Safety and Security Analysis for Movable Railroad Bridges

Movable railroad bridges, consisting of lift, bascule, or swing bridges have been used by American rail tracks that cross usable waterways for over a century. Although custom made, movable bridges share many common components and designs. Most of them use weight bearing towers for the movable span using electric or electro-hydraulic systems lift and/or rotate these movable spans. Automated locks hold the bridge in place as soon as the movement stops. The bridge operation, train and ship signaling systems work in synchrony for trains and waterway traffic to be granted safe passage with minimal delay. This synchrony is maintained by using custom-made control systems using Programmable Logic Controllers (PLCs) or Field Programmable Gate Arrays (FPGAs). Controllers located on the movable and the static parts of the bridge communicate using radio and/or wired underwater links sometimes involving marine cables. The primary objective of this paper is to develop a framework to analyze the safety and security of the bridge operating systems and their synchronous operations with railway and waterway systems. We do so by modeling the movable physical components and their control system with the interconnected network system and determine the faults and attacks that may affect their operations. Given the prevalence of attacks against PLCs, FPGAs and controllers, we show a generic way to determine the effect of what if scenarios that may arise due to attacks combined with failures using a case study of a swing bridge.

Effect of Strand Indentation Types on the Development Length and Flexural Capacity of Concrete Railroad Ties Made With Different Prestressing Strands

Pretensioned concrete prisms made with five different prestressing strand types (four 7-wire strands and one 3-wire strand) were load tested to failure to understand the effect of strand indentation types on the development length and bonding performance of these different reinforcements. The prestressing strands were denoted SA, SB, SD, SE and SF. SA was a smooth strand while the other four were indented strands. All strands utilized in manufacturing ofprisms had diameter of 3/8″ (9.52 mm). Among all types of strands, SF was the only 3-wire strand and the remaining strands were all 7-wire strands. For all types of strands, four straight strands were embedded into each concrete prism, which had a 5.5″ (139.7 mm) × 5.5″ (139.7 mm) square cross section. The strands were tensioned to 75 percent of ultimate tensile strength of strands 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. Prisms were load tested in 3-point-bending at different embedment lengths to obtain estimations of the development length of each type of strand. Two out of three identical 69-in.-long (175.26 cm) prisms were load tested at one end and one was tested at both ends for each reinforcement type evaluated. First prisms were tested at 28-in. (71.12 cm) from the end, while second prisms were tested at 20-in. (33.02 cm) from the end. Third prisms were loaded at 16.5-in. (41.9 cm) from one end and 13-in. (33.02 cm) from the other end. Thus, a total of 20 load tests (5 strand types × 4 tests each) were conducted in this study. During each test, a concentrated load with the rate of 900 lb/min (4003 N/min) was applied at mid-span until failure occurred. Values of load, mid-span deflection, and strand endslip were continuously monitored and recorded during each test. Plots of load-vs-deflection were then compared for prisms with each strand type and span, and the maximum sustained moment was also calculated for each test. The load tests revealed that there is a large difference in the development length of the strands based on their indentation type.

High Speed Intercity and Urban Passenger Transport Maglev Train Technology Review: A Technical and Operational Assessment

