the cross-sectional area, centroid, moment of inertia, and the eccentricity of the prestressing wires. If a CAD drawing is available, this information can be digitally extracted from the CAD model representation of the crosstie. In fact, this digital extraction has been done and has already been in use for some time in assessing transfer length for one of the common crosstie manufacturer designs. However, current research efforts are investigating the characteristics of existing crossties which have been in track for many years, for which CAD drawings of the original designs are unlikely to be available.

The objective of the current research is to develop a comprehensive understanding of the material characteristics that have caused splitting failures in prestressed concrete railroad ties, and those characteristics that have resulted in ties that have performed well after many years in track. As part of this effort, a three-dimensional (3D) Optical Scanning System is being used to accurately scan and quantify the surface geometry of previously manufactured ties that have been in service, so as to produce an accurate 3D CAD model for later analysis associated with the above long-term research objectives.

For the initial phase of this work, a sample from the CXT crossties of known geometrical characteristics that were subjected to representative long-term loading at the TTCI Facility in Pueblo Colorado, was scanned so as to accurately map out detailed 3D tie surface geometry. These ties were cast using the same concrete materials but with different prestressing wires, and were all subjected to the same extreme in-track loading for a period of several years. A commercially-available 3D Laser-Based Optical Scanning System, having a maximum spatial resolution of approximately 0.1mm, was used to perform the surface scanning operations presented in this paper. The CXT tie provides a useful initial evaluation of the accuracy and general feature capture capability of the scanning procedure, since a 3D CAD model for this tie has been provided by the manufacturer. A detailed qualitative and quantitative analysis is presented which compares the 3D CXT CAD model geometry with the 3D geometry of the experimentally scanned ties. Illustrations as to how this 3D technique can reveal such features as abrasion and wear, along with the longitudinal variation of the above mentioned cross-section parameters associated with longitudinal surface strain and transfer length assessment, are included in this paper.

Commentary by Dr. Valentin Fuster
2016;():V001T01A016. doi:10.1115/JRC2016-5761.

Load tests were conducted on pretensioned concrete prisms cast with 13 different 5.32-mm-diameter prestressing wire types that are used in the manufacture of pretensioned concrete railroad ties worldwide. The tests were specifically designed to evaluate the bond performance of wires with different indentation type under the cyclic loading. The prestressing wires were denoted “WA” through “WM” and indentation types included smooth, spiral, chevron, diamond, 2-dot and 4-dot. Four wires were embedded into each concrete prism, which had a 3.5″ (88.9 mm) × 3.5″ (88.9 mm) square cross section. The wires were initially pulled to 7000 pounds (31.14 KN) and gradually de-tensioned when the concrete compressive strength reached 4500 psi (31.03 MPa). A consistent concrete mixture with type III cement, water-cement ratio of 0.32 and a 6-in. slump was used for all prisms.

For each type of wire one 69 in-long (175.26 cm) prism was tested in 4-point-bending under the cyclic load and one under static load at 20-in (50.8 cm) embedment length. For cyclic load tests, the prisms were supported by two rollers spanning 45″ (114.3 cm) and load was applied on a spreading beam set on the top of the test prism. The prism setup and loading configuration were symmetric and load was applied to the prism from spreading beam to two bearings spaced 15″ (38.1 cm) apart. During each test, a concentrated load with the rate of 250 lb/min (1112 N/min) was applied until two cracks were observed at the maximum moment region on the test prisms (region between two bearings).

Once cracks were observed, the load was held constant for 3 minutes at the cracking load. After holding load constant for three minutes, load started to cycle between 400 lb (1779 N) to 4000 lb (17790 N) with the frequency of 3 Hz. The test was designed to go through 200,000 cycles and interlock limits were assigned to the program to stop the test in case of prism failure under the cyclic loading. For prisms able to finish 200,000 cycles of load, the procedure was to unload to zero and start loading the prism with the rate of 250 lb/min (1112 N/min) until prism failed. Values of load, mid-span deflection, and wires end-slip were continuously monitored and recorded during each test. Load-vs-deflection graphs were then plotted and compared for prisms with each wire type, and the maximum sustained moment was also calculated for each test. Also, a set of statically load tests were conducted on the identical pretensioned prisms to compare the results of statically and cyclically load tests. The cyclic load tests revealed that there is a significant difference in the bond performance of different wire types under the cyclic loading and they behave differently under cycles of loadings and unloadings.

Topics: Concretes , Wire
Commentary by Dr. Valentin Fuster
2016;():V001T01A017. doi:10.1115/JRC2016-5762.

Load tests were conducted on pretensioned members made with five different strands (three 7-wire strands and two 3-wire strands) to determine the effect of concrete release strength on the development length and flexural capacity of members. Strands named generically SA, SC, SD, SE and SF and they were all indented except SA (no surface indentation). All strands had diameter of 3/8″ (9.52 mm) except SC which had diameter of 5/16″ (7.94 mm). Among all types of strands used in manufacturing of test prisms, SC and SF were 3-wire strands, while SA, SD and SE were 7-wire strands. A consistent concrete mixture was used for the manufacture of all test specimens, and the different release strengths were obtained by allowing the specimens to cure for different amounts of time prior to de-tensioning. For SA, SD, SE and SF strands, each prismatic specimen (prism) had a 5.5″ (139.7 mm) × 5.5″ (139.7 mm) square cross section with four strands arranged symmetrically. However, prisms made with SC strand had 4.5″ (114.3 mm) × 4.5″ (114.3 mm) square cross section with four strands arranged symmetrically. The prisms were identical except for the strand type and the compressive strength at the time of de-tensioning. All four strands were pulled and de-tensioned gradually when the concrete compressive strength reached 3500 (24.13 MPa), 4500 (31.03 MPa) and 6000 (41.37 MPa) psi. Precise de-tensioning strengths were ensured by testing 4-in.-diameter (101.6 mm) × 8-in.-long (203.2 mm) compression strength cylinders that were temperature match-cured.

The prisms were loaded in 3-point-bending to determine the ultimate bond characteristics of each reinforcement type for the different concrete release strengths. A loading rate of 900 lb/min (4003 N/min) for 5.5″ (139.7 mm) × 5.5″ (139.7 mm) prisms was applied at mid-span and the maximum sustained moment was calculated for each. Same procedure with loading rate of 500 lb/min (2224 N/min) was applied to 4.5″ (114.3 mm) × 4.5″ (114.3 mm) prisms. Three 69-in.-long (175.26 cm) prisms, each having different concrete release strength, were tested with each of the 5 strand types. Two out of three testing prisms were tested at only one end and one was tested at its both ends. Thus, for each strand type and concrete release strength evaluated, a total of 4 tests were conducted for a total of 60 tests (5 strand types × 3 release strengths × 4 tested embedment lengths). Test results indicate that the concrete compressive strength at de-tensioning can have a direct impact on the ultimate flexural capacity of the members, and this has significant design implications for pretensioned concrete railroad ties. Results are discussed and recommendations made.

Topics: Concretes
Commentary by Dr. Valentin Fuster
2016;():V001T01A018. doi:10.1115/JRC2016-5765.

Live load performance of a recently constructed, prestressed concrete bridge was investigated to determine the Impact Factors (IMs), the Girder Distribution Factors (GDFs). The bridge was subjected to controlled static and dynamic loading using two Denver Transit Partners (DTP) electric-multiple-unit rail cars prior to a commuter rail line being placed into service. The rail cars travelled along northbound and southbound tracks of the four span, horizontally curved, bridge at various speeds. A total 24 tests were conducted and response was measured using a combination of strain sensors and accelerometers installed at critical sections on the supporting girders. Results for IMs and GDFs obtained from the field tests are presented. These results are also compared against relevant code provisions and these preliminary results indicated that IMs are insensitive to train speed and are smaller than investigated code provisions and that measured GDFs were different than those provided by these code provisions.

Commentary by Dr. Valentin Fuster
2016;():V001T01A019. doi:10.1115/JRC2016-5766.

Vibrations of the slab track system propagated to the environment are estimated for railway tracks in which substructures are made from hot mix asphalt concrete (HMAC) and/or rubber modified asphalt concrete (RMAC). Sensitivity analysis is done to determine the ability of such layers to reduce vibrations with various frequencies, load amplitude and thicknesses of asphalt layers. Different types of substructures i.e. with or without the concrete base layer are used to assess propagated vibrations caused by the moving train. A finite element (FE) model of the ballast-less track substructure is built and the dynamic analysis is performed for various track models with asphalt layers. The FE model is in principle a two-dimensional plane-strain model with the parameters according to the common slab track systems. Ground vibrations i.e. dynamic accelerations are extracted at different recording points around the track with lateral distances 0, 10 and 20m from the loading axis. The outputs of numerical simulations for different substructure models are obtained and the possibilities of vibration reductions by various methods are discussed.

Commentary by Dr. Valentin Fuster
2016;():V001T01A020. doi:10.1115/JRC2016-5776.

Concrete railroad ties have been used in increasing numbers in the U.S., particularly in high-speed rail, heavy-haul freight lines, and new track construction because of their reduced deflections, durability, and competitive cost. In-track assessment of concrete railroad ties can be a challenge, however because many exterior tie surfaces are covered by tie pads and rail or ballast. This damage may include concrete section wear from abrasion, cracking, or crumbling, or other types of defects. Damage internal to the concrete can also not be seen visually. The time and cost needed to inspect these tie surfaces means that it is not routinely performed. Non-destructive testing offers promise as a way to assess concrete tie integrity without having to remove ballast, however more information is needed to know how well non-destructive techniques work in detecting damage. Two of the most promising techniques for investigating the integrity of concrete non-destructively are ultrasonic pulse velocity and impact-echo. Ultrasonic pulse velocity (UPV) and Impact-echo (IE) were applied to investigate the uniformity of concrete railroad tie and its cavities, cracks and defects for concrete ties taken from track after service. This paper evaluated the variability of the test results in UPV and IE testing condition in which two concrete railroad ties with same manufacture and load history condition were tested in both methods. Two additional concrete ties with the same manufacture and load history as each other with visible longitudinal cracks were also examined to see how the damage affected the variability measured. For this purpose, wave pulse for every full length tie from full top, half top, longitude and two sides were measured using ultrasonic pulse (ASTM C597). Also, thickness of concrete ties on both sides, including rail seat location and the middle were assessed by standard tests method for measuring the p-wave speed and the thickness of concrete using the impact-echo method (ASTM C1383). Advice is given on how to interpret ultrasonic pulse velocity and impact-echo measurements and given the variability of the test method how to flag ties for potential deterioration given that most ties in service will not have initial measurements taken before damage for comparison.

Commentary by Dr. Valentin Fuster
2016;():V001T01A021. doi:10.1115/JRC2016-5779.

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.

Commentary by Dr. Valentin Fuster
2016;():V001T01A022. doi:10.1115/JRC2016-5781.

In order to quantify the effect of different reinforcement types on transfer lengths, an extensive study was conducted with the selected group of twelve different reinforcement types. These reinforcements are extensively used to produce concrete railroad ties across the world. These employed twelve (12) different types are of 5.32 mm diameter wires with different surface indent geometries. A research team from Kansas state university visited a PCI certified concrete tie manufacturing plant during January 2013. During the plant visit, four (4) concrete railroad ties were cast for each reinforcement type for a total of 48 ties. Considerable part of the study conducted at the plant was previously published by the authors. However for effective understanding, brief explanation of the tie manufacturing process will be presented in this paper. Strain measuring points were mounted on the bottom surface of a concrete railroad tie during the casting process. Proper measures were taken to safeguard these strain measuring points during loading. Transfer lengths were calculated using these mounted strain measuring points. Transfer length measurements were calculated at the plant, immediately after the application of prestressing forces to the concrete ties. After the casting process, two ties for each reinforcement type were stored at plant location for approximately one year and the remaining two ties (companion ties) for the each reinforcement types were shipped and stored at Kansas state university. Transfer length measurements were again calculated at this stage for all 48 ties. Ties stored at plant location were later subjected to cumulative in-track railroad loading of 85 million gross tons over six (6) months period of time. Whereas, the companion ties stored at Kansas state university were not subjected to any loading. Transfer lengths are calculated and compared at this stage and presented [4] in the past.

Ties which were already subjected to 85 million gross tons were further loaded to cumulative total of 236.3 million gross tons and the companion ties stored at Kansas State University were not subjected to any loading. Transfer lengths for the ties (twenty four) that were subjected 263.3 million gross tons were calculated and presented in this paper with detailed explanation. Transfer length behavior under different magnitudes of loading is also presented along with the discussion.

