交通运输工程学报

Cover and Contents of Vol.24, No.5, 2024

Cover Contents

Slope effects on highway-side photovoltaics and its wind load calculation method

LIU Zhuang-zhuang, LI Yao-cheng, WANG Feng, SHA Ai-min

Abstract: More> To evaluate the wind load situation on highway photovoltaic slopes (HPVS), a rigid piezometric wind tunnel test was applied to explore the influences of key parameters on the wind load on HPVS, including the wind direction angle, module inclination angle, slope gradient and array position. The slope gradient factor and wind direction angle factor were proposed, and according to the wind tunnel test, a method was provided to estimate the standard value of the wind load of HPVS based on the wind direction angle and slope gradient. Research results show that the slope effect brings a significant influence on HPVS wind load characteristics, and it is more apparent in the downstream elements of HPVS. At positive wind direction angles, the HPVS shows an amplification effect. The effect manifests as amplified wind pressures at small slopes and amplified wind suction at large slopes. It also presents a wind load blocking effect at negative wind direction angles, while the whole wind load is close to zero at large slopes. Under small slope conditions, the wind pressure on HPVS reaches the highest as the wind direction angle is 30°, while the wind suction is the largest when the wind direction angle is 150°. The HPVS is significantly affected by the change of its module inclination angle. Compared to the one without slope, the HPVS module inclination angle with slope has more severe impact on its whole shape coefficient. With the same slope gradient, the shape coefficient of the HPVS module increases with the rise of the module inclination angle. When the slope gradient is 30°, the changing of the HPVS module inclination angle results in the HPVS wind load turning from wind suctions to wind pressures. When the slope gradient is less than 20°, the shape coefficients of the whole module and the lower surface are less affected by the slope gradient at positive wind direction angles. The slope effect is relatively insignificant. When the slope gradient is higher than 20°, the slope gradient shows an increasing remarkable influence on the shape coefficients of the whole module and the lower surface at positive wind direction angles. Meanwhile, the slope effect strengthens gradually. When the slope gradient is close to the module inclination angle, the whole HPVS wind load is slightly affected by the slope structure. In summary, the research results provide a foundation for the wind load calculation in HPVS design.

2024, 24(5): 1-11. doi: 10.19818/j.cnki.1671-1637.2024.05.001

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Desirable energy space identification of clean and self-consistent energy along railways

TENG Jing, LI Long-kai, YANG Qi, SHI Rui-feng

Abstract: More> In order to intelligently identify the desirable energy space of clean and self-consistent energy along railways, a remote sensing image dataset containing 210 railway images with a resolution of 4 800 pixel×2 986 pixel was constructed. To address the problem of incompatible channel information of multi-scale fusion units in remote sensing image processing, a self-attention mechanism module was proposed to enhance the ability to capture multi-scale features. To address the discrepancy in the prediction results of remote sensing images with high resolution at different scales, a multi-scale consistency regularization (MSCR) method was proposed to enhance the robustness of the model during image processing. The MSCR-HRNetV2 method was constructed by combining the self-attention mechanism module and the MSCR method to improve the classical image segmentation HRNetV2 method. The MSCR-HRNetV2 method was verified on the self-built remote sensing image dataset of railways and the publicly available Potsdam remote sensing image dataset, respectively. Analysis results show that on the remote sensing image dataset of railways, the improved MSCR-HRNetV2 method achieves a mean intersection over union (MIoU) of 81.37%, which is an improvement of 3.13% compared with the original HRNetV2 method and an improvement of 3.86% compared with the mainstream image segmentation method DeepLabV3+. On the Potsdam remote sensing image dataset, the MIoU of the MSCR-HRNetV2 method reaches 75.96%, which is improved by 2.01% compared to HRNetV2 and 2.19% compared to DeepLabV3+. It can be seen that the improved MSCR-HRNetV2 method significantly improves the semantic segmentation performance of remote sensing images with high resolution, thus intelligently identifying the desirable energy space for clean and self-consistent energy along railways and providing important technical support for the planning and design of the integration system of transportation and energy.

2024, 24(5): 12-22. doi: 10.19818/j.cnki.1671-1637.2024.05.002

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Configuration optimization for transportation self-consistent energy system architectures under different operation modes

HUANG Hong-xin, HU Li-qun, ZHANG Yi-pu, XU Xian-feng

Abstract: More> In order to promote the utilization of renewable energy in transportation space, four operation modes and corresponding transportation self-consistent energy system architectures were proposed to adapt to the complex and changeable traffic environment and engineering construction and operation conditions. Configuration optimization models of system architectures were established under each operation mode, and the improved non-dominated sorting genetic algorithm was used to solve the configuration optimization models. Combined with case studies, the influencing factors of system architecture configuration schemes under different operation modes were analyzed, and the performance characteristics and adaptability of system architecture configuration schemes to the traffic environment under different operation modes were given. Research results show that operation mode A has the best economic and environmental protection performance, and it is easy to meet construction conditions, but the system reliability is the worst. The simulated operation results under no additional constraints show that the energy loss possibility is 6.7%, and the low-importance load power cut possibility is 23.23%. Operation mode D has the best system reliability, but it requires high grid connection conditions, with a grid connection power of up to 483.53 kW. The characteristics of modes B and C are more balanced and can be applied to most traffic environments. There are conflicts between the optimization directions of different optimization objectives. For every 1% increase in technical or environmental protection performance indicators, the economic investment will increase by millions. The power discard rate mainly affects the configuration capacity of power sources with strong fluctuation in output power and energy storage. In the case of this paper, when hydropower is used, the power discard rate exceeds 40%. There is a linkage effect between different constraint indicators and optimization objectives, and there is a constraint masking phenomenon based on the difference in the strictness of different constraint requirements.

