20 June 2018, Volume 31 Issue 6
    

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  • Review on China's Road Construction Machinery Research Progress: 2018
    Editorial Department of China Journal of Highway and Transport
    China Journal of Highway and Transport. 2018, 31(6): 1-164.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To promote the development of road construction machinery discipline in China, the research progress, hot topics, existing problems, specific countermeasures and development prospects of academic research in road construction engineering at home and abroad were systematically summarized from six aspects, including earthmoving machinery, compact machinery, pavement construction machinery, bridge machinery, tunnel machinery and maintenance machinery. In the aspect of the earthmoving machinery, the bulldozer, the excavator, the loader, the grader and so on were reviewed. Reviews of the compact technology and equipment included the static roller, the tire roller, the circular vibrating roller, the vertical vibrating roller, the impact roller, the intelligent compaction technology and equipment and so forth. Reviews of the road construction machinery included the asphalt mixing plant, the asphalt paver, the concrete batch plant, the concrete paving equipment, the stabilized soil mixing plant, etc. Reviews of the bridge machinery included the bridge girder erection machine, the moving form work bridge machine, etc. Reviews of the tunnel machinery included the ejector anchor machine, the shield tunneling machine, etc. As for the maintenance machinery, the sweeping machine, the deicing equipment, the inspection equipment, the asphalt miller, the recycler, the sealer, the cement road repair equipment and so on were reviewed. It is supposed to provide new perspectives and basic data for academic researches on road construction machinery engineering discipline.
  • Rheological Mechanical Properties of DCLR-modified Asphalt Binders
    LUO Rong, XU Yuan, LIU Han-qi, ZHANG De-run, FENG Guang-le
    China Journal of Highway and Transport. 2018, 31(6): 165-171.
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    To investigate the rheological mechanical properties and evaluate the effect of modification of direct-coal-liquefaction residue (DCLR)-modified asphalt binders, the dynamic shear rheometer (DSR) was employed to perform the time and temperature sweep tests, multiple stress creep and recovery (MSCR) tests, and time sweep tests at different stress levels on 90# base binders (before modification) and DCLR-modified binders (after modification). These tests were used to evaluate the stiffness, permanent deformation resistance, and fatigue cracking resistance of DCLR-modified binders, respectively. The results indicate the following. 1) The dynamic shear modulus of DCLR-modified binders is higher/lower than that of 90# base binders at low/high frequency; overall, the stiffness of DCLR-modified asphalt binders is higher than that of 90# base binders and the stiffness of DCLR-modified binders decreases less significantly than that of 90# base binders, which suggest reduced temperature susceptibility of DCLR-modified binders. 2) By comparing the nonrecoverable creep compliance and percent recovery of DCLR-modified binders and 90# base binders at different temperatures, it is observed that the nonrecoverable creep compliance of DCLR-modified binders is less and the percent recovery is greater than that of 90# base binders at the same temperature, which indicates that the permanent deformation resistance and recovery potential of DCLR-modified binders are significantly better than that of 90# base binders. 3) By comparing the fatigue lives of two binders at different stress levels, the resistance to fatigue cracking of DCLR-modified binders is observed to be greatly enhanced compared to that of 90# base binders; moreover, the power function can be employed to illustrate the variation of fatigue life with stress levels for both asphalt binders with satisfactory goodness of fit.
  • Constitutive Model and Bond Stress-slip Behavior Between Rebar and Steel Fiber Reinforced Recycled Concrete（in English）
    GAO Dan-ying, ZHU Qian
    China Journal of Highway and Transport. 2018, 31(6): 172-180.
