Search

• 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]

• Schwarz Primitive structures are fabricated using stereolithography technology. • 3D printed metamaterials are robustly tested under axial load conditions. • It is the first time that nonlinear behaviours of complex porous composite metamaterials has been benchmarked. • The discrete element method is adopted to simulate the Schwarz Primitive metamaterials validated by experimental tests. • New insights into crack patterns of composite metamaterials are the precursor to engineering applications. This study delves into the axial responses of Schwarz Primitive (SP) structures. Emphasising on bearing capacity, force distribution, cracking phenomena, load-displacement curve and energy absorption. Discrete element method (DEM) is adopted to analyse the axial load-bearing behaviour and fracture mechanics of Main SP and Secondary SP structures under various unit cell configurations after validated by experimental tests. The results indicates that despite sharing the same 1/8th cell structure, the axially-loaded behaviours of the Main SP and Secondary SP structures are not identical, particularly in scenarios involving a large unit cell size and a small number of unit cells. The Main SP structures display an axial load-bearing behaviour that is largely unaffected by variations in the number of unit cells along the x and y axes, while Secondary SP structures show a more pronounced improvement in average strength and energy absorption capacity when the number of unit cells increases. Main SP structures offer superior axial load-bearing capabilities and energy absorption efficiency, which is a significant consideration for their application in scenarios demanding high structural integrity. This distinction underlines the importance of tailored design and selection of SP configurations based on specific engineering requirements. [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]

Abstract Since multiple failure events associated with derailments could not be identified and derailment probability could not be reached quantitatively by event tree and fault tree analysis for safety assessment in railway systems, applications of Bayesian network (BN) were introduced over the last few years. The applications were often aimed at understanding safety and reliability of railway systems through various basic principles and unique inference algorithms focusing on particular railway infrastructures. One of the most critical engineering infrastructure, railway turnouts (RTs) have been investigated and analysed critically in order to develop a new BN-based model with unique algorithm. This unprecedented study reveals the causal relations between primary causes and the subsystem failures, resulting in derailment, as a result of extreme weather-related conditions. In addition, the model, which is designed for rare events, has been proposed to identify the probability and underlying root cause of derailment. Consequently, it is expected that various weather-related causes of derailment at RTs, one such undesirable event, which can result, albeit rarely, damaging rolling stock, railway infrastructure and disrupting service, and having the potential to cause casualties and even loss of life, are identified to allow for smooth railway operation by rail industry itself. The insight into this weather-derailment will help the industry to better manage railway operation under climate uncertainty. [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]

At present, railway infrastructure experiences harsh environments and aggressive loading conditions from increased traffic and load demands. Ground borne vibration has become one of these environmental challenges. Overhead line equipment (OHLE) provides electric power to the train and is, for one or two tracks, normally supported by cantilever masts. A cantilever mast, which is made of H-section steel, is slender and has a poor dynamic behaviour by nature. It can be seen from the literature that ground borne vibrations cause annoyance to people in surrounding areas especially in buildings. Nonetheless, mast structures, which are located nearest and alongside the railway track, have not been fully studied in terms of their dynamic behaviour. This paper presents the effects of ground borne vibrations generated by high speed trains on cantilever masts and contact wire located alongside railway tracks. Ground borne vibration velocities at various train speeds, from 100 km/h to 300 km/h, are considered based on the consideration of semi-empirical models for predicting low frequency vibration on ground. A three-dimensional mast structure with varying soil stiffness is made using a finite element model. The displacement measured is located at the end of cantilever mast which is the position of contact wire. The construction tolerance of contact stagger is used as an allowable movement of contact wire in transverse direction. The results show that the effect of vibration velocity from train on the transverse direction of mast structure is greater than that on the longitudinal direction. Moreover, the results obtained indicate that the ground bourn vibrations caused by high speed train are not strong enough to cause damage to the contact wire. The outcome of this study will help engineers improve the design standard of cantilever mast considering the effect of ground borne vibration as preliminary parameter for construction tolerances. [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]

