High-speed Railway System Research Articles

Research on System Architecture, Basic Platform, and Development Path of Autonomous Intelligent High-Speed Railway System

Research on System Architecture, Basic Platform, and Development Path of Autonomous Intelligent High-Speed Railway System

Analysis of the principle and applications of aerodynamics in high-speed railway

In recent years, high speed railway trains are a main part of modern transportation which brings extremely convenient. In this case, studies on aerodynamic performances and phenomenon of trains are the core for further development of high-speed trains. With this in mind, this paper briefly introduced aerodynamic formulae as well as summarized some major computational designs of train noses, with the corresponding experimental results of some designs. On this basis, the application of some designs was explained, with follow up limitations and outlooks of aerodynamics of high-speed trains. According to the analysis, results show that designs in China focus more on reducing aerodynamic drag, while the flatter design in Japan has a better overall aerodynamic performance. In addition, the limitations of current facilities as well as the prospects for the high-speed railway systems are demonstrated. Overall, these results shed light on guiding further exploration of high speed railway development.

Laboratory investigation on the fracture toughness (Mode I) and durability properties of eco-friendly cement emulsified asphalt mortar (CRTS II) exposed to acid attack

Cement Emulsified Asphalt Mortar (CEAM) has gained prominence as a vital material for its energy and noise damping properties between the concrete roadbed and track slab in a high-speed railway system. Therefore, it is evident that CEAM properties need to be better understood and optimized. Since cracking caused by traffic loading and atmospheric conditions is one of the primary causes of failure in CEAM, addressing this issue is of great importance. Furthermore, there is a growing need for more environmentally friendly and durable CEAM due to the environmental impact of cement production in the form of greenhouse effect. The objective of this study is to assess the impact of partially replacing cement content in CEAM Type II (CRTS II) specimens with pozzolanic materials such as silica fume, metakaolin, and granite sludge to investigate how these pozzolans affect the fracture toughness (Mode I) performance under both normal (water curing) and sulfuric acid exposure conditions with the main focus on evaluating the pozzolans ability to resist acid attack from a fracture toughness perspective as the research novelty. For this purpose, specimens containing pozzolans at 5 %, 10 %, and 15 % substitution level (by weight of cement) were subjected to Semi-Circular Bending (SCB) test both under normal and exposure to 5 % sulfuric acid solution conditions. Moreover, water absorption test was conducted on specimens in normal condition as a durability index. The test results of this study revealed that substitution of these pozzolanic materials enhanced the fracture toughness in normal condition. Specifically, at a 10 % substitution as the optimal level, silica fume and metakaolin resulted in 18 % and 15 % increase in fracture toughness performance compared to the control specimen in normal condition. However, granite sludge exhibited almost the same performance as the control specimen at 5% substitution as its optimal level. In acid exposure condition, the detrimental effect of acid on the fracture toughness performance of specimens was reduced by 61 %, 55 % and 13 % for samples containing silica fume, metakaolin and granite sludge at 15% substitution level, respectively. Furthermore, water absorption test results showed that inclusion of silica fume and metakaolin at a substitution level of 15 % results in 56 % and 47 % reduction in water absorption compared to the control specimen, respectively, while for granite sludge, it was almost the same as control specimen. These results were also confirmed by SEM studies. Since the use of these pozzolans as cement substitution not only improves the fracture toughness in normal condition but also provides protection against acid-induced degradation, this study contributes to the development of a more durable and environmentally friendly CEAM.

DEVELOPMENT AND CHARACTERISATION OF PANTOGRAPH SLIDES FOR RAILWAY APPLICATIONS: A SHORT REVIEW

High-speed railways have transformed global transportation, leading to increased economic activity and reduced congestion. Railway development is surging in Asia, encompassing upgrades to existing lines and the construction of new high-speed railways. This article explores the materials, processes, and properties of pantograph slides. A pantograph slide is an important component of top-running rails that enables the transmission of electrical energy from traction substations to moving trains. This review presents the evolution of pantograph slide materials, such as metal slide plates, pure carbon slides, powder metallurgy slides, metal-impregnated slides, and composite slides. The characterisations of pantograph slide properties, such as density, resistivity, hardness, impact, and flexural properties are also reported. This article delves into the utilisation of local materials, particularly carbon derived from palm kernel shells and coconut shells, as well as graphene from petroleum coke, for the development of current collectors. These findings may contribute to the understanding of pantograph slide materials and provide insights into the potential use of sustainable materials in high-speed railway systems.

