Prestressed Concrete Sleepers Research Articles

Influence of Surface Abrasion on Creep and Shrinkage of Railway Prestressed Concrete Sleepers

Ballasted railway track is very suitable for heavy-rail networks because of its many superior advantages in design, construction, short- and long-term maintenance, sustainability, and life-cycle cost. The sleeper, which supports rail and distributes loads from rail to ballast, is a very important component of rail track system. Prestressed concrete is very popular used in manufacturing sleepers. Therefore, improved knowledge about design techniques for prestressed concrete (PC) sleepers has been developed. However, the ballast angularity causes differential abrasions on the soffit or bottom surface of sleepers. Furthermore, in sharp curves and rapid gradient change, longitudinal and lateral dynamics of rails increase the likelihood of abrasions in concrete sleepers. This paper presents a comparative investigation using a variety of methods to evaluate creep and shrinkage effects in railway prestressed concrete sleepers. The outcome of this study will improve the material design, which is very critical to the durability of railway track components.

Impact capacity reduction in railway prestressed concrete sleepers with vertical holes

Railway prestressed concrete sleepers (or railroad ties) are principally designed in order to carry wheel loads from the rails to the ground as well as to secure rail gauge for dynamic safe movements of trains. In spite of the most common use of the prestressed concrete sleepers in railway tracks, the concrete sleepers are often modified on construction sites to fit in other systems such as cables, signalling gears, drainage pipes, etc. This is because those signalling, fibre optic, equipment cables are often damaged either by ballast corners or by tamping machine. It is thus necessary to modify concrete sleepers to cater cables internally so that the cables or drainage pipes would not experience detrimental or harsh environments. Accordingly, this study will extend from the previous study into the design criteria of holes and web openings. This paper will highlight structural capacity of concrete sleepers under dynamic transient loading. The modified compression field theory for ultimate strength design of concrete sleepers will be highlighted in this study. The outcome of this study will improve the understanding into dynamic behavior of prestressed concrete sleepers with vertical holes. The insight will enable predictive track maintenance regime in railway industry.

Influence of vertical holes on creep and shrinkage of railway prestressed concrete sleepers

Railway prestressed concrete sleepers (or railroad ties) must successfully perform two critical duties: first, to carry wheel loads from the rails to the ground; and second, to secure rail gauge for dynamic safe movements of trains. The second duty is often fouled by inappropriate design of the time-dependent behaviors due to their creep, shrinkage and elastic shortening responses of the materials. In addition, the concrete sleepers are often modified on construction sites to fit in other systems such as cables, signalling gears, drainage pipes, etc. Accordingly, this study is the world first to investigate creep and shrinkage effects on the railway prestressed concrete sleepers with vertical holes. This paper will highlight constitutive models of concrete materials within the railway sleepers under different environmental conditions over time. It will present a comparative investigation using a variety of methods to evaluate shortening effects in railway prestressed concrete sleepers. The outcome of this study will improve material design, which is very critical to the durability of railway track components.

Investigation on possible causes of expansion damages in concrete – a case study of sleepers in Indian Railways

Indian Railways uses factory made pre-tensioned pre-stressed concrete sleepers for its track. These sleepers start cracking after 6-9 years of their manufacturing in many areas of the Indian Railways. For the investigation of the premature cracking of sleepers, different categories of samples namely “Severely damaged”, “Moderately damaged”, and “Undamaged” are collected from different locations of Indian Rail- ways. These samples are analyzed under Scanning Electron Microscope (SEM) and Energy Dispersive Spec- troscopy (EDS). SEM images reveal that there is large ettringite deposition at the interfaces of aggregate and paste in case of “Severely damaged” and “Moderately damaged” sleepers, which could be a cause of delete- rious expansion and subsequent cracking, whereas the interfaces of “Undamaged” sleepers were found to be intact. High temperature experienced by these sleepers in form of steam curing during their production in factories may lead to Delayed Ettringite Formation (DEF) and subsequent expansion and cracking. Tempera- ture recorded in the concrete sleeper plant during steaming of the sleepers reveals that the temperature inside concrete exceeds 80°C, which is a critical temperature for the occurrence of damage due to DEF in future. Also, stress bench method of production of concrete sleepers, used in Indian Railways for older concrete sleeper plant, poses some structural deficiency which adversely affects the temperature of curing. Thus, DEF could be the possible cause of premature cracking of sleepers in Indian Railways.