2024, 24(5): 23-39. doi: 10.19818/j.cnki.1671-1637.2024.05.003

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Energy load forecasting of highway facilities in response to integration transportation and energy needs

ZHANG Yu-fei, JIANG Wei, ZHANG Shuo, WANG Teng, XIAO Jing-jing, YUAN Dong-dong

Abstract: More> To accurately predict the energy load, historical energy load data of typical highway structures were investigated, and the influences of multiple factors on energy load, including traffic volume, weather condition, week, month, and holiday/workday, were analyzed. The principal component analysis (PCA) method was applied to reduce the dimensionality of these influencing factors, thereby eliminating the redundancy in original sequences. The effects of holiday/workday attributes and weather condition on energy load characteristics were examined, and a strategy for constructing a candidate dataset (CD) for energy load forecasting models of highways was proposed. On this basis, the dynamic time modeling for multivariate energy load forecasting was performed by using a long short-term memory (LSTM) network model. The proposed forecasting model was validated by using empirical data from the Guilin-Liuzhou Highway in Guangxi. Analysis results show that the cumulative contribution rate of the five principal components of traffic volume, weather condition, week, month, and holiday/workday, is 85.54%, and they are the primary influencing factors of energy load on highways. The peak energy load periods for tunnels, toll stations, and service areas vary, with tunnel energy load peaks showing minimal fluctuations, toll station peaks concentrated between 10:00-21:00, and service area peaks occurring within the shortest period, only concentrated between 11:00-12:00. Across different seasonal test days, the application of CD construction strategy and PCA processing improves the specificity of the training data, resulting in enhanced prediction accuracy, with the mean absolute percentage error not exceeding 12.33% and the root mean square error not exceeding 3.86. The proposed prediction model demonstrates strong applicability for load prediction in various typical scenarios and provides theoretical support for the design of self-consistent energy systems for highways.

2024, 24(5): 40-53. doi: 10.19818/j.cnki.1671-1637.2024.05.004

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Review on molecular dynamics simulation for compatibilities of modifiers with asphalt

LIANG Bo, LIAO Wei, ZHENG Jian-long

Abstract: More> The research into the compatibilities of different types of modifiers with asphalt based on the molecular dynamics (MD) simulation was comprehensively reviewed, and the basic principles and methods of MD were introduced. The building of molecular models of asphalt and modifiers and the selection of environmental parameters were summarized. The influences of different evaluation indexes on the compatibility results and the correlation between MD simulation and experimental results were analyzed. Research results indicate that in studying the compatibilities of different types of modifiers with asphalt, the MD simulation can provide atom-level understanding and show its advantages in performance prediction, exploration of multiple interactions, optimization of ratios, and visualization to thus save costs and reduce experimental time. For polymer modifiers, their compatibilities with asphalt are mainly evaluated by indicators including the solubility, diffusion coefficient, mean square displacement and binding energy. For non-polymer modifiers, the evaluation is mainly based on the indicators such as the diffusion coefficient, radial distribution function, and binding energy. The solubility is widely applicable to the polymer-modified asphalt, but the thermodynamic properties of non-polymer modifiers and asphalt are greatly different, with a large dispersion in evaluation results. The diffusion coefficient and binding energy show wide applicabilities in evaluating the compatibilities of polymer and non-polymer modifiers with asphalt. Due to the influences of many factors such as the chemical composition, physical properties, interactions between molecules, and rheological behaviors of asphalt under different conditions, accuracies of model parameters should be verified by sufficient experimental data. The accuracy and reliability of simulation results are affected by these factors, resulting in certain differences in adaptabilities and results of different models. With the advances in computing power and algorithms, the MD simulation accuracy and efficiency improve greatly. Thus, researchers can more accurately simulate the chemical structures and dynamic behaviors of modified asphalt at different temperatures. If the MD is combined with experiments effectively to achieve multi-scale research, it is likely to reveal the compatibility mechanism of modifier with asphalt comprehensively, improve material properties, and expand the application fields.

2024, 24(5): 54-85. doi: 10.19818/j.cnki.1671-1637.2024.05.005

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Static system reliability analysis of cable-stayed bridge based on improved BP neural network

WANG Chun-sheng, HE Wen-long, ZHANG Wen-ting, YAO Shu-kui

Abstract: More> In order to enhance the efficiency of static system reliability calculation for cable-stayed bridges, a system reliability analysis model was developed based on an improved back propagation (BP) neural network. By introducing the genetic algorithm (GA) into the BP neural network, the limit state functions of key cable-stayed bridge components could be efficiently reconstructed, the design points could be captured rapidly, and the algorithm of GA-BP-GA-Monte Carlo (GBGMC) for component reliability index calculation was established. The rectified β-unzipping method was used to select candidate failure components, and the structure was modified by assuming in turn failure in the potential failure elements. The primary failure modes of the cable-stayed bridge were identified, upon which the fault tree was subsequently constructed. Based on the equivalent linear functions of the failure modes and correlation coefficients, the differential equivalent recursion algorithm was employed to calculate the reliability of the structural system. The effectiveness and accuracy of GBGMC were verified through a reliability study of three numerical examples. The proposed system reliability analysis method was used to evaluate the structural failure history of a cable-stayed bridge with a main span of 448 m. The component reliability indexes in each failure stage were calculated, and the structural system failure tree of the cable-stayed bridge was created. The structural system reliability index was efficiently calculated, and important components controlling the system safety were identified. Research results show that the computational error of GBGMC is within 0.3%, which is better than other traditional methods.The deflection reliability index at the main span center of the cable-stayed bridge is the lowest for the normal utilization limit state, which is 2.7. In terms of the ultimate limit state, the reliability indexes of the cables in the center of the main span, the main girder at the tower, and the lower section of the tower's cable anchorage area all pose a high risk of failure. Their respective reliability indexes are 3.1, 3.6, and 3.9, respectively. Nineteen main failure modes for the cable-stayed bridge at ultimate limit state are obtained, and the system reliability index is 3.8. Research results provide a theoretical basis of system safety control for the design optimization and maintenance decision of cable-stayed bridges.