• This study stems from the critical review of more than 140 research articles available in open literatures. • It is the first to highlight the properties of recycled steel fibre with respect to cleaner applications. • Sustainability analysis of recycled steel fibre reinforced concrete is established. • The outcomes highlight best practices for sustainable and cleaner solutions using recycled steel fibres. • The insight will enable an innovative alternative to achieve net-zero infrastructures. Construction wastes have become one of critical issues in lifecycle asset management, slowing down the path towards net zero. Accordingly, the contribution of recycled materials in building design and construction is needed. In such a context, recycled steel fibres (RSF) from waste tires have been considered as an alternative to the industrial steel fibres(ISF). This paper presents a comprehensive and critical review on RSF use relatively to fibre properties, as well as the mechanical properties of RSF reinforced concrete. Both at wet and hardened state comparative analyses between ISF and RSF to improve compressive strength, splitting strength and flexural strength is performed. Moreover, based on the data of global warming potentials and prices, investigates the contribution of RSF towards sustainable development and economy in comparison with ISF. [ABSTRACT FROM AUTHOR]

There has been a considerable increase in derailment investigations, in particular at railway turnouts (RTs), as the majority of derailments lead to lengthy disruptions to the appropriate rail operation and catastrophic consequences, being potentially severely hazardous to human safety and health, as well as rail equipment. This paper investigates the impact of climates with different features across the US on the derailments to light up a scientific way for understanding importance of climatic impact. To achieve this, official derailment reports over the last five years are examined in detail. By means of geographic segmentation associated with spatial analysis, different exposure levels of various regions have been identified and implemented into a Bayesian hierarchical model using samples by the M–H algorithm. As a result, the paper reaches interesting scientific findings of climate behaviour on turnout-related component failures resulting in derailments. The findings show extreme climate patterns impact considerably the component failures of rail turnouts. Therefore, it is indicated that turnout-related failure estimates on a large-scale region with extreme cold and hot zones could be investigated when the suggested methodology of this paper is considered. • The climate effects causing derailments at turnouts have been identified and classified. • A novel methodology dealing with the climate effects on derailments is proposed. • The relationship between turnout component failures and climate impact is assessed. • The suggested model is validated through actual derailment cases in the US. [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]

• 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]

• Unprecedented effects of unconstrained length of railway tracks are highlighted. • Physical nature of track buckling is studied using nonlinear FEM models. • Interspersed approach can shift failure from progressive to snap-through buckling. • Buckling of timber sleepered tracks can be prevented by interspersed approach. • Track lateral resistance plays a significant role in track buckling prevention. In a conventional railway system, timber sleepers have been widely used for ballasted railway tracks to carry passengers and transport goods. However, due to the limited availability of reliable and high-quality timbers, and restrictions on deforestation, the "interspersed" approach is adopted to replace ageing timbers with concrete sleepers. The replacement of ageing timber sleepers is frequently done over old and soft existing formations, which have been in service for so long, by installing new stiff concrete sleepers in their place. This method provides a cost-effective and quick solution for the second and third track classes to maintain track quality. Presently, railway track buckling, caused by extreme temperature, 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. According to the buckling evidences seen around the world, buckling usually occurs in ballasted track with timber sleepers and thus there is a clear need to improve the buckling resistance of railway tracks. However, the buckling of interspersed tracks has not been fully studied. This unprecedented study highlights 3D finite element modelling of interspersed railway tracks subjected to temperature change. The effect of the boundary conditions on the buckling shape is investigated. The results show that the interspersed approach may reduce the likelihood of track buckling. The results can be used to predict the buckling temperature and to inspect the conditions of interspersed railway tracks. The new findings highlight the buckling phenomena of interspersed railway tracks, which are usually adopted during railway transformations from timber to concrete sleepered tracks in real-life practices globally. The insight into interspersed railway tracks derived from this study will underpin the life cycle design, maintenance, and construction strategies related to the use of concrete sleepers as spot replacement sleepers in ageing railway track systems. [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]