Prestressed Concrete Sleepers Importance and Innovation

Prestressed Concrete Sleepers Importance and Innovation

Reply to Giannakos, K. Comment on: Toughness of Railroad Concrete Crossties with Holes and Web Openings. Infrastructures 2017, 2, 3

This paper responds to the discussion [1] by Dr. K. Giannakos over our technical note [2].[...]

Retraction notice to “Analytical study on longitudinal crack control for B70 mono-block pre-stressed concrete sleepers” Engineering Failure Analysis, Volume 49, March 2015, Pages 1–10

Retraction notice to “Analytical study on longitudinal crack control for B70 mono-block pre-stressed concrete sleepers” Engineering Failure Analysis, Volume 49, March 2015, Pages 1–10

Strain Rates in Prestressed Concrete Sleepers and Effects on Cracking Loads

Prestressed concrete sleepers (PCSs) play an essential role in structural response and performance of ballasted railway tracks. Due to defects in track or train components, high magnitude dynamic loads may generate at the rail head and transfer to the PCSs which can generate cracks in PCSs. Cracking from dynamic loads have been reported as the most critical problem of PCSs around the world and impose an early replacement of sleepers which is a financial burden to the rail industry. This paper investigates the effects of strain rates on the strength enhancement of PCS. By using available measurements, the strain rates are calculated at two critical points of the PCSs, the rail seat and midspan. Considering the dynamic increase factor (DIF) of concrete, the cracking loads of a PCS are calculated and are compared with commonly occurring dynamic loads. Results show that the maximum strain rates at both rail seat and midspan are about 0.08 and 0.016 1/s, respectively. The increase of cracking wheel load due to the strain rate effects is about 5 to 26 percent. The results are also shown to be able to demonstrate the level cracking from dynamic loads with very short return periods.

Impact analyses for negative flexural responses (hogging) in railway prestressed concrete sleepers

By nature, ballast interacts with railway concrete sleepers in order to provide bearing support to track system. Most train-track dynamic models do not consider the degradation of ballast over time. In fact, the ballast degradation causes differential settlement and impact forces acting on partial and unsupported tracks. Furthermore, localised ballast breakages underneath railseat increase the likelihood of centrebound cracks in concrete sleepers due to the unbalanced support under sleepers. This paper presents a dynamic finite element model of a standard-gauge concrete sleeper in a track system, taking into account the tensionless nature of ballast support. The finite element model was calibrated using static and dynamic responses in the past. In this paper, the effects of centre-bound ballast support on the impact behaviours of sleepers are highlighted. In addition, it is the first to demonstrate the dynamic effects of sleeper length on the dynamic design deficiency in concrete sleepers. The outcome of this study will benefit the rail maintenance criteria of track resurfacing in order to restore ballast profile and appropriate sleeper/ballast interaction.

Influence of technological and environmental factors on the behaviour of the reinforcement anchorage zone of prestressed concrete sleepers

The article analyses the influence of technological factors on variations in the stress and strain state during the production of prestressed concrete sleepers. The paper focuses on technological damage to the anchorage zone and its influence on concrete and the pretensioned reinforcement of the last prestressed concrete sleepers located by abutments. The article presents the calculation principles of stresses caused by thermal and humidity deformations, compares theoretical and experimental results and specifies the nature of damages. The paper deals with concrete structure and an interface between reinforcement and concrete of new and three years old prestressed concrete sleepers, explores the results of laboratory tests on deteriorating the ends of new prestressed concrete sleepers under freezing and thawing cycles, looks at changes in concrete structure and the interface between reinforcement and concrete at the ends and in the middle of prestressed concrete sleepers applying a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Secondary ettringite formation (DEF) in concrete micro-cracks and at the interface between reinforcement and concrete and elemental composition of the formed crystals have been determined. Significant difference in concrete structure and new solid phases at the ends of used and new sleepers has been defined. Concrete structure in the middle of the three years old railway sleeper has remained almost unchanged. The obtained results show that technological factors are affecting the deterioration nature of the ends of prestressed concrete sleepers.

