20 July 2017, Volume 30 Issue 7
    

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  • Research on Mesostructured Characteristics of Asphalt Mixture Based on Particle Packing Theory（in English）
    TAN Yi-qiu, XING Chao, REN Jun-da, ZHANG Lei
    China Journal of Highway and Transport. 2017, 30(7): 1-8.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to investigate the influence of particle grading on the mesostructure of asphalt mixtures, particle packing theory was utilized to propose interference parameter for particle grading evaluation. Based on the X-ray CT, the asphalt mixture with different grading, compaction times and compaction modes (i.e. Marshell and Gyratory methods) was scanned and three-dimensionally reconstructed. Combined with digital image processing technique, void distribution of the asphalt mixture and contact relations of particles were extracted. Fractal theory was applied to calculate the fractal dimension of void volume and position. Finally, relations between interference parameter and 3D void fractal dimension, interference parameter and particle contact were analyzed. The results show that with the increase of compaction times, the number of large voids and middle voids increases first and then decreases in two specific compaction modes. The average volume of large void decreases with the increase of average volume of middle void. For small voids and micro voids, the number of voids increases continuously with the increase of compaction times but the average void volume does not change obviously. The continuity of void volume distribution decreases with the increase of interference parameters, while the homogeneity of spatial location distribution increases with the increase of interference parameters. The continuity of asphalt mixture with gyratory compaction is poorer than that of mixture with Marshall compaction, however, the homogeneity of asphalt mixture with gyratory compaction is better. The number of contact points of dominant aggregate increases with the increase of compaction times, with the descending order being OGFC, SMA and AC. The number of contact points declines with the increase of interference parameters.
  • Preparation and Effect of Environment-friendly Cooling Micro-surfacing
    WANG Chao-hui, YIN Wei-yong, SUN Xiao-long, WANG Xin-qi, FENG Wei
    China Journal of Highway and Transport. 2017, 30(7): 9-17.
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    To achieve the environmental effect of cooling and exhaust purification for pavement preventive maintenance materials, the environment-friendly cooling micro-surfacing was prepared by adding functional materials, based on sophisticated micro-surfacing technology. The cooling and purifying testing devices were made independently for indoor and outdoor tests. The cooling and purifying effect of different types of environment-friendly cooling micro-surfacing was evaluated comprehensively. The road performances of the environment-friendly micro-surfacing were investigated systemically. The micro structure and the mechanism of cooling and purifying were revealed. The results show that the cooling and exhaust purifying effects of the compound (WHT+WHTA) micro-surfacing are the best, followed by WHTA micro-surfacing and WHT micro-surfacing. The cooling effect of environment-friendly cooling micro-surfacing increases gradually with the increase of pavement temperature. The outdoor cooling amplitude reaches 5.9 ℃ and the indoor cooling amplitude reaches 6.5 ℃. The purifying effect of COx, NOx and SO2 reaches 43%, and the purifying effect of particles with PM2.5 and PM10 reaches 59%. The change of temperature has a significant influence on the purifying effect of WHT and WHTA micro-surfacing, but the influence on the compound (WHT+WHTA) micro-surfacing is relatively small. Different types of environment-friendly micro-surfacing performs well. Functional materials disperse in emulsified asphalt stably and uniformly, which leads to the change of chemical functional groups. The cooling and purifying effect of the environment-friendly micro-surfacing is mainly derived from the self-polarization effect of functional materials caused by the crystal structure characteristics of the base materials.