2024, 24(5): 86-100. doi: 10.19818/j.cnki.1671-1637.2024.05.006

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Chloride erosion test and life prediction of HPC-NC gradient column under dry-wet cycles

SUN Sheng-jiang, DU Rui-zhi, GE Jia-hui, MEI Kui-hua, LIU Jian-zhong

Abstract: More> In order to improve the durability of steel-reinforced concrete structures subjected to chloride erosion in marine tidal and splash zone, a new structure of high performance concrete(HPC) -normal concrete(NC) gradient column was proposed. A dry-wet cycle test method was designed to conduct the chloride erosion test. The transmission law of internal chloride ions under the influence of different test parameters was studied. A simplified calculation model of chloride ion distribution in concrete was established by theoretical derivation and fitting calculation, and the rationality of the model was verified. The life prediction of initial corrosion time of steel bars was performed for the designed gradient structure based on the simplified model. Research results show that the functional gradient structure can effectively adapt to the erosion characteristics of the upper part in the tidal and splash zone subjected to dry-wet cycles and the lower part subjected to long-term immersion. The combination of different admixtures inhibits the erosion of chloride ions, and the free chloride ion content in HPC is 17.7% lower than that in NC. The surface chloride ion content increases with time and tends to stabilize, which conforms to the exponential distribution. The chloride ion diffusion coefficient decreases with action time under long-term immersion or dry-wet cycles. Its reduction rate decreases with time, and finally tends to stabilize. Compared with the values from the test and related literatures, the relative error of chloride ion distribution curve obtained by the simplified calculation model is within 12%. The early warning times of initial corrosion of steel bars with and without admixture under the protective layer thickness of 60-80 mm are 41-85 and 26-47 years, respectively, proving that the addition of rust inhibitor and erosion inhibitor can significantly improve the service life of HPC-NC gradient column.

2024, 24(5): 101-112. doi: 10.19818/j.cnki.1671-1637.2024.05.007

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Mechanical model of dovetail joints of Min-Zhe woven timber arch bridges

YANG Yan, ZHENG Yi, HUANG Cong-yan, WEI Jian-gang, WU Qing-xiong, CHEN Bao-chun

Abstract: More> The pseudo-static tests on full-scale models of dovetail joints of Min-Zhe woven timber arch bridges were conducted, the similarities and differences in the force mechanisms of dovetail joints between Min-Zhe woven timber arch bridges and ancient timber buildings were analyzed, and the applicability of the dovetail joint mechanical model in dovetail joints of Min-Zhe woven timber arch bridges was explored. According to the mechanical equilibrium and deformation coordination, the bending moment-rotation mechanical model and calculation formulas of dovetail joints of Min-Zhe woven timber arch bridges were proposed considering the tenon pull-out distance and mortise gap of joints. Through the test data and finite element analysis, the mechanical model and stiffness of dovetail joints of Min-Zhe woven timber arch bridges were verified. The effect of rotation and loading trips on the tenon pull-out distance and that of the mortise gap and axial force on the stiffness of dovetail joints were revealed. Research results show that the hysteresis energy dissipation of the dovetail joints of Min-Zhe woven timber arch bridges increases with the increase in the axial force in elastic stage. When the rotation is greater than 0.04 rad, the component enters the yield phase, and extrusion deformation cannot recover. When the rotation reaches 0.06 rad, the slope of the hysteresis curve stops growing. The dovetail joints are not damaged after loading. Due to the different force mechanisms of dovetail joints between Min-Zhe woven timber arch bridges and ancient timber buildings, the dovetail joint mechanical model of ancient timber buildings is not suitable for dovetail joints of Min-Zhe woven timber arch bridges. The error of bending moment-rotation of dovetail joints of Min-Zhe woven timber arch bridges between the finite element value and test value is only 3.2%, and the errors of positive and negative elastic maximum bending moments between finite element values and test values are 16.7% and -5.2%, respectively, indicating that the established bending moment-rotation mechanical model can accurately reflect the bending moment-rotation change law of joints during rotation. The tenon pull-out distance is influenced by the rotation in elastic phase and by the loading control displacement and loading stages in elastoplastic phase. The joint stiffness increases from 29.46 kN·m·rad^-1 to 52.24 kN·m·rad^-1 when the mortise gap reduces from 0.06 mm to 0.01 mm, indicating that the stiffness of dovetail joints increases with the decrease in the mortise gap. In summary, the proposed mechanical model can provide a reference for protection, repair, and research on the seismic performance of existing Min-Zhe woven timber arch bridges.

2024, 24(5): 113-130. doi: 10.19818/j.cnki.1671-1637.2024.05.008

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Strength theories and structure-failure characteristics of asphalt pavements

YANG Jian-jun, HUANG Wang, LYU Song-tao, QIAN Guo-ping, ZHENG Jian-long

Abstract: More> To evaluate and verify the failure modes and characteristics of asphalt pavements under complex stress states, the distribution characteristics of equivalent stress within the pavement structure were analyzed by using the classical five strength theories and the unified strength theory. Three typical pavement structure schemes, namely semi-rigid base asphalt pavement, flexible base asphalt pavement, and inverted asphalt pavement, were considered. The failure modes of pavement structures characterized by various strength theories were analyzed through numerical calculations. Research results indicate that structural failure modes and failure layers of a specific pavement characterized by various strength theories are different. For the semi-rigid base asphalt pavement, the first, second, and Mohr's strength theories mainly characterize the bending and tensile failure at the bottom of the base layer, while the third and fourth strength theories mainly characterize the shear yield failure of the asphalt surface layer. The unified strength theory mainly characterizes the tensile and shear combined cracking failure of the surface layer and base layer, and the maximum equivalent stress occurs within the asphalt surface layer, which can reach 0.8 MPa. A specific strength theory may be characterized as differential failure modes in different pavement structures. The fourth strength theory mainly characterizes the shear yield failure of the asphalt surface layer in the semi-rigid base asphalt pavement, and the shear cracking failure of the asphalt surface layer in the flexible base asphalt pavement. The fourth strength theory and the unified strength theory suggest more reasonable characteristics of pavement structure failure and reflect richer information on pavement structure failure. The combination of these two strength theories can characterize common distresses such as cracking in base and surface layers and rutting in surface layer, thus comprehensively controlling the load-type fatigue failure of pavement structures. The unified strength theory reveals the mechanical mechanism of surface layer preferentially cracking and failure, providing a new theoretical explanation mechanism for common pavement distresses such as top-down cracking and longitudinal cracking in practical engineering and proposing an optional strength verification index for independent control of surface layer cracking failure.