Sensitivity analysis of pre-stressed concrete sleepers for longitudinal crack prorogation effective factors

Abstract B70 mono-block pre-stressed concrete sleepers are one of the most common sleepers in Iran's railways industry. They have been used in many of the country's railway transition lines. The B70 types of sleepers are classified as pre-stressed concrete beams; therefore the value of pre-stressing force is one of the most important parameters in the field of sleepers' structural designing. Selecting high pre-stressing force due to the fact that it increases the steel bars strength, could increase the possibility of longitudinal cracks formation before service loading, especially if the tensile strength is low. Therefore, pre-stressing force and tensile strength are two important factors for investigating the sensitivity of longitudinal crack formation and propagation in sleepers. Sensitivity analysis has been conducted for tensile strength of concrete and the pre-stressing force in the steel bars, by using finite element method. It could be clearly seen in the results that increasing the tensile strength of concrete, increases the cross section capacity. This increase in the capacity does not have a direct relationship with the increase of the tensile strength. Also the numerical model indicates a linear behavior between different pre-stressing forces and maximum tensile stress around the dowels. Applying higher pre-stressing force values can increase the possibility of longitudinal cracks prior to service loading of the sleepers and also long-term sleepers' service life.

Experimental study on transfer length of an eco-friendly prestressed concrete sleeper

This study focuses on investigating transfer length in a newly developed eco-friendly concrete prestressed concrete sleeper. A next generation prestressed concrete sleeper was developed at the Korea Rail Research Institute (KRRI) in order to improve structural performances of the current prestressed concrete sleepers while addressing some environmental issues such as CO2 emissions and a lack of natural resources. The authors used ground granulated blast furnace (GGBF) slag and electric arc furnace (EAF) oxidizing slag to reduce the amount of Portland cement (III) and natural sand. To ensure the safety and structural integrity of the newly developed sleeper prior to a mass production and installation in the field, the structural performances of this newly developed eco-friendly concrete sleeper ought to be studied. One of important structural performances of prestressed concrete members which should be measured is transfer length. Unlike other civil engineering fields, no design guidelines for transfer length in prestressed concrete sleepers have been established in the railway industry. For example, the American Concrete Institute Building Code and the American Association of State Highway and Transportation Officials Bridge Design Specifications specify the required transfer length in prestressed concrete beams or girders depending on the size of prestressing wires or strands. Therefore, this study examines transfer length in the newly developed eco-friendly concrete sleeper and compares that with the transfer length in traditional prestressed concrete sleepers. Four sleepers are manufactured for each concrete, and the transfer length in each sleeper is monitored at the day of prestress release, and 7, 28 and 90days. As monitoring the behavior of the sleepers over 90days, the long-term effect on the transfer length is also investigated. The study demonstrates that the transfer length in the eco-friendly concrete sleepers is not only shorter than that of the traditional prestressed concrete sleepers, but also found to be more desirable since the prestress is fully developed prior to the railseat area.

Structural Behaviours of Railway Prestressed Concrete Sleepers (Crossties) With Hole and Web Openings

As the crosstie beam in railway track systems, the prestressed concrete sleepers (or railroad ties) are principally designed in order to carry wheel loads from the rails to the ground. Their design takes into account static and dynamic loading conditions. It is evident that prestressed concrete has played a significant role as to maintain the high endurance of the sleepers under low to moderate repeated impact loads. In spite of the most common use of the prestressed concrete sleepers in railway tracks, there have always been considerable demands from rail and track engineers to improve serviceability and functionality of concrete sleepers. For example, signalling, fibre optic, equipment cables are often damaged either by acute ballast corners or by tamping machine operation. There has been a significant need to re-design concrete sleeper to cater cables internally so that they would not experience detrimental or harsh environments. Accordingly, this study is the world first to experimentally investigate the effects of holes and web openings on structural behaviours of concrete sleepers under rail loading condition. The modified compression field theory for ultimate strength behaviours of concrete sleepers will be highlighted in this study. The outcome of this study will enable the new design and calculation methods for prestressed concrete sleepers with holes and web opening that practically benefits civil, track and structural engineers in railway industry.

