Search Results (912)

The straightness of rail joints is one of the critical factors affecting passenger comfort in high-speed railways, and investigating its influence on the dynamic performance of the vehicle–track system and riding comfort is of great significance. In this study, long-term field measurements were conducted at a turnout joint of a newly constructed high-speed railway in China, combined with multibody dynamics simulations, to systematically analyze the long-term evolution of rail joint straightness under various conditions, including pre- and post-grinding, joint commissioning, official operation, and extreme weather. Based on normalized data processing, the root mean square (RMS) index of joint straightness was extracted for feature quantification. Together with vertical acceleration and the Sperling index obtained from vehicle–track coupled dynamics simulations, a quantitative relationship between straightness and comfort was established. The results indicate that the cubic polynomial fitting method can effectively characterize the nonlinear mapping between the RMS of joint straightness and the Sperling index, further revealing a critical threshold at approximately 0.4 mm RMS beyond which vehicle running stability deteriorates and ride comfort significantly worsens. This study provides a reliable theoretical basis and engineering reference for the evaluation of rail joint quality and the optimization of maintenance strategies. Full article

This study has developed a novel measurement-based computational method that accurately determines the vertical and lateral wheel–rail contact forces transmitted from railway vehicles to the rails. A major contribution—and the first in the literature—is the analytical distribution of the total lateral wheelset force into its outer-wheel and inner-wheel components, thereby enabling precise individual evaluation of derailment risk on each wheel in curved tracks. Analytical equations derived from Newton’s second law were first formulated to express both vertical forces and total axle lateral force directly from bogie/axle-box accelerations and suspension reactions. To eliminate the deviations caused by conventional simplifying assumptions (neglect of creep effects, wheel diameter variation, and constant contact geometry), surrogate functions and distribution equations sensitive to curve radius, vehicle speed, and cant deficiency were introduced for the first time and seamlessly integrated into the equations. Validation was performed using the Istanbul Tramway multibody model in SIMPACK 2024x.2, with the equations implemented in MATLAB/Simulink R2024b. Excellent agreement with SIMPACK reference results was achieved on straight tracks and curves, after regression-based calibration of the surrogate functions. Although the method requires an initial regression calibration within a simulation environment, it relies exclusively on measurable parameters, ensuring low cost, full compatibility with existing vehicle sensors, and genuine suitability for real-time monitoring. Consequently, it supports predictive maintenance and proactive safety management while overcoming the practical limitations of instrumented wheelsets and offering a robust, fleet-scalable alternative for the railway industry. Full article

The objective of this work is to propose a novel mechanical model of under ballast mats (UBMs) that can replicate the phenomenon of energy dissipation under static loads. UBMs installed in the ballasted track structure can reduce the levels of vibration emitted by the railway system to the surrounding environment, affecting both people and the natural and built environment. A particular feature of UBM isolators is energy dissipation, which is manifested in load-deflection graphs in the form of so-called hysteresis loops. Notably, the hysteresis loop occurs not only under dynamic loads but also in the case of static loading. The constitutive equations of the UBM model will be formulated as a nonlinear set of ordinary differential equations. The parameters of the constitutive relations will be selected based on an optimization procedure to match the results of integrating the differential equations describing the theoretical model to the results of experimental tests of UBMs in the static range, in accordance with European standard EN 17282:2020-10. Full article

While railways are critical for transportation, their expansive networks spanning thousands of kilometers pose significant challenges for conventional structural health inspection and maintenance. Recent advancements in sensors and artificial intelligence technologies have led to a substantial growth in the body of research proposing innovative approaches for Railway Track Structural Health Monitoring (RTSHM) to enhance safety and operational efficiency. This work aims to synthesize the current RTSHM research landscape to explore mainstream and emerging directions and identify advancements, challenges, and opportunities in this field. Through the hybrid systematic review using bibliometrics analysis and topic modeling, core research themes emerged, from developing sensor and data acquisition techniques as the foundation, to be combined with AI-based methods for fault detection and prediction. These predictions are leveraged for predictive maintenance through degradation modeling, supplemented with information from dynamic response assessment and performance optimization, and the ultimate goal is integration of RTSHM for operational safety assessments and risk-based decision-making. While technologically advanced, current research predominantly focuses on detecting discrete defects, thereby neglecting the holistic management of the track system. This fragmentation contributes to a complex and often siloed landscape for infrastructure management, emphasizing that RTSHM remains in a critical developmental stage. Consequently, the development of smart railway, integrated with intelligent data collection devices, deep learning technologies, and innovative operational platforms, represents a challenging yet promising direction for future research. These advancements are anticipated to foster safer, more efficient, and sustainable railway systems worldwide. Full article