2024, 24(5): 131-143. doi: 10.19818/j.cnki.1671-1637.2024.05.009

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Fatigue characteristics of long-life cement-stabilized aggregates under complex service conditions

LIU Chao-chao, CHEN Meng-jie, ZHANG Hong-gang, CHEN Jie, ZHANG Liang-qi

Abstract: More> Under complex service conditions such as different load environments and service lives, the fatigue characteristics of cement-stabilized aggregates with varying curing ages and cement dosages were investigated under different loading modes and frequencies. The fatigue equation of cement-stabilized aggregates under complex service conditions was established based on the loading rate dependent stress ratio. The difference in fatigue characteristics of cement-stabilized aggregates under the influence of internal and external factors was compared and analyzed. A unified representation model of fatigue characteristics of cement-stabilized aggregates under external factors and a conversion relationship of fatigue models under internal factors were proposed. Research results show that under different loading modes, the strengths of cement-stabilized aggregates with varying curing ages and cement dosages are significantly related to the loading rate correlation, and the strength presents a power function relationship with the loading rate. The fatigue curves based on the loading rate dependent stress ratio all cross a fixed strength failure point, and uniformly characterize the single strength failure characteristics and fatigue failure characteristics under cyclic loading. The fatigue test results under different external factors (loading mode, loading frequency, specimen size, shape, etc.) can be characterized uniformly, and the accuracy is above 95%. Fatigue curves under different internal factors (curing age, cement dosage, etc.) present a certain angle to each other, and the size of the angle is related to internal factors within the range of test conditions. Accordingly, the conversion relationship of fatigue models of cement-stabilized aggregates under different internal factors can be established. The fatigue model shows that the fatigue performance of cement-stabilized aggregates tends to stabilize gradually with the increase in curing age and cement dosage.

2024, 24(5): 144-153. doi: 10.19818/j.cnki.1671-1637.2024.05.010

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Review on evaluation of sound quality in high-speed trains

QIAN Kun, SHEN Zheng-hua, TAN Jing, LIU Ke, DUAN Ji-ying, DU Xi-kang, ZHAO Jian

Abstract: More> The current research status and results of the evaluation of sound quality in high-speed trains were introduced from three aspects, including objective evaluation, subjective evaluation, and objective quantitative model. The subjective and objective evaluation methods of sound quality, as well as the objective quantitative models of sound quality in high-speed trains were summarized. The advantages and disadvantages of different models were discussed, and the future development directions of evaluation of sound quality in high-speed trains were forecasted. Analysis results show that at the present stage, most of the acoustic standards and acoustic design objectives for high-speed trains use A-weighted sound pressure level as the interior noise evaluation index, but in most cases, the noise is dominated by the low and medium frequencies. At this time, the A-weighted sound pressure level fails to well characterize the human ear's subjective feeling of the noise, so the use of the sound quality should be considered to carry out the subjective and objective evaluations of the noise. In the future, it is necessary to pay more attention to the applicability study of the objective parameters of the sound quality on the sound quality in high-speed trains, and the extraction of the key objective parameters of the sound quality is one of the important directions of the research on the evaluation of sound quality. The existing traditional objective psychoacoustic parameters cannot be well combined with the machine learning model to realize the accurate evaluation of sound quality. Extracting the features of traditional sound signals and combining it with the machine learning model for sound quality evaluation and analysis are the development trends of the future evaluation of sound quality in high-speed trains. The traditional subjective evaluation method of sound quality in high-speed trains has a long evaluation time and poor repeatability. Therefore, establishing a high-precision objective quantitative model of sound quality to replace traditional subjective evaluation methods, shorten the evaluation time, and improving the evaluation accuracy is the key direction of the future research on the evaluation of sound quality. The traditional multivariate linear regression model fails to evaluate the sound quality in the high-speed train well. In the future, with the rapid development of machine learning, the selection of suitable machine learning models combined with intelligent algorithm optimization to develop more accurate and efficient sound quality evaluation prediction models is an important part of the research on sound quality in high-speed trains. 8 tabs, 22 figs, 67 refs.

2024, 24(5): 154-172. doi: 10.19818/j.cnki.1671-1637.2024.05.011

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Review on accelerated aging and natural aging studies of composites under wet-heat-load conditions

QIN Guo-feng, QIN Wang-zhao, MI Pei-wen, LI Ming, FAN Qiu-han

Abstract: More> For the accelerated aging and natural aging of composites under wet-heat-load conditions, the change laws of micro aging mechanism (chemical properties and surface cracks) and macroscopic mechanical properties (tensile, shear, and bending) of fiber reinforced resin matrix composites in China and abroad under accelerated aging environments (high temperature environment, hygrothermal environment, and wet-heat-load coupling) and natural aging conditions were reviewed. The general process of durability prediction methods and their application progress were summarized, and the future development trends of aging failure studies of composites were pointed out. Research results show that composites are affected by wet-heat-loading, which is mainly manifested as the changes of matrix, matrix/fiber interface, fiber in terms of material composition or tissue morphology damage in microscopic properties, as well as the changes in mechanical properties such as tensile, compression, shear, and bending in macroscopic properties. The aging failure prediction methods of composites mainly involve the selection of aging metric parameters, the establishment of durability prediction models (linear regression, median strength aging equation, Arrhenius model, and artificial intelligence model), and the determination of an equivalent relationship between accelerated aging and natural aging. In the future, in-depth research should be carried out on the intrinsic connection between the microscopic aging mechanism and macroscopic aging performance of composites in aging environments and the correlation and quantitative analysis of aging laws in different aging environments, so as to further reveal the aging failure mechanism of composites in complex environments. On this basis, accelerated aging and natural aging failure test data of various types of composites can be accumulated, and a more accurate equivalent relationship between accelerated aging and natural aging can be established, so as to realize the prediction of durability of composites. 11 tabs, 122 refs.