System-level seismic fragility of high-speed railway track-bridge system with component-replaceable U-shaped combined steel damper

A component-replaceable U-shaped combined steel damper (UCSD) was presented as an energy dissipation device to mitigate the seismic damage of high-speed railway track-bridge system (HSRTBS). The energy-dissipation modules inside the UCSD can be replaced by removing the high-tensile bolts. A low cyclic test of the energy dissipation module was carried out. Parametric analysis of the UCSD with varying U-shaped plate thicknesses was conducted using finite element analysis, including 8, 10, 12, 14, and 16 mm. To study the effect of the UCSD on HSRTBS under near-fault ground motions, twenty-eight near-fault records recommended by FEMA-P695 were selected, and the UCSD was installed adjacent to bearings in HSRTBS. Component-level fragility curves of HSRTBS with UCSDs with the different thicknesses of U-shaped plates were compared. To comprehensively and efficiently evaluate the contribution of the UCSDs on HSRTBS, system-level fragility curves were obtained by the product of the conditional marginal (PCM) method. Results indicate that the UCSD exhibits excellent hysteresis performance and energy dissipation capacity, improving with the U-shaped plate. At the maximum considered earthquakes (MCE) level, the exceeding probability of complete damage of the system is reduced from 100 % to 95 %, 79 %, 57 %, 35 %, and 20 % respectively after adding UCSDs in five different U-shaped plate thicknesses. This reveals that the proposed UCSD can effectively mitigate HSRTBS seismic damage under near-fault motions, progressively improving with increased U-shaped plate thickness.

Modeling and analysis of transition-point disappearance in high-speed railway pantograph-catenary system

During the operation of high-speed railway, the transition-point disappearance phenomenon, which is caused by the deformation of pantograph head, poses a safety threat to the pantograph-catenary system. In this study, the analytical model for transition-point disappearance analysis is presented. The instantaneous profile, as well as the deformation process of the pantograph head under different contact force values and positions or different pantograph-head parameters can be solved using the model. Curve equation, force analysis, coordinate axis rotation, and few other methods are adopted to achieve simplified modeling. The proposed modeling method and analysis conclusion provide theoretical support for the permissible contact force range calculation and pantograph-head parameters optimization to prevent transition-point disappearance. The effectiveness of the proposed model is verified using both finite element simulation and experimental measurements. Finally, a case analysis for the prevention of transition-point disappearance is conducted, using pantographs with the models CX-GI and DSA250 as examples.

A method for reliability assessment of complex electromechanical system based on improved network connectivity entropy

The interconnectivity of components in complex electromechanical system (CMES) plays a critical role in ensuring system reliability. To examine the effect of component failures on system reliability, this work proposes a new reliability assessment method for CEMS based on improved network connectivity entropy. This method takes into account the mechanical, electrical, and information characteristics of components, and employs a comprehensive component importance calculation approach based on PageRank, which considers the functional impact of components. The reliability assessment model, considering both functional and topological attributes of the system, is established through the theory of network connectivity entropy. The proposed method is then demonstrated through an application to a bogie system of the CRH2008A high-speed railway. The proposed approach, rooted in topological networks, integrates component degradation into the physical structure of CEMS, providing a comprehensive way to deduce the impact of component failures on system reliability. Validity is demonstrated through case studies.

VHXLA: A post-earthquake damage prediction method for high-speed railway track-bridge system using VMD and hybrid neural network

The timely and accurate prediction of post-earthquake damage is critically important for ensuring the safety of high-speed railway track-bridge systems. The study introduces a novel method known as the VHXLA model. This innovative model blends variational mode decomposition (VMD) with a hybrid neural network for predicting non-linear multi-component post-earthquake damage in high-speed railways. The VHXLA model comprises a signal processing module and a deep learning module. The signal processing module utilises VMD decomposition, and the Hilbert transform (HT) to transform two-dimensional seismic signals into four-dimensional complex time–frequency signals, thus simplifying the task of identifying seismic time–frequency characteristics via the neural network. The deep learning module integrates diverse types of neural network components, such as the Xception CNN feature extraction submodule, the LSTM RNN temporal learning submodule, and the multi-head attention mechanism submodule. A Bayesian self-optimisation method is implemented to determine the number of decomposition layers in VMD and select essential hyperparameters. The model's effectiveness is evaluated by predicting the damage of an experimentally validated finite element model, subjecting it to seismic loads, and thus gauging its performance. The results indicated that the signal processing module, based on VMD decomposition, significantly improves the neural network's signal processing capability. In addition, the synergistic integration of different modules in the VHXLA model provides superior prediction accuracy compared to pre-existing damage prediction models. Notably, the prediction accuracy is consistent across different positions of the same predicted component in the high-speed railway track-bridge system.

