Variation of Track Response to Wheel Forces with Bogie Axle Spacing: Apparent Track Stiffness and its Influence on Dynamic Impact Forces on Railway Tracks

2021 ◽  
pp. 036119812110624
Author(s):  
Erdem Balcı ◽  
Niyazi Özgür Bezgin ◽  
Mohamed Wehbi
Keyword(s):  
Analytical Study ◽  
Mechanical Characteristics ◽  
Numerical Study ◽  
Railway Track ◽  
Dynamic Impact ◽  
Transition Zones ◽  
Railway Tracks ◽  
Impact Forces ◽  
Track Stiffness ◽  
New Perspective

Track stiffness is an important parameter that affects railway track response. Axle spacing influences the response of the track to wheel forces and has an effect on track stiffness. Track response to train wheels within a bogie or between neighboring bogies vary in relation to their mutual interference, depending on the mechanical characteristics of the layers composing the track, axle spacing and bogie spacing. This interference affects the force-deflection characteristic of the railway track under a wheel. Dynamic impact forces caused by track and wheel roughness relate to track stiffness. Therefore, everything else being the same, two trains with different bogie spacing may generate different dynamic impact forces on the railway track. As a result, the accumulated damage to a railway track over time can relate not only to cumulative tonnage but also to the axle spacing of the trains operating on the railway track. Through superposition of the estimated track deflections by the beam-on-elastic-foundation theorem and looking at it from a new perspective, this paper discovers a set of relations between the variations of track stiffness with bogie axle spacing. The paper introduces a new concept of apparent track stiffness and hypothesizes that dynamic impact forces on the railway tracks relate to axle spacing. The paper then presents a numerical study and an analytical study that analyzes wheel and track interaction along stiffness transition zones for different values of axle spacing and shows that bogie axle spacing has an effect on dynamic impact forces on railway tracks.

Advancement and Application of the Bezgin Method to Estimate Effects of Stiffness Variations along Railways on Wheel Forces

2019 ◽  
Vol 2673 (7) ◽  
pp. 248-264
Author(s):  
Niyazi Özgür Bezgin ◽  
Mohamed Wehbi
Keyword(s):  
Analytical Method ◽  
Contact Stiffness ◽  
Hertzian Contact ◽  
Dynamic Impact ◽  
Transition Zones ◽  
Railway Tracks ◽  
Impact Forces ◽  
Track Stiffness ◽  
Railway Engineering ◽  
New Equation

The need for an analytical method that one can apply manually to estimate dynamic impact forces on railway tracks that occur because of varying track stiffness or track profile initiated a study to develop an analytical method named as the Bezgin Method. The advancement of this method presented in this paper includes an extension of a set of equations developed and introduced by the first author earlier as the Bezgin Equations using the proposed method and development of a new equation. In addition to track stiffness taken into consideration in the equations introduced earlier, the Extended Bezgin Equations presented in this paper take into account bogie stiffness, wheel spring stiffness, Hertzian contact stiffness, and a factor for damping. The new equation takes into account the effect of vertical wheel acceleration as a train transitions to a stiffer structure or transitions along an ascending track profile. The paper unites and applies these equations to estimate wheel forces that develop along stiffness transition zones by considering an array of train speeds for an array of track stiffness ratios and representative values for track profile deviations along the transitions. Final section of the paper includes elaborate finite element analyses of structural track models that involve transitions of soil supported ballasted railway tracks with concrete based ballasted tracks along various transition lengths and compares their estimates for dynamic impact force factors with those estimated by the Extended Bezgin Equations. The paper concludes with a discussion of the potential uses, benefits, and the value of the Bezgin Method for railway engineering.

scholarly journals Application of the Bezgin Method to estimate dynamic impact forces and judge the conditions for ballast pulverization and slab cracking due to abrupt and rapid changes in railway track profile

2021 ◽  
Author(s):  
Erdem Balcı ◽  
Niyazi Özgür Bezgin
Keyword(s):  
Experimental Studies ◽  
Rate Of Change ◽  
Railway Track ◽  
Rolling Stock ◽  
Structural Domain ◽  
Numerical Techniques ◽  
Dynamic Impact ◽  
Accurate Analysis ◽  
Impact Forces ◽  
Track Stiffness

Dynamic impact forces occur on railway tracks due to the presence of roughness of the track and the wheel and relate to the train speed and the rate of change of roughness. Variations in track profile and track stiffness and variations in wheel circularity are the causes of roughness. Quantification of the dynamic impact forces is not an easy task due to the complexity of the mechanics of the rolling stock interaction with the railway track. A number of experimental studies have led to an understanding of the dynamic impact forces, yielding a set of conservative and case-specific empirical equations. There are also many calculation-intensive numerical techniques, relying on iterative calculations seeking to converge to a state of temporary equilibrium for the analyzed structural domain within small-time increments. These techniques provide detailed and valuable information for the stresses that develop within the many components of the railway track. However, such numerical techniques rely on expensive computational tools that require experienced users to apply and interpret their results. The sheer amount of representative structural and material data input required to define the analyzed structural domain of the railway track properly is also an important task to accomplish in order to conduct a meaningful analysis. The second author developed a simple analytical method that can provide an accurate analysis for the dynamic impact forces on any railway track relying on track stiffness as the only mechanical railway track parameter. This paper introduces an ongoing study led by the second author and provides an insight into how a designer or a track maintainer can apply the Bezgin Method to estimate dynamic impact forces that may occur in rail-ends and within turnouts. This paper will also discuss how one can judge the conditions for ballast pulverization or slab cracking should these conditions exist.