2024, 24(5): 173-194. doi: 10.19818/j.cnki.1671-1637.2024.05.012

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Research progress on safety of heavy-haul locomotive and bearing stability of couple and buffer system

ZHANG Zhi-chao, CHU Gao-feng, WANG Kai-yun, LYU Kai-kai, ZU Hong-lin, HAN Le

Abstract: More> In response to the service safety of heavy-haul locomotive and its coupler and buffer system, based on the systematic review of relevant line tests and theoretical simulations, the causes, mechanisms, and influencing factors of three main problems were systematically summarized, including the compressed stability of coupler, the safety of lateral crossing turnout for heavy-haul locomotive and the coupler separation, the improvement technologies for locomotive safety and coupler and buffer system stability were proposed, and the future research focus and development direction were forecast. Research results indicate that under the in-train longitudinal forces, the main safety issues of locomotive are the stability of coupler under compression on straight line or large curve, the safety of lateral crossing turnout for heavy-haul locomotive during electric braking, and the coupler separation in the middle of combined train. For the stability of coupler and buffer system, flatten pin coupler can maintain alignment stability by relying on the contact friction effect between coupler tail and follower plate under general longitudinal forces, but will be prone to lateral deflection instability under extreme compressed forces. The stability of coupler and buffer system can be improved by optimizing the secondary lateral stiffness, lateral stop clearance and stiffness of locomotive. The coupler with circular pin can resist the large longitudinal forces by relying on the mechanical stopper from coupler tail and shoulder, and will maintain a stable state by improving the secondary lateral stiffness of locomotive and reasonably matching with the suspension parameters. However, when coupler deflects to shoulder to play a role, excessive secondary lateral stiffness will strengthen the lateral constraint effect of wheel and rail. For the safety problem that locomotive crosses the branch line of 12-type switch or small curve, the coupler with circular pin can follow curve direction, and the safety of locomotive can be effectively improved by controlling electric braking force and optimizing operation. For the coupler separation in the middle of combined train, the mechanism is that the coupler force of middle locomotive experiences a "zero crossing" state, the releasing of vertical component of traction or electric braking force causes coupler head to bounce upwards, and following large pulling force immediately separates trailer coupler at an angle. Although some measures such as optimizing train operation and controlling coupler height difference can be taken to mitigate coupler separation, the fundamental measure is still adding anti-detachment device. The research work provides technical support for the safety improvement of China's heavy-haul railway transportation and the successful operation of 30 000-ton or even higher heavy-haul combined train. The further research should be carried out in the aspects of system simulation model correction, multi-objective optimization of structural parameters, refined train handling optimization, and safety monitoring and evaluation methods of locomotive. 27 figs, 81 refs.

2024, 24(5): 195-216. doi: 10.19818/j.cnki.1671-1637.2024.05.013

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Data-driven equivalent scaled model of coupler-buffer device design for subway vehicles

XU Ping, HUANG Qi, XU Tuo, WANG Ao, YANG Cheng-xing, WANG Shi-ming

Abstract: More> In order to quickly obtain the collision characteristics of the coupler-buffer device in the subway vehicle collision, the design of the coupler-buffer device was studied, and the data-driven equivalent scaled model design method of the coupler-buffer device was proposed. By taking the rubber buffer in the coupler-buffer device as the research object, the equivalent scaled finite element model of the rubber buffer was established and verified by scaled tests. The response surface proxy models of the geometrical parameter and mechanical characteristic in the equivalent scaled rubber buffer were constructed. The expansion tubes in the coupler-buffer device were taken as the research object, and a finite element model of the 1/8 scaled expansion tube was established and verified by quasi-static compression tests. A crashworthiness index prediction model based on the geometrical parameters of the scaled expansion tube was constructed. Based on the collision test of the coupler-buffer device for a type of subway head car, the equivalent scaled model designs of the couple head, buffer, and expansion tube were carried out to verify the validity of the method. A 1/8 equivalent scaled subway head car collision test was carried out to obtain the mechanical property curves, which were then restored and compared with the full-scale subway head car finite element simulation results. Research results show that the determination coefficients of the response surface proxy models of the peak crushing force and total mean force in the equivalent scaled rubber buffer are 0.994 and 0.992, respectively. In the crashworthiness index prediction models of the 1/8 scaled expansion tube, the determination coefficients of the platform mean force and specific energy absorption in the multilayer perceptron mode are both 0.999. In the results of the equivalent scaled coupler-buffer device for the subway vehicle test and the full-scale subway head car finite element simulation, the trends of force-displacement curves of the scaled test and the simulation test are the same, and the errors of total mean force, peak crushing force of the buffer are 1.11% and 5.62%, and the errors of platform mean force and specific energy absorption of the expansion tube are 0.59% and 2.51%, respectively. It can be seen that the data-driven design method based on the coupler-buffer device for subway vehicles can better be applied to the design of the equivalent scaled coupler-buffer device, reducing the cost of research and design in the coupler-buffer device while ensuring the accuracy of the equivalent scaled model.