Due to its effective noise reduction, the semi-enclosed noise barrier is increasingly being applied in the construction of high-speed railways. However, there is still a lack of systematic research on the wind load distribution characteristics under natural crosswind, especially for the complex aerodynamic behavior of the intersection section of multi-line bridges. Therefore, the wind load distribution characteristics on the surface of the sound barrier under crosswind conditions are explored within the engineering context of a semi-enclosed acoustic barrier at the junction of a single-track bridge and a three-track bridge, using a combination of wind tunnel testing and numerical simulation. A rigid-body model with a geometric scale of 1:10 is established for the wind tunnel test. The wind load distribution characteristics of the two acoustic barriers are analyzed from the perspectives of mean wind pressure, pulsating wind pressure, and extreme wind pressure, respectively. FLUENT 2022 software is utilized to model the flow field characteristics of the sound barrier under two working conditions: windward and leeward. The results show that under the action of crosswind, the surface wind load of the sound barrier at the junction of the single/three-line bridge is very prominent, the maximum negative pressure shape coefficient is −4.516, and its distribution is dominated by negative pressure; that is, the sound barrier mainly bears suction. Compared with the semi-closed sound barrier on the single-track bridge, the extreme wind pressure at the semi-closed sound barrier on the three-track bridge and the junction of the two is more significant, which shows that this kind of area needs special attention in wind-resistant design. Full article

The construction of long-span continuous steel truss rail-cum-road bridges for high-speed railways presents significant challenges, primarily due to structural complexity, stringent deformation tolerances, and intricate construction sequences. This paper presents a comprehensive construction control methodology developed and implemented for such bridges. Using a real-world bridge project in China as a case study, the methodology integrates mechanical analysis of key construction stages, deformation prediction, real-time monitoring, and adjustment techniques. Furthermore, the application of machine learning (ML) for camber prediction is explored. Key findings indicate that the longitudinal displacement (X-direction) of the top chord at the upper-deck closure segment is highly sensitive to temperature variations, with a differential of about 10–12 mm observed under a 15 °C temperature change. Consequently, closure welding is recommended near the design reference temperature, with field measurements guiding final fit-up adjustments. A comparative analysis between ML predictions and theoretical methods for member elongation revealed that the Extra Trees (ET) model and K-Nearest Neighbors (KNN) model achieved excellent accuracy, with errors within 2 mm, demonstrating the feasibility of ML-based camber setting. The proposed integrated approach, combining finite element analysis, real-time monitoring, and detailed sensitivity analysis of closure accuracy, proves effective in ensuring structural safety and meeting precise alignment requirements, particularly for high-speed railway track. The findings offer valuable insights for the construction control of similar long-span steel truss rail-cum-road bridges. Full article

The salt lake and saline–alkali soil regions of high plateaus are characterized by widespread Alkali–silica reactive (ASR) aggregates, which severely threaten the durability of constructed infrastructure, including railways, highways, and buildings. The research systematically investigates the uniaxial compressive mechanical behavior and stress–strain constitutive relationship of high-performance concrete (HPC) with ASR mitigation measures (performance grades C40, C45, C50, and C60) after ten years of immersion in a standard alkali solution. A corresponding three-dimensional random aggregate mesoscopic concrete model was developed, and mesomechanical numerical simulations were performed to explore the failure process, failure patterns, and underlying mesoscopic damage mechanisms of the specimens. Results show that While the uniaxial compressive strength and elastic modulus of HPC show an expected increase with the concrete strength grade following long-term alkali exposure, both properties demonstrate a clear decline as the equivalent alkali content rises. Comparing and analyzing the C50 specimens of different admixtures, it was found that the air-entraining agent provided the most effective ASR suppression and obtained the highest uniaxial compressive strength compared with the rust inhibitor. By normalizing the stress–strain curves, the long-term constitutive behavior of HPC under alkali corrosion was summarized. Furthermore, mesoscopic model visualizations indicate that cracks initially appear in the mortar and gradually propagate inward during loading, leading to compressive failure characterized by diagonal cracks. Tracking the mesoscopic damage patterns within the specimens demonstrates that microcracks originate in the mortar and progressively extend through aggregates, revealing the underlying micro-damage mechanism. By studying the SEM-EDS images, it is found that HPC with a specific mix ratio designed in this paper can effectively inhibit the ASR effect, and it still has good corrosion resistance in long-term alkali immersion. Full article

