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• A new damage quantification based on peridynamic theory has been established. • This new approach tackles the complex crack initiation plane, which is unsolved. • The new technique has been validated by experimental case studies. • The predictions exhibit very good agreements with experiments. • Crack propagation patterns can be accurately predicted using this new approach. This paper proposes a novel approach to evaluate the damage in Peridynamic simulations to identify the crack initiation and propagation, based on the physical meaning of the bond network. The most commonly used criterion to assess the damage in Peridynamic simulations is the nodal damage value, a ratio of the broken bonds to number of unbroken bonds for each point. There is no consensus on the magnitude of nodal damage value within the literature. In most cases, the assessment is conducted visually via damage contours. Rarely, researchers calculate nodal damage value by counting the bonds that pass through a crack plane and must be broken to initiate a crack. Despite being widely-used, the application of nodal damage value is questionable since it neglects the likelihood of broken bonds that are irrelevant to a crack. In other words, the applied value of the nodal damage value might not give the information about the crack whether it emerges or not. This paper shows the influence of the nodal damage value on damage assessments and compares the proposed method with the nodal damage value in different scenarios. The results exhibit that the proposed method is robust, effective, and more importantly provides a single outcome for Peridynamic simulations. [ABSTRACT FROM AUTHOR]

The main functions of the sleepers in ballasted tracks include transferring loads, securing rail gauge and maintaining railway track geometry. Sleepers can be manufactured using timber, concrete, steel or other engineered materials, but concrete is most commonly used around the world. There are a number of researches on the impact load characteristics and the ultimate load carrying capacity of prestressed concrete sleepers, but research on the fatigue life of prestressed concrete sleepers is very limited. A prestressed concrete sleeper's fatigue damage is mainly due to the repeated loads derived from dynamic wheel-rail interactions, especially when either wheel or rail irregularity is present. Fatigue failure is thus a time-dependent limited state where a concrete sleeper accumulates damage to a failure point over its service life. Concrete sleepers could usually suffer from the dynamic fatigue loading spectra throughout their whole lives, and simultaneously, both static and dynamic load-carrying capacities of concrete sleepers degrades over time. Therefore, a fatigue life assessment is an important and complicated research frontier. Field loading conditions, material time-dependent and dynamic properties, and the dynamic bending moments of prestressed concrete sleepers are quantitatively analysed in this study. This paper also presents an updated fatigue life assessment method for concrete sleepers, and provides a case study based on actual field loading conditions and the time-dependent behaviour of materials. The new insights obtained from this study will improve concrete sleeper maintenance and inspection criteria, and provide a new reference for a rational dynamic design principle of railway concrete sleepers and bearers. • Life cycle modelling of railway sleepers is firstly presented. • Track loading annals are analysed from the fields. • Fatigue life assessment model of railway concrete sleepers has been validated with experimental data. • It is the first time that the endurance of railway sleepers is identified using the actual annual loading conditions. • Time-dependent effects play a significant role on the remaining fatigue life of concrete sleepers. [ABSTRACT FROM AUTHOR]

Each day tens of turnout-related derailment occur across the world. Not only is the prediction of them quite complex and difficult, but this also requires a comprehensive range of applications, and managing a well-designed geographic information system. With the advent of Geographic Information Systems (GIS), and computers-aided solutions, the last two decades have witnessed considerable advances in the field of derailment prediction. Mathematical models with many assumptions and simulations based on fixed algorithms were also introduced to estimate derailment rates. While the former requires a costly investment of time and energy to try and find the most fitting mathematical solution, the latter is sometimes a high hurdle for analysists since the availability and accessibility of geospatial data are limited, in general. As train safety and risk analysis rely on accurate assessment of derailment likelihood, a guide for transportation research is needed to show how each technique can approximate the number of observed derailments. In this study, a new stochastic mathematical prediction model has been established on the basis of a hierarchical Bayesian model (HBM), which can better address unique exposure indicators in segmented large-scale regions. Integration of multiple specialized packages, namely, MATLAB for image processing, R for statistical analysis, and ArcGIS for displaying and manipulating geospatial data, are adopted to unleash complex solutions that will practically benefit the rail industry and transportation researchers. • All estimates seem to be incapable of calculating an estimate for a low number of derailments. • the assumptions seldomly yield a precise estimate of the derailment rates under any uncertainty • Some assumptions which relied on turnout counts, are observed to deviate from the observations • the assumptions regarding turnout counts are a weak spot even when being generated mathematically on the basis of a concrete belief. [ABSTRACT FROM AUTHOR]

Railway turnouts or so-called 'switches and crossings' are complex systems by nature of design and construction. Railway turnouts are used to change direction of trains from one to another. They require high-quality construction and maintenance, in order to minimise rapid degradation and component failures that could result in train derailments. Due to the complexity of railway turnouts, the efficiency and effectiveness of maintenance can be improved by integrating existing practice by Building Information Modelling (BIM). This research establishes and analyses the world's first 6D BIM for life cycle management of a railway turnout system. The BIM (Level 3) has integrated 6-dimensions of field data information based on Revit-2018 and Navisworks-2018 platforms. The digital twins of a railway turnout in 3D embrace time schedule, costs and sustainability across the whole life cycle. The use of BIM for railway turnout systems has the potential to improve the overall information flow of the turnout planning and design, manufacturing pre-assembly and logistic, construction and installation, operation and management and demolition, thereby achieving better project performance and quality. Based on integrated information of railway turnout system, the 6D BIM has the ability to assess on economic, management and sustainability, and achieve a balance among them. This is the word first to demonstrate that BIM can fully deliver its essential benefits by information sharing, easing technical communication, improving design quality, reducing of design errors, accelerating implementation, speeding up work, shortening construction duration, reducing construction costs, enhancing carbon efficiency, supporting project management, and providing its owners with higher operational efficiency over the railway turnout system life-cycle. The results reveal that embodied material emission is the main contributor towards carbon footprint, especially produced during the manufacturing stage. The reconstruction stage contributes the most expensive phase of life cycle. The insight will significantly benefit the co-value creation among engineers, project managers, technicians, and senior management team. • Digital twin or BIM (Level 3) of railway switches and crossings is established. • It is the first to highlight sustainability-based life cycle management of railway turnout systems. • The life cycle analyses consider both cost and environmental impacts using field data, design and case studies. • The outcomes highlight best practices for sustainable and cleaner solutions for life cycle management of turnout systems. • The insight will benefit the co-value creation among engineers, project managers, technicians, and senior management team. [ABSTRACT FROM AUTHOR]

Abstract According to a large number of end-of-life rolling stocks were left over landfill, appropriate waste management should start by properly understanding the components of rolling stocks to determine their remaining potential. This paper evaluates efficient and feasible approaches to recovering and recycling wasted rolling stocks. The emphasis is placed on three broad train types, consisting of freight train, passenger train, and High-Speed Rail (HSR). In this article, all compositions of the three types of rolling stock are studied, with the results of the recyclability and recoverability rates being used to inform their productive treatment at the end-of-life. The distinctive point of this research is an analysis of compositions, materials, and the percentage of value adopted from the end-of-life rolling stocks. With respect to find out the recyclability (R cyc) and recoverability (R cov) rates on end-of-life rolling stock, the equations are adopted from ISO 22,628:2002 document to estimate the feasibility and suitability of each component on the rolling stock for taking advantage from unused parts. By comparing the R cyc and R cov rates among three types of rolling stock at the end-of-life stage, the highest value of R cyc showed at 92.8% from freight train where the highest value of R cov represented at 12.5% from HSR. It was found that those rates relate to the main components on rolling stock, which contained diversely characteristic to be reusable, recyclable or recoverable materials. Finally, the two key recommendations for further design on rolling stocks are provided regarding the proper selection of materials and the method to enhance efficiency of recycling and recovering process. [ABSTRACT FROM AUTHOR]

