Dissertations / Theses on the topic 'Irregularity on the railroad track'

Railway tracks deteriorate over time due to the combined effects of train loads and environment. To carry out appropriate maintenance, it is necessary to measure the condition of the track. There are two broad categories of condition measures namely: function and structural measures of conditions. Functional measures of condition assess the condition of the track from the point of view of the user. An example of a commonly used functional measure of condition is track geometry. In the UK, track geometry is measured by the track recording coach and it is carried frequently on the entire network. On the other hand, structural measures of condition assess the structural integrity of the track. Example of a commonly used structural measure of condition is track stiffness. In the UK, track stiffness is measured using the Falling Weight Deflectometer (FWD) and it is carried out less frequently on specific railway track sections as it is very slow, requires closure of the track and is expensive to operate. The aim of this research is to investigate the feasibility of using track geometry measurement to extract track stiffness information and ultimately develop a prototype automated system to achieve this.

High-Speed Rail (HSR) as a fast, reliable and environmentally friendly mode of transportation has received a lot of attention in recent decades. The International Union of Railways reported that there are more than 18600 miles of HSR in operation and about 1.6 billion passengers per year are carried by them. Although there are plans for HSR in many states including Florida, the United States, however, is still hesitant to develop its own HSR network. One of the main barriers to developing high-speed rail is excessive vibration propagation to the media which may cause annoyance to people who live in the track neighborhood. Train induced vibration also contributes to track settlement, developing track flaws, and increasing life cycle cost of track and supporting structures. The aim of this research is to address this problem by conducting a comprehensive investigation into track dynamics. For this purpose, three-dimensional mass-spring-damper models of vehicle, track and supporting structures were developed and matrices of mass, stiffness, and damping of each subsystem were formed. The response of the whole system was, then, determined by coupling the subsystems using Hertz contact theory. The differential equations of the coupled system were solved by the Newmark integration method and the results including vertical and lateral displacements and forces were presented in the time domain. Since the purpose of this dissertation is to quantify the effect of track and vehicle condition on vibration level, rail defects were also taken into account and rail random irregularities for the vertical profile, Gauge, alignment and cross level (super elevation) were incorporated into a numerical solution. The results of the study show the effect of track and vehicle parameters on the response of the vehicle, track, and substructures. Since Florida and some other states in the United States are very prone to hurricanes, an investigation was conducted into the effect of wind speed on vehicle stability. For this purpose, a curved beam was modeled to consider the influence of track curvature, cant deficiency, wind speed and train speed simultaneously. The results from the study show the maximum allowable values of train speed and axle load for different wind speeds. The findings can be used to decide under what circumstances there is a risk of vehicle overturning and how to avoid it.

This thesis adopts a holistic approach towards railway track capacity to develop methodologies for different aspects of defining, measuring, analysing, improving and controlling track capacity utilisation. Chapter 1 presents an overview of the concept of capacity and the railway capacity challenge is explained. Chapter 2 focuses on past approaches to defining and analysing the concept of railway capacity. Existing methods for estimating capacity utilisation are studied in four categories: analytical methods, parametric models, optimisation and simulation. Chapter 3 examines various factors affecting capacity utilisation. Chapter 4 develops the systems engineering foundation toward railway capacity. From process improvement methods, Six Sigma and its Define, Measure, Analyse, Improve and Control (DMAIC) cycle is chosen as the underlying framework of the thesis. Chapter 5 defines lean, micro and macro capacity utilisation based on the discrete nature of railway capacity. Data Envelopment Analysis (DEA) is used to develop two novel methodologies to analyse lean capacity utilisation. A DEA model analyses relative efficiency of train operating companies based on their efficiency to transform allocated train paths (timetabled train kilometres) and franchise payments to passenger-kilometres while avoiding delays. A case study demonstrates its application to 16 train operating companies in the UK. The operational efficiency of stations is benchmarked from similar studies for ports and airports. Two models are developed for analysing technical efficiency and service effectiveness. 96 busiest stations in Great Britain are analysed by this method. For analysing capacity utilisation in the freight sector, the concept of ‘profit-generating capacity’ is introduced in chapter 6. It is applied in an American freight case study to choose between bulk and intermodal trains in a heterogeneous traffic. DEA is also used in another case study for identifying the most profitable commodities. Chapter 7 suggests using variation reduction and failure mode and effect analysis (FMEA) to control capacity utilisation. For improving railway capacity utilisation it is suggested to find and improve the weakest line section, the weakest trains and the weakest station. A real world case study of the South West Main Line in Great Britain, demonstrates applying these aspects. For finding the weakest line section two existing methods of the UIC 406 and the CUI method are compared with each other. For finding the weakest trains a meso index is suggested. It can identify which trains can be removed to free up some capacity in the busiest section of the line. Simulating delays and removing the highest delay causing trains is another method suggested. The weakest stations are identified by applying the DEA methodology developed in chapter 5. Target values for train stops at each station are suggested to be fed to the tactical timetabling. It is concluded that developing methodologies to analyse, improve and control railway capacity utilisation is needed and the methodologies proposed in this thesis can be a stepping stone towards them.

Maintenance management decision-support systems are needed to help senior decision-makers and asset managers to better plan timely and efficient maintenance. Within the railway industry, several maintenance management decision-support systems have been developed. However, most these operate at project level where decisions are limited to short sections of track. Network level maintenance management systems enable future prediction of the condition of the railway network under different allocation of resources in a manner to provide acceptable levels of safety, reliability and cost. This project describes the development of a theoretical framework for the strategic assessment of network level railway maintenance funding and policy decisions. The model is designed to aid railway asset managers in planning medium to long-term maintenance investment requirements for the railway network. The model is based on stochastic processes which are capable of determining the effects of traffic, maintenance and climate on network condition under any budget scenario.

This thesis examines the effect of vehicle dynamics on lateral deterioration of the track alignment. As rail traffic runs along a route, the forces imposed upon the track cause the ballast to settle, and hence the track geometry deteriorates. At a specified value of deterioration the track geometry needs to be restored by tamping or other methods. As the deterioration is mainly in the vertical direction, this aspect has been more widely studied and models have been developed to predict vertical track geometry deterioration. On the other hand, lateral track deterioration is not as well understood, and this thesis aims to fill the gap in this knowledge. However, the understanding of the lateral deterioration mechanisms becomes more important as speed and capacity increase. This thesis describes statistical studies of track lateral deterioration, as well as the development and validation of a vehicle-track lateral dynamic interaction model. This work is undertaken to contribute to the fundamental understanding of the mechanisms of track lateral deterioration, therefore making the effective control and reduction of the lateral deterioration achievable. The statistical analysis provides a better understanding of three aspects of track lateral irregularities, namely: the relationship between vertical and lateral irregularities, the relationship between track curvature and track lateral irregularity and the change in track lateral deterioration over time. The vertical and lateral track irregularity magnitudes are clearly correlated. The track quality in the vertical direction is generally worse than in the lateral direction, however the number of track sections with lateral quality significantly worse than the vertical is non-negligible. The lateral irregularities tend to be larger on curves. It is notable that less than ten percent of the track studied has a constant lateral deterioration due to frequent maintenance activities and bidirectional lateral dynamic forces. Unlike vertical settlement, lateral deterioration develops exponentially in both magnitude and wavelength, and the major influences are found from the irregularities with wavelength longer than 10 m. The change in track lateral irregularity with different curve radii and the lateral deterioration rate are described in separate exponential power functions due to the limitation of the available track data. The parameters for these empirical equations do not remain constant due to the change in track conditions. Current track lateral models mainly focus on lateral failures such as buckling and lateral sliding. The development of lateral track irregularities tends to be studied using representative values of net lateral forces and net L/V (Lateral/Vertical) load ratios. Unlike other track lateral deterioration models, the model developed in this thesis focuses on the development of lateral irregularities based on the dynamic interactions between the vehicles and the track system. This model makes it possible to carry out more integrations and analysis of the track lateral deterioration in a realistic dynamic simulation, using vehicle models, contact conditions, track initial irregularities, and traffic mix more close to the reality. The vehicle-track lateral dynamic interaction model was validated against track geometry data measured on the West Coast Mainline (WCML) in England. It has been found that the model gives a reasonably accurate prediction of the development of lateral track irregularities. However, it also tends to predict a short wavelength deterioration that is not seen in the actual track deterioration. Improvements to the model are suggested by either adding more factors or simplifying the model depending on specific target application. Enhancing the model by including more details, such as longitudinal forces, temperature effect, more layered track systems, uneven track bed conditions and more representative wheel-rail contact conditions etc., may help understand the reason of the additional short wavelength. A sensitivity analysis was performed in order to identify the critical factors that influence lateral track deterioration. The track damage caused by specific vehicles can be controlled by understanding different vehicle dynamics behaviour on a particular track section or route. Vehicles with simple suspension design and heavy axle loads tend to cause more lateral track damage. Within a certain speed range, there will be a critical speed that generates the largest lateral deterioration. Vehicles with different dynamic behaviours can generate a potential offset of the lateral deterioration, so it is possible to design the traffic mix to cancel out the peak deterioration. However, it may not be very practical to redesign the traffic mix due to different traffic requirements. Subsequently, actions can be taken to effectively reduce track lateral deterioration, such as optimise the suspension design, vehicle weight, the selection of an optimal operation speed, and enhance the traffic mix design. As the most important interface between vehicle and track, the wheel-rail contact condition has an extremely large influence on lateral deterioration. Wheel and rail profiles with different wear conditions can cause altered vehicle-track lateral dynamic interaction. It is found that increasingly worn wheel/rail profiles within an acceptable tolerance can effectively reduce the lateral deterioration. Lateral deterioration can also be reduced by increasing all the track stiffness values, damping values and the mass of rails and sleepers, or alternatively, by decreasing the sleeper spacing. The sleeper-ballast interface is found to play the most important role in lateral deterioration. The interfaces between the sleeper and ballast shoulder, crib and base determines the non-linear characteristic such as hysteresis and sliding features. Improving the strength of the sleeper-ballast interface can improve the elastic limits and hysteresis characteristics, hence reducing the lateral deterioration. The findings of the investigation indicate that the model provides in-depth knowledge of the mechanisms influencing lateral deterioration and provides effective solutions with consideration of vehicles, wheel-rail contact and the track system. Further work would include track data with sufficient information in order to develop a more comprehensive empirical model that describes the lateral deterioration, inclusion of more potentially influential factors such as: temperature, ground condition, traffic etc. The model can be improved by taking into account additional factors such as the influence of longitudinal forces from the wheels to the rails, different weather and temperatures, subgrade and ground conditions, etc. The reason for the high frequency noise in the deterioration prediction is not understood yet and it should be discussed in terms of more accurate vehicle simulation results and more comprehensive rail and wheel worn profiles measured on the target track and vehicles. Furthermore, the sleeper-ballast lateral characteristics are not well understood and the previous research in this area is quite limited. To improve on the present work it would be useful to carry out laboratory tests in order to capture more accurately track lateral stiffness and damping values as well as the comprehensive non-linear characteristic of track lateral residual resistance behaviour.