Two-dimensional seismic simulation based on spectral element method and its application in high-speed railway track-bridge system

Seismic investigations of engineering structures under near-field ground motions typically utilize probabilistic earthquake methods. This study introduces a two-dimensional profile model developed for the spectral element method, taking the Chi-Chi earthquake as an exemplar. By integrating source parameters and station information, we use the SPECFEM2D code for seismic simulations. To demonstrate our method's practicality, we compare the PGA and spectrum of our simulated ground motions with actual seismic records. Further, we calculate the seismic response of the high-speed railway track and bridge system (HSRTBS) under two seismic excitations, assessing peak response errors across the track system, girder, support, and pier. The case study verifies that the simulated ground motions in this paper can be used in the seismic analysis of HSRTBS, providing seismic excitation for the seismic design of the structure and effectively complementing the scenario with limited seismic records. Moreover, the seismic simulation method used in this paper can reduce the number of elements and improve computational efficiency.

User-Assisted Base Station Caching and Cooperative Prefetching for High-Speed Railway Systems

With the aim of reducing the transmission latency, this paper proposes a scheme of user-assisted base station (BS) caching and cooperative prefetching for high-speed railway (HSR) communications. In the model under consideration, neighboring BSs periodically exchange information, including the coverage area and communication rate, to facilitate content caching and prefetching. As an additional means, users can cache contents that are different from BSs. Specifically, we construct an optimization problem for content caching and prefetching that minimizes the overall transmission latency. Moreover, this problem is decomposed into two subproblems, namely the one aiming to maximize the available throughput of BSs and the other attempting to maximize the user cache utilization subject to the constraint of the BS cache. We demonstrate that the objective function of the first subproblem is equivalent to a monotone submodular function subject to matroid constraints. Therefore, it can be efficiently solved with a greedy algorithm. Meanwhile, the user cache issue can be viewed as a weighted sum maximization problem. Simulation results are presented to verify that the proposed scheme can not only reduce the average transmission latency but also improve the hit probability and system throughput.

Efficiency benchmarking and its determinants in high-speed railways: Reference for China

The high-speed railway (HSR) performance has drawn considerable attention from international scholars and policymakers. One heatedly-discussed topic is measuring HSR efficiency and its important determinants, particularly HSR organizational structures. The main contribution of our research is the adoption of the multi-stage Network Data Envelopment Analysis (DEA) and Tobit Model, which provides a rational and coherent method to address this issue.We select the dataset from main HSR countries during the period of 2009–2018, and rank the efficiency of HSRs of different countries. Subsequently we examine the relationship between HSR efficiency and characteristic determinants, along with geographical and economic indicators that may influence the model.The results have revealed the HSR productivity difference do exist among countries. Overall, Asia's HSR systems demonstrate higher efficiency compared to those in Europe; while China's HSR efficiency ranks medium in the HSR multi-stages chain but higher in the service stage. Furthermore, the determinants of organizational structure can significantly effect on the effectiveness of HSR systems under a certain transport density threshold. In conclusion, regulators and operators should endeavor to increase traffic by meeting the demand to improve system efficiency. For China, focusing on vertical integration should be the key aspect of future HSR reform.

Key technologies and applications of intelligent dispatching command for high-speed railway in China

PurposeThe intelligent Central Traffic Control (CTC) system plays a vital role in establishing an intelligent high-speed railway (HSR) system. As the core of HSR transportation command, the intelligent CTC system is a new HSR dispatching command system that integrates the widely used CTC in China with the practical service requirements of intelligent dispatching. This paper aims to propose key technologies and applications for intelligent dispatching command in HSR in China.Design/methodology/approachThis paper first briefly introduces the functions and configuration of the intelligent CTC system. Some new servers, terminals and interfaces are introduced, which are plan adjustment server/terminal, interface for automatic train operation (ATO), interface for Dynamic Monitoring System of Train Control Equipment (DMS), interface for Power Supervisory Control and Data Acquisition (PSCADA), interface for Disaster Monitoring, etc.FindingsThe key technologies applied in the intelligent CTC system include automatic adjustment of train operation plans, safety control of train routes and commands, traffic information data platform, integrated simulation of traffic dispatching and ATO function. These technologies have been applied in the Beijing-Zhangjiakou HSR, which commenced operations at the end of 2019. Implementing these key intelligent functions has improved the train dispatching command capacity, ensured the safe operation of intelligent HSR, reduced the labor intensity of dispatching operators and enhanced the intelligence level of China's dispatching system.Originality/valueThis paper provides further challenges and research directions for the intelligent dispatching command of HSR. To achieve the objectives, new measures need to be conducted, including the development of advanced technologies for intelligent dispatching command, coping with new requirements with the development of China's railway signaling system, the integration of traffic dispatching and train control and the application of AI and data-driven modeling and methods.

