Prestressed Concrete Sleepers Research Articles

Aspects of Modeling Prestressed Concrete Sleepers Subjected to Positive Moment Test at Midspan

Aspects of Modeling Prestressed Concrete Sleepers Subjected to Positive Moment Test at Midspan

Strength Behavior of Prestressed Concrete Sleepers with Steel Slag Partial Replacement

Prestressed concrete sleepers (PCS) are very popular and commonly used by Indian Railways. This research is aimed at studying the behavior of concrete sleepers made with steel slag as a partial replacement for traditional cement concrete. A pre-stressed concrete railway sleeper was made using energy-optimizing furnace (EOF) steel slag, a byproduct in the steel manufacturing process, partially in the place of coarse aggregate, following the Indian Railways Standard (T39-85) for sleepers. EOF steel slag coarse aggregates were subjected to a few tests, including those for chemical resistance, soundness and alkali reactivity and the results were found to be satisfactory. Compared to the traditional concrete mix, the compressive strength is increased by about 20%. It paves the way to utilize the discarded steel slag for manufacturing cost-effective prestressed railway sleepers.

Effect of post-peak flexural toughness on the residual performance of macro synthetic fibre reinforced concrete sleepers subjected to impact loading

Dynamic impact loading is one of the predominant causes of premature failure of concrete railway sleepers, demanding a fair portion of the railway budget. Therefore, macro synthetic fibre reinforced concrete (MSFRC) is suggested as an alternative owing to its improved post-peak flexural capacity, ductility and crack arresting properties. In such adaptation, the residual behaviour after dynamic impacts caused by wheel-rail irregularities governs the reusability and the life cycle of the sleepers. Correspondingly, the residual performance of impacted MSFRC sleepers was evaluated experimentally compared to conventional prestressed concrete sleepers. The residual behaviour of the sleepers was further supported by a series of material-scale flexural experiments. The fracture toughness of MSFRC increased with the crack-opening width because of the tension stiffening associated with fibre bridging. As a result, the residual capacity, stiffness, and toughness of MSFRC sleepers were higher than conventional sleepers, thereby improving their adaptability to the rail network.

Self-Healing of Cracks in Cementitious Materials as a Method of Improving the Durability of Pre-Stressed Concrete Railway Sleepers.

The article presents research results regarding the possibility of modifying pre-stressed concrete railway sleepers to improve their durability. The cracks that appear in these elements are one of the reasons for shortening the period of safe use. They do not have a significant impact on the load-bearing capacity of these elements, but on their durability. The resulting scratches become an easy way for the external environment to migrate inside the element, including the reinforcement area. Despite efforts to eliminate the possibility of cracking, this phenomenon still occurs in railway sleepers. In order to reduce the negative effects of cracking the cement matrix, a technology for modifying a prefabricated concrete element with resin-filled tubes towards its autonomous self-healing was developed and tested. The tests were divided into three stages, including laboratory tests carried out on cement mortar beams, semi-technical tests carried out on reinforced concrete beams, and industrial tests carried out on pre-stressed concrete and prefabricated railway sleepers. All research conducted on a laboratory and semi-technical scale, preceding the target stage, was intended to ultimately enable the development of tube application technology on an industrial scale while verifying the effectiveness of self-healing at the laboratory level. The use of self-healing cementitious materials potentially reduces the negative effects of cracking railway sleepers, as shown by observations conducted during the research.

Full-scale static behaviour of prestressed geopolymer concrete sleepers reinforced with steel fibres