Commentary by Dr. Valentin Fuster
2016;():V001T01A023. doi:10.1115/JRC2016-5782.

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.

Commentary by Dr. Valentin Fuster
2016;():V001T01A024. doi:10.1115/JRC2016-5783.

In ballasted concrete tie track, the tie-ballast interface can deteriorate resulting in concrete tie bottom abrasion, ballast pulverization and/or voids in tie-ballast interfaces. Tie-ballast voids toward tie ends can lead to unfavorable center binding support conditions that can result in premature concrete tie failure and possible train derailment. Direct detection of these conditions is difficult. There is a strong interest in assessing the concrete tie-ballast interface conditions indirectly using measured vertical deflections.

This paper seeks to establish a link between the vertical deflection profile of a concrete tie top surface and the tie-ballast interface condition using the finite element analysis (FEA) method. The concrete tie is modeled as a concrete matrix embedded with prestressing steel strands or wires. The configurations of two commonly used concrete ties, one with 8 prestressing strands and the other with 20 prestressing wires, are employed in this study. All models are three-dimensional and symmetric about the tie center. A damaged plasticity model that can predict onset and propagation of tensile cracks is applied to the concrete material. The steel-concrete interface is homogenized and represented with a thin layer of cohesive elements sandwiched between steel and concrete elements. Strand- or wire-specific elasto-plastic bond models developed at the Volpe Center are applied to the cohesive elements to account for the interface bonding mechanisms. FE models are developed for both original and worn concrete ties, with the latter assuming hypothetical patterns of reduced cross sections resulting from abrasive interactions with the ballast. Static analyses of pretension release in these concrete ties are conducted, and vertical deflection gradients along tie lengths are calculated and shown to correspond well with the worn cross sectional patterns for a given reinforcement type.

The ballast is further modeled with Extended Drucker-Prager plasticity, and hypothetical voids are applied toward the tie ends along the concrete tie-ballast interface to simulate center binding support conditions. The distance range over which the concrete tie is supported in the center is variable and yields different center binding severity. Static simulations are completed with vertical rail seat loads applied on the concrete tie-ballast assembly. The influences of various factors on the vertical deflection profile, including tie type, vertical load magnitude, center binding severity, cross sectional material loss and prestress loss, are examined based on the FEA results.

The work presented in this paper demonstrates the potential of using the vertical deflection profile of concrete tie top surfaces to assess deteriorations in the tie-ballast interface. The simulation results further help to clarify minimum technical requirements on inspection technologies that measure concrete tie vertical deflection profiles.

Topics: Concretes , Deflection
Commentary by Dr. Valentin Fuster
2016;():V001T01A025. doi:10.1115/JRC2016-5787.

The purpose of this research is to establish mathematical models that predicts the bond strength of a reinforcement wire in prestressed concrete members, given the known geometrical features of the wire. A total of nineteen geometrical features of the reinforcement wire were measured and extracted by a precision non-contact profilometer. With these mathematical models, prestressing reinforcement wires can now be analyzed for their bond strength without destructive testing. These mathematical models, based upon a large collection of empirical data via prestressing reinforcement wires from various wire manufacturers in US and Europe, have the potential to serve as quality assessment tools in reinforcement wire and prestressed concrete member production. Most of these models are very simple and easy to implement in practice, which could provide insight into which reinforcement wires provide the greatest bond strength and which combinations of geometrical features of the reinforcement wire are responsible for providing the bond strength.

Our various empirical models have shown that the indent side-wall angle, which is suggested by the ASTM-A881/A881M, may not be the only significant geometrical feature correlated to the transfer length and bond strengths. On the contrary, features such as the indent surface area, indent width, indent edge surface area, indent volume, and release strengths do have significant correlations with the ultimate transfer lengths of the prestressed concrete members. Extensive experiments and testing performed at the Structures Laboratory in Kansas State University, as well as field tests at Transportation Technology Center, Inc. (TTCI) and one Prestressed Concrete Railroad Tie manufacturing facility, have been used to confirm the model predictions.

In addition, our experimental results suggest that the maximum pull out force in the un-tensioned pullout testing has significant correlation with the ultimate transfer length. This finding could provide reinforcement wire manufactures with a quality assurance tool for testing their wires prior to the production.

The resultant mathematical model relating the wire geometrical features to transfer length is referred to as the Bond Index Number (BIN). The BIN is shown to provide a numerical measure of the bond strength of prestressing steel reinforcement wire, without the need for performing destructive tests with the reinforcement wire. We believe that with the BIN and the maximal pull-out forces from the un-tensioned pull-out tests, one can have better insight into the optimal reinforcement wire design by testing the performance of wires before they are put into production lines.

Commentary by Dr. Valentin Fuster
2016;():V001T01A026. doi:10.1115/JRC2016-5793.

Previous research has focused on the effect of rail cant on rail wear and wheel/rail interaction, indicating that a steeper rail cant results in increased wear on rails and wheels. However, no research has investigated the effect of rail cant on the crosstie rail seat pressure distribution. Past research at the University of Illinois at Urbana-Champaign (UIUC) looked into the effect of negative (reverse) rail cant on pressure distribution across the rail seat utilizing matrix-based tactile surface sensors (MBTSS) on artificially created rail seat wear profile at TTC, Pueblo. These results showed that the pressure distribution became more non uniform with increasing negative rail cant. This paper looks into the effect of ‘design’ rail cant on pressure distribution across the rail seat. Static tests were carried out on 1:30 and 1:40 cant crossties imparting a predefined sequence of vertical and lateral load combinations. MBTSS and potentiometers were used to measure pressure distribution and rail rotation respectively. The 1:30 cant distributed load more evenly than 1:40 cant at lateral to vertical force ratios greater than 0.4. The two rail cants did not show significant differences in the values of average pressure, contact area, or rail rotation.

Topics: Pressure , Concretes , Design , Rails
Commentary by Dr. Valentin Fuster
2016;():V001T01A027. doi:10.1115/JRC2016-5798.

A High-Strength Reduced-Modulus High Performance Concrete (HSRM-HPC) for use in prestressed concrete rail ties has been developed by the authors. The HSRM-HPC material was originally considered for highway bridges but was rejected because of the accidental finding of the low modulus of elasticity. It is shown that the elastic modulus of the HSRM-HPC is reduced as much as 50% compared to the conventional HPC of the same strength while preserving all other properties of the conventional HPC. The use of the more flexible HSRM-HPC in concrete ties leads to reduced stress amplitudes and regularized stress fields at the rail seat area and the middle segment of the tie, which are the two most critical areas of tie failure. This work discusses the development and characterization of the HSRM HPC material, as well as current work on the performance assessment of such ties. The material development, material characterization, and performance assessment is conducted through experimental testing and computer simulations. The benefits of HSRM-HPC ties are quantified and discussed.

Commentary by Dr. Valentin Fuster
2016;():V001T01A028. doi:10.1115/JRC2016-5800.

GEOTRACK is a software for track structure analysis under vertical quasi-dynamic loads. It uses a three dimensional, multilayer elastic model for determining track and subgrade responses. Originally developed by Chang et al. in 1980, GEOTRACK has been validated by several studies to closely match the elastic response of railroad tracks in operation. GEOTRACK can be used to calculate different track response values in the superstructure as well as substructure. The most recent version of GEOTRACK, GEOTRACK for Windows, was developed in 1992 at the University of Massachusetts, Amherst. However, the source code for this executable version was lost before the software rights were acquired by the Transportation Technology Center, Inc. (TTCI). Accordingly, the current executable version, which only runs on 32-bit Windows operating systems, cannot be upgraded. The source code currently available to TTCI does not correspond to the current executable version of GEOTRACK, and was written in the VAX FORTRAN language, making it incompatible with modern compilers and operating systems. Considering the widespread need for GEOTRACK by researchers and practitioners in the railroad industry, a research collaboration was recently initiated between Boise State University and TTCI to develop a new upgraded version of the GETORACK program.

This paper will present preliminary results from this developmental effort, and will introduce different features being incorporated into the new version. Developed using the C#.net platform, the new program features an intuitive Graphical User Interface (GUI) with enhanced pre- and post-processing capabilities. Fundamental approach behind railroad track analysis using the multilayer elastic theory is presented in this paper along with basic analysis framework being used in the newly developed program.

Commentary by Dr. Valentin Fuster
2016;():V001T01A029. doi:10.1115/JRC2016-5802.

As one of the weakest locations in the track superstructure, the rail joint encounters different types of defects and failures, including rail bolt-hole cracking, rail head-web cracking or separation, broken or missing bolts, and joint bar cracking. The defects and failures are mainly initiated by the discontinuities of both geometric and mechanical properties due to the rail joint, and the high impact loads induced by the discontinuities. Continuous welded rail (CWR) overcomes most disadvantages of the rail joints. However, a large number of rail joints still exist in North American Railroads for a variety of reasons, and bolted joints are especially prevalent in early-built rail transit systems. Cracks are often found to initiate in the area of the first bolt-hole and rail-head-to-web fillet (upper fillet) at the rail end among bolted rail joints, which might cause further defects, such as rail breaks or loss of rail running surface. Previous research conducted at the University of Illinois at Urbana-Champaign (UIUC) has established an elastic static Finite Element (FE) model to study the stress distribution of the bolted rail joint with particular emphasis on rail end bolt-hole and upper fillet areas. Based on the stress calculated from the FE models, this paper focuses on the fatigue performance of upper fillet under different impact wheel load factors and crosstie support configurations. Preliminary results show that the estimated fatigue life of rail end upper fillet decreases as impact factor increases, and that a supported joint performs better than a suspended joint on upper fillet fatigue life.

Commentary by Dr. Valentin Fuster
2016;():V001T01A030. doi:10.1115/JRC2016-5805.

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.

Topics: Grouting , Railroads
Commentary by Dr. Valentin Fuster
2016;():V001T01A031. doi:10.1115/JRC2016-5814.

Ballastless track slab offers excellent stability and durability and has been well accepted in high-speed railways worldwide. Rails are typically laid on precast concrete slabs that are subjected to dynamic load transferred from the rails. Cracks can be induced by shrinkage and mechanical loading in concrete, which accelerates the degradation and affects the performance of the track slab. As tens of thousands of miles of ballastless track are constructed, effective and efficient maintenance for the concrete slabs has become an issue. In this paper, ultra-high performance concrete (UHPC) is proposed to fabricate ballastless track slab. UHPC is a superior fiber-reinforced, cementitioius mortar, which has greatly-improved mechanical strengths and durability. A recently-developed UHPC is evaluated in terms of the flowability, durability, shrinkage, and mechanical properties. A functionally-graded slab design is proposed with the consideration of initial material cost. The slab is cast with two layers: a layer of conventional concrete at the bottom, and a layer of UHPC on the top. A three-dimensional finite element model is developed for ballastless track slab whose flexural performance is investigated and compared with that of slab made with conventional concrete. Concrete damage plasticity model is incorporated to consider the post-cracking behavior. The results indicate that the proposed UHPC is promising for fabricating ballastless track slab with superior performance.

Topics: Concretes , Slabs
Commentary by Dr. Valentin Fuster
2016;():V001T01A032. doi:10.1115/JRC2016-5834.

High Performance Concrete (HPC) with early strength development is the material of choice in the fabrication of prestressed concrete railroad ties. The higher strength of HPC results in significantly higher values of the Elastic Modulus and increases the brittleness and the rigidity of the material, leading to premature cracking and the deterioration of the railroad ties. A High-Strength Reduced-Modulus High Performance Concrete (HSRM-HPC) material has been developed by the authors and used in the fabrication of prototype concrete ties. Detailed models based on the Finite Element Method of the HSRM-HPC have been developed to simulate the ASTM-C469 tests for elastic modulus. The HSRM-HPC constituent materials, i.e. aggregates and cement mortar, have been explicitly modeled and assigned properties determined experimentally. Aggregates size and distribution is modeled using a combination of probabilistic distributions consistent with the results of an experimental sieve analysis. Details of the development of each model are discussed. The models are verified with experimental data. Assessment studies have been performed in order to optimize the models with respect to efficiency, the quality of the results and computational times.

Commentary by Dr. Valentin Fuster
2016;():V001T01A033. doi:10.1115/JRC2016-5839.

