交通运输工程学报

Application of cohesive zone model to simulate reflective crack of asphalt pavement

ZHOU Zheng-feng, PU Zhuo-heng, LIU Chao

Abstract: Based on ABAQUS, the constitutive model and parameters of 3 Dcohesive element were analyzed by using the traction-separation law. By applying the displacement load on a cohesive element, the results of numerical simulation and theoretical computation of the stresses, displacements and strain energies were compared to verify the reliability of cohesive element under various combination rules of initial damage and complete failure in the loading process. In the asphalt surface course on the cracked base course, the cohesive elements were laid at the positions where reflective cracks might occur, the cohesive zone model was employed to simulatethe cracking procedure, and the effects of the parameters of cohesive element and the thickness of asphalt surface course on the crack propagation were studied. Analysis result shows that when the cohesive layer stiffness decreases from 40 to 20 GN · m^-3, the ratio of separation displacements of cohesive layer under unilateral and symmetric loads increases from 1.52 to 13.52, and the ratio of shear displacement to normal displacement of cohesive layer increases from 1.52 to 11.32 under unilateral load, which indicates that the asphalt surface course tends to appear type-Ⅱ shear cracks as the stiffness of potential cracking area decreases. Under traffic load, the cracking path of asphalt pavement is as follows: first, the damage begins at the bottom of asphalt surface course and propagates upwards; next, other damages occur near the loading area and propagate downwards; finally, after penetrating the entire surface course, the continuous decrease of potential fracture zone's stiffness will cause crack to propagate along the transverse direction of the pavement. In the increasing process of surface course thickness from 16 to 22 cm with a 2 cm-gradient, the separation displacement of cohesive layer decreases by 32.31%, 15.22% and 9.63%, respectively, and the ratio of shear displacement to normal displacement decreases from 3.24 to 1.10, which indicates that the increase of surface course thickness can effectively mitigate the propagation of reflective crack, although the effect decreases as the thickness increases. Furthermore, the increase of surface course thickness makes the reflective crack gradually transfer from type-Ⅱshear crack to type-Ⅰ-Ⅱmixed crack.More>

2018, 18(3): 1-10. doi: 10.19818/j.cnki.1671-1637.2018.03.001

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Built-in temperature's regional characteristics of cement concrete pavement and its effect on slab curling

WANG Li-juan, HU Chang-bin

Abstract: Based on the climate parameters of five Chinese regions, the distributional characteristics of built-in temperatures of cement concrete pavements in different regions with different altitudes and latitudes were studied by using the computational program of early-age temperature field of cement concrete pavement. The superposition effect of built-in temperature and ambient temperature was considered, the influence characteristics of built-in temperatures in different regions on the curling and uplifting of pavement were analyzed by using the 3 Dfinite element program. Research result shows that slab curling is affected by the built-in average temperature and built-in temperature difference between slab's top and bottom. Annual built-intemperature differences of cement concrete pavements in different regions present the bimodal distribution characteristics with low-wide and high-cuspidal peaks that respectively denote the distributions of negative and positive differences. Negative built-in temperature difference normally forms in the daytime, and has a large variability, which causes slab corner's upward curling. While positive built-in temperature difference basically forms in the nighttime, and has a numerical concentration, which causes slab corner's downward curling. The built-in temperatures of the pavements in different regions were compared, negative built-in temperature difference in the plateau area is the largest, and the high-frequency difference can reach-17.2℃in Lhasa. The second one is in the north area where the high-frequency difference can reach-13.2 ℃ in Harbin. Built-in average temperature is generally negative, and its distribution is the single-peak type. The annual range of air temperature in the high latitude region is larger, which directly results in the larger variation range of built-in average temperature. High-frequency built-in average temperature in Harbin is approximately-30.4℃, and approximately-18.4℃in Lhasa. Negative built-in average temperature also causes the downward curling of slab corner, and the effect of built-in average temperature on the curling is approximately 30%-50% effect of built-in temperature difference under the same condition. Different built-in temperatures combined with local climate have difference effects on the curling and uplifting of service pavement. When the negative built-in temperature difference of-20℃is added to local climate, the curling of slab increases by approximately 1.5-2.0 mm. It is suggested that pavement structure with quadrangular constraints is used in significant curling area to improve the engineering performance of the pavement.More>

2018, 18(3): 19-33. doi: 10.19818/j.cnki.1671-1637.2018.03.003

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Maximum grade and length of longitudinal slope adapted to dynamic performance of six-axis articulated vehicle