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    To promote the application of steel fiber-reinforced recycled concrete (SFRAC) in road and bridge engineering, 11 different mixture proportions of SFRAC were designed and a total of 33 bond specimens of rebar and SFRAC were cast with the test parameters of the recycled coarse aggregate (RCA) replacement ratio (0%, 30%, 50%, and 100%) and steel fiber contents (0%, 0.5%, 1.0%, 1.5%, and 2.0% by volume). Pull-out tests were conducted for the bond specimens between the rebar with strain gauges inside and SFRAC. It was found that there were two or three bond stress peak values in the bonding segment between the rebar and SFRAC. The change in the bond stiffness at the different bonding positions is the main reason for the non-uniform distribution of the bond stress. The uniformity of the bond stiffness in the bonding segment increases by increasing the replacement ratio of the RCA, and 50% is the optimal replacement ratio of RCA. This is also improved by adding steel fibers into recycled aggregate concrete (RAC), but their effect decreases when its volume fraction is 2.0%. Furthermore, the relative slip at the loading end increases with the increasing replacement ratio of the RCA and decreases with the increasing volume fraction of the steel fibers. The uniformity of the bond stiffness in the bonding segment is improved with increasing replacement ratio of the RCA and volume fraction of the steel fibers. The peak values of the bond stress in the bonding segment next to the free end increase with increasing replacement ratio of the RCA and has little relation with volume fraction of the steel fibers. The shape of the bond stress and slip curve between the rebar and SFRAC does not change with the bonding positions. Finally, a constitutive model for the bond stress-slip relation of the rebar embedded in the SFRAC is proposed, which considers the influence of the replacement ratio of the RCA and volume fraction of the steel fibers.
  • Uniaxial Compression Test of Geosynthetic-encased Stone Columns
    CHEN Jian-feng, ZENG Yue, FENG Shou-zhong, LI Li-hua
    China Journal of Highway and Transport. 2018, 31(6): 181-187.
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    Geosynthetic-encased stone columns (GESCs) are a new type of column bodies for a composite foundation. In this work,12 large-scale samples of GESCs with 300 mm diameter and 600 mm height were made using gravels of three different relative densities (Dr=0.42,0.62,0.78), and seamless sleeves of four different strengths (T=33, 43, 52, 65 kN·m-1) were also made using polypropylene woven geotextiles. These samples were used for studying the strength and deformation characteristics of GESCs subjected to a uniaxial loading, and subsequently to establish a method to determine their strength and modulus. Uniaxial compression tests were performed on the samples until failure. The results show upward concave stress-strain curve of GESCs at the preliminary loading stage presumably due to the initial densification of gravels under the uniaxial compression. After the initial nonlinear stage, stress increases approximately linearly up to the strength of GESCs, and subsequently decreases, indicating strain-softening characteristics. Once the loading approaches the strength of GESCs, the GESC bodies apparently bulge in the middle, where the horizontal slices of the geotextiles break sequentially until failure of the GESCs. Therefore, the strength of the horizontal slices ultimately controls the strength of GESCs. The bearing capacity of GESCs can thus be enhanced in practice by strengthening the horizontal slices. The strength of the GESCs is independent of the relative density of gravels but varies somewhat linearly with the geotextile strength. The strength of the GESCs can, therefore, be determined from that of the geotextile. The modulus of the GESCs apparently increases with an increase of either the geotextile strength or the gravel density, however, for a fixed gravel density the modulus increases linearly with the geotextile strength. A theoretical formula was established to compute the modulus of the GESCs. The formula was verified with the test data, and a correction factor of κ=2.4 was obtained to arrive at a better agreement with the test results.
  • Dynamic Early Warning Analysis and Safety Classification of Slope with Single Sliding Plane Based on Monitoring of Fully Grouted Bolts
    YAN Chang-gen, SUN Wei-feng, XU Wei, LIU Bao-jian
    China Journal of Highway and Transport. 2018, 31(6): 188-194,226.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The purpose of this study is to improve the slope warning system using a monitoring method of fully grouted bolts and to promote the extensive application of this method. Experiments were conducted to determine the monitoring bolts' early warning thresholds and the safety classifications of slopes with a single sliding plane, based on the actual mechanical characteristics of bolts and the instability evolvement rule of slopes. First, for slopes with a single sliding plane using fully grouted bolt monitoring, when the strengthening and monitoring bolts are constructed and the grouting strength of bolts reaches a stable value in a short time, the slope reaches a steady state of stress adjustment and deformation development, which is identified as the initial monitoring state of the slope. Second, considering the negative evolutions of shear strength parameters of sliding planes, hydraulic pressure on the sliding plane, or earthquake, a numerical simulation analysis of plane strain is proposed to determine the sequences, relative to the initial monitoring state of the slope, on the incremental accumulation of monitoring fully grouted bolts' axial force. Third, relative to the initial monitoring state of the slope, the increment of slope sliding force and the reduction of slope anti-sliding force induced by the negative evolutions are obtained using limit equilibrium stability analysis of slope, thereby obtaining a fitting function with the incremental accumulation of monitoring fully grouted bolts' axial force, and establishing a computational formula on the dynamic stability factor of the slope with the accumulation of monitoring fully grouted bolts' axial force. According to the regulations on slope safety classification and early warning in the Technical Code for Building Slope Engineering (GB 50330-2013) etc., early warning classifications of the slope using a monitoring method of fully grouted bolts are blue:without alert, yellow:low alert, orange:mid alert, and red:high alert. Finally, the slope example with a single sliding plane using the monitoring method of fully grouted bolts and its two independent calculation conditions of negative evolutions was designed to interpret the process of the proposed method for dynamic early warning analysis and safety classification of the slope. For similar slopes, it is first suggested to reasonably pre-judge the negative evolvement rules of slope negative influences combining the existing relevant information, and then to apply the proposed method to complete the analysis and obtain a reliable early warning result.