Railroad bridges experience dynamic wheel load augment from rolling stock that cross the bridges, due to nominal bridge and suspension dynamics, as well as anomalies such as wheel flats. The level of dynamic augment is particularly high for steam locomotives due to the hammer blow effect associated with the driven wheels. Tests conducted in the early-mid 20th century had quantified some of these effects, and the resulting findings have been part of the impact formulae presented in the AREMA Railway Engineering Manual.

However, there was concern that the impact associated with some of the non-cross counter-balanced, lighter, older locomotives, could be higher than specified by AREMA formulae. This paper describes the methodology and results from a series of tests that evaluated the levels of dynamic augment experienced by railroad track and an exemplar bridge under a set of narrow gauge steam locomotives, and compares the measurements to the design values specified in the AREMA Manual. Vertical and lateral loads on railroad track, and strain levels on multiple critical bridge members were measured under three different classes of light, narrow gauge steam locomotives, over a range of operating speeds and conditions. The tests were conducted on a 120 ft span, through truss bridge, and adjacent track on a tourist railroad.

Dynamic augment values measured during the tests were generally lower than the values expected from AREMA formulae. Similarly, the peak lateral loads measured appear to be nominal and lower than the AREMA prescribed values. However, it should be kept in mind that these results are from tests conducted with three relatively light, narrow gauge locomotives, on specific bridge and track, whereas, the AREMA formulae are intended to cover a wider range of conditions. These tests tend to show that the legacy standards are conservative and are applicable to calculating regulatory required bridge loads where steam locomotives are concerned.

Topics: Stress , Locomotives , Steam
Commentary by Dr. Valentin Fuster
2016;():V001T01A034. doi:10.1115/JRC2016-5840.

Ballast consisting of large sized aggregate particles with uniform size distribution is an essential component of the track substructure, to facilitate load distribution and drainage. As freight tonnage accumulates with traffic, ballast will accumulate an increasing percentage of fines due to either aggregate breakdown or outside contamination such as subgrade soil intrusion and coal dust collection. According to the classical text by Selig and Waters [1], ballast degradation from traffic involves up to 76% of all fouling cases; voids will be occupied by fines from the bottom of ballast layer gradually causing ballast clogging and losing its drainage ability. When moisture is trapped within ballast, especially fouled ballast, ballast layer stability is compromised. In the recent studies at the University of Illinois, the focus has been to evaluate behavior of fouled ballast due to aggregate degradation using large scale triaxial testing. To investigate the effects of moisture on degraded ballast, fouled ballast was generated in the laboratory through controlled Los Angeles (LA) abrasion tests intended to mimic aggregate abrasion and breakdown and generate fouled ballast at compositions similar to those observed in the field due to repeated train loadings. Triaxial shear strength tests were performed on the fouled ballast at different moisture contents. Important findings of this preliminary study on characterizing wet fouled ballast are presented in this paper. Moisture was found to have a significant effect on the fouled ballast strength behavior. Adding a small amount of 3% moisture (by weight of particles smaller than 3/8 in. size or smaller than 9.5 mm) caused test specimens to indicate approximately 50% decrease in shear strength of the dry fouled ballast. Wet fouled ballast samples peaked at significantly lower maximum deviator stress values at relatively smaller axial strains and remained at these low levels as the axial strain was increased.

Topics: Shear strength
Commentary by Dr. Valentin Fuster
2016;():V001T01A035. doi:10.1115/JRC2016-5842.

Qualification of prestressed concrete railroad ties is currently performed through testing at the design level following established AREMA guidelines, while important parameters, such as the strand transfer length, are typically not identified. Conventional testing practices are time demanding, expensive and labor intensive. Consequently, implementation of highly reliable, yet cost effective, quality control procedures at the tie production stage is highly appropriate and desired.

In this work, the authors developed a stereo-vision system for both laboratory and industrial environments to measure the 3-D strain fields on the surfaces of prestressed concrete railroad ties. The proposed measurement system is based on the Digital Image Correlation (DIC) techniques developed in University of South Carolina (USC) laboratories over the past three decades. It is a non-destructive, non-contacting technique that has been successfully applied to obtain full-field measurements for a wide range of materials, loading types and temperature conditions. Known as 3D-DIC or Stereo-DIC, the method employs a stereo-vision system to successfully perform quality assessment of concrete ties in relation to the determination of: (i) the transfer length in both laboratory and production facility environments and (ii) full strain fields during product qualification tests to identify product defects. The proposed procedure is introduced and verified through application in a laboratory environment. The implementation of the method is presented and the cost effectiveness, accuracy, and versatility are discussed.

Commentary by Dr. Valentin Fuster

Rail Equipment Engineering

2016;():V001T02A001. doi:10.1115/JRC2016-5704.

The intention of this paper is to discuss the key components of reliability processes as applied to rail vehicle acquisition programs, and their effects on the ‘stakeholders’ involved. The ‘stakeholders’ identified in this context, are those that are directly involved in the new vehicle project, namely; the rail operating authority with its associated divisions, the car builder with its internal departments, equipment and system suppliers to the car builder, consultants and governing associations.

Topics: Reliability , Vehicles
Commentary by Dr. Valentin Fuster
2016;():V001T02A002. doi:10.1115/JRC2016-5711.

Train car wheels are subjected to different types of damages due to their interactions with the brake shoes and track. If not detected early, these defects can worsen, possibly causing damage to the bogie and rail. In the worst-case scenario, this rail damage can possibly lead to later derailments, a serious concern for the rail industry. Therefore, automatic inspection and detection of wheel defects are high priority research areas. An automatic detection system not only can prevent train and rail damage, but also can reduce operating costs as an alternative for tedious and expensive manned inspection. The main contribution of this paper is to develop a computer vision method for automatically detecting the defects of rail car wheels using a wayside thermal camera. We concentrate on identification of flat-spotted/sliding wheels, which is an important issue for both wheel and suspension hardware and also rail and track structure. Flat spots occur when a wheel locks up and slides while the vehicle is still moving. As a consequence, this process heats up local areas on the metal wheel, which can be observed and potentially detected in thermal imagery. Excessive heat buildup at the flat spot will eventually lead to additional wheel and possibly rail damage, reducing the life of other train wheels and suspension components, such as bearings. Furthermore, as a byproduct of our algorithm, we propose a method for detecting hot bearings. A major part of our proposed hot bearing detection algorithm is common with our sliding wheel detection algorithm. In this paper, we first propose an automatic detection and segmentation method that identifies the wheel and bearing portion of the image. We then develop a computer vision method, using Histogram of Oriented Gradients to extract features of these regions. These feature descriptors are input to a Support Vector Machine classifier, a fast classifier with a good detection rate, which can detect abnormalities in the wheel. We demonstrate our methods on several real data sets taken on a Union Pacific rail line, identifying sliding wheels and hot bearings in these images.

Topics: Bearings , Wheels
Commentary by Dr. Valentin Fuster
2016;():V001T02A003. doi:10.1115/JRC2016-5712.

This paper is the first in a two-part series on the puncture performance of railroad tank cars carrying hazardous materials in the event of an accident. Various metrics are often mentioned in the open literature to characterize the structural performance of tank cars under accident loading conditions. One of the consequences in terms of structural damage to the tank during accidents is puncture. This two-part series of papers focuses on four metrics to quantify the performance of tank cars against the threat of puncture: (1) speed, (2) force, (3) energy, and (4) conditional probability of release.

In this paper (Part I), generalized tank car impact scenarios are illustrated. Particular focus is given to the generalized shell impact scenario because performance-based requirements for shell puncture resistance are being considered by the regulatory agencies in United States and Canada. Definitions for the four performance metrics are given. Physical and mathematical relationships among these metrics are outlined. Strengths and limitations of these performance metrics are discussed.

In Part II, the multi-disciplinary approach to develop engineering tools to estimate the performance metrics will be described. The complementary connection between testing and modeling will be emphasized. Puncture performance metrics, which were estimated from other sources, will be compared for different tank car designs. These comparisons will be presented to interpret the metrics from a probabilistic point of view. In addition, sensitivity of the metrics to the operational and design factors will be examined qualitatively.

Commentary by Dr. Valentin Fuster
2016;():V001T02A004. doi:10.1115/JRC2016-5713.

This paper is the second in a two-part series on the puncture performance of railroad tank cars carrying hazardous materials in the event of an accident. Various metrics are often mentioned in the open literature to characterize the structural performance of tank cars under accident loading conditions. One of the consequences in terms of structural damage to the tank during accidents is puncture. This two-part series of papers focuses on four metrics to quantify the performance of tank cars against the threat of puncture: (1) speed, (2) force, (3) energy, and (4) conditional probability of release.

In Part I, generalized tank car impact scenarios were illustrated. Particular focus is given to the generalized shell impact scenario because performance-based requirements for shell puncture resistance are being considered by the regulatory agencies in United States and Canada. Definitions for the four performance metrics were given. Physical and mathematical relationships among these metrics were outlined. Strengths and limitations of these performance metrics were discussed.

In this paper (Part II), the multi-disciplinary approach to develop engineering tools to estimate the performance metrics is described. The complementary connection between testing and modeling is emphasized. Puncture performance metrics, which were estimated from other sources, are compared for different tank car designs. These comparisons are presented to interpret the metrics from a probabilistic point of view. In addition, sensitivity of the metrics to the operational and design factors is examined qualitatively.

Commentary by Dr. Valentin Fuster
2016;():V001T02A005. doi:10.1115/JRC2016-5727.

The Paper describes the past, present and future of high speed trains following the passing of the High Speed Ground Transportation Act fifty years ago. In the distant past, electrically-powered Metroliners ran between Washington and New York and Turbo Trains powered by gas turbines ran between Boston and New York on the Northeast Corridor. In the recent past, AEM-7 and HHP-8 electric locomotives supplied by EMD and Alstom respectively for operation with Amfleet railcars also ran on the Northeast Corridor. At the present time, electrically-powered Acela trainsets and ACS-64 electric locomotives supplied by Siemens are in service on the Northeast Corridor. Trains of Horizon and Amfleet railcars hauled by General Electric P-42-DC diesel locomotives operate between Chicago and St. Louis and Chicago and Detroit on the Mid West Regional Rail System. The future consists of two on-going projects that are being implemented, three projects that are in the planning stage and six projects that are in the concept phase. Features to be considered in the design of a high speed train system include: Design Standards and Regulations, Motive Power, Train Configuration, Maximum Axle Load, Dual-Mode Propulsion, Emergency Power, Double Deck Configuration, Jumbo Train Arrangement, Radial Trucks and Hi-Lo Bi-Track System.

Topics: Trains
Commentary by Dr. Valentin Fuster
2016;():V001T02A006. doi:10.1115/JRC2016-5752.

Research to facilitate industry efforts to safely use natural gas as a locomotive fuel is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. This research is being conducted cooperatively with the Association of American Railroads (AAR). The research results are being shared with the AAR’s Natural Gas Fuel Tender Technical Advisory Group (NGFT TAG), which includes AAR, Member Railroads, and FRA, with support from ARA and Volpe Center. The NGFT TAG is developing industry requirements, including crashworthiness requirements, for revenue-service natural gas fuel tenders.

Five accident scenarios have been drafted by the NGFT TAG: a train-to-train collision, a grade-crossing collision, rollover, shell impact, and head impact. Each scenario includes a description of the equipment, the impact conditions, and the prescribed outcome. Conceptually, these tender scenarios parallel the scenarios described in 49 CFR Part 229 Appendix E for locomotive crashworthiness.

The focus of the NGFT TAG discussions has expanded to include alternative static requirements. Conceptually, the tender static requirements parallel the requirements for locomotive crashworthiness in AAR S-580. Requirements in S-580 for locomotive structure include static load capacities, material properties, and material thicknesses. For conventionally-designed locomotives, meeting the static requirements of S-580 is accepted as meeting the dynamic requirements of Appendix E. The tender static requirements under development are intended to provide the same level of crashworthiness as the previously proposed dynamic requirements.

The primary advantage of static crashworthiness requirements is that compliance can be shown with classical closed-form engineering analyses. A disadvantage is that design features are presumed, such as the inclusion and location of collision posts in a conventional locomotive design. Design features are not presumed in dynamic crashworthiness requirements; however, compliance must be shown with a design-specific validated computer simulation model. So while dynamic requirements allow for a wide range of design approaches, showing compliance often requires extensive effort.

This paper focuses on technical information to help support development of alternative static requirements for the train-to-train collision scenario. The goal of the static requirements is to provide the same level of crashworthiness as the dynamic requirements under discussion by the NGFT TAG. Tender features capable of providing the desired level of performance are proposed. These features have been selected such that a tender with these features would be crashworthy-compatible with a wide range of new and existing locomotive structural designs.

