The Effect of Rail Defects on Track Impact Factors

This paper investigates the effect of rail surface flaws on track impact factors for different track and vehicle conditions. For this purpose, a three dimensional vehicle and track as an integrated system modelled. The vehicle, consists car body, bogie frames and wheelsets, is able to model displacements in vertical and lateral directions. Hertz nonlinear springs utilized to connect vehicle to track structure and simulate the interaction between vehicle and track subsystems. Track comprises rail, rail pads, sleepers and ballast materials. For each subsystem, matrices of mass, stiffness and damping were formed and then matrices of total vehicle-track system considering their interaction were solved. Using FRA spectral density functions for rail irregularities, response of track with different qualities to train dynamic forces obtained. Rail random irregularities, rail corrugation and rail joint defects as three common rail defects have been considered in this paper. For each defects the influence of different track and train parameters on impact factor has been studied. The results of study indicate substantial effect of the depth and frequency of the rail flaws on impact factors. This paper has also considered the impact of vehicle speed on dynamic forces and found the critical speed for each case

Dynamic responses of railway sleepers to coupling vertical and lateral forces

It is unquestionable that railway infrastructure is naturally a complex system. Its behaviours, geometry and alignment, wheel-rail forces and operational parameters such as tractive efforts are often found to be nonlinear and asymmetrical. Not only does the complex train-track interaction generate vertical impact loading, but the curving behavior of the train body also induce dynamic lateral force acting on the rail. This paper presents a numerical simulation of a standard-gauge concrete sleepers, taking into account the tensionless nature of ballast support. The finite element model was calibrated using static and dynamic responses using experimental data. Previous extensive studies revealed that the two-dimensional Timoshenko beam model is the most suitable option for modeling concrete sleepers under vertical and lateral loads. In this investigation, the finite element model of Timoshenko-like concrete sleeper has been developed and calibrated against the numerical and experimental modal parameters. The influences coupling loads on the dynamic behaviours of concrete sleepers are investigated. In addition, it is the first to demonstrate the effects of material damping on the dynamic spectra of railway sleepers. The dynamic properties of sleepers are critical to dynamic serviceability of both track systems and sleepers themselves. The insight from this study will improve the material design criteria in order to improve train-turnout interaction and ride comfor

Numerical Estimation of Stresses in Railway Axles Using a Train-Track Interaction Model

The fatigue design of railway axles requires that the stresses arising in the axle in real service are accurately quantified. This paper describes a method to compute the dynamic stresses arising in railway axles as the effect of train track interaction, based on the numerical simulation of the dynamic interaction between a flexible wheelset and a flexible track. The wheelset is modelled as a flexible rotating body using an Eulerian approach, whereas track is regarded as an infinite periodic system with the rail modelled as a Timoshenko beam resting on discrete elastic supports, considering the inertia associated with the sleepers. The paper presents an application of the proposed procedure to the calculation of the dynamic stresses caused in the axle by different types of geometric imperfection occurring on the wheel and rail surfaces, considering the cases of a single harmonic rail corrugation, random rail roughness and a wheelflat.The authors gratefully acknowledge the support for this work provided by the Project TRA2010-15669 (Ministerio de Ciencia e Innovacion) and TRA2007-67167 (Ministerio de Educacion y Ciencia-FEDER).Martínez Casas, J.; Mazzola, L.; Baeza González, LM.; Bruni, S. (2013). Numerical Estimation of Stresses in Railway Axles Using a Train-Track Interaction Model. International Journal of Fatigue. 47:18-30. https://doi.org/10.1016/j.ijfatigue.2012.07.006S18304

Dynamic effect of high speed railway traffic loads on the ballast track settlement

The traditional ballast track structures are still being used in high speed railways lines with success, however technical problems or performance features have led to non-ballast track solution in some cases. A considerable maintenance work is needed for ballasted tracks due to the track deterioration. Therefore it is very important to understand the mechanism of track deterioration and to predict the track settlement or track irregularity growth rate in order to reduce track maintenance costs and enable new track structures to be designed. The objective of this work is to develop the most adequate and efficient models for calculation of dynamic traffic load effects on railways track infrastructure, and then evaluate the dynamic effect on the ballast track settlement, using a ballast track settlement prediction model, which consists of the vehicle/track dynamic model previously selected and a track settlement law. The calculations are based on dynamic finite element models with direct time integration, contact between wheel and rail and interaction with railway cars. A initial irregularity profile is used in the prediction model. The track settlement law is considered to be a function of number of loading cycles and the magnitude of the loading, which represents the long-term behavior of ballast settlement. The results obtained include the track irregularity growth and the contact force in the final interaction of numerical simulatio