  • Mechanical Property of Pavement Cement Concrete Under Dynamic Fatigue Load
    GUO Yin-chuan, SHEN Ai-qin, TIAN Feng, ZHOU Sheng-bo
    China Journal of Highway and Transport. 2017, 30(7): 18-24.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to explore the attenuation law of mechanical properties of pavement cement concrete under vehicle dynamic fatigue load, pavement cement concrete ratios with optimum mechanical property, durability and workability were proposed based on the orthogonal test. Three stress levels (i.e. 30%, 50% and 80%) were selected to design four different fatigue load schemes for the fatigue test. The residual strength and the change law of stress-strain curves of pavement cement concrete under different fatigue load schemes were measured by MTS and the classical theory of fracture energy was used to analyze the mechanical property of pavement cement concrete under dynamic fatigue load. The Results show that the residual strength of pavement cement concrete decreases under dynamic fatigue load with stress level of 80%, and the residual strength decreases by 20% after 4 hours' loading. When loading stress levels are 30% and 50% respectively, there is a negative attenuation of residual strength in the initial period of dynamic fatigue load and the residual strength increases by 7.9% and 3.1% respectively, after 3 hours' loading. The brittleness of pavement cement concrete increases, resulting from the dynamic fatigue load. The attenuation law of deformation is characterized by three stages, namely, elasticity, plasticity, and quasi-elasticity. With the increase of loading time and stress level, the fracture energy of pavement cement concrete gradually decreases. When the stress level is greater than 50%, the fracture energy deteriorates significantly under the fatigue load. When the stress levels are 30%, 50% and 80% respectively, the fracture energy of pavement cement concrete decreases by 24%, 57% and 66% respectively after 4 hours' loading, compared with the control specimen.
  • Analysis of Performance for Nano-ZnO Modified Asphalt Mixture
    CHEN Yuan-zhao, CHEN Ai-jiu, LI Chao-jie, LI Zhen-xia
    China Journal of Highway and Transport. 2017, 30(7): 25-32.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to investigate pavement performance of nano-ZnO modified asphalt mixture, firstly, nano-ZnO modified asphalt by the proportion of 1%, 2%, 3%, 4%, 5%, 6% and 7% was prepared in the light of high-speed shearing method and the contrastive analysis of basic properties were carried out between base asphalt and nano-ZnO modified asphalt. The DSR test, BBR test and Brookfield's viscosimeter test were carried out by selecting three doses of nano-ZnO modified asphalt at 1%, 4% and 7% respectively, to analyze pavement performance of nano-Zno modified asphalt. Secondly, the rutting test, immersion Marshall test, freeze-thaw split test and bending test at low temperature were carried out to analyze pavement performance of asphalt mixture systematically and modification mechanism was analyzed by infrared spectroscopy from micro perspective. The results show that three doses of nano-ZnO modified asphalt by the proportion of 1%, 4% and 7% can effectively improve high temperature properties, low temperature properties, viscosity and anti-fatigue properties of the asphalt. and optimal content is 4%. High temperature stability, water stability and low temperature crack resistance of nano-ZnO modified asphalt mixture by the dose of 4% reach the optimal state. The strength of nano particles can be fully utilized during the process of the preparation of Nano-ZnO modified asphalt based on high-speed shearing method. There may exist a physical-chemical reaction between Nano-ZnO modified asphalt and base asphalt,with the result of forming a stability of modified asphalt system. Meanwhile, softening point and consistency of the base asphalt can be improved. Under high-speed shearing action, chemical bonds of the melting base asphalt break and react chemically with the hydroxy groups on the surface of the nano-particles, with the result of forming a co-melting system of nano-particles and base asphalt.
