西南交通大学学报

Review on BIM Technology Used in Urban Rail Transit Projects

NONG Xingzhong, SHI Haiou, YUAN Quan, ZENG Wenqu, ZHENG Qing, DING Guofu

2021, 56(3): 451-460. doi: 10.3969/j.issn.0258-2724.20200018

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Abstract:
Urban rail transit project is a huge complicated system engineering with the properties of multi-major, multi-role, multi-constraint, long period, and large investment. Building information modeling (BIM) is a very effective technology to achieve high efficiency, standardization, low cost, and comprehensive collaboration in urban rail transit. Firstly the complexity of urban rail transit construction is analyzed in detail. Then this work summarizes the state-of-the-art BIM technology and its applications. The four kinds of BIM application modes are presented, i.e., construction-oriented, collaborative design and analysis-oriented, commercial software platform-based, and open platform-based BIM engineering. After analyzing the research and application insufficiency, the three major challenges of BIM technology application in urban rail transit are proposed: the integration of large-scale model sharing throughout the life cycle, the BIM-based multi-major, multi-CAD/CAE software collaboration, the high-efficient, low-cost management and usage of massive engineering information throughout the life cycle. Finally, to solve the existing shortcomings, the major trends of BIM technology development in urban rail transit engineering are suggested as the following five aspects: the full life-cycle integrated collaborative management and the related platform, BIM-based multi-major forward collaborative design, specification design of BIM for intelligent construction and operation, IFC (industry foundation class)-based BIM expression and sharing, deep integration of BIM technology and informatization.

Digital Management of Crack Defects Information in Steel Truss Bridges Based on Building Information Modeling

WEI Xing, ZOU Jianhao, XIAO Lin, CHEN Yang, GU Xingyu

2021, 56(3): 461-468, 492. doi: 10.3969/j.issn.0258-2724.20190507

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In order to solve the problem of complex data collection process, poor visualization effect and lack of time-related factors in the traditional bridge defects information management process, the building information modeling (BIM) technology was used to realize the visualization of a steel truss bridge crack defect, and a method for rapid batch update of crack defects information was developed with the visual programming software Dynamo, in which the update code is modularized. By introducing time parameters of defects, a 4D crack defects information model was created, whereby the dynamic correlation between crack defect information and 3D graphics in time series was realized, and the crack propagation law was presented. Results show that the introduction of BIM technology into the bridge defects management system can improve the efficiency of defects information management and realize the visualization of crack defects information. The created 4D crack defects information model can intuitively present the development process of crack defects, facilitate bridge operation and maintenance, and help managers scientifically predict the trend of crack development.

Optimization on Axis of Arch-Shaped Pylon for High-Speed Railway Cable-Stayed Bridge

SHI Zhou, HU Hao, PU Qianhui, LIU Zhenbiao, YIN Tao

2021, 56(3): 469-476. doi: 10.3969/j.issn.0258-2724.20190892

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In order to resolve the pylon layout difficulty for high speed railway cable-stayed bridges when the bridges span existing traffic lines, rivers and so on with small angles, the arch-shaped pylon was adopted and the optimization on axis of arch-shaped pylon was analyzed based on the fixed point iteration method and finite element analysis. Firstly, nonlinear equations for arch pylon optimization are established by analyzing the force balance of arch-shaped pylon based on that the height and span of the arch tower are determined and the initial axis is drawn up. Secondly, the non-linear equations are solved by the fixed point iteration method, and the approximate solution of the reasonable arch-shaped pylon axis is obtained, in which the cable-stayed cable force is calculated by the finite element method. Finally, taking the arch-shaped pylon cable-stayed bridge of Guangzhou–Shanwei High-Speed Railway spanning Shenzhen–Shantou Expressway as the engineering background, the approximate solutions of reasonable arch-shaped pylon axes are obtained under three typical load conditions, i.e., dead load, dead load combined with single-track train vertical static live load, and dead load combined with double-track train vertical static live load. The results show that under the three different load conditions, using the optimized arch-shaped pylon axes can reduce bending moments of arch-shaped pylons by 89.8% to 94.8%, compared with using the initial arch-shaped pylon axis; under the main force or both the main force and additional force, bending moments of optimized arch-shaped pylons are reduced by 64.6% to 92.2%, stresses of arch-shaped pylons are reduced from −172.6–−179.5 MPa to −74.0 – −6.2 MPa, and positive and negative deflections of optimized arch-shaped pylons with fitting axis are reduced by 51.0% and 33.8% respectively.