• Critical reviews of over 270 research articles related to bridge bearings have been conducted. • Failure modes of bridge bearings are identified and prioritised. • Alternative replacements of bridge bearings by composites is highlighted. • Meta-functional composite bridge bearings via additive manufacturing (AM) technologies have been proposed. • Insights stemming from this study underpin the industry adoption of AM technologies. One of the most important causes of bridge failure is the design and structural deficiencies of bridge bearings. Recently, typical bridge bearings with the reinforcement of steel or fibre have been widely used in base isolation system. Especially for fibre-reinforced rubber bearings, they offer numerous benefits as higher stiffness and strength, more flexibility, and decrease of transport and fabrication costs. Under vibration, common bridge bearings cannot perform well and the materials used in the bearings cannot sustain under environmental conditions. To develop the performance of these common bearings to obtain their superior physical and mechanical properties (e.g. lightweight, higher stiffness, better impact resistence, and vibration attenuation), the use of metamaterials (periodic structures) in the bearings is considered for this reason. The current paper is the world's first to present a comprehensive, state-of-the-art overview of the development of meta-functional composites for bridge bearing applications, exposed to both static and dynamic conditions. Also, the paper shows an approach to fabricate meta-functional composite bridge bearings via additive manufacturing (AM) technologies. Furthermore, the numerical simulation has been conducted to enable new insights into the behavior of a meta-functional bridge bearing suitable for real-life practial applications. These insights are fundamental to the performance benchmarking including the development of vibration-based condition monitoring and inspection for predictive bridge component maintenance. [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]

• Human errors causing derailments at switches and crossings were identified and classified. • A novel methodology dealing with the errors was proposed. • A novel DAG (Directed Acyclic Graph) built through Bayesian network was proposed. • The risks of errors were identified and analysed using new mathematical expressions. • Risk is prioritised by a most-to-least-critical importance ranking of human errors. The knowledge acquired in relation to failures associated with components has made significant contributions to the development of components with increased reliability, as well as a reduction in the number of rail incidents caused by certain system defects. These new systems have led to innovative developments in both the operations and technology of rail networks. Hence, rail employees must now function in conditions that have high complexity that are hard to comprehend. The risk of failure caused by human error (such as by dispatchers, train crews and track engineers) has developed into a significant safety problem. This study is the world first to provide novel insights into better understanding human errors, which result in derailments at rail turnouts. A most- to-least-critical importance ranking of these errors is established throughout a novel risk management technique. Moreover, the new findings and recommendations of this research study have a strong potential for industry to improve the reliability of rail operation, and avoid safety concerns regarding train derailments at rail turnouts. [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]

• This the world's first to establish a probabilistic Bayesian model for railway operations. • Model verifications against the long-term FRA's data exhibit excellent accuracy >95%. • Both of decision tree and Petri-nets models are embedded for risk assessment. • Both DT and PT models can be practically used by any railway authorities. • Railway accident reduction and reliability can be achieved by model adoption. Not only has the railway accidental prevention been a prime focus, but it has also become a key challenge for the industry in recent years. For many decades, rail authorities have attempted to significantly improve rail safety, whilst facing various passengers' risks and uncertainties. The overarching goal of this study is to develop a new posterior probability model to quantify uncertainties for benchmarking. This is the world's first to establish new insights from the benchmarking of risk and safety across different rail networks. The insights will point out the advantages and practicability of launching safety policies and reducing railway accidents for other rail networks. The new model has been developed using unparalleled long-term accidental data sets, including 'a trailer an accident' and 'causes of the accident'. The investigation adopts a Bayesian approach (via Python) to codify the novel model. The new findings lead to the better understanding into the uncertainty of railway accidents. Five notable rail networks have been selected as case studies. This study has also compared the effectiveness of the decision tree and Petri-net models using the posterior probability and number of injuries and fatalities. Based on the benchmarking outcomes, Chinese and Japanese railway systems denote the lowest risk over other networks, followed by Spanish, French and South Korean rail networks. The study also demonstrates that the novel benchmarking criteria can effectively measure and compare any rail networks' risk and uncertainties. Its adoption will lead to performance improvement in terms of safety, reliability and maintenance policies of railway networks globally. [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]