The aim of this research is to develop a fuller understanding of the mechanical behaviour of the sleeper/ballast interface, related in particular, to the forces applied by high speed tilting trains on low radius curves. The research has used literature review, field measurements, and laboratory experiments on a single sleeper bay of track. Theoretical calculations are also presented. Field measurements are carried out using geophones to record time/deflection for sleepers during passage of Pendolino trains on the West Coast Main Line. Calculations are presented to quantify normal and extreme magnitudes of vertical, horizontal and moment (VHM) loads on individual sleepers. Results from laboratory experiments, on the pre-failure behaviour of the sleeper to ballast base contact area, show that lateral load/deflection behaviour is load path dependent and relations are determined for improved computer modelling of the sleeper/ballast interface. Further test results are used to establish the failure envelopes for combined VHM loading of the sleeper/ballast base contact area. Tests show that the sleeper/ballast base resistance at failure occurs at a load ratio (H/V) of about 0.45 (24°) at 2 mm of displacement tending to 0.57 (30°) at greater displacements. In addition, measurements from pressure plates within the testing apparatus are used to describe the development of confining stress within the ballast during 100 cycles of vertical load. The development of confining stress is assessed with reference to a finite element model of the laboratory apparatus and it is shown that the earth pressure ratio moves towards the active condition for peak load and the passive condition at minimum load per cycle. The contribution to lateral resistance of the crib ballast and varying sizes of shoulder ballast is also established and it is found that the shoulder and crib resistance can best be characterised by taking the mean resistance over a range of deflection from 2 mm to 20 mm. Calculations are presented, supported by the experimental data, to quantify the resistance from different sizes of shoulder ballast and a chart is presented which can be used as the basis for shoulder specification in practice.

It has been desirable for years to develop non-intrusive/non-invasiveprocedures to determine the pressures and stresses at various levels andinterfaces in the railroad track structure in order to optimize track designs andimprove subsequent track performance. Recent research has developedsatisfactory procedures for measuring pressures in the track structure at theballast/subballast/subgrade levels using earth pressure cells. The researchreported in this thesis documents the development of a technique for measuringthe pressures in the track, at the rail/tie plate/tie interfaces, using a very thinpressure sensitive Tekscan sensor. The Tekscan Measurement System uses asensor composed of a matrix-based array of force sensitive cells, similar to ministrain gauges, to obtain accurate pressure distributions between two surfaces inthe track. This thesis specifically describes: 1) the optimum procedure to installthe sensors into the track, 2) the recommended practices to effectively collectdata with the software, and 3) the accepted techniques for analyzing the results.Both laboratory calibration and in-track testing have been conducted and theresults are presented. The findings attest to the usefulness and practicality of theprocedure for accurately measuring pressures in railroad tracks. The proceduremay also be applicable for a wide variety of specific track related measurementssuch as validating curve geometric criteria, assessing crossing diamond impactpressures, and evaluating the advantages/disadvantages of various types of tieplates, fastenings and tie compositions.

This research study has concentrated on the invest~gation -of 1067 mm gauge railway track in order to provide optimum track standards. In addition an improved understanding has been obtained of the quasi-static and dynamic force levels exerted on the track structure and the indi victual track elements. The performance of resilient rail pads in attenuating dynamic stresses in concrete sleepers and the rail has been quantified. Rail head wear limits have been recommended for 1067 mm gauge track for a range of axle loads and train speeds. Significant potential savings of over $Al. 5 million per annum have been identified for the Queensland Railways with the adoption of these limits. In conjunction with these derived rail wear limits specific rail wear relationships have been determined, which allow more effective economic assessment of rail selection and in service life prediction. The track buckling stability of a range of 1067 mm gauge track structures have been quantified ahd recommendations made for rail length versus track curvature.

Ballasted track represents by far the most used infrastructure for railway transportation system, its main benefits being the relatively low construction costs, the maintainability, the relatively high damping capacity, noise absorption and high flexibility, the self-adjusting properties and high hydraulic conductivity. These are related to the structure of ballast layer as assembly as well as to particle properties. However, the unbound nature of ballast layer is also responsible for the reduction of geometric quality of the track, and therefore, its safety and ride comfort. The passage of trains causes cyclic movements of the unbound particles that result in permanent vertical and lateral deformations. For this track form, vertical settlement of granular layers and ballast particles degradation represent the major problems, affecting frequency of maintenance and track durability. In this context, reducing minor and major maintenance frequency while effectively using available resources by developing innovative technologies is a challenge for current and future railway research. After reviewing the most relevant existing solutions to improve ballasted track-bed behaviour and main factors affecting their performance, the aim of this research was to investigate the possibility of stabilising ballast with bitumen emulsion, as novel solution to slow down the loss in track quality associated with ballast settlement and particle degradation. In this regard, firstly the feasibility of the proposed alternative and main factors affecting its performance have been assessed through model-scale testing (small-scale Precision Unbound Material Analyser - PUMA). Results showed a good potential for this technology to reduce both the short-term and the long-term permanent deformation. It was also observed that bitumen stabilisation could modify mechanical properties due to the presence of a viscoelastic component (bitumen). The type of emulsion and its dosage played important roles in BSB properties: increasing the dosage of bitumen emulsion provided a better resistance to permanent deformation; increasing the viscosity of bitumen emulsion decreased the percentage of material lost, thereby providing improved stabilisation efficiency. Thus, depending on the field condition a specific bitumen emulsion could be designed to obtain the desired results in terms of BSB behaviour and stabilisation efficiency. At the same time, the use of harder bitumen for BSB seemed to improve the resistance to permanent deformation while polymer modification provided a more stable behaviour over time. Model-scale results provided important guidance on the influence of the factors analysed on the proposed technology. Nevertheless, to understand to what extent BSB could represent a solution to improve sustainability and performance of ballasted track-beds, findings had to be verified at full scale. Thus, full-scale box tests have been employed to assess how this technology could be effectively applied to existing ballasted tracks during maintenance operations and to investigate the practicability and maintainability of the presented technology. Results showed that bitumen stabilisation was more effective when applied at an early stage of ballast life (clean ballast), especially when coupled with tamping, providing a significant decrease to permanent deformation and to deformation rate (long-term behaviour). Nonetheless, in comparison with results obtained at model-scale, a slightly different behaviour of BSB in relation to unbound material was observed. Thus, with the aim of correlating previous model-scale PUMA and full-scale ballast box findings and evaluating long-term performance, full-scale PUMA testing was carried out. Results on clean ballast indicated that scale factor instead of the test type was the main factor controlling the effectiveness of Bitumen Stabilised Ballast (BSB) in terms of permanent deformation reduction. On the other hand, results obtained when using lower size aggregate confirmed that increasing the number of contact points increases also the influence of viscoelastic properties given by the bitumen, indicating that the use of different gradations combined with higher dosages (and types) of bitumen emulsions, could potentially modify full-scale track-bed mechanical properties. Key findings obtained from laboratory experiments, consistently showed evidence of the fact that bitumen stabilisation can reduce number of maintenance interventions due to geometry corrections and excessive particle degradation. In this regard, to estimate the environmental and economic impacts of BSB, a performance-based integrated model was developed to predict maintenance strategies of proposed technology in comparison to traditional ballast. This model, by combining the evolution of track irregularities with traffic and the level of contamination of ballast, allowed evaluation of the timing of corrective maintenance activities. Based on these, life-cycle environmental and economic costs of these alternatives have been carried out. Life Cycle Assessment (LCA) results showed that BSB is overall more sustainable than traditional ballasted track, only when considering also its impact on major maintenance operations. Sensitivity analysis carried out showed that BSB advantages are generally higher when the tolerance on the track quality level increases and with heavy traffic lines. LCCA results showed that BSB can provide important savings with respect to traditional ballasted track-bed. Sensitivity analysis showed that BSB would be more profitable for important and congested lines rather than peripheral ones. The influence of carbon conversion factor on results is relatively low while decreasing the discount rate corresponds to higher savings provided by the BSB. Overall, both LCA and LCCA results showed that BSB could offer a more sustainable solution from a life cycle perspective than traditional ballasted track-bed.

Track deterioration has a serious influence on the safety and efficiency (speed restriction) of train operations. Many expensive, disruptive and frequent repair operations are often required to maintain the ballast characteristics due to the problem of settlement. Because of this, a geogrid solution that has proved to be a simple and economical method of reinforcing track ballast is widely used. This project presents an evaluation of the behaviour of geogrid-reinforced railway ballast. Experimental large box pull-out tests were conducted to examine the key parameters influencing the interaction between ballast and the geogrid. The experimental results demonstrated that the triaxial geogrid with triangular apertures outperforms the biaxial geogrid with square apertures and the geogrid aperture size is more influential than rib profile and junction profile. The discrete element method (DEM) has then been used to model the interaction between ballast and geogrid by simulating large box pull-out tests and comparing with experimental results. The DEM simulation results have been shown to provide good predictions of the pull-out resistance and reveal the distribution of contact forces in the geogrid-reinforced ballast system. The discrete element method has also been used to simulate cyclic loading of geogrid-reinforced ballast under confined and unconfined conditions. For the confined condition, box tests have been simulated on unreinforced samples and reinforced samples with different geogrid positions and geogrid apertures. The response of the ballast layer reinforced with geogrid under repeated loading agrees with experimental results. It was found that the optimum location of geogrid is 100 mm depth from base, and the triaxial geogrid outperforms biaxial geogrid. For the unconfined condition, cyclic loading of a trough of ballast has also been simulated, and the sample with the geogrid at 50mm from the sub-ballast layer performs best. It was also found that the used of two geogrids at both 50mm and 150mm from the sub-ballast gave a smaller settlement than using a single layer geogrid, or the unreinforced ballast. The geogrid reinforcement limits the lateral displacement in reinforced zone, which is approximately 50mm above and below the geogrid. Previous investigations have shown that the abrupt stiffness change in track support is often associated with accelerated rates of deterioration of track geometry, high maintenance demand, and poor ride quality. However, at present, there is no detailed understanding of the mechanisms of track geometry deterioration at transition zones. This work provides insight into the factors that can cause or accelerate track degradation at the transition zones, in order to identify and evaluate appropriate mitigation design. A simple track transition model with dimensions 2.1m x 0.3m x 0.45m was simulated by using PFC3D. In order to identify and evaluate appropriate mitigation methods, two kinds of transition patterns, including a single step change and a multi step-by-step change for subgrade stiffness distribution were tested. The influence of the train direction of travel and speed on the transition were also investigated. In addition, geogrid was used in the ballast layer to examine the effects of geogrid reinforcement.

