Concrete Railway Sleepers Research Articles

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.

A review of agro-potential waste as a constituent in railway sleepers

Historically, concrete was used exclusively for building construction. Concrete has recently found application in the railway business, notably in the construction of concrete railway sleepers. Concrete is made up of three primary ingredients: fine aggregates, coarse aggregates, and cement. To enhance the qualities of concrete, research was conducted on the possibility of substituting wastes from other industries for the ingredients of concrete. With agriculture being one of Malaysia's main industries, ranking third in terms of national economic activity, it demonstrated the potential for using agricultural wastes as ingredients of concrete manufacturing (fine aggregate, coarse aggregate, and cement). While the characteristics of agricultural waste-derived concrete have improved, research on their use as concrete railway sleepers remains uncommon. As such, this article will examine the feasibility of incorporating agricultural waste into concrete for the manufacturing of concrete railway sleepers.

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.

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.

Comparison of new LCR and ordinary prestressed concrete railway sleepers with LUR tests

Rail operations today have become more difficult due to increasing operating speeds and decreasing maintenance times. New developed, laminated carbon fiber reinforced polyurethane (L-CFRPU) reinforced concrete railway sleepers (LCR) have the potential to show longer service life in this demanding condition. In this study, a large number of specimens with various reinforcement variations were produced, and improved incremental loading–unloading-reloading (LUR) tests and common one-stage static loading (direct loading) tests were performed. Sleeper deformations, first crack formation loads, and permanent crack width measurements were also recorded during the tests. It is revealed that there are significant differences in peak load capacity, modulus of elasticity, and maximum deformation values between the results of the direct-loading tests and the LUR tests. According to the results, the new LCR sleepers have met the static capacity requirements of standards and also show fewer vertical plastic deformations, which are very important for high-speed railways. Among the samples, sleepers with L-CFRPU surface sanded, and with more spread of L-CFRPU in the concrete section showed better performance than the other sleepers.

Analysis of Fault Conditions in the Production of Prestressed Concrete Sleepers

Industries demand that their products are high quality with the least number of defects due to the rapid improvement in manufacturing technology. Quality is a critical criterion for evaluation in manufacturing firms. The production of a final product that can meet customer requirements is essential in a sustainable supply chain system to reduce costs, increase productivity and provide high-quality products. The aim of the study is to identify the root cause of defects emerging in the production process of prestressed railway concrete sleepers. Ishikawa diagram and Pareto analysis were used to identify the root cause. The results showed that the cause of the faulty concrete sleeper is the breaking of the bolts, which are supplied by the external provider. Since the supplier refused to accept the complaint, chemical analysis and measuring of hardness and microhardness of bolts were realized. It showed that the hardness of the bolts does not achieve the values, which should be achieved after the declared heat-treatment. As a corrective action, the input control of bolts hardness was proposed as well as establishing the team cooperating with the supplier to improve the heat treatment process, which will be the objective of further study.

Behaviour of new LCR and ordinary prestressed concrete railway sleepers under repeated impact loads

Rail operations today have become more difficult due to increasing operating speeds and uninterrupted working conditions. Prestressed railway sleepers especially are susceptible to high-frequency dynamic loads from trains and receive significant damage from these loads. Laminated carbon fiber reinforced polyurethane (L-CFRPU) reinforced concrete railway sleeper models (LCR concrete sleepers), which can be produced more economically and practically than prestressed railway sleepers have higher damping and resonance resistance capabilities. In this study, behaviour of railway sleeper under repeated impact loads was investigated and LCR and ordinary prestressed concrete sleepers were compared. According to the results, new LCR concrete sleepers have higher resistance to repeated impact load and show higher residual strength. In addition, these new concrete sleepers are expected to be beneficial in extending the service life of the railway components, reducing maintenance needs, and reducing harmful effects on the environment.