  • Numerical Simulation of the Mechanical Characteristic and Failure Mode of Karst Subgrade
    WEI Feng, CHEN Zhong-da, CHEN Zhi-feng, ZHANG Zhen, ZHU Yao-ting, HU Wen-hua, WU Fu-quan
    China Journal of Highway and Transport. 2018, 31(6): 195-206.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To reveal the mechanical characteristic and failure mode of the Karst subgrade, a Karst cave model was established that considers the formation distribution, shape of the cave, and location of the cave based on the study results. The staged modeling method was adopted to simulate the layered filling process of the subgrade. The force method and the strength reduction method were used to analyze the mechanical characteristic and its effect on the failure mode. A multipoint displacement meter was used to monitor the deformation and failure process of the Karst subgrade during the subgrade filling process. Then, a numerical model was established to reproduce the failure process. According to stress state and the Hoek-Brown strength envelope, the failure modes are divided into tensile failure, tensile shear failure, and compression shear failure. The influences of roof tilt angle and cave shape were analyzed. Based on the bending theory, the analytical solution of the allowable subgrade filling height was derived. Then, corrections were made according to the ground stress and the arch effect. It is observed that the flexural tensile stress in the cave roof may be counteracted due to the arching effect and the compression of ground stress, leading to the formation of a shear plastic state, rather than a stretched plastic state. In the past, the calculation results of bending stress based on the simply supported beam assumptions are relatively large, due to the failures of considering the arch effect and the compressive effect of the ground stress. The stress state of the roof of the rectangular cave is mainly tensile shear, whereas the roof of the elliptical cave is mainly compression shear, and the stability of the actual shape of the cave is between the two. The inclination of the roof (within 25°) has no obvious influence on the size and stability of the roof, but the stress model of the roof of the cave may shift from the compression shear zone to the stretching shear zone. To prevent Karst instability, the subgrade filling height should be reasonably controlled; however, the current regulations are too conservative to allow the thickness-to-span ratio to be smaller than 0.8. The antibend estimation method was observed to be better than the thickness-to-span ratio evaluation method, but it is still somewhat conservative. The revised antibend estimation method that considers the ground stress and arch effect is closest to the actual engineering fact and numerical calculation results.
  • Experimental and Numerical Investigations on Aerodynamic Admittances of Section Models
    ZHANG Wei-feng, ZHANG Zhi-tian, ZHANG Xian-xiong, CHEN Zheng-qing
    China Journal of Highway and Transport. 2018, 31(6): 207-216.
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    The authors reviewed some fundamental assumptions that lead to aerodynamic load theories of two-dimensional thin airfoils to further investigate the aerodynamic admittance of two-dimensional thin airfoil theories used in bridge aerodynamics, which adopts the concept of aerodynamic admittances determined uniquely by the dimensionless frequency and independent of wind field properties. These basic conditions do not hold for bluff bridge deck sections, so that aerodynamic admittance functions that are independent of the wind field properties are not available. Based on this theoretical viewpoint, the fluctuating lift forces of a flat plate and a rectangular section with an aspect ratio of 4 were measured through wind tunnel pressure measurement tests in three types of nonuniform arrangement grid-turbulence wind fields, and the aerodynamic admittance functions were identified. By comparing the aerodynamic admittance functions identified in different wind fields, the dependence of the cross sections on wind fields was investigated. The results were further verified using CFD simulations in three types of turbulent wind fields by changing the inlet boundary conditions. The results indicate that for a thin plate, the identified aerodynamic admittance functions from three different wind fields cohere with each other, indicating insensitivity to the oncoming wind field. In contrast, for a bluff rectangular section, the aerodynamic admittance functions from the wind fields differ significantly. This indicates that the aerodynamic admittances of bluff sections are functions that are not uniquely determined by the sectional configuration, but rather jointly determined by the configuration and wind properties. The results presented in this paper show that caution should always be applied in the application of airfoil-originated concept of aerodynamic admittance to bridge aerodynamics, and the wind field used to identify the aerodynamic admittances should be in accordance with the actual wind field characteristics.
