This numerical study focuses on evaluating the structural performance of prestressed concrete prisms with larger diameter (0.315 in) prestressing wires. More commonly used prestressing wires are the 0.209 in (5.32 mm) diameter wires for prestressed concrete crossties. However, there has been an interest to adopt larger diameter prestressing wires in order to provide higher prestress forces with the aim of mitigating the structural damage of prestressed concrete crossties. Previous experimental studies demonstrated that small-scale pretensioned concrete prisms had excellent correlation in bonding performance of concrete ties pretensioned with 0.209 in (5.32 mm) wires or three- or seven-wire strands. Using a finite element (FE) modeling approach, this study investigates the effects of 8 mm diameter prestressing wires on the splitting/bursting performance of prisms at the onset of de-tensioning of the wires. The studied parameters include geometrical/mechanical parameters such as thickness of the concrete cover, spacing between the wires, level of prestress forces, and concrete release strength in compression. Cohesive elements with a newly developed nonlinear bond-slip model are assigned to the interface between the prestressing wires and the surrounding concrete. The parameters for the bond-slip model are calibrated based on a simple pull-out test on concrete cylinders with the 0.315 in (8 mm) diameter wires. The simulation results are compared with the predicted splitting performance of prisms pretensioned with 0.209 in (5.32 mm) wires or seven-wire strands. Based on the FE analysis results, recommendations are made on the minimum concrete cover thickness and wire spacing required to achieve acceptable splitting/bursting performance in prestressed concrete prisms.

In this work, the non-destructive ball indentation technique is applied to estimate fracture toughness for three types of high-strength rail steels based on continuum damage mechanics. Damage parameter, in terms of the deterioration of elastic modulus, is measured for three rail steels using the loading-unloading smooth tensile test, based on which a ductile damage model is calibrated to determine the critical damage parameter at the onset of fracture. Meanwhile, an instrumented ball indentation test is conducted on the three rail steels to generate damage as a function of contact depth under indentation compression. The critical damage parameter from the smooth specimen is then applied to the indentation test to determine the critical contact depth for calculating the indentation fracture toughness based on the concept of indentation energy to fracture. Results show that although the magnitude of the so-determined indentation fracture toughness is greater than that of the corresponding mode I critical stress intensity factor ( K Ic ) measured using the pre-cracked single-edge-notched bend (SENB) specimen, the former can well predict the ranking order of the K Ic values among the three rail steels.

Cold-formed stainless steel is often used in the design and fabrication of passenger rail vehicle car body structures. It is attractive because of its corrosion resistance and the high yield strength in the quarter- and half-hard conditions. One of the complications in designing with this material is its anisotropic properties: the yield strength and stress-strain curve depend upon whether the material is loaded in tension or compression and upon the loading direction relative to the material rolling direction. This phenomenon has been known for some time in the rail industry, and is also well known in the general structural community. This paper is a review of the mechanical and metallurgical properties of cold-formed stainless steel and of current design approaches related to buckling of members made from this product form.

For the railway wireless monitoring system, energy efficiency is important for prolonging the system lifetime and ensuring the successful transmission of the inspection data. In general, decreasing the size of the data packet is conductive to declining the transmission energy consumption. Hence, the inspection data packets should be processed before being transmitted. However, the energy consumption of data processing may also be considerable, especially for the vision-based monitoring system. Therefore, we propose an optimization methodology to address the trade-off of the energy usage between data processing and transmission in railway wireless monitoring systems. In addition, the various data types and transmission distances of the sensors may cause the unbalanced energy consumption, and it will shorten the system lifetime due to the failure of some sensors. To address this challenge, in our proposed optimization framework, we adopt customized compression ratios for each sensor to balance its energy consumption. On this basis, the system lifetime can be extended by minimizing and balancing the energy consumption simultaneously. Finally, we use several generalized numerical examples to demonstrate the superiority and practicality of the proposed strategy. Compared to previous methods in the literature, our proposed approach can increase service lifetime of wireless monitoring systems using equal and less energy.

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.

