Railway Engineering

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Simulation and Control of Wheel Flange Climbing Derailment Using Actuators
(Addis Ababa University, 2016-11) Mensur Birhan; Zewudu Abadi (PhD); Tolosa Deberie (Mr.) Co-Advisor
This research explores how active actuation systems can affect rail vehicle dynamics, using a combined multibody simulation and experimental verification strategy. The research addresses an important issue concerning vehicle-track interaction, particularly large vibrations, instabilities in wheel-rail contact forces, and potential derailment, as each of these factors critically impact ride quality, safety operations, and maintenance costs. The methodology contrasts multibody dynamics modeling with experimental validation of key metrics, such as accelerations of the car body and bogie, wheel-rail contact forces, derailment coefficients, wheel lift, attack angles, and spectral vibration characteristics. The simulation-based evaluation compares system performance with and without active control under various operational conditions. The paper will demonstrate the capability of active control to mitigate harmful rail vehicle dynamics. The findings indicate significant improvements across all assessed measures. Active control leads to a 52% improvement in vertical car body acceleration (from 0.076 m/s² to 0.0375 m/s²) and a 35.7% improvement in lateral acceleration (0.28 m/s² to 0.18 m/s²), markedly improving ride comfort and stability. The wheel-rail contact forces are reduced by 1.3% vertically (73.75 kN to 72.8 kN) and laterally 3.6% (8.9 kN to 8.3 kN), which improves wear characteristics and longevity of components. The derailment coefficient is lower by 4.3% (0.115 to 0.11), improving the safety margin, and wheel lift is lower by 2.1% (375×10⁻⁶ m to 367×10⁻⁶ m), facilitating better contact stability. Spectral analysis reveals that active control shifts resonant frequencies down (e.g. from 9.67 Hz to 8.75 Hz) for car body vibrations and simultaneously reduces amplitudes, which signifies that well-targeted vibration suppression is achievable within critical frequency bands. These results give strong support to advance the implementation of active actuation in rail systems, especially in high-speed applications where dynamic performance is important. We showed that active control improves safety, comfort, and maintenance efficiency; furthermore, it also validated both theoretical and experimental models in our study. These results provide a practical basis to use active suspension in future rail vehicles.
Modeling Passengers’ Attitude and Analysis of Travel Experience Attributes: A case of Addis Ababa Light Rail Transit
(Addis Ababa University, 2015-04) Gizachew Kefelew; Fitsum Teklu (PhD)
The importance of public transportation in developing countries lies in its ability to promote sustainable urban development, support economic growth, and enhance the overall well-being of communities. Light rail transit systems are particularly essential for alleviating traffic congestion issues on roads by offering an alternative mode of transportation. Therefore, it is essential to assess the performance of light rail transit services from passengers’ perspective to pinpoint both strengths and areas needing improvement within the transit network. Accordingly, the primary goal of this thesis research is to evaluate the light rail transit service performance from the perspective of AA-LRT’s passengers and recommend optimal improvement strategies that enhance travel experience of passengers. Through a satisfaction survey conducted via paper-based questionnaire, the authors determined the passengers' satisfaction index on AA-LRT’s service through HPSI. The calculated overall passenger satisfaction index of 2.66 indicates that passengers remain below the “fairly satisfied” threshold (score=3). The authors also proposed an NDS compartmental model to explore trends of passenger satisfaction levels. The model categorizes passengers into "N" for less or quite satisfied, "D" for dissatisfied, and "S" for satisfied. The model was evaluated for existence and uniqueness of solutions, as well as the positivity and boundedness of solutions. Local stability was analyzed for both dissatisfaction-free and dissatisfaction-persistent steady states. An optimal control problem was formulated and analyzed to investigate strategies for minimizing passenger dissatisfaction. Numerical findings indicate that the efforts related to providing train services that adhere to high levels of reliability and punctuality for arrivals, and related to trains operate with excellent safety and security standards effectively reduces dissatisfaction levels. The graphical representation of numerical results also indicates the importance of the order of the fractional derivative in representing the evolution of passengers’ satisfaction over time with consideration of memory effects.