  • Analysis on Distortion Effect of Non-prismatic Composite Box Girders with Corrugated Steel Webs Based on Newmark Method
    LI Li-feng, ZHOU Cong, WANG Lian-hua, REN Hong-chang
    China Journal of Highway and Transport. 2018, 31(6): 217-226.
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    To investigate the distortion effect of non-prismatic composite box girders with corrugated steel webs (CBGCSWs) under eccentric loads, the in-plane and out-of-plane force systems of an infinitesimal segment of non-prismatic CBGCSWs were first established, ignoring the axial stiffness of the corrugated steel web in the longitudinal direction. Then, by taking the distortional angle as the unknown, the governing differential equation for distortion of non-prismatic CBGCSWs was derived. Finally, the governing differential equation was solved using the Newmark method based on the theory of conjugate beam; thus, the calculation theory for the distortional warping normal stress of non-prismatic CBGCSWs under eccentric loads was established. Taking a large-span non-prismatic CBGCSWs bridge as the case study, the distortional warping normal stresses of angular points of the bridge under four different cases were obtained using the proposed method. The theoretical values were compared with results obtained using the three-dimensional finite element method. The results showed good agreement, indicating that the values obtained from the proposed method are accurate and can be applied in projects as reference. Based on this, the ability of non-prismatic CBGCSWs to resist distortion was compared with that of the corresponding PC box-girder, and the effects of the diaphragm spacing, the depth to span ratio, the width to span ratio, and the dimensions of corrugated steel web on the distortional warping normal stress were investigated. The results show that using the corrugated steel webs to replace concrete webs would largely weaken the ability of the box-girder to resist distortion, and this phenomenon should be further explored. In addition, the effects of the diaphragm spacing and the width to span ratio on the distortional warping normal stress are significant, while the depth to span ratio and the dimensions of corrugated steel web have minimal effect.
  • Evaluation of Reinforcement Effect of an RC Tied Arch Bridge Based on Vehicle Bridge Coupled Vibration
    LUAN Juan, HAO Xian-wu
    China Journal of Highway and Transport. 2018, 31(6): 227-234.
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    To evaluate the reinforcement effect on the bridge-coupled vibration analysis of a reinforced concrete (RC) tied arch bridge adopting the active reinforcement method, ANSYS software was used to establish the space beam, plate, and bar element of the bridge beam finite element model first, and then a three-axis nine degrees of freedom (9-DOF) vehicle model and a road surface roughness of level B were selected to simulate the actual vehicle and bridge deck status. Subsequently, the beam model was transferred to BDANS software to calculate bridge dynamic displacement, acceleration response by numerical simulation, and vehicle and bridge dynamic responses to study the dynamic impact on the modeled bridge section before and after reinforcement. Simultaneously, the spectral characteristics of acceleration response at different positions before and after bridge reinforcement were analyzed. Finally, the measured value and the theoretical value based on the engineering dynamic characteristics, dynamic response, and axle-axle coupling effect were compared and analyzed. The results show that the vertical natural frequency of the structure after reinforcement is higher than that before reinforcement; however, the improvement is low. The dynamic response at different positions of the structure before and after reinforcement tends to increase with increasing vehicle speed, and when the speed is in the range of 60 km·h-1 to 80 km· h-1, the dynamic response of the mid-section of the structure decreases the most after reinforcement and the root mean square acceleration of the structural control section after reinforcement is less than that before reinforcement. According to the magnitude of the change, it is suggested that the speed of the vehicle passing through the bridge structure should be 60 km·h-1 or less to ensure the comfort level, traffic efficiency, and traffic safety of pedestrians crossing the bridge. Through comparison of the theoretical and measured values, the validity of this method based on the analysis of bridge-coupled vibration to model the in-service performance of the bridge structure is verified.
  • Experimental and Numerical Simulation Analysis of Temperature Field of Tunnel Fire with Different Fire Source Areas（in English）
    CHEN Chang-kun, WANG Wei-yu, KANG Heng, SHI Cong-ling, LIU Xuan-ya
    China Journal of Highway and Transport. 2018, 31(6): 235-243.