GUO Teng-feng, ZHANG Zhi-wei, LIU Bing, LIU Jian-bei, GAO Jin-sheng

Abstract: For the problem that under the same longitudinal grade, the dynamic performance of a representative (six-axis articulated) vehicle in highway freight transportation in China with full load was worse than the representative vehicle for the longitudinal slope design in Technical Standard of Highway Engineering (JTG B01—2014), the actual engine performance curves ofthis representative type of vehicle were obtained by combining the typical flat road test and the actual road test. The relationship between engine torque and engine rotate speed, as well as the relationship between engine power and engine rotate speed were analyzed. The relationship curves of slope grade-vehicle speed were established under different gears according to the motor vehicle motion equation. The maximum equilibrium vehicle speed under the condition of steady running, full engine load and different longitudinal grades were determined. The curves of acceleration and deceleration performance of this representative type of vehicle were gained to propose the primary longitudinal slope design indicators such as the grade and length of the longitudinal slope, which conform to the change of freight vehicle type in China. Research result shows that under the same longitudinal grade, owing to the reduction in the specific power of the representative vehicle, its equilibrium speed decreases by 20%-30% compared to the representative vehicle for the longitudinal slope design in Technical Standard of Highway Engineering (JTG B01—2014). The maximum longitudinal grade adapted to the six-axis articulated vehicle is 50% lower than that specified in the standard. Therefore, the dynamic performance of the current representative vehicle cannot adapt to highway longitudinal slope design indicators. According to the acceleration and deceleration characteristics of the six-axis articulated vehicle under different longitudinal grades, the maximum slope length satisfied the climbing demand of six-axis articulated vehicle decreases with the increase of longitudinal grade, the reduction increases gradually, and the largest reduction reaches 60%.More>

2018, 18(3): 34-43. doi: 10.19818/j.cnki.1671-1637.2018.03.004

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Freezing and thawing characteristics of seasonal frozen soil along Moscow-Kazan High-Speed Railway

HAN Long-wu, CAI Han-cheng, CHENG Jia, ZHAO Xiang-qing, JIANG Kai

Abstract: According to the geomorphologic unit, micro-geomorphology, stratigraphic lithology and hydrogeological conditions and other factors, 14 monitoring sites were established in seasonal frozen soil areas along the Moscow-Kazan High-Speed Railway, which is 770 km long. FromOctober 1, 2016 to April 26, 2017, the lithology, density and moisture content of seasonal frozen soil, groundwater level, earth temperature, air temperature near the ground surface, snow thickness, and snow density were continuously measured once every 10 days. Based on the measuring data, the freezing and thawing characteristics of seasonal frozen soil along the railway were studied. Research result shows that in the seasonal frozen soil region along the MoscowKazan High-Speed Railway, snow cover lasts from late October to following April. Snow cover thickness varies from 20.2 to 38.2 cm and the average value is 27.3 cm. The maximum snow cover thickness varies from 25 to 60 cm, occurs in early to middle February, and the average value is 44.4 cm. The soil starts to freeze from middle November to late November, and thaws completely from early March to following middle April. The unfrozen time lasts from 100 to 165 days, and the average time is 122 days. The freezing rate of the soil changes from 0.27 to 1.20 cm·d^-1, and the average value is 0.50 cm·d^-1. The thawing rate changes from 0.27 to 2.52 cm·d^-1, and the average value is 1.14 cm·d^-1. In the freezing period of the soil, snow cover reduces the freezing rate of the soil. In thawing period of the soil, snow cover delays the thawing beginning time of the soil from the top to the bottom, also reduces the thawing thickness of the soil from the top to the bottom, and changes the double-direction thawing between the top and the bottom into the single-direction thawing from the bottom to the top. Along the Moscow-Kazan HighSpeed Railway, the maximum average freezing depth of the soil is 0.45 m within the range of 0.19-0.90 munder natural conditions, which generally occurs in early or middle February. Snow cover can reduce the seasonal freezing depth of the soil, and the reduction is 22.2%-32.6% when the thickness of snow cover is 26.1-28.6 cm. Snow cover has both cooling and insulating effect on the soil in the periods of early snow formation and late snow melting, but the cooling effect is major. However, in the stable period of snow cover, the insulating effect is major. Snow cover has a substantial insulating effect on the soil temperature, and the influencing depth and extent depend on the moisture content of the soil. The higher the moisture content is, the less the influencing depth and extent are, and vice versa.More>

2018, 18(3): 44-55. doi: 10.19818/j.cnki.1671-1637.2018.03.005

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Track irregularity probabilistic model