Modelling of Balfour Beatty Embedded Rail System (BBES) for Dynamic Analysis
(Addis Ababa University, 2015-01) Mesfin Hailu; Mequanent Mulugeta (PhD)
The main purpose of design of track structure is to have cost effective good riding quality with optimum speed. Recently, several findings are giving attention for a track of high speed with maximum comfort to have ideal track. However, most tracks of these types are prone to huge initial investment, so that still on the ground, the old traditional ballasted track system is dominantly under construction with its several problems. The Balfour Beatty Embedded Rail Track System (BBES) is invented to offer economical as well as safety and comfort advantages. In this thesis, dynamic response of BBES studied. Track dynamic analysis has been done by modeling the prototype track using finite elements and analyzing the spatial responses of the track. The first step was developing a finite element model of the track using known modeling software- ABAQUS. The modelling algorithm was made in 3D to analyze the system responses. The dynamic responses of the track evaluated and some responses are compared to that of traditional ballasted track from literatures of previous studies. The natural frequency, modal dynamics and response spectra of the track analyzed using ABAQUS steady state dynamic solver. Effect of rail pad stiffness on the on the rail has been investigated under single harmonic load. The finite element solutions obtained from the solver software are based on frequency domain. The results of the track dynamic responses are encouraging that it could be the best fit of requirements of track structures of the era. The vertical displacement of the BBES rail is lower than that of the conventional ballasted track system. Dynamic spectrum shows that most BBES dynamic responses are maximum at lower frequencies so that the period of vibrations are longer at these maxima. Higher displacement is shown in lower stiffness rail pad so that dynamic aggressiveness decreases in decreasing the pad stiffness. The thesis discussion also includes the potential of manufacturing the components of BBES in Ethiopia. The presence of companies in Ethiopia potentially capable to manufacture different components of the track and the small number of components needed for the track make it’s life cycle cost less than that of conventional ballasted track.
Ballast Degradation Modelling: Case study of Addis Ababa Light Rail Transit
(Addis Ababa University, 2025-08) Alemwork Eshetie; Tezera Firew (PhD); Anteneh Zewdu (Mr.) Co-Advisor
Railway infrastructure should be maintained regularly to improve its performance. This operation requires a large investment and shall be planned well to avoid human and financial resource waste. Various studies found that most of the track geometrical irregularities that seek maintenance are related to the degradation of the underlying ballast. This implies that for planning track geometry maintenance the understanding of ballast degradation mechanism is crucial. In this research, a ballast degradation model that characterizes ballast quality degradation and predicts ballast degradation from different parameters is developed for Addis Ababa Light Rail Transit (AALRT). This paper uses a statistical approach for ballast degradation modeling. Fractal dimensioning of track longitudinal level was applied to determine ballast quality index and to characterize ballast quality degradation. Previously recorded inspection data of track longitudinal profile were collected from Ethiopian Railway Corporation (ERC) and used to develop the model. The irregularities of the vertical track profile are quantified as a ballast quality index. This ballast quality index is used as a basis for developing ballast degradation model. Two ballast regression models were developed for straight and curved sections of AALRT. This degradation model is useful for AALRT infrastructure managers for understanding and predicting ballast quality and it will upgrade the performance of the railway maintenance operation.
Analysis of Crack Initiation and Fatigue Life on Light Rail Transit (LRT) Wheel Tread Profile: A Finite Element Approach.
(Addis Ababa University, 2025-05) Kaggwa William; Araya Abera (PhD)
The conditions within which railroad wheels operate, damage to their treads is inevitable. The damage ranges between minor (scratches) to major (fatigue cracks). This has advocated for studies and investigations into the various parameters that lead to their damage; included among the parameters is crack initiation (formation), propagation, and fatigue. This study, aimed at not only looking into the parameters that influence crack initiation but also dwell into investigations into the effects of varying the loading conditions and crack orientation on the stress distributions at the wheel tread surface and thereafter the effects of varying the crack lengths in the region of maximum stress concentration to the fatigue life cycles (cycles per mm growth). The research employs a model developed in SOLIDWORKS modelling software, and analyzed using both ANSYS and FRANC3D tools. Results showed that maximum stress occurs when cracks are aligned in the direction of motion, exceeding the material's ultimate tensile strength at overload capacity. Fatigue life analysis further revealed a strong dependency of the cycles on crack length. The study underscores the role of stress intensity factors and crack length in predicting fatigue life cycles.
Optimizing Railway Energy Reliability from Wind Energy Harvesting: A case study of Addis Ababa Light Rail Transit
(Addis Ababa University, 2025-06) Nakaibaale Tracy; Mesfin Belayneh (PhD)
Within the City of Addis Ababa, Ethiopia, the Addis Ababa Light Rail Transit (AALRT) contributes to crucial transportation benefits, which is a strategic connectivity of areas in Addis Ababa, however, the railway line faces a problem of frequent power outages, which undermines its energy reliability and sustainability. To address this challenge, this thesis investigates the feasibility of harnessing wind energy from moving trains along the AALRT corridor, taking into consideration the natural wind resources. Unlike large-scale grid-connected wind farms, this research explores the integration of small-scale wind turbines to supply power to railway auxiliary subsystems and employs advanced control strategies, this research aims to improve the reliability and sustainability of the railway’s energy supply. The research focuses on designing and implementing Fuzzy Logic Control (FLC) based Maximum Power Point Tracking (MPPT) to extract maximum energy from the Wind Energy Harvesting Systems(WEHS). Considering that the AALRT’s average speed is 30 km/h, the opportunity lies in capturing the wind produced by the moving train, as well as natural wind in the area, for power production particularly with an emphasis on optimized energy conversion using FLC-MPPT to maximize power capture from the Wind Energy Conversion Systems(WECS) through optimizing the MPPT process i.e., the control of the Tip Speed ratio and the Pitch angle to achieve higher power output in comparison to the traditional methods. The research concludes with practical recommendations for the deployment of integrated small-scale WECS, focusing on optimization by FLC-MPPT, along railway corridors, and power conversion to manage wind power. It also outlines future research directions to further advance wind energy harvesting technologies. The results of this thesis offer valuable insights for engineers, researchers, and industry stakeholders seeking to enhance railway energy resilience and promote sustainable transportation infrastructure, with a particular emphasis on distributed power generation through small-scale WEHS and advanced MPPT control."