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    In this study, a 1/9 scaled tunnel was established, and experiments and numerical simulations were carried out using the LES method for three different fire source areas to investigate the distribution rules of temperature in a tunnel exposed to fire and provide a reference for tunnel fire protection design and rescue. The distribution characteristics of temperature along the tunnel ceiling and cross-section, as well as the heat release rate and the behaviors of fire overflow at the tunnel entrance were determined and analyzed. The experimental and numerical results indicate that small area tunnel fire is mainly controlled by the fuel owing to the relatively abundant air, and the temperature at the center of the combustion region is significantly higher than the temperature at the two sides and it continues to decrease along the longitudinal direction. Furthermore, the temperature distribution is stable and obvious stratification occurs. It was found that the simulation results of FDS and the experimental results are in good agreement. For large area tunnel fire, the combustion is mainly controlled by the ventilation owing to the relatively abundant air supply, and the fire intensity at the middle of the combustion region decreased owing to limited ventilation and lack of oxygen; thus, the temperature decreased, while fire on both sides is relatively intense. As burning on both sides enters a weak phase, flammable vapors on both sides are reduced, and fuel in the middle of the combustion region burns intensely again owing to the abundant air supply. In this case, the simulation by FDS can also reflect the development of the fire. However, the simulation results indicate that the rate of increase of the temperature in the tunnel is higher and the combustion inhibition effect is more evident in the middle of the combustion region at the developing stage of the combustion. In addition, the growing trend of fire overflow of FDS is essentially consistent with the experimental results, and the simulation results can provide further details of fire overflow.
  • Dynamic Response of a Submerged Floating Tunnel During Non-contact Underwater Explosions
    LUO Gang, PAN Shao-kang, ZHOU Xiao-jun, CHEN Jian-xun, DAI Bing-qiang
    China Journal of Highway and Transport. 2018, 31(6): 244-253.
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    To study the regularity of the kinematics and dynamics of a submerged floating tunnel (SFT) subjected to near-field non-contact underwater explosions, fluid-solid coupling was employed and the problem of how to simulate a flow field with strong discontinuities was considered using the Arbitrary Lagrange Euler (ALE) coupling method. Explosive gas and water pressures were simulated using the Jones-Wilkins-Lee (JWL) and Mie-Gruenisen equations, respectively. To calculate the aforementioned problems, the LS-DYNA finite element kinetics program based on the potential flow theory and boundary element method was adopted. This study investigated the effects of three support systems (vertical, inclined, and combine the two cases) as well as the explosive quality and distance to the explosion center based on the displacement, velocity, acceleration, and stress of the SFT. The results indicated that after a non-contact explosion, the three support systems had a slightly different effects on the displacement, velocity, acceleration, and stress of the SFT. The cable axial force of the vertical support system was considerably less than that of the other two cases under the same explosive load. Compared with that of the vertical support system, the maximum cable axial force of the combined and inclined support systems was 296% and 283% higher, respectively. The displacement, velocity, and stress of the SFT increased linearly with increased explosive quality, and the acceleration was approximated by a parabolic increase. The accelerations of the SFT at midspan caused by the 200 kg and 500 kg explosives were 26.2% and 223% greater, respectively, than the acceleration caused by the 100 kg explosives. The explosive quality was a key factor that affected the security and stability of the SFT structure. The displacement, velocity, acceleration, and stress of the SFT experienced a reduction in power function with the increase in distance to the explosion center. In terms of acceleration, compared with the 2 m distance to the explosion center, the acceleration peaks were reduced by 73.2%, 94.2%, and 97.5% under the 5 m, 10 m, and 20 m operating conditions, respectively. In addition, the allowable explosive quality and safety distance were calculated by regression analysis and by using a fitting function, which provided a basis for a security evaluation of the SFT under a non-contact underwater explosion load.
  • Deformation Law and Flexible Formwork Support Technology of Soft Rock Tunnel Based on Force Analysis of Rock Bolt
    YU Yuan-xiang, CHEN Bao-ping, ZHANG Tao, ZHANG Jie
    China Journal of Highway and Transport. 2018, 31(6): 254-263.