2024, 24(5): 217-233. doi: 10.19818/j.cnki.1671-1637.2024.05.014

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Accurate prediction of remaining fatigue life and formulation of condition repair procedure of high-speed train body

LU Yao-hui, AI Jin-peng, ZHANG Ya-dong

Abstract: More> In order to reduce the cost of high-speed train operation and maintenance, improve operational safety, and extend the service life of structure, high-speed train service deterioration factors were considered. The method of vehicle system dynamics was adopted to calculate and formulate the load spectrum for the remaining life prediction of train body. A finite element model of train body and a proxy model of crack extension driving force at the focus points were established to achieve the mapping of the load spectrum of deterioration to the dynamic driving force of crack. Based on the advanced CJP model, a crack extension model considering the crack tip closure effect and stress ratio was established, and the relationship between the ranges of CJP stress intensity factor and conventional stress intensity factor was fitted. The Kriging agent model was used to accurately integrate the crack extension life, which further improved the accuracy of life prediction. On the basis of the remaining life prediction of train body, the modal strain energy was used as an indicator to monitor the crack state of high-speed train body. In addition, a condition level function was constructed to establish the corresponding relationship between the remaining life and the crack state. According to the crack monitoring results, the condition level was evaluated, and the consequences of continuous operation were predicted through risk assessment. The most economical repair strategy and repair procedure for high-speed train body were formulated according to the risk level. Research results show that the minimum and maximum values of load amplitudes after deterioration on the left and right sides of air spring are 107 and 122 kN. The maximum value of the load spectrum at the maximum degradation level increases by 6.16%. The structural stresses at the air conditioning mount (focus point 1) on the roof and the door corner position (focus point 2) have the same changing trend, increasing from 12.4 MPa to 15.8 MPa. This indicates that the stresses at the focus points increase with the deterioration of component performance, causing a great probability of failure. Based on the parameters in the CJP model and the International Institute of Welding (IIW) criteria, the calculated shortest remaining life mileages are both located at the connection position between the underframe beam and the longitudinal profile at the first end of train body (focus point 3), which are 6.781×10⁶ and 1.128×10⁷ km, respectively. This suggests that the remaining life calculated by the CJP model is more conservative. Through the systematic research on the service performance deterioration, structural life evolution, and condition course deterioration of high-speed trains, the mapping relationship between the remaining life and the fatigue state is established, and the method formulating the condition repair procedure of train body by combining the remaining life of train body with the operation and maintenance strategy is put forward, which is of great scientific significance for promoting the transformation of high-speed train maintenance mode from plan-based maintenance, fault-based maintenance to condition-based maintenance.

2024, 24(5): 234-247. doi: 10.19818/j.cnki.1671-1637.2024.05.015

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Ventilation and exhaust gas diffusion characteristics of power pack for trains running on open lines in wind environment

ZHU Fen-tian, ZHENG Qi-yao, XU Liang-zhong, CHANG Chao, NIU Ji-qiang

Abstract: More> Aiming at the ventilation and exhaust gas diffusion characteristics of diesel locomotive power pack, the steady-state Reynolds time averaged equation and shear stress transport turbulence model were used to simulate the flow field characteristics of diesel multiple units under crosswind condition. The effects of train speed, crosswind, and skirt plates on the ventilation of the power pack and exhaust gas diffusion characteristics on the roof were analyzed. Research results show that the ventilation performance of the power pack is optimal when the train operates without crosswind on an open line. As train speed increases, the exhaust gas concentration at the intake of most fresh air systems of air conditioning on the roof rises. Strong crosswind increases the airflow of fans on the windward side of the power pack, especially for downstream fans of the same power pack. Compared with no crosswind condition, the ventilation rate of the lead car fans can increase by up to 2.35 times, and that of the rear car fans can increase by up to 3.82 times in crosswind. However, the airflow of leeward fans decreases, particularly for the leeward fans of the power pack in the lead car, and even airflow loss occurs. The maximum fan ventilation rate in opposite direction can increase by 1.21 times. Skirt plates can effectively suppress the interference of crosswind on the fan airflow. Under strong crosswind, the fluctuation amplitude of fan ventilation rate of the power pack with skirt pates is limited to 28% compared to that under no crosswind condition. In an environment without crosswind, the maximum increase in exhaust gas concentration at fresh air inlets of air conditioning downstream of the roof exhaust outlets is nearly 80%. Crosswind can effectively reduce the exhaust gas content of most fresh air systems, causing significant difference between windward and leeward inlets. The deflection of exhaust gas due to crosswind significantly reduces and even eliminates the exhaust gas concentration at most fresh air inlets on the roof.

2024, 24(5): 248-258. doi: 10.19818/j.cnki.1671-1637.2024.05.016

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Monitoring method reconfiguration of expressway transportation volume after significant adjustment of toll collection mode

YAN Sheng-yu, SUN Ke-xin, WEN Fu-hua, XIAO Run-mou

Abstract: More> The new changes in the data structure of expressway network toll collection were clarified, and the index system of transportation volume monitoring (TVM) was improved. In view of the serious reduction in the reliability of gross mass and vehicle type identification data, the method of TVM was reconfigured. The 29×29 interprovincial passenger transport and freight transport exchange matrix was established, and the regional transportation volume rates of the economic zones of Jing-Jin-Ji, Yangtze River Delta, and Pearl River Delta were analyzed. The investigation method of the cardinal number of transportation volume statistics and the elimination method of interference factors in speed statistics under new situation were proposed. By comparing the year-on-year (YoY) growth rates of transport volume from 2009 to 2019 with the average annual growth rates from 2019 to 2021, the feasibility and continuity of the method of TVM were verified, and the characteristics of the whole route within and across the province for passenger trips and freight distance were analyzed. Analysis results show that the average YoY increase rates of freight volume and freight turnover from 2009 to 2019 have a deviation of 2.59% and 2.19% from the average annual growth rates from 2019 to 2021. The proportions of the average annual growth rates of passenger transport volume and passenger turnover of Class 1 cars from 2019 to 2021 in total passenger transport volume and passenger turnover are 0.32% and 0.25% higher than the average YoY growth rates from 2009 to 2019, respectively. It proves that the reconfigured method of TVM is feasible, and the indicator continuity is good. The electronic toll collection (ETC) passenger car and truck flow limited to 206 km within the province can effectively eliminate the interference factors in speed statistics, and the average speeds of passenger cars and trucks increase by 1.76% and 10.38%, respectively. According to the full path data of vehicles in 2021, 88.86% of passenger trips and 81.67% of freight distances are concentrated within 200 km. The passenger trips and freight distances within 200 km are concentrated within 50 km, with concentration rates of 58.09%-67.76%. After the adjustment of the toll collection mode, the freight distance of Class 3 trucks within the province increases by 9.06%, and those of other class trucks within the province decrease by 6.27%-16.81%. The freight distance of Class 6 trucks across the province decreases by 4.60%, and those of other class trucks increase by 3.21%-8.89%.