Profusive cracking leading to the deterioration of prestressed concrete sleepers has retained the sleepers from being exploited to their full extent. In addition, excess utilization of cement in producing the same has paved the way for developing its counterpart, geopolymer concrete (GPC), involving primary industrial residues as their precursors. This study presents a comprehensive investigation into the development and performance of high-strength geopolymer concrete sleepers for railway applications. The research focuses on the complete replacement of ordinary Portland cement with Fly ash and Ground Granulated Blast Furnace Slag in the geopolymer concrete mix, for mainline prestressed railway sleepers following Indian Railway Standards (IRS). Notably, the study includes experimental validations of long steel fibers as secondary reinforcement to the primary prestressing strands, aiming to enhance the ductility of the member. Experimental validations were performed on full-scale (1:1) sleeper members under static loading conditions. The main aim of this article was to assess the load carrying capacity at cracking and ultimate limits, rail seat bending moment, ductility indices, failure mechanism, electrical impedance, bond strength, and the eco-efficiency for the proposed prestressed geopolymer concrete sleeper members (with and without steel fibres) with reference to the conventional prestressed cement concrete sleepers. The considered GPC mix was found to achieve higher load and moment carrying capacity by about 8.3% and 8.54% respectively compared to the conventional concrete mix. The addition of steel fibres in the GPC increased the load and moment capacity of sleepers by 23% and 24.21% respectively. Additionally, the steel fibre reinforced GPC showed improved displacement ductility demand over the plain geopolymer concrete averaging 25%, 28.5%, and 3% corresponding to ultimate, failure, and residual ductility index respectively. Though inclusion of steel fibers improves the performance of sleepers in terms of load and ductility, they were found incompatible with regard to the electrical impedance property when used in conjunction with the pre-stressing strands.

ANALYSIS OF THE CAUSES OF DEGRADATION PRESTRESSED REINFORCED CONCRETE RAILWAY SLEEPERS

Railway sleepers are a very important component of the transport infrastructure, they are dynamically loaded and subject to many stresses that can cause degradation, shorten their service life and also reduce the safety of rail transport. The subject of the study was damaged-highly cracked prestressed concrete railway sleepers, 10 years old, sampled on the railway line route. The results of the investigations carried out to determine the characteristics of the concrete are presented. In order to determine the cause of the damage, low-frequency fatigue tests were also carried out in the laboratory to measure vibrations and to check for cracks. By checking the microstructure of the concrete with SEM-SEI and EDS electron microscopy, we found that the cracks were caused by chemical reactions in the hydrated concrete. The results of the analyses carried out can improve the criteria for the inspection and assessment of the serviceability of degraded railway sleepers during their service life.

Investigation of Load Environment and Bending Load Capacities of Aged Prestressed Concrete Sleepers

In this study, field measurements of the bending moments of prestressed concrete (PC) sleepers installed on commercial lines were obtained, and numerical analyses to identify the effects of different parameters on their bending moments were conducted. The bending load capacities of aged PC sleepers collected from commercial lines via bending tests were also determined. According to the field measurement results of the wheel loads and bending moments of the PC sleepers, the measured values were smaller than the design values. In addition, neither the wheel load nor the bending moment depended on train speed. The numerical analysis results indicate that the positive bending moment at the rail seat section is unlikely to exceed the design decompression moment (DDM). However, the negative bending moment at the center section may exceed the DDM if center support is provided with a reduced spring constant under the rail (the “hanging” rail seat section). In addition, the bending moment increased with the rail surface roughness, so the rail should be kept smooth. Moreover, the results of the JIS E 1201 bending tests on the aged PC sleepers showed that the crack generation load and ultimate load decreased gradually with increases in age and passing tonnage. However, all samples satisfied the JIS standard values. Furthermore, the bending moments generated in the PC sleepers during train passage were considerably smaller than the crack generation load and ultimate load during the bending test. Thus, Japanese PC sleepers aged more than 50 years currently satisfy the standard flexural fracture values specified by the JIS, and safety is not immediately compromised.

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

The Typical Damage Form and Mechanism of a Railway Prestressed Concrete Sleeper.