Rail Track Maintenance Planning: An Assessment Model

In Australia, railway track maintenance costs comprise between 25-35 percent of total freight train operating costs. Track maintenance planning models have been shown to reduce maintenance costs by 5 to 10 percent though improved planning. This paper describes a model which has been developed to deal with the track maintenance planning function at the medium to long-term levels. This model simulates the impacts of degrading railway track conditions and related maintenance work, in contrast to tradition models that mainly use expert systems. The model simulates the degrading track condition using an existing track degradation model. Track condition data from that model is used to determine if safety related speed restrictions are needed and what immediate maintenance work may be required for safe train operations. The model outputs the net present value of the benefits of undertaking a given maintenance strategy, when compared with a base-case scenario. The model approach has advantages over current models in investigating what if scenarios. The track engineer can assess the possible benefits in reduced operating costs from upgrading track infrastructure or from the use of improved maintenance equipment. After describing the model inputs and the assumptions used, the paper deals with the simulation of track maintenance and of train operating costs over time. The results of applying the model to a test track section using a number of different maintenance strategies are also given

Modelling rail track deterioration and maintenance: current practices and future needs

As commercialisation and privatisation of railway systems reach the political agendas in a number of countries, including Australia, the separation of infrastructure from operating business dictates that track costs need to be shared on an equitable basis. There is also a world-wide trend towards increased pressures on rail track infrastructure through increases in axle loads and train speeds. Such productivity and customer service driven pressures inevitably lead to reductions in the life of track components and increases in track maintenance costs. This paper provides a state-of-the-art review of track degradation modeling, as well as an overview of track maintenance decision support systems currently in use in North America and Europe. The essential elements of a maintenance optimisation model currently under development are also highlighted

Analysis of a typical railway turnout sleeper system using grillage beam analogy

A simplified grillage beam analogy was performed to investigate the behaviour of railway turnout sleeper system with a low value of elastic modulus on different support moduli. This study aimed at determining an optimum modulus of elasticity for an emerging technology for railway turnout application - fibre composites sleeper. The finite element simulation suggests that the changes in modulus of elasticity of sleeper, Esleeper and the sleeper support modulus, Us have a significant influence on the behaviour of turnout sleepers. The increase in Us from 10 to 40 MPa resulted in a 15% reduction in the bending moment while the increase in Esleeper from 1 GPa to 10 GPa has resulted in almost 75% increase in the bending moment. The shear forces in turnout sleepers is not sensitive to both the changes of the Esleeper and Us while the sleeper with low Esleeper tend to undergo greater settlement into the ballast. An Esleeper of 4 GPa was found optimal for an alternative fibre composite turnout sleeper provided that the Us is at least 20 MPa from the consideration of sleeper ballast pressure and maximum vertical deflection. It was established that the turnout sleeper has a maximum bending moment of 19 kN-m and a shear force of 158 kN under service conditions

Measurement methods and analysis tools for rail irregularities. A case study for urban tram track

Rail irregularities, in particular for urban railway infrastructures, are one of the main causes for the generation of noise and vibrations. In addition, repetitive loading may also lead to decay of the structural elements of the rolling stock. This further causes an increase in maintenance costs and reduction of service life. Monitoring these defects on a periodic basis enables the network rail managers to apply proactive measures to limit further damage. This paper discusses the measurement methods for rail corrugation with particular regard to the analysis tools for evaluating the thresholds of acceptability in relation to the tramway Italian transport system. Furthermore, a method of analysis has been proposed: an application of the methodology used for treating road profiles has been also utilized for the data processing of rail profilometric data

Dynanics of a vehicle-track coupling system at a rail joint

The dynamic behaviour at a rail joint is examined using a two-dimensional vehicle–track coupling model. The track system is described as a finite-length beam resting on a double-layer discrete viscous-elastic foundation. The vehicle is represented by a half car body and a single bogie. The influence of the number of layers considered, the number of elements between two sleepers, and the beam model is investigated. Parametric studies, both of the coupling model and the analytic formulae, are carried out in order to understand the influence of the main track and vehicle parameters on the P1 and P2 peak forces. Finally, the results in terms of P2 force from the proposed model are compared, not only with measured values but also with other simulated and analytical solutions. An excellent agreement between these values is foun

Analysis of the influence of cracked sleepers under static loading on ballasted railway tracks

