DSpace Collection: Thesis - Road & Transport Engineering

Standardization of Guidelines for Railway Track Infrastructure Subsystem for Railway System of Ethiopia

Wed, 13 Feb 2013 11:55:46 GMT

Title: Standardization of Guidelines for Railway Track Infrastructure Subsystem for Railway System of Ethiopia

Authors: Yeserah, Gebeyehu

Abstract: Railway transportation, which is needed in the achievement of effective development, is an efficient, cost-effective and it is environmental friendly transport system. In addition to the low railway network connectivity in Ethiopia like other developing countries, the available one is not modern; has low capacity and is insufficient to facilitate transit trade; and also Ethiopian railway transport has not standardized guidelines to design the system. In this study an attempt was made to standardize guidelines for railway track infrastructures specifically track geometric parameters and track structural elements for conventional lines in Ethiopia. To achieve such objectives the research had a methodology of a task involving literature review; discussion and comparison of different country standardization practice; and different data collection that contribute for standardization of guidelines for railway system in Ethiopia. Standardization of guidelines for different track infrastructure subsystems for Ethiopia context was done based on topography, climatic condition and availability of track construction material, and different literature reviews. Track cant of a normal limiting value of 160 mm was recommended to reduce or eliminate lateral acceleration created due to small curve in difficult topography of Ethiopia. In addition a cant excess of as small as 70 mm was recommended in avoiding damage of low rail by heavy freight train; and correspondingly this can be achieved by increasing the value of cant deficiency for fast train. A gradient of up to 3.5% and/or greater value was recommended for lines constrained by topography. Even if the selection of steel rail grade is based on avoiding rail wear and rolling contact fatigue; standard steel rail strength i.e. R260 is recommended for all lines including for the whole range of curvatures due to high investment cost of higher quality steel grade that are recommended for sharp curves (curves are suffering from high rail wear). On the other hand, the recommended method of selecting fastening systems is a matter of satisfying safety of the lines. The specification of ballast and subballast depend on the availability of track construction material; and the track construction material availability in Ethiopia is, more or less, not a problem in construction industry even in the eastern part of Ethiopia where inadequacy of construction material are expected. An attempt was made to find a suitable range of ballast gradation which fulfills the objective of good strength (well graded) without significant reduction in permeability of ballast (uniform graded) using a coefficient of uniformity between 2.2 and 2.6, moderately graded ballast was recommended. In addition the specification of subballast material was determined based on filter principle of drainage criteria using subgrade material size distribution. The problematic subgrade soil, placed under subballast, should be replaced or improved to achieve the required strength characteristics of subgrade layers. The appropriate type of tests was selected to define the characteristics of each track substructure layers (ballast, subballast and subgrade soil).

ASSESSING & QUANTIFING THE LEVEL OF TRAFFIC CONGESTION AT MAJOR INTERSECTIONS IN ADDIS ABABA (A CASE FOR EAST-WEST CORRIDOR)

Wed, 06 Feb 2013 08:59:42 GMT

Title: ASSESSING & QUANTIFING THE LEVEL OF TRAFFIC CONGESTION AT MAJOR INTERSECTIONS IN ADDIS ABABA (A CASE FOR EAST-WEST CORRIDOR)

Authors: Wondwossen, Taddesse

Abstract: Traffic Congestion is an ever growing chronic problem in the transportation system soon after the invention and mass production of automobiles. All major cities both in developed and developing countries are facing the problem due to increasing travel demand which follows economic and population growth. Traffic congestion directly affects commuters with an increased travel time, excessive delay in a queue, increased fuel cost, delay for important appointment and job, loss in productive hours; and it indirectly affects the living standard and the environment as well. Hence, traffic congestion cause upon road users and cities to incur a significant amount of money for both economic and social costs. Quantifying the level of the traffic congestion and understanding how much effect and cost are being incurred due to traffic congestion; hence, will be important for making improvement decisions and evaluate implemented mitigation measures. Following the economic and population growth in Addis Ababa, traffic congestion problem has emerged and the problem is even growing faster. In this study, the level of the traffic congestion in Addis Ababa city was quantified using travel time approach. The city’s one of the most congested East-West corridor was considered and travel time, traffic volume, and vehicle occupancy data were collected at four midblock and four intersections. Accordingly, the travel rate, the delay rate, total travel delay (Veh-Min and Per-min), buffer index and planning time index were calculated. And also, the average hourly travel rate is correlated with the average hourly traffic accident data and congestion spots and accident black spots were plotted on the GIS map to see the relationship between the traffic accident and traffic congestion. Accordingly, the result showed that on average about 18,000 Veh-min or 38 Veh-day and about 169,000 Per-min or 352-person-day are wasted at each major intersection entry and the city incurs annually about 5-8 Million Birr per intersection only for vehicle and fuel cost. The result also showed that the city’s traffic accident rate correlated with travel rate better than traffic volume and the congestion spots identified from questionnaire data conside with the black spots identified by the national road safety agency.