Highlights • 3D FEMs have been developed and rigorously validated. • Full-scale tests prestressed concrete sleepers with holes and web openings are conducted. • It is the word first to identify damages and failure modes of the sleepers with holes and web openings. • Novel insights into the behaviours of the sleepers with holes and web openings exposed to impact loading are highlighted. • Two advanced material modelling techniques are exercised and benchmarked. • Brittle cracking model provides better damage predictions than Damage Plasticity Model. • Holes and web openings induce shear failure of the sleepers under impact loading. Abstract Prestressed concrete sleepers are essential to the structural integrity of railway track structures, redistributing wheel loads from the rails to underlying ballast bed while securing rail gauges for safe train traffics. In practice, drilled holes or web openings are usually generated ad hoc in sleepers to enable signalling equipment and cables at a construction site. These holes and web openings could however affect the structural integrity of sleepers, especially when they are exposed to impact loading. In fact, statistically, 15–25% of dynamic loading conditions are of transience and high-intensity by the nature of wheel-rail interaction over irregularities. This study is thus the world first to rigorously investigate the impact behaviours of railway sleepers with hole and web openings, which is critical to railway safety and reliability. In this study, three-dimensional finite element modelling using ABAQUS Explicit is used to comprehensively design and analyse the behaviour of prestressed concrete sleepers with various types of holes and web openings upon impact loading. Two different modelling techniques including concrete damaged plasticity model and brittle cracking model are also exercised to aid in this study. The results obtained show that the brittle cracking model provides better damage results as it can illustrate crack propagation very well until reaching the failure mode under impact loading. The findings illustrate a pathway to use brittle cracking model instead of concrete damaged plasticity model for dynamic impact analysis. Moreover, the outcome of this study will provide a better and new insight into the influences of holes and web openings on sleepers' failure modes under impact loading so that appropriate guidance can be proposed to rail and track engineers in order to generate holes and web openings ad hoc in prestressed concrete sleepers without compromising their structural performance. [ABSTRACT FROM AUTHOR]

Each year, there can be three to six millions of service train axles running over an open plain track. In fact, these trains could impose a variety of dynamic loading conditions depending on the wheel and rail maintenance levels. Inevitably, the risk of high-intensity dynamic loading conditions by wheel-rail interactions due to wheel or rail irregularity cannot be disregarded. Imperfection of rail tracks could lead directly to the exceedance of permissible stress of a track component and later amplify rapid track deterioration rates causing cracking in sleepers and failure of track substructure. Practical railway track irregularities can be typically classified into short wave length (high frequency) and long wave length (low frequency) defects, of which previous researchers had studied each in isolation. This paper is the first to study the influence on railway track inspection and maintenance priorities caused by the coupling of wave lengths between dipped rail joint and differential track settlements. To study the dynamic coupling effects, P1 and P2 forces are evaluated at the track irregularity together with rail/sleeper contact force, ballast pressure and bending moments of sleepers using dynamic multi-body simulation approach. It is found that some patterns of coupling irregularity could cause a significant reduction in dynamic impact factors whilst some are associated with an increase in the wheel/rail impact force. The insight has then been integrated to establish track performance indicators that are paramount for prioritising track inspection and maintenance. [ABSTRACT FROM AUTHOR]

To enhance rail operational flexibility, railway turnouts are special track systems, which are designed to divert or change a train from a particular direction or a particular track onto other directions or other tracks. In reality, the railway turnout is commonly built on complex track geometry and graded terrain, which makes it one of the most unique and critical railway infrastructures. The physical constraints and complexity of turnout systems cause various risks and uncertainty in rail operations. This study critically analyses emerging geotechnical risks on turnout systems considering all aspects that can potentially result in impaired reliability, availability, maintainability and safety (RAMS) of the turnout systems. The annual derailment incidents have been evaluated to identify emerging risk factors. Not only do these incidents yield operational downtime and financial losses, but they also give rise to the casualties and sometimes the loss of lives across the world. In particular, the climate change risks on geotechnical aspects of the turnout systems have been highlighted. This paper thus presents how turnout components work as a system, the diversity of emerging risks considering natural hazards and global warming potential to the system. In addition, it highlights the climate change adaptation strategies for georisk mitigation of the railway turnout systems in order to improve RAMS of the railway turnouts and crossings, focusing on trackbed failures on the systems. [ABSTRACT FROM AUTHOR]

Modern railway tracks require electrification to power the trains and signaling systems to detect near real-time location of trains on railway networks. Such systems require the rail to carry and return the residual electricity back to substation, while enable signals to transfer within a track circuit. This track circuit requires rail joints to divide and insulate each loop of the circuit. Such the rail joints often generate impact transient dynamics to track systems. This paper presents the filed investigation into the vibration attenuation characteristic of under sleeper pads (USPs), which are the component installed under the concrete sleepers generally to improve railway track resilience. The field trial is aimed at mitigating rail joint impacts in a heavy haul track under mixed traffics. ‘Big Data’, obtained from both the track inspection vehicle and the sensors installed on tracks, demonstrate that track surface quality (top) of the section was improved after the track reconstruction. Fourier analysis results showed that the track surface (or vertical deviation) tends to deform at larger displacement amplitude and resonates at a lower wavelength of track roughness. Interestingly, the operational pass-by vibration measurements show that the USPs has resulted in an increased vibration of both rail and sleeper with USPs. Although the studies have found that the sleepers with USPs tend to have lesser flexures, the field data also confirms that a railway track with USPs could experience a large amplitude vibration, especially when excited by a high-frequency impact force. These dynamic behaviours imply that the use of soft to moderate USP could potentially induce dilation of ballast whilst the use of hard USP may reduce sleeper-ballast friction. In the end, these could then weaken lateral track stability over time. [ABSTRACT FROM AUTHOR]

Disruption in a schedule (or plan) can be managed but not all factors are visible. A study of disruption management is performed specifically to minimize the differences between the expected and actual context of execution. The purpose of this paper is twofold: first to offer an introduction and deliver a concept of disruption management in the transportation sector. Second, we aim to understand challenges in a rescheduling strategy to manage disruption in the area of resource scheduling. Real world applications from airline to railway services are used as a basis of the investigation. A discussion on the future development of disruption management with a focus on rail track inspection is provided in the final part of this paper. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Track inspection is purposely performed to recover tracks from defects and damage and eliminate potential safety hazards. It is scheduled through an exhaustive process that usually integrates many disciplines such as optimization, statistics, risk management, etc. Spending so much of a monetary and an emotional investment in an original schedule (referred to as master schedule hereafter) that the scheduler wants to deliver might be a good excuse not to develop a solid ‘Plan B’. Plan B here refers to scheduler responses or a contingency plan when the master schedule does not go as expected. It is found that there is often low to moderate probability of a crisis occurring when a schedule is executed in a real environment. Nevertheless, its impact can leave transportation services to the mercy of the disruption as shown by the Christmas 2014 incident where a huge volume of passengers using King's Cross and Paddington services experienced both inconvenience and discomfort due to engineering delays and train disruption. Thus, this paper aims to discuss the potential of considering ‘Plan B’ or contingency plan if incidents arise that were not expected during track inspection schedule execution. Benefits, general guidelines and relevant strategies for creating a contingency plan are also discussed. We highlight the rationale to support the claim that an original schedule of track inspection jobs should be adapted to respond to a new context e.g. inspection vehicle machine breakdown, new inspection requests, man-made hazards, terrorist attack, extreme weather, climate change, etc. It is however proposed to develop an appropriate set of performance measure that is used to guide rescheduling in track inspection due to financial, equipment inventory, manpower, safety regulations, time and spatial constraints. [ABSTRACT FROM AUTHOR]