The only commercially operating magnetically levitated (maglev) transport system in the world is the link between Birmingham International Airport and the National Exhibition Centre. Comparative financial analysis for this route showed that the construction costs for both wheeled and maglev systems were similar and that the cost of the guideway accounted for over 70% of the total. In part this was because the guideway was elevated; a likely requirement for any future urban system. A substantial reduction in installation costs for a system of this nature can only be achieved by the use of cheap, lightweight and flexible guideways. The British Rail Research maglev vehicle was designed for use on a rigid guideway and it was known that excessive flexibility would make the suspension control system unstable. The aim of the study was to develop a maglev suspension control strategy that was insensitive to guideway flexibility. Vibration measurements were carried out on the Birmingham guideway to establish its modal properties. It was found to be sufficiently rigid to allow the existing controller to work without problems .Measurements were also made on the guideway of a Swiss cablecar transit system. This was felt to represent the extremes of both lightness and flexibility and established the range of guideway dynamics that were likely to be encountered. For the initial experimental work, a section of the British Rail maglev test track was modified to incorporate three sections of flexible track. A personal computer was installed on board the vehicle and software was written to aid frequency response testing and dynamic system modelling. Tests were carried out to establish the dynamic parameters of the new sections of guideway. The existing rigid guideway controller separated magnet control from suspension control. Guideway flexibility destroys this separation and induces additional feedback terms that degrade system stability. Theoretical studies of an improved controller took advantage of the fact that that the suspension magnets act directly onto the guideway and affect the position of both vehicle and guideway. As the guideway is lightly damped it is only flexible over a narrow bandwidth and the new suspension controller is able to use vehicle inertia to react forces that control the guideway at its natural frequency. Theory suggested that this would restore the separation of magnet and suspension control even with a flexible guideway. For a variety of reasons, experimental implementation of the new controller proved to be difficult. Suspension performance on the flexible portions of the guideway was never adequately demonstrated. The work did however enable a very accurate theoretical model of the system to be developed. This model contrasted with earlier predictions because, on rigid guideways, it predicted substantially smaller phase margins than the earlier models had suggested. It showed that the new controller had only modest benefits relative to the original rigid guideway suspension controller. This led to the development of an improved controller, a "lumped" controller where magnet and suspension control are not separated. Modelling for a single degree of freedom vehicle on a single mode guideway showed that large improvements in suspension performance could be made. Further modelling of a three degree of freedom vehicle and a five mode three degree of freedom flexible guideway used parameters that represent the production vehicles at Birmingham. This work defined limits for guideway flexibility and vehicle dynamic performance and showed that maglev guideways for production scale vehicles, with the "lumped" controller, can be very flexible indeed. The major aim of the project was achieved. A suspension controller was developed that will allow a maglev vehicle to work on a guideway that is far lighter, more flexible and far cheaper than the guideway required for a conventional wheeled vehicle.

The development of Discrete Element Model (DEM) of railway ballast for the purpose of studying the behavior of ballast particles during tamping is addressed in a simulation study, with the goal of optimizing the railroad tamping operation. A comprehensive literature review of applicability of DEM techniques in modeling the behavior of railway ballast is presented and its feasibility in studying the fundamental mechanisms that influence the outcome of railroad tamping process is analyzed. A Discrete Element Model of railway ballast is also developed and implemented using a commercially available DEM package: PFC3D. Selection and calibration of ballast parameters, such as inter-particle contact force laws, ballast material properties, and selection of particle shape are represented in detail in the model. Finally, a complete tamping simulation model is constructed with high degree of adjustability to allow control of all process parameters for achieving realistic output. The analysis shows that DEM is a highly valuable tool for studying railroad tamping operation. It has the capability to provide crucial and unprecedented insights into the process, facilitating not only the optimization of current tamping practices, but also the development of novel methods for achieving sustainable improvements in track stability after tamping in the future. Different ways of modeling particle shapes have been evaluated and it has been shown that while using spheres to represent irregular ballast particles in DEM provides immense gains in computational efficiency, spheres cannot intently capture all properties of irregularly shaped particles, and therefore should not be used to model railway ballast particles. Inter-particle and wall-particle contact forces are calculated using Hertzian contact mechanics for determining ballast dynamics during tamping. The results indicate that the model is able to accurately predict properties of granular assemblies of the railway ballast in different test cases. The developed model for simulating tamping operation on a half-track layout is expected to be extended in future studies for evaluating rail track settlement and stability, optimization of tamping process, and performance of different ballast gradations.<br>MS

The accuracy of the results from a rail vehicle dynamic model is dependent on the realism of the track input to the model. An important part of the track input is the irregularities that exist on actual track. This study analyzes the irregularities inherent in railroad track geometry data, and provides an analytical method for creating track data with the irregularities for use as the input to a dynamic model. Track data, measured from various classes of track, was examined using statistical and frequency analysis techniques to identify any similarities in the characteristics of the irregularities. The results showed that each class of track had a distinctive value for the standard deviation of the alignment and profile data. It was also determined that the frequency content of all the tracks was contained within a common bandwidth. The track irregularities could then be generated with the same characteristics as an actual track. The method for creating the track irregularities was then programmed into TRAKVU. TRAKVU is a track preprocessor used in conjunction with NUCARS, a railcar dynamic modeling program¹. TRAKVU enables users to create track data and apply the appropriate irregularities so that the track will have the characteristics of the desired class of track. A validation was then performed to determine how well track created in TRAKVU simulated actual tracks. The statistical and frequency characteristics of created tracks were compared directly with actual tracks. Created track was also used as the input to a dynamic model. The predicted vehicle response was then compared to the actual vehicle response and the predicted vehicle response using measured track data as the input. The results from the validation showed that the created track performed as well as the measured track in providing the input to the model. Although the predicted response using the created track did not compare as well with the actual vehicle response, the differences could be attributed to inaccuracies in the model. ¹NUCARS and TRAKVU are copyrighted property of the Association of American Railroads.<br>Master of Science

Railways are integral to the transportation system of a growing economy. There is a constant demand by numerous stakeholders of the railway industry for greater train operational speeds, tonnage, passenger comfort and safety with minimal service disruptions. This is partly achievable through the improvement of the main components of railway track. A fundamental requirement for any railway track is to be able to maintain its as-built geometry over its service life. Settlement of a ballasted railway track is mainly caused by cyclic loading due to the passage of traffic. To return the rail track to the as-built alignment and level, track maintenance needs to be carried out. Tamping is one of the most common and traditional ways of maintaining the track and is not only costly but causes interruption to the day-to-day operations and damages the long term performance of the ballasted track. It therefore remains important to policy makers, rail practitioners and researchers to identify new techniques, innovations or processes that will prolong intervals between scheduled track maintenance. Track settlement is influenced by several interrelated track variables, not least of which are the railway sleeper, ballast and ballast-sleeper interface that have potential for alteration to be optimised with respect to the track performance. In this research, results are presented from a parametric experimental study using three different apparatus namely box test (confined), Composite Element Test (CET) (semi-confined), and Railway Test Facility (RTF) (full-scale), to investigate performance of different sleeper and ballast configurations. The box test and the CET apparatus were used ahead of the RTF (full-scale) apparatus as preliminary tests to obtain an insight into the performance and potential benefits of different sleeper types with and without the use of Under Sleeper Pads (USPs). The aforementioned apparatus were also used for comparison with the full-scale apparatus to assess the consistency of the sleeper settlement results (phase 1 tests). The purpose of using the box test and CET apparatus was also to allow a relatively large number of simplified tests to be carried out on sleeper and ballast combinations (Phase 2 tests) within a reasonable cost and time frame. Phase 2 tests were designed and conducted with consideration of the phase 1 test results. The test results from phase 1 showed that increasing the number of contact points between ballast particles and sleeper, and increasing the coefficient of friction at ballast-sleeper interface improved the settlement performance of the tarckbed. Therefore, having this in mind, further tests were designed and conducted including: finer ballast grading, two-layered ballast systems, frictional sleepers and USPs, and USP types with various stiffnesses. In addition, further tests on ballast bonding/gluing and ballast reinforcement were conducted with the aim of investigating possible ways of minimising ballast bed deterioration. Application of ballast gluing was proven beneficial (in literature) in improving ballast bed performance, however, the overall cost of super glues used for this method was high. Therefore in this study, a low cost glue was introduced and its performance was tested under conditions similar to real track. With regard to ballast reinforcement, the expanded polystyrene was added to the ballast sample with the aim of decreasing the contact forces between ballast particles and consequently minimising ballast bed deterioration and settlement. The observations in this study sought to establish qualitative and quantitative data on the effects of different parameters on the track performance, which may lead to a longer service life with less maintenance. The results showed that the type of sleeper has an influence on the performance of a railway track. With respect to settlement performance of a railway track, sleepers with higher depth and width, coefficient friction, and bending stiffness performed better. Out of all investigated sleeper types without any additional interventions, concrete mono-block gave the least settlement and the plastic sleeper gave the most. It was also found that inclusion of USPs (regardless of type) can be beneficial compared to the ‘no USP’ scenario in: (1) Increasing trackbed resiliency. (2) Reducing maintenance works related to settlement. (3) Reducing sleeper deflections (hogging) at the middle of sleeper. (4) Reducing the rate of deterioration of sleeper support at the rail seat (6) Reducing differences in the performance of different sleeper types. (7) Reducing tendency towards centre binding. (8) Reducing transmitted pressure on subgrade. (9) Making the trackbed stiffness more uniform. The conclusion of research was that use of concrete mono-block sleeper, USPs, finer ballast grading, a two-layered ballast system with finer ballast grading on top, frictional sleeper, frictional USP, and ballast gluing all have potential to improve the performance of ballasted railway track and reduce the maintenance requirements.

Thesis (M.S.)--West Virginia University, 2003.<br>Title from document title page. Document formatted into pages; contains xiv, 158 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 141).

For application in damping treatments, elastomeric materials should have a high damping loss factor, but this is inevitably linked to a strong temperature-dependence of the dynamic properties. A methodology is developed that allows a material to be formulated for a particular damping application where temperature-dependence has to be taken into account. The methodology is applied to the case of a tuned absorber system used for damping the vibration of a railway track. This is required to be effective over a temperature range -20°C to 40°C. To investigate the effect of the temperature on the performance of a rail damper, a simple Timoshenko beam model of the track vibration is used, to which are added single-frequency and dual-frequency tuned absorbers. The results show that a high noise reduction can be achieved for the optimum stiffness, provided that the loss factor is between about 0.25 and 0.4. In order to study the generic effects of high damping versus constant stiffness, the time-temperature superposition principle is used to convert frequency-dependence to temperature-dependence for a notional material with constant loss factor. This is used in the prediction of decay rates and thereby noise reduction. In addition, a weighted noise reduction is studied by using measured rail temperature distributions. This temperatureweighted noise reduction allows a single number measure of performance to be obtained which can be used to assess various elastomeric materials in order to determine the optimum material for a given situation. Two types of viscoelastic material, butyl and EPDM rubbers with various amount of fillers and plasticisers are investigated. The properties of both rubbers have been measured over the range of temperatures for frequencies 300-3000 Hz. For this a test rig had to be modified. For butyl, the best combination of filler and plasticiser gives temperature weighted noise reductions up to 5.9 dB(A). Butyl rubber is suitable for use in the rail absorber giving high noise reductions between 0°C and 40°C. The best EPDM compound gives a temperature-weighted noise reduction up to 6.2 dB(A). Comparing these two rubbers, EPDM is more suitable for low temperatures below 10°C and butyl is more suitable for higher temperatures above 10°C.

