公路交通科技

05 May 2018, Volume 35 Issue 5
    

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  • Failure Mechanism and Control Measures of Common Trunk Highway Semi-rigid Base Asphalt Pavement
    ZOU Jing-rong, ZHANG Zhi-qiang, LI Tao
    2018, 35(5): 1-7,48. https://doi.org/10.3969/j.issn.1002-0268.2018.05.001
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    In order to study the failure mechanism and improve the durability of asphalt pavement of trunk highway, the mechanism of disease, such as broken pile and cracks of semi-rigid base asphalt pavement, are analyzed based on the field investigation and analyzing pavement drilling core in the area of the common trunk highways in Hunan Province. The stress states of pavement under standard axial load and over 30% of overload are analyzed by means of BISAR finite element software after selecting the typical structure of heavy traffic graded asphalt pavement of trunk highway and establishing the analysis model of pavement structure with consideration of influence of horizontal force on stress distribution. The study result shows that the higher the vertical load, the higher the shear stress level, and overloading does not affect the location of maximum shear stress. By comparing the stresses and strains in 3 kinds of interlaminar binding states, it is found that it is generally in continuous or semi-continuous state and the interface will not be completely smooth. The calculation result demonstrates that (1) in the thin layer pavement structure with asphalt surface less than 10 cm, the high shear stress zone is located on the semi-rigid base, the shear strength of semi-rigid base is lower than the shear stress, which causes the fracture of base course. (2) With the rapid decline of base strength, cracks, rutting and other diseases gradually occur. According to the pavement disease layer, 3 kinds of pavement structure are proposed. The stress states in different structure layers are calculated when changing base and surface thicknesses respectively. The improvement measures of common trunk highway pavement structure are put forward:to increase the asphalt surface layer thickness to at least 12 cm under the heavy load, the thickness of semi-rigid base should reach more than 35 cm, and the interlaminar binding must be ensured in construction process and vehicle traffic must be strictly controlled during semi-rigid base curing period to improve the fatigue life of pavement.
  • Experimental Study and Numerical Simulation of Fatigue Looseness Behavior of Dowel Bars in Concrete Pavement
    YAN Yuan, LI Luo-ke, ZHOU Yi-tang, BAO Liang
    2018, 35(5): 8-15. https://doi.org/10.3969/j.issn.1002-0268.2018.05.002
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    Focusing on the fatigue failure of dowal bar in cement concrete pavement (CCP), the mechanism and propagation rule of the fatigue failure are studied in respect of the mechanical performance degradation of the contact interface between dowel bar and concrete. First, the 3D FE model of CCP is established considering the mechanical behaviors of dowel bar to concrete and surface to base, and the mechanical characteristics of dowel bar system under various vehicle axle loadings act on the edge of plate are studied. Second, the testing system of contact interface between dowel bar and concrete is developed, the pseudostatic accelerate fatigue loading test is designed to simulate the loosening process of dowel bar. Then, the shrink joint substructure FE model which contains the smeared cracks is established based on the test, and the fatigue looseness behavior is simulated by extended FE method. Finally, the calculation method of critical vehicle axel load of shrink joint of CCP is presented. The result shows that (1) the unfavorable position of the shrink joint in load transfer process is the stress concentration region located around the dowel bar under wheel loading; (2) the long term action of heavy-duty vehicles caused the high contact stress loading/unloading state of the concrete around the dowel bar and the cracking and spalling of concrete, which will eventually lead to the increasing fatigue looseness of the dowel bar; (3) application of numerical analysis technique can effectively invert the critical vehicle axle load of the pavement shrinkage structure, prevent the accumulation of damage in the concrete around the dowel bar and avoid the fatigue loosening of the dowel bar. This study helps more accurate evaluation on the working condition of dowel bars in CCP, understand the failure process of the dowel bar under long-term effects of traffic load and environment, helps more scientific prediction on the fatigue life of dowel bar, and helps more rapid comparisons for design schemes.