  • Time History Analysis Method for Seismic Reliability of Bedding Rock Slopes Based on Newmark-β Method（in English）
    CHEN Xun-long, GAO Rong-xiong, GONG Wen-hui, LI Yi, PENG Yong-hao
    China Journal of Highway and Transport. 2017, 30(7): 33-40.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to improve the computational efficiency of the traditional time history analysis method for seismic response of bedding rock slopes and consider the random characteristics of earthquake in the selection method for evaluation index of dynamic reliability of slopes under earthquake action, a simplified calculation method for seismic response of bedding rock slopes was established using the Newmark-β method and Matlab/Simulink. And then the calculation methods for time histories of safety factor and reliability were further given based on the Monte Carlo method. According to the specified minimum of safety factor of slope stability in the technical specification for slope engineering and the maximum allowable failure probability of slope in practical engineering, two new evaluation indexes, that is, minimum safety-required reliability and maximum allowable failure reliability as well as the corresponding calculation methods were put forward. Moreover, dynamic reliability of slopes under earthquake action was comprehensively assessed by two new evaluation indexes. The results show that the proposed simplified calculation method for seismic response of bedding rock slopes is reasonable and feasible, with high calculation efficiency and accuracy. The proposed evaluation method for dynamic reliability of slopes by dint of two new evaluation indexes under earthquake action is reliable, compared with other evaluation methods. It takes the random characteristics of seismic reliability of slopes into account. Combining the seismic reliability of slopes with the technical specifications of slope engineering and practical engineering risks, the computing results can realistically reflect the security status of slope under earthquake action. Hence, the results with high rationality apply to the practical engineering.
  • Method for Determining Anti-slip Safety Factors Between Main Cable and Saddle in Suspension Bridge
    ZHANG Qing-hua, CHENG Zhen-yu, JIA Dong-lin, BAO Yi
    China Journal of Highway and Transport. 2017, 30(7): 41-49.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To precisely evaluate the anti-slip safety between the main cable and the saddle and guarantee the structure safety of multi-pylon suspension bridge, characteristics of the frictional resistance between the main cable and the saddle were investigated. The differential equation between lateral pressure and tension force of strands was established by analyzing the stress-strain relation of micro-body between strands. Meanwhile, a frictional resistance equation between the main cable and the saddle was established based on the lateral pressure expression. The method for determining anti-slip safety factors between the main cable and the saddle was proposed. The frictional resistance equation was validated by results of the model test. Moreover, determination methods of anti-slip safety factor as well as the influence of saddle design parameters on the anti-slip safety factor were discussed. The results indicate that the actual frictional resistance between the main cable and the saddle can be precisely determined by the proposed frictional resistance equation for the saddle with or without vertical friction plate. The existing way of defining anti-slip safety factor with ambiguous physical meaning and conservative values can't consider the influence of optimized saddle parameters on the improvement of anti-slip safety. These problems obstruct the overall design of the multi- pylon suspension bridge. The anti-slip safety factor expression with clearer physical significance is convenient for engineering application and can be taken as the major basis for determining anti-slip safety factor. The coefficients of friction between the main cable and the saddle as well as the saddle design parameters influence the frictional resistance to some extent. It is effective to improve the anti-slip safety through optimal saddle design parameters and the installation of vertical friction plates.
  • Simplified Calculation of First-order Longitudinal Natural Vibration Period of Cable-stayed Bridges Based on Energy Method
    ZHANG Wen-xue, KOU Wen-qi, CHEN Ying, DU Xiu-li
    China Journal of Highway and Transport. 2017, 30(7): 50-57.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In the simplified calculation of first-order longitudinal natural vibration period of cable-stayed bridges with the floating and tower-girder hinge system, the influence of bidirectional vibration coupling effect was neglected. Taking the situation into consideration, simplified formulas for calculating the first-order longitudinal natural vibration period of two kinds of cable-stayed bridges were derived by the Rayleigh energy method. Firstly, simplified calculation models of cable-stayed bridges with the floating and tower-girder hinge system were established respectively, on the basis of the transmission path of longitudinal inertial force under the action of earthquake. Secondly, in the light of assumed longitudinal and vertical displacement vibration equations of main girder and tower of cable-stayed bridges with floating and tower-girder hinge system, the deformation energy and kinetic energy of cables, main girder and tower of two kinds of cable-stayed bridges were analyzed and calculated respectively, considering the intercoupling between the longitudinal and the vertical modes. Finally, simplified formulas of first-order longitudinal natural vibration period for cable-stayed bridges with the floating and tower-girder hinge system were derived by energy conservation principle. The first-order longitudinal modal of five built-up bridges were analyzed by dint of the finite element software. Then theoretical results were compared with values calculated by the finite element method. The results show that results calculated by simplified formulas are in good agreement with values calculated by the finite element method. And the relative errors are less than 15%. The simplified calculation method with good stability can be used to estimate the first-order longitudinal natural vibration period. It provides a reference for preliminary design and scheme comparison of cable-stayed bridges by combing the simplified formulas for calculating the first-order longitudinal natural vibration period of cable-stayed bridges with floating system with ones with tower-girder hinge system.