Hilbert-Huang Transfer Analysis on Vehicle-Induced Vibration Signal of Continuous Bridges Based on ICEEMDAN

XING Shiling, LYU Shuangshuang, ZHU Liming, ZHANG Jia

2021, 56(3): 477-484, 492. doi: 10.3969/j.issn.0258-2724.20190285

[Abstract](699)

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As an improvement of the empirical mode decomposition (EMD), the improved complete ensemble empirical mode decomposition with adaptive noise (ICEEMDAN) has a good application potential in the field of structure damage identification of bridges. In this study, ICEEMDAN and Hilbert transforms were firstly performed on the simulated vehicle-induced vibrations of bridge, and the spectral feature changes caused by the damage were extracted with the established damage identification method. The established method was then applied on the measured vibration data of a real bridge, and the mode components of the vibration signals were identified. The characteristics of Hilbert instantaneous frequency spectrum were finally analyzed and discussed based on the first-order mode components of the measured signal. The results are shown as follows: There are more vibration components in the simulated signal than in the measured signal, and the insignificant mode components in the simulated signal do not appear in the measured signal; The instantaneous frequency of the first-order mode vibration component can be used as the characteristic parameter of bridge damage identification for the determination of the occurrence of damage, the damage location or even the quantification of the damage; The damage recognition capability of the established method is insensitive to the position of the measurement point; The proposed method has a feasibility in engineering practice, which completes the identification of bridge damage and damage location with a simple data acquisition procedure, and without relying on finite element model calculations.

Buffeting Responses of Single-Tower Cable-Stayed Bridge with Rigid Frame System During Construction

TANG Yu, HU Pan, JIA Hongyu, ZHENG Shixiong, ZHANG Gang

2021, 56(3): 485-492. doi: 10.3969/j.issn.0258-2724.20190848

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In order to estimate bridge buffeting responses more accurately, taking a large cantilever steel box composite girder of a single-tower cable-stayed bridge with rigid frame system under construction as the research object, a comparative study is made to investigate the differences in bridge dynamic characteristics caused by different modeling methods for tower-girder nodal rigid zone in finite element models. The two-dimensional incompressible unsteady Reynolds average Navier-Stocks (URANS) simulation method is used to identify aerodynamic admittances and static coefficients of the girder section, which consists of a steel box girder and large lateral cantilever arms. In addition, the quasi-steady buffeting theory of Davenport is carried out in ANSYS to analyze bridge responses in time domain, and the calculated buffeting responses are compared with those of the wind tunnel test of aeroelastic model. Results show that the structural dynamic characteristics and buffeting responses of the single-tower cable-stayed bridge with the maximum double cantilever in construction state are greatly affected by the finite element modeling method for the tower-girder binding zone. The maximum difference between structural fundamental frequencies reaches 21.3%, which deserves attention in similar dynamic analysis. The identified aerodynamic admittance of girder shows its dependence on parameters of incoming wind field, and should be utilized in a rational way. The calculated values of buffeting responses are found to be greater than that of the wind tunnel test of the aeroelastic model, and thus are conservative for structural design.

Simplified Analysis Method for Deflection of Thin-Walled Box Girder

ZHOU Maoding, LIN Pengzhen, ZHANG Yuanhai, JI Wei

2021, 56(3): 493-499. doi: 10.3969/j.issn.0258-2724.20190523

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In order to find a simplified method for calculating the deflection of the thin-walled box girder under the influence of shear deformation, the flexural deformation of the thin-walled box girder is analyzed on the basis of the unit force method. Firstly, by analyzing the distribution mode of the flexural shear stress of the thin-walled box girder, the expressions for the shear influence coefficients of each wallboard constituting the box girder are derived. With the shear influence coefficient, the analytical expression of the simple box girder deflection can be deduced by using Timoshenko beam theory. Secondly, the beam segment analysis model of the box girder is built by using the Castingliano’s second theorem and the program is compiled for solving the complex structure such as the box girder with variable sections. Finally, the example models of the box girders with constant and variable sections are analyzed. The results of numerical examples show that the error between the deflection calculated by the program and the measured and the ANSYS finite element results is within 3%. For the numerical example, the deflection of the box girder is increased by more than 20% due to the shear deformation. Parametric analysis also indicate that the additional deflection caused by the shearing of the flange increases with the width-to-height ratio, whereas for the web, the case is the opposite.

Checking and Analysis of Reinforcement Arrangement Scheme for Slab Track Based on Comprehensive Index Method

GAO Liang, ZHAO Wenqiang, ZHONG Yanglong, TONG Fengzhuang

2021, 56(3): 500-509. doi: 10.3969/j.issn.0258-2724.20190358

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To optimize the mechanical performance of the slab track after reinforcement, an evaluation method for track reinforcement was proposed based on comprehensive index method. The shape change energy density and Gaussian curvature were selected as the evaluation components to construct the quantitative checking index of the reinforcement. Taking CTRS Ⅲ ordinary type slab track as an example, a finite element model for slab reinforcement checking was established, and the influence of different reinforcement schemes on the overall mechanical performance of slab was analyzed. The results indicate that the proposed comprehensive index could highlight the uneven stress area of the track slab. The centralized reinforcement under the rail position can improve the resistance of the track slab to the vertical vehicle load. However, the excessively concentrated reinforcement will lead to a worse adaptability to the temperature load. Compared to the optimum scheme, the comprehensive index of the end of the track plate of the excessively concentrated reinforcement scheme under the heating load is more than doubled. The scheme with larger steel bar diameter and sparse arrangement has poor force balance. The track slab should choose a reinforcement scheme with smaller steel bar diameter, densely arranged, and appropriate centralized under the rail.