Enhancing Railway Track Structural Condition Assessment Using Multi-Criteria Decision-Making Method
(Addis Ababa University, 2024-10) Kirubel Firew; Fiseha Nega (PhD)
The safety and reliability of railway infrastructure are dependent on diligent maintenance and inspection practices. A well-organized maintenance approach is imperative in ensuring the safety and reliability of a railway system. One of the most important aspects of railway maintenance is the detection and monitoring of track defects, which can lead to catastrophic failures if left unaddressed. While existing techniques can be beneficial in certain respects, they are incapable to provide a comprehensive view of the structural conditions of railway tracks, compromising ride safety and quality. This research addresses this gap by developing a model for railway track structural condition assessment using Multi-Criteria Decision Making (MCDM). Leveraging an extensive literature review the model assigns weights to key track components and defect categories through the Best-Worst method. Mamdani Fuzzy logic integrates diverse defect criteria and translates qualitative severity evaluations into numerical scores. The analysis reveals rails (48.16%) as the most critical component, followed by sleepers (21.05%). Within rail defects, transverse fissures hold the highest weight (43.75%). Validated through a case study, the model demonstrates strong agreement with actual results. A user-friendly application built on FlutterFlow facilitates detailed track condition assessments, encompassing individual defect categories, component health, and overall track structure status. This model empowers data-driven decision-making for railway authorities, enabling them to prioritize and address track issues effectively. The MCDM approach provides a structured framework for maintenance planning. Ultimately, this research aims to refine railway track infrastructure management through a structured and data-driven decision-making process.
Ground Penetrating Radar Simulation for Estimating Track Bed Thickness and Material Characterization.
(Addis Ababa University, 2024-06) Samuel Hailemariam; Fiseha Nega (PhD)
One of the most important substructures is the railway, which is a vital component of a country and demands significant investment. A railway track bed's surface layer is a multilayered structure. Three sublayers are often present: the top surface layer, known as ballast, the intermediate surface layer, sometimes known as sub-ballast, and the subsequent surface layer (Subgrade). An essential instrument for evaluating the status of railroad track beds is ground penetrating radar (GPR), which makes it possible to estimate the thickness of the track bed and classify the materials. . However, accurate interpretation of GPR data is challenged by the resolution limitations of GPR and the similar permittivity of track material sublayers. This study aims to verify and optimize GPR simulations using GprMax to improve the accuracy of determining track bed thickness and characterizing materials within railway infrastructure. The research methodology involves simulating various parametric conditions such as ballast fouling, variable track bed layer thicknesses, and different moisture content scenarios (wet and dry conditions). A structured approach is employed, starting with the establishment of study area characteristics, followed by configuring the geometry and materials in GprMax. The appropriate GPR antenna and frequency settings are then defined, and simulation settings and boundary conditions are established to ensure numerical stability and accuracy. Simulations are conducted, and the results are analyzed through post-processing techniques to examine the impact of parameter changes on GPR responses. Visualization capabilities of GprMax are utilized to compare simulated GPR scans under different conditions. The simulated results are validated against known field data or theoretical expectations to verify the simulation setup and parameters. The study concludes that GPR simulations in GprMax can effectively model the impact of ballast fouling, layer thickness variations, and moisture content on GPR signals. These simulations provide valuable insights into improving GPR data interpretation, promoting cost-effective maintenance strategies by reducing the need for extensive physical testing. This research contributes to enhancing the reliability and efficiency of GPR in railway infrastructure maintenance.
Failure Analysis of Switch Rails and Crossings Towards Maintenance Improvement: A Case Study of Addis Ababa Light Rail Transit
(2024) Ruhama Minwuyelet; Daniel Tilahun (Assoc. Prof.)