The principal causes of cracking in prestressed concrete sleepers are the dynamic loads induced by track irregularities and imperfections in the wheel-rail contact and the in-phase and out-of-phase track resonances. The most affected points are the mid-span and rail-seat sections of the sleepers. Central and rail-seat crack detection require visual inspections, as legislation establishes, and involve sleepers' renewal even though European Normative considers that thicknesses up to 0.5mm do not imply an inadequate behaviour of the sleepers. For a better understanding of the phenomenon, the finite element method constitutes a useful tool to assess the effects of cracking from the point of view of structural behaviour in railway track structures. This paper intends to study how the cracks at central o rail-seat section in prestressed concrete sleepers influence the track behaviour under static loading. The track model considers three different sleeper models: uncracked, cracked at central section, adn cracked at rail-seat section. These models were calibrated an validated using the frequencies of vibration of the first three bending modes obtained from an experimental modal analysis. The results show the insignificant influence of the central cracks and the notable effects of the rail-seat cracks regarding deflections and stressesMontalban Domingo, ML.; Zamorano Martin, C.; Palenzuela Aviles, C.; Real Herráiz, JI. (2014). Analysis of the influence of cracked sleepers under static loading on ballasted railway tracks. The Scientific World Journal. 2014. doi:10.1155/2014/363547S2014Remennikov, A. M., & Kaewunruen, S. (2008). A review of loading conditions for railway track structures due to train and track vertical interaction. Structural Control and Health Monitoring, 15(2), 207-234. doi:10.1002/stc.227Barke, D. W., & Chiu, W. K. (2005). A Review of the Effects of Out-Of-Round Wheels on Track and Vehicle Components. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 219(3), 151-175. doi:10.1243/095440905x8853KAEWUNRUEN, S., & REMENNIKOV, A. M. (2007). EFFECT OF IMPROPER BALLAST PACKING/TAMPING ON DYNAMIC BEHAVIORS OF ON-TRACK RAILWAY CONCRETE SLEEPER. International Journal of Structural Stability and Dynamics, 07(01), 167-177. doi:10.1142/s0219455407002174Gustavson, R., & Gylltoft, K. (2002). Infuence of cracked sleepers on the global track response: Coupling of a linear track model and nonlinear finite element analyses. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 216(1), 41-51. doi:10.1243/0954409021531674Profillidis, V. A. (1986). Applications of finite element analysis in the rational design of track bed structures. Computers & Structures, 22(3), 439-443. doi:10.1016/0045-7949(86)90049-0Shahu, J. T., Kameswara Rao, N., & Yudhbir. (1999). Parametric study of resilient response of tracks with a sub-ballast layer. Canadian Geotechnical Journal, 36(6), 1137-1150. doi:10.1139/t99-054Gallego Giner, I., & López Pita, A. (2009). Numerical simulation of embankment—structure transition design. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 223(4), 331-343. doi:10.1243/09544097jrrt234Schanack, F., Ramos, Ó. R., Reyes, J. P., & Pantaleón, M. J. (2014). Relative Displacement Method for Track-Structure Interaction. The Scientific World Journal, 2014, 1-7. doi:10.1155/2014/397515Fu, Q., & Zheng, C. (2014). Three-Dimensional Dynamic Analyses of Track-Embankment-Ground System Subjected to High Speed Train Loads. The Scientific World Journal, 2014, 1-19. doi:10.1155/2014/924592Zhang, X., Zhu, Z., & Liu, H. (2014). Fracture Property of Y-Shaped Cracks of Brittle Materials under Compression. The Scientific World Journal, 2014, 1-7. doi:10.1155/2014/192978Molyneux-Berry, P., Davis, C., & Bevan, A. (2014). The Influence of Wheel/Rail Contact Conditions on the Microstructure and Hardness of Railway Wheels. The Scientific World Journal, 2014, 1-16. doi:10.1155/2014/209752Yan, S., Wu, J., Sun, W., Ma, H., & Yan, H. (2013). Development and Application of Structural Health Monitoring System Based on Piezoelectric Sensors. International Journal of Distributed Sensor Networks, 9(11), 270927. doi:10.1155/2013/270927Montalbán, L., Zamorano, C., Palenzuela, C., & Real, J. I. (2014). Finite element modelling of cracked railway pre-stressed concrete sleepers. European Journal of Environmental and Civil Engineering, 19(1), 81-93. doi:10.1080/19648189.2014.935486Drucker, D. C., & Prager, W. (1952). Soil mechanics and plastic analysis or limit design. Quarterly of Applied Mathematics, 10(2), 157-165. doi:10.1090/qam/48291Li, D., & Selig, E. T. (1998). Method for Railroad Track Foundation Design. I: Development. Journal of Geotechnical and Geoenvironmental Engineering, 124(4), 316-322. doi:10.1061/(asce)1090-0241(1998)124:4(316