Chloride Ion Transport in Concrete of Ballastless Track under Fatigue Loading

REN Juanjuan, DU Wei, DENG Shijie, FENG Xiang

2021, 56(3): 510-516. doi: 10.3969/j.issn.0258-2724.20190690

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The chloride ion penetration resistance of concrete structure of ballastless track under fatigue load is one of the main factors affecting its service performance. In order to analyze the variation of chloride ion transport in concrete under fatigue load, the bending fatigue loading test of concrete specimens immersed in chloride solution was carried out. A two-field coupling model based on the structural mechanics field and the chloride transport field was then established with COMSOL finite element software to simulate the chloride diffusion behavior in concrete. The results show that when the erosion time is 2 d, the chloride ion diffusion depths corresponding to the stress levels of 0.3, 0.5, and 0.7 are 7, 11 and 16 mm, respectively, which indicates that the chloride diffusion depth in concrete increases with an increase in fatigue stress level. The chloride ion concentration calculated by the two-field coupling finite element model is basically consistent with the experimental test results, which proves that the model is reasonable. What’s more, the diffusion depth of chloride in concrete increases with the erosion time, and the relationship between them can be described well by a unary quadratic polynomial.

Shaking Table Test for Structural Model with Inclined Column Transfer System

YANG Chun, WU Hongwei, MO Tingwei, CAI Jian, WU Yi, ZUO Zhiliang, CHEN Qingjun, PAN Guangbin

2021, 56(3): 517-525. doi: 10.3969/j.issn.0258-2724.20190104

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To study the seismic performance of a super high-rise building, a shaking table test with a geometrical scale of 1/35 was carried out. Part of frames in the tower structure of the building are supported by two concrete-filled steel tubular (CFST) mega frame columns with duplex-story height, which are not connected to the first 6 floors. The inclined CFST column transfer structure is arranged on the 7th to 11th floors. Through experiments, failure modes, natural vibration period, story drift, and torsional responses of the structural model were studied first. Then, a numerical analysis of the elastic-plastic seismic response of the original structure was carried out via PERFORM-3D software. Results show that torsion effects were significant because of the asymmetric plane arrangement and the inadequate torsional stiffness of the tower. When the actual peak acceleration on the shake table surface was close to the value of the rare earthquake condition (i.e., 470 cm/s²), the torsional failure occurred in the tower. In this condition, except for very few stories, the story-drift angle of each floor was still smaller the limit value 1/100 of the elastic-plastic story-drift angle. Under all load conditions, the strains of CFST frame columns and inclined ones of the transfer areas stayed elastic. The analysis results are in good agreement with those of experiments.

Test and Evaluation Method for Filling Quality of Foamed Mixture Lightweight Filler Subgrade

LIU Xin, SUN Dongning, XU Xin, DU Lei, HONG Baoning

2021, 56(3): 526-533. doi: 10.3969/j.issn.0258-2724.20190678

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To evaluate the quality of the foamed mixture lightweight filler subgrade, field tests were performed based on ultrasound technology in a practical project. Wave velocity, amplitude and main frequency were selected as evaluation indicators, and a novel method for detection and evaluation of foamed mixture lightweight filler subgrade was established. Evaluation method consisted of two steps: the first step judged whether the on-site subgrade was qualified by evaluation indicators; the second step evaluated quality grade of the qualified subgrade by entropy weight-based subgrade quality uniformity evaluation model. The results show that when testing distance is 0.8 m, the ultrasound test results of the foamed mixture lightweight filler subgrade are stable and representative. 95% of minimum wave velocity, 80% of average amplitude and 86% of average main frequency can be used as the low limits to judge whether the subgrade is qualified. The evaluation results show that the test section subgrade is qualified, and the subgrade quality grade is good.

Bearing Capacity Evaluation of Tunnel-Type Anchorage Based on Artificial Intelligent Algorithm

WANG Zhonghao, GUO Xifeng, YANG Xingyu

2021, 56(3): 534-540. doi: 10.3969/j.issn.0258-2724.20200165

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At present, the tunnel-type anchorage is short of reasonable analytical formula for the evaluation of the bearing capacity, the model test is time-consuming and labor-consuming, and its numerical simulation has poor reliability. To handle the above problems, an artificial intelligence method is presented for predicting the bearing capacity of the tunnel-type anchorage. Starting from its force transmission process, the factors influencing the bearing capacity are analyzed and the evaluation index system of bearing capacity has been determined. Then, given the strong learning prediction ability of least squares support vector machines (LSSVM) and excellent performance of particle swarm optimization (PSO), a PSO-LSSVM model with nonlinear mapping of bearing capacity is established. After training the model with 17 cases of the tunnel-type anchorage as input samples, the optimal combination of kernel parameters and penalty coefficients is determined to be (1,500). Finally, the model is used to predict the bearing capacity of a bridge tunnel-type anchorage and the prediction result is determined as 10.2P. The comparison with the bearing capacity result of 11.0P that is determined by the comprehensive study of the scale model test and numerical simulation method, demonstrate that the predicted result is slightly lower but very close to the result of other method. This also shows that the prediction results of the model are reasonable, reliable and conservative, and the prediction effect is desirable.