XU Lei, ZHAI Wan-ming

Abstract: To efficiently select track irregularity random samples for satisfying the ergodicity requirements of excitation sources in stochastic dynamics and reliability analysis in vehicle-track system, the weak-stationarity and similarity spectral of track irregularities were introduced to propose a track irregularity probabilistic model. Using the discrete probability integration and statistical approaches, the massively measured track irregularity time histories were divided into multiple time-domain sequences. The statistical power spectral density distribution of each sequence was calculated by the spectral analysis method. Then, using the matrix-based method, the set representation of the power spectral density function of track irregularities was obtained. It was assumed that the power spectral densities could be linearly accumulated at different frequencies, allowing the probabilities of entire spectra line to be obtained using the power spectral density probability distribution of a single frequency. The representative track irregularity spectra were selected through the commonly random simulation methods, and the track random irregularities were inversely simulated. The height and direction track irregularities of high-speed railway about 269 km were measured. Based on the vehicle-track coupled dynamics theory, the calculation results between the track irregularity probabilistic model and track irregularity stochastic model was compared from the aspects of the simulated amplitude of track irregularity and the probability density distribution for dynamic response in the vehicle-track system to verify the validity and high efficacy of the track irregularity probabilistic model. Calculation result shows that when taking the track random irregularities caused by the two models as excitation sources, the difference of the obtained probability entropies of vehicle-track system dynamic response between the two models is less than 2%. Both models can accurately express the excitation characteristics of track irregularities. The stochastic and probabilistic models need 131 and 33 random samples, respectively, to guarantee the consistent probability density distributions between the simulation and measurement, and the probabilistic model has higher computation efficiency. Under the presented computational condition, the wheel-rail forces and car body accelerations are 38-152 kN and-0.042 g-0.043 g, respectively, and are respectively less than the limits of wheel-rail forces (170 kN) and car body accelerations (0.25 g) in Code for High Speed Railway Design (TB 10621—2014). The track irregularity status of the investigated high-speed line is sufficient to guarantee the running safety and riding comfort of the vehicle.More>

2018, 18(3): 56-63. doi: 10.19818/j.cnki.1671-1637.2018.03.006

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Test and analysis on frost heaven effects of cold region tunnel

ZHANG Yu-wei, LAI Jin-xing, QIU Jun-ling, XIE Yong-li

Abstract: To investigate the distribution law of frost heaven force with time and space, the test frost heaven force was defined based on the temperature field. The change law of the frost heaven force was described by the lining pressure and steel arch stress. A new test method of frost heaven force was presented based on the temperature field, and a temperature field-frost heaven force synchronization test system was developed. Took Jichoushan Tunnel of Sichuan Provincial Highway 215 as an example, 5 test sections were set to conduct large-scale field tests, and the typical sections of K117+700 (section 700 for short) and K117+600 (section 600 for short) were selected to investigate the tunnel environment temperature, surrounding rock temperature, secondary lining pressure and steel arch stress. The differences in the stresses of the secondary lining and steel arch between the conditions of freezing (from December to February of next year) and unfreezing (from July to September) were defined as the test frost heaven force, and the testfrost heaven force was analyzed through the temperature field. Subsequently, the theoretical frost heaven force was computed by the existing frost heaven model and compared with the field test result, and the frost heaven law of the tunnel in the cold region was studied. Analysis result shows that the tunnel environment temperature changes with time as a seasonal sine functional variation. The surrounding rock temperature affected by the environment temperature changes as a seasonal positive and negative temperature variation, and a seasonal freezing-thawing phenomenon appears. Under the negative temperature, the surrounding rock is frozen, and the supporting system is affected by the pressure of the surrounding rock and frost heaven force. The lower the temperature, the more obvious is the effect of the frost heaven. The peak value of stress of each section appears in January. The maximum stresses of lining and steel arch of section 700 are 149 kPa and 31 MPa, respectively. Under a positive temperature, the surrounding rock is unfrozen, and the supporting system is only affected by the pressure of the surrounding rock. The maximum difference of frost heaven forces among different test points on the same section can reach 5.23 MPa. It is illustrated that the frost heaven force is not only related to the temperature field, but also to the rich water condition and surrounding rock grade. The test frost heaven force is 1.25 MPa less than the calculated one. Therefore, a frost heaven force reduction coefficient of 89.17% should be considered when designing the supporting.12 figs, 36 refs.More>

2018, 18(3): 64-73. doi: 10.19818/j.cnki.1671-1637.2018.03.007

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Calulation of vertical earth pressure of high-fill steel corrugated pipe culvert

WEI Rui, CAO Zhou-yang, GU An-quan, XIE Yong-li

Abstract: A method involving the inertia moment calculation for characterizing the wave characteristics of steel corrugated pipe was introduced. Through the Spangler pipe-soil interaction model, a computational formula of the vertical convergent deformation of steel corrugated pipe culvert was obtained. The top fill of the pipe culvert was deemed to be a semi-infinite straight line deformation body, and the settlement of the strip foundation was inverted to assimilate the stress model of buried pipe culvert. Based on the foundation settlement calculation formula derived from the elastic mechanics, the settlement difference between the compression deformation of the soil and the vertical convergent deformation of the pipe culvert was mainly considered and the calculating formula of the vertical earth pressure of the tube culvert was derived. Taking theproject of the high-fill steel corrugated pipe culvert at the Wujiahao to Zhangjiawan Section of the Guangba-Guangshan Highway as an example, the field test of vertical earth pressure on the top of steel corrugated pipe was performed. The vertical earth pressure computed by the formula was compared with the field test value and back-calculated result using the measured settlement difference value. Research result shows that the vertical earth pressure at the top of the culvert increases with the increase of filling height. The calculated values, measured values and inverse values of the vertical earth pressure at the top of the culvert after filling to design elevation are 224.14, 221.98 and 211.33 kPa, respectively, the relative error between the calculated value and the measured value is approximately 0.9%, and the inverse values are 6.1% and 5.0% less than the calculated and test values, respectively. The results of calculation and inverse calculation are consistent with the variation rule of the measured vertical earth pressure, and the higher the fill, the more consistent are the results. The proposed calculation formula of the vertical earth pressure of high-fill steel corrugated pipe culvert is feasible because it considers the resistance coefficient and the coefficient of the foundation bed, and reflects the deformation and stress characteristics of the steel corrugated pipe culvert.More>

