Narrow Results

Infrastructure constructions promote the flow of production factors across regions and improve the information environment of the region. This paper investigates the impact of infrastructure construction, proxy as the opening of high-speed railway (HSR), on corporate cost stickiness. The results show that the opening of HSR is beneficial to decreasing corporate cost stickiness, and this positive impact is robust after IV estimations and placebo test. Moreover, we find some evidence that the opening of HSR can promote the frequency and quality of analysts’ survey, and improved the corporate information environment. Further analyses show that the positive impact of HSR on corporate cost stickiness is more pronounced for firms with serious information asymmetry and weaker corporate governance. Then after the effect of the HSR on stickiness of different type corporate cost was tested, the results showed that the impact of the opening of HSR on corporate cost stickiness mainly exists in manager perks and salary-welfare. Based on the introduction of HSR, our findings clarify and highlight the role of infrastructure construction on corporate asymmetric cost management behavior.

The hangers represent the crucial load-bearing component of arch bridges and are susceptible to dynamic vehicle load. However, little effort has been made to carry out dynamic analysis of arch bridge hangers under high-speed train loads. This paper presents an investigation of the dynamic behavior of the arch bridge subjected to high-speed train with emphasis on the flexible hangers, using train–bridge interaction simulation and field measurement data. Coupled train–bridge system model composed of three-dimensional train model, bridge model, and wheel–rail interaction model is established to account for hanger transverse vibration, spatial train loading, and track irregularity excitation, among others. Vibration data of bridge components including the hanger are measured through field test on a typical high-speed railway tied-arch bridge. A total stress-based dynamic amplification factor is subsequently proposed to describe the effect of hanger transverse vibration. The influence of significant parameters such as train speed and track irregularity on the dynamic effects of hangers is examined by the experimentally validated train–bridge interaction model. It is found that the dynamic responses of the hangers are considerably different from bridge global responses. In-plane and out-of-plane transverse vibrations of the hanger result in a large increase in the hanger dynamic effects which prove to be sensitive to train speed, track irregularity, train loading position, etc. Moreover, the dynamic amplification factor formula in the current high-speed railway code may not be sufficient to characterize the dynamic amplification of hangers under operating conditions.

High-speed railways are “lifeline projects” that shoulder the heavy responsibility of transporting relief supplies and medical forces for the first time after earthquakes. To ensure the train’s safety after earthquakes, it is of great urgency to ascertain a post-earthquake speed threshold. To that end, a target model for seismic irregularity emerges as a key parameter. In this paper, a null phase assumption-based technique for the mutual conversion between evolutionary power spectral density and non-stationary signal was proposed. Taking a high-speed railway track-bridge system as the research object, the target model of seismic irregularities was constructed based on the proposed technique. The rationality of the target model of seismic irregularities was verified, and the construction parameter settings were discussed. Moreover, a simplified frequency-domain fitting method for the target model of seismic irregularities was proposed based on the spectral decomposition theory. According to the research findings, the null phase assumption-based technique is capable of performing interconversion between seismic irregularity and its evolutionary power spectral density with satisfactory accuracy. It is recommended to set the minimum number of seismic irregularities, spatial sampling interval, hop size, and length of window function as 50, 0.25m, 1, and 40 to 100, respectively.

Topographic effects significantly influence the propagation of seismic activity; however, research on the differences between mountainous and plateau terrains remains scarce. This paper focused on the 2008 Wenchuan earthquake, analyzing a five-span high-speed railway simply supported by a bridge through dynamic time-history analysis. Stations were categorized into mountainous and plateau groups based on their average shear wave velocity for the top 30m ($V_{s30})$ values and elevation, aiming to explore the impact of terrain differences on seismic actions by comparing structural responses between the two groups. This study revealed an exponential relationship between structural responses and the rupture distance ($R_{\mathrm{\text{rup}}}$)/peak ground acceleration (PGA), with a rapid decrease in response when $R_{\mathrm{\text{rup}}}$/PGA was below 100 and subsequent stabilization. Additionally, the sites were segmented into three zones according to the epicentral distance. The findings highlighted that the average PGA value of the mountain group was 2.7 times that of the plateau group in Region I, and the value decreased to 1.93 times that in Region II. However, the average PGA value of the plateau group slightly exceeded that of the mountain group in Region III. By comparing the PGA values of stations with similar fault distances within these regions, it was discovered that elevation could amplify seismic motion up to 4.59 times for smaller fault distances, with minimal amplification effects observed for larger fault distances. Finally, by examining damage to key components such as rails, beams, bearings, and piers and employing the kriging interpolation method to produce a regional seismic response cloud map, instances of high-speed railways constructed post-Wenchuan earthquake serve as evidence to corroborate the findings.