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    Information on the range of deformation and the displacement of surrounding rock under support conditions provides an important theoretical basis for a reasonable determination of the reserved deformation size and its support scheme for a soft rock tunnel excavation. The surrounding rock mass of the tunnel is simplified as an ideal elastic and plastic medium, in which some full-column rock bolts are fixed. Based on the principle of coordinated deformation, this paper establishes a mechanics model of the interaction between the rod body and surrounding rock mass. In addition, the distribution law of surface friction and the axial force of an anchor bolt are analyzed, and the neutral point position where the relative displacement between the bolt body and the rock mass is zero, and the maximum axial force of the bolt body according to the static equilibrium condition of the bolt body, are derived. Plastic zone and loose zone formulas, along with the influencing factors of surrounding rock with a support structure, are discussed. A displacement formula and a rigid-gap-flexible formwork supporting technology of the surrounding rock are also proposed, based upon which, the displacement and reserved excavation deformation size of surrounding rock are calculated; in addition, the surrounding rock is supported using a flexible formwork. The results show that the deformation range of tunnel-surrounding rock can be analyzed inversely according to the axial force of the anchor body. Moreover, the flexible formwork support structure can absorb a great deal of deformation energy of a largely deformed soft rock, the appropriate stiffness of which can resist the harmful deformation of the surrounding rock, and new research approach is put forward for a reasonable design of the excavation and support scheme of a soft rock tunnel.
  • Haze Defogging Algorithm for Traffic Images Based on Improved Gradient Similarity Kernel
    WANG Gui-ping, SONG Jing, DU Jing-jing, HUANG He, WANG Hui-feng
    China Journal of Highway and Transport. 2018, 31(6): 264-271,280.
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    In fog and haze weather, the degraded images collected by traffic image acquisition equipment contain more noise and the edge of the image is not prominent. Images are dark and the contrast is low, and the images are pale and gray. For traditional traffic image filtering and image defogging algorithms, the filtering effect and edge preserving ability cannot be taken into account, which is prone to cause noise patches, resulting in low image quality after defogging. Based on traditional gradient bilateral filtering, a new gradient similarity kernel is designed, and a haze defogging algorithm for traffic images based on the improved gradient similarity kernel is proposed. Firstly, collected images containing noise are transformed into the Lab color space to enhance the color gamut width. Next, by using the improved similarity kernel and the space similarity, the weights of gradient similarity and spatial similarity are calculated, which are between each pixel of the image and the neighboring pixels in the filter box, respectively. The images are filtered according to the weights, and the filtered images are transformed into the RGB color space. Finally, according to the atmospheric scattering model and the dark channel prior principle, the filtered traffic images are subjected to defogging processing, and restored images can be obtained. The experimental results show that compared with the traditional bilateral filter and gradient bilateral filter, after processing with the proposed algorithm, the peak signal-to-noise ratio and normalized gray difference of the restored image are improved by 13.25% and 9.41%, and 21.76% and 22.7%, respectively. While ensuring the filtering effect and avoiding the "noise patch", as many of the edge details of the image as possible can be retained. This can improve the quality of fog traffic images, and has important application value and practical significance for enhancing traffic monitoring and ensuring traffic safety.
  • Analysis of the Driving Behavior During the Takeover of Automatic Driving Vehicles in Dangerous Traffic Situations（in English）
    NIU Jian-wei, ZHANG Xue-mei, SUN Yi-pin, QIN Hua
    China Journal of Highway and Transport. 2018, 31(6): 272-280.
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    To guide drivers to use the automated driving system safely, this study investigated their performance during the takeover from automated driving to manual driving on a driving simulation platform. This study also investigated the factors influencing the switch mode between automated driving and manual driving in complex traffic environments. Driving behavior was analyzed in terms of driving speed, headway distance, vehicle lateral control, and vehicle steering behavior, and the associated data were collected from 36 subjects, who participated in two dangerous traffic situations. The results show that some subjects immediately switch the driving mode after the road situation prompt appears, while other participants undertake surveillance of the information pertaining to the road and vehicle after the prompt, and therefore, do not switch to manual driving until a traffic conflict is observed. It is found that the state (e.g., playing games or listening to music) of the subject before taking over the vehicle has an influence on the takeover time. The time to take over the vehicle in the case of the participants that were playing games is shorter than that of the participants listening to music. It is found that the switch mode has a significant influence on the lateral position of the vehicle as well, and the subjects that chose the first switch mode can keep driving at a relatively safe speed during the subsequent driving process, indicating that there is a correlation between "switching mode one" and "lower safe vehicle speed", though the causal relationship between the two needs further investigation.