As an essential feature to enable rail operational flexibility, railway turnouts are special track systems used to divert a train from a particular direction or a particular track onto other directions or other tracks. Railway turnout is constructed on a complex geometry and grade, which makes it one of the most critical railway infrastructures. These characteristics pose various risks in rail operations. A considerable number of derailment incidents have occurred every year. Not only do these incidents yield operational downtime and financial losses, but they also give rise to the casualties and sometimes the loss of lives across the world. One of fundamental reasons is that railway industry barely pays attention to risk elements on railway turnouts. This paper thus presents how turnout components work as a system, the diversity of emerging risks considering natural hazards and global warming potential to the system. Additionally, in order to perform a well-designed quantitative-based risk analysis method for appropriate risk management of railway turnouts and crossings, focusing on aging, degradation and signalling faults on the systems, the research develops a number of new ideas. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• 3D IWP minimal surface structures have been modeled and validated. • 3D printed IWP specimens have been established and experimentally tested. • Structural performance of the cellular unit has been assessed thoroughly. • Failure modes have been identified for the first time. • Discrete element modeling has been established to model the damage and failure of the structure. The Schoen I-graph-wrapped package (IWP) structures are recognized as one of the best promising cellular structures because of their high specific mechanical properties and damping ratios. The axially-loaded behaviors are critical for structural safety and durability in engineering fields. In order to extend the application of IWP structures into civil engineering, this paper investigated the axially-loaded behaviors, including compressive strength, force distribution, load-deflection pattern, energy absorption and cracking pattern, of the main and secondary Skeletal-IWP structures. Firstly, a novel method for simplifying triply periodic minimal surfaces (TPMSs) has been put forward. Then the main and secondary Skeletal-IWP units are fabricated using stereolithography technology and tested. The discrete element method (DEM) is adopted, for the first time, to simulate the axially-loaded behaviors of IWP structures with different unit cell arrangements after the validation by robust experimental results. The results reveal that the secondary Skeletal-IWP structures outperform the main Skeletal-IWP structures in compressive strength. When the unit arrangement changes from single unit to 7 × 7 × 7, the compressive strength of the main and secondary Skeletal-IWP structures increases from 9 MPa to 13.4 MPa and 9.2 MPa to 14.4 MPa, respectively. The main type shows a "X"-shaped cracking pattern, and the secondary shows a "X"-shaped cracking pattern. [Display omitted] [ABSTRACT FROM AUTHOR]

Australian railway networks suffer a large fluctuation of extreme heats each year due to their wide variety of geographical conditions. Depending on climatic, cloud and radiation conditions, an ambient temperature of 20 °C could induce an equivalent thermal load absorption of track components as much as 30 °C to 35 °C or even more. As such, relatively high turnover of timber sleepers (crossties in a plain track), bearers (skeleton ties in a turnout), and transoms (bridge cross beams) can often be observed due to their unstable deformation and rapid deterioration. This paper investigates an application for the replacement of ageing timber transoms mounted on existing railway bridges using fibre reinforced foamed urethane (FFU) transom beams, which are proven to provide environmental, safety and financial benefits. Clear benefits of the FFU material are the maintainability and constructability, especially for existing railway bridges. In this study, numerical simulations using finite element package ABAQUS have been carried out to illustrate the effect of thermal loads on the structural behaviour of a railway transom bridge. The model was developed using a case study of an actual railway bridge in Kiama, Australia and it has been validated by field data measurements. It is found that nonlinear structural behaviour of the bridge components exists at highly elevated temperatures. The better insight into the thermal load responses will lead to safer and more reliable rail stress adjustment practice, preventing rail misalignment or buckling. [ABSTRACT FROM AUTHOR]

Prestressed concrete sleepers (or railroad ties) are structural members that distribute the wheel loads from the rails to the track support system. Over a period of time, the concrete sleepers age and deteriorate in addition to experiencing various types of static and dynamic loading conditions, which are attributable to train operations. Recent studies have established two main limit states for the design consideration of concrete sleepers: ultimate limit states under extreme impact and fatigue limit states under repeated probabilistic impact loads. It was noted that the prestress level has a significant role in maintaining the high endurance of the sleepers under low to moderate repeated impact loads. This experimental investigation was aimed at static and dynamic load rating of aged railway concrete sleepers after service. Fifteen sleepers were extracted from a heavy haul rail network for testing using experimental facilities at the University of Wollongong (UoW), Australia. The structural evaluation program included quasi-static bending tests, dynamic impact tests, and tests to establish the current level of prestress in the steel wires using the dynamic relaxation technique. Two of the sleepers were evaluated for the level of prestressing forces in accordance with Australian Standards. Through diagnostic tests, the results of quasi-static bending tests produced the in-track bending capacities of sleepers that can be combined with the moments and forces anticipated over the next ten years to predict performance of the sleepers on a heavy haul coal line. The dynamic tests simulating the ability of concrete sleepers to resist extreme loading events due to heavy impact loads demonstrated that the sleepers in-track are likely to be able to resist the planned increased traffic without catastrophic failure over the next decade. Final conclusions suggest that there should be a routine test program every five years to ascertain the load rating of clustered sleepers and their fastening system in the heavy haul track system. [ABSTRACT FROM AUTHOR]

• Nonlinear FE model of sleepers has been presented. • Full-scale experiments have been conducted for validation. • Crack propagations are monitored and presented. • It is the first time that crack propagations are predicted. • Prestress forces play a significant role on the crack propagation. 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. [ABSTRACT FROM AUTHOR]

• 3D FE model of interspersed tracks has been developed. • Vulnerability of interspersed tracks has been assessed. • This study is the first to assess the failure of interspersed tracks exposed to flood damage conditions. • The new insights will help track engineers to define operational restrictions in order to improve resilience capability of interspersed railway tracks. In traditional railway networks globally, timber sleepers have been widely adopted since the advent of railway systems. After a certain period of time, timbers tend to degrade and it becomes more and more difficult to seek cost-effective replacement hardwood sleepers. To provide a short-term solution, many rail infrastructure managers use an interspersing method of track maintenance. The interspersed sleeper of railway tracks, which is a spot replacement of old timber sleeper with concrete or composite counterparts, is often utilised as a temporary maintenance measure for secondary railway tracks such as low-traffic lines, yards, balloon loops or siding. Reportedly, the performance of railway lines including the interspersed tracks can quickly deteriorate when the tracks are exposed to heavy rains and floods. In many cases, ballast washaway can be often seen. This study is the world first to demonstrate the effects of ballast washaway on the vulnerability assessment of interspersed railway tracks using nonlinear finite element simulations, STRAND7. Two sets of moving point loads representing a bogie along the rails have been established to investigate the worst-case, potential actions for impaired performance of sleepers and differential settlements of the track. In this study, the emphasis is placed on the effects of ballast washaway on the maximum displacement of rails and the relative track geometries (i.e. top and twist). The maximum bending actions causing the failures of the track components are also investigated. The new insights will help track engineers develop appropriate climate change adaptation methods and policies for operations of interspersed railway tracks facing extreme rainfall and flooding conditions. [ABSTRACT FROM AUTHOR]