Magnetic levitation (maglev) is a highly advanced technology which provides, through magnetic forces, contactless movement with no wear and friction and, hence, improved efficiency, followed by reduced operational costs. It can be used in many fields, from wind turbines to nuclear energy and elevators, among others. Maglev trains, which use magnetic levitation, guidance and propulsion systems, with no wheels, axles and transmission, are one of the most important application of the maglev concept, and represents the first fundamental innovation of rail technology since the launch of the railroad era. Due to its functional features, which replaces mechanical components by a wear free concept, maglev is able to overcome some of the technical restrictions of steel-wheel on rail (SWR) technology, running smoother and somewhat quieter than wheeled systems, with the potential for higher speeds, acceleration & braking rates and unaffected by weather, which ultimately makes it attractive for both high speed intercity and low speed urban transport applications. From a technical perspective, maglev transport might rely on basically 3 technological concepts: i) electromanetic suspension (EMS), based on the attraction effect of electromagnets on the vehicle body, that are attracted to the iron reactive rails (with small gaps and an unstable process that requires a refined control system); ii) Electrodynamic Levitation (EDL), which levitates the train with repulsive forces generated from the induced currents, resulted from the temporal variation of a magnetic field in the conductive guide ways and iii) Superconducting Levitation (SML), based on the so called Meissner Effect of superconductor materials. Each of these technologies present distinct maturity and specific technical features, in terms of complexity, performance and costs, and the one that best fits will depend on the required operational features of a maglev system (mainly speed). A short distance maglev shuttle first operated commercially for 11 years (1984 to 1995) connecting Birmingham (UK) airport to the the city train station. Then, high-speed full size prototype maglev systems have been demonstrated in Japan (EDL) (552 kph - 343 mph), and Germany (EMS) (450 kph - 280 mph). In 2004, China has launched a commercial high speed service (based on the German EMS technology), connecting the Pudong International Airport to the outskirts of the city of Shanghai. Japan has launched a low speed (up to 100 kph - 62.5 mph) commercial urban EMS maglev service (LIMINO, in 2005), followed by Korea (Incheon, in 2016) and China (Changsha, in 2016). Moreover, Japan is working on the high speed Maglev concept, with the so called Chuo Shinkansen Project, to connect Tokio to Nagoya, in 2027, with top speeds of 500 kph (310 mph). China is also working on a high speed maglev concept (600 kph - 375 mph), supported on EMS Maglev technology. Urban Maglev concept seeks to link large cities, with their satellite towns and suburbs, to downtown areas, as a substitute for subways, due to its low cost potential, compared to metros and light rail (basically due to their lower turning radius, grade ability and energy efficiency). High Speed Maglev is also seen as a promising technology, with the potential do provide high quality passenger transport service between cities in the 240–1,000 km (150–625 mi) distance range into a sustainable and reliable way. This work is supposed to present, based on a compilation of a multitude of accredited and acknowledged technical sources, a review of the maglev transport technology, emphasizing its potential and risks of the low and high speed (urban and intercity) market, followed by a brief summary of some case studies.

MIMO Channel Capacity for Rail Transportation Applications: The Impact of Tunnel Curvatures

Rail transportation industry has drawn a growing interest on the use of Radio Access Technology for critical and non-critical services to improve safety/reliability, performance, and passenger experience. During the past two decades the theory and practice of the MIMO communications has solidified to the point where MIMO is now the main infrastructure for several legacy and emerging radio access standards. In this paper, the impact of subway tunnels’ curvatures on the MIMO channel capacity is explored. A heuristic approach is proposed which provides an efficient and low complexity solution for the MIMO channel capacity in curved subway tunnels for both the C-MIMO and the D-MIMO paradigms. The suggested approach is quite versatile and can be swiftly expanded to the case of multi-segment inhomogeneous tunnels.

Clustering Algorithms for Direct Current Track Coded Signals

Designed for detecting train presence on tracks, track circuits must maintain a level of high availability for railway signaling systems. Due to the fail-safe nature of these critical devices, any failures will result in a declaration of occupancy in a section of track which restricts train movements. It is possible to automatically diagnose and, in some cases, predict the failures of track circuits by performing analytics on the track signals. In order to perform these analytics, we need to study the coded signals transmitted to and received from the track. However, these signals consist of heterogeneous pulses that are noisy for data analysis. Thus, we need techniques which will automatically group homogeneous pulses into similar groups. In this paper, we present data cleansing techniques which will cluster pulses based on digital analysis and machine learning. We report the results of our evaluation of clustering algorithms that improve the quality of analytic data. The data were captured under revenue service conditions operated by Alstom. For clustering algorithm, we used the k-means algorithm to cluster heterogeneous pulses. By tailoring the parameters for this algorithm, we can control the pulses of the cluster, allowing for further analysis of the track circuit signals in order to gain insight regarding its performance.

U.S. Freight Rail Fuel Efficiency: 1920-2015 Review and Discussion of Future Trends