  • Hazard Evaluation of Glacial Debris Flows in Aoyitake-Bulunkou Section of Karakoram Highway
    DENG En-song, WEI Xue-li, ZHU Zhi-xin, CHEN Bao-cheng, HU Lei
    2018, 35(5): 16-23. https://doi.org/10.3969/j.issn.1002-0268.2018.05.003
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    By using the methods of field investigation, fixed-point observation, interpretation of remote sensing data, regional geological data collection and mathematical statistical analysis, the 26 glacial debris flow gullies along the Aoyitake-Bulunkou section of Karakoram Highway are selected as the study object. Nine indicators are including average slope, weathering intensity of rocks, annual hours of sunshine, average annual temperature, glacier area, distance from the fault zone, drainage area, gradient, largest height difference of drainage selected as the basic evaluation factors. Principal component analysis method is used to determine the weight of each evaluation factor and select the dominant factor, and then the gray system is used to calculate the correlation degree between each evaluation factor and the dominant factor. The calculation formula of the hazard coefficient of debris flow is proposed and a suitable hazard assessment model of debris flow is constructed. The evaluation result shows that (1) glacial debris flows along the research Highway are in moderate-high hazard levels, which are mainly distributed in the lower part of the Aoyitake-Bulunkou section; (2) there are 3 very high hazard debris flow gullies, accounting for 11.54%, 10 high hazard debris flow gullies, accounting for 38.46%, 12 medium hazard debris flow gullies, accounting for 46.15%, and 1 light hazard debris flow gully, accounting for 3.85%. The result of the study coincides with the actual situation of the glacial debris flow in 2011-2015, which shows that the evaluation model is reasonable and feasible, it can provide a scientific basis for debris flow hazard assessment and route selection along and near the Aoyitake-Bulunkou section of Karakoram Highway.
  • Study on Changing Rule and Physico-mechanical Property of Silty Area Based on Statistical Analysis
    ZHANG Yan-ming, LIU Yi-lin, LI Xiao-xuan
    2018, 35(5): 24-33. https://doi.org/10.3969/j.issn.1002-0268.2018.05.004
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    In order to make sure the roller compaction technique for silt in different area, the regional variation rules of the grain composition and liquid plastic limit of the silt in northern region is revealed based on statistical analysis. By analyzing the correlation of grain content, liquid limit value with maximum dry density, optimum moisture content, CBR and linear expansion rate, the internal determining factor of the change of the physical mechanical properties of the silt is revealed. The suitable grinding process of different silts is determined by comparing the rolling effects of the wheel + vibratory roller compaction technology and impact roller compaction technology on different silt roadbeds. The result shows that (1) when the silt distribution area moved from west to east, silt content increased from 8.8% to 8.8%, sand content reduced from 87.9% to 0, and clay content stabilized under 10%; (2) liquid limit increased from 22.4% to 22.4%, plastic limit increased from 15.4% to 21.6%, and plastic index fluctuated around 10; (3) composition of silt particles and liquid plastic limit are greatly influenced by landform; (4) silt content has higher correlations with maximum dry density, optimum moisture content, CBR, linear expansion rate, while it has poorer correlation with plasticity index. By comparing the construction effects of different rolling technologies on the of different silt roads, it is determined that the recommended rolling technology for sand low liquid limit silt and silty sand is wheel + vibratory roller compaction, and that for low liquid limit silt is impact roller compaction + heavy-duty roller pressuring.
  • A Crack Image Segmentation Method Based on Small Scale Fractal Dimension
    TAN Xiao-gang, ZHANG Hong-wei
    2018, 35(5): 34-39. https://doi.org/10.3969/j.issn.1002-0268.2018.05.005
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    A crack image segmentation method based on the theory of small scale fractal dimension is proposed. First, the median filtering is applied to arrange all pixels in a neighborhood of pixel point to be processed according to the size of the gray value. The median value of the arrangement is used as a new value of the pixel point to make the surrounding pixels close to the true value, thereby eliminating the isolated noise points, and the effect of noise can be effectively removed on the basis of preserving crack information. Second, according to the proposed algorithm of small scale fractal dimension, the dimension is refined to the minimum to maximize the image details. Compared with the traditional fractal dimension method, this method can better reflect the irregularity of the cracks, can divide the irregular characteristics of the cracks, and can get better effect. By calculating the fractal dimension of each pixel point in road surface image, the crack information can be effectively extracted. Finally, in order to the effectiveness of the proposed method is verified by a large number of test and precision-recall evaluation system. According to the comparison of crack image segmentation performance of different algorithms, traditional method cannot achieve satisfactory result in accuracy rate. It can be seen from the curves that there is still a certain gap between traditional method and the proposed method, the F-measures of the proposed are basically stable at around 0.9, while most of the F-measures of traditional methods are below 0.7, and binaryzation data can fall below 0.3. The experimental result shows that the proposed method can achieve satisfying result of crack image segmentation.