Commentary by Dr. Valentin Fuster
2016;():V001T02A007. doi:10.1115/JRC2016-5817.

Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. The components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment.

Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of service loads. It has been shown analytically that push back coupler trigger loads exceed the service load capacity of conventional couplers and draft gears. Two sets of coupling tests are planned to demonstrate this, one with a locomotive equipped with conventional draft gear and coupler and another with a locomotive equipped with a pushback coupler. These tests allow for comparison of conventional with CEM-equipped locomotive measured performance during coupling. In addition to the coupling tests, car-to-car compatibility tests of equipped locomotives and a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests. In the coupling tests of conventional equipment, the maximum coupling speed for which there is no damage to either vehicle will be measured. A moving locomotive will be coupled to a standing cab car. The coupling speed for the first test will be 2 mph, the second test 4 mph, and the tests will continue with the speed incrementing by 2 mph until damage occurs to either vehicle.

This paper describes the test requirements and analysis predictions for the coupling tests of conventional equipment. The equipment to be tested, track conditions, test procedures, and measurements to be made are described. A one-dimensional model for predicting the longitudinal forces acting on the equipment and couplers has been developed, along with preliminary predictions for the conventional coupling tests. It is expected that damage will occur for coupling speeds between 6 and 8 mph.

Topics: Locomotives
Commentary by Dr. Valentin Fuster
2016;():V001T02A008. doi:10.1115/JRC2016-5819.

Since the adoption of 286,000 lb gross rail load (286K GRL) car service, an increase in wheel thermal damage and shelling has been observed. This is attributed to the increased braking horsepower in 286K GRL service as compared to the 263K GRL service environment. This study investigated possible designs and methods of braking that could lead to reduced heat input to the tread of freight car wheels in order to mitigate this damage and reduce its occurrence to a level closer to that seen with 263K GRL car service.

Fifteen potential concepts to lower the thermal input to wheels and/or accelerate heat removal from the tread were identified and evaluated using the following engineering categories: simplicity of design, maintenance requirements, weight considerations, material and manufacturing costs, controllability of braking effort, and market acceptability. Five final concepts — axle-mounted disc, cheek disc, wheel rim, axle-mounted drum, and high convection coating — were developed through preliminary design and thermal analysis to confirm their effectiveness in meeting the objectives.

Four concepts for alternative braking methods — axle-mounted disc brakes, cheek disc brakes, wheel rim clasp brakes, and axle-mounted drum brakes — were analyzed in considerable detail. Of the four concepts presented, the first three appear to be feasible and would be potential candidates for further detailed investigations/evaluation.

It is shown that as the demand on railway wheels to withstand increased mechanical and thermal loads grows, there are viable braking enhancements that can help manage the stress state in freight car wheels.

Commentary by Dr. Valentin Fuster
2016;():V001T02A009. doi:10.1115/JRC2016-5820.

The application of Laser technology for the top of the rail (TOR) lubricity detection is investigated. A laser-based sensor technology is proposed to detect, measure, and monitor the condition of the TOR lubricants. The optimum configuration of the laser sensor, suitable for effective lubricity measurements, is presented. In the proposed embodiment, the laser head is employed with its beam reflected off of the rail surface. Specular reflection of a lubricated rail is measured and compared with dry condition. A processing technique is developed based on the recorded reflection intensity dissimilarities to identify rail’s lubricity condition. A lubricated rail yields lower reflectivity value, as compared with a dry rail. The TOR detection system is mounted on a hand-operated cart for field testing. The field test results indicate that the proposed technique can successfully assess to what extent TOR lubricants are present on the rail, therefore serve to distinguish between various states of rail lubricity, from completely dry to completely saturated.

Topics: Lasers , Rails
Commentary by Dr. Valentin Fuster
2016;():V001T02A010. doi:10.1115/JRC2016-5821.

Top fittings devices on tank cars are subject to damage and failure under derailment conditions, potentially leading to the release of hazardous lading. This paper describes the conceptual development of an objective methodology for evaluating the risk of fittings protection failure and the potential reduction in that risk when mitigating strategies such as improved fittings protective structure are deployed. The methodology captures several key elements that affect fittings survival, including: the speed of derailment initiation, the impact velocity/force spectrum experienced by the fittings protective structure during the event, the strength/structural capacity of the protective structure, and the rigidity of the ground surface.

Detailed finite element modeling efforts were employed to capture derailment dynamics and corresponding impact velocity spectra, as well as the strength of multiple protective designs. Future work, including validation, is planned to extend the concept into a detailed methodology.

Commentary by Dr. Valentin Fuster
2016;():V001T02A011. doi:10.1115/JRC2016-5823.

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.

Commentary by Dr. Valentin Fuster
2016;():V001T02A012. doi:10.1115/JRC2016-5833.

The frequent incidences of Non-Accident Releases (NARs) of lading from tank cars have resulted in an increasing interest in transporting hazardous materials in total containment conditions (i.e., no pressure relief devices). However, the ability of tank cars to meet thermal protection requirements provided in the Code of Federal Regulations under conditions of total containment has not been established. The intent of this effort was to evaluate through a series of third-scale fire tests, the ability of tank cars to meet the thermal protection requirements under total containment conditions, with a particular focus on caustic ladings. A previous paper on this effort described the test design and planning effort associated with this research effort.

A series of seven fire tests were conducted using third scale tanks. The test fires simulated fully engulfing, hydrocarbon fueled, pool fire conditions. The initial tests were conducted with water as a lading under jacketed and non-jacketed conditions and also with different fill levels (98% full or 50% full). Additionally, two tests were conducted with the caustic, Sodium Hydroxide as the lading, each test with a different fill level. In general, the tanks with water were allowed to fail or reach near-failure conditions, whereas, the tests with the caustic lading were not allowed to proceed near failure for safety reasons. This paper describes the results and observations from the fire tests, and discusses the various factors that affected the fire test performance of the test tanks.

Review of results from the one-third scale tests, and subsequent scaling to full-scale suggest that a full-scale tank car filled with 50% NaOH solution is unlikely to meet the 100-minute survival requirement under conditions of total containment.

Commentary by Dr. Valentin Fuster
2016;():V001T02A013. doi:10.1115/JRC2016-5835.

Train carbody and truck structures are designed to exhibit primary natural frequency modes great enough to avoid unwanted resonant oscillations with normal track interactions. Critical bounce modes can be excited by typical track in the 2–4 Hz range. Trains are designed with first modes above this threshold. Historically, simplified approaches are employed to predict natural frequencies of the main truck and carbody train structures independently. Since the advent of high powered computing, more detailed finite element analysis (FEA) eigenvalue approaches have been used to more accurately predict natural frequency of structures. Still, the typical FEA approach uses simplified boundary conditions and partial models to determine natural frequencies of individual components, neglecting the interaction with other connected structures. In this paper, a detailed, holistic approach is presented for an entire Light Rail Vehicle (LRV). The analysis is performed on a fully detailed FEA model of the LRV, including trucks and suspension, carbody structures, non-structural mass, articulation, as well as intercar and truck-carbody connections. The model was developed for detailed crashworthiness investigations, which requires a high level of fidelity compared to what is typically required for static and modal analysis. Using the same model for multiple purposes speeds up development while also improving the accuracy of the analyses. In this paper, the modal analysis methodology developed is described. A case study is presented investigating the often neglected contribution of windows, cladding, and flooring on the overall carbody natural frequency.

Commentary by Dr. Valentin Fuster
2016;():V001T02A014. doi:10.1115/JRC2016-5844.

When a mechanical component of a railway vehicle experiences failure due to fatigue, it is necessary to determine whether it has been an isolated failure or it is a systematic failure that may affect the whole fleet. The present work presents the methodology to be followed for the application of on-track tests to determine the probability of fatigue failure. By simulating a normal commercial service in one or multiple conditions, the stress levels experienced by the component are recorded. These stress levels are combined and extrapolated in order to determine the typical global stress history that the component will experience during its operational life. From this stress history, the risk of fatigue failure can be estimated by means of the cumulative damage method also known as Miner’s rule. For this calculation the measured stress levels have to be compared with an S-N curve. The problem arises because the S-N curves presented in the standards correspond to stresses in the direction perpendicular or longitudinal to the weld. The peculiarities of on-track tests imply that the direction of principal stress may vary continuously and the maximum stress value may be present in specific points of the record with directions that do not represent the normal behaviour of the piece. Different forms of dealing with the projection of the rosettes have been analyzed, and the influence of these considerations on the damage calculation has been studied.

Topics: Fatigue failure , Risk
Commentary by Dr. Valentin Fuster

Signal and Train Control Engineering

2016;():V001T03A001. doi:10.1115/JRC2016-5750.

The overall performance of a Communication-Based Train Control (CBTC) system largely depends on the performance of its Data Communication Subsystem (DCS). The DCS network in almost all CBTC commercial system products marketed in the last decade utilizes radio communications in the open ISM bands (2.4 GHz or 5.8 GHz) to establish the bi-directional data link between the central/wayside and onboard segments. To ensure a stable and sound radio communication, a key question is the number of the wayside Access Points (APs) and locations of their antennas. Radio propagation modeling aims to provide an optimal and reasonably reliable solution to the cited question. The diffraction impact of sharp corners and edges in tunnels on the radio propagation process, however, has not been accounted for in majority of models. The purpose of the present research is to incorporate the effect of diffraction coupling due to sharp edges in tunnel sections which include geometrical discontinuities such as cross-junctions and L-bends through ray-mode conversion. The proposed modeling approach offers sufficient versatility to assimilate a variety of discontinuous geometries involving sharp edges in a tunnel environment. Numerical and empirical results suggest that the model provides an accurate tool for analyzing diffraction effects of tunnel discontinuities with sharp edges on the process of radio propagation.

Commentary by Dr. Valentin Fuster
2016;():V001T03A002. doi:10.1115/JRC2016-5784.

Positive Train Controller (PTC) is a communication based system designed to enforce PTC safety objectives for trains such as train-to-train collisions, train derailments, and ensure railroad worker safety. Existing PTC designs consider risks due to operational environment such as location of other trains, switches, and speed limits.

We propose to enhance PTC by using a multi-tiered cognitive radio network that considers multiple risks such as those due to bandwidth congestion, packet length limitations, propagation losses, detectable exploitation of Software Defined Radio vulnerabilities, and protocol vulnerabilities. Radios operating at PTC nodes (such as train, WIU and Base station) is equipped with a cognitive layer, which communicates with other nodes to create a cognitive radio network. The proposed network as a whole strives to provide spectrum management and security for the radio communication system, which can enhance the PTC functionality.

Each cognitive radio in our proposed network consists of multiple tiers. The upper tier consists of a master cognitive engine that holistically evaluates the operational risks of the network and acts to mitigate them using the lower tiers. The lower tier (immediate slave tier to the master) consists of sub cognitive engines for cryptographic operations and spectrum management. The traditional PTC protocol is implemented at a lower tier module that interface with the master Cognitive Engine (CE). The master-slave communications within one radio is implemented using middleware.

The proposed cognitive radio network can be modeled as a cyber-physical system by incorporating train movement dynamics, radio transmission characteristics and cryptographical computations, thereby constituting a distributed system of communicating hybrid automatons. This design enables us to verify safety and the security of the system using formal methods, which constitutes our ongoing work. We also discuss potential issues such as FRA mandated safety cases that needs to be addressed if the proposed features are to be added to the PTC systems.

Topics: Trains
Commentary by Dr. Valentin Fuster
2016;():V001T03A003. doi:10.1115/JRC2016-5801.

Integrating Global Navigation Satellite System (GNSS) into railway application has a great potential because of its various advantages, such as lower cost, less trackside equipment, higher positioning accuracy, easier maintenance and so on. Railway system is a safety-critical system that requires high reliability, safety and real-time performance, so GNSS technology must be tested, verified and validated in railway system before putting into practical applications. However, due to the unavoidable restrictions and inconvenience of the railway field conditions, these tests cannot be accomplished on site. On this basis, this paper has developed a GNSS-based train trajectory simulation system which can provide GNSS data simulation of multi-train trajectory in multiple scenarios in order to support the tests and research of GNSS-based railway application, especially GNSS-based train localisation system and GNSS-based train control system.