There has been a worldwide trend to increase axle loads and train speeds. This means that railway track degradation will be accelerated, and track maintenance costs will be increased significantly. There is a need to investigate the consequences of increasing traffic load. The aim of the research is to develop a model for the analysis of physical degradation of railway tracks in response to changes in traffic parameters, especially increased axle loads and train speeds. This research has developed an integrated track degradation model (ITDM) by integrating several models into a comprehensive framework. Mechanistic relationships for track degradation hav~ ?een used wherever possible in each of the models contained in ITDM. This overcc:mes the deficiency of the traditional statistical track models which rely heavily on historical degradation data, which is generally not available in many railway systems. In addition statistical models lack the flexibility of incorporating future changes in traffic patterns or maintenance practices. The research starts with reviewing railway track related studies both in Australia and overseas to develop a comprehensive understanding of track performance under various traffic conditions. Existing railway related models are then examined for their suitability for track degradation analysis for Australian situations. The ITDM model is subsequently developed by modifying suitable existing models, and developing new models where necessary. The ITDM model contains four interrelated submodels for rails, sleepers, ballast and subgrade, and track modulus. The rail submodel is for rail wear analysis and is developed from a theoretical concept. The sleeper submodel is for timber sleepers damage prediction. The submodel is developed by modifying and extending an existing model developed elsewhere. The submodel has also incorporated an analysis for the likelihood of concrete sleeper cracking. The ballast and subgrade submodel is evolved from a concept developed in the USA. Substantial modifications and improvements have been made. The track modulus submodel is developed from a conceptual method. Corrections for more global track conditions have been made. The integration of these submodels into one comprehensive package has enabled the interaction between individual track components to be taken into account. This is done by calculating wheel load distribution with time and updating track conditions periodically in the process of track degradation simulation. A Windows-based computer program ~ssociated with ITDM has also been developed. The program enables the user to carry out analysis of degradation of individual track components and to investigate the inter relationships between these track components and their deterioration. The successful implementation of this research has provided essential information for prediction of increased maintenance as a consequence of railway trackdegradation. The model, having been presented at various conferences and seminars, has attracted wide interest. It is anticipated that the model will be put into practical use among Australian railways, enabling track maintenance planning to be optimized and potentially saving Australian railway systems millions of dollars in operating costs.

The pressure distribution at the ballast-tie interface of railroad track plays a key role in overall track support. Failure of the ballast or tie can result from excessive loads that were not designed for, requiring increased maintenance and reducing railroad operating efficiency. Understanding the forces acting on the ballast and tie are required to design higher performance and longer lasting track. To further this understanding, the use of Matrix Based Tactile Surface Sensors (MBTSS) is employed to measure the actual pressure distribution at the ballast-tie interface, characterized by individual ballast particle contact points and non-uniform pressures. The research explores this application of MBTSS including the development of sensor protection and calibration procedures. Results from laboratory ballast box testing conducted at the Transportation Technology Center, Inc. (TTCI) are presented. Conservative estimates of peak pressure under a typical wheel load on new ballast averaged 1450 psi and on fouled ballast averaged 680 psi. Contact areas varied across the range of ballast gradations and are shown to increase under increased applied load. A parameter to describe the "roughness" of the ballast-tie pressure distribution is offered. Results from in-track testing performed at TTCI, including pressure distributions along ten test ties, are also presented.

A method for numerical simulation of train induced track vibration and wave propagation in subgrade has been proposed. The method uses a mass to simulate the bogie of a train and considers the effect of rail roughness. For this method, rail roughness is considered as a randomly generated signal and a filter is used to block the undesired components. The method predicts the particle velocity around the track and can be applied to many kinds of railroad trackbeds including traditional ballast trackbed and modern Hot mix asphalt (HMA) trackbed. Results from ballast and HMA trackbeds are compared and effects of HMA layer on damping track vibration and dissipating wave propagation are presented. To verify the credibility of the method, in-track measurements were also conducted. Site measurements included performing geophysical tests such as spectral analysis of surface wave test and seismic refraction test to determine the subsurface conditions at the test site. Ballast and HMA samples were tested in the laboratory by resonant column test to obtain the material properties. Particle velocities were measured and analyzed in the frequency domain. Results from in-track tests confirm the applicability of the numerical method. The findings and conclusions are summarized and future research topics are suggested.

At present, high speed dual purpose rail/road vehicles employing fixed non-destructive testing (NDT) sensors are used to inspect rails. Due to the uncertainties in characterisation of the defects when they are detected at high speed, manual re-visiting of the defects by expert operators is required before any decision regarding track maintenance is made. This research has been driven by a desire from the rail industry for a robotic system performing faster than human operators and being capable to both detect and characterise rolling contact fatigue (RCF) cracks in rails with the aim of automating the existing manual inspection and enhancing its accuracy and reliability. This thesis combines expert systems technologies with robotic NDT to fulfil this aspiration. A great deal of effort has been spent to develop a robotic inspection trolley which can automatically detect and characterise the RCF cracks in rails using an alternating current field measurement (ACFM) sensor. It uses a rule based expert system (RBES) proposed to control the robotic trolley and more importantly process ACFM data for both detecting and sizing defects. The developed system can detect the possible presence of defects in railway tracks at high speed pass (5-20 km/h) and can automatically return to an identified defect location to perform a slower and more detailed scan (up to 20 mm/s) across a rail section to determine the size, depth and number of cracks present in that section.

Thesis (MScEng)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: The Tubular Track (TT) railway system is a twin beam modular railway system consisting of two reinforced concrete (RC) beams on which steel rails are continuously supported. The beams are linked with galvanised steel gauge tie bars and continuously supported by soil foundations, and can be used to replace conventional sleeper and ballast railway support. The TT railway system has in the past been analysed with various analysis methods, but were found to obtain con icting results. The con icting results means that one of the analysis methods used for the analysis and design of TT railway sections is either an underestimation or overestimation of section displacements, forces, and stresses; or both methods could even be incorrect. The main emphasis of this investigation is therefore to develop and verify static and dynamic analysis methods and modeling techniques which can be used to simulate the TT railway system accurately. The results and models of the previous analyses are not explicitly investigated in this dissertation, but serve as a motivation for this investigation. The TT system is supported by several soil strata providing vertical support, but geometrically modeling the subgrade strata in the analysis models adds a high level of complexity, and is not feasible for general analysis where soil conditions are mostly unknown. The elastic foundation theory is therefore used to accurately simulate the interaction between beam and foundation and therefore su ciently simpli es the analysis models. Simpli cation of a subgrade foundation by simulating a soil sti ness supporting the TT beam is investigated and analysed by comparing nite element analysis (FEA) results of various soil models using parameters of four known soil formations currently in use at TT railway sections. The FEA of the subgrade formations indicates that there is a linear relationship between the modulus of subgrade reaction for a square plate bearing test and a rectangular, in nitely long plate representing the subgrade support for the TT beams. A square plate bearing test can therefore be performed on site and modi ed to represent the actual subgrade support sti ness of the TT railway structure, whereafter it can be used for the analysis and design of the TT system using one of the proposed analysis methods. The analysis models used range from simple theoretical models based on elastic foundation principles, to two-dimensional (2D) beam elements, and ultimately to complex three-dimensional (3D) solid nite element models. The models used for the analyses are the Single and Double Beam elastic foundation, PROKON 2D beams, ABAQUS 2D beams and ABAQUS 3D solid element models. The alternative analysis methods considered should provide a clear indication of which analysis methods are accurate and feasible for design of the TT system. An in-situ reference model with known de ections and design parameters speci c to a TT railway section is used to analyse the di erent analysis methods' accuracy and validity. The Double Beam, ABAQUS 2D and ABAQUS 3D models were found to provide very similar displacements, bending moments and shear forces for a static analysis, whereas the PROKON and Single Beam models provide unsatisfactory results. The PROKON beam model underestimates the bending moments and shear forces in the rail, and overestimates bending moments and shear forces in the RC beam by a considerably margin. This result can lead to the underdesigning of the rail which could possibly force the RC beam to be subjected to larger maximum bending moments and shear forces than for what it was originally designed for, thereby nullifying or possibly even exceeding the amount for which it was overdesigned. This e ectively accelerates material fatigue, which might be the possible cause of the small cracks in the RC beams which have been found on some TT railway sections, which is currently being investigated. A graphical user interface of the Double Beam method is provided for quick and e cient analysis. Empirical methods used to simulate the dynamic nature of a railway system are often used in the industry to simplify the dynamic loading by determining a dynamic amplitude factor (DAF) to be applied to a static load. An implicit dynamic FEA is therefore performed to obtain the DAF for the reference section, which is subsequently used for the comparison with in-situ de ection results. The results of dynamic analysis validates the proposed empirical analysis method, as the displacements obtained were very similar to actual eld test results, thereby also verifying the accuracy of the proposed analysis methods. The sensitivity of the TT system to design parameters is also investigated to indicate to which parameters the design is sensitive to and where small variations of these parameters require due consideration for future and analysis of the TT railway system.<br>AFRIKAANSE OPSOMMING: Die Tubular Track (TT) spoorweg stelsel is 'n dubbel balk modulêre treinspoor sisteem bestaande uit twee gewapende beton balke waarop staal spore voortdurend ondersteun word. Die balke word gekoppel deur gegalvaniseerde staal stawe vir laterale styfheid en word deurlopend ondersteun deur grond fondamente, en kan gebruik word om konvensionele dwarslêer en ballast spoorweg ondersteuning te vervang. Die TT spoorweg stelsel was in die verlede met verskeie analiseringsmetodes ontleed, maar het teenstrydige resultate gewerf. Die teenstrydige resultate beteken dat een van die analise metodes wat gebruik word vir die analisering en ontwerp van TT spoorweg seksies 'n onderskatting of oorskatting van verplasings, kragte, en spannings is; of beide metodes kan selfs verkeerd wees. Die hoofklem van hierdie ondersoek is dus die ontwikkeling en veri kasie van statiese en dinamiese analitiese metodes en modellering tegnieke wat gebruik kan word om die TT spoorweg stelsel akkuraat te simuleer. Die resultate en modelle van die vorige ontledings word nie uitdruklik in hierdie proefskrif ondersoek nie, maar dien as 'n motivering van hierdie ondersoek. Die TT stelsel word ondersteun deur verskeie grond strata wat vertikale ondersteuning verskaf, maar meetkundige modellering van die grond strata in die ontledingsmodelle veroorsaak 'n hoë vlak van kompleksiteit wat nie bruikbaar is vir algemene analises waar grondeienskappe meestal onbekend is. Die elastiese fondament teorie word daarom gebruik om die interaksie tussen die balk en die fondament akkuraat te simuleer, en vereenvoudig dus die analitiese modelle voldoende. Vereenvoudiging van 'n grond fondament deur 'n grond styfheid ondersteuning van die TT balk te simuleer is ondersoek en ontleed deur die resultate van eindige element analises van verskillende grond modelle te vergelyk. Bekende ontwerp parameters van vier bekend grondformasies wat tans gebruik word by TT spoorweg seksies word vir hierdie analises gebruik. Die eindige element analises van die grondformasies dui daarop aan dat daar 'n lineêre verwantskap tussen die modulus van grond reaksie vir 'n vierkantige plaat dratoets en 'n reghoekige, oneindige lang plaat dratoets bestaan. 'n Vierkantige plaat dratoets kan dus op terrein uitgevoer en aangepas word om die werklike styfheid van die grond ondersteuning van die TT spoorweg sisteem voor te stel. Die analitiese modelle wat gebruik word wissel van eenvoudige teoretiese modelle wat gebaseer is op elastiese fondament beginsels, twee-dimensionele (2D) balk elemente, asook komplekse driedimensionele (3D) soliede eindige element modelle. Die modelle wat gebruik is vir die ondersoek is die Enkel en Dubbel Balk elastiese fondament, PROKON 2D balke, ABAQUS 2D balke en ABAQUS 3D soliede element modelle. Hierdie reeks bied 'n duidelike aanduiding watter analiseringsmetodes akkuraat en haalbaar is vir die ontwerp van die TT stelsel. 'n In-situ verwysingsmodel met bekende de eksies en ontwerp parameters wat spesi ek is vir 'n TT spoorweg seksie word gebruik om die akkuraatheid en geldigheid van die verskillende analitiese metodes te analiseer. Die Dubbel Balk, ABAQUS 2D en ABAQUS 3D modelle verkry baie soortgelyke verplasings, buigmomente en skuifkragte vir 'n statiese analise, terwyl die PROKON en Enkel Balk modelle onbevredigende resultate verkry. Die PROKON model onderskat die maksimum buigmomente en skuifkragte in die staal spoor, en oorskat buigmomente en skuifkragte in die gewapende beton balk. Hierdie resultaat kan moontlik lei tot die onderontwerp van die staal spoor en dwing moontlik vir die gewapende beton balk om blootgestel te word aan groter buigmomente en skuifkragte as vir wat dit oorspronklik ontwerp is, en verontagsaam sodoende moontlik die kragte waarvoor dit oorontwerp is. Dit versnel e ektief materiaal vermoeiing, wat die moontlike oorsaak is van die klein krake wat gevind is in die gewapende beton balke op sommige TT spoorweg seksies wat tans ondersoek word. 'n Gra ese gebruikerskoppelvlak van die Dubbel Balk model is verskaf vir vinnige en doeltre ende ontleding. Empiriese metodes om die dinamiese aard van 'n spoorweg-stelsel te simuleer word dikwels gebruik in die bedryf om dinamiese belasting te vereenvoudig deur middel van die gebruik van 'n dinamiese amplitude faktor (DAF) wat op 'n statiese belasting aangewend word. 'n Implisiete dinamiese eindige element analise word dus uitgevoer om die DAF te ondersoek, wat daarna gebruik word vir die vergelyking met die in-situ de eksie resultate van die in-situ verwysingsmodel. Die resultate van die dinamiese analise bevestig dat die voorgestelde empiriese analise metode gebruik kan word, omdat die verplasings wat verkry baie soortgelyk was aan werklike veld toets resultate, en daardeur ook die veri ëring van die akkuraatheid van die voorgestelde analise metodes bewerkstellig. Die sensitiwiteit van die TT stelsel vir ontwerp parameters word ook ondersoek om aan te dui watter parameters die ontwerp voor sensitief is, en waar klein variasie in hierdie ontwerp parameters behoorlike oorweging vereis vir die toekomstige analisering en ontwerp van die TT spoorweg stelsel.