  • Fabrication Configuration and Unstressed Geometry Achievement of Beam Segment of Incrementally Launched Steel Box Girder
    LI Chuan-xi, ZHOU Qun, DONG Chuang-wen
    2018, 35(5): 40-48. https://doi.org/10.3969/j.issn.1002-0268.2018.05.006
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    In focusing on the deficiencies in fabrication configuration of steel box girder, such as inconsistent weld width between top and bottom of beam segment by "rectangle method", and unequal adjacent edge's lengths (equal beam's heights) or unequal beam's heights (equal adjacent edge's lengths) using "right-angled trapezoid method", the influence of these deficiencies or defects and the application range of these methods mentioned above are investigated by theoretical analysis and numerical calculation, and a new method called " method of trapezoid with equal heights and equal adjacent edge lengths" is proposed. Aiming at the deficiencies of the previous phase transform method that the elevation of control points is chosen as basic variables and the programming is relatively complex based on general formula representation, the method of in-place elevation determinion by using transfer matrix and the basic variable of height difference between two ends of beam segment is proposed. The research result shows that (1) "Right-angled trapezoid method" is more adaptable than "rectangle method". For beam segment with the height of 3.5 m, when the assembled angle exceeds 0.082 degree in "short-straight line replacing curve" method, the weld width between adjacent beam segments in fabrication configuration is more than 5 mm allowable value by "rectangle method", and when the angle exceeds 1.937 degrees, the height difference of the of beam segments or the length difference of adjacent edges are more than 2 mm allowable value using "right-angled trapezoid method", both methods are not adaptable in these conditions. (2) "Method of trapezoid with equal heights and equal adjacent edge lengths" is suitable for determinating each beam segment fabrication configuration with any beam height and any rotation angle, and this method can be applied not only for incrementally launched beams, but also for in-situ assembled bridge such as hoisting large beam segment, cantilever assembling beams and so on. (3) The method of determining in-place elevation of beam segment by using transfer matrix and the basic variable of height difference between two ends of beam segment expanded the expression forms of previous proposed phase transform method, simplified the programming process, and is more intuitive and practical. The result are applied in project, and the incremental launching process is smooth and good practical results are obtained.
  • Study on Single Pile Subjected to Torsion Based on Nonlinear Programming Method7
    ZHAO Ming-hua, LIU Xiang-ning, YANG Chao-wei, XIAO Yao
    2018, 35(5): 49-56. https://doi.org/10.3969/j.issn.1002-0268.2018.05.007
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    In order to obtain the internal force and torsional deformation of single pile under torque, first, using the nonlinear soil springs to simulate the interaction between pile and soil, a simplified calculation model of torsional pile single pile is established based on the assumption of elastic beam. Afterwards, the total energy expression of the pile-soil system is obtained by discrete pile body into several units. Considering the force balance of pile body and torsional displacement continuity conditions, a nonlinear programming model of a single pile subjected to torsion is established based on the principle of minimum energy, which can be solved by the method of optimization to obtain the torsional deformation of single pile. Through the calculation and analysis of torsional pile in double layered foundation model, the applicability of this method in layered soils is verified. The result shows that (1) the torsional rigidity of the pile is proportional to the square root of pile-soil shear modulus; (2) the shear modulus of the top soil has greater influence on the torsional performance of the pile, improving the shear modulus of the foundation soil to enhance the torsion resistance of the pile is an economic and effective method for the actual project. Finally, based on a model test whose calculation program is compiled with MATLAB software, the influencing factors are analyzed. The result shows that (1) under the same torsional load, with the increase of pile shear modulus GP or pile diameter d, torsion angle of pile head is reduced, but the increase of GP cannot effectively improve the ultimate bearing capacity of pile-soil system under torsion load; (2) the larger the pile diameter d, the greater the ultimate bearing torque of the pile-soil system can be, and the change rate of the ultimate torque value is proportional to the square of the change ratio of pile diameter; (3) the value of ultimate bearing capacity of the torsional pile is proportional to the ultimate shear stress B of pile side soil.