Railway systems are such a complex transportation systems that consists several components like rails, switches, crossings, check rails, turnout carriers, and some other components. Maintenance of railway “switch and crossing” (S&C) systems is critical for effective and safe train operations. The material degradation and geometry optimization of switches and crossings should be considered for an efficient operation of railway system. The failures of railway tracks are an unavoidable phenomenon that affects the operation intensively. AALRTS rail material is 50 Kg/m U71Mn and the frog is Hadfield steel. Previously different failure assessment and investigation researches have been carried out, however, failure investigation techniques need to be updated frequently and assessed because the problem still exists. Markov chain model was implemented for statistical analysis of critical failures and the output results are “Mean Time To Failure” for both critical and disastrous failures. Based on the results it is possible to recommend that increasing the number o f “Ultrasonic Inspection Cars” test from 3 to 5 or increasing the test interval from 122 days to 73 days per year will minimize “Mean Time To Failure” from 3.1 years to 1.6 years. The mean time to failure results can be an input for a strategic track maintenance planning. “Failure mode, effects, and criticality analysis” (FMECA) were implemented to identify the most critical failure mode with higher risk. The welded rail specimen`s quality, hardness, and microstructural features were evaluated at different cooling rates experimentally. To identify and assess the microstructure feature and hardness of rail welding through different cooling rates three major NDT tests have been employed. Increasing the number of tests of inspection or the inspection interval will minimize the mean time to failure. Generally, all the non-destructive test results demonstrate that there is a noticeable defect on the welded rail cooled at 6°C/s. Comparatively fewer defects were observed on the welded rail cooled at 3°C/s; while acceptable defects were manifested on the one cooled at 2°C/s. The minimum cooling rate can be achieved through both preheating and post-heating process. From the switch panel, “Failure mode, effects, and criticality analysis” (FMECA) results “gauge corner spalling” failure mode was with the highest risk priority number so that its improvement has a great influence on the maintenance efficiency.Additionally, from the detail results of failure mode, effects, and criticality analysis (FMECA) of turnouts; failure modes under high risk category need special attention during maintenance planning and need improvement of rectification techniques. From the results of the analysis six failure modes have been laid under high risk categories whereas two failure modes have been laid under moderate risk categories and four failure modes have been laid under low risk categories. As a conclusion cooling of rail welding`s at 2°C/s cooling rate will give the material good micro-structural feature and better weld quality relatively. This minimum cooling rate 2°C/s achieved by uniform and optimum preheating and post-heating temperatures. Finally, the researcher recommend a controlled cooling rate for welding quality improvement and maintenance efficiency increment.
Techno-Economic Analysis of Deploying Communication Based Train Control System (Cbtc): In Case of Ethio- Djibouti Railway Line
(Addis Ababa University, 2024-01) Abdurahman Endris; Yalemzewd Negash (PhD); Birhanu Reesom (Mr.) Co-Advisor
The techno-economic analysis is a technique to evaluate a technology's economic performance. It measures a technology's entire significance, enabling analysts to objectively assess benefits and expenses. It is crucial to conduct a techno-economic study of any new technology or product at the research and development stage before commercializing it for use in a significant industrial process. Due to the train control system's rapid growth, studies recommended a new communication control system called communication-based train control system. It improves line capacity and minimizes trackside equipment by safely reducing the separation (headway) between trains operating on the same line. The acceptability and economic viability of a new technology can‟t be demonstrated via implementation or adoption without a comprehensive technical and economic feasibility assessment. Therefore, we were motivated to investigate the techno-economic analysis of adopting CBTC for the Ethio- Djibouti railway line. For this study's techno-economic analysis, we utilized capital expenditure, operating expenditure, and total costs of ownership. We have analyzed the coming five consecutive years of revenue and cost data. We also used one year's signal and control data in the Ethio- Djibouti railway. In this study, using techno-economic analyses including net present value, internal rate of return, and payback period as economic indicators, we assessed the overall economic assessment of CBTC technology adoption. Finally, as the results of the study show, adopting CBTC technology on Ethio- Djibouti Railway allows the organization to increase competitiveness and economic returns. In addition to this, the study suggests that the use of CBTC on the railway can improve the safety of the train and faster train operation performance by increasing the ability of railroad lines, particularly in local and regional markets.
Design, Modeling and Analysis of Roof Top Photo v oltaic System for Ethio Djibouti Railway Passenger Trains
(Addis Ababa University, 2024-03) Eliyas Dejene; Getachew Biru (PhD)
The growing demand for electric railway transportation worldwide has led to a rise in power consumption by the transportation system . Hence, providing sufficient, cleaner, and less expensive energy to the transportation system is important to cope with the increasing energy demand. In Ethiopia, the Ethio Djibouti railway trains consume huge amounts of energy from the national grid for their propulsion and auxiliary services. As the demand for this energy continues to rise, it is crucial to research and explore innovative solutions to meet the increasing energy needs. One potential solution is harnessing solar energy from train rooftops, which can supplement the energy requirements and reduce the stress on the national grid. By adopting this approach, we can alleviate the burden on the grid and enhance the reliability of the power supply. This research presents a new design and model of a rooftop photovoltaic system for Ethio Djibouti railway passenger trains. To fulfill the research objective, the solar irradiance function of the train travel schedule across the train route is collected from the European U nion weather forecasting web . Following that, the train rooftop PV capacity in contrast with the electrical load demand of the trains w as analyzed. Based on the load and PV capacity available, the PV system is optimally sized with an appropriate energy control strategy Additionally, the PV panels' weight and efficiency are considered during the design phase to improve the practicality and feasibility of the system. Finally , the designed system is modeled and simulated using MATLAB to validate the performance level of the PV system. Th e research findings reveal that the designed train rooftop p hoto voltaic system can produce up to 393.6 kW However, energy output is influenced by the train's departure time and location. T he designed rooftop PV system can contribute up to 21.318GWh of electric power to E thio Djibouti railway passenger trains and yield a net profit of 247,607 USD in its lifetime . Additionally, the return on investment value of the PV system is 3 49 %%.