Proposal and Application of a New Technique to Forecast Railway Track Damage Because of Track Profile Variations

2019 ◽  
Vol 2673 (4) ◽  
pp. 568-582
Author(s):  
Mohamed Wehbi ◽  
Niyazi Özgür Bezgin
Keyword(s):  
Decomposition Method ◽  
Wavelet Decomposition ◽  
Impact Force ◽  
Railway Track ◽  
Dynamic Impact ◽  
Railway Tracks ◽  
Impact Forces ◽  
Profile Variation ◽  
Damage Data ◽  
A New Technique

This paper presents a new technique to estimate dynamic impact forces on railway tracks that develop because of variations in track profile. The approach presented uses a wavelet decomposition method to systematically define the irregular profile variation of a rough track length in relation to regular wavelet functions. These functions provide the regular profile variation parameters to estimate the dynamic impact forces using a new method proposed by Bezgin. This paper begins with an introduction of the proposed Bezgin Method and two equations developed by this method to estimate dynamic impact force factors that develop along descending track profiles, followed by the presentation of the wavelet decomposition method to represent the irregular variations in rough track profiles by wavelet functions. The paper then presents three case studies that involve track profile and stiffness measurements and track damage data collection along three railway tracks in the United Kingdom and continues with the applications of the wavelet decomposition method to the measured variations in the track profiles. The equations developed by the Bezgin Method then make use of the processed profile data to estimate the dynamic impact force factors along the railway tracks. The paper ends by correlating the estimated dynamic impact force factors to the damage data collected along the tracks and shows that there is a relation between the observed track damage and the estimated dynamic impact force factors. The proposed technique has, therefore, the potential applications to assess railway track conditions and forecast railway track damage.

scholarly journals Investigating the Effect of Some Train and Track Parameters on Contact-impact Forces in the Vicinity of a Rail Breakage

2019 ◽  
Author(s):  
Mosab Reza Tajalli ◽  
Jabbar Ali Zakeri
Keyword(s):  
Interaction Model ◽  
Element Model ◽  
Contact Forces ◽  
Railway Track ◽  
Dynamic Impact ◽  
Impact Forces ◽  
Risk Increase ◽  
Length Increase ◽  
Train Speed ◽  
Contact Impact

Broken rails or welds are the main causes of derailment in railway networks. Therefore, a wheel-rail interaction model, which precisely estimates contact-impact forces in the presence of broken rails, can have a significant effect on derailment risk reduction. This paper attempts to present contact-impact forces in the vicinity of broken rails by employing a detailed 3D finite element model. The model is verified using a field test carried out on a ballasted railway track. Effects of train speed, gap length, axle load and railpad and ballast characteristics are studied on rail-wheel contact forces as well as on railpad and ballast forces. Results suggest that increasing the train speed from 60 km/h to 110 km/h would increase dynamic impact force from 2.46 to 4.11. It is also observed that increasing axle load results in an increase in the wheel-rail impact forces and in railpad and ballast forces, while leading to a reduced dynamic impact factor. Furthermore, investigating the effect of the track parameters demonstrates that ballast stiffness is the most important characteristic of the track, which has a reverse effect on dynamic impact forces. Moreover, unloading length increase and consequently derailment risk increase is highly sensitive to increasing train speed.

scholarly journals Dynamic train-track interactions over railway track stiffness transition zones using baseplate fastening systems

2020 ◽  
Vol 118 ◽  
pp. 104866
Author(s):  
Chayut Ngamkhanong ◽  
Quek Yan Ming ◽  
Ting Li ◽  
Sakdirat Kaewunruen
Keyword(s):  
Railway Track ◽  
Train Track ◽  
Transition Zones ◽  
Track Stiffness

Reduction of Dynamic Wheel/Rail Impact Forces at Grade Crossings Using Stiffness Transitions

2001 ◽  
Author(s):  
Allan M. Zarembski ◽  
Joseph W. Palese ◽  
Leonid Katz
Keyword(s):  
New Jersey ◽  
Field Tests ◽  
Atlantic City ◽  
Dynamic Impact ◽  
Theoretical Formulation ◽  
Analytical Technique ◽  
Transition Zones ◽  
Impact Forces ◽  
Grade Crossing ◽  
Grade Crossings

Abstract This paper presents the results of combined analytical and field study of the use of vertical stiffness transition zones to reduce dynamic wheel/rail impact forces at the interface between conventional track and high/rail grade crossings. These interfaces are traditionally sites of severe dynamic impact forces and corresponding rapid degradation of the geometry of the track. A recent FRA sponsored research study developed a new analytical technique to define the number of and magnitude of the stiffness transition zones needed to reduce the dynamic impact forces. This technique was used to design a series of transitions for a concrete grade crossing, which were installed on New Jersey Transit’s Atlantic City Line in the vicinity of ATCO New Jersey in 1998. Field tests performed on the grade crossing after installation showed a significant reduction in measured dynamic vertical accelerations across the grade crossing as compared to other crossings on the same line. Recent follow up evaluation of this grade crossing showed that it is performing significantly better than similar adjacent grade crossings on the same line and that there has been a marked reduction in degradation of the track/grade crossing and associated maintenance. This paper will present the results of the theoretical formulation, analytical study, and the field tests.

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