2018, 18(3): 74-83. doi: 10.19818/j.cnki.1671-1637.2018.03.008

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New method of dust removal by negative ions in construction tunnel

XU Shi-qiang, REN Hong-yuan, WANG Ming-shan, LI Jie

Abstract: In order to dilute the dust during the ventilation for construction tunnels, so as to speed up the construction progress, a new method of dust removal using negative ions was introduced, and the feasibility of the new method was analyzed. Using the charge theory of dust particles, the charge of dust particles was studied, and the saturated charge formula of dust particles in the external electric field of a negative ion purification system was obtained. According to the environmental characteristics of construction tunnel, the dust particles' stress conditions were analyzed when the dust settling active forces were electric field force and gravity. The Newton's second law was used to deduce the settlement algorithm of dust particles. The indoor test was carried out through the simulation of a tunnel environment, and the field test was carried out after the tunnel test scheme was determined via the installation parameters obtained by the indoor test. The field test results were used to analyze the accaracy of the effect and mechanism of the negative ion dust removal method and settlement algorithm. Research result shows that duringaconstruction period, the respirable dust removal rates are 51% and 20%, respectively, with and without the negative ion purification system in the test section, and when the respirable dust concentration exceeds the permissible concentration-short term exposure limit of 8 mg·m^-3 in Technical Specification for Construction of Highway Tunnel (JTG F60—2009) (standardfor shot), the time durations are 1 and 12 h, respectively. The time-weighted average concentration of respirable dust reduces from 6.38 mg·m^-3 to 3.10 mg·m^-3 after using the system, which meets the standard's requirement of the time-weighted average concentration not exceeding 4 mg·m^-3. Therefore, the new method can quickly and efficiently purify the air during tunnel construction. The mechanism of the negative ion technology used for dust removal during tunnel construction can be explained by the charge theory of dust particles and Newton's second law. In a similar working condition where the main dust is PM₁₀, the dust removal times obtained by the dust settling algorithm, the indoor test and the field test are 14, 18 and 20 min, respectively. The dust settling time calculated by the dust settling algorithm should consider the comprehensive influence coefficient of 1.3-1.4.More>

2018, 18(3): 84-93. doi: 10.19818/j.cnki.1671-1637.2018.03.009

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Impact dynamic characteristic of heavy wagon and its effect on lateral load of bolster

SUN Shu-lei, WANG Guang-chao, PENG Yi-qiang, LI Ping-fei

Abstract: A 3D dynamics model of wagon impact was built based on draft gear dynamics theory, coupler bidirectional contact method and load transfer model of wagon and bolster, the impacts under different velocities and empty/heavy wagon states were simulated, the wagon impact dynamic characteristic and its effect on the lateral load of bolster were analyzed, and the simulation result was validated by impact test. Analysis result shows that the dynamic characteristic of draft gear-coupler bidirectional contact, and the lateral load of bolster in wagon impact can be simulated by using the 3D dynamics model, and are close to the test result. Themaximum errors of coupler force and bolster lateral load are less than 10% and 25%, respectively. Because the mass of empty wagon is smaller and the motions of coupler and plate change greater in wagon impact, the dynamic curve oscillation of coupler force in loaded and unloaded wagons impact is more obvious than that in loaded wagons impact, and even local peak appears. Relatively to the coupler contact model and mechanical transmission characteristics, because the model of draft gear has hysteresis characteristic, the coupler contact force in loaded wagons impact is 24% smaller than the resistance force of friction draft gear, and the value in loaded and unloaded wagons impact is 31%. The coupler force and bolster lateral load increase with the impact velocity, and the changing processes and appearing times of the maximum values are nearly consistent. The coupler force is larger between loaded wagons than between loaded and unloaded wagons under the same velocity. When the velocity is 3, 5 and 8 km·h^-1, respectively, the value increases by 57%, 25% and 37%, respectively. But the bolster lateral load is opposite to the coupler force, the value decreases by 42%, 53% and 47% under the three velocities, respectively. Therefore, the connected scheduling between loaded and unloaded wagons should be strictly controlled because their impact can result in larger lateral load of bolster.More>