  • Traffic Target Tracking Algorithm Based on Scale Adaptive Multiple Instance Learning with Compressive Sensing
    YANG Hong-hong, QU Shi-ru
    China Journal of Highway and Transport. 2018, 31(6): 281-290,316.
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    This paper aims to solve the problem that most existing tracking algorithms have poor adaptability in the process of tracking a traffic target with scale and pose changes and use a fixed-size tracking box to track the target, which results in the target template containing a lot of background information and causing tracking drift or failure. In this paper, a traffic target tracking algorithm based on scale adaptive multiple instance learning with compressive sensing theory and a superpixel objectness measure is proposed. Firstly, compressive sensing theory is used to reduce the feature dimension in multiple instance learning, thus reducing the computational complexity of the algorithm. Secondly, local scale adaptive adjustment is carried out by using the superpixel objectness measure to solve the scale adaptation problem in the multiple instance tracking algorithm. In addition, a target identification mechanism with variable learning rate is introduced to update the classifier parameters, and the occlusion or drift of the tracked target is judged by the similarity of the target in the continuous frame. According to the result of target identification, the classifier parameters are updated with the variable learning rate. The experimental results show that the proposed tracking algorithm has good robustness and high tracking accuracy under complex environments with vehicle occlusion, scale change, and three-dimensional rotation. Compared with CT, MIL, and WMIL trackers for the test traffic video sequences, the average center position error in test videos is far smaller, at only 3.92 pixels; the error in CT, MIL, and WMIL is 56.96 pixels, 35.36 pixels, and 58.54 pixels, respectively. The average overlap rate of the proposed method is 80.1%, while that of CT, MIL, and WMIL is 44.9%, 45.3%, and 45%, respectively, which meets the real application of intelligent traffic monitoring.
  • Characteristics of Urban Cyclist Perception of Fatigue（in English）
    LI Cong-ying, YANG Yun-feng, SHAO Zhuang-zhuang, HUANG Yi-zhe, ZHU Tong, XUE Jia-liang
    China Journal of Highway and Transport. 2018, 31(6): 291-298.
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    To explore the mechanism of perceiving cyclist fatigue and seek the factors that influence the perception, this study designed and implemented a cycling experiment in different cycling environments. Based on the cycling data, including individual attributes, the intensity of cycling activity, and the physiological and psychological data of cyclists, collected from the cycling experiment, a fatigue perception model was developed using multivariable linear regression. The model described quantitatively the relations between cyclists' perceiving fatigue state and their individual attributes, cycling activity intensity, and physiological and psychological loads. The linear significance and multicollinearity of the model were tested by using a statistics method. In addition, through implementation of another cycling experiment, the forecasting ability of the cyclist fatigue perception model in real cycling activities was verified. The analytical results show that perceiving cyclist fatigue is mainly influenced by the individual attributes of cyclists, the intensity of their cycling activities, and their physiological and psychological loads. Statistically, the influencing impact factor scores of the aforementioned on fatigue perception were -0.291, 0.353, 0.253, and 0.265, respectively. This means that a positive correlation was found between fatigue perception and cycling activity intensity, the cyclists' physiological and psychological loads, and their perception of fatigue, whereas the cyclists' individual attributes had a negative correlation with fatigue perception. It should be noted that cycling activity intensity had the greatest effect on changes to the cyclists' perception of fatigue. No significant difference was observed between the forecast and real values of the cyclist fatigue perception model. Based on these research results, this cycling system can be improved by reducing the physiological and psychological loads of cyclists during cycling, thereby reducing the expectation of the cyclists' perception of fatigue during cycling and affecting their decision-making and cycling behaviors. This model also can be used in the field of bicycle evaluation and planning.
  • Subjective Perception Based Passenger Congestion Quantification for Bus Operation
    TENG Jing, WANG He-fei, YANG Xin-zheng, LIU Hao-de, LIU Xiang-long
    China Journal of Highway and Transport. 2018, 31(6): 299-307.