The Sound Absorption Coefficient of Railway Concrete Sleepers Containing Palm Oil Fuel Ash (POFA) As a Cement Replacement Material

Major noise and vibration during train operation can cause disturbance to the surrounding. One of the methods to reduce this disturbance are by installing concrete sleepers. The use of railway concrete sleepers may be a high potential to reduce the noise and vibration. To produce concrete sleepers cement usage will be used with greater volume. Approximately 100 million tons of Palm Oil Fuel Ash (POFA) was disposed to the landfill currently. POFA contains high silica content and porous particles which indicated its pozzolanic properties and sound absorption characteristics. Therefore, this study was to determine the sound absorption coefficient of railway concrete sleepers containing POFA as a cement replacement material. Concrete sleepers with a strength grade of 55 and a w/c ratio of 0.35 were prepared in this study. Three design mixes with 0% (control), 20%, and 40% of POFA tested by using an impedance tube test at 28 days of curing age. The results show, the sound absorption coefficient and noise reduction coefficient increases as the percentage of POFA increases. The best performance was obtained by concrete sleepers containing 40% of POFA, with a recorded sound absorption coefficient of 0.10 for low frequency and 0.44 for high frequency. Meanwhile, the noise reduction coefficient recorded was 0.33, which reduce 32% of noise compared to OPC.

Numerical studies to evaluate crack propagation behaviour of prestressed concrete railway sleepers

The prestressed concrete sleeper is a primary type of sleeper for railway systems around the world. Compared with wooden and composite sleepers, concrete sleepers are of good elasticity and sufficient longitudinal and lateral resistance to ensure the stability of the track. As the railway system is developing to a heavier load and higher speed system, the cracking of concrete sleepers under dynamic load and long-term service is becoming more and more critical. It is essential to evaluate the crack behaviour of prestressed concrete sleepers. In this paper, three-dimensional FEM models have been established using Abaqus based on the brittle cracking model. After the validation by experimental results, the numerical research is performed to evaluate the crack propagation behaviours of prestressed concrete sleepers with different concrete compressive strength, different prestressing force magnitudes, and different loading rates. The results reveal that the cracking resistance of a concrete sleeper turns enhanced by improving the compressive strength of concrete and the initial prestressing force of tendons. It is also observed that the cracking becomes more progressive as the loading rate increases.

Comparison of prestressed concrete railway sleepers and new LCR concrete sleepers with experimental modal analysis

Rail operations today have become more difficult due to increasing operating speeds and decreasing maintenance times. Today’s higher frequency train loads are more detrimental, and prestressed railway sleepers especially are susceptible to these dynamic loads. Laminated carbon fiber reinforced polyurethane (L-CFRPU) reinforced concrete railway sleeper models (LCR concrete sleepers) have the potential to exhibit higher damping and resonance resistance more economically and practically. In this study, experimental modal analysis was performed on a large number of samples produced to understand the damping characteristics of sleepers. According to the results, new LCR concrete sleepers have extremely higher damping ratios of over 50% and are expected to be beneficial in extending the service life of the railway components, reducing maintenance needs and harmful effects on the environment.

Incremental LUR tests of new LCR concrete railway sleepers

Today, the early deformation of sleepers has, directly and indirectly, raised railway maintenance expenditures. On the other hand, several types of fiber reinforced polymer (FRP) products are widely used as a new effective method to prevent corrosion and fatigue problems of reinforced concrete elements. In this context, carbon fiber reinforced polymer (CFRP) products have priority over other FRP types to ensure the high capacity design of railway sleepers. Moreover, it will not be necessary to apply the pre-stressing method according to the experiments. Thanks to the practical production method without pre-stressing, many raw materials, labor, and energy savings are gained. Laminated form carbon fiber reinforced polyurethanes (L-CFRPU) are generally used today for earthquake strengthening and rehabilitation of reinforced concrete or steel structures. The use of L-CFRPU products for preliminary reinforcement in concrete railway sleepers has not been experimentally researched, yet. In this study, newly designed L-CFRPU reinforced (LCR) concrete sleepers were tested with EN 13230 incremental LUR (loading–unloading-reloading) tests, and the test results were compared with widely used concrete sleepers and calculated limit state design load for UIC railway lines. According to test results, newly produced sleepers show higher enough design load capacities and offering a longer service life.