  • Analysis and Experiment on Dynamic Characteristics of Skew Continuous T-beam Bridge
    WANG Rong-xia, REN Teng-teng, SONG Wa-li, ZHANG Yu-ming
    2018, 35(5): 57-64,72. https://doi.org/10.3969/j.issn.1002-0268.2018.05.008
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    The spatial grillage model based on a three-span skew continuous T-beam bridge engineering is built using Midas Civil, and the influencing rules of different skew angles on the dynamic characteristics of this kind of structure are analyzed. Considering the effects of skew angle, the formula of fundamental frequency for calculating the impact coefficient of continuous bridges in current specification is modified. Finally, a dynamic load test of factual bridge is conducted to verify the correctness of the modified fundamental frequency formula. The study shows that (1) the first 3 orders vertical bending vibration modes of skew continuous T-beam bridge are changed from the first, third and fifth orders of natural vibration modes to the first, the third and the seventh orders as the skew angle becomes larger, and the change of skew angle has no influence on the first two vertical bending vibration modes; (2) when skew angle is less than 30°, the fundamental frequency approaches to right bridge, it can be considered as that of right bridge; (3) when skew angle is greater than 30°, the effect of skew angle on the calculation of fundamental frequency should be considered; (4) when skew angle is less than 40°, the natural frequencies corresponding to the first 3 orders vertical bending vibration modes still meet the ratio of π2:3.552:4.32 as the same as right bridge; (5) in real skew continuous bridge engineering, the third-order natural frequency can be obtained from the measured first-order natural frequency based on the ratio, which can be used as the natural frequency value in calculating the negative moment effect caused by the impact force; (6) the dynamic load test of the real bridge shows that the calculation result of the modified fundamental frequency formula is reasonable; (7) the dynamic characteristics of skew T-beam bridge can hardly be affected whether the connection between T-beams is rigid or hinged. The conclusions are applicable to the small and medium 3-span continuous skew T-beam bridge with rigid or hinged connections between main girders.
  • Analysis on Temperature Difference Characteristic of Steel Box Girder Cross-section of Cable-stayed Bridge over North Sea Based on Long-term Monitoring
    CHEN Yi-fei, SUN Zong-guang, SHAO Yuan
    2018, 35(5): 65-72. https://doi.org/10.3969/j.issn.1002-0268.2018.05.009
    Abstract ( ) Download PDF ( ) HTML   Knowledge map   Save
    The stress state of steel box girder cable-stayed bridge is very complex due to its structural characteristics. It is difficult to predict the temperature of the steel box girder under the influence of environmental conditions. Difference of in-plane temperature has significant influence on stress distribution of steel box girder. Determining the reference value of temperature difference of steel box girder section is the requirement for safety and durability. At present, there is no uniform scheme to determine the reference value of the temperature difference of the cross-section at home and abroad. Through the long-term monitoring system on the long-span steel box girder cable-stayed bridge located in Chinese northern frozen sea, the temperature monitoring data of girder mid-span cross-section have been obtained. The atmospheric temperature data over 2012 are sorted out, and the annual temperature variation has significant seasonal characteristics. The analysis of difference between 6 main temperature measuring points at cross-section of girder mid-span shows that the transverse temperature difference of roof and vertical temperature difference between roof and floor are significantly, while the transverse temperature difference of the floor is very small, the lateral temperature distributions of the top and bottom plates is obviously asymmetric. The probability distribution models of positive and negative temperature difference among main measuring points are established by weighted Weibull distribution respectively. The fitting effect of distribution function is good. On this basis, the computational method of reference value of section temperature difference is approached based on the relevant standards at home and abroad. Taking the monitoring data from 2012 to 2015 as the samples, the sampling number of the annual samples is 12, the reference values of the temperature difference between the 2 obvious groups of measured points on the steel box girder section are calculated. The result shows that for the specified return period of 50 years, the transverse temperature difference of midspan cross-section of steel box girder roof is 21.42℃, the vertical temperature difference between roof and floor is 28.53℃, exceeding the 20℃ prescribed by General Specifications for Design of Highway Bridges and Culverts. When designing and monitoring steel box girder cable-stayed bridge, it is necessary to pay enough attention to the temperature stress of the main girder.
