When a shortcircuit fault occurs between the positive pole of a highvoltage DC circuit for a train and its carbody inside the station in a straddle seat monorail DC traction system, this causes the carbody grounding relay (GR) of all trains inside the station to actuate and the circuit breakers of the train to trip. Meanwhile, this also triggers multiple 64D grounding protection actions and trips the circuit breaker of the DC feeder. The fault results in a loss of power to the DC traction system. It is necessary to identify the faulty train and restore the normal power supply of the DC traction system as soon as possible to reduce the impact of the accident. First, the study analyzed characteristic differences in the amplitude of the grounding current and negative receiving electricity current for a faulty train compared to a normal train when a shortcircuit occurred between the positive circuit and the carbody based on the equivalence model of the DC traction bipolar power supply system for straddle monorail transportation. Second, an identification method for a faulty train is proposed based on a comparison of the grounding current and negative current amplitude. The identification procedure is activated when the grounding current exceeds a predetermined threshold. If the grounding current amplitude is greater than the negative current, the train is identified as faulty; otherwise, it is considered to be in a normal state. The accuracy and effectiveness of this method were validated through MATLAB simulations and field tests. The proposed approach is simple, practical, and highly reliable, providing a strong safeguard for the safe operation of straddleseat monorail systems.

To verify the effects of rail damping devices in the rail corrugation treatment for vibration reduction tracks, rail damping devices were added to a laddertype sleeper track and a steelspring floating slab track, respectively, in this study. The vibration and trackside noise characteristics of the two vibrationreduction tracks were reported, and the development of rail corrugation was tracked. The results show that the rail damping devices installed on the laddertype sleeper track can achieve positive effects in vibration and noise reduction in a wide band range, which can reduce rail vibration and trackside noise by 9.7 dB and 11 dB (A), respectively. The rail damping devices installed on the steelspring floating slab track can reduce rail vibration and trackside noise by 8.3 dB and 3 dB (A), respectively, within their operational frequency range. Longterm tracking tests revealed that the installation of rail damping devices can at least halve the rate of rail corrugation development on vibration reduction tracks.

This study investigated the thermal environment and comfort in elevated subway stations in Wuhan, determined passenger thermal comfort ranges, and examined the impact of station architectural forms on passenger comfort during typical summer days at five representative stations. The research combined instrumental measurements with subjective surveys. Linear fits were applied to the standard effective temperature (SET*) and mean thermal sensation vote (MTS) at two stations, and these were compared with the predicted thermal sensation (PTS) to determine passengers' thermal sensation ranges. The results indicated that the stations tended to fail to meet the requirements of the "Code for design code (GB 501572013)". Additionally, indoor air temperatures were frequently too high, relative humidity largely met the standard, and air velocities in most stations were low. Survey data suggest that station design significantly affects passenger thermal comfort, revealing a preference for open platforms during summer. Moreover, the PTS curve remained consistently higher than the SET*MTS curve, indicating that passengers' summer thermal adaptations exceeded expectations. Finally, common shading, ventilation, and thermal environment improvement measures for regions with hot summers and cold winters were proposed alongside theoretical insights for enhancing thermal comfort and supporting green transitions in elevated subway stations in Wuhan.

To monitor rail health in realtime and provide early warning of rail fracture damage, this study proposes a broken rail detection method that combines ultrasonic guided wave detection and variational mode decomposition signal processing technologies. The system workflow and hardware circuits of each module were designed and constructed according to the requirements for rail fracture detection. A threedimensional rail model was created using finite element simulation software to analyze the propagation speed of ultrasonic guided waves within the rail and assess the feasibility of the noise reduction technique. The system's effectiveness was verified through equipment installation tests on Suzhou Metro Line 5, where artificially simulated rail fractures were used. The results demonstrated that, upon rail fracture, the system achieved a remote alarm time of 3 minutes and the defective positioning error is 1.1%, providing a reliable approach for rail fracture monitoring.

In response to the problems of insufficient crosslevel, crossstandard, and crossregional integration in the development of multilevel rail transit in the Guangdong Hong Kong Macao Greater Bay Area, empirical analysis methods were used to study the deepseated influencing factors from the aspects of policy system design, planning and construction, and coordination of operating entities. On the basis of analyzing the current situation and existing problems of multilevel rail transit development in the Guangdong Hong Kong Macao Greater Bay Area, this paper explores the successes, failures, and lessons learned from the development of multilevel rail transit in urban agglomerations at home and abroad. It proposes countermeasures such as establishing an integrated integration system mechanism and policy norms, strengthening integrated planning and construction management, promoting the integration of comprehensive transportation hubs, improving land support policies and investment and financing supporting policies, and establishing a multilevel rail transit operation enterprise alliance in the Greater Bay Area. The research results can provide a reference for the decisionmaking of multilevel rail transit integration in the Guangdong Hong Kong Macao Greater Bay Area.