Uma nova abordagem de sistema de gerência de pavimentos ferroviários é exposta nesta tese. O objetivo principal da pesquisa foi o desenvolvimento de um sistema de gerência em nível de rede e análises do custo do ciclo de vida em nível de projeto, adotando como estudo de caso a Estrada de Ferro Vitória Minas. A revisão bibliográfica apresenta modelos de avaliação da qualidade geométrica e estrutural no Brasil e no mundo. O desenvolvimento iniciou-se com a composição do sistema de gerência em nível de rede utilizando um inventário do trecho em estudo, a subdivisão dessa via em segmentos homogêneos de comprimento variável de acordo com a geometria (curva e tangente), e a aplicação de seis códigos: (i) classe de via; (ii) inventário da estrutura do pavimento com base no tipo de dormente; (iii) geometria com a definição da metodologia de avaliação da qualidade geométrica, propondo um índice que aplica o desvio padrão dos parâmetros geométricos (bitola, empeno, alinhamento e nivelamento transversal), a contagem de exceções e os respectivos limites de alerta, intervenção e segurança; (iv) superfície pela análise do desgaste do trilho e defeitos superficiais; (v) segurança pelo coeficiente de atrito; e (vi) capacidade estrutural com a aplicação do módulo de via parametrizado pelo carro controle. A partir dos seis códigos, foi possível categorizar a estratégia de manutenção aplicável e, em nível de projeto, foram analisadas as degradações do lastro e do desgaste do trilho, com definições de equações de predição, o que permitiu simular o custo do ciclo de vida das estratégias. Por fim, para verificar a viabilidade técnica da estratégia de manutenção apontada, foram estudadas as tensões no topo do lastro e do subleito e ainda o módulo de via por retro análise das deflexões medidas da via permanente em duas seções da EFVM.<br>A new approach to the railroad track management system is presented in this thesis. The main objective of the research was the development of a network management system and life cycle cost analysis in a project level, adopting as a case study of the Estrada de Ferro Vitoria Minas. The bibliographic review has exposed geometric and structural track quality evaluation models in Brazil and in the world. The development began with the composition of the network management system using an inventory of the track under study, the subdivision of the railway into homogeneous segments of variable lengths depending on the geometry (curve and tangent), and the application of six codes: (i) class, (ii) pavement structure inventory based on tie type, (iii) geometry with definition of quality assessment methodology proposing an index that applies the exception counting and the standard deviation of the parameters - cross level, warp, alignment and gauge - and safety, alarm and intervention limits, (iv) surface by analysis of rail wear and rail surface defects, (v) safety by friction coefficient, and (vi) structural capacity with the application of the track modulus parameterized by the track geometry car. From the six codes, it was possible to categorize the applicable maintenance strategy at a project level, create prediction equations of the ballast and the rail wear degradation and simulate life cycle cost of the strategies. In order to verify the technical feasibility of the mentioned maintenance strategy, it was measured the stress at the top of the ballast and subgrade and the track modulus by retroanalysis deflections in two sections of the EFVM.

The primary focus of this research is evaluation of feasibility, applicability, and accuracy of Doppler Light Detection And Ranging (LIDAR) sensors as non-contact means for measuring track speed, distance traveled, and curvature. Speed histories, currently measured with a rotary, wheel-mounted encoder, serve a number of useful purposes, one significant use involving derailment investigations. Distance calculation provides a spatial reference system for operators to locate track sections of interest. Railroad curves, using an IMU to measure curvature, are monitored to maintain track infrastructure within regulations. Speed measured with high accuracy leads to high-fidelity distance and curvature data through utilization of processor clock rate and left-and right-rail speed differentials during curve navigation, respectively. Wheel-mounted encoders, or tachometers, provide a relatively low-resolution speed profile, exhibit increased noise with increasing speed, and are subject to the inertial behavior of the rail car which affects output data. The IMU used to measure curvature is dependent on acceleration and yaw rate sensitivity and experiences difficulty in low-speed conditions. Preliminary system tests onboard a 'Hy-Rail' utility vehicle capable of traveling on rail show speed capture is possible using the rails as the reference moving target and furthermore, obtaining speed profiles from both rails allows for the calculation of speed differentials in curves to estimate degrees curvature. Ground truth distance calibration and curve measurement were also carried out. Distance calibration involved placement of spatial landmarks detected by a sensor to synchronize distance measurements as a pre-processing procedure. Curvature ground truth measurements provided a reference system to confirm measurement results and observe alignment variation throughout a curve. Primary testing occurred onboard a track geometry rail car, measuring rail speed over substantial mileage in various weather conditions, providing high-accuracy data to further calculate distance and curvature along the test routes. Tests results indicate the LIDAR system measures speed at higher accuracy than the encoder, absent of noise influenced by increasing speed. Distance calculation is also high in accuracy, results showing high correlation with encoder and ground truth data. Finally, curvature calculation using speed data is shown to have good correlation with IMU measurements and a resolution capable of revealing localized track alignments. Further investigations involve a curve measurement algorithm and speed calibration method independent from external reference systems, namely encoder and ground truth data. The speed calibration results show a high correlation with speed data from the track geometry vehicle. It is recommended that the study be extended to provide assessment of the LIDAR's sensitivity to car body motion in order to better isolate the embedded behavior in the speed and curvature profiles. Furthermore, in the interest of progressing the system toward a commercially viable unit, methods for self-calibration and pre-processing to allow for fully independent operation is highly encouraged.<br>Ph. D.

Effective maintenance of railway track is critical for the safe operation of any railway network. Efficient maintenance may also result in economic benefits for rail operators. The work in this thesis looks into how an inexpensive measurement system could be fitted to in-service railway vehicles such as commuter trains, to provide a relatively high frequency of measurement on their routes of operation, when compared to dedicated measurement vehicles. This thesis describes how a prototype inertial measurement system was designed and built, and fitted to a commuter train operating in the region south of London, UK. Inertial data is processed to provide a vertical profile of the track. A novel use of a modified Bryson-Frazier filter is used to produce vertical profile datasets which are repeatable to within 0.2 mm. Profiles calculated from multiple passes of the same areas of track are compared to show track degradation. Methods of estimating track stiffness are developed using vertical geometry data from repeated passes of the same track sections at differing speeds. Some correlation to stiffness is shown through the results, but exact measurements were not possible. Finally, two case studies are presented which show findings at a bridge approach, and through two level crossings.

In the design of rail track structures where the subgrade cannot achieve the desired capacity, enabling the required standard of track geometry to be maintained for the speed, axle load and tonnage to be hauled, a capping layer of granular material is placed between the natural ground or the embankment fill material and the ballast to protect the underlying weaker layers. In spite of the important role played by the capping layer, very little research has been carried out on its performance. The current practice of design of the capping layer, therefore, is based on working stress philosophy where reduced levels of stresses are assumed not to degrade the subgrade. Even on tracks containing a thick ballast layer that ensures allowable levels of working stress the subgrade has been found to have permanently deformed. Design of capping layers based on plastic deformation, therefore, appears appropriate. This thesis aims at determining the load levels that cause detrimental plastic deformation in the capping layer. The suite of material properties that characterise plastic deformations of capping layer is neither readily available nor easily determined. This thesis proposes a cheaper method of evaluating a range of capping layer material properties using penetration tests on specimens contained in California Bearing Ratio (CBR) test moulds coupled with a finite element modelling based back calculation technique. The suite of material properties thus determined are used for the simulation of the behaviour of capping layers under the boundary and loading conditions similar to those in practice. The predicted results are validated using laboratory experiments on large size capping layer specimens.