A wind warning system (WWS) is designed to ensure the operational safety of trains amid various wind environments. The system integrates the Internet, cloud computing, and virtual instrumentation technologies to automatically collect wind speed data and intelligently output alert information. To precisely predict the wind speed, a hybrid intelligent algorithm termed VMD–SSA–GRU comprising variational mode decomposition (VMD), sparrow search algorithm (SSA), and gated recurrent unit (GRU) is proposed and integrated into the WWS. Besides, the quantile regression (QR) is applied to wind speed uncertainty estimation, and the probability density functions of partial intervals are further evaluated by an improved kernel density estimation method. Two typical wind speed datasets (typhoon and normal wind conditions) measured by the WWS are used for validation of the applicability of the developed forecasted model. Through comparison to seven single and four combined models, the developed model presents the highest forecast accuracy in both definitive and uncertainty predictions even in typhoon wind conditions. The study demonstrates that the WWS integrated with the proposed hybrid intelligent algorithm can provide sensible warning for the safety of train operation.

The girder end region is one of the weak points affecting operational stability and safety on kilometer-level railway bridges, featuring continuous track irregularities spanning over tens of meters, and often suffering from substandard ballast quality. Addressing the two issues, taking a kilometer-level span suspension bridge as a case, the local characteristics of dynamic track irregularities were analyzed at the girder end regions of long-span bridges. First, the distribution of track dynamic irregularities was analyzed based on the results from special tests conducted under extreme environmental temperatures. Then, the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) method was introduced to dissect the intrinsic properties within the original signals, and the local characteristics of track dynamic irregularities with spatial wavelengths concentrated within 20m have been well revealed. Based on the principle of maximum entropy, these local fluctuation characteristics can be assessed through the standard deviation of track geometry deviations calculated in 10m unit sections. Ultimately, through fractal analysis, a negative correlation was identified between the fractal dimension and the stiffness of the ballast bed, and it was found that the ballast state on the approach bridge side is notably deteriorated, while that on the main bridge side remains in a great state. The findings can help assess the service condition of girder end structures based on dynamic detection results, providing a reference for the operation and maintenance of kilometer-level span railway bridges.

The acceleration of the vehicle body is closely related to the wavelength components of the track, making the design of track alignments crucial for enhancing the comfort of high-speed rail travel. However, research on the effects of long-wavelength deformations on alignment design and their impact on vehicle dynamics remains limited, and existing methodologies fail to effectively calculate the wavelengths of traditional alignments, which consist of linear segments and vertical curves. This study introduces a novel approach for computing long-wavelength track alignments and vehicle response wavelengths using signal decomposition and the Hilbert transform. A comprehensive program is developed to analyze the relationship between alignment and vehicle response wavelengths through correlation coefficients and coherence functions. The results show that traditional alignments have predominant wavelengths exceeding 1 000m, which exhibit negligible correlation with vehicle response due to the dominant influence of alignment curvature. In contrast, Fourier series-designed alignments demonstrate a significant correlation with vehicle response, particularly under high-speed conditions. Quantitatively, vehicle response wavelengths are found to range from 1000m to 5000m, with Fourier series alignments effectively reducing dynamic impacts. These findings highlight the potential of the proposed approach in optimizing track design for challenging railway sections, providing valuable guidance for improving high-speed railway operations.