Applicability of Novel Pile-Plank Embankment in Seasonally Frozen Regions

ZHANG Shuming, JIANG Guanlu, DU Dengfeng, LIAO Yilai, XUE Yuan, LI Anhong

2021, 56(3): 541-549. doi: 10.3969/j.issn.0258-2724.20190716

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In order to control the frost heaving damage in the seasonally frozen regions of the Moscow−Kazan high-speed railway, a novel pile-plank subgrades with an insulation board was proposed. Comparing the performance of three kinds of thermal insulation materials, expanded polystyrene (EPS) foam board, polyurethane (PU) board and extruded polystyrene (XPS) foam board shows that the XPS insulation board could be used in the new subgrade for its better performance in heat insulation, waterproof, impervious and compressive properties. The thermo-elasto-plastic model was established to study the influences of laying range, insulation board thickness, filling height, and external temperature on the mechanical deformation of the new type subgrade. The results show that when the laying range of the insulation board is extended to the signal wire slot, it can do better to preventing the downward transfer of negative temperatures (reducing the frozen depth), and diminishing the harmful effect of soil frost heaving surrounding the pile-plank structure. With increasing board thickness, the heaving amount decreases exponentially and frozen depth decreases close to a parabolic curve. The upper surface of the insulation board can prevent the downward transfer of negative temperatures and its lower surface plays a role in controlling the soil temperature dissipating under embankment. Increasing the filling height of embankment is helpful to suppress the subgrade heaving amount and reduce the usage thickness of the insulation board. The insulation board thickness should be greater than 0.4 m when the filling height is 0.8 m; and the board thickness should be greater than 0.31 m when the filling height is 2.8 m.

Lateral Performance of Semicircular Corrugated Steel Plate Shear Wall with Edge Stiffeners

ZHOU Linli, TAN Ping, TENG Xiaofei

2021, 56(3): 550-557. doi: 10.3969/j.issn.0258-2724.20190319

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A semicircular corrugated steel plate shear wall with edge stiffeners (CSPSW) was proposed to improve the premature buckling and small out of plane stiffness of flat steel plate shear wall. Theoretical elastic initial stiffness and bearing capacity were derived according to the simplified mechanical model which based on the mechanical characteristics of the CSPSW, and the elastic buckling critical load formula of the proposed steel plate shear wall was also given. Elastic buckling analysis and nonlinear pushover analysis of 22 single-story CSPSW were carried out by using the finite element software ABAQUS, the validity of the theoretical formula was verified. The effects of various design parameters on the buckling performance and failure mode of CSPSW were investigated. The results show that the elastic buckling critical load and bearing capacity of the proposed CSPSW are much higher than the plain steel plate wall. The circular diameter and stiffener thickness ratio should meet the corresponding value requirements to ensure the overall buckling of CSPSW. With the increase of the span height ratio, the decrease of the depth-thickness ratio and the increase of the circular diameter, the elastic buckling critical load of CSPSW increases linearly. The rib width and rib thickness of the side stiffeners have little effect on the elastic buckling critical load of CSPSW. Yielding of the CSPSW prior to buckling under lateral load when the circular diameter is bigger than 30 mm. There are three failure modes of CSPSW, namely bending, bend-shearing, and forming “pleats” in the form of tensile bands.

Hydrodynamic Pressures Study of Barrier Lake under Coaction of Earthquake and Clastic Flow Landslide

ZHAO Haixin, YAO Lingkan, HUANG Yidan, SU Yue

2021, 56(3): 558-563. doi: 10.3969/j.issn.0258-2724.20190323

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A shaking table model experiment was designed to study the hydrodynamic pressures of the barrier lake under the action of an earthquake and a clastic flow landslide. Firstly, an experiment was carried to study the hydrodynamic pressure of the barrier lake under the action of an earthquake to obtain the hydrodynamic pressure data, which was compared with the existing calculation formula of seismic hydrodynamic pressure. Then, an experiment was carried to study the hydrodynamic pressure caused by the surge of the barrier lake under the action of a clastic flow landslide to obtain the hydrodynamic pressure data and a statistical formula was established. Finally, an experiment was carried to study the combined hydrodynamic pressure under the effect of an earthquake and a co-seismic clastic flow landslide and a formula for calculating the combined hydrodynamic pressure caused by an earthquake and a clastic flow landslide was established. The results show that the relationship between the hydrodynamic pressure caused by an earthquake and water depth and seismic peak acceleration can be described by Westergaard’ formula. The hydrodynamic pressure caused by a clastic flow landslide is negatively related to the initial water depth, positively related to the inflow velocity and volume of landslide. The combined hydrodynamic pressure is less than the sum of the single hydrodynamic pressure under the action of an earthquake and the single hydrodynamic pressure under the action of a clastic flow landslide, which is about 51% − 95% of the sum of two.

