New Advances in Design of Railway Track System

Sadeghi, Javad

doi:10.5772/35903

Cited by 8 publications

(13 citation statements)

References 5 publications

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“…4,15 Additionally, it has been noted that many of the prediction tools also overestimate the loads in the rail transit loading environment, leaving room for further refinement given sufficiently large and accurate data sets. 10,16 The prediction of impact loads, and its incorporation into design, is comparatively simpler. According to AREMA, 17 impact loads are incorporated into recommended design practices for concrete crossties as a 200% increase over the static load, or three times static load.…”

Section: Types Of Loadsmentioning

confidence: 99%

Quantification of rail transit wheel loads and development of improved dynamic and impact loading factors for design

Edwards

Cook

Dersch

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part F:

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An increase in the number of rail transit track construction and rehabilitation projects in North America has generated increased interest in optimizing the design of the track infrastructure and its components. Many rail transit track component design guidelines use historical wheel loads and loading factors that were derived from freight railroad design practices. These design factors may not be representative of the loading experienced on the rail transit networks today, leading to over-designed, sub-optimal infrastructure components. Therefore, researchers at the University of Illinois at Urbana-Champaign are conducting research to lay the groundwork for improved understanding of the loading environment entering the track structure using wheel loads data obtained from recently deployed field instrumentation and existing wheel impact load detectors. This paper evaluates the existing design impact factors and assesses their effectiveness when applied to the rail transit sector, using data from three representative rail transit agencies in the United States. New dynamic loading factors are also proposed to represent the rail transit loading environment more accurately. A quantitative approach to addressing design factors may provide economies in future designs and facilitate the use of probability of exceedance and other metrics that relate to factors of safety.

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Section: Types Of Loadsmentioning

confidence: 99%

Quantification of rail transit wheel loads and development of improved dynamic and impact loading factors for design

Edwards

Cook

Dersch

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part F:

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“…This lack of further research on the topic corroborates the idea that railway track design relies considerably on an empirical approach -as discussed by Markine et al, 39 Markine et al 40 and Sadeghi. 42…”

Section: Metaheuristic and Other Optimization Methods In Railway Transportationmentioning

confidence: 99%

Optimization of the behaviour of high-speed railway tracks using a genetic algorithm approach

Rodrigues

Dimitrovová

2014

Proceedings of the Institution of Mechanical Engineers, Part F:

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This paper deals with a multi-objective optimization of geometrical and mechanical properties of a high-speed railway track when subjected to a moving load representative of a train axle. The model of the track employs several simplifications; it was implemented in two dimensions on the explicit dynamics module LS-DYNA for the finite element commercial software ANSYS. The design space is formed by the ballast height and by parameters representing the dynamic properties of the rail-pads. The objective function covers minimization of the maximum ascending and descending displacement and velocity in the main structural elements, namely the rail, the sleepers and the ballast. A genetic algorithm implementation is used to optimize these functions, which proved to be effective in finding quasi-optimal solutions with a low search effort. The tools presented can give insight into how the behaviour of the railway track is influenced by various design parameters.

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“…The assumption of a uniform load distribution under the sleeper is adequate for a stiff sleeper, such as a concrete sleeper. For a more flexible sleeper, such as a timber or a polymer sleeper, also the sleeper itself should be considered as a beam-on-elastic-foundation, otherwise rail seat loads will be overestimated and rail deflections will be underestimated (Rahrovani, 2016; Sadeghi, n.d. ; Sadeghi and Youldashkhan, 2005; Winkler, 1875).…”

Section: Current Calculation Modelsmentioning

confidence: 99%

“…When performing maintenance in track, by tamping the ballast, only the area around the rail seat is tamped, creating a more local support, as can be seen in Figure 2(b) (Sadeghi, n.d.). The situation in Figure 2(a) can be interpreted as a specific case of the situation in Figure 2(b), that is, the situation where L 2 = 0 and L 3 = 1 / 2 L .…”

Section: Current Calculation Modelsmentioning

confidence: 99%

“…At the rail seat, where the ballast stresses are the highest, settlement will be the highest. This results in movement and/or compaction of the ballast with levelling of the ballast stresses as a result, until the support condition of Figure 2, load case C is reached (Sadeghi, n.d., 2010; Schwedler, 1889). In this situation, the loads on the ballast are uniform over the sleeper length and thus further ballast settlement will occur evenly.…”

Section: Worn Trackmentioning

confidence: 99%

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A simplified method for calculating load distribution and rail deflections in track, incorporating the influence of sleeper stiffness

Belkom

2020

Advances in Structural Engineering

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When performing railway track stiffness analyses, in current standards sleepers are often regarded as a rigid member. For flexible sleeper materials like timber or polymers, this may lead to underestimating rail deflections up to a factor two and overestimating rail seat loads up to 20%. Calculations incorporating sleeper bending can currently be performed analytically by a two-layer beam-on-elastic-foundation calculation, or by finite element analyses, but a simple approach does not yet exist. This article introduces a simple calculation method to establish rail deflections, track stiffness and rail seat loads, incorporating the effects of both bending and shear stiffness of the sleeper, applicable to new or tamped track. A sleeper flexibility factor fS is introduced as a deformation multiplication factor compared with a rigid sleeper. Validation against current calculation models shows a deformation accuracy within 6% and a load accuracy within 2%. When a track is not maintained, a gap will develop under the sleeper at the rail seat. The size of this gap correlates to the stiffness of the sleeper. Eventually a uniform load distribution can develop under the sleeper. A calculation method is introduced to estimate the gap and the track behaviour at uniform load distribution. When for flexible sleepers the track deflection due to the gap can develop outside of the desired range, timely track maintenance or monitoring is advised.

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New Advances in Design of Railway Track System

Cited by 8 publications

References 5 publications

Quantification of rail transit wheel loads and development of improved dynamic and impact loading factors for design

Quantification of rail transit wheel loads and development of improved dynamic and impact loading factors for design

Optimization of the behaviour of high-speed railway tracks using a genetic algorithm approach

A simplified method for calculating load distribution and rail deflections in track, incorporating the influence of sleeper stiffness

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