Simulated HAZ continuous cooling transformation (SH-CCT) diagram presents the start and end points of phase transformation and the relationships of the microstructures of HAZ, temperature and cooling rates. It is often used to assess the weldability of materials. In this paper, a weathering steel Q345C which is widely used in the bogies manufacturing was studied. The cooling times from 800${}^{\circ }$C to 500${}^{\circ }$C ($t_{8/5}$) were from 3 s to 6000 s, aiming to study the microstructures under different cooling rates. Different methods such as color metallography were used to obtain the metallography images. The results show that ferrite nucleates preferentially at the prior austenite grain boundaries and grows along the grain boundaries with a lath-like distribution when $t_{8/5}$ is 300 s. Austenite transforms into ferrite, pearlite and bainite with decreasing $t_{8/5}$. Pearlite disappears completely when $t_{8/5}=150$ s. Martensite gradually appears when $t_{8/5}$ decreases to 30 s. The hardness increases with decreasing $t_{8/5}$. The SH-CCT diagram indicates that the welding input and $t_{8/5}$ should be taken into consideration when welding. This work provides the relationships of welding parameters and microstructures.

Railway system as an important transportation pattern can improve regional economic growth and accelerate the development of transportation structure. In this paper, we propose an evolving model to describe the evolutionary mechanism of high-speed railway system by using hypernetwork theory. The stations are represented as nodes while the lines are represented as hyperedges. The evolving process includes two ingredients: growing and linking which is driven by both random and preferential attachment. We analytically deduce the node hyperdegree distribution which is shown to follow a shifted power-law distribution. Furthermore, we test the impact of parameters on the model. Then the empirical investigations of China Railway High-speed (CRH) are demonstrated which can be explained by the proposed model. The model can reveal the macro characteristics of railway system and provide reference for the further development of high-speed railway.

This paper studies the effect on the existing railway which is made by the train with 216 km/h high-speed when running across over the existing railway. The influence on the railway carrying capacity which is made by the transportation organization mode of the existing railway is analyzed under different parking modes of high-speed trains as well. In order to further study the departure intervals of the train, the average speed and the delay of the train, an automata model under these four-aspects is established. The results of the research in this paper could serve as the theoretical references to the newly built high-speed railways.

Different from the conventional logistics service network design problem, we design a fast logistics service network based on high-speed railway. An integrative optimization model which is applicable for solving practical problems is established. This paper simultaneously considers three subproblems: Train timetabling, freight flow assignment and electrical multiple units (EMU) routing plan, in which the objectives are simultaneous to minimize the total train travel time, the operation cost and transportation cost of freight transport, the number of freight EMU and the number of maintenance tasks. The constraints imposed in the model include space-time path resource assignment restriction, node operation capability, train safety interval time, train connection time restriction, freight service time window, train loading capacity restriction and EMU routing restriction. Based on the thoughts of divide and conquer, the original problem is decomposed by using the decomposition mechanism of the Lagrange relaxation algorithm to solve the integrated optimization model. To verify the feasibility and effectiveness of the model and algorithm proposed in this paper, a case study is conducted based on Harbin Dalian high-speed railway.

Accurate prediction of train delay recovery is critical for railway incident management and providing passengers with accurate journey time. In this paper, a two-stage prediction model is proposed to predict the recovery time of train primary-delay based on the real records from High-Speed Railway (HSR). In Stage 1, two models are built to study the influence of feature space and model framework on the prediction accuracy of buffer time in each section or station. It is found that explicitly inputting the attribute features of stations and sections to the model, instead of implicit simulation, will improve the prediction accuracy effectively. For validation purpose, the proposed model has been compared with several alternative models, namely, Logistic Regression (LR), Artificial Neutral Network (ANN), Support Vector Machine (SVM) and Gradient Boosting Tree (GBT). The results show that its remarkable performance is better than other schemes. Specifically, when the error is extended to 3min, the proposed model can achieve up to the accuracy of 94.63%. It proves that our method has high value in practical engineering application. Considering the delay propagation of trains is a complex process, our future study will focus on building delay propagation knowledge base and dispatcher experience knowledge base.

A linear wheel–rail interaction model for the vehicle–bridge coupling system is presented in this paper. The vehicle subsystem is modeled by the rigid-body dynamics method, the bridge subsystem by both the direct stiffness method and superposition method, and the wheel–rail interaction by the "corresponding assumption" and simplified Kalker creep theory. Based on the above modeling for the wheel–rail interaction system, linear simultaneous equations are established and solved. As a case study, the response of the Pioneer train traversing a 24 m simply–supported girder bridge is calculated. The proposed analysis procedure is validated through comparison of the calculated results with the measured ones. Also, some vibration characteristics of the system are discussed.