The GNSS-based train trajectory simulation system is based on the railway timetable (also called schedule), rolling stock information and digital track map. The paper firstly researches on the timetable that stores information of each train at each specified station, including arrival time, departure rime, track to be occupied, and connections to other trains. With the timetable simulation, the train’s trajectory can be generated using the information provided by the digital track map. The output trajectory data is mainly GGA sentence which is compliant with the National Marine Electronics Association (NMEA) 0183 standard. The paper also calculates the satellite visibility based on satellite ephemeris to simulate the number of visible satellites during the trajectory with changing time and space. All the information and data, such as timetable, speed/distance curve, distance/time curve, station track occupation state, can be visualized and updated in graphics and diagrams for better view. In addition, the train motion behavior of acceleration, cruising, coasting and braking can also be modelled in the system, as well as the driver’s behavior.

The GNSS-based train trajectory simulation system has been realized using C# programming language in Microsoft Visual Studio 2010. And the field data of Shanxi coal railway transportation company railroad is used in the system. The simulation system is tested and the experimental results show that the developed simulation system can perform the expected functions, and provided data source for GNSS-based train localisation system. In addition, this simulation system has a good performance in compatibility and scalability.

Commentary by Dr. Valentin Fuster

Planning and Development

2016;():V001T05A001. doi:10.1115/JRC2016-5841.

Freight transportation of goods and commodities is a necessity and is often a significant portion of the overall investment in industrial development, especially in the natural resource industry. The economic costs of developing infrastructure have long been factored into the project costs, but environmental or social impacts have received less attention. In addition, alternative transportation modes are rarely compared from both economic and environmental perspectives. This paper performs a Life Cycle Assessment (LCA) for truck-only, multimodal and rail transportation options to transport ore and concentrate. In this paper, LCA is performed in SimaPro for construction/manufacturing, operations, maintenance, and end of life phases to obtain the overall Global Warming Potential (GWP) in terms of kilogram equivalents of CO2 (kg CO2eq). After emissions from alternative options have been defined, the cost of each option can be investigated through Life Cycle Cost Analysis (LCCA) This paper also discusses the past work on LCCA and its application to transportation projects. The final part provides a methodology to convert the emission results from LCA for integration with the costs from LCCA.

Commentary by Dr. Valentin Fuster

Safety and Security

2016;():V001T06A001. doi:10.1115/JRC2016-5705.

Broken rails in freight and passenger revenue service occur due to single, or combinations of, faults or failures of various kinds. These may occur due to limitations inherent in the rail defect inspection process, track maintenance and renewal practices, and may also arise due to changes in operating conditions. The Government and the industry have developed regulations, standards and procedures to control these issues and reduce broken rail occurrences. This paper presents a broken rail fault tree as a way of visualizing the problem. It describes current controls and shows how they map onto the fault tree. Examples of recent broken rail derailments are used to illustrate the fault tree. Lessons learned are used to identify areas where further tightening of controls or the imposition of new controls may be required to further reduce the number of, and potentially eliminate, broken rails in service.

Topics: Rails
Commentary by Dr. Valentin Fuster
2016;():V001T06A002. doi:10.1115/JRC2016-5719.

Continuous Welded Rail (CWR) has been widely used in modern railway system for it provides smooth ride, higher freight speed, and less maintenance. A major safety concern with this type of structure is the absence of the expansion joints and the potential of buckling in hot weather. According to the FRA safety statistics, the track alignment irregularity is one of the leading factors responsible for the accidents and the most economic/environmental damages, among all the railway accident causes. However, the thermal stress measurement in the CWR for buckling prevention has been an unresolved problem in railroad maintenance.

In this study, a method is introduced to determine the in-situ thermal stress of the in-service CWR by using the Hole-Drilling method. The ASTM Hole-Drilling test procedure, as one type of stress relaxation methods, was originally developed to measure the in-plane residual stresses close to the specimen surfaces. The residual stresses are typically computed based on the relieved strains with the calibration coefficients. Inspired by the stress relaxation philosophy, an investigation on the thermal stress measurement of the CWR using the Hole-Drilling test procedure is conducted in this paper. First, the feasibility of using the Hole-Drilling method of the thermal stress measurement is examined via a 3-D finite element model. The stress relaxation computed from the Hole-Drilling test is compared with the applied uniaxial thermal stress. To facilitate the implementation on the CWR, a new set of calibration coefficients with finer depth increment is computed with a novel three-dimensional finite element model for more realistic simulation. The updated coefficients are experimentally validated with an aluminum column specimen under uniaxial load. For the experimental studies, a roadside prototype is developed and two sets of tests are carried out on free-to-expand rail tracks and on rails subjected to controlled thermal loads at UCSD Powell Laboratories. The relieved stresses are computed using the updated calibration coefficients, and a linear relationship between the axial and vertical residual stresses at the neutral axis is observed for both 136RE and 141RE rails. Furthermore, the in-situ thermal stresses are estimated with the residual stress compensation and the neutral temperatures are predicted according to linear thermal expansion theory. These tests illustrate that the determination of the thermal stresses by the Hole-Drilling method is in principle possible, once ways are developed to compensate for the residual stress relaxation. One such compensation is proposed in this paper. A statistical interpretation on the proposed method is also given to provide a reference for railroad applications.

Commentary by Dr. Valentin Fuster
2016;():V001T06A003. doi:10.1115/JRC2016-5726.

The New York City Transit (NYCT) Signal Modernization Program has been ongoing since the mid-1990s. The current phase of modernization involves the procurement of Solid State Interlocking (SSI) systems that are designed to replace relay-based interlockings. SSI procurement has necessitated significant adjustments to NYCT’s system deployment processes, most notably in the areas of design, implementation, test, maintenance, and safety certification. NYCT has successfully met the challenge of applying the updated deployment processes to multiple, concurrent system procurements.

The most fundamental change to the NYCT procurement approach required a shift from the traditional design-build model of acquisition for relay-based systems to a software-based development lifecycle for SSIs. The relay-based Interlocking systems’ design-build model has traditionally involved the realization of complex relay logic with well-known hardware components such as relays, trip-stops, signals and switch machines. The SSI systems’ software model however requires additional consideration of software and hardware development phases, such as designated in the V-lifecycle.

V-model phases include requirement, design, implementation, and test. For SSI systems, NYCT adopted a “double” V-Life cycle approach, one V for the supplier’s SSI hardware and software (executive) platform, and one V for the SSI application (site-specific field) logic. At NYCT, the first V is dedicated to the suppliers’ executive platform. Hardware and software comprising the supplier platform are verified to meet safety and performance requirements. Safety analyses such as Fault Tree Analysis, Failure Modes and Effects Analysis, Timing Analysis, and Hazard Analysis are generated by SSI suppliers. System Safety Concepts, e.g., Numerical Assurance, Checked Redundancy, Intrinsic Fail-Safety are also assessed. NYCT’s second V is dedicated to the application software, i.e., the site-specific relay-based logic, which is implemented as Boolean logic within the SSI. For the Booleans, the process of traditional circuit checking is supplemented by Model Checking, wherein NYCT General Safety Properties are used to verify the site-specific logic. Model Checking provides assurance that safety properties are met throughout the entire interlocking design, for every system state, and does not rely on a manual review process. This paper will focus on the benefits NYCT has realized as a result of adopting Model Checking as a requirement for safety certification, along with an overview of the NYCT SSI safety certification process.

Topics: Safety
Commentary by Dr. Valentin Fuster
2016;():V001T06A004. doi:10.1115/JRC2016-5729.

The railroad industry is challenged by the complexity and cost of performing the alternate route analysis as required by the Federal Railroad Administration’s (FRA) hazmat routing regulation. This is especially problematic to the regional and short line railroads for several reasons, including the unavailability of alternate routes and, as with the Class I railroads, it is a matter of cost and complexity of analysis. This research paper will look at developing a simplified risk model so as to reduce the cost and complexity of the analysis. This will be accomplished by, among other things, looking at the input parameters to the model for commonality so as to reduce the number (of input parameters) and look at three operating conditions for the analysis. They are: 1) the premise that there are available alternate routes, 2) that alternate routes may not be feasible operationally or economically and 3) that there are no alternate routes. This research and analysis will result in a model that is less complex and costly to run and address the concerns and challenges of the short line and regional railroads.

Commentary by Dr. Valentin Fuster
2016;():V001T06A005. doi:10.1115/JRC2016-5738.

Train accidents damage infrastructure and rolling stock, disrupt operations, and may result in casualties and environmental damage. While the majority of previous studies focused on the safety risks associated with train derailments or highway-rail grade crossing collisions, much less work has been undertaken to evaluate train collision risk. This paper develops a statistical risk analysis methodology for freight-train collisions in the United States between 2000 and 2014. Negative binomial regression models are developed to estimate the frequency of freight-train collisions as a function of year and traffic volume by accident cause. Train collision severity, measured by the average number of railcars derailed, varied with accident cause. Train collision risk, defined as the product of collision frequency and severity, is predicted for 2015 to 2017, based on the 2000 to 2014 safety trend. The statistical procedures developed in this paper can be adapted to various other types of consequences, such as damage costs or casualties. Ultimately, this paper and its sequent studies aim to provide the railroad industry with data analytic tools to discover useful information from historical accidents so as to make risk-informed safety decisions.

Commentary by Dr. Valentin Fuster
2016;():V001T06A006. doi:10.1115/JRC2016-5742.

This paper investigates the influence of rail age, annual traffic density, and inspection frequency on broken-rail-caused train derailment risk. First, we estimate the probability of a broken-rail-caused train derailment based on a sequence of stochastic processes including rail defect formation, growth, detection and the likelihood that a broken rail causes a derailment. In addition to derailment frequency, we also estimate derailment severity, which is measured by the average number of railcars derailed per train derailment, based on FRA-reportable train derailment data. The preliminary risk analysis model provides a quantitative approach to understand broken rail risk, and potentially aid in development of effective ways to mitigate derailment risk.

Topics: Risk analysis , Rails , Trains
Commentary by Dr. Valentin Fuster
2016;():V001T06A007. doi:10.1115/JRC2016-5743.

This paper develops an analytical framework for analyzing freight-train derailment risk due to track geometry failures. First, track geometry degradation is estimated based on a previous study that uses data from one Class I railroad. Then, the frequency of expected number of track-geometry-defect-caused derailment on mainlines is estimated. After that, the derailment severity (measured by the number of railcars derailed) can be predicted based on FRA-reportable track-geometry-failure-caused freight-train derailments. Due to data limitations, several simplifying assumptions were made to illustrate model structure and implementation procedure. The model can be adapted to specific carriers and locations for normative risk management of track geometry defects.

Commentary by Dr. Valentin Fuster
2016;():V001T06A008. doi:10.1115/JRC2016-5747.

The Federal Railroad Administration (FRA) has published a Notice of Proposed Rulemaking (NPRM) that will require passenger rail operators in the United States to develop a System Safety Program using a risk-based hazard management approach. Identified as 49 CFR, Part 270 System Safety Rule [1], the NPRM describes the basic requirements for a system safety program plan, including the need for a method for accepting risk. The NPRM does not, however, identify how the responsible party should actually go about managing risk. That is left up to the railways themselves.

In Europe, hazard management is applied in the railroad industry (including high-speed rail systems) under the regulatory authority of the European Union. European Commission Regulation 352/2009/EC [2] outlines a Common Safety Method (CSM) on Risk Evaluation and Assessment for Railways of the European Union, commonly known as the CSM Regulation and the heart of the railway safety program in Europe. The CSM Regulation includes the standard risk assessment process elements: identification of the hazards, corresponding risks, mitigation measures to reduce the risk, and the resulting safety requirements to be fulfilled by the system under assessment. What sets the CSM Regulation apart from other risk assessment programs is that it provides a methodology for determining when acceptable risk is achieved. The risk acceptability of the system under assessment is evaluated using one or more of the following risk acceptance principles:

a) The application of relevant codes of practice;

b) A comparison with similar systems (reference systems);

c) Explicit risk estimation.

In essence, the responsible party can accept risk that has either been regulated to an acceptable level by an authority having jurisdiction or a widely-accepted industry practice, or if the risk has been successfully addressed by a similar railway system through that railway’s engineering and operational controls. If neither of these cases applies the responsible party can estimate the risk and choose to accept it or not. A common approach, even internationally, is to develop an explicit risk estimation process based on the U.S. Department of Defense Military Standard 882E (MIL-STD-882E) [3]. Safety hazards are identified, analyzed for risk (severity and probability), and mitigations are progressively applied until a level of safety is achieved that is as low as reasonably practicable.