The research described in this dissertation centres on the application of a discipline of formal methods in railway signalling system design. A generic abstract model of railway track networks and signals has been developed in Higher-Order Logic(HOL). It consists of several theories arranged in a hierarchy. Railway track networks are modelled by a class of constraint labelled directed graphs. HOL theories of graphs and paths have been developed for representing track networks. HOL theories modelling individual track components and signals have also been developed. These theories are then combined to create a theory of track network. Three applications of this model are described. The first is a network verifier which verifies a formal specification of track layout against its abstract model by proving theorems automatically. The second application is to extract information from the specifications and to create control tables automatically. Lastly, a method of modelling the interlocking processor using finite state machines is described. Although this research has centred on railway signalling, it can be viewed as a case study of how to apply formal methods in the analysis and design of safety- critical systems. The approach and methods used can be generalized in order to be useful in other industries.

Because the operational characteristics of signalized intersections near highway-railroad grade crossings (IHRGCs) are different from those of signalized intersections located elsewhere in the traffic system, standard operational strategies do not apply. This is because safe operation at IHRGCs takes precedence over all other objectives. Because the prime objective of the current preemption methods is to clear the crossing, secondary objectives such as safe pedestrian crossing time and minimized delay are given less consideration or ignored completely. Consequently, state-of-the-practice strategies may cause serious pedestrian safety and efficiency problems at IHRGCs. Therefore, there is a definite need for research on how to improve traffic signal preemption strategies. An important element of preemption strategy is detection of trains and prediction of arrival times. However, because of the limitations of current detection technologies, estimation algorithms, etc., there is a wide range in these warning times. In this dissertation, a new train-arrival prediction algorithm was developed using detection equipment located farther upstream from the HRGC. The state-of-the-art transition preemption strategy (TPS) was developed to ensure that as preemption is initiated by approaching trains, the signal display does not change in a manner that endangers either pedestrians or drivers. However, because it does not account for the variability of predicted train arrival times, there is still a possibility of failure. Therefore, a new transition preemption algorithm that is specifically designed to improve intersection performance while maintaining or improving the current level of safety is developed. This dissertation developed a preemption strategy (TPS3) that uses better train arrival time estimates to improve the safety and efficiency of IHRGCs. The approach was simulated on a test bed in College Station, Texas, and it was concluded that the new TPS improves the safety and operation of intersections near highway-railroad grade crossings.

In American rail operations, rails fail due to the combined effects of rail wear due to repetitive wheel contact and the growth of surface and sub-surface cracks and flaws. Rail maintenance includes frequent uncoupled wear and ultrasonic inspections that determine the amount of wear that the rail has undergone and the presence of cracks and flaws. A rail is removed from service when its wear reaches a pre-determined wear limit or a flaw is detected in its cross section. In rail research, the life of a rail is typically estimated using fracture mechanic or fatigue methods and an assumed flaw geometry. Multiple models ranging from complex elastic-plastic finite element models to simplified representations of a beam on an elastic foundation have been developed to predict the life of a rail. The majority of rail failure models do not incorporate rail wear into their analysis, and assume an unworn rail geometry. In order to account for rail wear, certain models adopt simplified rail geometries that uncouple rail wear into top-wear and side-wear. This thesis presents a rail failure model that describes the combined effects of rail wear and crack growth through the development of a functional relationship between input variables describing the geometry, loading, and material properties of a given rail and output variables describing the life characteristics of the rail. This relationship takes the form of multiple response surfaces estimating the desired output variables. Finite element models incorporating worn rail profiles and an assumed crack geometry corresponding to a detail fracture are combined to determine the state of stress and strain at the assumed flaw. Strain-life fatigue methods and fracture mechanic concepts are used to develop the output variables necessary to describe the life of the rail using the finite element model results. The goals of this research are to predict the remaining fatigue life and estimate the crack-growth rate of the rail based on the minimum number of geometry, loading, and material property independent variables. The outputs developed to describe the railâ s remaining life are intended to be used for the decision making for rail removal.<br>Master of Science

Track maintenance represents over 20 percent of Australian railway operating costs. Thus there is considerable incentive for rail corporations to reduce their maintenance costs. There is considerable research directed at improving track structures and maintenance techniques to reduce the track maintenance expenditure. However, there is little work on the planning of track maintenance that can be applied to Australian railway operations. This research reviews maintenance planning and finds that models currently available are empirical models reliant mainly on historical track condition data from specific rail organisations. No such models are yet in use Australian railway operations. Leading models utilise expert systems to decide maintenance activities rather than optimise the net benefits of maintenance. As such, these models are ineffective at assessing what if scenarios of changed track operating conditions. Internationally, current maintenance practice is to plan maintenance on professional judgement without the use of models to aid decisions. Currently, only a minority of larger rail corporations record sufficient track and maintenance data needed for maintenance planning modeling. A new track maintenance model has been formulated based on a mechanistic track degradation approach. This allows the model to operate without historical track maintenance condition data and hence utilise a minimal amount of track maintenance data. The model assesses the net benefit of maintenance by simulating the costs of planned and unplanned maintenance, as well as train operating costs as they are affected by track condition. A prototype computer program has been developed that has shown that the model is capable of assessing a cost efficient intervention level for tamping and resleepering maintenance. The model's independence from historical data means it is applicable to any rail operator and is capable of assessing what if scenarios on the impact of changed track, traffic or cost conditions. The model has been subjected to testing that has identified areas for its further development. These areas are the modeling of defective sleeper clusters and of sleeper ages, also the development and inclusion of a ballast degradation and maintenance sub-model. Further work for the developed prototype computer application include improving the program efficiency, expanding the number of iteration cycles used in the simulation and recording a track asset value during degradation and maintenance of the track

Railway tracks experience elevated rail deflections when the supporting soil is soft and/or the train speed is greater than approximately 50% of the wave propagation velocity in the track-soil system (i.e. the critical velocity). Such vibrations are undesirable, so soil replacement or soil improvement of the natural soil (or alternatively mini-piles or lime-cement treatment) is often used to increase track-ground stiffness prior to line construction. Although areas of existing soft subgrade might be easily identified on a potential new rail route, it is challenging to determine the type and depth of ground remediation required. Therefore, major cost savings can be made by optimising ground replacement/improvement strategies. This paper presents a numerical railway model, designed for the dynamic analysis of track-ground vibrations induced by high speed rail lines. The model simulates the ground using a thin-layer finite element formulation capable of calculating 3D stresses and strains within the soil during train vehicle passage. The railroad track is modelled using a multi-layered formulation which permits wave propagation in the longitudinal direction, and is coupled with the soil model in the frequency-wavenumber domain. The model is validated using a combination of experimental railway field data, published numerical data and a commercial finite element package. It is shown to predict track and ground behaviour accurately for a range of train speeds. The railway simulation model is computationally efficient and able to quickly assess dynamic, multi-layered soil response in the presence of ballast and slab track structures. Therefore it is well-suited to analysing the effect of different soil replacement strategies on dynamic track behaviour, which is particularly important when close to critical speed. To show this, three soil-embankment examples are used to compare the effect of different combinations of stiffness improvement (stiffness magnitude and remediation depths up to 5 m) on track behaviour. It is found that improvement strategies must be carefully chosen depending upon the track type and existing subgrade layering configuration. Under certain circumstances, soil improvement can have a negligible effect, or possibly even result in elevated track vibration, which may increase long-term settlement. However, large benefits are possible, and if detailed analysis is performed, it is possible to minimise soil improvement depth with respect to construction cost.

Fahrbahnunebenheiten und Gleislagestörungen können als Repräsentanten schwach stationärer Prozesse aufgefasst werden. Die Beschreibung der Qualitätsklassen von Fahrwegen erfolgt konventionell über die Spektraldichte (Leistungsdichte). Ausgehend von der Spektraldichte-Beschreibung wird die Generierung synthetischer Fahrwegstörungen für die numerische Simulation von Fahrzeugen als Mehrkörpersystem mit den Mitteln der Fourieranalyse und mit Hilfe von Wavelets untersucht<br>Road unevenness and track irregularities can be considered as realisations of weakly stationary stochastic processes. A description of track quality levels is given by the (power)spectral density of the related process. Here, the synthesis of track irregularities for a given spectral density using fourier series and wavelets is considered