With the rising speed of high-speed trains, the aerodynamic loads become more significant and their influences on the hunting stability of railway vehicles deserve to be considered. Such an effect cannot be properly considered by the conventional model of hunting stability analysis. To this end, the linear hunting stability of high-speed railway vehicles running on tangent tracks is studied. A model considering the steady aerodynamic loads due to the joint action of the airflow facing the moving train and the crosswind, is proposed for the hunting stability analysis of a railway vehicle with 17 degrees of freedom (DOF). The key factors considered include: variations of the wheel–rail normal forces, creep coefficients, gravitational stiffness and angular stiffness due to the actions of the aerodynamic load, which affects the characteristics of hunting stability. Using the computer program developed, numerical calculations were carried out for studying the behavior of the linear hunting stability of vehicles under steady aerodynamic loads. The results show that the aerodynamic loads have an obvious effect on the linear critical speeds and instability modes. The linear critical speed decreases monotonously as the crosswind velocity increases, and the influences of pitch moment and lift force on the linear critical speed are larger than the other components of the aerodynamic loads.

Operation safety of high-speed trains is dependent on their vibration characteristics, which vary with bridge deformation. This paper studies the influence of bridge pier settlement and girder creep camber, which are two typical types of long-term bridge deformation, on the vibration of high-speed trains. To this end, an analytical approach is presented to link the bridge deformation with railway track deformation; the track deformation is used to analyze the vibration of the CRH2 high-speed train in China. The vibration analysis results are validated using the in-situ measurement data. The present study shows that bridge pier settlement greatly affects the vertical acceleration, derailment coefficient and wheel unloading rate of the high-speed train; incorporating bridge girder camber aggravates the vibration of the train–bridge system. The threshold of bridge pier settlement is suggested to be 11.1mm for trains moving at 350km/h with regard to the code-specified vibration limit. This study has significant implications for the design and operation of high-speed railways.

This paper presents a unified framework for dynamic analysis of vehicle-bridge interaction (VBI) systems using a commercial finite element software suite (ABAQUS$\text{®}$). This framework can provide bridge designers and engineering practitioners with a general platform to analyze the coupled system with high modeling efficiency and accuracy in modeling and outputting. Moreover, it has readily available nonlinear material/element models and nonlinear dynamic analysis functions for complex structures. This analysis framework was first validated with a classical VBI problem involving a sprung mass moving on a simply supported beam, whose closed-form solution is readily available. Validation for the application on complex structure was then presented with a typical 16-car Japanese high-speed train (Shinkansen) and a three-block bridge. The cars comprised car bodies, bogies and wheelsets, which were all modeled as rigid bodies and which were connected with springs and dashpots. The bridge was modeled with typical three-dimensional solid elements. Interaction between wheelsets and tracks was realized using the penalty method. Rail irregularity was also considered in the analysis. The consistency between calculated dynamic responses and field experiment data of certain pre-specified observation points validated the proposed method. Furthermore, ease in analyzing VBI problems involving nonlinear material properties and with high spatial resolutions was demonstrated with a classical cracked beam problem: a point mass moving on a simply supported cracked beam. Both linear and nonlinear crack models were employed. The former model assigned crack surfaces with a mechanical contact property and showed its accuracy in comparison to the reference model. The latter assigned a nonlinear material model in crack-prone zones and illustrated the potential applicability to dynamic crack propagation simulation in VBI problems. The present framework was further applied to seismic response analysis of a train-bridge interaction system involving material nonlinearity and separation between track and wheel under a strong earthquake.

In order to predict more accurately the structural vibration and noise of elevated tracks induced by moving trains, a new prediction method based on the scaled model test is proposed in this paper. A 32-m simply supported box girder bridge used in the Beijing–Shanghai high-speed railway is selected as the prototype for designing and constructing a scaled model test with 10:1 geometric similarity ratio. Both experimental tests and finite element analyses were carried out to verify the similarity relationship between the model and prototype. The test result shows that the scaled model can predict the structural vibration and noise of the prototype, as long as the similarity constants between the prototype and scaled model are correctively determined. Furthermore, a standard finite element analysis model for the scaled model is built. Based on the sensitivity analysis, the model parameters for finite element analysis are updated by minimizing the errors between the measured and calculated modes. The computational results show that the updated model based on the local parameters partitioning works best, and the precision of the modal frequency calculated is noticeably improved after updating, with the average relative error reduced from 5.46% to 3.09%, and the difference of the peak values reduced from $0.358\times 10^3$m/s² to $0.189\times 10^3$m/s². The calculated dynamic response of the finite element model after updating is basically in line with experimental results, indicating that the updated model can better reflect the dynamic properties of the scaled box girder model. The updated finite element model is useful both for verification with the model test result and for reliable prediction of the dynamic characteristics of the prototype.

