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With an emphasis on the combined degradation of railway track geometry and components, a new numerical-analytical method is proposed for predicting the track geometrical vertical levelling loss (VLL). In contrast to previous studies, this research unprecedentedly considers the influence of initial track irregularities (ITI) on VLL under cyclic loadings, elastic-plastic behaviour, and different operational dynamic conditions. The non-linear numerical models are simulated using an explicit finite element package known as LS-Dyna, and their results are validated by full-scale experimental and field measurement data. The outcomes are iteratively regressed by an analytical logarithmic function that cumulates permanent settlements, which innovatively extends the effect of ITI on VLL in a long-term behaviour. For a typical heavy-haul railway operating under 30 tons axle load and 60 km/h train velocity, the result indicates that the set of ITI with the highest standard deviation (SD) of vertical profile (VP) degrades faster (37% on average) than that with the lowest SD. Additionally, our new findings reveal that the worst scenario is related to a train running at 60 km/h and carrying a load of 20 tons/axle in an uneven track whose SD of VP evolves from 3.23 mm at N = 0 (ITI) to 7.20 mm, whereas the best one corresponds to a train at 60 km/h and 30 ton axle load in an uneven track whose SD of VP downgrades from 0.48 to 1.50 mm, both at 3 M cycles (or 60 million gross tons). These findings indicate the importance of considering the ITI for predicting track geometrical VLL under cyclic loadings. Therefore, based on this research, an acceptable condition (thresholds) of ITI can be redefined for a minimum effect on VLL, which can support the development of practical maintenance guidelines to extend the railway track service life.

Super-high-speed guided systems such as hyperloops and MagLev are highly at risk of cyber and physical threats from either natural or man-made hazards. This study thus adopts a nonlinear finite element method to investigate and analyse blast responses of a spatial thin-shell structure formed as an essential part of the Hyperloop tunnelling system. The thin-shell structure is a longitudinal cylindrical tube used in hyperloop rail concepts that will have the capability to carry passenger pods travelling at speeds in excess of 1000 km/h. A robust parametric study has been carried out on a thin-shell metallic cylinder in accordance with experimental results to validate the blast simulation modelling approach. In addition, case studies have been conducted to simulate the effects of varied charge loading (TNT equivalent) of 10 kg, 15 kg and 20 kg. Since the hyperloop system is in its development stages, potential design modifications to adjust the thickness of the thin-shell cylinder are also simulated. Our findings demonstrate that thicker walls of 30 mm yield almost negligible dynamic displacements with lower blast pressures. However, this modification can cause serious ramifications in terms of infrastructure costs. On this ground, venting ports for blast mitigation have been proposed to alter and alleviate blast effects on the tube deformations. The novel insights reveal that increased venting port sizes can significantly increase the impulse deformations of the hyperloop tube but are key in reducing blast pressures within the asset infrastructure. These findings will inform hyperloop engineers about potential design solutions to ensure safety and reliability of future hyperloop rail travels amid the risks and uncertainties of cyber and physical threats. [ABSTRACT FROM AUTHOR]

The interspersed railway track is an enhanced timber railway track, spot-replacing damaged wooden sleepers with new concrete sleepers to improve the bearing capacity of existing railway lines. Although this interspersed solution is characterised by low cost and short maintenance time, the interspersed tracks have worse stability than concrete tracks and can deteriorate quickly when exposed to extreme weather conditions such as heavy rains and floods. In many cases, heavy rains and floods are accompanied by strong winds. Ballast washaway can often be observed under flood conditions while the mass of trains is unevenly distributed on two rails due to the effect of lateral wind load and rail irregularities. The current work is the first in the world to investigate the collective multi-hazard effects of ballast washway and uneven axle loads on the vulnerability of conventional and interspersed railway tracks using nonlinear FEM software, STRAND 7. The train bogie is modelled by two sets of point loads. The maximum displacement, bending moment and twists have been studied to evaluate the worst condition. The novel insights will help the railway industry develop proper operations of interspersed railway tracks against naturally hazardous conditions. [ABSTRACT FROM AUTHOR]