Prestressed concrete sleepers are an important track component that is widely used in railway ballast track. Prestressed concrete sleepers have high strength, strong stability, and good durability; thus, their operation and use in railways are beneficial. However, in different countries and regions, certain damage to sleepers typically appears. Existing research on concrete sleepers focuses primarily on the structural design method, the application of new materials, theoretical analysis, and bearing strength test research, while ignoring sleeper damage. There are a few sleeper damage studies, but they look at only one type of damage; thus, there is no comprehensive study of prestressed concrete sleeper damage. The damage forms of prestressed concrete sleeper damage are thus summarized in this study, and the theory of the causes of prestressed concrete sleepers is analyzed based on the limit state method for the first time. The findings indicate that sleeper structure design is the primary cause of its operation and use status, and that special measures should be considered based on sleeper use conditions. In addition to meeting design requirements, materials, curing systems, product inspection, and other factors must be considered during manufacturing to improve the sleepers' long-term performance. Keeping the track in good condition, including but not limited to the state of fasteners, ballast bed, and track geometry is also an important aspect of preventing sleeper damage. The outcomes of this study provide better insights into the influences of damage to railway prestressed concrete sleepers and can be used to improve track maintenance and inspection criteria.

Machine Learning Based Design of Railway Prestressed Concrete Sleepers

The state-of-the-art design methods for railway prestressed concrete sleepers are currently based on the quasi-static stresses resulting from a simplification of dynamic wheel loads, and subsequently the quasi-static responses of concrete sleepers. This method has been widely used in practices to overcome the complexity of dynamic analysis and testing. A single load factor (or called dynamic impact factor) for a partial safety-factored design (or k factors for the test criteria) is commonly used to crudely account for dynamic train–track interactions over different levels of track irregularities. The dynamic impact factors for either design or testing are usually obtained from either (i) railway infrastructure managers (i.e., in EN 13230), or (ii) prescribed standardised factors (i.e., AS 1085.14, AREMA Chapter 30, JSA—JIS E 1201). The existing design concepts for prestressed concrete sleepers using either (i) an allowable stress design or (ii) the limit state design method require many iterations for calculations and optimisations. The design process to achieve optimal products suitable for track, operational, and environmental parameters is, thus, very time-consuming. On this ground, this study investigates the potential capability of machine learning (ML) to learn from large amounts of design data sets and then to facilitate the design and capacity prediction of railway prestressed concrete sleepers. Three ML algorithms are developed, namely deep learning, Bayesian Neural Network, and random forest. Through a combination of hand-calculated design data, industry design data, and experimental investigations in compliance with EN 13230, over 3000 sets of design data have been collected. These data sets are used to assimilate a comprehensive database for machine learning. Four indicators, namely mean squared error (MSE), root-mean-square error (RMSE), mean absolute error (MAE), and R2 are used to benchmark the accuracy and precision of machine learning models. Our results reveal that the random forest algorithm offers the best performance. The values of MSE, RMSE, MAE, and R2 are 0.54, 0.74, 0.25, and 0.99, respectively. Note that the Bayesian neural network also performs very well. In contrast, the deep learning algorithm performs worse than the others. The insight demonstrates machine learning’s capability to aid in the design of railway prestressed concrete sleepers, to satisfy both serviceability and ultimate limit states

Remaining Fatigue Life Predictions of Railway Prestressed Concrete Sleepers Considering Time-Dependent Surface Abrasion

One of the safety-critical components of ballasted track systems is railway sleepers whose main functions are to (i) transfer vertical load, (ii) maintain rail gauge, and (iii) restrain longitudinal rail movement. Railway sleepers can be manufactured using timber, concrete, steel, composite, and any other engineered materials. Prestressed concrete sleepers are the most commonly used type worldwide because of their superior value-for-money performance. In practice, railway sleepers experience thousands of cycles of aggressive wheel–rail dynamic loads and wear deterioration can be observed over their service life. Not only does the deterioration affect track quality and geometries, but it also undermines the structural integrity of the track structures. The wear and abrasion directly decrease the capacity of railway sleepers, resulting in the reduction in service life. In this paper, the emphasis is placed on the assessment of the fatigue life of prestressed concrete railway sleepers with imperfect geometry. This study is the world’s first to establish a new fatigue simulation of railway concrete sleepers considering accumulative non-constant amplitudes, which has been validated using full-scale experimental results and empirical analyses. Parametric studies have been conducted to obtain new insights into the fatigue performance of the worn sleepers. The new findings will improve railway sleeper maintenance and inspection criteria, and will provide a new guideline on track-condition monitoring networks.