2018, 18(3): 94-104. doi: 10.19818/j.cnki.1671-1637.2018.03.010

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Vibration control of EMU car body based on secondary vertical actuators and piezoelectric actuators

CAO Hui, ZHANG Wei-hua, MOU Bing-rong

Abstract: To reduce the rigid and elastic vibration of car body of high-speed electric multiple units (EMU), the active vibration control method was proposed based on secondary vertical actuators and car body piezoelectric actuators. Based on a certain type of high-speed EMU, an active reducing method of vibration was designed in which vertical actuators were installed in thesecondary suspension, piezoelectric actuators were arranged in the under-frame of the car body, and an H_∞ robust optimal controller was used to coordinate the vehicle control. A mechanics model of rigid-flexible coupled vibration reduction based on vehicle dynamics parameters was established. The placement positions of the piezoelectric actuators and sensors were optimized by using the H₂ and H_∞ norms. The H_∞ feedback controller was designed by robust optimal control method. The effect of vibration damper and active control method on vehicle dynamic performance was simulated by MATLAB. The dynamic performance differences between passive suspension vehicle, secondary vertical actuators vehicle and active control vehicle were compared. Analysis results show that when the piezoelectric actuators and the piezoelectric sensors are arranged at the distances of 7.15, 12.25, and 17.35 mfrom the left end of the car body, the normalized H₂ and H_∞ norms of the first and second-order elastic modes of the car body are the largest, and can be used as the placement positions of piezoelectric actuators and sensors. The robust optimal control method based on the secondary vertical actuators and car body piezoelectric actuators can effectively suppress vibration of the car body, and the acceleration power spectrums of the first order vertical bending vibration frequency on the car body centre and above the bogie reduce by 5% and 10% of passive suspension vehicle, respectively. With higher velocity, the vibration acceleration suppression effect is more obvious. When vehicle's speed is 200 and 350 km·h^-1, its mean square root of vibration acceleration decreases by 10% and 18%, respectively. Compared with the passive suspension, the magnitudes of output force power spectrums of the secondary vertical actuators are 106 N²·Hz^-1 at the bounce and pitch vibration frequencies of the car body. Thus, the secondary vertical actuators can greatly suppress the rigid vibration of the car body. The voltage power spectrums of the piezoelectric actuators reach a peak of 4 000 V²·Hz^-1 at the first order vertical bending vibration frequency of the car body, which greatly suppresses the elastic vibration of the car body.More>

2018, 18(3): 105-113. doi: 10.19818/j.cnki.1671-1637.2018.03.011

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Effect of subsystem parameters on vibration isolation characteristics of two-stage vibration isolation system

CHEN Jun, DING Jie, YAN Bing, WANG Yong-sheng, DONG Da-wei, HUA Chun-rong

Abstract: To determine the effect of subsystem parameters on the vibration isolation characteristics of a two-stage vibration isolation system (TSVIS), a three degrees-of-freedom (3-DOF) dynamics model of TSVIS with a subsystem was established. The analytical expressions for the amplitude ratio of the first-and second-stage main system and the subsystem were derived. The variation rules of these three amplitude ratios with the mass, natural frequency, and damping ratio of the subsystem were analyzed. The exact analytical and numerical solutions of the optimum parameters for the subsystem as an absorber on TSVIS were presented. The first batch of diesel railcar power packs in China were selected as the research objects, and the influences ofstiffness, damping, and mass of the radiator on the vibration isolation performance of the power pack TSVIS and the vibration intensities of the diesel generator set and radiator were investigated. The prototype of the power pack TSVIS with the optimum stiffness of the radiator isolator was obtained. A vibration test was carried out. Test result shows that a radiator vibration isolator stiffness greater than 1.5 times the turning point stiffness can seriously deteriorate the radiator's vibrations. A damping loss factor of approximately 0.24 can effectively restrain the vibration intensity and force transmission ratio peak of the TSVIS. A larger mass of the radiator can effectively improve the vibration isolation performance of the TSVIS and reduce the vibration intensities of both the diesel unit and the radiator. The maximum dynamic reaction force, under the stalling condition of the second-stage vibration isolator, reduces by 50%. The maximum measured dynamic reaction force of the second-stage vibration isolator under normal condition is 296 N, which is better than the current value. The maximum measured vibration intensities of the diesel unit and radiator under normal condition are 15.45 and 4.97 mm·s^-1, respectively, which represents an exceptionally satisfactory level. Therefore, by employing a larger mass and damping of the subsystem, and optimizing the TSVIS by regarding it as a vibration absorber, can improve the dynamic performances of the TSVIS under diesel engine starting, stalling and normal conditions.43 figs, 25 refs.More>

2018, 18(3): 114-128. doi: 10.19818/j.cnki.1671-1637.2018.03.012

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Axle temperature threshold prediction model of high-speed train for hot axle fault