The increase in demand for railway transportation results in a significant need for higher train axle load and faster speed. Weak and sensitive trackforms such as railway switches and crossings (or called 'turnout') can suffer from such an increase in either axle loads or speeds. Moreover, railway turnout supports can deteriorate from other incidences due to extreme weather such as floods which undermine cohesion between ballast leading to ballast washaway or loss of support under turnout structures. In this study, new intelligent automation based on machine learning pattern recognition has been built to detect and predict the deterioration of railway turnouts exposed to flooding conditions which is the scope of this study. Since the turnout system is very complex by nature, different features and smart filtering are explored to find the potential features for deep learning. Nonlinear finite element models validated by actual field measurements are used to mimic the dynamic behaviors of turnout supports under flooding conditions. The study exhibits that the novel recognition model can achieve more than 98% accuracy, yielding the potential capability to recognize and classify turnout support deteriorations facing extreme weather conditions which will be beneficial for responsible parties to schedule and plan maintenance activities. [ABSTRACT FROM AUTHOR]

Railway turnouts are essential in the train traffic route management for modern railways. Despite significant devotion to railway turnout research, one of their most common failures has not been thoroughly investigated, which is a fatigue over the turnout crossing nose. At the crossings, wheel-rail discontinuity imparts high-frequency high-magnitude forces, which are the source of fatigue failure over the crossing nose. In this study, a novel approach built on "Peridynamics" (PD) has been developed to obtain new insights into the fatigue cracks. A recent approach using "crack on mid-plane" has also been employed in this study to enhance the limited capability of Peridynamics. This paper is the world's first to investigate fatigue failures over a crossing nose from fracture mechanics perspective. This paper also introduces a novel adaptive time-mapping method as an alternative to earlier time-mapping methods for fatigue models proposed in the open literature. The new model has been verified against both Finite Element Method and experimental data. It reveals that our new approach can simulate fatigue damage, particularly in mode I crack propagation. The study has provided important insights on the fatigue crack development, which is not possible before by existing Peridynamics fatigue model. The new approach on the basis of "adaptive time-mapping" and "crack on mid-plane" is demonstrated to be effective and efficient in PD simulations. [ABSTRACT FROM AUTHOR]

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

Railway sleepers are safety–critical components of a railway structure. They support ballasted track superstructure and are a critical factor in track geometry and track components' deterioration. Unsupported sleepers are a common issue incurred after tracks have been utilized. When unsupported sleepers are present, they cause differential settlements of track superstructures, additional dynamic loading, and excessive train-track vibrations which affect passenger comfort, safety, and maintenance cost. This study is the world's first to develop new machine learning models to prognose and better diagnose defect severities of unsupported sleepers aligned with practical track inspection guidelines. Data used to develop machine learning models are based on a verified finite element model with actual field measurements, enabling unbiased full data ranges that govern all defect conditions. Different conditions of unsupported sleepers can be explored by varying locations of unsupported sleepers and the number of unsupported sleepers. Also, other operational parameters can be addressed such as speeds of rolling stock, the roughness of rail surface, and vertical stiffness of wheel-rail contact. In total, 2016 data sets have been obtained. Axle box accelerations are adopted as key indicators for machine learning models. Machine learning techniques used in the study are the convolutional neural network, recurrent neural network, ResNet, and fully convolutional neural network. Data fusion and assimilation have been conducted since the data points are dependent on the train speeds. Our new results reveal a breakthrough essential for real-world applications that the convolutional neural network model provides the best accuracy in both unsupported sleeper prognostics and severity identification. The accuracies of detection and severity identification are 99.34% and 97.02% respectively. [ABSTRACT FROM AUTHOR]

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

This paper presents a novel meta-functional auxetic unit (MFAU) cell designed to improve performance and weight ratio for structural bridge bearing applications. Numerical investigations were conducted using three-dimensional finite element models validated by experimental results. The validated models were exposed to compression and buckling actions to identify structural failure modes, with special attention placed on the global behaviours of the meta-functional auxetic (MFA) composite bridge bearing. This bearing uses an unprecedented auxetic sandwich core design consisting of multiple MFAU cells. Numerical predictions of the elastic local critical buckling loads of the MFAU cell were in excellent agreement with both the analytical and experimental results, with an observed discrepancy of less than 1%. These results demonstrate that local buckling failures of MFAU cells can potentially be incurred prior to yielding under compression due to their slenderness ratios. Surprisingly, the designed sandwich core used in the MFA composite bridge bearing model can mimic an auxetic structure with significant crashworthiness, implying that this novel core composite structure can be tailored for structural bridge bearing applications. Parametric studies were thus carried out in order to enrich our insight into the MFA composite elements. These insights, stemming from both experimental and numerical studies, enable a novel design paradigm for MFAU that can significantly enhance the structural performance of MFA composite bridge bearings in practice. [ABSTRACT FROM AUTHOR]