U.S. freight railroads produce about 40 percent of freight gross ton-miles while consuming only about 1/20th of the total U.S. diesel fuel1. Compared to heavy-duty trucks, freight railroads have significant energy (and emissions) advantages including the low coefficient of friction of steel wheel-on-rail (compared to rubber tires-on-pavement) and multiple-vehicle trains. However, improved heavy-duty truck technologies are being federally-funded and developed which may create some challenges to freight rail’s long-standing environmental (and economic) advantage in certain transportation markets and corridors. This paper reviews U.S. freight rail fuel efficiency (measured in gallons of fuel per thousand gross ton-miles) from 1920 to 2015, using published records from the former Interstate Commerce Commission (ICC) archived and made available by the Association of American Railroads (AAR). All freight locomotive energy consumption (all types of coal, crude oil, electricity kilowatt-hours and diesel fuel) are converted into approximations of diesel gallons equivalent based on the nominal energy content of each locomotive energy type, in order to show the effect of transitioning from steam propulsion to diesel-electric prior to 1960 and the application of other new technologies after World War II. Gross ton-miles (rail transportation work performed) will similarly be tracked from historic ICC and AAR records. Annual U.S. freight rail fuel efficiency is calculated and plotted by dividing total calculated diesel gallons equivalent (DGe) consumed by gross (and by lading-only net) ton-miles produced. New technologies introduced since 1950 which have likely contributed to improvements in freight rail fuel efficiency (such as introduction of unit coal trains, distributed power, alternating current locomotives, etc) will also be discussed and assessed as to relative contribution to fuel efficiency improvements. The paper includes a discussion about U.S. freight rail fuel efficiency compared to heavy-duty truck fuel efficiency, with comments on projected improvements in heavy-duty truck technologies and fuel efficiency. A conclusion is that U.S. freight railroads and equipment suppliers need to be more aware of projected heavy-duty truck fuel efficiency improvements and their potential for erosion of some aspects of traditional railroad competitiveness. Numerous suggested action plans are discussed, with particular focus on reducing the aerodynamic drag (a delta velocity-squared factor in train resistance and power requirement) of double-stack container trains. Last, this paper discusses possible courses of action for U.S. freight railroads to achieve fuel efficiency improvements greater than the historic ∼1 percent improvement achieved over the past 50 years. If freight rail is to remain economically competitive vis a vis heavy duty trucking, railroads will have to identify, evaluate and implement new technologies and/or new operating practices which can help them achieve fuel efficiency improvements matching (or exceeding) those projected for heavy trucks over the next 7-to-12 years. A specific example for improving fuel efficiency of double-stack container trains is discussed. Failure to address the future of freight rail fuel efficiency is likely not an option for U.S. railroads.

Milwaukee Streetcar Overhead Contact System: A Challenging Design Effort

The new Milwaukee Streetcar system has been in the planning, design and construction phases for over 10 years and on November 2, 2018, operations with a combined overhead contact system and streetcar battery power commenced ushering in a new era of growth for the City of Milwaukee. Many challenges in the design and construction of the overhead contact line and power system were encountered during this time period including budgetary constraints, multiple pole location changes, underground obstacles, low clearance bridges, alignment changes, utility conflicts, and changing vehicle requirements. The line was originally designed for pantograph operation but soon adapted for pole/pantograph current collection and then changed back to pantograph only current collection during the final design. The original design consisted of underground feeder cables to supplement a 4/0 contact wire but eventually not utilized due to budgetary constraints. Instead, a larger 350 kcmil contact wire was used with no paralleling feeder cables. The added weight of a 350 kcmil wire with wind, ice and low temperatures created high forces in the overhead contact system (OCS) leading to challenges in pole and foundation design where compliance to the National Electrical Safety Code (NESC) was required. The OCS style originally proposed and finally constructed used an inclined pendulum suspension (IPS) system that was constant tensioned with rotating springs deemed by the installing contractor superior to balance weights. The pendulum system was chosen as it is simple, lightweight, less visually obtrusive, and more economical than other suspension systems such as stitch and steady arm that are being used on other streetcar or light rail systems. IPS has provided Milwaukee with an excellent operating overhead contact system. Buildings along the route that were not historic structures were utilized where possible for span wire attachment but in many locations long bracket arms up to 40 feet long had to be used requiring special designs to keep the size of the pipes standard with the rest of the system. Challenges arose at low bridge underpasses where the contact wire had to be below required code height and special precautions had to be undertaken. Other areas such as the St. Paul Lift Bridge proved challenging as well where special electrically interlocked OCS devices were initially designed to de-energize the overhead wires and is further discussed with the reasoning for their use. This paper outlines the phases of design, the changes to the design that occurred over time, the challenges encountered to the OCS design, the method of design, and the final disposition of the design for construction. It further outlines the construction of the system and problems encountered with poles, foundations, bracket arms, traction power substations, contact wire, feeder cables, and winter conditions affecting the integrity of these structures and how some of these problems were solved.