Assessing Railway Property Theft and Developing Engineering Protection Mechanisms: A case Study of Addis Ababa Light Railway Transport Service Enterprise and Ethio-Djibouti Railway
(Addis Ababa University, 2024-06) Silenat Asrat; Getu Segni (PhD); Biniyam Ayalew (Mr.) Co-Advisor
Ethio-Djibouti railway line run from Addis Ababa to Negad, the port of Djibouti. Ethiopia also built light railway transport in Addis Ababa, capital city of Ethiopia. The construction of this rail infrastructure is essential for the development of both countries. However, after the operation start both the Addis Ababa light railway transport service and Ethio- Djibouti railway lines faced so many challenges due to different safety and security issues including theft on their property that challenge the transport service. The seriousness of theft in railway industry cannot be ignored. It highly deserves immediate notice and action. The curse's accompanying damages to the railway property are irreversible. Theft related issues cause businesses to lose millions of dollars' worth of property. This paper aimed to identify and set solutions to these major problems by developing protection mechanisms. The study further identifies the characteristics and the leading causes that motivates criminals to railway property theft. Quantitative methodological approach was adopted to accomplish this work. Both primary and secondary data were used as a source of information for the study. Primary data was taken from participants by using questionnaire survey. Secondary data was taken from AALRTSE and Ethio-Djibouti railway recorded data on occurrence of theft over the year 2018 to 2023. Quantitative analysis was conducted for both primary and secondary data sources. There were 2233 occurrence of theft to railway assets over the study period. The characteristics of criminals and property theft was identified. Numerous hotspot areas have been discovered using the information. This paper also presents that availability of scrap metal dealers and poor enforcement of law against criminals are among the top most leading cause to railway property theft and then developing solutions to prevent this issue. Previous literatures are failed to set solutions as the culture of the given systems. Due to the limited literatures related to railway property theft, developing new protection mechanisms are taken to solve the issues on railway. The findings will guide efforts to improve the safety and security of railway asset. The study recommends that the railway industry to develop a multi-stakeholder partnership strategy. In conclusion, the extra loss of costs by the Ethiopian railway industry is eliminated and solved. Once the security problems are solved the maintenance costs will be reduced once the location is identified providing the possible solution for the find out problems.
Thermomechanical Modeling and Analysis of Rail Vehicles Disc Brake with Nonaxisymmetric Finite Element Method
(Addis Ababa University, 2024-06) Kejela Temesgen; Demiss Alemu (Assoc. Prof.)
Braking could have unfavorable consequences, including disc thickness variations, thermal judder, crack, fade, surface wear, and limited service life as a result of thermal fatigue. To counteract such damaging consequences, accurate prediction or determination of temperature is fundamental in the design stage and during operation and maintenance. Eventually, several FE (finite element) models have been attempted to assess the temperature, stress, and fatigue life prediction of disc brakes. Despite this, the spatial variations of heat input load and boundary conditions are not adequately taken into account in these models. Hence, accurate detection of failure in the design stage and during preventive maintenance is a key problem. In this dissertation, an FE-based non-axisymmetric moving heat source (NAMHS) algorithm that takes into account the temporal and spatial change of thermal load and boundary conditions is developed, and implemented in disc brake geometry and material selection, as well as in evaluating the effect of braking energy. All input geometric parameters and braking conditions implemented in thermomechanical modeling are extracted from the trailer and motor bogie of Addis Ababa Light Rail Transit (AALRT). ANSYS parametric design language (APDL) is implemented in coding the variations in thermal loads and the corresponding boundary conditions, both spatially and timely. The model constitutes three separate analyses: thermal, mechanical (stress assessment) and fatigue life. To consider space and time variation in heat input and boundary condition, NAMHS is executed by the APDL programming model, similar to FORTRAN written commands. Once the model is seen successful in disc brake analysis, its applicability in other research areas is tested in three ways: comparative analysis geometry selection, examining the effect of braking energy, and disc material comparative analysis. The consideration of radial distance in the NAMHS model algorithm showed surface temperature variation as high as 10% and 60% compared to traditional FE models of moving heat source and