  • Experimental on Partial Repair Technology of Light-weight Composite Bridge Deck Composed of Steel and UHPC Layer
    SHAO Xu-dong, LI Zhao-hui, WU Jia-jia, HUANG Xi-jun
    China Journal of Highway and Transport. 2017, 30(7): 58-64.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to solve problems of the partial demolition and the joint treatment in repairing the damaged area in the UHPC layer of composite bridge deck, a method of dismantling damaged area by pulling out the rebar in the UHPC layer was proposed. A new design with welding tensioned bar on the steel plate as joint was provided. To prove the feasibility of the demolishing method, demolition experiments of UHPC layer in designated areas were carried out using the full-scale test model. In order to verify the mechanical performance of the old-new UHPC joint, strength tests of horizontal joints and vertical joints were completed. The results show that the method is used to dismantle the damaged area of UHPC layer quickly. The new repair joint effectively boosts the tensile strength through welding tensioned bars in the position of joint on the steel plate. The cracking stresses of horizontal joints and vertical joints are 21.8 MPa and 17.4 MPa respectively, obviously larger than 9.8 MPa, the cracking stress of traditional joints. The cracking stresses of joints are 73.4% and 63.9% of cracking stresses of cast-in-place section respectively. The finite element analysis of Dongting Lake Bridge indicates that the maximum horizontal tensile stress and the maximum vertical tensile stress are 15.4 MPa and 5.4 MPa respectively, less than measured values. The new repair joint completely meets the requirement of tensile stresses in the UHPC layer.
  • Property of Mode-coupled Internal-resonance of CFRP Cables（in English）
    MEI Kui-hua, SUN Sheng-jiang, LI Xue-qin, JIN Guo-qing
    China Journal of Highway and Transport. 2017, 30(7): 65-72,85.
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    In order to investigate the mode-coupled internal-resonance characteristics of CFRP cables, a two-degree-of-freedom vibration model was established to reflect the first-order mode coupling of the cable in plane and out of plane. The geometrical nonlinearity caused by sag and large displacement of cables was taken into consideration. On the basis of the model, the internal resonance responses of CFRP cables and steel cables with the same conditions under pure plane and non-plane loads were analyzed by the numerical method. The effects of external excitation amplitude, damping ratio and initial disturbance on internal-resonance characteristics were investigated. The results show that when the frequencies of cables in plane and out of plane satisfy the resonance condition, the primary resonance in plane occurs along with the internal resonance in plane and out of plane. With the increase of the external excitation amplitude, the maximum displacements in plane and out of plane increase. When the external excitation amplitude is less than a certain value, the internal resonance is not likely to occur. With the increasing damping ratio, the maximum and steady-state amplitudes of cables tend to decline. When the damping ratios increase to a certain value, the internal resonance is not likely to occur. With the increase of the initial disturbance, the maximum amplitude and steady-state amplitudes of the cable almost remain unchanged but it is shorter for energy transferring from the in-plane to the out-of-plane. During the course of motion, the beat frequency of CFRP cable is significantly higher than that of the steel cable. It is more quickly for the CFRP cable from transient vibration to steady motion. In particular, the maximum amplitude and steady amplitude of CFRP cable are much smaller than those of the steel cable.