  • Multi-parametric Analysis on Steel-STC Lightweight Composite Bridge Deck
    ZHAN Jian, SHAO Xu-dong, QU Wan-tong, CAO Jun-hui
    2018, 35(5): 73-81,90. https://doi.org/10.3969/j.issn.1002-0268.2018.05.010
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    To comprehensively study the influences of thickness of STC layer, thickness of diaphragms and spacing of stud shear connectors on the fatigue property of lightweight composite bridge deck, the cooperation among the 3 parameters is analyzed and the comprehensive optimum design parameters of lightweight composite bridge deck under the 3 design parameters are obtained. Based on a bridge, the ANSYS local FE model is built to calculate the fatigue stress amplitude of the typical fatigue-prone cracking details of steel bridge deck under different values of the 3 parameters, and the calculation result is evaluated by the nominal stress method. Based on the result of FE analysis, it is concluded that (1) the lightweight composite bridge deck structure could strongly enhance the local stiffness of the steel bridge deck, but it has limited contribution to the global stiffness of the bridge deck; (2) the lightweight composite bridge deck structure under different design parameters has more influence on the stress amplitude of U-rib-to-deck connection details than that on other details, and the diaphragm cracking details at the U-rib-to-diaphragm weld joints are the cracking control details of the structure; (3) increasing the thickness of the STC layer from 45 mm to 60 mm could further reduce the fatigue stress amplitude of fatigue-prone details in the steel deck; (4) increasing the thickness of the floor beams could better improve the details of cracking at the U-rib-to-diaphragm connection and butt weld at U-rib lower edge, and the stress amplitude reduction is about 20%-29%; (5) reducing the spacing of the stud shear connectors could obviously decrease the stress amplitude of the U-rib-diaphragm weld joints and the arc cutouts in floor beams, and the stress amplitude reductions ranged from 22.01% to 27.96%; (6) According to the simulation, 7 of the 12 lightweight composite bridge deck schemes could satisfy the fatigue strength design requirements and one scheme would never crack theoretically.
  • Influence of Double Cavities behind Masonry Lining on Tunnel Structure Safety
    WANG Wei, GAO Leng-tao, ZHANG Heng-wen, DENG Jun
    2018, 35(5): 82-90. https://doi.org/10.3969/j.issn.1002-0268.2018.05.011
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    To deeply research the influence rule of the existence of different sized cavities behind masonry tunnel lining on the safety and mechanical property of tunnel structure, and to guarantee the safety of tunnel operation, the analysis of the safety influence of the space and scale of double cavities behind masonry tunnel lining is carried out. Based on the field measurement data of a masonry tunnel in Chengdu-Chongqiang line, the cavity distribution features both on depth and width are statistically analyzed, and the suitable normal distribution rule and the probability distribution interval are obtained. By using the plane strain model established by ANSYS FE software, the whole stress of lining, the safety factors of typical sections and the checking calculation for tensile and shear resistances of mortar joint section are researched, and the variations of tunnel lining safety with different scaled cavity diseases are figured out. The result indicates that (1) vault and haunch double cavities and left and right haunches double cavities have the highest frequency, and the cavity distribution features both on depth and width can be expressed by normal distribution; (2) the depth of lining cavities approximately obeys the normal distribution of N(24.88, 6.67), which are mainly between 20 to 30 cm, (3) the width of lining cavities obeys the normal distribution of N(1.39,0.46), which are mainly between 1 to 2 m; (4) the lining safety factor between two cavities is lower than that of other region, the region between two cavities is the key part for safety evaluation and cavity disease treatment; (5) left and right haunches double cavities have more harm than vault and haunch double cavities to lining structure; (6) cavity width of 2.0 m is the critical cavity width for masonry tunnel safety. It is suggested that the cavity width should be controlled within 2.0 m.
  • Simulation of Manual Monitoring System of Expressway Tunnel Unexpected Events
    ZHU Tong, HU Yue-qi, WU Ling, LIU Hao-xue, LIU Wei
    2018, 35(5): 91-98. https://doi.org/10.3969/j.issn.1002-0268.2018.05.012
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    In order to reduce the detecting time of expressway tunnel unexpected events and improve the efficiency of emergency response, the detecting time distribution regularity of the unexpected events under multiple manual monitoring patterns is investigated. First, the basic stochastic model of manual monitoring system of expressway tunnel unexpected events is established. Next, in consideration of the human reliability while performing the monitoring tasks, the model is modified while the correction coefficients characterizing the personnel's working status and working conditions and environment are proposed. Then, the solution method is raised based on Monte Carlo method. Finally, taking the actual monitoring system of an expressway extra-long tunnel in Shaanxi Province for example, the expected detecting time and its distribution regularity of the unexpected events are obtained by computation, and the expected detecting time and distributions under different monitoring and management patterns are compared. The result indicates that (1) the detecting probability of unexpected events increases with time prolonging after the events; (2)the expected detecting time and distribution difference between single monitoring and multiple monitoring is not significant, while the expected time for detecting the unexpected events can be shorten effectively from 1.96 min with one monitor to 1.17 min with multiple monitors inspecting screens separately, and the time that unexpected event can be guaranteed to be detected decreases sharply from 6.6 min to 3.0 min; (3) the worse the working condition and personnel's working status, the longer the expected detecting time will take, and the detecting time extends to 16.8 min with the correction coefficients ranging from 3.0 to 10.0; (4) working environment and personnel's working status are of vital importance for detecting unexpected events. Finally, the meaning of the simulation result for event handling and emergency rescue work is discussed.
