Ballasted Track Structure Research Articles

Diagnostics of Track Quality of Ballastless Track and Transition Areas in Vicinity of Portals of Tunnel Turecky vrch

Abstract The paper deals with the partial results of diagnostics of experimental sections of ballastless track Rheda 2000® and transition areas between ballastless and ballasted track structure around portals of tunnel Turecky vrch after six measurement cycles. The paper presents differences between each operational measurement and the measurement before putting sections into operation, which indicates a development of track geometry quality.

Simple plastic deformation analysis of ballasted track under repeated moving-wheel loads by cumulative damage model

This study examines a simplified and practical prediction method for the cumulative residual settlement of ballasted track under repeated train passages, and the applicability and usefulness of the proposed method are discussed by comparing the experimental results of cyclic loading tests of model ballasted track structures with the analytical results. As the results, this study proposed a new analytical procedure with iterative calculation by linear elastic Finite Element (FE) analysis, which can evaluate the effects of continuous rotation of principal stress axis due to moving-wheel loads by taking into consideration the cumulative strain characteristics of ballast obtained from laboratory element tests such as multi-ring shear tests adopting the moving-wheel loading method in terms of the practical use. In addition, it was revealed that when laboratory element tests with high accuracy was conducted under experimental conditions similar to the actual phenomena in order to grasp the cumulative strain characteristics of ballast and then plastic deformation analysis was performed based on the findings above, the proposed analytical procedure could roughly estimate the cyclic plastic deformation of railroad ballast under repeated moving-wheel loads even with a simple linear elastic FE analysis. These findings confirm sufficient applicability of the proposed analytical procedure to the estimation of the cumulative residual settlement observed at ballasted track structures subjected to repeated train passages.

Vertical vibrations of composite bridge/track structure/high-speed train systems. Part 3: Deterministic and random vibrations of exemplary system

Abstract Based on the one-dimensional quasi-exact physical and mathematical modelling of a composite (steel-concrete) bridge/track structure/high-speed train system (BTT), developed in Part 2, advanced computer algorithms for the BTT numerical modelling and simulation as well as a computer programme to simulate vertical vibrations of BTT systems are developed. The exemplary bridge under numerical quasi-static and dynamic analysis, designed according to Polish standards, has a 15.00 m span length and belongs to the SCB series-of-types developed in Part 1. The bridge is loaded by a German ICE-3 high-speed train moving at the resonant and maximum operating speeds. A continuously welded ballasted track structure adapted to high operating velocities is applied. The output quantities include: time-histories of the vertical deflection of the main beams at the midspan, time-histories of the longitudinal normal stress in the bottom fibres of the main beams at the midspan, time-histories of the vertical acceleration of the bridge deck at the midspan, time-histories of the vertical accelerations of the suspension pivots in car-bodies, time-histories of the dynamic pressures of the wheel sets of moving rail-vehicles. The design quantities, understood as the extreme values of the output quantities, are used to verify the design conditions. The basic random factor, i.e. vertical track irregularities of the track, is taken into consideration. Basic statistics of the design quantities treated as random variables are calculated and taken into account in the design conditions.

Vertical vibrations of composite bridge/track structure/high-speed train systems. Part 1: Series-of-types of steel-concrete bridges

Abstract A new series-of-types of single-span simply-supported railway composite (steel-concrete) bridges, with a symmetric platform, has been designed according to the Polish bridge standards. The designed bridges/viaducts are located on the main railways of the classification coefficient k = +2. A ballasted track structure adapted to high operating speeds has also been designed. The ultimate limit states and the limit states corresponding to the bridges undertaken are collected and discussed. The bridges have been designed in accordance with contemporary art engineering, with geometric and material optimization, avoiding overdesign. A new methodology of numerical modelling and simulation of dynamic processes in composite bridge/ballasted track structure/high speed train systems, developed in Part 2 and Part 3, has been applied and implemented in a problem-oriented computer programme. A new approach to predicting forced resonances in those systems is formulated and tested numerically. It has been proved that in the case of typical structural solutions of bridges and ballasted track structures, it is necessary to introduce certain limitations for operating speeds of trains