Губар, О. В. Обґрунтування норм улаштування та утримання колії для кривих з радіусами менше 350 метрів : авт. дис. к. т. н.: 05.22.06 / О. В. Губар ; Дніпропетр. нац. ун-т залізн. трансп. ім. акад. В. Лазаряна. - Д., 2011.<br>UA: АНОТАЦІЯ. Дисертація присвячена обґрунтуванню норм улаштування та утримання колії для кривих з радіусами менше 350 м шляхом впровадження конструкції рейкових скріплень з можливістю складання та регулювання ширини колії у як в межах кругових, так і перехідних кривих для типових залізобетонних шпал. Розроблено математичну модель взаємодії рухомого складу і колії та програмне забезпечення, які дозволили в дисертації встановити раціональні обґрунтовані норми ширини колії та розробити технологію складання колії з залізобетонними шпалами. Надано методики суцільного і локального регулювання ширини колії зі скріпленням СКД65-Б. Отримані теоретичні й практичні результати використано в розробці конструкції колії на залізобетонних шпалах для кривих ділянок радіусом менше 350 м.<br>RU: АННОТАЦИЯ. Диссертация посвящена обоснованию норм устройства и содержания пути для кривых с радиусами менее 350 м путем внедрения конструкции рельсовых скреплений с возможностью устройства и регулирования ширины колеи как в пределах круговых, так и переходных кривых для типовых железобетонных шпал. Выполнен анализ материалов расследования сходов подвижного состава. Установлено, что основная часть сходов имеет место на станциях в кривых с радиусом менее 350 м при выполнении маневровых работ. В большинстве случаев сходили с рельсов локомотивы с трехосными тележками. Существующие на сегодня нормы ширины пути в кривых участках рассчитанны исходя из условий вписывания жесткой базы массового железнодорожного экипажа. Расчеты обоснования этих норм разрабатывались с учетом наличия, на то время, в вагонном парке длиннобазных двухосных вагонов и грузовых вагонов с трехосными тележками. При массовом внедрении железобетонных шпал норма ширины колеи на прямых и кривых при радиусе 300 м и больше на железобетонных шпалах установлена одинаковой, равной 1520 мм. Область применения железобетонных шпал ограничена величиной радиуса из-за необходимости обязательного расширения ширины колеи в кривых участках меньших радиусов. На сегодняшний день как на железных дорогах Украины, так и стран СНГ отсутствуют обоснованные нормы устройства пути на железобетонных шпалах в кривых участках пути с радиусами круговых кривых менее 350 м. Такие обоснования отсутствуют, в первую очередь, из-за того, что отсутствуют конструкции пути, которые отвечали бы требованиям для таких кривых, а именно возможностью устройства пути с заданной и обоснованной шириной колеи в пределах круговой кривой и обеспечения отвода расширения в пределах переходных кривых. Кроме того, такая конструкция должна предусматривать возможность регулирования ширины колеи, которая изменяется в процессе эксплуатации. Вопросом возможности внедрения железобетонных шпал в кривых участках с радиусами менее 350 м непрерывно занимались еще с 70-тых годов прошлого столетия. Как результат – в круговых кривых с радиусами от 200 м до 450 м было разрешено укладывать специальные железобетонные шпалы (типа Ш-6) с нормой ширины колеи 1535 мм, но опыт их эксплуатации оказался достаточно неудачным, из-за отсутствия как возможности регулирования ширины колеи, так и отсутствия возможности создания отвода ширины колеи в пределах переходных кривых. Автором разработана конструкция рельсовых скреплений для типовых железобетонных шпал (Ш-1, Ш-6), что дает возможность устройства и регулирования ширины колеи в кривых участках любого радиуса как в пределах круговых, так и переходных кривых. Эта конструкция прошла опытную эксплуатацию на сети железных дорог Украины и введена в постоянную эксплуатацию приказом Государственной администрации железных дорог Украины. В настоящее время при отсутствии длиннобазных двухосных вагонов и вагонов с трехосными тележками в вагонном парке и наличием разработанной автором конструкции, что позволяет собрать путь с шириной колеи до 1535 мм (1540 мм со шпалами типа Ш-6) появилась техническая возможность установления и регулирования ширины колеи в кривых, где необходимое ее расширение. Это вызывает необходимость обоснования норм устройства и содержания колеи для кривых с радиусами менее 350 м. О необходимости таких норм для железобетонных шпал в кривых участках пути с радиусами кривых менее 350 м свидетельствует количество деревянных шпал, уложенных в путь и которые могут быть заменены на железобетонные шпалы. Например, на Львовской железной дороге уложено 4 млн. 554 тыс. деревянных шпал что составляет 48 процентов от общего количества шпал, а на остальных железных дорогах доля деревянных шпал составляет от 22 до 30 % от их общего количества. Больше всего деревянных шпал имеют так называемые горные дистанции, где много кривых радиусом менее 350 м. Кроме того, фактический срок службы железобетонных шпал отвечает расчетному и складывает около 40 лет, а фактический срок службы деревянных шпал составляет около 7–7,5 лет, что в 2–2,5 раза меньше от расчетного. Основная причина сокращения срока службы связана с механическими повреждениями древесины в результате частых перешивок рельсовых нитей. По этой причине 33 процента деревянных шпал непригодны для дальнейшего использования. Кроме того, закупки деревянных шпал ограничены малым объемом предложений от поставщиков, из-за чего шпал катастрофически не хватает не только для проведения плановых, но и текущих ремонтов. Разработана математическая модель взаимодействия подвижного состава и пути и программное обеспечение, которые позволили в диссертации установить рациональные обоснованные нормы ширины пути и разработать технологию устройства и содержания пути с железобетонными шпалами. Полученные теоретические и практические результаты использованы в разработке конструкции пути на железобетонных шпалах для кривых участков радиусом менее 350 м и использованы в нормативно-техническом документе Укрзализныци «Инструкция по устройству и текущему содержанию пути со скреплениями типа СКД65» ЦП-0199.<br>EN: ANNOTATION. The present thesis grounds the standards of conformation and maintenance of track for curves with radiuses less than 350 m by introducing the rail clips device with the option of setting railway gauge within the ambit of both circular and transition curves for typical concrete ties. The mathematical model of interaction of rolling stock and track and the software that allowed setting properly grounded standards of railway gauge and developing the technology of conformation and maintenance of track with concrete ties are worked out in the thesis. Methods of general and local adjustment of railway gauge with the help of СКД65-Б rail clip are given. Theoretical and practical educts were used in the development of conformation of track with concrete ties for curves with radiuses less than 350 m.

The thesis deals with design of the tram power collecting route and the tram track of the route no. 3 in reconstruction area recently called “Zbrojovka Brno”. Connection to the present infrastructure is also considered. Housing, resting, administration sectors and tram stops are designed for easy availability in the new area. Because the railroad bounds the area on the East and will be extended in the future, joining the tram transport with integrated transport system in Židenice is possible. Design includes the new bridge across Svitava river and connection with surrounding areas. If we divide individual car transport (IAD) from the tram route, the trolley car transportation is designed in place IAD.

Набоченко, О. С. Підвищення ефективності роботи щебеневого баластного шару залізничної колії : авт. дис. к. т. н.: 05.22.06 / О. С. Набоченко ; Дніпропетр. нац. ун-т залізн. трансп. ім. акад. В. Лазаряна. - Д. : Вид-во Дніпропетр. нац. ун-ту залізн. трансп. ім. акад. В. Лазаряна, 2013. УДК 625.141.021(043.3) ГРНТИ 73.29.11 Захист - 25 квітня 2013 р.<br>UK: АНОТАЦІЯ Дисертація присвячена підвищенню ефективності експлуатації баластної залізничної колії з точки зору покращення роботи баластного шару шляхом встановлення раціональних параметрів конструкції колії та рухомого складу, експлуатаційних умов при оптимальних міжремонтних інтервалах. Виконано аналіз впливу та взаємозв'язків факторів впливу на розладнання баластного шару. Розроблено модель короткотривалих та довготривалих процесів взаємодії рухомого складу та залізничної колії, яка враховує розладнання баластного шару при багатократній дії рухомого складу та внутрішні динамічні процеси руху частинок щебеню та шпали у баластному шарі. Розроблено метод розрахунку розладнання геометрії колії, який враховує одночасний взаємний вплив основних груп факторів на роботу баластного шару. Запропоновано спосіб виміру ступеня ущільнення баласту, який ґрунтується на динамічній інтерпретації імпульсного відклику баластного шару. Виконано лабораторні та натурні вимірювання імпульсного відклику баластного шару з подальшим аналізом на реальних ділянках колії з різним ступенем ущільнення баласту при різних комбінаціях проходження важких колійних машин. Сформульовано практичні рекомендації щодо вибору епюри шпал в залежності від вантажонапруженості; ефективних параметрів роботи динамічних стабілізаторів колії та технології виконання робіт; раціонального співвідношення між швидкістю руху та осьовим навантаженням з точки зору роботи баластного шару та встановлено раціональні значення критерію призначення виконання підбивок баластного шару для пасажирського та вантажного руху<br>RU: АННОТАЦИЯ Диссертация посвящена повышению эффективности эксплуатации балластного железнодорожного пути с точки зрения улучшения работы балластного слоя путем установления рациональных параметров конструкции пути и подвижного состава, эксплуатационных условий при оптимальных межремонтных интервалах. Выполнен анализ влияния и взаимосвязей факторов влияния на расстройство балластного слоя и обобщены имеющиеся потенциалы улучшения работы балластного слоя с точки зрения уменьшения затрат жизненного цикла пути. Разработана модель кратковременных и длительных процессов взаимодействия подвижного состава и железнодорожного пути, которая учитывает расстройство балластного слоя при многократном воздействии подвижного состава, нелинейность работы подрельсовых опор и балластного слоя при взаимодействии пути и движущейся квазистатической силы, а также внутренние динамические процессы движения частиц щебня и шпалы в балластном слое. Моделирование динамических процессов, происходящих внутри балластного слоя под воздействием вибрационной нагрузки, выполняется с использованием метода молекулярной динамики. Согласно этому методу, каждая отдельная частица балластного слоя рассматривается как отдельное тело в контактном взаимодействии с соседними частицами, которое имеет вязко-упругие свойства и свойства трения. Разработан метод расчета расстройства геометрии пути, учитывающий одновременное взаимное влияние основных групп факторов на работу балластного слоя: факторов конструкции пути, подвижного состава, эксплуатационных условий и факторов содержания пути. В данном методе учтено влияние выполнения путевых работ на работу балластного слоя, а именно: после выполнения подбивки достигается определенная степень улучшения геометри пути, но одновременно происходит рост интенсивности деформаций при многократной подбивке из-за измельчения балластного материала. Степень улучшения зависит от геометрического состояния пути до подбивки. При этом учитывается, что с помощью побивки нельзя получить качество лучше, чем начальное качество пути, т.е. неровность из-за неравнопругости земляного полотна и неравномерной осадки при однослойной стабилизации пути. На основании знания механизмов расстройства балластного слоя и факторов, которые на него влияют, прогнозируется процесс расстройства геометрии пути и, соответственно этому, определяются рациональные строки текущего содержания и ремонтов пути. Предложен способ измерения степени уплотнения балласта, основанный на динамической интерпретации импульсного отклика балластного слоя, в основе которого лежит частотный анализ. Выполнено лабораторные и натурные измерения импульсного отклика балластного слоя с последующим анализом на реальных участках пути с разной степенью уплотнения балласта при различных комбинациях прохождения тяжелых путевых машин. Вследствие статистического анализа лабораторных и натурных измерений импульсного отклика балластного слоя выбрано параметры динамической интерпретации сигнала, которые позволяют надежно оценивать плотность балластного слоя, а именно: передний фронт волны, мгновенную частоту, начало спектра. На основании натурных измерений деформаций пути получены аналитические зависимости связи остаточных просадок пути в фазе стабилизации с параметрами импульсного отклика балластного слоя при различных степенях уплотнения. Сформулированы практические рекомендации по выбору эпюры шпал в зависимости от грузонапряженности; эффективным параметрам работы динамических стабилизаторов пути и технологии выполнения работ; рациональному соотношению между скоростью движения и осевой нагрузкой с точки зрения работы балластного слоя и установлены оптимальные значения критерия назначения выполнения подбивок балластного слоя для пассажирского и грузового движения; дана рекомендация рациональных величин вертикальных неровностей с точки зрения содержания балластного слоя, при которых назначаются работы по подбивке пути.<br>EN: ABSTRACT The thesis is dedicated to increasing the efficiency of operation of the railway ballast in the point of view of ballast improvement by means of establishment of rational track design parameters and operating conditions. The analysis of effects and interactions of factors on the ballast work is done. A model of short-term and long-term processes of interaction between the rolling stock and railway track is developed. The model takes into account the ballast deterioration under the rolling stock loading and the internal dynamic processes of particles of ballast and sleepers in the ballast layer. A method of calculation of railway track geometry deterioration is completed. The method takes into account the simultaneous mutual influence of the main groups of factors. A method for measuring the degree of compaction of ballast is proposed. The method is based on a dynamic interpretation of the ballast impulse response, which is grounded on frequency analysis. Laboratory and field measurements of the ballast impulse response with the following analysis on real track sections with a different degree of ballast compaction are fulfilled. Practical recommendations are proposed: the sleeper layout depending on the traffic density; the effective parameters of the dynamic stabilizers; the optimal ratio between the train velocity and axial load depending on the ballast maintenance intervals.