Overtopping Failure of Moraine Dams under Action of Earthquake-Induced Resonant Water Surges

ZHANG Cong, YAO Lingkan, HUANG Yidan, SU Yue

2021, 56(3): 564-571. doi: 10.3969/j.issn.0258-2724.20190454

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Shaking table model experiments were designed to study the overtopping failure mechanism of moraine dams under action of earthquake-induced resonant water surges (ERWSs). Firstly, movements of earthquake-triggered surges under resonant and non-resonant conditions were compared to examine the main influencing factors of maximum height of ERWSs, and a prediction equation for the maximum height was proposed through dimensional analysis. Then, based on the critical water head condition for coarse particle initiation and the critical water volume condition for sediment transportation in dam break, critical conditions of overtopping failure for barrier dams under water surge actions were established and a risk assessment procedure was developed. Finally, taking the 34 small-scale moraine-dammed lakes located in the Parlung Zangbo River basin as examples, the operation of the proposed procedure was demonstrated. Results show that compared with non-resonant surges, ERWSs have greater amplitudes and a much slower process of attenuation with time, and a steady state with continuous large-amplitude wave motion exists in the time history of the resonant surge. When the seismic resonance effect is considered, the number of dangerous moraine-dammed lakes in the Parlung Zangbo River basin increases from 3 to 11, and the distribution extends to the areas with smaller peak ground acceleration (PGA). The results provide a scientific basis for seismic risk assessment of barrier lakes along the Sichuan-Tibet Railway.

Pavement Crack Segmentation Algorithm Based on Pulse Coupled Neural Network with Brainstorming Optimization

FAN Xinnan, WANG Jie, SHI Pengfei, LI Min

2021, 56(3): 572-578. doi: 10.3969/j.issn.0258-2724.20190354

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In order to improve the segmentation accuracy and robustness of crack detection, a new segmentation algorithm for pavement crack image is proposed on the basis of brain storming optimization (BSO) and pulse coupled neural network (PCNN). This method uses the maximum entropy criterion as the fitness function of the BSO algorithm, and then determines the individuals participating in the next iteration according to the fitness value. Since the BSO algorithm has strong convergence, which is able to quickly determine the optimal individual solution. Combining the image features, the optimal parameters of the model are obtained, which can be substituted into the PCNN model to achieve the segmentation of the crack image. The experimental results show that the maximum fitness value of different road crack images can be obtained within 20 iterations, so as to determine the best segmentation parameters. Compared with traditional crack segmentation algorithms like Sobel, PCNN, genetic algorithm based on the maximun entropy of the histogram (GA-KSW), and genetic algorithm based on the pulse coupled neural network (GA-PCNN), the proposed method achieves a regional consistency accuracy of 0.9924 and a regional contrast of 0.9924 and a regional contrast of 0.0900.

Weather Classification in Traffic Scene Based on Joint Voting Network

CUI Hongtao, CAO Ke, ZHANG Hu, CUI Xiao

2021, 56(3): 579-586. doi: 10.3969/j.issn.0258-2724.20200084

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Weather classification based on road monitoring images has become an important research topic in intelligent traffic system. With the application of convolutional neural network (CNN), image recognition has been greatly developed. However, the existing deep learning methods still face great challenges in weather recognition of complex traffic scenarios. A novel deep neural network (DNN) model based on joint voting framework is proposed to extract rich semantic features. The proposed model consists of two core modules: the second-order feature module based on channel and spatial attention mechanism and the joint voting classification module based on composite features, which can extract discriminant information from different weather images and improve the weather recognition performance in complex scenarios. Extensive experiments conducted on two benchmark weather classification datasets demonstrate that the proposed joint voting DNN outperforms the existing weather recognition method by 1.97%.

Formal Method for Behavior Verification and Data Validation of Station Interlocking System

WANG Keming, WANG Xia, CHENG Peng, LIU Ning, ZHANG Chuandong

2021, 56(3): 587-593, 610. doi: 10.3969/j.issn.0258-2724.20191182

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Station interlocking system is a typical safety-critical system driven by data, which needs to verify the system behavior and confirm the correctness of data in the development. After analyzing the design specifications of the interlocking system, the initial system model was built automatically by the UML (unified modeling language) diagram, with the system properties and event flows described by Event-B language on RODIN platform. Subsequently, the refinement policy was used for hierarchical modeling, and the proof obligations of each layer were proved by theorem and the properties of the system attributions were verified. Thus, a reliable universal function model was obtained. Using a real station yard, the axioms of the model were proved and the interlocking data were validated as well. According to the formal verification and data validation in a given scenario, the subtle defects generated in the analysis of the system requirements could be found and corrected. Finally, the functional simulation and acceptance testing confirmed the correctness of the general model and the interlock data. This method not only improves the accuracy and hierarchy of the model-based development, but also verifies the universal behavior state of the system. Combined with axiomatic verification, the validation of interlocking data is realized. The function scenario can be simulated and tested based on the model, which can further improve the reliability of the universal function prototype of the system.