axisymmetric, respectively. Besides, the partition of friction surface area into the heat input and convection in NAMHS resulted in maximum circumferential variations of temperature, von Mise stress, and fatigue life prediction as high as 49°C, 46MPa, and 2000 life (braking times), respectively. Moreover, the friction surface is exposed to radial stress variations from tensile stress of 20MPa to compressive stress of -125MPa. Stress variation between the leading and trailing edge of the pad trace due to deceleration is illustrated 5ᵒC and 3MPa on late-braking times, respectively. The applicability test of the NAMHS model algorithm revealed encouraging outcomes. Although the maximum friction surface temperature seems similar, its variation is highlighted higher in the original disc geometry, compared to the modified. Unexpectedly, the original disc’s stress is found more than twice the stress found in modified disc geometry. Besides, the braking energy variation prevailed in emergency braking of the motor bogie revealed twice the strain range in the motor bogie, compared to the service brake in the trailer bogie. And, its applications in material selection displayed cooling times as the main factor. Finally, the NAMHS model algorithm is applied to experimentally and analytically studied solid disc brakes, and successfully validated. Therefore, this finding has drawn our attention to the significance of considering the spatial variation of heat source in a modeling disc brake, which couldn’t have been supported in traditional models. The results reported here suggest that the NAMHS model algorithm could provide convincing evidence and a reliable estimate of where a maximum temperature and stress were observed, and where a crack could be initiated. Hence, this study provides a first step towards a realistic and comprehensive representation of FE modeling, which could be implemented in failure prediction. Hence, this NAMHS finding will help us to predict thermal fatigue life in a better way, compared to any traditional modeling. And, the model should find a broad range of applications in conducting comparative analysis of geometries and materials under any braking type. We hope that our finding could influence disc brake manufacturers, researchers, and maintenance personnel in disc brake damage investigation. Furthermore, the proposed model could be easily implemented and suitable in the area of linear or tangential sliding frictions in addition to disc brakes. These might include, but not limited to thermal and stress analysis of tread brakes, drum brakes, engine pistoncylinder, and camshafts are just to cite a few of its application areas.
Study on Improvement of the Existing Power Reliability of Addis Ababa Light Railway Transit
(Addis Ababa University, 2023-08) Eleni Sisay; Getachew Biru (PhD)
The DC Railway Traction Power Supply System is a widely used technology around the world, particularly in urban and inter-urban regions. The system operates on standard DC traction voltages of 750 V, 1500 V, and 3000 V, which require less electrical clearance than the AC Railway Traction Power Supply System catenary. However, power interruptions can have a significant impact on the system. In the case of AALRT, frequent power interruptions led to thousands of passengers being evacuated from subway cars and stranded at stations. This tesis analyses the reliability of the Addis Ababa Light Rail Transit (AALRT) Traction Power Supply System (TPSS) using interruption data collected from AALRT, Ethiopian Electric Power (EEP), and Ethiopian Electric Utility (EEU). The data includes the number of customers interrupted, number of trips cancelled due to power interruption, daily number of customers served, daily customer interruption duration, number of times the power interruption occurred, number of passenger flow in both lines, and number of passengers interrupted. The causes of power interruption from EEP and EEU sides and duration of power interruption from incoming line 132/15kV are also included. Then, reliability indices are calculated and analysis results indicate that the highest mean time between failures (MTBF) was 2688.98 hours on the East-West (EW) line in 2019 G.C. and 4705 hours on the North-South (NS) line in 2020 G.C from the collected data. The highest duration of power interruption recorded was 804.47 hours on NS in 2019 G.C, and the highest frequency of power interruption recorded was 154 interruption/year on NS in 2020 G.C. In this thesis, two power reliability improvement technologies, substation reconfiguration and distributed generation, were analysed. The thesis was modelled in Matlab Simulink and the results were compared and best reliability mitigation techniques were identified. Substation reconfiguration by using redundant line has been found the best alternative for improving the power reliability for AALRT. As per the model developed, system average interruption frequency index and system average interruption duration index of 10.0490 interruptions/year and 24.0280 hr/customer/year, respectively have been achieved. This method is optimal in terms its applicability and cost.