Jusqu'à présent les modèles multi-corps d'interaction véhicule-voie ferroviaire utilisent principalement des composants rigides. De tels modèles présentent l’avantage d’un nombre de degrés de liberté limité permettant de réaliser des calculs en temps réel à basses fréquences. En revanche, ils ne permettent pas de prédire avec suffisamment de précision les spectres des efforts de contact roue-rail en raison de l’hypothèse d’éléments rigides qui est assez forte. Aussi ces modèles gagneraient à être améliorés en prenant en considération la flexibilité des éléments. Ceci est possible grâce au couplage éléments finis – dynamique multi-corps. Les travaux réalisés dans le cadre de cette thèse ont pour objectif, l’amélioration des prédictions des efforts d’interaction véhicule-voie par intégration d’essieux et de rails flexibles dans les modèles multi-corps du véhicule et de la voie. Des modèles éléments finis des essieux et de la voie ont été développés et couplés au modèle global de la dynamique multi-corps via des méthodes de réduction de modèles afin de gagner en précisions tout en limitant le nombre de degrés de libertés. Différentes configurations des modèles multi-corps du véhicule et de la voie avec des essieux et des rails flexibles ont été explorées afin d’évaluer les effets de la flexibilité des éléments sur les prédictions des efforts de contact. Les premiers modèles sont réalisés avec des essieux flexibles roulant sur une voie théorique parfaite sans défauts avec des rails rigides en alignement puis en courbe. Ces modèles ont été ensuite modifiés afin d’intégrer la flexibilité des rails ainsi que des excitations générées par les défauts des roues et des rails (usure ondulatoire, méplat de roue et joint de rail)<br>Multibody models for the study of the vehicle-track interaction used by railway companies consider mainly rigid components. These models are characterized by small number of degrees of freedom allowing real time calculations in low frequency ranges, but these models do not properly estimate real interaction forces because of the strong hypothesis of the components rigidity. These models need to be improved by taking into account the components flexibilities by coupling finite elements analysis with multibody dynamics simulations. The main objective of this study is to develop the multibody models of a railway vehicle and track with flexible wheelsets and flexible rails in order to improve the prediction of vehicle-track interaction forces. Finite element models of wheelset and track are developed and reduced using model reduction methods to reduce their number of degrees of freedom before their integration in the multibody models. Different configurations of vehicle and track models with flexible wheelsets and flexible rails are considered to evaluate the effect of components flexibilities on the contact forces. The first models are made of flexible wheelsets rolling on a perfect track with rigid rails in alignment and curve without irregularities. Then, these models are improved by integration of flexible rails and excitations involved by the rail and the wheel irregularities (rail corrugation, wheel flat and rail joint)

碩士<br>國立高雄應用科技大學<br>土木工程與防災科技研究所<br>105<br>The information of track alignment irregularity is obtained by many random operation situations. After railway construction has completed, track geometric alignment will be continue deformation due to wheel/rail interaction. Then, there are many effects such as train operation safety, stability, riding comfort, wheel/rail life and circumstance noisy to occur. For ensuring safety operation and providing stable and comfortable service, track alignment regularity is very important work for rail maintain management. The lasting external load added on the rail to lead to deformation or deflection, which is called "track alignment irregularity". There are five major track irregularities to bring the train operation with wagging, yawing, twisting and nodding. The rail structure will be damaged by the excess lateral and longitudinal forces. This study is focused on the occurrence probability of track alignment irregularity. The result showed that track interval and elevation for irregularity are more appeared on occurrence probability. Although the train is no driving safety, but there are riding comfortable problems.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008.<br>Title from title screen (site viewed Mar. 5, 2009). PDF text: viii, 143 p. : col. ill. ; 13 Mb. UMI publication number: AAT 3331436. Includes bibliographical references. Also available in microfilm and microfiche formats.

碩士<br>臺灣大學<br>土木工程學研究所<br>98<br>The track class and speed for North American railroads are governed by regulations from the Federal Railroad Administration. Better quality of track permits greater operational speeds and lower transportation cost but also requiring greater maintenance expenditure. In this study, we considered this trade-off between maintenance and transportation costs, and developed an optimization framework determining the optimal assignment for track class based upon the characteristics of the track, traffic demand, and maintenance budget. This tool can help railroads maintain tracks at their most appropriate level so as to provide reliable and cost-effective services.

碩士<br>國立成功大學<br>土木工程學系碩博士班<br>97<br>This article studies two major topics. One investigates the behavior of ground vibrations induced by the train moving on the embankments using field experiments, theoretical formulations, and finite element analyses. The other investigates the vibrations on the trains passing the structures of bridges and embankments. Experiments measured on the vehicle are used to realize the characteristics of vibrations on the trains of THSR (Taiwan High Speed Rail), Taipei MRT, and Taiwan Railway. In the first topic, the train-induced vibrations are large at the dominant frequencies of nV/Lc, even though the track is very rough. For subsonic train speeds, the train-induced ground vibration is extremely small when the track is perfectly smooth, but with a minor track irregularity, the train-induced ground vibration can be significantly increased. However, for supersonic train speeds, the ground vibrations with or without track irregularities are not very different, and the vibration of the first dominant frequency having the longest wavelength is the most obvious wave. In the second topic, the vibrations on the train in the track direction are smaller than those in other two directions. The major vibration frequencies on the train are come from the natural frequencies of trains and bridges. Furthermore, the vibrations on the train from Tainan to Taichung are similar, even through the soil properties between the two locations are very different.

碩士<br>國立中央大學<br>土木工程研究所<br>100<br>In this thesis, the vehicle-bridge interaction problem with small and smooth track irregularity in vertical direction is studied by experimental and numerical analyses. The experimental structure is set up in the laboratory, including a bridge model with tracks and a car model with suspension system. The velocity and deformation of the bridge model and velocity and acceleration of the car model are measured when the car model passes in different velocities through the bridge structure. The dynamic responses in the all models were also measured when the car model in several different weights passed though the bridge model with a vertical irregularity; and the numerical model included wheel/track contact was established by LS-DYNA code. The results from experiments are compared with the results of numerical analyses. Numerical results reveal that the LS-DYNA can simulate well the dynamic performance measured from the experiment. The dynamic performance of the car passing a lateral irregularity should be carried on in the future study.

碩士<br>淡江大學<br>土木工程學系<br>91<br>The demands for railroad track maintenance and rehabilitation (M & R) activities are gradually increasing due to the continuing deterioration of our old rail track systems as well as the call for expansion of domestic railroad systems. Proper selections of M & R activities can reduce their frequency and extend track service life to assure the best use of our limited resources. The major objective of this study is to conduct an in-depth investigation on the application of composite index in railroad track maintenance management system. The current practices of domestic track M & R activities were first reviewed. The fundamental concepts and evolutions of different composite indices including Track Quality Index (TQI) and Track Structural Condition Index (TSCI) were investigated for high and low volume track systems, respectively. Track geometry signatures are usually measured through the use of an automated inspection car. A TQI derived from the number of exceptions to a performance based threshold is appropriate for allocating M & R resources. An overall TSCI is determined based on the detailed track inspections of different rail, joints, crossties, ballast, and subgrade components through visual means. Furthermore, the major concerns of the global application of composite indices are toward standardization, simplification, and automation. A preferred composite index should be determined based on its measuring ability, replicability, objectivity, consistency, and efficiency. A total track management system consists of safety, network level, and project level management activities. Together with the utilization of “sampling”, “dynamic segmentation”, and “uniform section” concepts, an automated Track Maintenance Management System (TMMS) prototype program with well-organized Windows-based graphical user interfaces was developed using Microsoft Visual Basic 6.0 program. Given the original survey data, this prototype program can automatically calculate TQI and TSCI, which are applicable to future project-level and network-level track M&R management activities. Case studies were conducted to validate the correctness of this prototype program through comparisons of manual calculations and the results of the RAILER program. Ultimately, the inspection results may also be used to predict track deterioration rate and future conditions, determine required budget levels, as well as inspect the effectiveness of M & R strategies in the future.

碩士<br>國立成功大學<br>土木工程學系碩博士班<br>91<br>This research project was an effort to improve our understanding of the design and performance analysis of geosynthetics application in railroad track mitigation. Insert of geosynthetic layer at the subgrade and subbase interface, increase the bearing capacity of the track, separate the aggregate base course and the subgrade to prevent two dissimilar material from intermixing, and acts as a filter to prevent stone aggregate intrude into the fine soil or fine soils migrating up into voids of stone aggregate due to high pore water pressure induced by cyclic loading. This research project was collaboration with China Steel Company , in order to mitigation railway ballast and aggregate degrade and deterioate progressively under cyclic loading by using geosynthetics reinforcement. The railroad track deformation and economic benefit were analyzed using numerical technique, FLAC program and Tensar-Pave software. FLAC (Fast Lagrangian Analysis of Continua) was selected for this research because of its excellent capability of modeling geotechnical engineering related stability problems and its extended programming ability. First, FLAC model and Tensar-Pave software were used to simulate the field instrumentation measurments in real railroad track situation and then comparing with field measuring data (from settlement plates), in purpose to provide the mitigation of geosynthetic railroad track. Results shown that the geosynthetics reinforced test section of the railroad track produced lower settlement about 30 % off compare to the unreinforcd test section and because of geosynthetics reinforcement function saving the amount of aggregate/ballast thickness about 20-40 %. Thereby, design cooperated with numerical techniques (FLAC) and Tensar-Pave software, would improved techniques for analyzing the track deformation, economic benefits (aggregate saving) and reduce the railraod track maintenance cost.

碩士<br>國立臺灣大學<br>工程科學及海洋工程學研究所<br>100<br>This paper studied the effect of long term concrete creeping behavior of pre-stressed concrete bridge on the vibration of track structure and ridding comfort of high speed rail. Track irregularity can be induced by creeping of pre-stressed concrete bridges. The finite element analysis software ANSYS was used in this paper to calculate the deflection of viaduct by concrete creeping. To consider the pre-stressed effect, we build a five-span concrete bridge model with pre-stressed tendons and calculate the creep coefficient according to the code of CEB-FIP 1995. Vertical deflections by concrete creeping in 20 years were presented in several period. A 4-carbody train passing through deflected bridge in different creeping time was taken into consideration. We use the finite element analysis software, LS-dyna, to perform dynamic analysis. The total accelerations on the car were calculated and the riding comfort was evaluated by ISO 2631-4(2005).

The South African railway company makes use of a train wheel detection system to monitor the trains present on a particular track, noting their lengths, positions and speeds. Interference due to distorted traction currents cause havoc with this system rendering the information gathered unreliable. To combat this interference two paths are available to reduce the detection systems susceptibility. These paths include the addition of shielding between the railway track and the wheel detectors, which form the functional entities of the train wheel detection system, and the installation of a cable running parallel to the railway track with connections to it some distance before and after the position of the wheel detector. To verify these paths, high frequency experiments were performed in the lab as well as FEM simulations. To perform the high frequency experiments a source capable of producing the high frequency current needed was designed and constructed, along with a well shielded measurement system to enable the mapping of the flux density within the region occupied by and surrounding the wheel detector. The results of both the experimental measurements and simulations yielded that the interfering magnetic field could indeed be reduced through the use of the two available paths, when they are both applied separately and in combination. To obtain the greater reduction in the interfering field within the area occupied by and surrounding the wheel detector the paths should be used in combination. Therefore through the use of a shield that is constructed from a magnetic material and the installation of a parallel cable the train wheel detection system can be made more robust.<br>Prof. W.A Cronjé Prof. I.W. Hofsajer