Efficiency of Traffic Structure Based on SBM-Tobit-GWR Model

CAO Xudong, WANG Jianjun, CHEN Chenchen

2021, 56(3): 594-601. doi: 10.3969/j.issn.0258-2724.20190881

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Under the guidance of resource conservation and ecological environmental protection strategies, in order to improve transportation efficiency, optimize transportation structure, and achieve environmental friendly and sustainable developments of transportation industry, the factors affecting the transportation structure efficiency are analyzed from the two aspects of traffic input and system output. By introducing the super-SBM (slack based measure) undesirable model, which considers the environmental benefits of the transportation structure system, the transportation structure efficiency of 30 provinces in China is systematically analyzed. Then, the Tobit regression and geographically weighted regression method are used to analyze the causes of transportation structure efficiency differences, the spatial differentiation of factors, and accordingly propose the adjustment strategies for the transportation structure. The results show that the comprehensive efficiency of transportation has obvious regional differences. The top five provinces are Shanghai (1.567), Guangdong (1.366), Yunnan (1.292), Jiangxi (1.181) and Anhui (1.160). The regression coefficients in terms of the proportion of secondary industry output in GDP, population density, and regional per capita GDP are 0.9513, 0.7659 and 0.5691 respectively, which have the most significant impact on the transportation structure efficiency. The spatial distribution of sub-variable coefficients shows that there is spatial heterogeneity for different regions in the influence level of socioeconomic factors on the transportation structure efficiency. To improve the overall transportation efficiency in China, it is necessary to transform the large-scale and rough development of transportation infrastructure into the refined design and planning of transportation layout, optimize resource allocation, and promote the development of public transportation.

Optimization of Wing Rail Lifting Value for Rigid Frog of Speed-Up Turnout

ZHANG Pengfei, ZHU Xudong, LEI Xiaoyan

2021, 56(3): 602-610. doi: 10.3969/j.issn.0258-2724.20190488

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In order to study the influence of the rigid frog structure irregularity on dynamic characteristics of trains passing through the turnout, based on the theory of wheel-rail contact and wheel-rail system dynamics, a frog model of switch and a CRH2 vehicle model under different wing rail lifting design schemes were established in the case of the rigid frog of Chinese No.12 single turnout. On this basis, the influence of wing rail elevation design on the dynamic characteristics, passing speed, and ride stability of trains crossing the turnout were analyzed. Results show that with the wing rail bending outwards the wheel-rail contact area begins to move outwards when the train crosses a switch, resulting in a reduction in the vertical position of the wheelset center of mass. The problem of lowering the vertical position of the wheel’s center of mass can be effectively solved by setting a reasonable wing rail lifting value, to improve the stability of the train crossing the switch and the comfort of passengers. The design of wing rail lifting can effectively improve the dynamic characteristics of the train passing through the turnout in the straight direction, but the effect on lateral crossing is limited. When the heightening value of the wing rail is set as 3 mm, the optimal effect of wing rail lifting is the best. Compared with the design without wing rail heightening, the maximum values of lateral and vertical wheel-rail forces of the first wheelset of the train passing through the turnout with heighted wing rail in the straight direction are reduced by 45.8% and 30.3%, respectively. In addition, the lateral and vertical accelerations of the vehicle body are also reduced by 42.2% and 26.1%, respectively. With the increase of the train running speed, the dynamic response of the wheels and rails at the time of crossing the turnout is gradually intensified, and a reasonable design of the wing rails will help to increase the speed of the train crossing the turnout. The research results can provide some theoretical reference for the structural optimization design of rigid frog for railway lines in China.

Effect of Rail Hardness on Fatigue Cracks Initiation and Rail Wear

WANG Junping, ZHOU Yu, SHEN Gang

2021, 56(3): 611-618. doi: 10.3969/j.issn.0258-2724.20190184

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Abstract:
In order to study the relationship between rail hardness and rail wear and fatigue cracks initiation life, based on the Archard wear model and the critical plane fatigue cracks initiation prediction model, the prediction method for the coexistence of rail fatigue cracks initiation and wear was presented by combining wear and sectional iteration of profile changes and fatigue damage accumulation. The wear growth, fatigue damage accumulation and fatigue cracks initiation life of 4 kinds of rails with different hardness were researched. The results show that the fatigue cracks initiation life predicted by above-mentioned method has a good agreement with that of the field observation. The rail with high hardness can reduce wear and prolong the fatigue cracks initiation life, which is suitable for sharp curves. Among the rails with four hardness, the average wear growth rate can be reduced by about 3% − 6% and the fatigue cracks initiation life can be prolonged by about 9% − 12% when the hardness of the rail increases by every 10 HBW. Comparing to the U78CrV/U76CrRE hot rolled rail, the average hardness of the U78CrV heat-treated rail increases by about 17.9% while the wear growth rate reduces by about 19.8% and its fatigue cracks initiation life prolongs by about 57.7%. With the wheel/rail friction coefficient of 0.3, the fatigue cracks are initiated at rail sub-surface which is below rail surface of about 1.0 − 2.5 mm and close to rail top center of about 15 − 18 mm in all 4 kinds of rails.