Squat is a type of rail defect that frequently poses challenges for railway tracks, as they generate dynamics and accelerate track degradation. Detecting rail squats is resource-intensive, given their relatively small size compared to the railway track. Often, by the time they are detected, damage has usually already occurred in other track components. Currently, rail squats are primarily detected using dedicated railway measurement vehicles. There has been a recent trend in research towards utilizing trains in regular traffic to monitor the condition of railway tracks. However, there is a lack of research and general guidelines regarding the optimal placement of accelerometers or sensors on trains for squat detection. In this study, multibody simulation software GENSYS Rel.2209 is employed to simulate a passenger train traversing rail squats under various scenarios, with each scenario characterized by a distinct set of typical feature values for the squats. The results demonstrate that the front wheel set, positioned closest to the defects, exhibits the highest sensitivity to vertical accelerations. Squat length is much more sensitive than depth for detection at typical speeds, and accelerometers on bogies or the car body require speeds below 40 km/h to ensure reliability. The acceleration response mechanism during squat traversal is explored, revealing the effects of varying squat geometries and train speeds. This finding enables a detection method capable of locating squats and estimating their length with over 90% accuracy. Practical recommendations are provided for optimizing squat detection systems, including squat width detection, sensor selection criteria, and suggested train speeds. It offers a pathway to detect squat more efficiently with optimized installation locations of accelerometers on a train. Full article

High-speed railway turnouts play important roles in the efficient operation of trains. However, the complex mechanical structure of turnouts and insufficient displacement of switch rails under dynamic conditions create a point of vulnerability for high-speed railways. The insufficient displacement of switch rails in high-speed railway No. 18 turnouts critically impacts operational safety. This study establishes a coupled finite element model of the switch rail and sliding track bed plate to analyse the effects of the friction coefficient and wheel–rail force. The results show that without considering the force of the iron block, the maximum insufficient displacement of a switch rail occurs at sleeper No. 27, and the maximum insufficient displacement increases linearly with the friction coefficient, with a regression coefficient of 1.02. When considering the wheel–rail force of the train, the maximum insufficient displacement of the switch rail occurs at sleeper No. 25, with the regression coefficient reduced to 0.67. Through dynamic and static tests and a case analysis, the influence of wheel–rail force on the insufficient displacement of a switch rail is verified. The results show that the application of a lateral wheel–rail force in the model significantly reduces the insufficient displacement of the switch rail, with an improvement of more than 90%. This study can significantly improve the optimisation of turnout design and the operational efficiency of a railway network. Full article

Railway braking efficiency hinges on the thermomechanical conditions at the wheel-rail interface. Frictional heating during operation causes significant temperature fluctuations, directly impacting braking performance in rail vehicles. Evaluating these effects is important for developing infrastructure and components adapted to environmental conditions. Several studies have explored the influence of temperature on components such as the brake disc or the wheel; little attention has been paid to the thermal conditions of the rail itself. This paper examines the effect of rail temperature on the braking behavior and energy consumption of a railway vehicle. Using a 1:20 railway track, rail segments were subjected to four temperatures (28.5 °C, 40.0 °C, 49.9 °C, 71.0 °C) by heating with Nichrome wire, and tests were performed at three speeds (0.75, 1.00, and 1.30 m/s). The results show that higher rail temperatures improve wheel-rail adhesion up to an optimum point (40.0 °C), beyond which performance deteriorates. In contrast, tests at 71.0 °C showed reduced braking efficiency, despite lower electrical current peaks, indicating a non-linear thermal response. Full article

Railway tracks at bridge approaches experience significant vertical stiffness transitions, leading to adverse effects such as settlement and increased dynamic loads, accelerating track degradation. This study explores various structural solutions, including geosynthetics, reinforced ballast, transition slabs, under sleeper pads (USPs), under ballast mats (UBMs), jet grouting, and special rail fasteners. Despite their application, these solutions often fail due to their static nature. This paper introduces an adaptive approach using special rail fastenings with real-time adjustable stiffness. This system dynamically modifies rail support characteristics based on train speed and track conditions, improving track durability, ride quality, and maintenance strategies. The findings demonstrate the potential of adaptive systems to enhance railway infrastructure performance. Full article