Progressive failure analysis of partially pre-stressed concrete railway sleepers

Billions of sleepers are used on railways around the world today. As the importance of railways in the transportation sector is increasing, the demand for sleepers is also increasing. Although wooden and steel sleepers were used in rail systems in the past, today the most widely used sleeper type in the world is reinforced concrete sleepers. Among these reinforced concrete sleepers, pre-stressed sleepers are the most widely used, popular type of sleeper that can be produced in many countries. The two main production methods of pre-stressed sleepers are the ribbed reinforced system and the non-ribbed reinforced anchor plated system. In this study, B70 type pre-stressed concrete sleepers, have been investigated with the positive moment determination tests at the rail seat with progressive failure observations according to EN 13230-2:2016 standard. After tests, detailed cracking, failure, and fatigue analyzes under increasing test loads were performed with ANSYS® finite element analysis results for both types of pre-stressed sleepers. According to results, A-type sleepers have 50% more compression stress at the first crack formation load (Frr) than N-type sleepers and According to the first 0.05 mm permanent crack formation load (Fr0.05), it is seen that 25% higher stresses occur in A-type design than N-type design under Fr0.05 load. The results obtained through the analysis have been compared with the actual field measurement results, which have become more and more popular in the world in recent years. In this direction, various suggestions have been made for the development of concrete railway sleeper models.

Comparative modal analysis of B70 and LCR-6 type railway sleepers after repeated impact loads

Due to today's high-frequency trainloads and wheel or rail irregularities, the railway system is more exposed to impact loading conditions. In this study, laminated carbon fiber reinforced polyurethane (L-CFRPU) products were used, with a new non-pre-stressed production process, to improve the impact damping characteristics of concrete railway sleepers. New designed LCR-6 type sleepers were compared with standard B70 type pre-stressed concrete sleepers by performing modal analysis before and after a 50 times repeated-330 kN impact loading procedure. This is the first study to compare new LCR-6 type sleepers with prestressed competitors after impact loads. According to the analysis results, FRF magnitude values ​​decrease up to 83% lower in impacted LCR-6 type sleepers compared to impacted B70 type sleepers. After the impact loading procedure, the cracks formed in LCR-6 type sleepers closed and remained below 50-µm width, and according to the simultaneous mechanical test results, these few hairline cracks do not cause a significant mechanical capacity loss, while increasing the damping ratios by 274%. This advantage will be beneficial in extending the service life of sleepers and protecting other railway components from vibration and impact damage. Therefore, while the pre-stressed concrete sleepers have a negative course during their service life, the non-pre-stressed LCR type sleepers show a positive acceleration.

Mechanisms and Evolution of Cracks in Prestressed Concrete Sleepers Exposed to Time-Dependent Actions

Railway sleepers are an important component of track systems, which can be manufactured by timber, concrete, steel and any other engineered materials. They serve as rail supports and transfer loads from trains to substructures of track systems. In railway networks worldwide, prestressed concrete sleepers are more common than other material types because of their cost-efficacy, environmental friendliness, higher stability and performance, and durability. However, certain types of damage can still appear due to diverse load spectra and aggressive environmental conditions. The causes of cracking observed in prestressed concrete sleepers are usually induced by impact loads. The most affected sections are at the midspan and the rail-seat area of sleepers. Over a long term, time-dependent actions also affect the structural performance of prestressed concrete sleepers. This paper intends to determine the time-dependent crack phenomena in prestressed concrete sleepers under static conditions. Nonlinear finite element method (FEM) has been developed and validated by full-scale experimental tests of prestressed concrete sleepers in accordance with EN13230. In this study, equivalent losses of prestress as a result from time-dependent actions and resultant behaviours are considered. Their influences on crack initiation and propagation in prestressed concrete sleepers have been demonstrated. The results exhibit that the crack simulation can accurately predict the cracking behaviours and the time-dependent behaviour of prestressed concrete sleepers. This insight is critically essential to experimental load rating prediction, that can appropriately estimate the remaining life of aged railway concrete sleepers exposed to time-dependent actions.

