فهرست مطالب

Advances in Railway Engineering - Volume:3 Issue:1, 2016
  • Volume:3 Issue:1, 2016
  • تاریخ انتشار: 1395/02/20
  • تعداد عناوین: 5
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  • Masoud Yaghini*, Hasti Jafari Pages 1-8
    Regarding the importance of competitive advantages among the transportation systems, improving the costumer’s satisfaction is an important factor in attracting them to these systems. In this research, we focus on the effects of constructing new stations on users and a new mathematical model is proposed for this problem. In the proposed model, two simultaneous effects on customers by constructing new stations are investigated. One effect is the improvement of the demand access to the railway network and the other one is related to the increase in the travelling time for customers sitting in the train. As the first effect, the less the customer’s distance to the stations, the more attractive to use this system and the second effect concerns the increased in the traveling time in new stops which may result to customer’s dissatisfaction. The proposed mathematical model achieves the time optimality, furthermore; it maximizes the covered population to locate the stations. For locating the optimal site for new stations, we need to apply the population usage information. The proposed model is examined on the Mashhad’s subway as a case study and the results are reported.
    Keywords: locating new railway stations, traveling time, covering model, accessibility model
  • Nazmul Hasan Pages 9-14
    This paper deals with the threshold radius that warrants the use of single restraining rail for transit and railroads. Different railways use different threshold radius from 91m to 365m to provide restraining rail. These threshold figures are probably experience driven choices. The need for restraining rail may be related to a so-called derailment alarm coefficient of 1.2 sustained over 2m length (According to UIC leaflet 518 a safe maximum value of Y/Q ratio of 0.8 over the length of 2m is recommended) but it needs a wheel/rail interaction software to estimate derailment coefficient. The author is not aware if it has been done for this purpose. A quick and simple assessment method is developed here. A restraining rail reduces the angle of attack (AOA) to reduce the likelihood of wheel climb derailment and to reduce wear provided it is installed close enough to the inner (lower) rail to prevent flange contact with the outer (higher) running rail. Angle of attack depends on wheel base, curve radius and free play. The threshold radius is formulated by considering these three parameters. An assumption made to derive the equation is that twice the AOA on tangent track due to free play is a critical AOA on circular curves to warrant a restraining rail. The assumption is validated by comparing the threshold radius obtained by the formula with real world examples. It is also shown that curvature resistance of the threshold radius is too high to warrant a restraining rail. If the radius of the curve is less than threshold radius then the restraining rail needs to be extended into the spiral up to a point where the radius matches with the threshold radius. A formula substantially based on current practice is given to determine the extension of single restraining rail into the spiral subject to a minimum requirement.
    Keywords: track Geometry, Track design, Y, Q ratio, wheel, rail interaction, thresholdradius
  • Hasan Abbasi*, Hooshang Katebi, Masoud Hajialilue Bonab Pages 15-26
    Nowadays deep excavations are needed for construction of foundation of high rise buildings, providing space for parking and etc. In some cases deep excavations may be constructed in the vicinity of the subway tunnels and causes unpredicted extra displacements and internal forces in tunnel lining of tunnels which were not designed for them and consequently affect serviceability of tunnel. Therefore in order to avoid structural damages, comprehensive studies should be carried out when the excavation is located in adjacent of tunnel and necessary precautions should be adopted. In this paper 2D FDM software FLAC 2D was used for modeling and investigating the effects of excavations on existing tunnels in sand layer. In this analysis it is assumed that the cross section of tunnel is circular and tunnel exists before deep excavation and also stress relaxation in the soil body around tunnel was taken into account before installation of tunnel lining. In this study different locations of excavation with respect to the tunnel were taken into account and effects of excavation on induced displacements and changes of internal forces of tunnel lining have been studied. Diaphragm wall is used for retaining of excavation and in the analyses Mohr- Coulomb constitutive model is used for soil body. The results of 2D numerical analyses show that when tunnel is located in the outside of the excavation, because of the shielding effect of the diaphragm wall, excavation has less effect on tunnel in comparison with the tunnel which is located below the excavation.
    Keywords: Deep Excavation, Tunnel, Numerical modeling, Finite Difference Method
  • Meysam Naeimi*, Rolf Dollevoet Pages 27-37
    The ability to perform rolling contact fatigue (RCF) experiments in wheel–rail material is provided by a new small–scale test rig, manifesting the actual dynamic behaviour of the railway system. In this paper, a multi-body dynamics (MBD) model is proposed, simulating the vibration behaviour of the prescribed rig. The new testing facility is modelled using a three-dimensional model of the vehicle-track system in MBD environment. This computer model, implemented in MSC Adams, represents the main components of the test rig, and evaluates their dynamic functionalities. The model is developed by coupling the MBD approach with the finite element method (FEM). It provides the capability of performing time–domain simulations under various loading conditions. By applying the geometric profile of the rail under a sample of V-shape defect, dynamic responses of the test rig components are obtained. Using a pulse load function, the rail defect is simulated by the imaginary motion of the wheel over the defected rail. Performing a modal analysis using a mixed model of the MBD–FEM, the main dynamic characteristics of the system are determined. The results of analysis show that, the MBD–FEM simulation can only deal with low–frequency vibrations of the components, even if rail defects with relatively small wavelengths are applied as the source of dynamic excitations.
    Keywords: Test rig, multi, body dynamics, Finite Element Method, wheel–rail contact, rail defect
  • Abdullah Demir* Pages 39-47
    This article is concerned with the static analysis of structural cables used in railway overheads. Structural analysis computer program named ANSYS is used for analysis. Two effects are considered in the analysis. First one is the bending behavior effect of cables. BEAM188 in addition to LINK10 and LINK180 is used to see the difference in case of additional bending effect. Besides, LINK10 and LINK180 is also compared. Second one is the effect of pantograph. Pantograph is modelled as a contact element instead of a force. Accordingly, some sample cable systems similar to railway overhead are analyzed.
    Keywords: Railway overheads, structural cable, sliding contacts, nonlinear analysis