Software Development for the AASHTO and ERA Flexible Pavement Design Methods

Fri, 28 Dec 2012 09:06:06 GMT

Title: Software Development for the AASHTO and ERA Flexible Pavement Design Methods

Authors: Amare, Setegn

Abstract: In Ethiopia the number and type of traffic increases and the change is alarming. This leads to the construction of road infrastructures which needs economical and safe design of roads. Nowadays, flexible pavement roads and surface failure before the expected design period has become a critical issue in our country. The design in our country is based on the prevailing condition of soil and materials report using the Ethiopian Roads Authority (ERA) Pavement Design Manual where the results obtained will be compared with that of the AASHTO Structural Design Pavement manual. Finally, the thickness obtained using both design guides will be compared. And it is known that pavement thickness design in our country is manual based. Manual design method has a drawback in avoiding human mistake, error and doing many alternatives for comparison as flexible pavement design involves different nomograph, charts, tables and formulas so it is cumbersome and time taking practice which may result in unsafe or uneconomical design. The development of the software is using MATLABR2008b programming language. And the goals achieved are the thicknesses of surface, base and subbase layers of flexible pavement roads are determined and different design charts, default values and tables are digitalized. Furthermore, comparison between AASHTO and ERA methods in terms of thickness and construction cost can be made to select the best design alternative. Besides, the designer or researcher can do as many alternatives as needed in short time. The result obtained by the developed software (AASHERA) is verified by comparing with the manuals and examples from different books. And the analysis results turn out to be successful when it is compared with the manuals and books calculation.

INVESTIGATION OF THE PERFORMANCE OF UNSEALED ROAD SUB BASE MATERIALS USED AS WEARING COURSE OF GRAVEL ROA

Thu, 27 Dec 2012 13:16:29 GMT

Title: INVESTIGATION OF THE PERFORMANCE OF UNSEALED ROAD SUB BASE MATERIALS USED AS WEARING COURSE OF GRAVEL ROA

Authors: SIMENEH, MERGA

Abstract: A good road structure may help in reducing the number of accidents. Wearing course is the top layer of the road structure which is the layer exposed to the vehicle tyre and environment. The international roughness index and Present Serviceability Index are both indices that can be used as indicator of road roughness and serviceability. Objective of the study is primarily to determine the performance and the durability, serviceability and service life of unsealed gravel road wearing course above sub grade. In evaluating the serviceability of the road, roughness is an important indicator of pavement riding comfort and safety. It is condition indicator that should be carefully considered when evaluating pavement performance. At the same time, the use of roughness measurements plays a critical role in the pavement management system. There are many devices used for roughness evaluation. In this thesis, roughness measurement was done by Merlin manual instrument. The methodology used to carry out the thesis work is carry the field data measurement for roughness and gathering user assessment for the case study site and taking sample data of soil for strength test of CBR. International roughness index was measured by using Merlin roughness index measuring instrument. And used for calculating present serviceability index as independent parameter. Both international roughness index and present serviceability index were measured along 200m section of the road for about 19.7km of the study route. This studies only focuses on one type of road which was gravel pavement located on western part of Ethiopia in Benishagul Gumuz regional state in Kamashi Zonal state. The work has generated that this unsealed gravel road is running with in the design limit without sever deterioration as the result of serviceability, user assessment, CBR strength test and roughness value shows.