A comparative review on American, European and Chinese standard for railway concrete sleeper

This article discusses the similarities and differences of American, European and Chinese standard for railway concrete sleeper. As an integral part of railway structure, concrete sleeper which is widely used in railway engineering plays an important role in the stability of the railway structure. To ensure the quality of concrete sleeper, different regions stipulate standard for concrete sleeper on the basis of technology development and geographical environment. A comparative review on concrete sleeper standard from America, China and Europe in terms of requirements on cement, aggregate, reinforcement, manufacturing and concrete properties has been conducted. The review shows that all of three regions have similar requirement on cement in terms of compressive strength and SO3 content. The aggregate requirement for both American and Chinese standard specifies the upper (D) and lower (d) limits of sieve size while the European standard which provides more flexible requirement specifying only the ratio D/d. Both of European standard EN 13230-1 and American standard AREMA CHAPTER 30 focus more on prestressing reinforcement including wire, strand and bar, while the Chinese standard GBT 37330 has more specific requirement for manufacturing process of concrete sleeper on the basis of steel reinforcement. The value of compressive strength of concrete stipulated by GBT 37330 is the highest. This paper could provide clear understanding of the production requirements of concrete sleeper in America, China and Europe which can be used as guide for further concrete sleeper development in the future.

Structural response of monoblock railway concrete sleepers and fastening systems subject to coupling vertical and lateral loads: A numerical study

Monoblock prestressed concrete sleepers are the most dominant type of sleepers in ballasted railway tracks. As such, it is important to provide optimized designs to the concrete sleepers and the associated fastening systems to ameliorate railway safety and to save both capital and maintenance funds. Therefore, a three-dimensional finite element railway model was created and verified. The response of both concrete sleepers and fastening components to coupling vertical and lateral loading was quantified. Such loading form typically occurs at horizontal railway sections causing damage to the railway track components. The influences of the sleeper spacing, elastic modulus of the rail pad, and friction coefficient at the contact surfaces of the rail and sleeper with the rail pad under varied lateral loadings were investigated. The interaction influence between parameters was thoroughly discussed. Among the studied parameters, the finite element model outcomes showed that the elastic modulus of the rail pad and the coefficient of friction are the most critical parameters with respect to the lateral load path and the local response of concrete sleeper and fastening system, especially at high lateral loadings. By using a relatively soft rail pad (elastic modulus = 100 MPa), the concrete material remained below the compressive and tensile fatigue limits even under high lateral loadings provided that the coefficient of friction remains limited to 0.3. By contrast, for a given lateral to vertical loading ratio, a continuous increase in the developed stresses of the concrete material and rail pad was detected as the elastic modulus changed from 100 MPa to 2000 MPa and the coefficient of friction increased from 0.3 to 0.9. The influence of sleeper spacing on the behaviour of railway tracks is only tangible on the distribution of the vertical wheel load. Lastly, the peak stress magnitudes of the ballast bed could be increased by 50% as the lateral to vertical loading ratio reached 0.6 compared to the case where the lateral load is absent. The experience gained from this article would help to formulate specific recommendations to improve the design of concrete sleepers, fastening systems, and ballast bed.

Time-dependent behaviours of railway prestressed concrete sleepers in a track system

The main functions of railway sleepers are: (i) to safely transfer loads from wheel axles to foundation; (ii) to secure both rails ensuring correct track gauge at all time; and, (iii) to restrain movements of rails to control longitudinal creeps. In reality, railway industry can experience costly problems of railseat twists and tight gauges, for instance, due to time-dependent actions and poor workmanship. These problems prevent trains to navigate over tracks safely, effectively and quietly. They require additional, expensive maintenance activities much more frequently over time such as rail renewal, rail reprofiling/grinding, rail pad replacement, curve lubrication adjustment, etc. On this ground, it is very important to maintain the geometry and topological/dimensional stability of railway sleepers. The long-term geometric performance of sleepers can be significantly influenced by time-dependent actions and behaviours. The creep and shrinkage in prestressed concrete sleepers result in internal actions that is led to geometric deformation, which change the rail gauge and influence the safety and reliability of track components. Time-dependent behaviours also lead to increased complex internal stresses, which can cause cracking on prestressed concrete railway sleepers. The cracks stemming from creep and shrinkage can be observed in real life, at a certain time after construction, along the sleepers and near the fasteners such as anchorage, bolt holes, and web openings. In this study, unprecedented experimental and numerical investigations are conducted to evaluate time-dependent behaviours of full-scale prestressed concrete sleepers. An empirical calculation method is also introduced and the empirical results are compared with both experimental and numerical results. Insights into creep and shrinkage effects are highlighted in order to essentially aid predictive and preventative track maintenance, supporting the effective and efficient decision making of both (i) engineers and manufacturers and (ii) infrastructure managers and owners.