Abstract: On railway track structures, dynamic impact loads with very high magnitude but short duration are often caused by wheel or rail abnormalities such as flat wheels and dipped rails. The possibility of the large impact loading to cause an extreme failure to an in situ concrete sleeper could be very low about once or twice in the design life cycle. However, to the current knowledge, the behaviour of the in situ prestressed concrete sleepers under the ultimate impact loading has not yet been comprehended, resulting in the design deficiency. A high-capacity drop-weight impact testing machine was thus constructed at the University of Wollongong, in order to evaluate impulsive resistance of in situ prestressed concrete sleepers under impact loads. This paper describes the detail of the high-capacity impact testing machine, as well as the instrumentation, the calibration, and the analysis of failure mode, crack propagation, flexural toughness, and energy absorption mechanisms with respect to railway prestressed concrete sleepers. The impact tests were carried out using the prestressed concrete sleepers manufactured in Australia. An in situ track test bed was simulated in laboratory and calibrated against the frequency response functions obtained from the experimental modal analysis. The experiments using the high-capacity impact testing machine to investigate the impact energy transfer mechanism of the prestressed concrete sleepers are highlighted. [Copyright &y& Elsevier]

Abstract: Prestressed concrete sleepers (or railroad ties) are among the major and the most common structural components of railway track structures. Their main duty is to carry and transfer the wheel loads from the rails to the ground. In general, railway tracks suffer with the extreme loading conditions, which are attributable to the train operations with either wheel or rail abnormalities such as flat wheels, dipped rails, etc. These loads are of very high magnitude but short duration, as well as they are of low-possibility occurrence during the design life of the prestressed concrete sleepers. In spite of the most common use of the prestressed concrete sleepers in railway tracks, their impact responses and behaviours are not deeply appreciated nor taken into the design consideration. This experimental investigation was aimed at understanding the progressive dynamic behaviours of prestressed concrete sleepers in railway track structures under repeated impact loading, in order to form the state of the art of limit states design concept for prestressed concrete sleepers. A high-capacity drop weight impact testing machine was constructed at the University of Wollongong as to achieve the purpose. Series of repeated impact tests for the in-situ prestressed concrete sleepers were carried out, ranging from a low drop height to the ultimate drop height where the ultimate failure occurred. The accumulative impact damage and crack propagation are highlighted in this paper. The effects of track environment including soft and hard tracks together with the relationship between the resultant bending moment of prestressed concrete sleepers and the applied impact force as a design guideline were also presented. [Copyright &y& Elsevier]

Abstract: Extreme loading conditions on railway tracks may include dynamic impact loads with very high magnitude but short duration. These loading conditions are caused by wheel or rail abnormalities such as flat wheels, dipped rails, etc. This type of loading is very rare and could occur once or twice in their design life span. A high-capacity drop weight impact testing machine was constructed at the University of Wollongong, in order to evaluate the ultimate capacity of prestressed concrete sleepers under impact loads. This paper presents the experimental investigations to evaluate failure modes, flexural toughness, and energy absorption mechanisms for railway prestressed concrete sleepers under static and impact loadings. Energy absorption capacity of the prestressed concrete sleepers was evaluated to determine the amount of energy required to fail the sleeper under impact load. Static and impact tests were carried out on the Australian-manufactured prestressed concrete sleepers. The residual capacity of the prestressed concrete sleepers after impact has also been highlighted. Also, this paper presents a simplified approach to predict ultimate moment capacity of railway prestressed concrete sleepers under impact loading. Modified compression field theory has been employed in the flexural resistance prediction, based on a generalized sectional analysis software, Response-2000. Effects of dynamic strain and loading rates were taken into account for predicting the impact capacity. The test results exhibit very good correlation with the predicted results by the modified compression field theory. [Copyright &y& Elsevier]

Abstract: Railway sleepers in a track system are usually utilised to transfer any loading from the rails to the ground support. A wide range of loading conditions has been observed but the critical loading condition is the wheel impact force, which is often due to the wheel or rail irregularities. The railway industry has been aware of a high potential that an out-of-round, single-sided wheel defect may occur and cause cracking in the railway concrete sleepers. This paper presents the dynamic effects on the railway concrete sleeper in a track system due to a single wheel impact. In this study, the railway concrete sleeper is modeled using the beam on elastic foundation theory. The dynamic finite model makes use of the elements coupling with shear and bending deformations to represent the concrete sleeper, and features the use of the tensionless elastic support as the nature of ballast. The parametric investigations focus on the influences of both magnitude and duration of the transient loading. Using the robust finite element software STRAND7, the finite element model of the railway concrete sleeper was previously established and validated against experimental data by the authors. The numerical simulations present the dynamic flexural moment magnification factor of the railway concrete sleeper under the asymmetrical wheel load patterns. [Copyright &y& Elsevier]

Abstract: In many railway networks, the dynamic loads on the track can be detected and they are highly diverse. In most cases, the dynamic wheel load could be treated as a quasi-static load whereas it is later employed in flexural response and failure analysis of railway structures, according to the current design standard: AS1085. This paper presents the effect of a large asymmetrical wheel load on the flexural response and failure criteria of the concrete sleepers in railway track systems. The finite element model updating of the concrete sleeper was earlier established and verified against experimental dynamic characteristics by the authors. Using a finite element package STRAND7, the nonlinear finite element model is capable of simulating the tensionless ballast support whereas the supporting boundary condition provides resistance to only compression. The numerical investigations are carried out to provide guiding criteria to railway track engineers for crack and failure analysis of the railway concrete sleeper subjected to a large quasi-static asymmetrical wheel burden. The normalized quasi-static responses are demonstrated in order to illustrate the critical effect of the large wheel unbalance on the flexural responses of the concrete sleeper in railway track system. [Copyright &y& Elsevier]

• Nonlinear FEM of a prestressed concrete sleeper is presented. • Field measurements are used for validations of the time-dependent simulations. • Creep and shrinkage properties are taken fully into account. • It is the first time that the time-dependent effects are considered throughout the models. • Flexural stress resultants of the prestressed concrete sleepers are underestimated by design. 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. [ABSTRACT FROM AUTHOR]

This paper unprecedentedly benchmarks the environmental and economic impacts of notable High-speed rail (HSR) networks. The goals are to (i) point out the environmental impacts from the HSR networks and (ii) evaluate the whole life cycle cost of HSR systems. The emphasis of this study is placed on five HSR networks from five countries to depict the effectiveness of sustainable transport policies in each particular country. Both life cycle assessment (LCA) and life cycle cost (LCC) models are adopted for a new critical framework capable of benchmarking the lifecycle sustainability of HSR networks. The new findings exhibit that CRC's system is the leader in energy-saving, who consumes only 67.55 GJ/km yearly, and emits lowest CO 2 at an amount of 77,532.32 tCO 2 /km annually. These impressive results are stemmed from key enabling policies related to eco-friendly rolling stock design, sustainable construction, and green energy grids. With respect to the LCC analysis, the SCNF network takes advantage in the economy of scale and unleashes the lowest cost among other networks. It estimates that the SNCF network spends approximately 1,990,599.51 £/km annually at a % discount rate. The implications of these finding are discussed that the initial project has a high chance to be successful on economic than the late project due to an influence of the time value of money. • Detailed LCA and LCC frameworks for HSR networks in relation to environmental and economic perspectives. • An analysis of five notable HSR networks selected from different geographic regions, technologies, services and relevant conditions. • Long-term life cycle is evaluated by NPV analysis. The life cycles for rolling stock and HSR track are estimated at 35 and 70 years, respectively. • A sensitivity analysis for LCC is provided using the MCS. It is an advantage for rail authorities to control financial plan on uncertainty situations. [ABSTRACT FROM AUTHOR]

