الفهرس 
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Abstract
Railroads provide one of the most important means of transportation in the world. The railroad infrastructure. primarily the railways tracks, has inevitability suffered from greater economic demands requiring heavier train axle loads and faster operating speeds. These heavy trains and/or high speeds are likely to push the conventionally constructed ballast-tie type track structure closer its limits regarding sustained long term stability and geometry.
The main objectives of the slab track (ballasted track) structure type are to reduce the maintenance costs and the maintenance occupations. Many research p efforts involvinu experiments with solid concrete track-beds (slab type track structure) in the field and laboratory, have taken place throughout the world. Despite of the extensive efforts that are being conducted to investigate the behavior of the slab track, the analytical models for understanding its behavior are still far from well developed. The development of techniques and criteria for track design is an important part of the rail supporting technology program.
In this thesis, a new process to apply the finite element techniques for analyzing the slab track structure responses to static loads is developed. An extensive theoretical study of the slab track and its response to a wide range of loads, rail sizes, axle spacing. fastener spacing and resilience, slab dimensions and different subgrade types, is presented. Some simple experimental tests are employed for the verification , of the developed theoretical models. Calculations of the stresses and deflections for both types of the track structure, the conventional ballasted tie type structure and the slab type track structure are included in the thesis.
The theories and methods used for the determination of the stresses and deflections of the ballasted tie type track structure are reviewed, starting with the Winkler foundation analysis through to the use of the finite element method as an improved analytical technique that can deal with any special problem. These problems include those that are difficult for other methods to analysis due to their limitations. Here in this thesis, the analysis of ballasted tie type track structure is
done by ustnv the finite element technique, representing the track as a continuously elastic supported beam and using Mecham.s representation tbr the track modulus.
Slab track has different concepts to different people and therefore the first decision in its design is to select the general contiuuration of the track. For this objective, the evaluation of the slab track structure includes descriptions ()Isiah structures now in use in many countries. followed by the review of different thstenine types and the design features of slab track. I [owever, the study included not only the slab track but extended to all ballastless tracks.
The logical design of slab type track involves the determination of the pressures and strains imposed on all elements of the track structure, followed by a determination of the allowable stresses and strains that the various elements can withstand.
In this thesis, the analysis of the slab type track is done: Firstly, by using the mathematical models presented in Iletenyi for a beam of infinite length supported continuously along its length on an elastic foundation. As common representation of the foundation is the vertical pressure proportional to the vertical deflection of the slab. The subgrade is characterized by a subgrade modulus. Secondly, by using two dimensional finite element technique to model the slab track as a continuously elastic supported beam, this model facilitate the analysis of the slab track for any type of boundary conditions, deals with the actual position of the wheel load concerning, fastener locations, and has much lower cost than the three dimensional finite element model. A good agreement between the previous two methods is found when the comparison is made. Thirdly, by using the three dimensional finite element technique to model the slab track. This model developed to get the strains of the slab in longitudinal and transverse directions. Finally, by using some experimental tests to simulate the response of the slab track to loading under laboratory conditions.
The thesis includes many applications on different types of trains, rail sizes, fastener spacing and resilience, different dimensions of slab, different types of soil. Also, it includes comparison between the mathematical model and the finite element model, in addition to a verification of the theoretical models by using the experimental tests.
The thesis reached to the follow-me .( I) the newly developed finite element model appears well suited for the analysis of the slab track structure and is capable of handling many problems. (2)the finite element model results are closer to the experimental test results than the results calculated by the mathematical model based on I letennvi. (3) A izood representation of the deflections and stresses for all components of the track with a wod accuracy. (4) A better understandin2 of the behavior of the slab track.