Browsing by Author "Bethelhem Bekele"

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    Finite Element Analysis of Rail Bending Stress and Deformation Under The Effect of Unsupported Sleeper
    (Addis Ababa University, 2023-06) Bethelhem Bekele; Celestine NKundineza (PhD)
    Ethiopia, one of the developing countries in the world, has put large affinity towards basic infrastructures like buildings, roads, power supplies needed for the society wellbeing. Among these, railway is one mode of transportation. In several countries, the traditional railway track system is the ballasted track, i.e., consists of rail, rail pad, and concrete or wooden sleeper on ballast and sub-grade. Railway sleepers and ballast are the main structural elements of railway track. The ballast-sleeper interactions include pressure distribution and load transfer to ballast, railway sleepers are aimed to maintain track gauge, guarantee lateral stability of the track and contribute to better geometrical conditions of the track. However, in the case of lose sleeperballast contact, these function of the interaction will be affected. This study examines the effect of rail vehicle speeds and unsupported sleeper as a result of ballast stiffness variation on rail stresses and vertical displacements. The Finite element model which was composed of a single train wheel rotating on a rail supported by evenly spaced five sleepers, laid on a 300mm thick ballast layer, was used. The results show that the decrease in ballast modulus leads to an increase in rail deflections. It is also found that increase in speeds results in an increase of rail deflection and stress. For the deflection of the rail as the speed increases the deflection also increases. In this project considering the speed variation for example at ballast modulus of 120 MPa, for the speed of 20, 40 and 80Km/hr the deflection are 0.187, 0.207 and 0.266mm respectively. In the presence of unsupported sleeper, the rail bending stress increased by 32% and the maximum von-mises stress on rail which is 181.52 MPa occurred when the ballast modulus is 90MPa with a rolling speed of 80Km/hr. For a train moving on 80Km/hr speed, the rail bending stress increases from 51.12 MPa to 72.23 MPa in the existence of unsupported sleeper.