Grade separations have been used along High-Speed Rail (HSR) to decrease traffic congestion and the danger that occurs at grade crossings. However, the concern with grade separations is the potential damage due to lateral impact of bridge superstructures by over-height vehicles. This is a concern with existing bridges, and lateral impact is not included in standard bridge code provisions. A new bridge technology, Hybrid Composite Beam (HCB), was proposed to meet the requirements of another HSR objective, that of a sustainable solution for the construction of new and replacement bridges in rail infrastructure. The hybrid composite beam combines advanced composite materials with conventional concrete and steel to create a bridge that is stronger and more resistance to corrosion than conventional materials. The HCB is composed of three main parts; the first is a FRP (fiber reinforced polymer) shell, which encapsulates the other two parts. The second part is the compression reinforcement which consists of concrete or cement grout that is pumped into a continuous conduit fabricated into the FRP shell. The third part of the HCB is the tension reinforcement that could consist of carbon or glass fibers, prestressed strands, or other materials that are strong in tension, which is used to equilibrate the internal forces in the compression reinforcement. The combination of conventional materials with FRP exploits the inherent benefits of each material and optimizes the overall performance of the structure. The behavior of this novel system has been studied during the last few years and some vertical static tests have been performed, but no dynamic or lateral impact tests have been conducted yet. Therefore, the main objective of this study is to evaluate the performance of HCB when subjected to lateral impact loading caused by over-height vehicles. This paper explains the advantages of HCB when used in bridge infrastructures. The commercial software ABAQUS was used to perform the finite element (FE) modeling of a 30ft long HCB. Test data was used to validate the results generated by FE analysis. A constant impact loading with a time duration of 0.1 second was applied to an area at the mid-span of the HCB. Lateral deflection and stress distribution were obtained from FE analysis, and local stress concentration can be observed from the stress contour. Full-scale beam dynamic testing will be conducted in the future research to better study the behavior of HCB when subjected to over-height vehicles.

To adequately satisfy the demands placed on North America’s railway infrastructure through ever increasing freight tonnages and development of its high speed rail program, the design and performance of concrete ties and elastic fastening systems must be improved. As a part of a study funded by the Federal Railroad Administration (FRA) aimed at improving concrete crossties and fastening systems, field experimentation was performed at the Transportation Technology Center (TTC) in Pueblo, CO by researchers from the University of Illinois at Urbana-Champaign (UIUC). This paper details the extensive instrumentation program which includes strain gages and linear potentiometers. Testing was conducted over seven adjacent concrete crossties in tangent and curve track utilizing TTC’s Track Loading Vehicle (TLV) as well as passenger and freight train consists. Measurements taken consisted of the wheel-rail input loads, component stresses (e.g. insulator post compression), concrete tie strains, and displacements of the rail and concrete tie. The data was collected synchronously to provide a means to capture the load path, target areas of uncertainty, and provide comprehensive data for the validation of a multi-tie, 3-D finite element model being developed by UIUC. Varying train speeds, track curvature, and loading types provided a means to assess the loading variability that can be expected within the fastening system and lead to more purposeful and efficient instrumentation strategies. Furthermore, this data can be used to guide future research in further quantifying the field loading demands on system components, ultimately leading to the mechanistic design of the concrete crosstie and fastening system.

For the past two decades, the Federal Railroad Administration (FRA) Office of Research and Development has sponsored research conducted by the Volpe National Transportation Systems Center (Volpe Center) in safety matters related to the transportation of hazardous materials by railroad tank cars. Recent research conducted by the Volpe Center has included the application of semi-empirical and computational (i.e., finite element analysis) methods to estimate the puncture resistance of conventional railroad tank cars under generalized head and shell impact scenarios. Subsequent work identified sandwich structures as a potential technology to improve the puncture resistance of the commodity-carrying tank under impact loading conditions. This paper summarizes basic research (i.e., testing and analysis) conducted to examine the deformation behavior of flat-welded steel sandwich panels under two types of quasi-static loading: (1) uniaxial compression; and (2) bending through an indenter. The objectives of these tests were to: (1) confirm the analytical and computational (i.e., finite element) modeling of sandwich structures, (2) examine the fabrication issues associated with such structures (e.g., material selection and welding processes), and (3) observe the deformation behavior and local collapse mechanisms under the two different types of loading. In addition, the uniaxial compression tests were performed to rank or screen different core geometries. Five core geometries were examined in the compression tests: pipe or tubular cores with outer diameters equal to 2, 3, and 5 inches; a 2-inch square diamond core; and a double-corrugated core called an X-core with a 5-inch core height. The compression tests showed excellent repeatability of structural (i.e., force-crush) response for panels with similar cores and welding. The 3-inch pipe core and the diamond core were selected as candidate cores for the next test series because they possess attributes of moderate strength and moderate relative density. In addition, force-crush curves calculated from finite element analysis were in reasonable agreement with the measured curves for all cores. Bend tests using a 12-inch by 12-inch indenter with 1-inch radius rounded edges were also conducted. The panels were simply-supported over 4-inch diameter rollers spanning 24 inches between the centers of the rollers. The bend tests included three variables: (1) core type (diamond core and 3-inch pipe core); (2) core orientation relative to the supports (cores running either parallel or perpendicular to the rollers used to support the panels); and (3) face sheet type (solid plates on both sides, strips used as face sheets on both sides, and a combination of solid plates and strips. Finite element analysis of the bend tests produced nearly identical shapes to the measured force-displacement curves.