Modeling the Safety Conditions of a Railway Line: The Case of Ethio-Djibouti Railway
(Addis Ababa University, 2023-07) Kalkidan Teshome; Yonas Minalu (PhD); Biniyam Ayalew (Mr.) Co-Advisor
The Ethio- Djibouti railway line run from Addis Ababa to the port city of Djibouti (Negad). The construction of this rail infrastructure is essential for the economic growth and development of both countries. However, after the operation start the Ethio- Djibouti railway line faced so many challenges due to different safety issues that challenge the train speed to travel at less than the designed speed. This thesis concerns identifying and setting countermeasures for the major safety problem by developing a model. Safety problems are incidents that lead to accidents, collisions, and death. This is done by taking previous data, questionnaire results, and field data from video cameras that were installed on the train (CCTVs if any) and locating the major Land use accident analysis area by using QGIS and then developing a solution on the major accident locations. From other literature underpasses, overpasses, or providing fences on the railway crossing and implementing government laws are considered the major solution to prevent safety issues on railway property. So by considering the Ethiopian people‟s culture of living, developing new countermeasures are taken to solve the issues on the Ethio- Djibouti railway. Finally from this thesis, the extra expense cost by the Ethiopian Railway Company is deducted and solved. Once safety problems are solved the Compensation cost, unplanned purchasing cost, and also maintenance costs will be reduced, especially the compensation cost for the mortality of animals and person will be reduced once the location is identified providing the possible measures for the find out problems.
Passenger Ride Comfort Analysis of a Rail Vehicle Running with Polygonized Wheel Using Dynamic Simulations (A case study of Addis Ababa Light Rail Transit)
(Addis Ababa University, 2023-07) Mazuri Erasto Lutema; Haileleoul Sahle (PhD0
The railway transportation system is currently undergoing a significant expansion. As a result, train lines are upgraded, and the technical condition of the rail vehicles that use them is also taken into consideration. However, under certain circumstances, wheels on rail vehicles may sustain damage while in use. Then, depending on the kind and degree of flaws, the profile of the wheels is no longer circular but rather changes. The passenger's ride comfort is diminished when a rail vehicle with a damaged wheel is in operation. The research considered one type of railway wheel damage, which is wheel polygonization, and focused on analyzing the ride comfort for passengers based on results obtained from multibody dynamic analyses. Simulations and calculations were done in numerical and dynamic multibody software. The findings demonstrate that the wheel polygonization of 0.3 mm has a greater impact on ride comfort compared to the other amplitudes (0.1mm and 0.2mm). This implies that with an increase in polygonization amplitude, the ride index will also increase. However, running an overloaded carrying capacity vehicle has minimal comfort compared to an empty and rated carrying capacity vehicle when the wheel has a polygonization defect. Moreover, it found that with increasing vehicle speed, the ride index also increases, which means that at high speeds, the ride comfort will be diminished. Furthermore, it found that the orders of wheel polygonization have an effect on ride comfort. With the increasing order of polygonization, the ride index also increases. According to the findings, this study has a significant impact on the maintenance planning for wheels and rails as well as operation management.
Positive Train Control with Headway Optimization on an Active Communication System-a case study of Addis Ababa Light Rail Transit
(Addis Ababa University, 2023-08) Mohamed Ali Hussein; Yihenew Wondie (PhD)
Reducing rail transit's headway effectively is of enormous practical value since it plays an increasingly significant part in the public transportation system. Some of the most important goals in railroad operations include safety, capacity, and timely schedules. The idea behind positive train control (PTC) is to use cutting-edge 2 information technologies to increase the safety and effectiveness of railroad operations. Except for increasing the average waiting time, headway irregularity may also result in additional energy consumption and more delay time. Active communications and other information technologies enable the deployment of a dynamic headway, which can increase track capacity and dispatching effectiveness while also enhancing safety. Minimum headway, which is the optima Interval time the following train can reach while tracking the lead train, is considered to be one of the main factors restricting operational capacity. We can run with better headways without increasing the operational speed; for example, the Addis Ababa LRT currently uses 15 minutes of headway when the speed is averaging 20-70 km/h. The calculated results show that this significant headway can be reduced by up to 4 minutes without slowing down operation As a result, dynamic headway control cannot be represented using existing modeling techniques that use fixed headways, especially when the dynamic headway only comprises a small portion of a single block. Minimum headway shall be a minimum period of time required for the station to carry out requisite train arrival and departure operations, which it is also essential that trains operating in this area are safe.
Reliability and sensitivity analysis of multibody system due to uncertainty parameters. A case study of Addis Ababa Light Rail Transit
(Addis Ababa University, 2023-08) Murungi Rodger; Haileleoul Sahle (PhD)
A multibody system is one of the complex mechatronic system whose dynamic performance is influenced by its connected components and the mechanical structure. However during the service life, the system is subjected to degradation of different components whose conditions may greatly impact the vehicles running characteristics like stability and reliability. The suspension system is one of the systems that ensure better and reliable running behaviors are achieved and hence any uncertain changes in its characteristics becomes of significant interest and must be treated with utmost attention. Hence this research aims carrying out reliability and sensitivity of multibody system due to uncertainties in the suspension system and provides a model which can be applied to evaluate the performance of the vehicle in terms of variation of suspension design parameters. The vehicle is modelled using SIMPACK dynamic software, incorporated with track irregularities from maintenance data and using statistical tools to vary suspension design parameters. The dynamic performance of the vehicle is evaluated by using dynamic indexes like derailment coefficient and vibration sensitivity to assess the level of reliability and sensitivity of the vehicle. The results showed that the running safety reliability is more sensitive at low values of damping and stiffness of the primary suspension and stability is achieved as they increase while vibration sensitivity increases with increase in damping and stiffness values of both primary and secondary suspension. Furthermore secondary suspension damping and stiffness greatly influence vibration sensitivity as opposed to primary suspension damping and stiffness which exhibits little influence on vibration sensitivity hence secondary suspension damping exhibits the greatest influence on vibration sensitivity while primary suspension stiffness exhibits the least influence on vibration sensitivity.