Modelling Railway Prestressed Concrete Sleepers (Crossties) With Holes and Web Openings

Pre-stressing in concrete railway sleepers yields endurance property under high-cycle fatigue. This structural effect plays a positive role in durability of the sleepers. However, as a common practice, track engineers often generate holes or web openings in concrete sleepers to enable the accommodation of rail equipment cables and signaling equipment. This study aims to provide a principle understanding of the structural capacity and energy toughness of pre-stressed concrete sleepers with and without holes and web openings. It will investigate the design criteria and effects of holes and web openings on the structural capacity of concrete sleepers under rail loading. The finite element modelling for ultimate strength design of concrete sleepers will be highlighted in this study. Static experimental investigations have been firstly carried out to validate the finite element models using ABAQUS. The models are capable of predicting the failure planes and can help provide practical guidelines for the holes and web opening for track engineers.

Structural performances of an eco-friendly prestressed concrete sleeper

This study focuses on investigating structural performances of a newly developed eco-friendly prestressed concrete sleeper for railway tracks in South Korea. An eco-friendly concrete has been developed by authors at the Korea Railroad Research Institute (KRRI) with the aims of reducing carbon dioxide (CO2) emissions and finding a replacement of natural sand for fine aggregate. Direct and indirect CO2 emissions are one of the main environmental issues in the concrete industry. Reducing the amount of cement usage is beneficial to address the issue of CO2 emissions in the concrete industry. Another environmental issue in the concrete industry in South Korea is the shortage of natural sand as a fine aggregate. So there is a need for finding a replacement of natural sand. The authors utilized two types of recycled industrial byproducts (slags) to handle the environmental issues of railway prestressed concrete sleepers: (1) ground granulated blast furnace (GGBF) slag, which replaces 30% of Portland Type III cement and (2) electric arc furnace (EAF) oxidizing slag, which entirely replaces natural fine aggregate. With the recycled industry slags, an eco-friendly concrete was developed with a high initial compressive strength at prestressing release (<24h) and 28-day compressive strength, which are essential properties for manufacturing prestressed concrete sleepers. Herein, required laboratory tests such as static test, dynamic test, fatigue test, and vertical test for fastening components are carried out to evaluate structural performances of the eco-friendly prestressed concrete sleepers according to international and domestic prestressed concrete sleeper standards. Experimental results demonstrate that the eco-friendly prestressed concrete sleeper not only satisfies the structural requirements of prestressed concrete sleepers in accordance with the international and domestic standards, but also shows superior structural performances compared with those of normal prestressed concrete sleepers.

CONSTANT AMPLITUDE SPECTRUM OF THREE COACHES TRAIN AND CYCLIC COUNTING ON PRESTRESSED CONCRETE SLEEPERS (PCS)

The raw strain data collected from Keretapi Tanah Melayu Berhad (KTMB) railway are in variable amplitude. This paper discovers how the variable amplitude data can be changed to the constant amplitude data. It is found that the raw strain data is not suitable for fatigue and strength testing on Prestressed Concrete Sleepers (PCS). Apart from that, the most suitable method in determining the numbers of cycles is Rainflow Cycle Counting Method. Through rainflow cycle counting method, the number of cycles is determined. The numbers of cycles are used to simplify the laboratory test such as fatigue and strength test for the PCS. The frequencies of dynamic loading test on the PCS are set based the numbers of cycles. The constant strain data are also converted into constant loading data using the relationship of stress-strain and loading-stress. Constant amplitude loading will again simplify the laboratory testing. The goal is to show that the designs used in PCS are appropriate based on current loading demand. Then, a comparison of constant amplitude data is made between different numbers of coaches and freight train. The maximum data from the comparison shows that the higher loadings are obtained from freight train.