Initiation Cause of Subway Rail Corrugation on Track with Rubber-Booted Short Sleepers

LI Wei, ZHOU Zhijun, WEN Zefeng

2021, 56(3): 619-626. doi: 10.3969/j.issn.0258-2724.20190734

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Abstract:
To investigate initiation cause of short-pitch rail corrugations occurred on curved tracks with rubber-booted short sleepers, field measurement and numerical simulation methods were employed. Firstly, establishment of the relationship for wavelength of the rail corrugation and dynamic behaviour of the track was facilitated by the field measurement. Then, wheel-rail contact parameters were calculated by a vehicle-track coupled dynamics model. Receptance of the tracks was measured by an impact excitation technique. At last, a linear model for the rail corrugation was established to analyze characteristic of rail wear based on the wheel-rail contact parameters and the receptance of the tracks. Rail wear rate of the tracks in the frequency domain was calculated during a vehicle running at curves. The initiation cause for rail corrugations with specific wavelengths occurred on the tracks with rubber-booted short sleepers was clarified. The results show that corrugations for the tracks with rubber-booted short sleepers have occurred at curves with radius of less than or equal to 800 m. Main wavelength of the corrugations is about 50−160 mm and level of the corrugations on low rails is higher than that on high rails. Passing frequency of the corrugations is in the range of 140−280 Hz, which is close to resonant frequencies (160−300 Hz) of the track with rail vibrating related to sleepers. Modal shape of the tracks exhibits rails and sleepers vertical vibrating on the slab in same and opposite directions at frequencies of 160−210, 250−300 Hz. Initiation of corrugation on the curved tracks is determined by the dynamic behavior of the tracks. Characteristic of corrugations exhibits the fixed-frequency mechanism, which means wavelength of the corrugations is related to the speed of vehicle.

Effect of Defect on Fatigue Property of EA4T Axle Steel

LI Hang, ZHANG Jiwang, XU Junsheng, SU Kaixin, ZHANG Jinxin, LU Liantao, WU Mingze

2021, 56(3): 627-633. doi: 10.3969/j.issn.0258-2724.20190373

[Abstract](675)

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Abstract:
In order to accurately evaluate the effects of different size defects on the fatigue property of EA4T axle steel, the drilling method was used to artificially introduce defects on the surface of the smooth specimen, and the fatigue test was carried out to obtain the fatigue limits on the smooth specimens and the specimens with different size defects by the rotary bending fatigue machine. The fracture morphology was observed by a scanning electron microscopy (SEM). Finally, the fatigue limits of specimens with defects were assessed using Neuber's formula (based on notch sensitivity) and a modified El-Haddad model (based on fracture mechanics). The result show that when the defect size of the specimen is less than 59.64 μm, the fatigue limit is the same as the smooth specimen, both of which are 360 MPa, however, when the defect size is larger than 59.64 μm, the defect will reduce the fatigue limit of the smooth specimen, and the larger the introduced defect size, the lower the fatigue limit. Fatigue strength prediction based on the Neuber formula is conservative, however, the modified El-Haddad model can better predict and evaluate the effect of different size of 3D hole defects on the fatigue strength of EA4T axle steel.

Extreme Value Inference of Axle Stress Spectrum for Intercity EMU

DING Ran, LI Qiang, WANG Wenjing

2021, 56(3): 634-639, 665. doi: 10.3969/j.issn.0258-2724.20190662

[Abstract](593)

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Abstract:
In order to evaluate the reliability and extend stress spectra of axles, the maximum stress during its full life need to be predicted. First, to obtain the empirical cumulative distribution function of axle stress, the bin width of 0.5 MPa is chosen, which is based on the Sturges formula as a tradeoff between the inferred accuracy and statistical efficiency, and the rain flow counting is performed against the measured axial stress-time history. Secondly, the empirical mean excess function is calculated according to different threshold values and the reasonable threshold is determined by identifying the turning point of the mean excess function. Then, based on Pickands-Balkema-de Haan theorem, the excess distribution function of the axle stress is fitted with the generalized Pareto distribution, and the maximum stress during the full life is inferred with the fitted distribution. Finally, this method is verified with the measured data. The results show that in order to assess the maximum axle stress during its full life, the tests of 3000 km are required at least. The inferred maximum stress with the measured data of 13.5 t wheel load is about 13% higher than that with the one of 14.1 t wheel load. Therefore it should be particularly cautious to operate at axle design weight.