Development patterns, material metabolism, and greenhouse gas emissions of high-speed railway in China

China built the longest high-speed railway system by consuming massive construction materials. However, characterization material metabolism in HSR system remains less explored. Here we conducted a bottom-up material metabolism study and revealed the material stocks, flows, and greenhouse gas emissions from 2008 to 2035 in China’s high-speed railway. We show that material stocks temporally amount from 0.6 gigatons in 2010 to 3.7 gigatons in 2020, dominated by aggregate and cement. Spatially, material stock distribution gaps across Chinese provinces are becoming more narrowed. Material flows wise, growing high-speed railway speed increased resource demands, but construction technology and material production advances could offset these increases. Our results demonstrate the carbon replacement value of 1008 megatons by 2020 and the operational emissions of 31 megatons annually. Compared with road and aviation passenger transport, we highlighted the environmental benefits of high-speed railway for informing green transitions.

A Reliable and Intelligent Deep Learning Based Demodulator for M-Ary Code Shifted Differential Chaos Shift Keying System With Power Allocation

In high-speed railway systems, channel conditions are dramatically changing, which brings great challenges to information transmissions. Our objective is to improve the reliability performances by utilizing the deep learning (DL) scheme to intelligently extract the features of signals to combat the complex dynamically changing channel conditions. In this paper, we propose a DL-aided demodulation scheme for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary code shifted differential chaos shift keying system with power allocation (PA-GCS-MDCSK) to enhance reliability performance. In this design, the deep neural network (DNN) adopts fully-connected layers (FCLs) to conduct the joint de-spreading of Walsh codes and chaotic demodulations. Meanwhile, the long short-term memory (LSTM) unit with the residual structure is constructed to extract the correlation between the chaotic sequences, thus the interferences induced by real-valued chaotic sequences can be suppressed, thereby improving the reliability performance. Then the computational complexity is analyzed and compared with benchmark schemes. Simulation results over both additive white Gaussian noise (AWGN), fading, and railway channels validate that the proposed design can achieve better bit error rate (BER) and robustness performances than benchmark schemes.

Multiconductor Cell Analysis of AC High Speed Railway Lines

The aim of this paper is the application of Multiconductor Cell Analysis to a very special case of a multiconductor system, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e</i> ., the AC high-speed railway system, with 14 parallel conductors. The present matrix approach allows representing both the single elements and the entire railway system also including the high voltage three-phase supply network. The algorithm allows computing all the steady-state regime electrical quantities (voltages, currents and power) of each section: in particular, the ground return current, responsible for electromagnetic interferences, can be derived by the knowledge of all the circulating currents. It is also possible to evaluate the electric unbalance impact on the supply three-phase power system given by the railway system. Eventually, two different scenarios are presented, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e</i> ., a maximum allowable high-speed line power request and a contact-wire to rail short circuit.

Data-driven gale-induced risk assessment strategy for the high-speed railway system

Railway accidents caused by gales are indeed influenced by multiple factors, making them a complex process. However, current research and monitoring systems often focus solely on wind speed, overlooking the combined effects of other factors. This paper proposes a data-driven assessment strategy specifically designed for high-speed railways. The disaster-inducing factor, disaster-pregnant environment, disaster-bearing body, and disaster prevention/mitigation capabilities are all taken into consideration. Moreover, it explores the interrelationships between these factors. To validate the proposed mechanism, the spatial-temporal distribution of gale-induced risks along China’s high-speed railways is studied in this paper. By analyzing and interpreting the data, the researchers are able to identify areas and time periods that are particularly prone to gale-induced accidents. These findings are crucial for the development of effective strategies for disaster prevention and mitigation in the context of high-speed railways.