Fatigue life modelling of railway prestressed concrete sleepers

Railway sleepers, which transfer wheel loads to the formation, are an essential component of railway track systems. Prestressed concrete is the most commonly used type of railway sleepers around world. Crushing is a common damage (under resultant compressive stress) in concrete sleepers, which is attributable to excessive flexural, shear, pre-stress and bond actions. Dynamic impact loading conditions are often the cause of failure in the concrete sleepers. However, accumulated damage due to cyclic loads can also cause concrete crushing. Most previous research has investigated the impact load characteristics and the ultimate limit states of prestressed concrete railway sleepers. There is a knowledge gap with respect to serviceability limit states and fatigue failure of prestressed concrete sleepers. This study presents new results of extensive numerical, analytical, and experimental investigations aimed at predicting fatigue lives under cyclic loads. A numerical study validated by 30 full-scale experimental tests is executed and extended to assess fatigue limit states, while theoretical fatigue analysis methods based on S-N curve and Miner linear cumulative damage are additionally introduced for benchmarking. This paper is the world's first to demonstrate a remaining fatigue life assessment for prestressed concrete sleepers and benchmark with the theoretical methods. Parametric studies are conducted to unprecedentedly illustrate influences of support conditions, dynamic load distribution, and track stiffnesses on the remaining fatigue lives of prestressed concrete sleepers. This paper highlights the rationales associated with the development of fatigue limit states. The insights will provide design flexibility and improve railway sleeper maintenance and inspection criteria.

Verification of Longitudinal Level Irregularity Suppression Effect at the Structural Boundary by Ballasted Ladder Track

The ladder sleeper, which is a type of longitudinal sleeper with long beams in the longitudinal direction of the rail, was developed for the maintenance-labor saving of ballast tracks. In this study, to quantify the load distribution performance of the ladder sleepers at the structural boundary, full-scale model tests were conducted to quantify the vibration transmission reduction effect of the ladder sleepers. Following that, numerical experiments were carried out using a three-dimensional numerical analysis model and it was revealed that the ladder sleeper can reduce the pressure on the sleeper bottom plane by approximately 70% when compared to conventional prestressed concrete sleepers. Furthermore, when laying the ladder sleeper at the structural boundary, it was shown that laying across the structural boundary may be more effective in reducing the pressure on the sleeper bottom plane than laying it in front of the structural boundary. Finally, ladder sleepers were installed on the commercial line and long-term measurements of the longitudinal level irregularity verified the effect of suppressing the longitudinal level irregularity of the ballasted ladder track.

Green approach on ternary blended pre stressed cement concrete railway sleepers

Conventional Railway concrete sleepers are manufactured using steel pre-stressed strands upto pre-determined stress level surrounded by well compacted controlled concrete. The concrete used in manufacturing of railway sleepers is made up of 53 grade ordinary Portland cement with natural aggregates. Though, experiments have been conducted worldwide with various unorthodoxical constituent materials, the standardization of such non-conventional materials used for concrete sleeper manufacturing on Indian Railways (IR) is yet to be established. The pretensioned prestressed concrete (PSC) sleepers for Broad Gauge (BG) should pass the specified acceptance criteria T 39-85 of 2011 as per the Indian Railway Standard specification issued by Research Design Standard Organisation (RDSO).Abundantly available industrial wastes, such as Fly ash and other supplementary cementitious materials viz., ground granulated blast furnace slag (GGBFS), metakaoline (MK), silica fume (SF) have been found, through experimental investigations which improves some of the characteristic strengths of concrete. Utilising these materials in railway sleepers manufacturing process contributes carbon foot print (CFP) mitigation on one hand, the growing concerns of waste disposal and management are also addressed concurrently. The findings of current experimental studies indicate, the PSC sleeper manufactured with ternary blended concrete (TBC) of different percentage level of replacement of cement along with partial replacement of natural coarse aggregate, exhibit good strength characteristics. These sleeper specimens qualify the specified standard bending test (SBT) for sleepers namely moment of resistance (MR), whereas failing moment of failure (MF) at failure loads at rail seats criteria only.The experimental findings hold promise to conduct further studies with lesser percentage levels of sintered fly ash coarse aggregate i.e., standalone 40% in the current study. From application stand point, the manufactured TBC- PSC can be used in loop lines, berthing tracks and non-passenger freight-oriented lines, major shunting yards.