The California High-Speed Rail Authority (CHSRA) has adopted a risk-based hazard management program to achieve an acceptable level of safety for the design, construction, implementation and operation of the California High-Speed Rail System. CHSRA has deliberately used both domestic and international guidance and standards in the development of this program in an effort to apply the most up-to-date processes and philosophies, and to draw upon the impressive safety legacy of international high-speed railway operators.

This paper will describe the relevant regulations and guidance (both domestically and internationally), review the elements of a risk acceptance program based upon the CSM Regulation, and apply the program to a select set of hazards to demonstrate how appropriate mitigations can be determined and residual risk accepted. The paper will also identify potential future applications for the CSM Regulation here in the United States, and will challenge the reader to manage hazards using a risk-based approach that incorporates the basic framework of the CSM Regulation.

Topics: Safety , Risk
Commentary by Dr. Valentin Fuster
2016;():V001T06A009. doi:10.1115/JRC2016-5757.

The National Transportation Safety Board in the United States and the Transportation Safety Board of Canada publish reports about major railroad accidents. The text from these accident reports were analyzed using the text mining techniques of probabilistic topic modeling and k-means clustering to identify the recurring themes in major railroad accidents. The output from these analyses indicates that the railroad accidents can be successfully grouped into different topics. The output also suggests that recurring accident types are track defects, wheel defects, grade crossing accidents, and switching accidents. A major difference between the Canadian and U.S. reports is the finding that accidents related to bridges are found to be more prominent in the Canadian reports.

Commentary by Dr. Valentin Fuster
2016;():V001T06A010. doi:10.1115/JRC2016-5760.

In current rail inspection processes, following a detection of a suspected internal defect, an additional secondary detailed inspection is required to (1) confirm the presence of the flaw and (2) determine the severity of the flaw to allow for optimal post-detection rail maintenance planning. Current ultrasonic devices in this secondary inspection efforts heavily rely the expertise and experience of the test personnel’s judgement to confirm the rail flaw and to characterize the internal defect by analyzing reflected waveforms. To eliminate the uncertainties in this secondary inspection process and to provide the testing operators with better defect characterization such as the size and location of the flaw, a defect ultrasonic imaging device utilizing synthetic aperture focusing (SAF) techniques is proposed in this paper. These imaging techniques have been successfully demonstrated in medical imaging, providing quantitative characterization of internal components, allowing for a better prognosis. Ultimately, having a quantitative evaluation of the internal flaw can lead to an increase in the safety of train operations by preventing derailments. Thus, in this paper, a preliminary portable rail defect imaging concept is proposed by the University of California, San Diego, to provide three dimensional images of internal defects in the rail. The prototype reconstructs a three-dimensional volumetric image of the rail, utilizing multiple two-dimensional planar ultrasonic images. Improvements to the conventional tomographic imaging algorithms have been made by utilizing a mode-selective image reconstruction scheme that exploits the specific displacement field, respectively, of the longitudinal wave modes and the shear wave modes, both propagating simultaneously in the test volume. The specific mode structure is exploited by an adaptive weight assignment to the ultrasonic tomographic array. Such adaptive weighting forces the imaging array to look at a specific scan direction and better focus the imaging onto the actual flaw (ultrasound reflector). This preliminary study shows that the usages of the adaptive weights based on wave structure improves image dynamic range and spatial resolution, when compared to a conventional ultrasonic imaging technique such as Delay-And-Sum (DAS). Results will be shown both from numerical models and experimental tests of internal flaws in rails.

Commentary by Dr. Valentin Fuster
2016;():V001T06A011. doi:10.1115/JRC2016-5771.

The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is developing a system for high-speed and non-contact rail defect detection. A prototype using an ultrasonic air-coupled guided wave signal generation and air-coupled signal detection, paired with a real-time statistical analysis algorithm, has been realized. This system requires a specialized filtering approach based on electrical impedance matching due to the inherently poor signal-to-noise ratio of air-coupled ultrasonic measurements in rail steel. Various aspects of the prototype have been designed with the aid of numerical analyses. In particular, simulations of ultrasonic guided wave propagation in rails have been performed using a Local Interaction Simulation Approach (LISA) algorithm. The system’s operating parameters were selected based on Receiver Operating Characteristic (ROC) curves, which provide a quantitative manner to evaluate different detection performances based on the trade-off between detection rate and false positive rate. The prototype based on this technology was tested in October 2014 at the Transportation Technology Center (TTC) in Pueblo, Colorado, and again in November 2015 after incorporating changes based on lessons learned.

Topics: Inspection , Waves , Rails
Commentary by Dr. Valentin Fuster
2016;():V001T06A012. doi:10.1115/JRC2016-5772.

This paper identifies and explores possible safety implications of RoHS (Restriction of Hazardous Substances) compliance on railway equipment, with the purpose of presenting this topic for further consideration in North American industry standards, e.g. AREMA (American Railway Engineering and Maintenance-of-Way Association) guidelines. Of specific interest is the topic of tin whiskers, which are known to grow in electric circuits that are Lead free. Tin whiskers have the ability to bridge the gap between two vital signals in a circuit, creating the possibility for a potentially hazardous scenario to occur in a safety-critical system.

As rail transportation technologies become progressively more dependent on safety critical electronics that are RoHS compliant, the subject of tin whiskers merits its due consideration in the industry. There are verified incidents of tin whiskers having adverse impact in the automotive and aerospace industries; examples are provided in the paper. If precautionary measures are not respected, it is possible that a short circuit resulting from tin whiskers may lead to an undesirable incident in the rail industry also.

Research has shown that there are proven techniques which can inhibit tin whisker growth to an acceptable level. Mitigating measures and their effectiveness in deterring whisker growth are discussed in this paper.

Awareness is essential in prevention of a hazard. Railroads and Transit agencies that recognize hazards posed by metal whisker growth will be in a better position to evaluate the safety of RoHS compliant products provided by system integrators, who, in turn, must account for the issues presented in this paper in their internal quality processes. In due course, the safety implications of RoHS transitioning should be considered in an industry-wide guideline such as AREMA, laying the foundation for future RoHS compliant railway equipment that is safeguarded against safety concerns from tin whisker growth.

Commentary by Dr. Valentin Fuster
2016;():V001T06A013. doi:10.1115/JRC2016-5780.

Contrary to the declining railroad-highway crossing crashes over the past decade, the pedestrian-railroad interface has remained relatively unchanged. While engineering solutions and law enforcement have been tried, little is known about their effectiveness on the pedestrian mindset and psychology.

One of the main reason for crashes of this type is that pedestrians tend to be restless while waiting at railroad crossings. This can lead to pedestrians performing irrational acts such as attempting to walk across a crossing before a train arrives. Earlier, trains traveled at slower speeds which pedestrians could react to easily and trains had less freight so it needed less braking distance and thus it was easier to control them. There are many factors with the potential to improve pedestrian safety at railroad crossings.

In this paper the current safety norms for railroad crossings existing across in more than 40 major cities in US were analyzed to determine the existing safety standards for pedestrians at railroad grade crossings. State departments of transportation (DOTs) were contacted, along with professionals in public and private sector involved in safety at railroad crossing and ask them what according to them is a high risk railroad grade crossings in their area, safety practices that are common in their area, various threats to Safety implementation and then analyze these crossing for the types, safety signs and equipment present at them.

Topics: Safety , Railroads
Commentary by Dr. Valentin Fuster
2016;():V001T06A014. doi:10.1115/JRC2016-5786.

A comprehensive study is needed to address the human behavior at railroad grade crossings. Human behavior at different signs changes and it may lead to crashes. No guidance is provided in the recommendations provided by Manual on Uniform Traffic Control Devices where and when different type of signs and different combination of signs are appropriate. Crashes occur mostly when the drivers try to go through the gate or around the gate when a train is approaching. Drivers come to a complete stop at stop signs and then proceed only if a train is not coming, this may lead to a crash when they cannot accelerate in time to cross the tracks. Yield sign may have better results in this case. Cross-buck signs are same as the yield sign where drivers should slow down, look for the train and then proceed. However, people may tend to proceed without yielding as it is not as common of a sign. Hence we can say driver behavior at specific sign is important for the recommendation or the guideline to install a sign. Adopting a common sign at all grade crossings could provide enhanced consistency and reduce crashes. A literature review was done on human behavior at grade crossings and the crash rate at different types of signs. Driver behavior at the time of the crash for 15 states was studied from the Federal Railroad Administration data by reviewing detailed reasons for every crash. Driver behavior at different types of signs at the time of each crash was studied from the reviewed data and the literature review. Driver behavior at different signs was summarized.

Topics: Railroads
Commentary by Dr. Valentin Fuster
2016;():V001T06A015. doi:10.1115/JRC2016-5799.

While experience is often the best teacher, learning from precursors is much less painful. The aviation and health care industries have greatly benefited from proactively analyzing and developing measures to address sentinel events and learning from various data sources. Such reflective learning is typical of High Reliability Organizations (HROs) with strong learning cultures. As technology like Positive Train Control increasingly integrates into the rail industry, the resulting data they inevitably produce can provide a wealth of knowledge that can greatly improve safety if the data streams are well managed and not blindly mined. For example, simulators generate data while locomotive engineers use them. During training, such data can indicate weak points where the engineer can improve. Examining such data over multiple engineers can establish general areas of strengths and weaknesses among trainees where instructors can place more or less focus and develop better overall training options. Such data could potentially be used to improve cab design and establish how trains and cab care would operate along a given rail line. This paper will explore the use of data streams from various sources, including those currently used like injury reports, emerging ones like simulation training evaluations and data logs to develop better safety cultures within the rail industry.

Topics: Safety , Rails
Commentary by Dr. Valentin Fuster
2016;():V001T06A016. doi:10.1115/JRC2016-5803.

Safety as the key quality property among RAMS (reliability, availability, maintainability, and safety) demonstrates the most stringent performance in correspondence with the safety requirements and performance standards like EN 50126. Meanwhile, GNSS (Global Navigation Satellite Systems) are penetrating the railway now widely in non-safety related applications as passenger information, fleet management, etc. GNSS also have great potential for safety-related applications in railway such as the train location determination function, which the safety performance needs to be assured through hazard analysis and risk assessment process.

The train location determination by satellite-based localization system is elevating the train control to the next level. The European Train Control System (ETCS) has being trying to implementing Level 3, the Chinese Train Control System (CTCS) has been implementing CTCS Level 3 low cost especially for secondary lines, and the U.S. is implementing train control systems under Positive Train Control (PTC) requirements. The train control system needs GNSS to provide more accurate location information of trains, more flexible and condensed trains on tracks with the consistency of still keeping the current safety level or even improve safety.

Some researchers are trying to understand the performance of GNSS (GPS / EGNOS / Beidou) for railway applications from the fundamental accuracy level. A satellite-based train localization unit (SaLuT) as the entity to perform the train location determination function is to bring the GNSS accuracy evaluation up to safety integrity according to the safety requirements and standards for risk assessment. One of the key consequential result derived from the train location is the adequate safety margin. The safety margin, which can also be called as “safe braking distance”, is a margin indicated to rail traffic that would allow the train to stop with the application of normal service braking. The safety margin estimation quality and the risk of the safety margin shows the hazard rate for the safety margin estimation function performed by the designed localization unit SaLuT.

This paper discusses the safety margin estimation method considering both GNSS accuracy and integrity assessment aspects of SaLuT, in accordance of the settled safety requirements of location determination function. To analyze the hazard of the safety margin estimation, a formal method is applied to model the SaLuT behavior and functions. The formal method based on stochastic Petri net enables the modeling process to include the GNSS receiver collected real data on the test track into it. The safety margin estimation method together with the risk assessment method using the real data can generate quantitative indicators to represent the localization function and safety margin estimation quality. The data used for the analysis is collected in the Qinghai-Tibet railway line from Golmud station to Ganlong station by SaLuT installed on a locomotive along the track. With the stochastic Petri net model and the systematic equation using the real collected data to estimate the safety margin based on the GNSS technologies, the SaLuT can be validated and verified for its hazard rates, which provides information for the safety cases in order to meet the industrial normative requirements.

Commentary by Dr. Valentin Fuster
2016;():V001T06A017. doi:10.1115/JRC2016-5811.

Twenty-three commuter and inter-city passenger train accidents, which occurred over the past twenty years, have been analyzed. The analysis has assessed the potential effectiveness of various injury mitigation strategies. The strategies with the greatest potential to increase passenger safety are interior occupant protection, coupler integrity, end structure integrity, side structure integrity, and glazing system integrity. We recommend that these strategies be researched further.