According to a recent estimate, over 1.5 billion wasted tyres which containing over 40% of vulcanised rubber and 15% of steel fibre are discarded yearly, which posing a serious threat to circular economy implementation and transition to net zero. To minimise the greenhouse gas(GHG) emission and the environmental side effect caused by burning and burying these waste tyres, recycling and reusing these materials for sustainable structural designs has become the centre of attention. This paper focuses on applying recycled bead steel fibre to improve the shear capacity of fibre-reinforced concrete beams. Moreover, the existing national standard known as Eurocode 2 and TR63 can hardly illustrate the relationship between fibre and high-strength concrete. This study is the first to investigate shear behaviours of high-strength industrial and recycled steel fibre reinforced concrete beams with consideration of different shear span ratios. Therefore, twenty real-scale beams are constructed to examine the shear capacity of high-strength industrial and recycled steel-fibre reinforced concrete beams, which aims to compare the improvement of shear strength through experiments and identify different shear strength improvements of the two categories of steel fibre. Besides, comprehensive data of 164 beams from previous studies have been collected to benchmark with the experimental results for the formula design. This study proves the feasibility of replacing industrial steel with recycled steel fibre to improve the shear capacity of fibre-reintroduced concrete beams. Moreover, there are six novel equations designed developed using Eurocode 2 and TR63 as a basis in this study. Based on the findings of the paper, the proposed formulas demonstrate remarkable accuracy, with an average value of 0.982 and standard deviation of 0.213, respectively. Following an exhaustive comparison of RSF and ISF reinforced concrete beams, with a focus on economic expenditure and GHG emissions, it can be concluded that RSF offers superior economic and environmental benefits, which reduce the emissions up to 25.39% and price up to 28.04% when replacing ISF 0.8% RSF, respectively. • This study stems from full scale experiments using recycled steel fibres. • It is the first to establish sustainable design framework for fibre reinforced concrete beams. • Sustainability design and assessments of recycled steel fibre reinforced concrete is established. • The outcomes highlight new pragmatic technical solutions to reduce wastes and implement circular economy. • The insight will enable an innovative alternative to achieve net-zero infrastructures. [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]

• 3D coupled train-track-soil interaction model combined with PML is firstly proposed. • Seismic metamaterial is firstly adopted for mitigating vibrations in railways. • Mitigated frequencies are in line with the band gap from dispersion analysis. • Seismic metamaterial exhibits excellent performance in ground vibration mitigation. With the rapid development of high speed rail system, ground vibration mitigation solutions are desperately needed. Based on the concepts of phononic crystals, seismic metamaterial, which is a novel vibration mitigation method, can theoretically yield excellent performance in shielding dynamic propagation waves in broad frequency bands. However, the application of seismic metamaterials in railway-induced vibration mitigation is a very recent and ongoing topic. Therefore, this study is the world's first to establish new and practical contribution towards a better understanding into the mitigation effects by seismic metamaterials for railway-induced ground vibrations. The seismic metamaterials are made of an array of concrete inclusions in this study. The dispersion theory for seismic metamaterials is proposed for analyzing the theoretical band gaps. A 3D coupled train-track-soil interaction model is also developed based on the multi-body simulation principle, finite element theory, and perfectly matched layers method using LS-DYNA. The dimensions of seismic metamaterials are determined based on the dominant frequencies of vibration accelerations in natural ground. When the seismic metamaterials are adopted in railway ground, the vibration responses are investigated in both time and frequency domains to illustrate the mitigation effects. Finally, the numbers of inclusions, initial distances, and train speeds are changed to investigate their influences on shielding effects. The novel insight stemmed from this study incites an original and better understanding into the attenuation of ground vibrations using seismic metamaterials in high speed railways. [ABSTRACT FROM AUTHOR]