Evaluating the Effect of Natural Third Body Layers on Friction Using the Virginia Tech Roller Rig

In this study, the effect of natural third body layers on the coefficient of friction and contact forces is evaluated using the Virginia Tech-Federal Railroad Administration (VT-FRA) roller rig facility. The test rig allows us to precisely control the contacting surfaces to study its effect on the wheel-rail interface forces and moments. Experiments have shown while running the tests, a slight amount of wear occurs at the running surfaces. The worn material deposits at the surface and behaves like a “natural” third-body layer at the contact, resulting in changes in traction coefficient and creep forces. The material wear and its accumulation on the running surfaces change with wheel longitudinal load and creepage. A series of organized time-based experiments have been conducted with the running surfaces cleaned at the beginning of the test to study the effect of material wear accumulation on selected parameters including traction coefficient and creep forces over time. In order to highlight the effect of the natural third body layer on the wheel-rail contact forces, a series of experiments were conducted, in which the wheel and roller surfaces were cleaned in one case and left uncleaned in another. The results of the experiments are quite revealing. They indicate that when the running surfaces are cleaned after each test, the maximum creep force (or adhesion) is far lower than when the running surfaces are not cleaned, i.e., the natural third-body layer is allowed to accumulate at the surfaces. The results indicate that the wear debris act as a friction enhancer rather than a friction reducer.

Studying the Effect of Tangential Forces on Rolling Contact Fatigue in Rails Considering Microstructure

In this paper, the micro-mechanical mechanisms behind the initiation and propagation of rolling contact fatigue (RCF) damages caused by the large traction forces are investigated. This study provides a three-dimensional (3D) model for studying the rolling contact fatigue in rails. Since rolling contact fatigue is highly dependent on the rail’s steel microstructure behavior, a proper 3D approach to capture the microstructure- and orientation-dependent mechanical behavior is required. A precise material model known as crystal plasticity is used for this purpose. Additionally, a cohesive zone approach is implemented to capture the crack initiation and propagation at the grain boundaries. Using the 3D finite element model which is developed for this study, we evaluate the effect of various parameters such as traction forces along the rail, and also the normal forces on the RCF response. The results reveal that the RCF cracks initiate slightly below the rail surface. These cracks start propagating toward the rail surface when the contact force is applied in repeated load cycles. The results also indicate that the depth at which RCF initiates depends on the ratio between the longitudinal traction forces and the normal loads. With larger traction forces, the cracks initiate closer, or at the rail surface, whereas larger normal loads promote the cracks initiation beneath the surface.

Boundary Conditions Effects on the Crack Growth Mechanism Under Cycling Bending

The recent increase of train speed and frequency determines a rise of the loads transmitted to the superstructure. Therefore, railway components might experience service loads that have not considered at the design stage. Moreover, wear and backlash modification between components of a mechanical system might be able to modify the internal boundary conditions of the assembly. According to damage tolerance philosophy, an initial flaw is assumed to exist in the fatigue critical location of a structural component, and the analysis of the crack propagation life for such component needs accurate Stress Intensity Factor (SIF) evaluations. In this study, the effects of the boundary conditions on the crack propagation life have been evaluated for a semi-elliptical surface crack having semi-axes a and c and growing from the root of a shoulder fillet notch in a round bar loaded in bending. Two cases have been analyzed: - the shoulder is free from external forces; - the shoulder is in contact with an adjacent generic body. At first, the SIF distribution has been calculated with the Virtual Crack Closure Technique, considering or not the nonlinear effect induced by the contact forces arising from the interaction between the shoulder and the neighboring component. Successively, in both the above cases a two-parameters propagation law has been utilized to predict the evolution of both crack shape and crack depth when a cyclic bending load is applied to the rod. For this purpose, different values of the Stress Concentration Factor at the root of the fillet, and of the initial aspect ratio of the crack front, were considered in the calculations. It is found that the aspect ratio evolves to a unique asymptote, taking or not into account the non-linearity introduced by the contact at the shoulder, and this value depends on the notch severity. The ratio between the dimensionless SIFs obtained with and without the unilateral constraint at the shoulder, βcs / βfs, does not depend on the relative crack depth and crack shape. Also, the effect of the notch severity on the dimensionless SIF appears to be evident only for the portion of the crack front in the vicinity of the free surface.