Investigation of Conflicts Between Railway and Road Network Interaction and Their Impacts on the Operation: The Case Addis Ababa Light Rail Transit
(Addis Ababa University, 2023-07) Sibomana Aime Alphonse; Girmay Kahssay (PhD)
Due to quick financial growth, Addis Ababa city has a high traffic issue, which affects the movement of pedestrians, goods, and tracks where business is also affected. Addis Ababa Light Rail Transit (AALRT)has been involved in solving the problem. This research aims to investigate economic, social, and traffic conflicts caused by the alignment of AALRT and road network, suggest solutions for each conflict investigated, and mitigate for the next LRT project to avoid conflicts. Scenario 1 considered railway and road networks combined, and scenario 2 considered roads without LRT. The parameters for social conflicts were: pedestrians waiting time to cross, pedestrians travelled distance to access the next crossing level, the walkway distance between the railway and road network, safety and security at the crossing level, waiting area before the crossing level, and peak hours effects. The economic conflict parameters were: business owners crossing for services, vehicle supplying goods access to shops, customers and business owners’ vehicles access to shops and Railway alignment contribution on business around, interviews and questionnaires have been delivered, and statistical package for social science (SPSS) has been used to analyse the respondents’ feedback in qualitative aspects and Excel for quantitative aspects. After comparing the parameters of both scenarios, the following conflicts have been shown: long distance travelled to reach the crossing, long waiting time before crossing, insufficient walkway area between railway and road, insufficient security and safety signs at the crossing, difficulties of the vehicles to access shops and traffic congestion at turn bay. Solutions to the investigated conflicts are: to provide an inclusive pedestrian flyover bridge on every 150 m to 200 m of LRT and road network, to provide a walkway of 1.5 m width between railway and road, to install a signalling system at every crossing, to provide vehicles turn bay for freight vehicles and passengers’ vehicles on every 350 m of the systems which will make business easy and feasible. The future project must do a clear investigation during the planning phase; using tunnels and bridges to avoid alignment conflicts is better. The most cost-effective solution is constructing a turn bay that can be used as a zebra crossing and providing a signalling system at every turn bay. The other research can be focused on the design of suitable flyover bridges and turn bays.
Design of Synchronous Reluctance Motor for Light Rail Transit Traction
(Addis Ababa University, 2023-08) Takunda Victor Gadza; Abebe Teklu (PhD)
Trains play a crucial role in modern society transporting a significant portion of the freight and passengers transported worldwide. With increased urban populations, Light Rail Transit (LRT) systems have become one of the important means of transportation for large populations. Therefore, finding less expensive, reliable, and efficient ways of operating these trains is pivotal. In addition, there has also been a huge drive toward environmental conservation. This has resulted in standards and regulations that advocate for increased energy consumption efficiency and cleaner energy sources to reduce pollution-related environmental damage. Traction motors are one of the areas where these improvements may be introduced. Various types of traction motors have been used that include Direct Current (DC) motors, Alternating Current (AC) Induction Motors (IMs), and Permanent Magnet Synchronous Motors (PMSMs). However, these motors have shortcomings, such as inefficiencies in IMs due to rotor losses and expensive material costs in PMSMs due to rare earth permanent magnets. Therefore, finding alternatives with better efficiency and less cost is of paramount importance. One alternative is to replace the IM and PMSM with the Synchronous Reluctance Motor (SynRM). Therefore, this thesis designed a SynRM motor and drive system that can be used for the LRT application as an alternative. The design process includes investigating LRT traction requirements, investigating SynRM characteristics, design of a SynRM model for the LRT, optimizing the model’s performance, and evaluating it using Finite Element Analysis (FEA). The motor was designed for the Addis Ababa Light Rail Transit. A control for the SynRM was also generated using SyR-e software and simulated. The SynRM performed comparably to the reference IM with a 4% higher torque output and 5% higher efficiency. It is also three times smaller in volume, weighs 50% less, and the material cost is 40% less than the reference IM. However, the designed SynRM has less power factor than the IM. This is due to the rotor needing a high level of magnetization, leading to an increase in reactive power. This increase in reactive power can then cause a decrease in the motor's power factor.

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