XIE Guo, WANG Zhu-xin, HEI Xin-hong, GAO Qiao-sheng, WANG Yue-kuan

Abstract: Aiming at the problem that the adaptability of existing fault detection system based on the fixed temperature threshold for the axle was poor, and its high false and missing alarm rate, considering the influence of train speed, environment temperature and running conditions on the axle temperature and the relationship among the factors, a dynamic threshold prediction model for the axle temperature of high-speed train was established. Considering the difference in axle temperature variation of high-speed train under different running conditions, the train running state was divided into three stages: acceleration, steady running and deceleration, and aiming at each stage, the Pearson correlation coefficient method was used to analyze the correlation degree between the axle temperature and original monitoring data of train speed, environment temperature and load, as well as that between the axle temperature and derivative data of runningtime and initial axle temperature. The factors closely related to axle temperature variation were extracted, the multiple regression analysis method was used to establish a dynamic threshold prediction model for axle temperature based on the original monitoring data, and a modified dynamic threshold prediction model based on the original monitoring data and derived data for the three running stages of the train. The models were validated using the Ftest method. The model accuracy was verified based on the measured axle temperature data from high-speed trains in China. Research result shows that in the three stages of acceleration, steady running and deceleration, the average relative errors between the true values of axle temperature and the prediction values of the modified dynamic threshold prediction model are 2.0%, 4.1% and 3.3%, respectively. The prediction accuracies of the modified prediction model in the three stage increase by 79.8%, 64.3%, and 65.6%, respectively, compared to the dynamic threshold prediction model for axle temperature based on the original monitoring data. The decision coefficient of the model is larger than 0.99 and the significance probability is less than 0.05, which indicates that the model is effective.More>

2018, 18(3): 129-137. doi: 10.19818/j.cnki.1671-1637.2018.03.013

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Failure mechanisms discrimination and life prediction of safety relay

SUN Yong-kui, ZHANG Yu-zhuo, XU Chao-fan, CAO Yuan

Abstract: The failure mechanisms of a safety relay were analysed and divided into three failure modes. The contact resistance, closing time, super-path time, bounce time, releasing time and arc time were used as failure characteristic parameters, and the wavelet transform and moving average methods were utilized to achieve denoising. Aimed to the possibility of correlation among characteristic parameters, the principal component analysis method was used to achieve the dimension reduction for the multi-dimensional characteristic parameters to correlate the characteristic parameters. The average gradient value of principal components was defined. The failure modes of 18 sets of contacts were discriminated by using the Euclidean distance discrimination criterion. The characteristic parameters of contacts were analysed using the Fisher discrimination method. The characteristic parameter significantly reflected the features of a safetyrelay's life was selected as the prediction parameter. A grey prediction model was established to predict the safety relay's life, and the prediction effect of the model was verified. Research result indicates that after denoising, the characteristic parameters have good smoothness, high signalto-noise ratios, and low root mean square errors, indicating that a good denoising effect is achieved. The failure modes of 18 sets of contacts are discriminated with an accuracy of 83.3% using the Euclidean distance discrimination criterion. The super-path time has the largest Fisher discrimination function value of 8.2, indicating that the super-path time is an important parameter to represent the life of a safety relay. The actual lifetime of the safety relay is 122 000 times, the prediction life is 116 000 times based on the grey model, and the relative error of the prediction life is 4.9%, indicating that the proposed life prediction model has high accuracy and good feasibility.More>

2018, 18(3): 138-147. doi: 10.19818/j.cnki.1671-1637.2018.03.014

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Energy management strategy optimization of extended-range electric vehicle based on dynamic programming

XI Li-he, ZHANG Xin, GENG Cong, XUE Qi-cheng

Abstract: A modified dynamic programming algorithm was proposed.A future reachable states array was determined based on the constraints.The transfer costs among discretized states were calculated to guarantee the solving accuracy and reduce the off-line calculation burden.An energy management strategy for an extended-range electric vehicle was designed using a modified dynamic programming algorithm.Based on the energy management problem features, a dynamic system model was constructed, a system state equation for solving global optimization problems was determined, the battery state of charge (SOC) was selected as a state variable, and the extender output power was selected as a control variable.During the iterative calculation process, the cost of engine fuel and the battery energy were added in the objective function.Different driving-distance simulation cycles were constructed based on the Beijing arterial road cycle toobtain the optimal distribution result of required motor power.The control rules of extender start-stop corresponding to the battery SOC and required motor power were extracted, the distributed regulation between extender power split ratio and required power was fitted using the least square method, and the energy management strategy based on the optimal rules was established.Simulation result indicates that for the 100 km driving distance simulation cycle, the calculation time of the modified dynamic programming algorithm is 7 239 s, and the calculation efficiency improves by 78.2% compared to the classic dynamic programming algorithm.The optimal rule-based energy-management strategy has a similar control performance with the modified dynamic programming algorithm.The SOC errors of the two control strategies are within 2.5%.Compared to the charging deplete/charging sustain control strategy, the optimal rule-based control strategy improves the economy performance by approximately 5.4% and the fuel economy by approximately 7.9%.More>