Vibrations of Bridge / Track Structure / High-speed Train System with Vertical Irregularities of the Railway Track

The study presents the vibration theory and random dynamic analysis of the series-of-types (designed by the author) of composite (steel-concrete) bridges loaded by a German ICE-3 high-speed train. The vibration theory includes: a continuously welded ballasted track structure, viscoelastic suspensions of rail-vehicles with two two-axle bogies each, non-linear Hertz contact stiffness and one-sided contact between the wheel sets and the rails, the viscoelastic and inertia features of the bridge, the viscoelastic track structure on and beyond the bridge, approach slabs. The basic random factor, i.e. vertical track irregularities of the track, is taken into consideration.

Parametric Study on Geogrid-Reinforced Track Substructure

The purpose of this paper was to evaluate the effectiveness of geogrid for conventional ballasted track and asphalt concrete underlayment track using PLAXIS finite element program. Geogrid element was modeled at various locations that include subballast/subgrade, subballast/ballast interfaces, middle of the ballast, and one-third depth of the ballast. The results revealed that the effectiveness of geogrid reinforcement appeared to be larger for ballasted track structure compared to asphalt concrete underlayment track. Particularly, in case of installing geogrid at one-third depth of ballast layer in a conventional ballasted track, the most effectiveness of geogrid reinforcement was achieved. The influence of geogrid axial stiffness on track substructure response was not clear to conclude. Further validations using a discrete element method along with experimental investigation are considered as a future study. The effect of asphalt concrete layer modulus was evaluated. The results exhibited that higher layer modulus seems to be effective in controlling displacement and strain of track substructure. However it also yields slightly higher stresses within track substructure. It infers that further validations are required to come up with optimum asphalt concrete mixture design to meet economical and functional criteria.

Effect of random track irregularities on selected composite bridge / track structure / high-speed train system vibrations

A theory of the quasi-exact physical and mathematical modelling of the composite (steel–concrete) bridge / ballasted track structure / high-speed train system (BTT) was developed, including viscoelastic suspensions of rail-vehicles on two-axle bogies, the non-linear Hertz contact stiffness and one-sided contact between the wheel sets and the rails, the viscoelastic and inertia features of the bridge, the viscoelastic track structure on and beyond the bridge, the approach slabs, and random track irregularities. Based on this theory, advanced computer algorithms for the BTT numerical modelling were written and a computer program to simulate the vertical vibrations of the BTT systems was developed. The bridge subject to the preliminary dynamic analysis and designed according to Polish standards has a 15.00 m span length. The bridge was loaded by the German ICE-3 high-speed train moving at the critical (180 and 270 km/h) and the maximum (300 km/h) operating speeds.

Analysis of buckling in dual-gauge tracks

Two types of track gauges are currently in use in the Spanish railway network: the traditional ‘iberian’ wide gauge of 1668 mm used in the conventional network and the international 1435 mm gauge used for the high-speed lines. The dual-gauge track, in which a third rail is added to the classical two-rail layout, has recently been proposed for the design of new lines. This solution implies a substantial modification of the classical ballasted track structure and thus requires an analysis of mechanical phenomena occurring on the rail-sleeper grid of the track. In particular, this study focused on lateral track buckling, produced by the axial compression stresses on the rails induced by increases in temperature. Whenever the axial compression force exceeds a critical threshold, the track could become unstable as significant lateral deflections may appear thus leading to unacceptable riding safety levels. In this case, the addition of the third rail increases the steel section and therefore the axial compression, which may lead to track instability. This study assessed this phenomenon in detail by means of a three-dimensional, nonlinear, numerical finite element model, based upon the latest reports of the European Railway Research Institute. Several conclusions have been derived from this study as regards the increasing risk of instability in a dual-gauge track.