• Nonlinear 3D track-ballast interaction model is firstly presented. • Field measurements are used for the validation of the model. • It is the first time that the balllast degradation effects are considered in track bucklings. • Ballast fouling play a significant role in undermining lateral track stability. • Lateral track resistance can reduce by half when fully fouled ballast incurs. Presently, railway track buckling, caused by extreme heat, is a serious issue that causes a huge loss of assets in railway systems. The increase in rail temperature can induce a compression force in the continuous welded rail (CWR) and this may cause track buckling when the compression force reaches the buckling strength. It is important to ensure the lateral stability of railway track in order to tackle the extreme temperature. However, in fact, railway track can be progressively degraded over time resulting in poorer track stability. This includes the larger lateral track misalignment and component deteriorations. This unprecedented study highlights 3D Finite Element Modelling (FEM) of ballasted railway tracks subjected to temperature change considering different ballast fouling conditions. The buckling analysis of ballasted railway tracks considering ballast fouling conditions has been investigated previously. This paper adopts the lateral resistance obtained from the previous single sleeper (tie) push test simulations to the lateral spring model. The influences of the boundary conditions and rail misalignment on the buckling temperature are also investigated. The results clearly show that the ballast fouling may increase the likelihood of track buckling even if the fouled ballast is accumulated at the bottom of the ballast layer. More importantly, the allowable temperature can be reduced up to 50% when the ballast is completely fouled. The results can be used to predict the buckling temperature and to inspect the conditions of ballast. The new findings highlight the buckling phenomena of interspersed railway tracks and help improve the inspection regime of ballast conditions especially in summer to encounter the extreme heat. [ABSTRACT FROM AUTHOR]

To minimize the maintenance frequency as well as the environmental impact caused by the growing number of railway materials reaching the end of their lives, appropriate sustainable management is inevitable prior to either turning them into wastes or leaving them in landfill sites. This paper presents the recent developments of Fibre-reinforced Foamed Urethane (FFU) sleepers installed in the railway turnouts. It determines the recycling and recovering processes of this infrastructure system. The results of recyclability (R cyc) and recoverability (R cov) rates for the railway turnout system are subject to assumptions associated with data which are taken from relevant sources (e.g. UNIFE). The result presents a value of 92.23% and 93.50%, respectively. A sensitivity analysis demonstrates that Mass Recovery Factor (MRF) has superior effect on R cyc and R cov values compared to Energy Recovery Factor (ERF). In addition, this study evaluates environmental life-cycle impacts based on the calculation of carbon emissions and energy consumption over 75 year's lifespan. Comparison of the life-cycle sensitivity for the whole railway turnout system is conducted between FFU sleepers and concrete sleepers. The results show that concrete sleeper emitted almost the same carbon emission as the FFU material, but with much more maintenance and replacement frequency over the mentioned lifespan. • Sustainability analysis of composite materials for railway switches and crossings is established. • It is the world's first to highlight life cycle cost and sustainability of railway turnout systems. • Life cycle evaluations have been carried out using designs, case studies, and field data. • The outcomes highlight best practices for sustainable and cleaner solutions for composite materials. • The insight will vastly improve recyclability and sustainability of composite materials for railway turnouts. [ABSTRACT FROM AUTHOR]

• Three-dimensional FE models have been developed and validated by full-scale tests of prestressed concrete sleepers. • It is the first to identify the impact responses of railway concrete sleepers with under sleeper pads exposed to impact loading. • Increase in insertion losses and decrease of contact pressures from impulse moderation have been highlighted. • It is the first to reveal the effectiveness of USP in impact load response of railway sleepers. • Insights will help track engineers to make decision on the design and usage of USP. Exposed to operational uncertainties, the investment in railway infrastructure is increasing to improve track resilience, to mitigate long-term consequences, to prolong the track service life, and to reduce unplanned maintenance costs and carbon footprint. Under sleeper pads (USPs) have been widely used in several countries as a resilient component placed underneath concrete sleepers. However, it is well-known that, with any imperfection of either wheel or rail, railway tracks usually are incited by impact loading conditions. Accordingly, the application of USPs to mitigate the detrimental impact load consequences on track structure is unprecedentedly highlighted in this paper. Despite the common uses of USPs in various countries in Europe, the dynamic behaviour of the USPs under high-intensity impact loading conditions has not been fully investigated. Note that not only does this study focus on serviceability condition but it also instigates an extreme condition, which can occur when there are coupled effects of short and long wavelength defects (e.g. dipped rail joint coupled with track settlement, switches and crossings, etc.). This paper thus establishes a 3D finite element model of prestressed concrete sleepers with USPs, using LS-Dyna. This study has confirmed field measurement data that the sleepers with USPs tend to have lesser flexures, contact force and impact energy. However, this study is the world's first to reveal that the vibration of sleeper with USPs could be amplified by the large amplitude impact force, which can be induced especially when excited by a high-speed train travelling over short-pitch rail defects, rail joints, coupled defects or crossings. It is also noteworthy that a very stiff pad with a bedding modulus of 1 N/mm3 can be alternatively used as USPs as recommended by the results obtained. Based on both numerical and field measurement results, it demonstrates that the applications of USPs should be very carefully considered since the USPs could trade off the desired benefits by aggravating dynamic behaviours of sleepers with USPs. The new insights will help track engineers to make appropriate decision on the design and usage of USP. [ABSTRACT FROM AUTHOR]

• Interspersed track systems are simulated using nonlinear finite element method. • Ballast model using tensionless stiffness has been adopted to reflect the real-world physical behaviour. • 600 nonlinear simulations varying various time-dependent parameters have been carried out. • Dynamic uplifts are the source of rapid track deterioration over life cycle. • More routine ballast tamping is recommended to resolve any track geometry problem. Presently, timber-sleepered tracks are still being adopted in railway networks transporting goods and passengers. However, the deterioration of timber sleepers is evident after years of service due to natural decay; and it is difficult to seek cost-effective hardwood sleepers to replace the aging sleepers. An impermanent "interspersed" approach is an alternative method used to substitute rotten timbers with concrete sleepers. Although the interspersed tracks offer a cost-effective short-term solution for certain track classes, there are some drawbacks to this practice, since the interspersed track has inconsistent stiffness problems, and the different track decay rate can cause uneven settlement and foundation failure, which can lead to significant track deterioration over time. The emphasis of this study is placed on the long-term behaviour of interspersed track components under repeated train loading. Interspersed track models in three-dimensional space have been developed and validated using a finite element method. The effects of deteriorated railway components (timber, rail pads, ballast) are taken into account to examine the dynamic performance of the interspersed tracks under moving train loads. This study will help rail track engineers better understand the time-dependent behaviour of interspersed tracks, enable a truly predictive track maintenance and improve the reliability of infrastructure asset maintenance and life cycle management. [ABSTRACT FROM AUTHOR]