Three types of accidents were analyzed: train-to-train collisions, derailments, and grade-crossing collisions. Train-to-train collisions include the commuter train-freight train collision in Chatsworth, California on September 12, 2008. In Chatsworth a commuter train collided with a freight train at a closing speed of ∼80 mph, fatally injuring twenty-five people and injuring more than 100 others. Derailments include the commuter train derailment in Spuyten Duyvil, New York on December 1, 2013, fatally injuring four people and injuring more than fifty others. Grade-crossing accidents include the commuter-SUV collision in Valhalla, New York on February 3, 2015, which resulted in six fatally injured people, including the SUV driver, and thirteen severely injured people.

Four categories of mitigation strategies were considered: train crashworthiness, wayside structure crashworthiness, fire safety, and emergency preparedness. Within each of these categories are equipment features, which may potentially be modified to further mitigate injuries. The features are simple noun phrases, e.g., “floor strength,” implying that the floor strength should be increased. Train crashworthiness includes features such as end strength, floor strength, coupler separation, and numerous others. Wayside structure crashworthiness includes features such as frangible catenary poles and third rail end caps. Fire safety includes train interior and train exterior features for minimizing the potential for fire and for reducing the rate at which fire might spread. Emergency preparedness includes features for emergency egress, access, lighting, signage, and on-board equipment, such as fire extinguishers.

Overall, rail passenger travel has a high level of safety, and passenger train accidents are rare events. The numbers are low for expected casualties per passenger-mile and casualties per passenger-trip. A high level of safety, however, does not mean efforts to improve it should cease. But it does mean that crashes are rare events. Rare events in complex systems are notoriously difficult to analyze with confidence. There are too few accidents to provide the data needed for even a moderate degree of mathematical confidence in statistical analysis. Analyses of similar data in medical and scientific fields have been shown to be prone to the biases of the researchers, sometimes in subtle and difficult-to-detect ways. As a means of coping with the sparse data and potential biases, the goal has been to evaluate the accidents transparently and comprehensively. This approach allows a wide audience to understand how injuries and fatalities occur in passenger train accidents and, most importantly, allows us to prioritize mitigation strategies for research.

Commentary by Dr. Valentin Fuster
2016;():V001T06A018. doi:10.1115/JRC2016-5816.

In the railroad industry, monitoring the condition of key components such as bearings and wheels is vital to ensure the safe transport of goods and commodities. Bearing seizures are amongst the most dangerous types of failures experienced by trains because they occur unexpectedly and may lead to costly derailments. Current bearing health monitoring techniques include tracking the temperature and acoustic emissions given by the bearings. Although temperature histories of railroad tapered roller bearings are readily available, the literature does not provide information relating the temperature profiles to the severity of the bearing defect. The study presented here investigates the correlation between temperature profiles and bearing defect severity measured by the size of spalls present on bearing outer (cup) and inner (cone) rings. The temperature data used for this study was acquired from defective and healthy bearings that were run at various operating load and speed conditions. The data presented here provides the railroad industry with a greater understanding of the thermal behavior of defective bearings, which can be used to assess the future needs of bearing condition monitoring systems.

Commentary by Dr. Valentin Fuster
2016;():V001T06A019. doi:10.1115/JRC2016-5827.

This paper investigates the plausibility of a novel in-vehicle auditory alert system to warn drivers of the presence of railroad crossings. Train-Vehicle collisions at highway-rail grade crossings continue to be a major issue despite improvements over the past several decades. In 2014 there were 2,286 highway-rail incidents leading to 852 injuries and 269 fatalities. This marked the first time in the past decade that incident rates increased from the previous year. To prevent the overall trend in safety improvement from plateauing, interest is shifting towards novel warning devices that can be applied to all crossings at minimal cost. These novel warnings are intended to complement but not replace the primary visual warnings that are already in place at both active and passive crossings. Few in-vehicle warning systems have been described and tested in the rail safety literature. The ones that have been described only manipulate the modality or reliability of the warning message, and pay little attention to message content, timing of presentation, mappings between crossing events and warning logic, and driver habituation associated with long term use. To this end, a line of research has been being carried out to design in-vehicle auditory alerts and measure subjective preference and driver behavior in response to in-vehicle auditory alerts. The first study included a subjective evaluation of potential auditory cues. Cues rated as most effective and appropriate were included in the design of prototype systems in the follow up study. The second study will measure compliance rates in a driving simulator with and without in-vehicle auditory alerts. The results of first study and the study design for the second study are discussed.

Topics: Vehicles , Highways , Rails
Commentary by Dr. Valentin Fuster
2016;():V001T06A020. doi:10.1115/JRC2016-5832.

Critical derailment incidents associated with crude oil and ethanol transport have led to a renewed focus on improving the performance of tank cars against the potential for puncture under derailment conditions. Proposed strategies for improving puncture performance have included design changes to tank cars as well as operational considerations, such as reduced speeds and upgraded brake systems. In a prior paper on this topic, the authors conceptualized a novel and objective methodology for quantifying and characterizing the reductions in risk that result from changes to tank car design or to the tank car operating environment.

This paper describes an extension of that effort to include additional derailment cases, additional operating speeds, considerations for alternate train configurations, such as Distributed Power (DP) and Electrically Controlled Pneumatic (ECP) brakes, as well as options for component level studies. In essence, the developed methodology considers key elements that are relevant to tank car derailment performance and combines these elements into a consistent probabilistic framework to estimate the relative merit of proposed mitigation strategies. The relevant elements considered include variations in the derailment scenarios, chaotic derailment dynamics, the distribution of impact loads and impactor sizes, various operating speeds, brake system differences, and variations in tank car design. The paper also provides an overview of the validation efforts which suggest that the gross dynamics of a tank car train derailment, and the resulting puncture performance of the tank cars, are captured well by this methodology.

Commentary by Dr. Valentin Fuster
2016;():V001T06A021. doi:10.1115/JRC2016-5836.

Accident investigation reports and related documents provide a wealth of information for rail professionals, even across different modes of transportation. This information can be used to improve operations, maintenance, safety, training, and emergency response. It can also guide the procurement and design of new equipment and infrastructure. At the same time, the historical nature of the information as well as the volume available and variety of sources can be a barrier to effective use. This paper will provide an introduction to some of the sources of transportation accident data and reports, including the variety of topic-specific information and special reports that are available. The discussion will include less-considered sources of accident information including foreign transportation safety boards as well as specialized federal and state agencies. Accidents that were investigated and reported on by more than one organization are also discussed.

Commentary by Dr. Valentin Fuster
2016;():V001T06A022. doi:10.1115/JRC2016-5838.

A 1969 collision of two Penn Central train resulted in four fatalities and forty-five injuries. This accident could have been prevented, had some type of train control system been in place. After this accident, the National Transportation Safety Board (NTSB) asked the Federal Railroad Administration (FRA) to study the feasibility of requiring railroads to install some type of automatic train control system that would prevent human-factor caused accidents. Over the next almost four decades, a number of additional accidents occurred, culminating in the January, 2005 Graniteville Norfolk-Southern accident and the September, 2008 Metrolink Chatsworth accident.

A little more than one month after the Metrolink accident, Congress passed the Rail Safety Improvement Act, which requires Positive Train Control (PTC). To better explain the positive train control requirements, this paper traces each to a detailed case study. Four different accidents are studied, each being an example of one of the four, core positive train control requirements. Included in the case study is a discussion about how positive train control would have prevented the accident, had it been present.

This provides positive train control implementers and other railroad professionals with a better understanding of the factors that have caused or contributed to the cause of the positive train control preventable accidents studied.

Topics: Accidents
Commentary by Dr. Valentin Fuster

Energy Efficiency and Sustainability

2016;():V001T07A001. doi:10.1115/JRC2016-5721.

Due to the increasing scarcity of fossil fuels and the climate change, the importance of energy efficiency is increasing. This importance is major especially in areas where the energy consumption is high. Rail transport depicts such an area. The highest proportion of energy consumed in the railway is the so called traction energy. This energy is required for the train run. In the timetable, allowances leave a margin for the driving style of train run. By the selective use of strategies that change the driving style, it is possible to exploit these allowances and reduce the traction energy consumption. The first objective of this study deals with the development of algorithms for energy-saving driving style.

First, the necessary input variables of the algorithms based on the literature research and the formulas of train dynamics were determined. Then the algorithms were developed to create different energy-saving driving styles, resulting choose the best result which should be shown as a driving recommendation. The developed algorithms were used in an application example in order to calculate the potential of energy-savings. The example should represent the influence of the input variables for a comparison of different situations. At last the acceptance of the determined driving strategies in practice was investigated. By implementing the design thinking method it was identified that driver advisory systems and training programs are necessary to facilitate energy-saving driving in practice.

Commentary by Dr. Valentin Fuster
2016;():V001T07A002. doi:10.1115/JRC2016-5777.

The interest of this work is to develop a control strategy to most effectively manage the power split between the energy storage system (ESS) and the diesel generator of a hybrid locomotive. The overall goal is to minimize fuel consumption of the diesel engine, while maximizing battery life of the onboard ESS. This problem proves to be complex due to the conflicting cost functions of fuel economy and battery state-of-health (SOH)[1]. In other words, during a typical drive cycle, fuel consumption is minimized by placing high loads upon the battery while minimizing negative effects on SOH requires more specific loading characteristics of the ESS for the same drive cycle. This work highlights the development of several power split control strategies for effective power management of a hybrid locomotive. The progression from a strict rule-based (RB) control strategy to an equivalent consumption minimization strategy (ECMS) is realized through simulation. Likewise, the advantage of Model Predictive Control (FLC) is also shown in simulation.

Commentary by Dr. Valentin Fuster
2016;():V001T07A003. doi:10.1115/JRC2016-5824.

The vast majority of railway construction and maintenance machines is powered by compression-ignition combustion engines. The tendency of introducing stringent standard emission regulations for these prime movers, e.g. TIER 4, forces the migration toward downsized units. Additionally, the high price reached by diesel fuel in the last decades demands reductions of the machines’ energy consumption in order to maintain the customers’ operating costs competitive. Both targets can be achieved by implementing efficient hybrid hydraulic displacement-controlled architectures that reduce pollutants emissions and benefit fuel saving without affecting the system’s productivity. For these reasons, this research paper aims at investigating the potentials of a series-parallel hybrid architecture grounded on secondary controlled hydraulic motors and potentially suitable for any railway construction and maintenance machinery. The results demonstrate that the rated engine power can be reduced by at least 35% in the reference application by applying such a propulsion system. Specifically, the high-fidelity multi-domain dynamic model created for sizing, analyzing, and controlling this displacement-controlled layout is addressed. Special focus is dedicated to the rail/wheel interface confirming that the proposed control strategy maintain the slip/spin of the wheels within the desired limits.

Commentary by Dr. Valentin Fuster
2016;():V001T07A004. doi:10.1115/JRC2016-5830.

As railroads and local industries served by rail seek to reduce emissions and improve fuel efficiency, new technologies are being developed to serve this market. Contrary to the minimal competitive options available over the last several decades, new companies are now emerging with a variety of locomotive designs aimed at low emissions and low horsepower solutions. Some technologies involve alternative fuels (e.g. natural gas, bio-diesel, battery power, etc.), while others incorporate very low horsepower diesel engines (400hp–1000hp) in order to meet the Tier 4 regulations set by the Environmental Protection Agency (EPA). Yet another option available to railroads and local industries is the mobile railcar mover. Typically used within railroad yard limits or on industry tracks, yard and industrial switchers and mobile railcar movers travel short distances, but must be capable of moving large loads. Subject to high forces when moving cars, these technologies must be both resilient (requiring minimal maintenance) and safe (not subject to derailment or loss of control). As the current market for yard and industrial switchers continues to expand, both railroads and local industries served by rail are placing greater emphases on the environmental and economic benefits of the emerging technologies. This paper aims to analyze the current yard and industrial switcher market and draw conclusions based on emissions data and lifecycle costs. Industrial switchers are compared with yard switchers and mobile railcar movers. Although industrial switchers are more limited in horsepower and operational versatility than yard switchers, many of the daily operations between the two are similar. Mobile railcar movers (e.g. Trackmobile® and Rail King®) offer lower initial costs as well as the versatility of both on-track and off-track movement. However, they may require additional maintenance and offer reduced tractive effort compared to locomotive technologies. As the demands on railroad yard and industry operations grow increasingly complex due to environmental regulations and economic demands, these new technologies have the potential to increase competition in the marketplace and offer improved engineering solutions. By developing a hierarchy of key requirements of yard or industry switchers, this paper provides a framework for identifying the best options available to a railroad or local industries. The scope of this paper will include a review of all options available, but will place a greater emphasis on technologies that are commercially available for wide distribution. By sampling and analyzing the current industrial market, much insight can be gained into daily operational requirements and challenges faced by this sector of the industry.