CONVERTING CONSTANT AMPLITUDE LOADING OF PRESTRESSED CONCRETE SLEEPER (PCS) FROM VARIABLE AMPLITUDE

Prestressed Concrete Sleepers are structures that support railway system and absorb variable loading from the train that pass along the rail. In this study, variable amplitude loading from PCS taken from site measurement was converted into constant amplitude loading. Therefore the number of cycles and frequency are also important to be determined. There are various method for counting the number of cycles and the best adoptive method was Rainflow Cycle Counting. Once the number of cycles is obtained as well as the constant amplitude stress in a series of stress block, the prediction of fatigue life of PCS can be analyzed by further research in the laboratory work. However the limitation of this study is only to obtain the constant amplitude loading of PCS and also counting the number of cycles in various series of stress blocks.

Fracture mechanics analysis of pre-stressed concrete sleepers via investigating crack initiation length

This paper presents an investigation on pre-stressed concrete sleepers based on the principles of fracture mechanics in concrete material. To evaluate fracture mechanics parameters pre-stressed concrete sleepers with different initiation crack length varying between 0mm and 45mm increasing by 5mm steps are used. A three-point bending loading condition is considered. Finite element software is employed to model the sleepers and to calculate the parameters of fracture mechanics such as KIc and crack growth. Finally, in this study for validation, load–displacement diagram of 5 experimental samples is compared with numerical model of finite elements for validation of model. The paper shows that an expansion in crack instability follows from increasing crack-to-depth ratio, initial toughness, the crack stability and crack unstable toughness, the crack instability expansion begins. The paper also shows a good agreement between the numerical and experimental results via comparing the results of the 5 samples with the numerical model.

Climate effects on the shoulder width measurements of prestressed concrete high speed railway sleepers of ballasted tracks

Sleepers are the primary structural components that provide the necessary gauge width and the structural stability to the ballasted railway track. High performance prestressed concrete sleepers of high-speed railways have strict design and production requirements to provide a safe, serviceable and a reliable railway superstructure. The production dimensions of a contemporary prestressed high performance concrete sleeper are within low tolerance values on the scale of a millimeter that is uncommon for ordinary structural concrete elements. Railways are within climatic conditions that could become effective in the dimensional stability of their sleepers. Within regions of low humidity levels, in addition to the elastic shortening of the prestressed sleepers, the effects of concrete creep and shrinkage could lead to total contraction values in excess of the allowed tolerances for the shoulder width of the sleepers. Therefore the dimensional design of a high performance prestressed concrete sleeper must include the effects of time dependent dimensional changes. This paper presents the possibility of falling out of dimensional tolerance for prestressed high performance sleepers and ways to mitigate those possibilities for railways in arid climatic conditions or within climatic zones undergoing a climate change.

Constant Amplitude of Prestressed Concrete Sleeper (PCS) Subjected to Three Coaches Train

- Concrete sleeper is the main structrural component in railways track. Concrete sleeper is used to transmit the load from the train to the ballast. In this study, the pattern of load applied to the concrete sleeper was determined. The pattern of load is important as it affecting the design and lifetime of conrete sleeper. The raw data for load of train will produced variable amplitude value as the concrete sleeper will be experiencing the different type of loading. The value of raw data when the wheel of train hit the concrete sleeper will be higher than the raw data when the conrete sleeper is experiencing vibration due to incoming train. In this study, the pattern of load will be analysed to understand the behaviour of the load applied to concrete sleeper. Other than that, the variable amplitude value of raw data will convert into a constant amplitude value using a method of calculation. The determination of constant value amplitude will be divided into N-section to finding the maximum and minimum value for the section. In addition, the actual number of cycle from the raw data will determined using Rainflow Counting method. This study can be further used for laboratory work as it’s determine the suitable loading and cycle applied to the concrete sleeper under dynamic loading.