Jabbar Ali Zakeri

• Professor (full)
• Head of Department at Iran University of Science and Technology

Increasing the train speed in railway networks is the most important factors in improving the fields of attracting more passengers and cargo than other transportation modes. The construction of new railway structures with the aim of increasing the speed of trains requires a lot of money. Therefore, the purpose of this study is to investigate the po...

Since the establishment of the railway system, railway engineers worldwide have been striving to enhance the speed and axle load of trains. Numerous efforts have been made to develop various railway networks. The acceptance of this mode of transportation can be enhanced by increasing the axle load and running speed of trains. This study aims to inv...

One of the inevitable places where the railway track stiffness suddenly changes is the junction points of the slab and ballasted tracks. In these junction areas, differences in the vertical stiffness of the track cause an increase in wheel–rail contact forces that lead to some crucial damages in railway tracks such as rail defects, hanging sleepers...

Due to increasing train speed and passage tonnage, the repair and maintenance of ballasted railway tracks is essential. As a result of cyclic train loads on ballasted tracks, the ballast layer can deteriorate. When the ballast bed deteriorates, it can change the track geometry, which leads to uncomfortable ride and an increase in wheel-rail interac...

Railway bridges are built to allow trains to cross over highways, valleys, or other transportation infrastructure. In recent years, the number of railway bridges subjected to over-height collision forces has increased. These collisions damage the bridge and affect the safety of the running train. In this investigation, first, a 3D GT26 train-track-...

Nowadays, attention to railways has been increased as one of the important transportation methods. Various factors can cause longitudinal forces on the railway tracks, so the most important factors are the temperature changes due to the rail contraction and expansion (thermal forces), train braking system forces and acceleration, etc. Increasing lo...

Abrupt stiffness variations along the railway track may increase the geometrical and mechanical defects of railway lines. The conjunction points of a railway track with concrete and ballast pavements, which are called slab-ballasted track transitions, are one of the main areas where vertical track stiffness changes sharply. Therefore, the potential...

The railway network design problem is one of the critical issues in the transportation sector due to its significance and variety of necessary applications. The major issue of this field relates to the decision of whether to increase the railways’ capacity or construct a new route to meet demand. Although the budget is a great concern of the manage...

Full service without defects of railway bridges is more important than highway bridges because failure at a part of the bridge results in the blockage of the entire track and the stopping of the trains. In recent years, the problem of an over-height vehicle collision to the bridge superstructure has occurred more frequently. These collisions damage...

Ballast is a porous layer that reduces the effective contact surface between sleeper and ballast. Also, the sleeper does not have a smooth bottom surface, which causes a reduction of the contact surface between the sleeper and ballast particles. At field experiments, by installing sensitive papers under the sleepers of a track, the cyclic load was...

Lubricants are usually utilized to decrease wear, reduce friction, and release heat. Although the lubrication approximation originated from thin-film studies, it has limitations because of continuum mechanics assumptions. To overcome these limitations, for the first time, this article employs a hierarchical multiscale approach to study the friction...

A ballasted railway track's longitudinal stiffness and resistance with wooden sleepers were experimentally and numerically investigated. The longitudinal resistance was measured by measuring the force and displacement in the rail's axial direction by increasing the number of sleepers from one to five. The track longitudinal stiffness (TLS) and resi...

The traditional ballasted tracks have been used widely in railway transportation infrastructure. Construction of ballasted tracks on the clayey soft subgrade causes high settlement and low bearing capacity. Significant maintenance cost and time-consuming operation have been encountered due to presence of clay. Different methods of soil stabilizatio...

Background Road traffic crashes and associated injuries and mortalities are one of the big public health challenges, especially in low/middle-income countries. Road safety lead agency (RSLA) is a vital factor in the sustainable prevention and promotes road safety. In the recent decades, various policy interventions have been conducted for road safe...

A study about the running safety of trains moving over bridges subjected to hydrodynamic loads under one-direction and two bidirectional high-speed train passing is presented. Dynamic performance of the developed 3D train–bridge–wave system (TBW model) subjected to different hydrodynamic loads and applying Association of American Railroads track ir...