Railway specialists expect that the demand for rail-bound passenger and freight traffic in the US will increase enormously in the coming years. Implementing the American Recovery and Reinvestment Act (ARRA) of 2009, new high-speed lines will be created throughout the nation. This will lead to an additional increase of passenger traffic demand. Experiences from Western Europe have shown that new high-speed passenger lines will cause changes in user demand behavior as well as an augmentation of the importance of regional lines featuring connections to the high-speed network. The existing stations will not only be greater utilized by the new high-speed lines, but a growth in demand for regional lines could also require an increasing number of trains. That could lead to greater infrastructure utilization as well. Both aspects lead to the question of whether the already existing large stations of the future high-speed network possess enough capacity for handling such a large number of trains. It is comprehensible that station capacity will play a very important role for planning new corridors. While UIC Code 406 contains first steps of defining a standardized method for doing line capacity research, it does not include any information about station capacity evaluations. A few analytical methods for doing such evaluations are described in this paper. Most of these methods are easy to apply but offer important values for evaluating existing station infrastructure as well as timetables. It is also shown that the compression method presented in UIC Code 406 cannot be used for doing station capacity research.

This paper describes the conduct of the first of a series of quasi-static compression tests of rail passenger equipment being done to examine occupant volume strength. Specifically, this program is investigating methods of evaluating occupant volume integrity when loads are placed along the collision load path of the occupant volume. Budd Pioneer car 244 has been chosen as the test article to examine alternative occupant volume loading strategies. Since this car has been involved in several impact tests as part of a previous research program, it is important to verify the structural integrity of the vehicle before conducting an alternative loading test. Although the vehicle has been modified with crash energy management crush zones at both ends, the occupant volume between the body bolsters is unmodified from the original structure. The 800,000-pound compressive strength test will be used to ensure the structural integrity of the car is intact. Before the conduct of this test, repairs were made to the crush zone. These repairs included replacement of trigger elements in the form of shear bolts and shear rivets. Additionally, energy absorbing elements were removed from the pushback coupler and primary energy absorbers because they would not contribute to the load path of this test. Steel blocks were added to the sliding sill element, enabling it to contact the fixed sill and enhancing the load-bearing capacity of the sliding-fixed sill connection. Preliminary results of this test include an overall description of the test procedures, discussion of permanent deformation observed during the test, and presentation of finite-element simulation results. Detailed analysis of test results, including strain gage data, is ongoing. The test results are being compared with the finite-element model results in support of the next tests planned for this series. The next two tests will evaluate the carbody when it is loaded along its collision load path to establish the elastic limit and crippling strength.