  • Theoretical Analysis of Mechanical Properties for Continuous Deck Structure of Simply Supported Beam Bridge
    ZHUANG Yi-zhou, XU Liang, CHENG Jun-feng, LAI Huan-lin
    China Journal of Highway and Transport. 2017, 30(7): 73-85.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In allusion to problems that continuous deck structure of simply supported beam bridge was vulnerable to crack, leak and edge failure, a formula of stress in the continuous deck structure under the combination of vehicle loading and the temperature effect was deduced by structural mechanics in terms of linear elastic theory. Furthermore, the formula was verified by the ABAQUS, considering a certain project as an example. Based on the comprehensive analysis of mechanical properties for the continuous deck structure, it was found that main factors were thickness, unbounded length and material types. Influences of above parameters on the stress and mid-span deflection of continuous deck structure were considered according to the further analysis. Meanwhile, main parameters influencing the stress of continuous structure on deck were analyzed as well. The results show that the formula can be used to accurately calculate mechanical parameters for continuous deck structure under vehicle loading and the temperature effect. The stresses at the top and bottom of concrete pavement decrease dramatically with the increase of pavement thickness and the maximum stress on top surface is in linear relationship with thickness. Comparing the asphalt concrete pavement with the conventional concrete pavement, the maximum principal tensile stresses of them on top surfaces are almost the same, but the latter has much larger tensile stress on bottom surface. It is reasonable to combine the asphalt concrete pavement with the cast-in-place concrete pavement. It is effective to increase the thickness of concrete pavement and set unbounded areas for the improvement of mechanical properties. Setting the unbounded area will be the most efficient way to remarkably reduce the maximum tensile stress on the deck when the unbounded length is about 5% of each span. In a word, the results provide a theoretical guide for the mechanical calculation and an accurate method of continuous deck structure of simply supported beam bridge.
  • Influence of Combined Central Stabilizing Plates on Flutter Performances of Box Girder
    XIA Jin-lin, YANG Yong-xin, GE Yao-jun
    China Journal of Highway and Transport. 2017, 30(7): 86-93.
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    In order to compare flutter performances of sections with different heights of both one-sided and combined plates and investigate their diverging mechanisms under various attack angles, a series of wind tunnel tests on sectional model were carried out in allusion to a given single-box suspension bridge. The influence of one-sided stabilizing plates under attack angels of 3°, 0° and -3° respectively on flutter performances was firstly investigated. Then, effects of wind resistance under corresponding attack angles were explored by simultaneously changing the height of central stabilizers at both sides. Moreover, values of the optimal height of combined stabilizing plates was given. Finally, the diverging mechanism for the initial section and the optimal section was compared by 2d-3DOF method. The results show that flutter critical wind speed of one-sided central stabilizing plates increases first and then decreases with the increasing height of stabilizing plates. The flutter critical wind speed of stabilizing plates with the proper height grows to some extent. Compared with one-side stabilizing plates, a section with combined plates is better to improve the aerodynamic stability. The 2d-3DOF analysis indicates the flutter diverging mechanism is dramatically changed by central stabilizing plates. The variation trends of the aerodynamic damping with wind speed are obviously different in the optimal section and the initial section.
  • Test on Flexural and Shearing Performance of Concrete-encased Composite Girder with Corrugated Steel Webs
    HE Jun, LIU Yu-qing, LU Zhan, LI Chuan-xi
    China Journal of Highway and Transport. 2017, 30(7): 94-100,143.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to improve the mechanical performance of composite girder with corrugated steel webs under hogging moment and avoid the shear buckling of the corrugated webs and local buckling of compressive flange, measures of concrete-encased composite girder with corrugated steel webs were proposed. Two specimens with different flexure shear ratios were designed and model tests on concrete-encased composite girders with corrugated steel webs were conducted to investigate the mechanical performance under combined shear force and bending moment, understand the effects of flexure shear ratios on the ultimate load-carrying capacity and failure modes, and establish correlation equations under shear force and bending moment. The results show that composite girders are failed due to the interaction of flexural and shearing forces and both flexural cracks and shear cracks appear on encased-concrete. The flexure shear ratio has a slight effect on the shear stiffness of un-cracked section, but a large effect on the shear stiffness after concrete crack. With the increase of flexure shear ratio, the cracking load decreases, but the structural ductility increases. In addition, the un-cracked sections satisfy the assumption of plane section under shearing and flexural loads. However, after concrete crack in the tensile region, the strain of corrugated web at the corresponding positions becomes small on account of “accordion effect”. The strain is almost zero in flat plate areas but recognizable strain in skew plates is not zero because of the compression of concrete. Finally, based on model test and numerical simulation results, load-carrying capacity evaluation rules of concrete-encased composite girder with corrugated steel webs under shearing and flexural loads are established, to provide a reference for further designs.