Track longitudinal resistance is defined as the resistance generated by sleeper-ballast and rail-sleeper interactions against the imposing forces, which cause longitudinal displacement. This component is one of the important indicators of the continuously welded rail (CWR) track's stability and lateral resistance against buckling. In this paper, th...

Sand dune accumulation in the railways passing through desert areas leads to ballast softening and settlement, which is one of the major challenges in the ballast maintenance operation. In this regard, ballast infilling with polyurethane could be mentioned as a novel solution that has been less attentional in previous studies. In this matter, in pr...

This paper considers the impact of foundation geometry on the vibrations transferred to a building in the vicinity of a railway line from the aspect of choosing an appropriate foundation type. For this purpose, a 1-g scale physical model is developed that includes the main parts containing dry sandy soil, a rigid soil container, and a five-story st...

With the increasing speed of trains and the axle load of railways, the need to provide lateral stability of railways becomes more important. Small-radius curves on conventional tracks and temperature fluctuations pose a significant threat to the lateral stability of railway tracks as they increase lateral and longitudinal forces, leading to track b...

Determining the strategy and planning for maintenance operations on railway tracks is important given the increasing demand from both freight and passengers. An important prerequisite of maintenance planning is the ability to predict the overall and geometric conditions of the railway in the near future. It is, therefore, necessary to develop a deg...

The longitudinal resistance of ballasted tracks is due to the longitudinal interaction of rail-fastener and ballast-sleeper. Longitudinal resistance is under the effect of various factors as well as the applied vertical load of the running train over the track structure. In this paper, the effect of vertical load on the longitudinal resistance of t...

Track thermal buckling is one of the primary safety issues of continuously welded rail tracks. It has been shown that transition zones of open deck steel bridges are more prone to track buckling, as the thermal loads from the bridge and lower track lateral resistance in this region can destabilize the track in the lateral plane. The aim of this pap...

Abstract: This paper proposes a multiobjective optimization approach for a preventive maintenance scheduling problem. To model this problem, an optimization model was developed by considering two objective functions: minimizing maintenance cost associated with the preventive tamping cost, machine preparation cost, and possession cost during time sc...

Abstract This paper proposes a multi objective optimization approach for a preventive maintenance scheduling problem. To model this problem, an optimization model was developed by considering two objective functions: minimizing maintenance cost associated with the preventive tamping cost, machine preparation cost, and possession cost during time s...

Lateral displacement of sleepers and uneven settlement in ballast layer induced by lateral loading of trains running through the curves, the continuous rail's thermal force, and the discontinuity of the ballast particles. One of the most critical challenges in railway track mechanics is lateral displacement of the sleeper affected by dimensions and...

Track thermal buckling is one of the primary safety issues of continuously welded rail tracks. The lateral track resistance is the main resisting force against track buckling, which is mainly provided through the interaction of sleepers in the ballast material. In this sense, researchers have focused on determining the lateral resistance of various...

In order to reduce the buckling problems related to the railway ballasted tracks, measurement should be applied to improve the lateral resistance of tracks. There are different procedures to increase the lateral resistance of railway tracks. These methods are implemented using various materials by changing the size, geometry, and dimensions of trac...

Nowadays, with various advancements in the railway industry and increasing speed of trains, the design of railway tracks and vehicles has become vitally important. One of the frequent problems of ballasted tracks is the existence of unsupported sleepers. This phenomenon occurs due to the lack of ballast underneath the sleepers. Here, a model is pre...

Some issues concerning railway routes are related to avoiding uneven deformations, rail roughness, and increased dynamic loads. Lack of transition zones at the entrance and exit of bridges intensifies the above-mentioned failures due to sudden changes in track stiffness. The main objective of this article is to investigate the effects of approach s...

In this study, the dynamic behavior of the 3D train-bridge system subjected to different hydrodynamic loads (TBW model) is established. By taking a continuous bridge (32 + 48 + 32) m with box girders as a case study, the dynamic responses of the bridge which is under train passing and subjected to several sea hydrodynamic loads are analyzed. The su...