Optimal Configuration of Wind-Solar-Hydrogen Multi-Energy Complementary Microgrid with Demand Side

CHEN Weirong, FU Wangxuan, HAN Ying, LI Qi, HUANG Lanjia, XU Chengpeng

2021, 56(3): 640-649. doi: 10.3969/j.issn.0258-2724.20200163

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Abstract:
To optimize the economic cost of multi-energy complementary microgrid, an optimal configuration method is proposed for the wind-solar-hydrogen multi-energy complementary microgrid with demand-side response. First, the operation control strategy is formulated under the relevant power constraints and control principles. Then, in order to maximize the direct consumption of wind and solar power, an incentive demand-side response is introduced, and the mixed integer programming is used to optimize the load curve. Further the optimal configuration model with the demand-side response is established: with the minimum annual cost as the optimization goal and the requisite constraints of the system, the particle swarm optimization is used to iteratively find the optimal configuration. In order to verify the model, the historical data of a certain area is utilized to solve the optimal configuration scheme, and the technical and economic analysis is carried out under different operating modes of microgrid, the self-balance rate constraint and influencing factors of construction cost. The analysis results show that by introducing the hydrogen energy power generation system and considering the demand-side response, when the self-balancing rate is 81.64%, the minimum cost to reach the equivalent annual value is 3.143 million yuan; the self-balancing rate is controlled at a reasonable level, and the cost reduction promoted by the technology advancement will help to improve the economic benefits of the microgrid.

Current-Carrying Mechanism of New Continuous Cable Traction Power Supply System

ZHANG Liyan, LIANG Shiwen, LI Xin, JIA Ying, HAN Dushuo, LI Qunzhan

2021, 56(3): 650-658. doi: 10.3969/j.issn.0258-2724.20200057

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Abstract:
Continuous cable traction power supply system is free of electrical phase separation and extend power supply distance, dealing with power quality problems effectively. However, cable traction network (CTN) contains different voltage levels, and the fundamental frequency current flows every CTN link before being used by trains. Moreover, the harmonic current transmitted from trains needs to penetrate in two voltage levels before feeding back to utility grid. In order to study current-carrying mechanism in novel continuous cable TPSS, starting from the special topology of CTN, the equivalent circuit of train-CTN coupling system is established according to dual-port network analysis method. Then current transmission rules in CTN are analyzed. Combined with simulation model, the harmonic current distribution in CTN and harmonic current content of main substation (MSS) are studied. When the new system contains eight short sections for one train, the fundamental frequency current is mainly transmitted by the single-sided CTN where the train locates, and the current ratio between load and MSS is less than four (traction transformer ratio). The harmonic current content of MSS decreases by 43.5% compared with harmonic current content at train.

Influence of Catenary Stitch Wire Parameters on Dynamic Performance Between Pantograph and Catenary

GUAN Jinfa, TIAN Zhijun, ZHANG Xuewu

2021, 56(3): 659-665. doi: 10.3969/j.issn.0258-2724.20190326

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Abstract:
In order to determine the optimal design values of the catenary stitch wire at different speed levels, the dynamic simulation models of pantograph, catenary and pantograph-catenary contact have been established by finite element method, which correspond to the speed levels of 250 and 350 km/h for Chinese high-speed railways. The dynamic performance indexes of pantograph and catenary, such as the section area, statistics of contact force and the maximum uplift at supporting points have been obtained and compared, with different cross-sectional areas, tensions and length of the stitch wire under double pantographs. The results show that for the parameters of the stitch wire on O2-1 catenary, JTMH 35 mm² cross-section, (2.80 ± 0.10) kN tension and 14 m or 18 m length at 250 km/h should be chosen; for the parameters of stitch wire on Beijing−Shanghai high-speed catenary, JTMH 35 mm² cross-section, (3.50 ± 0.10) kN tension and 18m length at 350 km/h. The change of stitch wire parameters has little influence on the contact force of the anterior pantograph, but has a significant effect on that of the posterior pantograph. The maximum uplift at supporting points with the stitch wire length of 22 m is 111% at 250 km/h and 117% at 350 km/h of the stitch wire length of 18 m, which means that the change of stitch wire length has a significant impact on the maximum uplift.

An NLOS Environment Location Algorithm Based on Geometric Constraint and Iteration

DENG Ping, XIE Xue

2021, 56(3): 666-672. doi: 10.3969/j.issn.0258-2724.20200094

[Abstract](444)

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Abstract:
In non-line-of-sight (NLOS) environments, the traditional optimal localization algorithm is weak against NLOS errors and needs an accurate initial position value to guarantee the algorithm converge. To deal with this, a positioning algorithm based on geometric constraint and iteration in a scenario of two base station (BS) is proposed. By introducing the maximum scattering radius as the geometric constraint condition, the linear iterative method is used to perform a one-dimensional global search, and the initial estimation positions of mobile station (MS) are obtained by the least squares (LS) algorithm. Then the initial MS estimation positions are filtered by a distance threshold value, and finally its final position is obtained by weighted average. Simulation results show that when the scattering radius is 200 m, the probability of location error under 200 m can reach 100%, and in the same environment, the calculation time of this algorithm is only 0.4% of the grid search algorithm.

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2021 Vol. 56, No. 3