2018, 18(3): 148-156. doi: 10.19818/j.cnki.1671-1637.2018.03.015

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Quantitative evaluation method of traffic function reliability for urban arterial roads

YAN Ya-dan, TONG Pei, NING Zuo-qiang, WANG Dong-wei

Abstract: A calculating model of traffic function reliability for urban arterial roads was established to quantitatively evaluate its achievement degree. The key features of traffic functions of arterial roads were analyzed, including the following three aspects: undertaking larger traffic volumes, having higher speed, and serving medium-long distance travel. The definition of traffic function reliability of urban arterial roads was proposed by the reliability theory. The travel speed and product of straight rates were selected as the corresponding indicators for the traffic function. The calculation method of traffic function reliability based on the probability theory was constructed. The threshold ranges of two calculation indicators were analyzed. The differencesand connections between the traffic function reliability and service level were compared. The traffic function reliability during the peak and off-peak hours was evaluated for two arterial road units in Zhengzhou. Calculation result shows that there is no correlation between the travel speed and product of straight rates, and they are further considered to be independent. The straight rates at the intersections between the arterial roads and branch roads are higher than those at the intersections between the arterial roads and sub-arterial roads. The four measured groups of straight rates are 0.271, 0.062, 0.229, and 0.034 higher, respectively. During the peak and offpeak hours, the traffic function reliability of Kexue Road, which connects the old district and high-tech development district, is 0.803 and 0.702, respectively. The achievement degree of traffic function on Kexue Road reaches a high level. The traffic function reliability of Dongfeng Road, which is located in the old district, is 0.386. The reliability characteristics and achievement degree of traffic function of Dongfeng Road are far lower than that of Kexue Road. The service levels of three intersections on Kexue Road are all level one. During the peak hours and off-peak hours, service levels of segments on Kexue Road are class B and C, respectively. The service levels during the peak hours of three intersections on Dongfeng Road are level two, level two, and level three, respectively, and the service level of segment on Dongfeng Road is class C. The service level of Kexue Road is better than that of Dongfeng Road in general. The evaluation results of traffic function reliability are basically consistent with the analysis results of service level. However, compared with the service level, the traffic function reliability for urban arterial roads can better reflect the function characteristics and effects of external factors on the urban roads traffic operation.More>

2018, 18(3): 157-166. doi: 10.19818/j.cnki.1671-1637.2018.03.016

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Merging influence factors recognition and behaviors prediction of on-ramp vehicles of urban expressway

WANG Er-gen, SUN Jian

Abstract: The vehicle trajectory data of bottleneck sections on US Highway 101 (US101) and Hongxu Road of Yan-an Expressway in Shanghai (SHHX) were analyzed, and the merging behaviors of on-ramp vehicles on urban expressway were studied.13 instant influence factors and 25 historical experienced influence factors of merging behaviors were considered. The random forests algorithm was used to sort the importances of 38 influence factors, and the key influence factors were identified. The merging behaviors prediction models based on the Bayesian network were established for two bottleneck sections, and the model prediction accuracy was evaluated. Analysis result shows that 14 key influence factors are obtained in the bottleneck sections US101 and SHHX, including 6 historical experienced influence factors. For the bottleneck sectionUS101, the historical experienced influence factors account for 45.45% of the whole key influence factors, while for SHHX, the proportion is 36.36%. Thus, the historical experienced influence factors have significant effect on the decision of final merging. The Bayesian network models that consider the historical experienced influence factors have higher prediction accuracy. The overall prediction accuracies of merging behaviors improve by 2.53% and 8.85% at US101 and SHHX, respectively. Without considering the historical experienced influence factors, the overall prediction accuracies of merging behaviors at US101 and SHHX are 87.94% and 73.17%, respectively. Under considering the historical experienced influence factors, the overall prediction accuracies of merging behaviors at US101 and SHHX are 90.47% and 82.02%, respectively. Additionally, the prediction models are not overly fitted. The difference between the prediction accuracies of merging and nonmerging events is within 1.2% using the testing datasets.More>

2018, 18(3): 180-188. doi: 10.19818/j.cnki.1671-1637.2018.03.018

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An ant colony optimization algorithm of stochastic user equilibrium traffic assignment problem