Investigation on Prestressed Concrete Sleeper (PCS) Subjected to Dynamic Loading on Site and Experimental Works.

The purpose of the research was to study the condition of prestressed monoblock concrete sleeper (PMCS) under dynamic loading experimentally and through site investigation. From this research, the value of deflection base on acceleration of concrete sleepers have been obtained. This study showed the possible correlation and relation of the PCS deflection located under a railway track. This research includes experimentation process which includes experimental investigations for dynamic loading of prestressed concrete sleepers (PCS) were examined in terms of its capability to accommodate their own design capacity and the relationships between load and displacement happened within the concrete sleeper. This study will help the railway authorities to understand and take any maintenance action to their rail infrastructure. From experimental test, the highest deflection on KTMB and EPMI rail seat section is 1.35 mm and 1.04 mm respectively. From site investigation at KM20.75, the highest deflection occured is 5.993 mm which is lower compared to the highest deflection at KM26.25 with the value of 7.06 mm.

Structural Displacement of Prestressed Concrete Sleepers Subjected to Six Coaches Commuter Load at Pinang Tunggal and Kobah

Nowadays, train is one of an effective transportation in Malaysia. Commuter started the operation at Central Region had extended the operation at Northern Region in 2015.Since the volume of passengers were increasing every year, it caused railway track need to be maintenance frequently due to the displacement of concrete sleeper on railway track. According KTMB representative, the displacement happened depend on the soil condition. However, this study figured out the structural displacement concrete sleeper under different of soil condition. A site investigation had been carried out along railway track from Butterworth to Alor Setar. In this study had selected Pinang Tunggal the subsoil condition silty sand in category which displacement 7.40mm and Kobah the subsoil condition under soft clay, the displacement 0.15mm accordingly. The tools that had been used in this site investigation such as vibrator machine and piezometer. The captured records transferred to software called as Dewesoft to measure the displacement of concrete sleeper. From the result had been plotted on the graph showed sandy silt had shown the highest displacement compared with the soil condition soft clay. Therefore, the roof cause of displacement of concrete sleeper at railway track may cause the water table in the subsoil. This study would assist the authority to plan the maintenance on railway track.

Crack Propagation Assessment of Time-Dependent Concrete Degradation of Prestressed Concrete Sleepers

As prestressed concrete sleepers are continuously exposed to various environmental and loading conditions, it is increasingly crucial to analyse their current and future serviceability performance. In practice, the main cause of cracking in prestressed concrete sleepers is usually induced by impact loads. The most heavily influenced sections are the midspan and rail-seat area of sleepers. This paper investigates the effects of time-dependent concrete strength degradation on the capacity of prestressed concrete sleepers. The factors affecting concrete strength degradation are analysed in order to evaluate the crack behaviour of prestressed concrete sleepers. A finite element modelling approach is developed for prestressed concrete sleepers, which is used to assess the effects of structural behaviour in railway sleepers. The sleeper model has been calibrated and validated. This research firstly discusses time-dependent behaviour using load–crack length responses. It is shown that various cracking modes cause an overall increase in the maximum cracking length as prestressed concrete sleepers age. This paper demonstrates that initial cracking loads and ultimate crack lengths have significant change in first 20 years. After 40 years of service life, the crack resistance of prestressed concrete sleepers becomes very weak which is only 61.32% of the new sleeper. In long term, the initial cracking load keeps reducing, and the crack propagation rate becomes sharp. The presented methodology and results can greatly assist in decision-making for the repair or replacement of prestressed concrete sleepers and aid in the design of new prestressed concrete sleepers considering their future performance.