2024, 24(5): 259-269. doi: 10.19818/j.cnki.1671-1637.2024.05.017

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Evacuation trajectory prediction of passengers in transport aircraft based on social-implicit model

CHEN Kun, LI Fang, FENG Zhen-yu, CHEN Xiang-ming, DUAN Long-kun

Abstract: More> To accurately predict passenger evacuation trajectories in narrow spaces during emergencies of transport aircraft, a social-implicit model based on deep learning was developed. The model included three modules: social zone, social cell, and social loss. Passenger behavior changes and dynamic interactions under different conditions were processed through trajectory clustering and convolutional neural networks. The passenger movement and conflict behavior data were collected from Boeing 737-800 simulation cabin emergency evacuation experiments. These data combined with social force model parameter calibration were used to generate the training dataset. The social-implicit model was trained and validated by using the dataset, and its predictive performance was evaluated in terms of average displacement error (ADE), final displacement error (FDE), average mahalanobis distance (AMD), and average maximum eigenvalue (AME). Analysis results show that the social-implicit model performs well on the constructed emergency evacuation dataset, with an ADE of 0.011 m and an FDE of 0.02 m, representing a 97% reduction compared to the ETH BIWI walking pedestrians dataset and University of Cyprus pedestrian dataset pedestrian datasets. The accuracies of AMD and AMV improve by 72.4% and 94.1%, respectively, indicating that the model excels at capturing passenger trajectory change in narrow environment. In terms of evacuation time, path, speed, and bottleneck position prediction, the model closely aligns with the results of social force model, with evacuation efficiencies of 1.92 and 1.93, respectively. The path prediction can accurately capture the congestion points, with the speed error no exceeding 0.02 m·s^-1, and the bottleneck position error within 0.41 persons per square meter, demonstrating that the model can simulate congestion characteristics during the passenger evacuation. Compared to the social force model, the deep learning model's runtime significantly reduces from 65 s to 0.021 s, and the model size reduces by 78.02%. The social-implicit model provides an efficient and accurate solution for trajectory prediction and performance evaluation in civil aviation emergency evacuation system optimization.

2024, 24(5): 270-284. doi: 10.19818/j.cnki.1671-1637.2024.05.018

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Nonlinear effect of station-area built environment on taxi-metro combined travel

CHEN Qi-xiang, LYU Bin, LI Xian-lin

Abstract: More> The taxi trajectory data was preprocessed and taxi trip data was extracted. Taxi-metro combined travel was identified and categorized into subway extending access (SE-access) trips and subway extending egress (SE-egress) trips, and potential influence areas of subway stations were identified. The extreme gradient boosting (XGBoost) model was employed to analyze the nonlinear effects of station-area built environment on taxi-metro combined travel. The Shapley additive explanations (SHAP) model was introduced to explain the nonlinear characteristics: importance, orientation, and threshold phenomena. The necessity of station-area built environment factors for taxi-metro combined travel was analyzed using necessary condition analysis method. Analysis results indicate that the station-area built environment contributes differently to various types of taxi-metro combined travel, with land use mix, bus station density, road network density, and residential land density significantly necessary for taxi-metro combined travel. During the morning peak hours, key factors influencing SE-access trips are bus station density, residential land density, and road network density, with importance values of 33.38%, 30.10%, and 19.33%, respectively. For SE-egress trips, key factors are bus station density, residential land density, and road network density, with importance values of 41.48%, 15.61%, and 14.41%, respectively. During the evening peak hours, key factors influencing SE-access trips are residential land density, road network density, and bus station density, with importance values of 34.13%, 23.84%, and 23.13%, respectively. For SE-egress trips, key factors are residential land density, bus station density, and land use mix, with importance values of 40.88%, 20.32%, and 14.72%, respectively. The SHAP value of bus station density changes with a three-stage trend, with 15 and 50 stations per square kilometer as threshold points. For road network density, 14 km·km^-2 is a critical demarcation value, meaning that the road network density below this threshold negatively contributes to taxi-metro combined travel, while the road network density above this threshold contributes positively. When residential land density exceeds 0.45 m²·km^-2, it positively contributes to taxi-metro combined travel and tends to remain stable.

2024, 24(5): 285-300. doi: 10.19818/j.cnki.1671-1637.2024.05.019

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Review on map matching technologies in intelligent transportation scenarios

LI Ying, FEI Yi-xuan, AN Yi-sheng, LIU Yang

Abstract: More> To promote the development of map matching technology, an in-depth study of map-matching algorithms was conducted from the perspective of matching methods. The principles, characteristics, and application scenarios were classified and described. The existing map matching datasets were comprehensively introduced. The application scenarios of map matching in the field of intelligent transportation were summarized, and future research directions for map matching technology were proposed. Research results indicate that the accuracy and completeness of global position system (GPS) data can be affected by various factors, which results in sparse trajectory data. Sparse GPS trajectories can result in the inability to accurately reconstruct the actual driving paths of vehicles, increasing the uncertainty in map matching. The demand for lane-level matching has become increasingly urgent due to the development of intelligent transportation systems, the rise of autonomous driving technology, and the growing complexity of urban transportation networks. The future research directions of map matching technology primarily focus on two aspects. For map matching technology with sparse trajectories, attention needs to be paid to data interpolation techniques to improve trajectory continuity, multi-sensor data fusion technology should be employed to enhance the accuracy and reliability of positioning, and deep learning techniques should be applied to improve the intelligence level of matching algorithms. For lane-level map matching technology, the focus lies in integrating high-precision map data with real-time traffic information to provide more accurate information on road characteristics and traffic conditions, optimizing deep learning models to recognize complex traffic patterns and road characteristics, and developing algorithms that adapt to dynamic traffic environments to obtain algorithms with improved stability and adaptability. These research directions will help enhance the accuracy, reliability, and real-time performance of map matching technology and provide stronger support for intelligent transportation system and autonomous driving technology.