This study explores the applicability of oblique bolt joints in smalldiameter shield tunnel beam melting (TBM) tunnels, clarifying their mechanical properties and damage mechanisms. A segment structure with an external diameter of 6.2 m and a thickness of 350 mm was utilized as a prototype for conducting bending performance tests on steel fiber concrete segments with oblique bolted joints under four different horizontal axial force conditions. The analysis focused on the deformation characteristics and flexural performance of the segment joints across varying axial force levels, as well as the failure processes and mechanical properties under failure conditions. The results showed that the higher the axial force on the segment joints, the higher the joint stiffness, requiring larger bending moments to open the joint. In other words, the joint axial force can be actively increased by increasing the bolt preload or by applying annular prestressing to improve the joint stiffness. Compression of the sealing gasket under joint axial force results in stress concentrations within the sealing groove. Therefore, selecting an appropriate sealing gasket or optimizing the sealing groove structure is essential in the design process. The study also found that enhancing the compressive strength of the top concrete and reducing the insertion angle of the oblique bolt significantly improve joint bearing capacity. These findings provide valuable guidance for the design of segment joints.

To predict the vibration response of buildings along subway lines quickly and reasonably, a building structural system is decomposed into two parts, namely, a propagation structure and a response structure, based on the theory of mechanical mobility. The bearing structure is assumed to be a beam element model, and the slab structure is considered a plate element model. The mobility formula and the corresponding matrix expressions for each unit system are derived, and a traininduced structural vibration response model is constructed. The reliability and accuracy of the model are validated through onsite testing, showing that the predicted structural responses align well with measured vibrations in both time and frequency domains. In the frequency domain, the maximum error of the center frequencies of each 1/3 octave band does not exceed 5 dB, indicating that the proposed traininduced structural vibration response model can quickly and effectively predict the structural vibration response and that the outcomes can provide theoretical support for vibration prediction along subway lines.

In response to the increasing speed and strict requirements for bridge smoothness in the design of railelevated bridges, this study is based on the design of the elevated bridge of Beijing Metro Line 22 at a speed of 160 km/h. A new type of adjustable height device is developed and designed based on a lowmeltingpoint alloy as the height adjustment medium. A series of experimental studies are conducted, including the structural design of the device, indoor temperature and pressure tests, fullscale pressure adjustment performance tests of the compression shear machine, and onsite beam erection tests. The findings indicate that the new adjustable height device enables stepless bidirectional height adjustment with a rapid adjustment speed, completing height changes within 30 s. The device achieves millimeterlevel accuracy, and the alloy demonstrates excellent stepless adjustment performance and compression stability once cooled and solidified. The accuracy and stability of this adjustable height device not only ensure the smoothness of elevated bridge beams but also offer valuable guidance for engineering applications, such as replacing deteriorated bearings and adjusting for differential settlement in bridges.

The conventional subway line design method cannot address the issues of a large amount of demolition, complex construction, high risk, and high cost in the densely built areas under construction. This article innovates a line design method that combines a special scissors crossover with a curved islandtype misaligned platform, which not only meets the design needs of related disciplines such as architecture, structure, signal, track, train operation, and line but also allows subway lines to avoid dense buildings around the station flexibly. The results indicate that this innovative route design method can reduce demolition, increase construction clearance, reduce open excavation scale, reduce construction difficulty and risk, and reduce engineering investments. It provides technical guidance for areas with dense buildings, as well as demolition and construction difficulties around subway stations. The application to practical engineering cases demonstrates that this innovative line design method can yield economic, technical, and social benefits.

In the overall structure of a shield tunnel, the joint of the pipe segments is the weakest part of the waterproofing system, and its waterproofing performance directly influences the stability and service life of the entire tunnel. With continuous innovation and changes in structural design and construction methods, the occurrence of water leakage or sealing gasket damage at the joints of pipe segments has become increasingly severe. Therefore, research and optimization of waterproofing performance are crucial. This study begins with the waterproof principle of elastic sealing gaskets and deeply analyzes the factors that affect joint leakage, based on which specific optimization measures were proposed for the waterproof performance of pipe joints. Finally, to verify the actual effectiveness of these optimization measures, empirical research was conducted on a new type of shield tunnel project in Jiangxinzhou, Nanjing. The main conclusions of the study are as follows: the physical properties and durability of EPDM gaskets must strictly comply with regulatory requirements; The adhesive work of the onsite sealing gasket and the tensile deformation of the onsite pipe segment assembly on the sealing gasket is essential factors impacting the leakage of water at the joint; The solid section structure at the corner of a largediameter high water pressure shield tunnel requires to be optimized to avoid issues such as corner accumulation and stress concentration caused by the crosssectional size of the sealing gasket; The monitoring results after the tunnel is completed indicate that the optimized shield tunnel not only has good forming quality but also has a much better waterproof effect than traditional shield tunnels. This study not only provides a theoretical basis and practical guidance for the waterproof design of shield tunnel segment joints but also provides a valuable reference and inspiration for similar projects.