The multi-span simply supported (MSSS) box girder bridge is the most used structural form for the high-speed railway (HSR) in China. In structural design, it is required that the MSSS bridge system has high stiffness and low deflection under the operation loads. With the expansion of the HSR network to regions that are seismically active, the seismic performance of MSSS bridges in these regions is an issue of great concern. In this study, the performance-based earthquake engineering (PBEE) methodology originally developed to quantify the seismic performance of buildings and bridges has been adopted to quantify the seismic performance of the HSR MSSS bridges in China. Typically, a four-span MSSS bridge used in China’s Sichuan–Yunnan HSR lines has been extensively assessed by the PBEE approach. This study is the first of its kind to systematically identify and quantify the damage states, repair actions, repair costs and travel delay losses for China’s HSR MSSS bridge system. The results reveal that the financial loss from the MSSS bridge system is highly dependent on the anchorage capacity of the fixed bearings. Overall, the costs of travel delay outweigh those for structural repair. Most of the financial loss can be attributed to the functional loss of the track-slab components and bearings of the HSR MSSS bridge system.

With the development of high-speed railways, the double-line mode of ballastless tracks is being adopted increasingly worldwide. In some sections where subgrades need to be laid, this type of line mode is also applied above the subgrade, thus forming double-line track-subgrade structure. In this structure, the subgrade on one side of the double-line is subjected to the eccentric pressure of the load when the unidirectional train is running (the most common operating condition in actual operation). When the subgrade contains embankment layer, the complexity of the problem is increased. Therefore, a 1:4 scale test model of the double-line ballastless track-subgrade system was constructed in this paper in order to study the dynamic responses of the double-line track-subgrade structure with embankment layer under the unidirectional high-speed train loads. By considering the similarity of shear wave velocities, a new uniform dynamic similarity method was adopted to design the track, subgrade and foundation models. The effects of a series of sine waves with 1–30Hz excitation frequency and three kinds of loading modes on the speed, soil stress and acceleration response of the track and subgrade were systematically investigated. The relationship between the effective composite values of velocity beneath the track and the depth was finally obtained. The results show that the dynamic stress attenuation of the subgrade bottom layer under larger axle loads are relatively faster. It is found that the dynamic stress attenuation of the subgrade bottom layer is relatively fast under the high-frequency uniform excitation of large axial heavy load.

The pile foundation under a high-speed railway (HSR) not only bears the self-weight of the superstructure, but also bears a long-term vertical periodic load during its service. In this study, a large-scale vertical dynamic load test and particle flow numerical simulation method were adopted to investigate the axial cyclic performances of open piles in sand. The results from the dynamic test show that under a dynamic load with cyclic load ratios of 0.1 and 0.2, the surface displacement of the pile decays rapidly as the pile distance increases. Moreover, the higher the vibration amplitude and frequency, the larger the surface displacement. The influence range of the soil around the pile is approximately six times of the pile diameter. It is also found that the external frictional resistance of the upper part of the pile decreases, whereas that of the middle part increases. In addition, the internal friction resistance of the lower part of the pile decreases and gradually stabilizes after approximately 200 cycles. The simulation results show that the influence range of the pile on the surrounding soil is approximately 5–8 times the diameter of the pile under the action of dynamic loading; the vertical displacement of the pile mainly occurs at the beginning of the cycles. The total settlement of the pile foundation increases with an increase in the cyclic load ratio. With an increase in the cycle period, the friction resistance values on the outside of the pile and middle part significantly decrease and increase, respectively. After 10 cycles, the resistance gradually stabilizes, and no evident changes in the internal friction resistance of the pile are observed.