Seismic response of high-speed railway system under actions of ground motions from deterministic physics-based simulation

In order to investigate the response of a high-speed railway bridge under seismic excitations in the near-fault area, a deterministic physics-based method is used to construct the ground motion field in the near-fault area of a scenario earthquake. A finite element model of an assumed high-speed railway system is established, which consists of a finite length CRTS III ballastless track laid on a 15-span simply-supported girder bridge. The simulated ground motions and a group of three-component as-recorded accelerograms are used to provide non-uniform and uniform excitations at bridge piers, respectively. The seismic response of the rail-track-bridge system is calculated, and the effects of using different types of seismic excitations for the seismic analysis of the high-speed railway bridge in the near-fault area are analyzed. The results show that two end piers of a multi-span simply supported girder bridge could encounter remarkably different excitations in terms of waveform and frequency content for different bridge alignments in the near-fault area. The vertical response of the railway bridge system is more sensitive to the pattern of the excitation than the longitudinal response. Considering the spatial difference of ground motions among piers could increase the difference of the rail vertical displacement between the beam joint and mid-point of span, forming a remarkable periodic vertical irregularity of the rail. Using non-uniform excitation could lead to a reduction in DPeak and APeak which is most significant for DPeak in the vertical direction.

Pareto-improving seat allocation for high-speed railway networks with equilibrium flows

This paper develops optimization models for Pareto-improving seat allocation schemes in high-speed railway (HSR) networks, where time-dependent demand and equilibrium travel choices are incorporated. Under the Pareto-improving seat allocation scheme, at least some passengers are strictly better off, and no passenger is worse off, when compared to the situation with no seat allocation scheme. In particular, two scenarios with fixed and elastic passenger demands are considered. The passenger travel choice equilibrium conditions are taken as constraints for the seat allocation optimization model, which can be further reformulated into a mixed-integer linear programming (MILP) with the help of linearization, relaxation and outer-approximation techniques. The optimal solution then can be obtained by solving the proposed MILP. The numerical examples on two real-world regional HSR systems are presented to illustrate the proposed Pareto-improving seat allocation optimization approach.

Ultrasonic SH guided wave detection of the defects of switch rails with 3D finite element method

A switch rail is an important part of the high-speed railway system, but it is highly susceptible to defects during service, which threat traffic safety. A switch rail has an asymmetric variable cross-section structure, which makes it challenging to detect its defects with ultrasonic testing. In this study, the finite element model of switch rails and the ultrasonic SH guided wave detection of groove defects were explored. The three-dimensional finite element model of switch rails with the same sizes used under working conditions was established. Furthermore, the influences of grid division method, switch mechanism setting method, and root end variable cross-section grid type on guided wave propagation in the model were analyzed in detail. The switch rail model was experimentally validated. The ultrasonic SH guided wave detection of the defects at the rail head and rail bottom was successfully realized and the echo signals from other special structures of switch rail were also obtained. The finite element model calibrated with experimental results could be used to simulate guided wave detection at any location with any defect. The calibrated model could optimize the switch rail guided wave detection scheme and guide signal identification. The study provides an important basis for the inspection and monitoring of switch rails.

Optimal P2P based energy trading of flexible smart inter-city electric traction system and a wayside network: A case study in Alexandria, Egypt

In an open energy market, the peer-to-peer (P2P) energy trading policy became more applicable. Therefore, while planning for new electrified systems, such a trading policy is taken into consideration. On the other hand, as the electrification of railway systems along with the use of electric vehicles serve several sustainable development goals, plans are studied for the electrification of the inter-city railway system in Alexandria, Egypt, in order to connect it with the high-speed inter-provincial electric railway system. In addition, other plans are studied for local production of electric vehicles. For this purpose, this paper presents a study regarding P2P based optimal energy management (EM) of a flexible smart railway substation taking into consideration multiple energy sources of the traction system and the wayside distribution network. The energy sources of the substation include captured regenerative braking energy (RBE), photovoltaic (PV) units and a multistory parking garage of electric vehicles (EVs). The wayside distribution network also contains several energy sources including distributed generation and multiple energy hubs (EHs) in addition to district distribution area with flexible loads. Optimal energy management is carried out including optimal demand side management of flexible loads and EHs. The optimization study takes into consideration several operational uncertainties arising from several components of the system. The simulation results show the feasibility of applying the proposed EM algorithm with an improvement of the energy economics of the system.