2024, 24(5): 301-332. doi: 10.19818/j.cnki.1671-1637.2024.05.020

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Design and application of ship remote-driving control system

LI Chen, YAN Xin-ping, LIU Jia-lun, TANG Min, CHEN Guang-lin, LIN Nan

Abstract: More> To ensure safe and efficient navigation and stable operation control under the "shore-based control supplemented by onboard monitoring and watch-keeping" mode, the definition of ship remote-driving control system and "ship-shore-cloud" cross-domain collaborative integrated fusion architecture were proposed. Aiming at the network time-varying delay problem under stochastic communication environments, incremental redundant retransmission and delay-tolerance compensation methods were integrated to establish the video communication processing mechanism. The Luenberger state observer was constructed to improve the networked control performance, and the control quantity offset caused by environmental interference or model mismatch could be avoided. A typical 64 TEU inland water model ship was taken as the research prototype to develop the system's modularized functions and standard interface protocols, and the effectiveness of the proposed method was verified at a control station 690 km away. Experimental results indicate that turning is more sensitive to network fluctuations compared with straight and path-following conditions. Specifically, the responding time of shipboard underlying hardware increases from 124.53 ms to 135.76 ms at the ultimate turning angle and rotation jitters. After optimization, the influence of 5% packet loss and 40 ms network jitters is eliminated, the end-to-end transmission delay is stabilized at 150-200 ms, and the video stutter rate is controlled within 1.2% by the video communication processing mechanism. The maximum lateral offset error of the path following is 1.54 m, with an average error of 0.61 m, improving the stability and reliability of remote-driving control system effectively, so that it can meet the requirements of typical remote-driving scenarios. As the driver needs some time to familiar with the ship's current steering task and motion state, immediate exit from the control loop will result in increased offsets, temporary jitter, and oscillations during take-over.

2024, 24(5): 333-347. doi: 10.19818/j.cnki.1671-1637.2024.05.021

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Recognition and classification method in multi-ship encounter scenarios based on topological graph

LIU Ke-zhong, KONG Wei, YU Yue-rong, WANG Wei-qiang, YUAN Zhi-tao, WU Xiao-lie

Abstract: More> Aiming at the problems such as the lack of characterization models, and the challenge of distinguishing between ship interactions for multi-ship encounter scenarios in complex navigable waters, a recognition and classification method was proposed based on topological graph for multi-ship encounter scenarios. Considering the dynamic characteristics of ships in time and space, automatic identification system data was divided by time slices to obtain distance data suitable for research. Based on inter-ship Haversine distances, the find-verify-and-fix clustering algorithm was applied to construct time series of topological graphs, and the representative topological graphs were automatically generated in multi-ship encounter scenarios. The similarity between different representative topological graphs for different encounter scenarios was calculated by SimGNN model, and the similarity measurement of multi-ship encounter scenarios was realized. A K-nearest neighbors classifier was employed for multi-ship encounter scenario classification, and the encounter processes of different topological graph number and various ship types were analyzed. Experimental analysis was conducted using real data from a specific day (24 hours) in Ningbo-Zhoushan water area. Research results indicate that the proposed recognition algorithm for multi-ship encounter scenarios accurately identifies 794 valid multi-ship encounter scenarios in the water area, with two-ship encounter scenarios being the most common, followed by three-ship encounter scenarios, and relatively few occurrences of four-or-more-ship encounter scenarios. This result aligns with the perception of vessel traffic service personnel. Most scenarios have a duration of less than 1 000 s, with the numbers of generated topological graphs remaining below 100, indicating a relatively similar trend in data distribution. In the same encounter scenario, there is little fluctuation in ship number, demonstrating the stability of the proposed recognition algorithm. After using the classification algorithm, there is an obvious similarity in ship types and representative topological graphs between scenarios of different durations in the same category. Scenarios of various categories are significantly different in the evolution process, duration, ship type, and representative topological graph.

2024, 24(5): 348-361. doi: 10.19818/j.cnki.1671-1637.2024.05.022

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Distributed cooperative predictive control of virtual coupled trains

LI Zhong-qi, ZHONG Ling-yu, YANG Hui

Abstract: More> To improve the cooperative tracking efficiency and stability of virtual coupled trains, a multi-train interactive cooperative tracking control method was proposed based on the distributed model predictive control (DMPC). A state-space model of virtual coupled leader-follower trains bidirectional topology was established based on the unit train dynamics analysis, so as to improve the limitation of unidirectional topology and make the communication structure more stable. The improved DMPC algorithm was designed by introducing the neighboring system state information into the cost index function and weighting it with the self-state information. Under the constraints of running velocity limit, distance limit, and control quantity limit, the optimal control quantity and state quantity of trains were obtained by solving the improved cost index function, the distributed cooperative control of virtual coupled trains was realized, and the feasibility and closed-loop stability of the algorithm were theoretically proven. The semi-physical simulation system for train tracking and running in the laboratory was used for simulation. The virtual coupled trains consisting of four CRH380A unit trains were controlled to track a specified velocity curve and compared the proposed algorithm with other traditional algorithms. Simulation results indicate that under different initial conditions, the distance and velocity errors of virtual coupled trains can converge after 300 s, the control output can meet the requirements of passenger comfort, and each unit train can still maintain a stable coupled formation after receiving the velocity adjustment instruction. The root mean square errors of velocity and distance of virtual coupled trains obtained by the proposed method are 3.32×10^-8 km·h^-1 and 6.11×10^-7 m, respectively, which are 99.99% lower than traditional methods. Therefore, the control and tracking performance of the proposed method is superior to that of traditional control methods, and the sampling time simulation duration of each unit train can be guaranteed within 3 ms, meeting the requirements of high-speed train control system.

2024, 24(5): 362-378. doi: 10.19818/j.cnki.1671-1637.2024.05.023

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