Center for Railway Engineering

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Browsing Center for Railway Engineering by Author "Abdulsetar, Siraj (Mr.)"

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    Analytical and Finite Element Analysis of Rail Deflection and Bending Stress Under Different Sleeper Spacing
    (Addis Ababa University, 2017-04-25) Lemmi, Gurmessa; Abdulsetar, Siraj (Mr.)
    The amount of wheel load that distributed through each sleeper depends on the track bed quality, sleeper type and sleeper space. The relationship between applied loads, track stresses, and track deformations are factors to be considered in proper track design and maintenance. Any defects and changes in track components will produce defects in rails in turn. Among these results rails bending stress, rails deflection and rails support loads are from the most parameters to be considered during the design of rail track. This research has investigated the effects of sleeper spacing, particularly the rails deflection, the induced rail bending stresses and the rail supporting force under several concentrated (Wheel) moving loads and single wheel load. Finite element method model and beam on elastic foundation (BOEF) track model have been used to get numerical and analytical solutions respectively. The Finite element method analysis was carried out in ANSYS work bench. Results from both analyses were analyzed by quantitative approach and compared together. Train axle arrangements and wheel static load have been taken from rolling stock proposed for Sabata- Mieso-Djibute Line which is identified as “HXD1C high power AC drive six-axle (7200kw) freight electric locomotive”. The Analysis shows numerical analysis gives higher values of rail deflection; lower values of rail supporting force and rail bending stress than analytical analysis. On the other hand the analytical analysis shows that multiple wheel loads gives higher values of rail deflection and rail supporting force but lower values of rail bending stress than single wheel load while numerical analysis shows single wheel load gives higher values (rail deflection, rail supporting force and rail bending stress) than multiple wheel loads. This one occurred due to the fact that the effect of one axle load gives positive value while the other gives negative values. The summation of the positive and negative values will be lower than the single positive value obtained from single wheel load. The differences of these values depend on the sleeper space and rail track bed quality.
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    Development of Maintenance Model and Strategy For Addis Ababa Light Railway Transport (AALRT) Railway Track Line
    (Addis Ababa University, 2016-12) Melese, Teshome; Abdulsetar, Siraj (Mr.)
    There is a need among transportation maintenance decision makers for a better understanding of the long-term behavior of railroad tracks. The use of accurate techniques (maintenance model and strategy) to predict track conditions increases track safety and maintenance effectiveness as well as reduce maintenance costs through improve planning. This paper describes the track maintenance model and strategyrelevant for Addis Ababa Light Rail Transit.By using reliability model with weibull distribution, the expected number of critical and degraded failures are determined. Then three failure mechanisms are determined and the rate of critical and degraded failures is determined for each failure mechanism. Finally the governing value of critical and degraded failure are chosen to determine reliability parameters such as mean time to failure(MTTF),mean time to detect(MTTD),mean time before failure(MTBF),mean time to repair(MTTR) and preventive maintenance index(Ipm). The analysis result shows that, the Frequency of critical failure is reduced by 56%by conducting three inspection per year. And also the Mean time until any failure is detected by conducting inspection at every four months of interval for AALRT Railway track line (MTBF) is obtained as 2.55 years. Then after, four maintenance strategies are developed for AALRT. These are: Repair as soon as the component is identified to be in a state where repair is necessary, repair when the component is identified in the state where a major repair is required, repair when the component is identified as being in the state where renewal is needed and no repair, component is allowed to deteriorate without any intervention.
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    Effects of Design Parameters on Curved Ballasted Track
    (Addis Ababa University, 2016-12) Yonatan, Abebe; Abdulsetar, Siraj (Mr.)
    Train and track interactions during services normally generate substantial forces on railway tracks. Such forces are transient by nature and of relatively large magnitude. There has been small literature showing of the typical responses for the loading conditions on the curved section of railway track structures, in particular, lateral and vertical loads. This paper presents a response of the curved section of a ballasted railway track structure for different parameters of track and train. In this research, the response of curved ballasted track components as a function of speed, cant and curvature is investigated using numerical modeling. Curved and straight section of ballasted railway track is modeled using the finite element approach. The paper mainly focuses on studying the effect of speed, cant as well as curvature on the values of deformation/displacement of the components of the track . Taking into account a model representing the train load, the model forms a dynamic analysis and a non-linear quasi-static analysis of track structures using Finite Element Modeling method with the use of commercially available software ABAQUS. The main results that are used to investigate the effect of speed, cant and curvature are vertical and lateral rail deflection, vertical and lateral sleeper displacement and vertical and lateral subgrade displacement Hertz analytical method was used to assess the axle load and train speed effect based on the results of calculated contact pressure and penetration depths for a selected straight section where the half-space assumption is valid. Results show that with increasing train speed track deflection grow higher. It is observed that, for example, in a long-term the outer rail response for a 350 meter radius ballasted track there is 0.3536 mm lateral deflection increase for every Km/hr increase of train speed. It is recommended to do a feed-back loop for the long-term behavior of the track.
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    Modeling and Analyzing the Deformation of Ballast Structure Due to Repetition of Loads
    (Addis Ababa University, 2015-12) Shimelis, Assefa; Abdulsetar, Siraj (Mr.)
    The issue of permanent deformation of ballast structure due to repetition of loads is the most important element in railway maintenance planning and policy making. It affects the general operation and management of railway transportation plus the overall costs of track structure and its life spans. To allow a safe, reliable and efficient rail network and to provide a good ride quality, the vertical profile of a railway track has to be maintained at a satisfactory level. And timely maintenance of ballast structure is essential to provide continuous service at reasonable costs since the track permanent deformation is a function of traffic load, environmental condition and track structure response behavior to the applied loads at different times of service life. Although most of the time deterioration process is very slow, but it might lead to massive failures with an enormous financial lose. This research determines the permanent deformation of railway ballast, particularly the vertical settlement under repeated traffic loading. Experimental data reviewed in the literature were assumed to represent the ballast materials used in LRT projects. After initial elastic modeling, the extended Drucker-Prager model with hardening, which simulates the initial plastic deformation of granular materials under cyclic loads, were used in the FEM analysis in order to account for the inelastic behavior of railway ballast. Besides, FEM analysis provides the information to predict railway ballast deformation in terms of number of loading under wheel loading. And it can be observed that the vertical stresses were concentrated underneath the sleeper and ballast permanent deformation is increasing exponentially with increasing number of loading cycles and deform non- linearly with increasing depths of ballast.