Longitudinally Coupled Prefabricated Ballastless Track (LCPBT) system was firstly applied on Suining-Chongqing experimental railway line and Beijing-Tianjin intercity railway line. LCPBT track structure is longitudinally continuous, with fixing a 5-cm-thick hard foam board above every bridge structure joints, between bridge protection layer and the continuous concrete base to reduce detrimental fastening pulling force in case of great rotation angle or displacement. Hard foam board ensures a steady deformation transition, and we calculate its compressive stress, compression and cubical elasticity coefficient Q , for fulfilling force-bearing and deformation requirements. Taking a two-span, simple supported beam, each with 32-m-long bridge for instance, an integral finite element model of continuous welded rail -coupled track slab -coupled concrete base –bridge beam was established, in which a vertical compression amount under 9 different load cases. The maximum bottom tensile stress of concrete base, maximum compressive stress and compression amount of hard foam board are gained from computation results. Besides, Q -value and the control value of rotation angle at bridge structure joints are suggested in this paper. The key findings are: a) under simultaneous actions of train load and beam rotation angle, the maximum bottom tensile stress of concrete base does not exceed its threshold as 250 kPa, given a Q -value of 0.5 N/mm 3 ; b) considering the uniformity of track stiffness and track regularity, a greater Q -value is preferable and we recommend the Q -value as 0.5 N/mm 3 ; c) the beam rotation angle at bridge structure joints should be less than 1.4, including the load cause of uneven settlement of adjacent bridge piers, uneven settlement of adjacent bridge foundation; d) uneven settlement of adjacent bridge foundation on the same bridge pier must be strictly controlled to avoid affecting the service life of hard foam board.

This paper presents the computational fluid dynamics (CFD) modeling to study the effect of intake port bend angle on the flow field inside the cylinder of a direct injection (DI) diesel engine under motoring conditions. The flow characteristics of the engine are investigated under transient conditions. A single cylinder DI diesel engine with two direct intake ports whose outlet is tangential to the wall of the cylinder and two exhaust ports has been taken up for the study. Effect of intake port bend angle (20°, 30°, and 40°) on the flow field inside the cylinder has been investigated at an engine speed of 1000 rpm. The pre-processor GAMBIT is used for model preparation and commercial computational fluid dynamics code STAR-CD has been used for solution of governing equations and post processing the results. CFD results during both intake and compression strokes have been compared with experimental results of Payri et-al [7, 8]. The predicted swirl ratio, radial velocity and turbulent intensity variations at different crank angles and at different locations are discussed. Distribution of velocity and turbulence intensity inside the cylinder is also discussed. It is observed that the intake ports with 20° bend angle produce maximum swirl and also results in a slight decrease in volumetric efficiency compared to intake ports with 30° and 40° bend angles and there is no appreciable variation in turbulent intensity. Hence, for the better performance of a DI diesel engine, it is concluded that the intake ports with 20° bend angle is most appropriate and CFD is an effective design tool to develop more efficient DI diesel engines.

This paper reports the Computational Fluid dynamic modelling to study the mixture preparation strategies for a 4 valve DISI engine under motoring condition. The suitability of air guided mixture preparation concept for a flat piston engine is investigated. Three different valve configurations viz., standard valve, forward tumble shroud valve and reverse tumble shroud valve are used to create different bulk air flow pattern viz., standard tumble, forward tumble and reverse tumble inside the engine cylinder. Two speed viz., 1000 and 2000 rpm with different fuel injection timings (90°, 180° and 270°) have been considered. The fuel injector is located near central axis of the cylinder and the spark plug is located between the intake valves on the fire deck of the engine. Gambit Pre-Processor is used to create the computational domain and the commercial CFD package STAR CD is used for simulation and post processing. The effect of air motion inside the cylinder on the turbulent kinetic energy and equivalence ratio prevailing near the spark gap are studied. Compared to standard valve configuration the forward tumble and reverse tumble valve configurations are able to produce higher tumble index for the speeds simulated. The mean turbulent kinetic energy prevailing inside the engine cylinder is sustained for the forward tumble and reverse tumble cases, well into the end of compression stroke which is attributed to the higher tumble for these cases, which may enhance burning rate. For the simulated cases of no shroud valve the equivalence ratio at the spark gap for higher speed (2000 rpm) is higher than the lower speed (1000 rpm) for the same injection timing. This may be attributed to higher turbulence at higher speed. The same trends is noticed for the forward tumble shroud valve and reverse tumble shroud valve configuration cases except for 180° injection timing where the higher speed case produces lesser strength of mixture at the spark plug gap. From the analysis of the simulated cases for different bulk flow inside the cylinder the forward tumble configuration with wide spacing arrangement of spark plug and injector, consistently produces a better mixture near the spark plug gap for all the injection timing for the two speeds simulated. Hence the forward tumble air motion with wide space concept may be a viable strategy for maintaining proper equivalence ratio at the spark plug at different loads and better combustion stability.