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    To comprehensively quantify crowding and passenger transport efficiency of the equipment and facilities of a bus corridor, and scientifically evaluate the sensitivity of objective technical index and subjective passenger perception to the level of the bus running condition, the conception of passenger congestion and passenger congestion index models was proposed. From the analysis of the correlation between subjective passenger travel time and passenger congestion and the characteristics of bus travel, the passenger congestion quantification model was formulated with a time multiplier for systematically evaluating subjective perception, travel time, and crowding. A visual analogy scoring SP survey was designed for model parameter estimation data collection, incorporating four characteristic variables (passenger density in carriage, passenger density on platform, travel time, and waiting time) affecting perception time. Applying the practical data of a Beijing Xisanhuan bus corridor, the all-day temporal-spatial distribution of section passenger congestion index and the dynamic evolutionary trend of the corridor passenger congestion index were studied. According to the results, based on the peak-state threshold (the value of which is 0.193 9), the passenger congestion condition of the Xisanhuan bus corridor presents significantly directional distinction, and the peak-state is more remarkable and lasts longer in the downward direction. Furthermore, the average sensitivity coefficients of the four characteristic variables are 0.449 2, 0.165 2, 1.427 1, and 0.408 3, respectively, and travel time is the most significant factor of the passenger congestion index while passenger density on platform is the least, showing that the model is capable of distinguishing causes of formation. This model has the advantage of comprehensively analyzing the temporal-spatial distribution and dynamic evolutionary trend of passenger congestion in a bus corridor, and may hopefully be applied to bus running condition improvement measures research.
  • P2 Structure Hybrid Power System Coordinated Control
    GUO Wei, XU Xiang-yang, LIU Xian-dong, WANG Shu-han, DONG Peng
    China Journal of Highway and Transport. 2018, 31(6): 308-316.
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    To improve the control efficiency and responsiveness of hybrid systems, a P2 control structure and effective hybrid mode are proposed based on the characteristics of the P2 hybrid control system's complex control object and the vehicle function requirement. The entire mode conversion truth matrix is proposed based on the vehicle's driving cycle and mode conversion efficiency. To meet the coordinated control requirements, a P2 hybrid coordinated control structure is presented, where the main functions and interface definitions of each control unit were constrained. With consideration given to the response delay of the two different power sources in the coupling process by the hydraulic hybrid clutch and control overlap between the hybrid clutch and shift clutch, the clutch control and engine start control sequences were optimized. The relationship between the engine torque, motor torque, and hybrid clutch control pressure, was established by defining the key control objective in different control stages. The results show that the mode conversion can be realized efficiently by HCU according to coordinate among engine, motor, and transmission. Each system control result is verified by vehicle test. The whole mode conversion time is 1.5 s, and the gear shift quality and dynamic responsiveness also meet the driving requirements.
  • Load Equivalent Method for Fatigue Bench Test of Hydraulic Excavator Stick
    XIANG Qing-yi, LU Peng-min, WANG Bin-hua, REN Xue-jiao
    China Journal of Highway and Transport. 2018, 31(6): 317-326.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A load equivalent method is proposed to overcome the problem of the correlation characteristics between forces not being reproduced when each hinge force is compiled separately into the load spectrum and applied to the fatigue bench test. In other words, the load equivalent method is proposed to obtain the basic data that reflect the actual working situations of the stick and can be used to compile the programmed load spectrum for a bench fatigue test. Three-dimensional pin-shaft force sensors, pressure sensors, displacement sensors, and strain gauges, were used to measure the time history of the stick's hinge force connected to the bucket, cylinder force, rocker force, working posture, and stress of the critical fatigue measuring points on the stick. The loading scheme of the fatigue bench test in the local coordinate system of the stick was determined according to the change of each hinge force and the stick's movement characteristics. On the basis of the stick cross section's stress state, it is proposed that maintaining the consistency of stress at the maximum stress point of the stick's maximum bending moment cross-section should be used as the load equivalent benchmark. Then, each hinge force on the stick would be equivalent to a unidirectional force. The calculated stress history caused by the equivalent load at each critical fatigue measuring point on the stick was compared with the measured stress history of the corresponding measuring point. The results revealed that the correlation degree of the two stress curves reached 97.21% at point 1 and 91.54% at point 2, while it was slightly lower at point 3, where it reached 88.6%. At the same time, at each critical fatigue measuring point, the calculated fatigue damage caused by the equivalent load was very close to the measured fatigue damage caused by the measured stress, which verified the load equivalent method. Moreover, the load obtained by the equivalent method comprised the basic data for compiling the load spectrum for fatigue life prediction and the programmed load spectrum for the fatigue bench test.
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