In this paper, a new test method and a measurement technique were proposed to evaluate the track longitudinal resistance (TLR). The three-stage track longitudinal behavior was assessed. The track longitudinal stiffness (TLS) and track longitudinal resistance force (TLRF) were defined based on the analyses of force-displacement curves in each test....

Track lateral resistance ensures the track stability under operation and during its service life in lateral and longitudinal directions. Numerous methods and techniques have been considered to enhance track lateral resistance. Since sleeper, as one of the railway track superstructure components, has a significant contribution in providing the later...

Controlling the ground-borne vibrations affecting structures by changing the geometry and weight of foundation as an inexpensive and efficient method has rarely been considered by researchers. In this article, the effect of foundation geometry and weight built on different soil types on the induced vibration level in a building at the proximity of...

A floating ladder track is established in the present paper as a next-generation non-ballasted track system. The three-dimensional model consists of a track (mass-spring-damping system) and the underlying soil. Rectangular pulse loading with an amplitude of 60 kN is considered as the wheel loading system. A time domain coupled finite element with a...

Abstract The aim of this study has been to determine the optimal maintenance limits for one of the main railway lines in Iran in such a way that the total maintenance costs are minimized. For this purpose, a cost model has been developed by considering costs related to preventive maintenance activities, corrective maintenance activities, inspection...

This study investigates the simultaneous effects of unsupported sleepers and rail random irregularities on track displacement and wheel load reduction, by means of numerical simulations with vehicle-track coupling. Vehicles are simulated as multibody systems comprising the major vehicle masses and suspension systems with nonlinear stiffness and dam...

In order to reach a desired quality in railway tracks and to maintain this quality in an acceptable level, a systematic and regular maintenance plan must be performed. By proper management of track maintenance and codification of proper methods to evaluate the quality of railway tracks, a desired quality can be reached. For this purpose, some indic...

A proper decision-making scheme for track geometry maintenance requires a knowledge of the real condition of track geometry. Therefore, the track must be inspected by measurement cars at different time intervals. The frequency of track geometry inspection plays a crucial role in decision-making and has always been a big concern for infrastructure m...

Broken rails or welds are among the rail discontinuities that generate significant impact forces in the wheel-rail contact surface. These forces lead to contact loss and thus an increase in the derailment probability. In this paper, experimental and analytical data are employed to study the impact force as the wheel crosses over a broken rail. In t...

One of the major concerns in the development of railway systems is to choose an optimized wheel and rail profile from a wide range of material and geometries. Although various investigations are conducted to improve the vehicle and rail behavior, there is less research on the wheel–rail interaction when a heavy vehicle passes through a light rail t...

Lateral movements of the ballasted railway track especially in the continuous welded rail (CWR) occur in sharp curves because of high lateral forces. Several strategies have been proposed to increase the track lateral resistance which most of them related to track curves with small radii. In this paper, track lateral supports as a new method have b...

Increasing the axle load causes track deterioration and permanent settlement of the ballast layer. In the ballasted railway tracks, due to the inevitability of unequal settlements in the ballast layer, part of the rail due to high flexural rigidity will become suspended, which causes the formation of the track with unsupported and partially support...

Masonry bridges are among the main structures built along the road and railway routes. These structures are generally old and have historical value. Considering the increased axial load and passing speed from these bridges, an in-depth study of these structures and their potential is of paramount importance. In the present study, an old masonry arc...

This paper proposes an opportunistic preventive maintenance policy to schedule tamping interventions aiming to minimize the total maintenance cost. In this policy, the goal is to obtain an opportunistic maintenance threshold (OMT) to decide when to perform preventive tamping operations on given railway segments to minimize total maintenance cost as...

Effects of sand contamination of railways on the loading pattern of pre-stressed concrete sleepers were investigated, using a FE model of railway track developed and validated in this research. To derive properties of contaminated ballasts, various laboratory tests were conducted. For the investigation, parametric analyses of the model were conduct...