  • Study on Generation and Evolution of Road Traffic Accident Chain Based on Bayesian Network Model
    XIONG Xiao-xia, CHEN Long, LIANG Jun, CHEN Yue-xia
    2018, 35(5): 99-107. https://doi.org/10.3969/j.issn.1002-0268.2018.05.013
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    In order to study the generation and evolution rules of road traffic accident chain and fully reflect the mechanism of road traffic accidents, based on the 100-car natural driving research data from the United States, the variables characterizing pre-accident driver status and behavior are constructed considering the impact of driver's status and driving behavior on road traffic safety, which are utilized along with other variables of influencing factors such as traditional driver, roadway, traffic, and environment characteristics for establishing the Bayesian network model for road traffic accident risk type. By introducing the casual chain theory of accidents, a simple path search algorithm for directed acyclic network is used to generate the accident chain set based on the established Bayesian Network, and the information gain feature selection method is used to identify the key accident chain. The result of critical accident chain derived from the 100-car natural driving research data shows that (1) single vehicle accidents tend to occur on curved and sloped roadways when drivers are not distracted or not engaged in complex secondary tasks; (2)while front, side, and rear-end collision accidents are more usually occurred under horizontal and straight roadway conditions with the driver's attention transferring from the roadway ahead to both sides of the window and rearview mirror or the secondary task of the driver becoming more complex. By changing the status probability of each node in the identified accident chain, the evolution path and rule of different types of accidents can be explored, which has overcome the limitation of traditional methods that analyze the causes of road traffic accidents separately, and reflected the interrelationship of the contribution factors and events of accident chain, and provided a new perspective on better control of road traffic risk and realizing the blockage of accident chain.
  • Cooperative Control and Simulation for Intersection Group of Over-saturated Tidal Lane
    XU Xue-qi, JIANG Ke, HUANG Chao
    2018, 35(5): 108-114. https://doi.org/10.3969/j.issn.1002-0268.2018.05.014
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    Variable lane technology is one of the effective solutions to the problem of "tidal traffic congestion", the Tidal Corridor in Hangzhou West Lake District is the main road connecting the western suburbs and urban areas. In order to solve the commuter traffic congestion of over-saturated tidal lane in morning rush, the actual traffic data is deeply analyzed and the bottleneck section of the tidal lane is determined. Based on group dynamics, the cooperative control algorithm is put forward, and a double-intersection cooperative control model is established, the real-time signal cooperative timing scheme under the supersaturated situation at both ends of the bottleneck road is researched. VISSIM+MATLAB adaptive simulation control technology is used to compare the signal timing schemes for intersections at both ends. The simulation results show that (1) The speed in the bottleneck section increased from 22.7 km/h to 28.2 km/h due to the cooperative timing scheme, which has been improved by 24.23%, The congestion level is improved from moderate to mild. Meanwhile, driving time, average delay time and other parameters also reached a certain degree of optimization. (2) although the cooperative traffic control in the 2 intersections achieved a certain effect, the traffic flow in the next section decreased by 12.35% while the average delay time increased by 8.96%. It means that the multi-intersection cooperative timing scheme design based on group dynamics algorithm must emphasize the correlation of upstream and downstream traffic flows. It is necessary to carry out cooperative control over the intersections of all road sections from the overall view. The above works provided a theoretical and practical basis for the quantitative analysis and real-time intelligent control of urban tidal lanes.
  • Design of Transit Network between Urban Area and Suburb Based on K-means Clustering
    LUO Xiao-ling, JIANG Yang-sheng
    2018, 35(5): 115-120,134. https://doi.org/10.3969/j.issn.1002-0268.2018.05.015
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    To change the unreasonable situation of the existing suburban transit network planning,a new suburban transit network optimization model is constructed by applying the Milk-run and Hub-spoke design method in the logistics field to the optimization and design of transit network. At the same time, the corresponding heuristic algorithm is designed to solve the new suburban transit network optimization model. First, the urban bus stations are clustered by k-means clustering method. The same classed stations are the composition stations of a Milk-run line. And the bus line length optimization problem of the same type stations is turned into a classic TSP problem to solve. Combining with a variety of local searches, the shortest path design of each milk-run line is obtained. Then, according to the planned Milk-run line, by traversing all the stations in the milk-run line, the hub location of each Milk-run line in determined. Finally, combining with the passenger demand, the corresponding number of vehicles for each line is allocated, and the corresponding starting frequency of each line based on the running time can be obtained. To verify the practicability and effectiveness of the proposed model and algorithm, the proposed method is applied to the actual suburban transit network optimization in Tin Shui Wai District, Hong Kong. The scheme is solved by Matlab programming. The result of the case study shows that (1) comparing with the actual bus service without changing the existing station layout and the number of vehicles, when the passenger demand maintains the existing level, it can reduce 4.2% total travel time of passenger by using the Milk-run and hub-spoke method to optimize the existing bus service; (2) the setting of Milk-run line and hub stations can produce scale effect, effectively improve the suburban transit system service level, and make residents travel more convenient and quick.