• Gyroid, IWP and Primitive TPMS structures are fabricated using stereolithography technology. • 3D printed TPMS structures are robustly tested under axial vibrations. • It is the first time that natural frequencies of complex porous composite structures structures has been benchmarked. • Damping properties of complex porous composite structures have been identified for the first time. • Nonlinear dynamic phenomena of TPMS based composite structures have been found. • New insights into nonlinear dynamics of composite structures are the precursor to engineering applications. Natural frequency, damping ratio and dynamic stiffness are fundamental to the performance of structures subjected to dynamic loads. Triply Periodic Minimal Surface (TPMS) composite structures, celebrated for their superior energy absorption capacity and specific strength, represent some of the most promising meta -structures. However, their dynamic properties are yet to be fully understood, thereby hindering their practical applications within civil engineering domains. Damping properties, crucial to vibration reduction, remain particularly elusive; previous studies have not successfully established a connection between these properties and the force excitation amplitude in TPMS structures. This study aims to compare the damping properties of different TPMS structures and to investigate their potential for adoption within civil engineering fields. Three types of TPMSs, including Schoen I-graph-wrapped package surface (IWP), Schwarz primitive (Primitive) and Schoen Gyroid (Gyroid), have been adopted to design solid and sheetal TPMS composite structures with identical relative density (50%) to compare their damping properties under varying excitation amplitudes. These TPMS structures are manufactured from photosensitive resin (UV resin) using stereolithography 3D printing technology. Owing to the lack of previous research into the damping properties and dynamic stiffness of TPMS structures as support structures, we have conducted single-freedom modal tests to determine the modal parameters, including natural frequency and damping ratios. Our novel results indicate that the natural frequency and damping ratio of the TPMS structures vary with the excitation amplitude. Additionally, the dynamic stiffness of TPMS structures reveals a similar decreasing trend to frequency when load amplitude escalates. As the excitation amplitude increases, the TPMS structures demonstrate softening and are capable of offering a higher vibration damping coefficient. Notably, the SS-Gyroid structure exhibits higher stiffness and damping ratio compared to other TPMS structures. These fresh insights pave the way for the integration of 3D printed smart TPMS structures within civil engineering, particularly for vibration reduction and efficient material usage. A judicious TPMS structure design can provide relatively high stiffness and damping ratio without excessive material use. [ABSTRACT FROM AUTHOR]

Fatigue fractures can be frequently observed in welded joints in orthotropic steel decks (OSDs) after just a few decades of operation, which become the major deterioration mechanism deterring the serviceability of OSDs. In this paper, a novel dynamic Bayesian network (DBN) model has been established for the fatigue reliability analysis of OSDs at system-level. The exact inference algorithm is applied in the DBN model with discrete variables. Special modifications have been made on the existing algorithm to improve the computational efficiency in dealing with the deck system consisting of a considerable number of joints. Using the DBN model, the fatigue reliability of welded joints can be predicted and updated with the inspection and monitoring results at system-level. At the same time, a framework is established for the system-level reliability considering the fatigue fracture of rib-to-deck (RD) joints, the dominant cracking pattern affecting the serviceability of OSDs. For illustration, a typical OSD bridge in China has been selected to carry out a case study. To derive the stress spectrum required by the DBN model, the stochastic traffic model is employed, and the influence-based Monte Carlo simulations have been carried out. As a result, the fatigue reliability can be predicted at both component- and system-levels. Meanwhile, the observation of the traffic and the inspection result has been fused into the DBN model to update the deteriorating state of the deck system. Besides, the effect of enhancement and maintenance has been highlighted, including the enhancement in fatigue strength at the construction stage, and the repair and traffic control during the operation stage. • A novel dynamic Bayesian network (DBN) model is established for the fatigue reliability of orthotropic steel decks (OSDs). • Special modifications are made on the inference algorithm of the DBN model to improve computational efficiency. • A framework is established for the system-level fatigue reliability of OSDs based on serviceability. • The DBN model is illustrated with a case study, including prediction, information-based fusion and evidence-based updating. • The effects of enhancement and maintenance are investigated using the DBN model. [ABSTRACT FROM AUTHOR]

This unprecedented study aims to demonstrate the potential to locate crack damage and severity in full-scale railway prestressed concrete sleepers. The dynamic mode shape curvature squares method has been utilised. This approach adopts structural deflection shapes extracted from experimental modal analysis using an impact excitation. The railway concrete sleepers are exposed to the first crack and 1.5 times above the first-crack loads using experimental setup in accordance with the British Standard (for benchmarking purpose). It is found that the first cracking of the sleepers has caused non-significant stiffness reduction of the structural component evidenced from the fact that the natural frequency shifts are only few percent and no visible differences in deflection mode shapes are observed. In addition, the mode shape curvature alone cannot indicate the crack establishment in the railway sleepers. However, a relatively sparse wireframe for deflection shapes enable the plausible density of sensor grids that can be further analysed for damage detection. In this paper, the curvature square approach has been developed to quantify and locate the damage in the railway sleepers. The standardized damage index distributions and subsequent thresholding with different levels of confidence of damage localization have been firstly developed to enhance the accuracy of crack localization. It is found that accurate locations of cracks mostly in the mid span of the sleepers can be reasonably detected in accordance with the actual crack measurements from the experimental data. The novel insight into this approach can enhance the new development of on-board technology for railway sleeper crack detection using operational modal signals. • Dynamic mode shapes of cracked railway concrete sleepers are extracted. • Mode shape curvature square method is used to identify cracks in railway sleepers. • Polynomial smoothing of mode shape curvature eliminates the need for baseline data. • Initial and further cracks in railway concrete sleepers are accurately detected. [ABSTRACT FROM AUTHOR]

• The generation of porous structures is facilitated by adopting two triply minimal surfaces. • A simulation method for porous concrete structures is proposed using a non-linear soft-contact model based on the Discrete Element Method. • For the first time, the comparative analysis of the bearing capacities of Primitive and Gyroid concrete structures under simultaneous torsion and compression loads is presented. • An investigation into the cracking patterns of Primitive and Gyroid structures under diverse loading conditions is conducted. Bioinspired lightweight Primitive and Gyroid structures are two well-known TPMS (triply periodic minimal surface) cellular structures. These structures have been shown to possess high specific strength and energy absorption capacity, and thus hold great promise for a range of prefabricated civil engineering applications. As a result, concrete cellular TPMS structures have garnered the attention of researchers. However, prior to this study, no investigation has been carried out on the mechanical properties and failure patterns of concrete Primitive and Gyroid structures under coupled compressive and torsional loads. This lack of knowledge on the behaviour of these structures can lead to safety concerns in construction projects. To better understand the mechanical behaviour of Primitive and Gyroid structures under combined compression and torsion, the discrete element method (DEM) is adopted to simulate the TPMS structures. Both linear contact and nonlinear softbond contact models are utilized to simulate the brittle mechanical behaviour of concrete material. After validating the DEM parameters using published experimental data, the DEM models are subjected to coupled compressive and torsional loads to study their compressive and torsional bearing capacity and cracking patterns. The results indicate that the Primitive based structures outperform the Gyroid based structures in terms of both compressive and torsional resistance. The study is the world's first to reveal that a compressive load enhances the ultimate torsional bearing capacity of TPMS structures, but a torsional load reduces their compressive bearing capacity. Additionally, the loading conditions have little impact on the cracking patterns of the four TPMS structures. [ABSTRACT FROM AUTHOR]

Railway transportation, comprising freight and passenger transport, is the lifeblood of the social economy of a country today, especially for developing countries. Despite over a decade of operations, derailment accidents are among the most frequent accidents for railway transportation and may cause fatally or severe injury to passengers, loss of property and damage to the railway track. Hence, this study focuses predominantly on the structural response and performance evaluation of composite rail track slabs through 3D finite element analysis using ABAQUS. The response and performance of composite track slab subjected to derailment actions has been observed. Material strain-rate properties and impact loads have been introduced to the numerical simulation in order to investigate impact behaviours of composite slabs subjected to derailment loading in explicit dynamic analysis. Based on obtained results, it was found that 45 km/h in the direction of gravity is the limit impact velocity for the designed composite rail track slab. The outcome of this study will improve the design standard and calculation of composite rail track slabs subjected to derailment actions. [ABSTRACT FROM AUTHOR]