  • Experiment on Ground Deformation During Tunneling and Pre-arch Stress by Pre-cutting Method
    WANG Xiu-ying, WANG Teng, LI Kong-ming, HE Mei-de, LUO Ping
    China Journal of Highway and Transport. 2017, 30(7): 101-109.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To clarify the mechanic response of ground and pre-arch by pre-cutting method during tunneling, the 3D geo-mechanics model test of large scale 1∶10 was designed to factually simulate the process of the grooving, pouring concrete and the full face excavation in the light of pre-cutting method. Ground deformation during tunneling and pre-arch stress were investigated. Earth pressure and strain of pre-arch were obtained by setting measuring points of displacement, pressure and strain in the model soil. Through analyzing the obtained data and comparing it with the result of numerical simulation, the development of the ground deformation, stress characteristics of the pre-arch and the key problems during tunneling were further investigated. The results show that the influence of pressure and timeliness of concrete pouring on the quality of pre-arch is great. Compared with pre-cutting and pouring concrete process, ground settlement during soil excavation protected by the pre-arch is much smaller. It shows that core soil of the face can be protected by the pre-arch, the convergence deformation significantly decreases, and ground settlement can be effectively controlled. The sidewall and the haunch are in compression but the arch is in tension. The pre-arch poured by plain concrete is easy to be destroyed and hence tensile properties of the pre-arch should be enhanced in projects design.
  • Signal Control Method for Bus Priority at Intersections near Subway Stations Considering Pedestrian Crossing（in English）
    LIU Yu-gang, LI Jia-li, LI Jun-bo, YANG Hong-tai, LI Ming
    China Journal of Highway and Transport. 2017, 30(7): 110-118.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to take into full account the influence of pedestrian crossing on signal control for bus priority at intersections near large-scale public facilities such as subway stations and solve problems that the delay of pedestrian crossing was not considered in the traditional signal control method for bus priority (SCMBP) resulting in long resistance time of pedestrians, a novel priority control method was proposed in consideration of the delay of pedestrian crossing, bus, and users of private vehicles at intersections. Four scenarios were categorized based on the flow of pedestrians and private vehicles, that is, high pedestrian volume and traffic volume, high pedestrian volume and low traffic volume, low pedestrian volume and traffic volume as well as low pedestrian volume and high traffic volume. By virtue of the first three scenarios, a bi-level programming model was established to maximize the road capacity and to optimize the delay of bus passengers, social vehicle users, and crossing pedestrians. Meanwhile, a multi-objective programming model with the purpose of maximizing the benefit of all road users at an intersection was established. The genetic algorithm was used to solve the two programming models. Moreover, the delay of bus passengers, private vehicle users, and pedestrians before and after adopting the proposed method were compared. The results show that the delay of crossing pedestrian can be greatly reduced with a slight increase in the delay of bus passengers and users of social vehicles. Compared with the traditional SCMBP, the pedestrian's delay may decrease by 59% at the state of high pedestrian volume and traffic volume, in the light of this method. At the state of high pedestrian volume and low traffic volume, the pedestrian delay decreases by 41% and at the state of low pedestrian volume and high traffic volume it decreases by 195%. It proves that the SCMBP considering pedestrian crossing is efficient, fair and practical, with the maximum benefit.