Modal and harmonic response analysis of new CFRP laminate reinforced concrete railway sleepers

Nowadays high-cost sleeper applications are becoming indispensable because of railway operation conditions and high frequency train loads. For the protection of sleepers and other railway components, “non-prestressed” sleepers have the potential to reduce railway maintenance costs and exhibit a longer service life compared to their prestressed competitors. But the disadvantage of this process is steel reinforcement defects due to corrosion and fatigue. A new type of sleeper with non-pre-stressing process with non-corroding carbon fiber reinforced polymer (CFRP) laminate reinforcements can overcome these disadvantages. Rail seat static positive moment tests have been performed for these new types of sleepers before and it was determined that they can provide the desired static strength parameters even in high speed train lines. In this study, modal and harmonic response analysis has been performed and the results compared with prestressed sleepers with equivalent concrete cross-section dimensions. According to the results this new sleeper model has higher damping advantages and is expected to be beneficial in extending the service life of the railway components, reducing maintenance needs, and harmful effects on the environment.

A three-dimensional finite element analysis of concrete sleepers and fastening systems subjected to coupling vertical and lateral loads

At horizontal railway curves, the rail is typically a subject to both vertical and lateral wheel loads. The underestimated influence of lateral load at such locations in the design process could compromise the structural integrity of the whole railway track system. Rail-seat deterioration and damage of fastening system components are two possible failure mechanisms associated with high lateral loadings that could lead to safety concerns and costly maintenance activities. It is, therefore, of high importance to analyse the track response including concrete sleepers and fastening systems to coupling vertical and lateral loadings. For such end, a three-dimensional finite element railway model was created and subjected to a variety of lateral to vertical loading ratios. Of other elastic fastening systems, the Skl-style (W14) fastening system, which is currently of high demand, was accounted for as a result of it has been barely researched. The finite element model was rigorously verified with the experimental works and classical theories found in the previous knowledge. The finite element outputs could investigate the complex structural behaviour of railway concrete sleepers and fastening systems and the transmission mechanism of the lateral loading through the track system. The findings indicated that the concrete-rail pad interface is significantly influenced by the high lateral to vertical loading ratio which produces localized contact area of high compressive stress; however, the influence of lateral load on the produced stresses of both tension clamps and angled guide plates is minimal. Further, lateral sliding at concrete-rail pad interface was apparent even at low lateral load, increasing the possibility of wear deterioration of the contacting surfaces. Lastly, the gap between the field angled guide plate and the rail base is a critical parameter that influences the lateral load path and failure mechanisms. The outcomes of this research would lead to better insight into the influences of lateral wheel load more clearly and thus contribute to improvements in the current design practices of concrete sleepers and fastening systems at demanding locations.

Effect of steel fiber content on structural and electrical properties of ultra high performance concrete (UHPC) sleepers

This experimental research investigates the structural and electrical responses of ultra-high performance concrete (UHPC) railway sleepers with three different levels of steel fiber content. The UHPC sleepers used in this research were fabricated using a conventional concrete sleeper manufacturing process including the post-tensioning method. They were then evaluated via static bending tests at the rail-seat section and via electrical insulation performance tests. Test results indicate that UHPC sleepers with all three levels of steel fiber content sufficiently meet international requirements. The results from the first cracking load and the load when a crack width becomes 0.05 mm indicate that an amount of steel fiber greater than 1% is required to effectively control early-stage crack development in UHPC sleepers. In addition, the relationship between fiber volume fraction and normalized strength highlights that the material characteristics of UHPC, especially its tensile capacities, correlate strongly with the structural behavior of UHPC sleepers.