• 3D FE model coupled with multi-body simulation has been developed. • Vulnerability of railway turnout systems has been assessed. • This study is the first to assess train-turnout interactions exposed to flood damage conditions. • The new insights will help track engineers to define operational restrictions building resilience capability. Track twists used in modern railways indicate the warpage of a particular track plane to identify track quality. In some cases, a twist is intentionally introduced on tracks to facilitate motions in curves. Nevertheless, twists can exceed above certain thresholds resulting in twist faults, which impose direct risk to safety and a potential cause for derailments. Twist faults are commonly observed in ballasted tracks, which consists of crushed rock particles and have low endurance to resist against dynamic track forces. In general, the deterioration in ballast structure progresses slowly. However, in reality, there are some catalysts such as extreme events that can speed up the deterioration of the ballast bed. Extreme events have rare occurrences but a high potential to damage structures and environment in a short duration. Even though the term 'rare' is still used to define extreme events, a consensus among the environmental scientists on the increased frequency of extreme events could be found in open literatures. In this study, the impacts of flooding, one of the most common extreme events, on the dynamic phenomena of a turnout structure is investigated in terms of dynamic twists. The emphasis is placed on railway turnouts of which the asymmetrical structure is expected to amplify twist responses. A 3-dimensional finite element method (FEM) model has been developed and many hypothetical scenarios ranging from various materials to vehicle speeds have been tested in virtual environments. It should be noted that the developed model is the modified version of a previously validated model and therefore, validation of the model is done by a comparison with the parent model. This study is the world's first to demonstrate that the dynamic performance of composite and plastic bearers is relatively poor in comparison to concrete bearers when considering dynamic twist phenomena. Our new results also exhibit that partially damaged turnout structures in the case of flooding is the most critical and vulnerable situation, which could result in detrimental train derailments. This vulnerability cannot practically be inspected by naked and untrained eyes. On this ground, when exposed to flooding conditions, it is recommended to halt any railway operations over vulnerable switches and crossings, and to avoid the approach of 'reach the station first' in emergency cases. [ABSTRACT FROM AUTHOR]

• A novel PINNFD method is proposed to solve the multi-frequency elastodynamics issue. • The proposed PINNFD allows the solution of elastodynamics in the frequency domain. • Fourier features for all frequencies can be embedded in the proposed PINNFD model. • The performance of the traditional PINN and the proposed PINNFD were compared. • The potential of the proposed PINNFD for engineering applications is validated. Despite the fact that physics-informed neural networks (PINN) have been developed rapidly in recent years, their inherent spectral bias makes it difficult to approximate multi-frequency target functions such as the solutions to elastodynamics problems. To address this challenge, this paper proposes a new PINN frequency domain (PINNFD) method on the basis of frequency domain inputs. Fourier features for all frequencies can thus be constructed and embedded in the model, which provides essential support for the PINNFD method to accurately approximate multi-frequency target functions. To validate the effectiveness of the proposed PINNFD method, the proposed method and the traditional method are applied to solve the elastodynamics problem in infinite media under various dynamic point loads, including single-frequency harmonic load, multi-frequency harmonic load, and multi-frequency random load. The results show that although the PINN with embedded Fourier features is able to achieve the simulation of elastodynamics problems under harmonic loads, it fails to solve the problems under multi-frequency random loads. Whereas the proposed PINNFD method achieves better results in all cases of loading conditions, which demonstrates the advancement of the proposed method in solving multi-frequency problems in engineering applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Coupling train and 3D track slab interaction model is firstly presented and validated in a full scale. • Dynamic material properties and field measurements are taken fully into account. • It is the first time that the strain rate effects are considered throughout the train-track interaction models. • Dynamic material properties play a significant role when the train travels above 70 km/h. • Flexural stress of the track slab is considerably underestimated unless considering dynamic material properties. Slab tracks or so-called ballastless tracks have been widely adopted for highspeed rail networks. Material properties of slab track components have significant influences on the serviceability performance of both high-speed trains and the slab tracks. In reality, the stiffness of rail pads and moduli of elasticity of concrete and CA mortar are quite different when they are determined by using either quasi-static or dynamic loading tests. Based on a critical literature review, most previous studies adopted some static material properties despite the fact that the actual loads from high-speed trains onto slab tracks are dynamic excitations. In addition, some studies simply adopted the dynamic stiffness of rail pads whilst ignored the dynamic effect on modulus of elasticity in their simulations. This study is thus the world's first to highlighting the influence of the dynamic material properties on the train-track vibration interactions. A nonlinear 3D coupled vehicle-slab track model has been developed based on the multi-body simulation principle and finite element method using LS-DYNA. This model has been validated by comparing its results with full-scale field test data together with other simulation results. A very good agreement among the results has been found. The magnification effect on the dynamic modulus of elasticity under dynamic train loads has been determined firstly. The influences of material properties on the serviceability performance of the vehicle, the wheel-rail contact force, the vibration responses of the rail, concrete slab, and CA mortar have then been evaluated. The deviation coefficients of vibration responses of the vehicle and track under three types of material properties have been determined to emphasise the influences of the dynamic stiffness and modulus of elasticity. The novel insight stemmed from this study provides a new reference and state-of-the-art recommendation for adopting suitable and realistic material properties of high-speed slab tracks in practice. [ABSTRACT FROM AUTHOR]

High-speed trains can induce significant amplification of dynamic responses of components in railway tracks especially when the train travels at the so-called 'critical speed'. Based on a critical literature review, most previous studies with respect to train-track-soil interactions have merely been focused on the simplified natural ground vibrations. Accordingly, there exists no investigation into the influences of piles on the ground responses despite the fact that the pile-reinforced ground improvement has been widely adopted in soft soil regions for high-speed railway with slab track systems. In order to highlight the influences of piles on ground vibrations, a 3D fully coupled train-track-soil model has been developed based on the multi-body simulation principle, finite element theory, and perfectly matched layers method using LS-DYNA, in which the dynamic material properties of slab tracks have been adopted. This model has been validated by comparing its results of ground vibrations and train-track interactions with field-test results. This is thus the world's first to investigate the critical speeds of slab-track railway with natural and pile-reinforced ground improvement. The dynamic displacements, vibration velocities, and dynamic stresses of soils with natural and pile-reinforced grounds have then been evaluated under normal and critical train speeds. The accelerations of car body and dynamic impact factors with the increasingly train speed have also been presented. The piles influences on the wave propagations in the soils have been highlighted. The novel insight from this study provides a new and better understanding of ground vibrations in high-speed railway systems using slab tracks in practice. [ABSTRACT FROM AUTHOR]

Abstract Prestressed concrete sleepers are the most commonly used type of railway sleepers in ballasted railway track. They have a strong influence on track performance, track stiffness and railway safety. Reportedly in many railway lines (especially in heavy-rail networks), many prestressed concrete sleepers have failed due to rail seat abrasion (RSA). RSA is a wear deterioration of the concrete underneath the rail that results in various problems such as loss of fastening toe load, gauge variation, improper rail cant, and eventually loss of rail fastening. In addition, the RSA will directly decrease the capacity of worn concrete sleepers. However, to the best of authors' knowledge, there were very few studies that quantitatively examined the effects of RSA on the structural capacity of the prestressed concrete sleepers. In this paper, a numerical study is executed to evaluate the load-carrying capacity of a prestressed concrete sleeper using LS-DYNA. The nonlinear model was validated firstly based on both theoretical analyses and experimental results in accordance with Australian Standard. Using the validated finite element model, the influences of different wear depth of RSA are investigated; and different compression strength and tensile strength of concrete and the prestress losses are highlighted. The outcomes of this study lead to better insight into the influences of RSA more clearly and improve track maintenance and inspection criteria. Highlights • Nonlinear FEM for railway sleeper failures is developed. • Three dimensional finite element models have been established using material nonlinearities. • Experimental and design data have been used to rigorously validate the model results. • Failure modes of sleepers with abrasion are comprehensively identified. • Structural capacity of the sleepers depends largely on the abrasion types and severity. • The new insight into failure mechanisms will help track engineers to better monitor and maintain sleepers in ballasted track environments. [ABSTRACT FROM AUTHOR]