  • A Model for Calculating Bus Route Section Passenger Volume under Incomplete Information
    MA Chao-qun, AI Qian-nan, ZHANG Jun
    2018, 35(5): 121-127. https://doi.org/10.3969/j.issn.1002-0268.2018.05.016
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    To solve the calculation problem of the traffic section passenger volume of urban bus lines under incomplete traffic data information, taking section passenger volume forecast as the research object, the prediction model of alighting passenger volume at bus station is discussed. Using the idea of section coverage, the bus line is divided into different passenger volume distribution links based on the center of passenger flow nodal points along the bus line. The bus sharing rate model on different links is established based on the location condition and passenger volume condition of each station. On this basis, the alighting passenger volume prediction model of each station is built based on the boarding passenger volume data of IC card. Combining the model of the relationship of boarding passengers, alighting passengers and section passengers, the section passenger volume is calculated. Finally, taking the IC cards' data of a bus line of Xi'an in a time period for example, the applicability of the model is analyzed. The land use and population density in the attraction area of 300 m surrounding each station of the line is counted, and the unknown parameters in the model are calibrated by improved genetic algorithm. The result shows that when the parameters to be determined α is 0.419 1 and β is 0.482 3 respectively, the objective function gets optimal solution. The calibration result is used to calculate the alighting passengers of each station of the line, then the bus section passenger volume is obtained. By comparing with the actual car-following survey result, it shows that there is a certain difference between the actual value and the predicted value by the constructed model. The average relative error is less than 23%, and the average absolute error is about 5 persons/section. From the overall result, the change trend of the predicted section passenger volume is basically the same as the actual survey section passenger volume, which shows that the established model is reliable.
  • Coordination Control for Traffic on Arterial Based on Ring-barrier Phase
    LIN Li, FENG Hui
    2018, 35(5): 128-134. https://doi.org/10.3969/j.issn.1002-0268.2018.05.017
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    In order to reduce the delay and improve the operation efficiency of buses in urban arterial road, combining with the technology of arterial traffic coordination control, a phase sequence and phase structure suitable for bus operation is proposed based on the concept of Ring-Barrier double-loop phase control at first. From the view of the parameters of arterial coordination control, based on the analysis of parameters such as common cycle signal, effective green time, bi-directional signal offset, considering the impact of stops and its own driving characteristics on the bus travel process, the optimal model of coordination control for buses in arterial road is established. Second, for calculating the effective green time and selecting the signal offset in this model, the Lingo and MATLAB are used to solve the nonlinear problem and genetic algorithm optimization. Besides, combining with the delay triangle method, a delay evaluation function is established to evaluate the effectiveness of bus coordination control. Finally, combining with the actual case and the methods of branch-and-bound and genetic algorithm, one of the arterial roads in Nanjing City is selected and its north-south direction is set for the coordination control, and 2 kinds of tools are used to optimize and solve the common signal cycle, effective green time, signal offset and other important parameters in the model. The result shows that (1) after the implementation of the algorithm, the delay of buses decreased with the increasing of iterations, the delay function values generally show a declining trend and a faster convergence rate; (2) in the iteration process, compared with the result of the first iteration, the 50th iterative optimization result indicates the bus delays are reduced by 20.13%.