Field measurements of ground vibrations were conducted along the Paris–Brussels high-speed railway (HSR) to systematically analyze vibration characteristics generated by embankment and cutting sections. Utilizing the 2.5D finite element method (FEM), numerical models were developed for both earthworks to evaluate the influences of design parameters on ground vibration responses. Results demonstrate that train axle load dominates vibration amplitude in the near-track zone, while the superposition effect of adjacent wheelsets and bogies becomes predominant at larger distances. Vibration energy attenuates progressively with increasing distance from the track, with medium- and high-frequency components decaying more rapidly than low-frequency components. The dominant vibration frequency is determined by the fundamental train-loading frequency (f₁), which increases with train speed. Distinct attenuation patterns are identified between earthwork types: embankments exhibit a two-stage attenuation process, whereas cuttings undergo three stages, including a vibration rebound phenomenon at the slope crest. Furthermore, greater embankment height or cutting depth reduces ground vibrations, but beyond a critical threshold, further increases yield negligible benefits. A higher elastic modulus of the embankment material correlates with reduced vibrations, and steeper cutting slopes, while ensuring slope stability, contribute to additional mitigation. Full article

In Europe’s changing transport landscape, railways are experiencing a renaissance, driven by environmental advantages, cost efficiency, growing demand, and political support. Yet this growth also exposes major challenges, especially regarding network capacity, infrastructure availability, maintainability, and the cost-effectiveness of maintenance. This study focuses on these aspects, analyzing their interdependence and their impact on building a more resilient and efficient rail system. A prediction model, based on historical measurement data, is developed to forecast track behavior and assess an alternative maintenance strategy. This maintenance strategy uses novel approaches to define maintenance-triggering intervention values. The overarching goal of this work is to contribute to the improvement of predictive maintenance approaches. Findings show no technical or economic justification for the continual reduction of section lengths, a practice common in heavily used networks. Instead, results demonstrate that with improved planning and long-section tamping, both track quality and service life can at least be kept at the same level or even be enhanced. Longer section lengths positively influence performance by lowering running meter costs and potentially reducing operational downtime in the long run. To validate these interrelationship, future research will integrate a model that explicitly considers the costs of operational hindrances. Full article

Ensuring the safety and reliability of freight wagons requires continuous monitoring of couplings such as hooks and buffers, which are prone to stress, wear, and misalignments. This paper proposes a vision-based 3D monitoring system which uses an RGB-D camera and a computer vision pipeline to estimate angular excursions and longitudinal displacements of wagon couplers during train operation. The proposed approach combines depth-based reconstruction with a normalized cross-correlation tracking algorithm, providing geometric measurements of coupling motion without physical contact. The system architecture integrates real-time acquisition and post-processing analysis to 3D reconstruct the geometric characteristics of wagon couplings under field conditions. Experimental tests performed on a T3000 articulated wagon allowed us to measure an angular excursion of approximately 9.8° for the hook and a longitudinal displacement of 17 mm for the buffer. The results show robustness and suitability for embedded implementation, supporting the adoption of vision-based techniques for safety monitoring in railways. Full article

To mitigate and control the seismic damage risk of high-speed railway bridges and enhance their post-earthquake reparability, a prefabricated multi-layer parallel-connected slit steel plate shear damper is proposed by utilizing the energy absorption capacity of flexure–shear coupled deformation in dampers. A theoretical model for calculating the stiffness and load-bearing capacity of the proposed damper was established and validated through detailed finite element simulations. The results demonstrate that the damper exhibits stable energy dissipation efficiency under cyclic loading, along with a gradual reduction in post-yield stiffness. Subsequently, a numerical model of the high-speed railway track–bridge-damper systems (HSRTBDS) was developed, incorporating the contribution of the proposed damper to quantify its control over the seismic response of the HSRTBDS. The findings indicate that the damper effectively reduces the seismic responses of the girders, rail fasteners, and track slabs, with a maximum deformation reduction exceeding 30% in the supporting structures. However, the deformation and damage of the bridge piers slightly increased, though they remained within acceptable safety limits. The damper showed limited influence on the damage to rails, fasteners, and shear key slots. Overall, the effectiveness of the proposed damper in controlling the structural response of HSRTBD has been demonstrated and validated, providing insights for the seismic design of high-speed railway bridges in high-intensity seismic zones. Full article