Highlights • Acoustic emissions are recorded from full-scale tests of prestressed concrete sleepers. • Non-significant peak frequencies of emissions are filtered using a modified universal threshold. • Maximum peak frequencies are assessed using emission counts and distribution centroid. • Peak frequency shifts are nearly linear with distance from the main emission source. Abstract A novel technique for acoustic emission-based condition monitoring of railway prestressed concrete sleepers under flexural loading is established. The evolution of peak frequency of emissions under increasing loads is studied using data from four emission sensors. It is found that the bulk of emitted peak frequencies are clustered in three bands - [150–300] kHz, [300–460] kHz and [500–800] kHz in all cases of full-scale sleepers tested. Only slight variations of band ranges are observed. A correspondence of acoustic emission counts to a particular peak frequency is established. Not all emissions are damage-induced – most of them have relatively small number of counts, suggesting that those are due to random noise. Thus, it is proposed to filter out the non-significant peak frequencies with the least number of counts by applying a universal threshold rule. The largest proportion of emission counts corresponds to mid-span of the sleepers. It is shown that other acoustic emission sources exhibit a nearly linear shift in maximum values of peak frequency with increasing distance from this largest concentration of acoustic emission events. This novel insight into condition-based acoustic emissions is critical to develop a suitable and efficient technique for monitoring safety-critical railway sleepers and bearers located in a discreet and remote area. It will truly enable preventative, predictive and condition-based track maintenance for railway industry, minimizing cost and environmental impacts. [ABSTRACT FROM AUTHOR]

Structural responses of longitudinally coupled slab tracks (LCSTs) under extreme heat waves (EHWs) and the adaptability of track reinforcement measures to cope with EHWs-related issues have been unprecedentedly investigated in this study. A novel finite element model (FEM) to assess nonlinear mechanical behaviours of LCSTs exposed to temperature rise has been established. The nonlinearities of material constitutional properties, interfacial behaviours and temperature distribution are taken into account, and the FEM has been fully validated by experimental data. This paper is the world's first to highlight nonlinear structural responses of LCSTs such as slab arching and interface failure under EHWs and under normal temperature rises (NTRs). More importantly, effectiveness of track reinforcement measures (such as post-installed anchors and interface adhesives) in mitigating track damage under EHWs are demonstrated to determine whether those measures are capable of making LCSTs adapt to EHWs. The new findings reveal that: (1) vertical buckling of LCST can be caused by atmospheric temperature rises; (2) the interface area between the mortar layer and the track slab adjacent to the joint with initial defect can fail under NTRs, while the interface delamination incurs under EHWs; (3) vertical displacements of track slabs under EHWs can be reduced by 97.3 % when post-installed anchors are introduced; and (4) the bond strength of interface adhesives should be larger than 0.02 MPa and 0.048 MPa to retain the vertical displacements within the threshold of level III interfacial gaps under NTRs and under EHWs, respectively. [ABSTRACT FROM AUTHOR]

• Wet condition can influence on FFU sleepers performance. • Two common screws used for FFU fastening system are studied. • Pulling out test is supported by DIC for crack opening and strains measurement. • Numerical modeling was developed to measure stress distribution on FFU specimens. • Wet condition may influence a lot on FFU sleeper fastening system performance. This paper studies the structural integrity of fastening systems used in fiber-reinforced foamed urethane (FFU) composite sleepers. 24 FFU specimens are studied with screw pull-out tests and digital image correlation (DIC) to investigate the effects of parameters such as wet conditions, the sleeper drilled hole diameter and the screw active length inside the sleeper. The pull-out test results reveal that a moisture content of 0.3% in FFU specimens can reduce the pull-out strength between the dry and water-absorbed specimens with 18 mm FFU hole and 80 mm screw active length in dry and wet states (18-AD &18-AW), 18 mm FFU hole and 90 mm screw active length in dry and wet states (18-BD & 18-BW), 20 mm FFU hole and 110 mm screw active length in dry and wet states (20-CD & 20-CW), and 20 mm FFU hole and 90 mm screw active length in dry and wet states (20-BD & 20-BW) by approximately 18%, 19%, 6% and 13%, respectively. Specimens with 20 cm holes have the highest pull-out loads of 71.9 kN and 68 kN in dry and water-absorbed states, respectively. When the active length of the screw decreases from 110 mm to 90 mm, the pulling strength decreases by approximately 14% and 16% in dry and water-absorbed states, respectively. Therefore, the experimental and FEM results show that a 20 mm FFU hole with a 110 mm active length and a 24 mm thick screw is the best option for an FFU sleeper fastening system, especially in wet conditions. [ABSTRACT FROM AUTHOR]

A number of composite railway sleeper technologies have been developed but their applications in rail tracks are still limited. This paper rigorously reviews the recent developments on composite sleepers and identifies the critical barriers to their widespread acceptance and applications. Currently the composite sleeper technologies that are available ranges from sleepers made with recycle plastic materials which contains short or no fibre to the sleepers that containing high volume of fibres. While recycled plastic sleepers are low cost, the major challenges of using this type of sleepers are their limited strength, stiffness and dynamic properties which in most cases, are incompatible with those of timber. On the other hand, the prohibitive cost of high fibre containing sleepers limit their widespread application. Moreover, limited knowledge on the historical long-term performance of these new and alternative materials restricts their application. Potential design approaches for overcoming the challenges in the utilisation and acceptance of composite sleeper technologies are also presented in this paper. [ABSTRACT FROM AUTHOR]

• Probabilistic crack growth model is established for RD joints with mixed failure modes. • Machine learning tool, Gaussian process regression, is used to boost the simulation. • Effect of mixed failure models is revealed on the fatigue behaviour of RD joints. • Uncertainty is quantified in failure model, fatigue life and crack growth of RD joints. Rib-to-deck (RD) welded joints in orthotropic steel decks (OSDs) of bridges demonstrates two major fatigue failure models, including the toe-to-deck (TTD) cracking and root-to-deck (RTD) cracking. Generally, the sole failure model is employed in the fatigue assessment of RD joints, causing a hot dispute on the dominant failure model. In this paper, the fatigue crack growth (FCG) in RD joints has been evaluated considering uncertainties and mixed failure models. A probabilistic fatigue crack growth (PFCG) model is at first established for the RD joint, in which two crack-like initial flaws are assumed at the weld toe and root of the RD joint. After that, the gaussian process regression is used to assist and boost the PFCG simulation. Then, the PFCG model is implemented on a typical OSD with the random traffic model. Finally, the result of the PFCG model is discussed in detail, including the failure model, fatigue reliability and life prediction, and crack size evolution. It is revealed that both the TTD and RTD cracking models have a notable contribution to fatigue failure and could not be ignored. More crucial, a remarkable reduction can be observed in the fatigue reliability of RD joints when considering mixed failure models. This study not only highlights the influence of mixed failure models on the fatigue performance of welded joints, but also provide an insight into the application of novel machine learning tools in solving the traditional structural issue. [ABSTRACT FROM AUTHOR]