Tie type is one of the most effective parameters for changing the lateral resistance of ballasted track. In this study, the lateral resistance of an existing curve-to-lateral movement is investigated in the field in two conditions: with simple mono-block concrete ties (B70) and with friction concrete ties (B70F). After that, lateral resistance is m...

Railway networks are one of the major parts of the transportation infrastructure. Development of this network by the construction of new lines or the capacity improvement of existing lines needs time and capital cost. Decision makers, who are responsible for the infrastructure network, always have a limited budget. They need to select the best pack...

Lack of lateral resistance is one of the emerging problems in continuously welded rails. Lateral resistance is a type of resistance in which the railway track mobilizes against the applied lateral forces. Thus, curved tracks, especially sharp curves (curves with small radiuses), are the most susceptible segments for the lack of lateral resistance....

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 e...

The fastening system in the slab of the lines plays an essential role in transferring and adjusting the force to the traverse, so it is essential to check its behavior and select it correctly. Fastening systems are used for ballast lines and concrete slabs based on the amount of vertical stiffness obtained under the rail. Since W14 binding system h...

Transition zone is one of the vulnerable sections in railway tracks. This study was conducted to assess the effects of using under sleeper pads (USPs) in the transition zone from ordinary ballasted track to railway bridges. For this purpose, a railway bridge with two spans (with the length of 7 m) and an overall length of 15.5 m was selected, follo...

The quality of ballast materials is an important criterion in railway track maintenance management systems. Although various studies have been made on the characteristics of ballast aggregates and ballast mechanical behaviours, making an optimal decision on the selection of appropriate ballast materials is still a serious challenge in the railway i...

Ballast layer Geometry condition is an important criterion in the railway track maintenance since the track stability strictly depends on the ballast geometry. Currently, a visual inspection is a method of monitoring ballast layer geometry which is considerably costly and time-consuming. Addressing the limitations of the current ballast maintenance...

In this paper, mixed-integer programming for the railway network design problem with a new objective function is proposed. The model considers development projects (new line construction and existing line improvement), available budget, block capacity, and origin-destination matrix demand. A standard code is used to calculate the capacity of the bl...

Existence of short wave length irregularities and discontinuities in the rail, such as corrugation, isolated rail joints, crossings and rail breakage, result in impact forces and an increase in wheel-rail contact force. Extreme forces in such could result in non-linear behavior of ballast and pads, and as a result, employing common linear models mi...

Significant parts of railway lines in most of the Middle East and Asian countries are in sandy and desert areas. Contamination of tracks (in particular the ballast layer) caused by frequent sand storms in the desert is an important challenge for railway industries. Despite a large number of reported railway accidents caused by the loss of shear str...

Ballast layer has an important role in vertical stiffness and stability of railway track. In most of the Middle East countries and some of the Asian ones, significant parts of railway lines pass through desert areas where the track (particularly ballast layer) is contaminated with sands. Despite considerable number of derailments reported in the sa...

There is a growing need to minimise vibrations of railway structures, especially the railway bridges, due to the increasing speed of trains. Various methods are used to reduce the effects of vibration on bridges. One of the methods is using under-sleeper pads. In this study, a real railway bridge – located in the northern district of Iran – with tw...

Fastening systems, as one of the main components of railway superstructure, play an important role in providing the safety of railway tracks. Nowadays, the performance of railway tracks in the design and construction of new lines by using the different types of fastening systems have been increased. According to the variety of fastening systems, th...

Today's, transportation system is one of the most important parts of every country's economy and it has fundamental role in the development of economic infrastructure. Bridges have been formed many parts of railway tracks and masonry arch bridges with inherent special architecture are among the historic structures in railway engineering. There are...

Ballast plays an important role in the stability of railway track systems. The effectiveness of the ballast in maintaining the track stability is very much dependent on its mechanical conditions. The available ballast maintenance approaches are mainly based on only track geometry conditions (such as track profile) which do not sufficiently reflect...