This paper adopts both explicit and implicit finite element methods in a specialist package LS-DYNA to investigate the nonlinear, dynamic response of a long span shell roof structure when subjected to blast loading. Parametric studies have been carried out on blast loaded laminated glass plates with reference to experimental results obtained by European researchers. A case study that has been chosen is a light rail station in The Netherlands called The Erasmusline. Following the detonation of 15 kg TNT charge, explicit analysis showed breakage surrounding the rigid supports along the edge beam where modal vibrations are restrained. An implicit analysis has confirmed the resonances in global eigen-frequencies where most blast damage is localized around the roof canopy hence producing cracking and potential glass detachment from the panels without full structural demolition. This insight from this study will inform structural engineers about the potential modes of failure and preventative strategies to minimize further secondary losses of life or assets from a terrorist attack. [ABSTRACT FROM AUTHOR]

Featured Application: The new findings highlight for the first time the nonlinear dynamic phenomena of turnout systems considering unsupported composite and concrete sleepers and bearers. The in-depth insights stemmed from multi-body simulations of dynamic train—turnout interaction demonstrates the influences of unsupported sleepers on dynamic responses, load redistributions, dynamic impact factors and wheel/rail contact forces. The novel insights can be used (not limited to) as a reference for the design, inspection and maintenance of railway switches and crossings. Track settlement is a common problem observed in ballasted railway tracks. The ballast bed and the material layers underneath it, deform under repeated trainloads and create uneven support conditions along the track. In some cases, the ballast settlement could be detrimental and the sleepers lose contact with the ballast bed partially or completely, resulting in higher contact forces and load distributions over the supported sleepers. Numerous studies have been conducted to investigate the phenomenon for normal tracks. Nevertheless, railway turnouts are somehow neglected. As a consequence, this study focuses on the relation between unsupported sleepers/bearers (particular name for turnouts) and a railway turnout system to develop the understanding of the response of turnout system under dynamic loadings. A 3D Finite Element Method (FEM) model is inherited from previous study and adopted to reflect the cases with unsupported bearer configurations. It is noteworthy that inherited model is capable of reflecting the impact forces, which is an inherent and fundamental characteristic of a railway turnout. Model verification is done with the parent model that was verified by field measurements. Three different support conditions (i.e., one, two, three unsupported bearers), five different velocities and six different positions of unsupported bearers are simulated. The results show that the performance of 'fibre-reinforced foamed urethane' (FFU) bearers are promising and more, unsupported bearers carry significant loads at particular locations, which is contrary to the sleepers on normal track that are subjected to insignificant loads. [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]

Rail turnouts are built to enable flexibility in the rail network as they allow for vehicles to switch between various tracks, therefore maximizing the utilisation of existing rail infrastructure. In general, railway turnouts are a safety-critical and expensive feature to a rail system as they suffer aggressive operational loads, in comparison to a plain rail track, and thus require frequent monitoring and maintenance. In practice, great consideration is given to the dynamic interaction between the turnouts components as a failed component may have adverse effects on the performance of neighbouring components. This paper presents a nonlinear 3D finite element (FE)model, taking into account the nonlinearities of materials, in order to evaluate the interaction and behaviour of turnout components. Using ABAQUS, the finite element model was developed to simulate standard concrete bearers with 60 kg/m rail and with a tangential turnout radius of 250 m. The turnout structure is supported by a ballast layer, which is represented by a nonlinearly deformable tensionless solid. The numerical studies firstly demonstrate the importance of load transfer mechanisms in the failure modes of the turnout components. The outcome will lead to a better design and maintenance of railway turnouts, improving public safety and operational reliability. [ABSTRACT FROM AUTHOR]

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]

Ballasted railway tracks are impaired due to either normal or abnormal operations. One of the problems is the differential settlements along the track. Clearly, there is the need to maintain periodically the track substructures by means of ballast packing/tamping. Inappropriate conducts result in the nonlinear distributions of support stiffness. This study firstly demonstrates the effects of improper ballast packing/tamping on the free vibration behaviors of in situ railway concrete sleepers. The two-dimensional finite element modeling of an in situ concrete sleeper was employed in the parametric studies. This model takes into account the coupled flexural-and-shear deformations of concrete sleepers, elastic displacements of fastening system, and nonlinear dynamic interaction between the sleeper and ballast support. Dynamic interaction between sleepers and ballast was investigated based on the nonlinear distribution of ballast support stiffness underneath the sleeper. Effects of both symmetrical and asymmetrical stiffness distributions on dynamic behaviors of the local in situ concrete sleeper were also highlighted. [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]

• 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]

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]

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]

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]