Commentary by Dr. Valentin Fuster

Urban Passenger Rail Transport

2016;():V001T08A001. doi:10.1115/JRC2016-5775.

Application of active suspension on passenger vehicles has engaged many vehicle dynamics specialists in recent years. The technology can be used for different purposes including improving comfort, stability or wear behavior. Despite these benefits, industries do not yet find these technologies attractive enough. One reason is that the achieved benefits do not pay back for itself since the vehicle will become more expensive. Therefore, more steps should be taken to make active suspension attractive. One such a step can be using active suspension for resolving classical limitations in rail vehicle dynamics. An example of this is a non-bogie rail vehicle with two axles. One of the problems associated with these vehicles is their short axle distance limiting the length of the vehicle. The short axle distance is partly for limiting wheel-rail wear. This paper describes how to reduce wheel wear through achieving better wheelset steering in curves so that longer axle distances can be allowed. Wheelset steering is performed by H control strategy.

Commentary by Dr. Valentin Fuster
2016;():V001T08A002. doi:10.1115/JRC2016-5778.

Ridership on Midwest passenger rail lines has been steadily increasing over the past two decades. Between 2005 and 2014, there has been a growth of more than 65 percent, much higher than the national average (approximately 30 percent for the same years). Nevertheless, a number of lines have discontinued their services or are in danger of discontinuance. For example, Kentucky Cardinal, operating between Chicago, Illinois and Louisville, Kentucky was discontinued in 2003, and the Three Rivers train, operating between Chicago, Illinois and New York, New York was discontinued in 2005. The Hoosier State train running between Indianapolis, Indiana and Chicago, Illinois would have faced the same fate recently, if not for the financial support that the state and communities have been providing since 2013. As of October 1, 2013, the State of Indiana, local communities, and Amtrak reached an agreement to support the Hoosier State line for the following fiscal year (2013–2014), and the agreement has continued ever since. In the meantime, the Indiana Department of Transportation (INDOT) was the first nationally to announce a Request for Proposals to seek competing solutions from independent providers, as allowed by the Passenger Rail Investment and Improvement Act of 2008 (PRIIA), in order to obtain private-sector competitive bids for the operation of the Hoosier State train. Recently, after many unfruitful attempts and many obstacles, INDOT reached an agreement with Iowa Pacific Holdings. The company has been providing the locomotives for the line since August 2015, and collaborates with Amtrak to keep the train in service, with a shared vision to increase service frequency, improve speed and maintain a reliable schedule, and provide better on-board amenities. However, to ensure the financial viability of the system and support any improvement or expansion, an increase in ridership is necessary. To achieve this, it is essential that we understand the opinions of Indiana residents, passengers of the Hoosier State train, and advocates of the line towards passenger rail.

This paper presents the results of a survey that was conducted on board the Hoosier State train to solicit information pertaining to the perceived ease of use and usefulness of the passenger rail services, riders’ opinions, and other factors that might affect behavior toward passenger rail transportation, as well as factors that affect an individual’s mode choice in general, such as habitual automobile behavior, or external impedance factors like schedule and route restrictions. The survey was endorsed by INDOT and approved by Amtrak and Iowa Pacific Holdings. In addition, this paper presents how opinions toward passenger rail differ among different groups based on socioeconomic and demographic characteristics, familiarity with passenger rail transportation in general and the Hoosier State train specifically, and usage. Furthermore, in order to prioritize service improvements that can foster an increase in the Hoosier State ridership, this paper explores mode choice decisions through the use of a multi-attribute attitude model.

The results of this paper can guide policy and planning decision making that aims to foster an increase in passenger rail ridership through a mode shift from personal automobiles and competing mass transportation systems, such as airlines and intercity buses.

Topics: Rails , Trains
Commentary by Dr. Valentin Fuster

Electrification

2016;():V001T09A001. doi:10.1115/JRC2016-5709.

Stray current corrosion will occur at each point where the current transfers from a metallic conductor (such as structural reinforcement) to the electrolyte (i.e, the soil or concrete). Hence stray current leakage can cause corrosion damage to the rails, railway metallic structures, utility pipelines in the soil and any other low resistance metal buried in the vicinity. The hazard posed by stray current is not confined to structures that are within the vicinity of the railway. Stray currents can flow considerable distances (particularly in soils of low resistivity) and can therefore cause corrosion damage to what may be considered remote structures. This paper presents the importance of corrosion control on utility pipes and then presents and evaluates potential metal loss using arithmetic equations and basic modeling.

Topics: Corrosion , Pipes
Commentary by Dr. Valentin Fuster
2016;():V001T09A002. doi:10.1115/JRC2016-5810.

This paper presents the development of a qualitative and quantitative assessment of the resistance to ground for the electrically continuous negative rails of a medium capacity transit line of the Taipei Rapid Transit System. Using synchronous potential measurements at three stations we examine potential profiles to locate potential rail sections with low resistance to ground qualitatively. Also the voltage sag values are used to quantitatively calculate rail-to-ground resistance per unit length. The approach presented in this paper requires only voltage measurements with the traction current as the energization source. Thus, this approach can be performed as a routine maintenance procedure to obtain rail-to-ground resistance values from a system-wide point of view.

Commentary by Dr. Valentin Fuster

Vehicle Track Interaction

2016;():V001T10A001. doi:10.1115/JRC2016-5722.

Three-point contact occurs in curving and transfer of a wheelset over switches and turnouts. In this study, an approach is presented that enforces three-point contact between a wheelset and a rail. This is accomplished by placing the wheelset over the track by setting the wheelset position parameters. Then, the location of all common normal are computed. Next, three common normal with shortest length are used to set up the non-penetrating constraint equations in track coordinate system. This led to nine algebraic equations whose Jacobean can be represented by block matrices. A Newton iterate based on these block matrices are used to compute the location of the three contact points. Several numerical examples are presented to verify the accuracy of the approach.

Topics: Rails , Wheelsets
Commentary by Dr. Valentin Fuster
2016;():V001T10A002. doi:10.1115/JRC2016-5734.

The discontinuity between rail ends at a joint creates dynamic wheel-rail forces (i.e. high impact forces and wheel unloading) that can result in a range of problems including wear, deterioration, and early failure of the track structure, its components, and passing equipment. The response and magnitude of the dynamic wheel-rail forces generated at joints depend upon the form of the discontinuity (e.g. battered rail ends, ramps, gaps, mismatches, etc.) and the support condition. Joints with battered rail ends, which result from degradation due to repeated impact loading, have been extensively analyzed using closed form expressions developed by Jenkins [1] to estimate P1 and P2 impact forces. While appropriate for analyzing joints with battered rail ends, P1 and P2 forces are not directly applicable to other forms of discontinuity at joints such as mismatches in which the rail ends are offset vertically when installed.

Under certain circumstances, railroads are introducing ramps (by grinding or welding) to reduce the mismatch discontinuity and produce a smoother transition in order to mitigate these dynamic wheel-rail forces. In this paper, analyses are conducted to estimate dynamic wheel-rail forces at joints having ramps and mismatches of various sizes using simplified models along with detailed NUCARS models for comparative purposes. The Federal Railroad Administration (FRA) Track Safety Standards (49 CFR Part213) [2] limit the maximum mismatch at joints by Track Class in order to minimize the impact forces which deteriorate the track structure, its components, and equipment, and may ultimately lead to derailment. Parametric studies are conducted to examine the effects of ramp length, direction of travel, mismatch height, and equipment speed (track class). Plots of primary shock-response-spectrum (maximum impact force on the ramp), residual shock-response-spectrum (maximum impact force after the ramp), and minimum wheel force (i.e. wheel unloading) are developed to provide guidelines on ramp length (H-rule) in order to control the maximum force by track class.

Topics: Rails , Wheels
Commentary by Dr. Valentin Fuster
2016;():V001T10A003. doi:10.1115/JRC2016-5770.

The railroad tie is an important component in track structure which provides lateral resistance, continuous support for rail and transfers the train load to ballast. The movement of the tie subject to train loading is usually considered as a vertical motion. However, it is believed that the real-world tie movement is not only translational but rotational due to moving load. In order to investigate the real movement of railroad ties, a train-track interaction computer program was used. The computer program includes a vehicle dynamics model and 3-D Finite Element (FE) track model. The wheel-rail contact forces were obtained from the vehicle dynamics model, and then input to FE track model to simulate the tie movement. Furthermore, the field validation was conducted at Northeast Corridor (NEC) in United States. The measuring units were mounted on the edge of ties to record the angle and acceleration change of the tie in three orthogonal directions. The data analysis showed that the field-measured translational and rotational movement of ties have good agreement with the simulation results. It is concluded that the tie movement is not only up-and-down motion under moving train load, but also comprises rotation and lateral movements.

Commentary by Dr. Valentin Fuster
2016;():V001T10A004. doi:10.1115/JRC2016-5785.

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.

Commentary by Dr. Valentin Fuster
2016;():V001T10A005. doi:10.1115/JRC2016-5813.

This study develops a detailed multi-body dynamic model of the Virginia Tech Roller Rig (VTRR) using multi body simulation software package SIMPACK. The Virginia Tech Roller Rig, a single-wheel roller rig with vertical plane roller configuration, is a state of the art testing fixture for experimental investigation of wheel-rail contact mechanics and dynamics. In order to have a better understanding of the dynamics at the contact, dynamic behavior and interaction of various components and subsystems of the rig need to be understood. In addition, it is essential to make sure that the measurements are only due to particular subject of study and not any intermittent source of disturbance. Any unwanted vibration at the contact needs to be compensated in the data measurements. To this end, a fully detailed model of the rig including all the components is developed in SIMPACK. The coupled multibody dynamic model represents all the major components of the rig and their interactions. The multibody dynamic model is employed for conducting noise, vibration, harshness (NVH) analysis of the rig. An Eigenvalue analysis provides the modal frequencies and mode shapes of the system. The modal analysis predicts the first natural frequency of the rig to be approximately 70 Hz, providing a relatively high bandwidth for evaluating the dynamics at the wheel-rail interface. Only dynamic that could have higher frequencies than the rig’s bandwidth is wheel-rail squeal. The model is also used to evaluate the performance of the contact force measurement system designed for the rig. The results show that the contact forces can be estimated precisely using the force measurement system.

Commentary by Dr. Valentin Fuster
2016;():V001T10A006. doi:10.1115/JRC2016-5815.

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.

Commentary by Dr. Valentin Fuster
2016;():V001T10A007. doi:10.1115/JRC2016-5826.

The primary purpose of this study is to use a nano-scale optical surface profilometer to assess the feasibility of such instruments in measuring localized friction coefficient on railways, beyond what can be commonly measured by tribometers used by the railroad industry. One of the important aspects of moving freight and passengers on railways is the ability to manage and control the friction between the rails and wheels. Creating a general friction model is a challenging task because friction is influenced by various factors such as surface metrology, properties of materials in contact, surface contamination, flash temperature, normal load, sliding velocity, surface deformation, inter-surface adhesion, etc. With an increase in the number of influencing factors, the complexity of the friction model also increases. Therefore, reliable prediction of the friction, both theoretically and empirically, is sensitive to how the model parameters are measured. In this study, the surface characteristics of four rail sections are measured at 20 microns over a rectangular area using a portable Nanovea JR25 optical surface profilometer and the results were studied using various statistical procedures and Fractal theory. Furthermore, a 2D rectangular area was measured in this study because 1D height profile doesn’t capture all the necessary statistical properties of the surface. For surface roughness characterization, the 3D parameters such as root-mean-square (RMS) height, skewness, kurtosis and other important parameters are obtained according to ISO 25178 standard. To verify the statistical results and fractal analysis, a British Pendulum Skid Resistance Tester is used to measure the average sliding coefficients of friction based on several experiments over a 5 cm contact length for the four rail sections selected for the tests. The results indicate that rail surfaces with lower fractal dimension number have a lower friction. The larger fractal dimension number appears to be directly proportional to larger microtexture features, which potentially increase friction.

Commentary by Dr. Valentin Fuster

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