Ballast shear interlocking is the phenomenon that occurs between adjacent ballast masses under sleepers due to axial loading. This phenomenon is caused when three factors: 1) large thickness of the ballast layer, 2) large stress distribution angle at ballast mass of under sleeper, 3) small sleeper spacing are available at the ballasted track. Thus,...

One of the important parameters for controlling the behavior of continuous welded rail (CWR) in railway tracks is rail support modulus. Reviewing the technical literature reveals some elapsed points in this regard such as continuous or discrete supports, V-shaped rail irregularity and geometrical stiffness which can considerably affect on the vehic...

As regards the ground-borne vibrations caused by unsupported railway sleepers in ballasted tracks have not been properly investigated till now, so this subject was studied in the current paper. In this matter, two separate finite element models including train-track dynamic interaction and ground-borne vibrations have been developed. At first, the...

This work aims to analyse and compare a number of durability related parameters including diffusivity, absorption and electrical resistivity in conventional concrete (CC) and self-consolidating concrete (SCC). Three different types of SCC were mix-designed containing different additions such as limestone powder (LSP), Viscosity Modifying Agent (VMA...

ABRUPT TRACK VERTICAL STIFFNESS VARIATIONS ALONG RAILWAY TRACKS CAN LEAD TO INCREASED DYNAMIC LOADS, ASYMMETRIC DEFORMATIONS, DAM-AGED TRACK COMPONENTS, AND CONSEQUENTLY, INCREASED MAINTENANCE COSTS. THE JUNCTION OF SLAB TRACK AND BALLASTED TRACK IS ONE OF THE EXISTING AREAS WHERE VERTICAL TRACK STIFFNESS CAN SUDDENLY CHANGE, THEREFORE REQUIRING A...

In this paper, the dynamic responses of train-bridge system under one-way and two-way high-speed train passing are studied. The 3D finite element modeling is used and the bridge and train are modeled considering their details. The created model is validated by the results of the dynamic field test. To study the effect of train speed, different trai...

Changes in axial force for control and prevent track buckling are vital to know the natural temperature. Thermal neutral temperature actually refers to the railway tracks where there is no pressure and no traction, or in other words the axial force is zero in rails. In this paper, the new definition for variations in neutral and float temperatures...

Railway track behaviour with unsupported prestressed sleepers has been investigated in the literature. However, some of the important factors – such as prestressing forces, variations of the sleeper cross-section along its length, losing or recovering contact between the sleeper and the ballast layer – have been omitted. These limitations have been...

Review of technical literature regarding to train-induced vibrations shows that the effects of unsupported railway sleepers on this issue have been less investigated. So, the present study was devoted to numerical investigations of the mentioned issue. In this regard, first the problem of longitudinal train–track dynamic interaction was simulated i...

Up to now, the effects of sleeper support modulus on the dynamic behaviour of railway tracks have attracted little attention from researchers. So the current study is allocated to investigating the issue through numerical simulations and field tests. For vehicle/track finite element simulations, a wagon system with 10 degrees-of-freedom, including...

An abrupt change in the stiffness of railway tracks at the junction between slab track and ballasted track causes increased dynamic loads, asymmetric settlements, damage of track components, and, consequently, increased maintenance costs. Due to this, a transition zone is usually built at the junction between the ballasted and the ballastless track...

This study is devoted to developing many new substructure models for ballasted railway track by using the pyramid model philosophy. As the effect of railway embankment has been less considered in the previous studies in the field of vehicle/track interaction, so the present study develops the pyramid models in the presence of railway embankment and...

Continuous welded rail (CWR) tracks have particular advantages over common tracks with jointed rails such as increased ride comfort, reduced noise and vibration and decreased maintenance costs due to the removal of joints in rail connections. Alternatively, some complications associated with CWR tracks, for instance increased lateral forces, are th...

Up to now, the effects of sleeper support modulus on the dynamic behaviour of railway tracks have attracted little attention from researchers. So the current study is allocated to investigating the issue through numerical simulations and field tests. For vehicle/track finite element simulations, a wagon system with 10 degrees-of-freedom, including...