  • Influence of Change of Public Transportation Service Quality on Travel Mode Choice Behavior
    YUN Mei-ping, LIU Guang-yang, LIU Fang
    China Journal of Highway and Transport. 2017, 30(7): 119-125.
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    In order to investigate the influence of service quality change of public transportation on residents' travel mode choice behavior, pooled cross-section data was formed by collecting the residents' travel survey data in Zhongshan City in 2009 and 2015 and a multinomial Logit (MNL) model was established by dint of disaggregate analysis and statistic analysis. Influence factors of travel mode choice behavior at any time, change of travel mode choice behavior based on result of model and statistics and the influence resulting from service quality change of public transportation were analyzed. The results show that compared with 2009, there is a big change of travel behavior in 2015. Fewer people travel by motorcycle and bike and more people select bus and car. In addition, the time of waiting for a bus replaces the walking time from home to bus stop becoming the main influence factor on travel behavior. What's more, the time of waiting for a bus continuously increases but walking time from home to bus stop gradually decreases from 2009 to 2015. The evolution of public transportation service quality affects travel mode choice behavior and poor public transportation service quality is the main influence factor. When an index of service quality is getting worse, it will gradually become the main influence factor of travel mode choice behavior. When an index of service quality is getting better, it will not be the main influence factor any more.
  • Travelers' Perception Differences in Travel Time Reliability and Crowding of Mode-choice in Multimodal Networks
    GAO Kun, TU Hui-zhao, LI Hao, SUN Li-jun
    China Journal of Highway and Transport. 2017, 30(7): 126-133.
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    In order to provide the foundation for scientific utilization of the traffic facilities in multimodal networks, an experimental design of SP survey for investigating mode choice behavior was proposed by the principles of utility balance and graphic design philosophy, incorporating several influencing factors (cost, travel time, travel time reliability and in-vehicle crowding) and multiple traffic modes (self-driving, metro, park and ride, bus). One-to-one and face-to-face surveys were conducted to collect efficient behavioral data. Discrete choice technology was applied to quantitatively analyze the effects of various factors on mode choice, explore mode choice behavior in multimodal networks and investigate the perception differences in travel time reliability (TTR) and crowding in particular. The results show that the perceived value of TTR of metro is 59.8% and 32.1% higher than that of bus and car respectively. The value of crowding in bus is 26% and 84% higher than that in metro and P&R. There exist perception differences of travelers on TTR and crowding of different modes. The perception differences should be taken into full consideration, on account of remarkably influencing the precision of forecasting models of mode choice. Furthermore,travelers' values in TTR and crowding highly influence the mode choices of commuting. The values of average time and TTR are 49.8 RMB·h-1 and 81.97 RMB·h-1 respectively. Travelers tend to increase 50% travel time to avoid overcrowding in vehicles. The estimated willing-to-pays can be used in planning and appraisals of traffic facilities in multimodal networks.
  • Taxi Commute Recognition and Temporal-spatial Characteristics Analysis Based on GPS Data（in English）
    FU Xin, SUN Mao-peng, SUN Hao
    China Journal of Highway and Transport. 2017, 30(7): 134-143.
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    In order to investigate the commute behavior by dint of taxi and temporal-spatial distribution characteristics of urban residents' travel activities, based on vehicle trajectory data generated by Taxi GPS device, the pick-up and drop-off information of commuters' travel by taxi was distinguished by geographic information database processing and GIS technology. On the basis of Traffic Analysis Zone (TAZ) division, the OD matrix of travel by taxi was established and the identification model of commute amount based on trajectory data was proposed. The compute model of commute time and distance was established to analyze temporal-spatial characteristics of compute behavior. Additionally, taken Xi'an as an object of the research, the empirical analysis of established models was carried out. The results show that the fluctuation coefficient of taxi traffic flow in each traffic zone is stable at 0.2. Average computing traffic flow of morning rush hours on weekdays is about 20 000 to 27 000 vehicles per day, and there are 15 000 to 27 000 vehicles per day in evening rush hours. Traffic flow in rush hours on Monday and Tuesday are relatively stable, with a slight increase from Wednesday to Friday. Average traffic flow is basically the same in morning and evening rush hours. The number of commuters by taxis on Tuesday is large, which becomes relatively less on Thursday.The scale of commuting travel by taxi in morning rush hours on weekdays during the whole month is about 27% of mean value of daily traffic flow in rush hours. The average commute distance of taxi is 3.7 km and the commute distance is mainly in the range of 2.5 km to 7 km. The average commute time is 17 min and the commute time is mainly distributed between 10 mins to and 20 mins. The recognition results of employment place and residence area are consistent with the actual conditions of land use. The method presented in this paper is available to identify commute behavior, workplace, residence, with providing the basis for urban traffic system optimization of commuter services and heterogeneity analysis of spatial activities.