  • Modelling of Cascading Failure and Reliability Simulation of Urban Agglomeration Traffic Network
    LI Cheng-bing, HAO Yu-cheng, GAO Wei, LI Feng-xiao
    2018, 35(5): 135-141. https://doi.org/10.3969/j.issn.1002-0268.2018.05.018
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    In order to improve the urban agglomeration traffic network's ability to resist sudden disasters and decrease the harm brought by cascading failure to improve traffic network's reliability, the cascading failure model for urban agglomeration traffic network is studied. First, we built the traffic network model of the single transport in urban agglomeration, the near nodes are superposed to form the subject traffic network model. Second, based on load-capacity model and characteristic of urban agglomeration, the relative importance of geographical distance and node degree is considered when distributing load of failure nodes to form the subject traffic network model. Taking network efficiency as the reliability index, the effect of cascading failure is measured. Finally, the cascading failure model for road and rail traffic network is established to simulate the cascading failure and to research the change of reliability of Huhhot-Baotou-Ordos urban agglomeration based on different attack strategies, capacity coefficients, geographical distance weights and node degree weights. The result shows that (1) whether random attack or deliberate attack, reliability is lower with lager capacity coefficient; (2) when capacity coefficient increases uniformly, the effect of cascading failure changes quickly; (3) under random attack, disparity of capacity coefficient can cause network efficiency reduces quickly and cascading failure has a great effect on reliability; (4) geographical distance weight and node degree weight impact on the start time of network efficiency saltation, the higher the value of geographical distance, the later the time; (5) under deliberate attack, capacity coefficient exists a threshold, the trend changes similarly in different network efficiency when capacity coefficient is less than the value; (6) cascading failure leads to little effect on reliability because geographical distance weight and node degree weight are set certain values.
  • Evaluation of VFM of PPP Project Based on Intuitionistic Fuzzy Set
    PAN Peng-cheng, WANG Hong-qian
    2018, 35(5): 142-150. https://doi.org/10.3969/j.issn.1002-0268.2018.05.019
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    Value for Money (VFM) is an assessment method for judging whether government and public-private partnerships (PPP) are used in place of the government's traditional procurement mode to implement infrastructure and public services. The service and public welfare attributes of road infrastructure PPP projects determined its strong social benefit. Therefore, combining with PPP VFM Evaluation Guidelines (Trial) and related literatures, based on the refinement of the basic evaluation indexes and supplementary evaluation indexes, a comprehensive index of social benefit is added, and traffic functional benefit, social economic adaptability, environmental impact, and resource utilization are taken as the contents of VFM evaluation index system. Thus, the situation of the past too extensive VFM evaluation index system, and the shortcoming of insufficient consideration of social benefits under PPP model has been improved. In the process of evaluating the VFM, the expert evaluation information is often vague, and there is a hesitation in the decision-making process. The theory of intuitionistic fuzzy set is introduced into VFM evaluation, and the VFM evaluation decision-making model based on intuitionistic fuzzy set and considering social benefit is established. The weights of experts and evaluation indexes, and the comprehensive score of experts' evaluation information are used to determine whether the PPP mode is adopted to implement the project. This method can solve the problem that the experts' information cannot fully expressed and multiple data have to be needed to determine the weights of experts and evaluation indexes in the traditional VFM evaluation method. According to the specific circumstances of different projects, a set of evaluation data can determine the evaluation index weights and expert weights at same time, which makes the evaluation result more concise and more practical.
  • Analysis on Supply Behavior of Rural Passenger Transport Service Based on Evolutionary Game Theory
    GE Xiao-peng, ZHANG Yi, ZHAO Jin-yu
    2018, 35(5): 151-158. https://doi.org/10.3969/j.issn.1002-0268.2018.05.020
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    In order to strengthen the pertinence and effectiveness of rural passenger transport service (RPTS) provision, and improve the quality of RPTS provision, it is necessary to conduct in-depth research on the decision-making behavior of related stakeholders in the process of RPTS provision. The RPTS provision involves 3 stakeholders, including government, enterprises and public. Although the government acts as "domination governance", the ultimate supply mode and supply effect of RPTS are determined by the game behaviors of the 3 stakeholders. Based on the assumption of the limited rationality of participants and the information asymmetry among participants, a benefit model among 3 stakeholders is built with the evolutionary game theory to seek the steady and gradual equilibrium under the condition of maximizing social welfare. The research result shows that (1) the government plays a dominant role in the process of promoting the game equilibrium of the 3 stakeholders, and the subsidy decision would have a great impact on the enterprises' production behavior and the public's decision-making behavior; (2) enterprises aim at pursuing the maximization of profits. and the expected benefits would be increased with more government subsidies; (3) the public selects the specific travel mode for the maximization of their own utility, and their identification and measurement of utility derived from the subjective judgment of their own conditions; (4) even though the government promotes social welfare by subsidizing RPTS, it dose not mean that the government has chosen the optimal supply mode of RPTS. Furthermore, several policy suggestions are put forward, including the introduction of market mechanism to select rural passenger transport enterprises, the introduction of voucher system to provide the public more choice, strengthening government financial subsidies, strengthening supervision in the course and afterwards.