یکی از پارامترهای مهم و تأثیرگذار برسازه‌ی خط‌آهن، ناهمواری‌های ریل است. پديده ناهمواري موجي شكل ريل¬ها (کاریوگیشن) از منابع اصلی تحريك دینامیکی اندرکنش خط و قطار به شمار می‌آید. در این مقاله به کمک مد¬ل¬سازی عددی اندرکنش خط و قطار با فرمول¬بندی مختصات متحرک ، اثرات توأم افزايش دامنه و طول‌موج کاریوگیشن-برای سرعت‌های تا ۳۶۰ کیلومتر بر ساعت -بر نيرو...

An important factor affecting the behavior of railway tracks is contamination of ballast material. In desert and wilderness areas, elasticity characteristics of railway ballast layer reduce and consequently rigidity of railway track is increased. This phenomenon has destructive effects on the railway lines especially railway sleeper and it could ca...

In spite of recent advances in ballasted railway track, the correct choice of ballast for rail track is still considered critical because aggregates progressively deteriorate under traffic loading and environmental exposures. Various ballast requirements, functions and duties have been defined by researchers, railway companies and countries` regula...

Rail support modulus is an important parameter for analysis and design of ballasted railway tracks. One of the challenges in track stiffness assessment is its dynamic nature under the moving trains which differs it from the case of standing trains. So the present study is allocated to establish a relation between the dynamic and static stiffness of...

The support condition of railway sleepers has a significant effect on the mechanical behavior of railway tracks due to the passing of different trains. One of the important issues in this regard relates to existing unsupported sleepers on the railway tracks. These sleepers cause changes in the dynamic responses of railway tracks under a moving trai...

When a train passes over bridges, the magnitude of forces and accelerations is altered due to sudden changes in the track stiffness. These forces can change with the variation in operational parameters and are effective particularly in high-speed passenger trains, when studying ride index parameter. In addition, by increasing the speed, old bridge...

Dynamic behavior of a track-train system is a function of axle loads and support stiffness because of non-linear supports. Therefore, it is expected that the support stiffness affects the behavior of the railway track during passing of a light or heavy car body. Since the effects of axle loads caused by light and heavy railway vehicles and support...

This article focuses on evaluating the dynamic behavior of ballast mixed with tire derived aggregate as an economic and environmental preserving method to obviate the rigidity problems in railway tracks. For this purpose, the ballast was mixed with 0, 11, 22, and 33 volume percentages of tire derived aggregate in a loading chamber and was examined...

This paper is devoted to investigating of dynamic behavior of a ballasted railway track by field tests and numerical analyses. In this regard, at first in a field test program, two different sections in a ballasted track including concrete and wooden sleepers with good quality are selected and their dynamic vertical deflections are measured due to...

Continuously welded rails are a common remedy to prevent rail defects, including railhead batter, rail cracking or breakage, and lateral displacement of track, among others. However, at curves with a radius of less than 400 m, rail welding is practically impossible due to the lack of track lateral resistance. Therefore, finding a new method to incr...

The railway track technical literature lacks proper reports on the key effects of the support stiffness on the track behavior with various sleeper geometries. Hence, it is the aim of this research to report on the assessment of the track foundation stiffness. The pyramid model equations are developed for three different stress conditions including...

Lateral resistance of railway track is one of the most important parameters in lateral stability. This parameter depends on the conditions of different components of ballasted railway track (such as density of ballast layer, sleeper spacing, type of sleeper, etc.). From this perspective, type of sleeper has an important effect on lateral resistance...

Buckling and geometric variation of railway track are the phenomena that threaten railway stability. The lateral resistance is the factor that maintains stability of railway track against them. In ballasted tracks, there are some regions that lateral forces increase, for example, in areas with high differences in temperature or in curves with low r...

One of the major problems of railroad deterioration is uneven settlement which occurs due to various reasons, including existence of defects in substructures, using non-homogenous ballast, or being poorly drained. Sometimes, because of these problems, sleepers remain freely as a part of vertical displacement and contact the ballast with load increa...