  • Research on Side Impact Test Parameters Based on AEMDB
    MA Wei-jie, YIN Feng-xuan, ZHU Hai-tao, LI Xiang-rong
    China Journal of Highway and Transport. 2017, 30(7): 144-150.
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    In order to effectively identify the passive safety performance of the vehicle in terms of the new edition of China New Car Assessment Program (C-NCAP), main parameters influencing safety performances of vehicle side impact were determined and “average” models representing the vehicle characteristics of China were put forward by the statistical analysis of apparent parameters of existing vehicles in China. And then mobile barrier parameters in line with traffic conditions in China were proposed and compared with the parameters prescribed in C-NCAP and Europe New Car Assessment Program (Euro-NCAP) in 2015. Three side impact tests of full-scale vehicle with the same model were carried out based on all three types of mobile barriers. Besides, an evaluation method of the side impact in accordance with the actual situation in China was proposed. The results show that different mobile barriers have considerable influences on the vehicle side door deformation, intrusion rates of the door and the dummy injury. The larger mass the mobile barrier is, the higher the terrain clearance of the lower edge of honeycomb aluminum bumper can be. The door intrusion rate increases with the increasingly serious door deformation. It is clear that dummies in tests get injured much earlier by employing the new type of mobile barrier and the barrier prescribed in Euro-NCAP in 2015. Meanwhile, the peak of the new type of mobile barrier is higher. Hence, the results have great influences on the development of vehicle passive safety in China and the promotion of side safety protection of vehicles.
  • Crashworthiness Research on Novel Multi-cell Thin-walled Structure of Varying Cross-sections
    ZHANG Yong, XU Xiang, LI Qi, LU Ming-hao, LIAO Shui-rong
    China Journal of Highway and Transport. 2017, 30(7): 151-158.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To further improve the crashworthiness of multi-cell structures under axial loading, a novel multi-cell thin-walled structure with varying cross-sectional shapes, formed by rotating internal ribs of the traditional multi-cell structure, was proposed. Hence, cells in the same cross-section appeared inhomogeneous characteristics. Combined with experimental and numerical finite element methods, the crashworthiness of multi-cell structure and varying cross-sectional multi-cell structure with different positions of rotation axes, rotation angles and wall thickness was compared by regarding peak crushing force and special energy absorption as indicators. Furthermore, to explore the potential of the crashworthiness of the multi-cell structure in varying cross-section, the multi-objective optimization was performed by dint of Kriging approximation techniques and multi-objective particle swarm optimization (MPSO) method. The Pareto frontier and the optimized parameter matching under different design requirements were obtained. The results show that the position of rotation axes, rotation angles and wall thickness have significant influences on the specific energy absorption of multi-cell structure in varying cross-section, but the position of rotation axes and rotation angles have a limited effect on peak crushing force. Moreover, the specific energy absorption of the multi-cell structure in varying cross-section is about 8% higher than that of the traditional multi-cell structure. When the maximum peak of crushing force is limited in the range of 180 kN, the optimal design parameters of wall thickness t and the rotation angle θ are 1.52 mm and 1.85 degrees respectively.
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