YANG Lin-jian, ZHAO Xiang-mo, HE Bing-hua, WEI Qiu-yue, AN Yi-sheng

Abstract: The relationship between the indicators of the traveler's familiarity with the road network and the equilibrium of traffic flow assignment was studied. An ant colony optimization algorithm with the pheromone update strategy of exponential form was proposed to solve the stochastic user equilibrium problem. In addition, the dynamic cycle process of traffic assignment was established from the logit model loading to the iterative calculations of traffic demand, path flow, road flow, road impedance and path impedance. The road flows and road impedances of Nguyen-Dupuis road network model were calculated and compared with the result computed by the successive average algorithm. The sensitivities of ant colony optimization algorithm and successive average algorithm were analyzed by adjusting the factors of the traveler's familiaritywith the road network. Analysis result shows that the road flow distributions computed by the successive average algorithm and ant colony optimization algorithm are 20-280 and 40-260 pcu, respectively, and the flow distribution interval computed by the latter decreases by 15.4%, while the maximum road flow decreases by 7.1%. Therefore, the road flow calculated by the ant colony optimization algorithm is more balanced. When using the ant colony optimization algorithm, the standard deviation of each road section flow in Nguyen-Dupuis road network model reduces from 65 to 48 pcu, 88% of the alternative paths' impedances distribute in 61-64, and 84% of the path impedances are lower than the result computed by the successive average algorithm. Therefore, the ant colony optimization algorithm can reduce the user travel time. When the familiarity of the road network is 0.01, 0.1, 1, 2, 7, and 11, respectively, the standard deviation of each road section calculated by the successive average algorithm is 75, 65, 50, 47, 45, and 45 pcu, respectively, and the standard deviation calculated by the ant colony optimization algorithm is 48, 48, 48, 47, 43, and 43 pcu, respectively. With the increase of road network familiarity, the range of the flow assigned to each road gradually decreases, and the standard deviation tends to be stable. The pheromone update strategy has greater influence on the probability of traveler's path selection, and the probability selecting the path with smaller impedance is higher. Therefore, the ant colony optimization algorithm gradually outperforms the successive average algorithm for the flow distribution of each road section.More>

2018, 18(3): 189-198. doi: 10.19818/j.cnki.1671-1637.2018.03.019

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Alternate evolution algorithm based on plant growth simulation for berth-quay crane joint allocation model

WU Di, WANG Nuo, LIN Wan-ni, WU Nuan

Abstract: To optimize the berth-quay crane joint allocation plans in a container terminal synthetically, the independence and system relevance between berth and quay crane were analysed. Based on the independence, two optimized sub-models were established, one to target the berth with the minimum average time in port, and the other to target the quay cranes with the minimum operating cost. Based on the system relevance, the constraint conditions for berth-quay crane joint allocation were constructed, the two sub-models were linked closely, and a complete berth-quay crane joint allocation model was established. The characteristics of the joint allocation model were analysed, and an alternate evolution algorithm based on plant growth simulation wasdesigned to solve it. Alternate evolution operators based on the plant growth simulation algorithm were used to alternately optimize the two targets of each individual in the population to achieve population evolution. The non-dominated solutions were screened through the algorithm framework. After multiple population evolutions and non-dominated solution screening, the Pareto satisfactory solution set for the berth-quay crane joint allocation was obtained. A berthquay crane joint allocation plan for 31 vessels arriving within 3 din the container terminal of Dalian Port was optimized and compared with the multi-objective genetic algorithm. Calculation result shows that 13 satisfactory solutions are obtained. The average vessel time in the port is 7.47-9.44 h, the number of quay cranes used is 85-96 and the total operating cost is 208 680-211 140 yuan. Compared with the optimization results of the multi-objective genetic algorithm, the computation speed is 6.07% faster, and four more non-dominated solutions are achieved with an increase rate of 30.76%, the results are closer to the Pareto frontier and the optimization degree of joint allocation plan is higher. The designed alternate evolution algorithm based on plant growth simulation maintains the maximized independence of an individual in the population evolution process and obtains more non-inferior solutions, and the alternate evolutionary approach provides results closer to the Pareto frontier.More>

2018, 18(3): 199-209. doi: 10.19818/j.cnki.1671-1637.2018.03.020

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Forecasting method of expressway traffic volume based on NPCA and GA-RBF

LEI Ding-you, MA Qiang, XU Xin-ping, LIU Qing-yi

Abstract: To improve expressway traffic volume forecasting accuracy, on the basis of the features of expressway traffic volume which was obviously nonlinear and affected by many factors, a forecasting method based on the nonlinear principal component analysis and GA-optimized RBF neural network (NPCA-GA-RBF) method was presented. The main influencing index of expressway traffic volume was determined, and the nonlinear principal component analysis method was used to reduce the dimensionality and correlation of influencing factors. The original multiple indexes were replaced by a few principal components to simplify the structure of the neural network. The GA was used to optimize the parameters of the RBF neural network and further improve the forecasting accuracy of traffic volume. An expressway in Puer City was taken as the example to verify the traffic volume forecasting method. Analysis result shows that theaverage relative errors of the GA-RBF and NPCA-GA-RBF methods in two experiments are 1.62%, 3.53% and 2.27%, 3.32% smaller than that of the RBF model, respectively, so the GA-optimized RBF neural network improves the traffic volume forecasting accuracy of the RBF method. Compared to the GA-RBF method, the average relative error of the NPCA-GA-RBF method decreases by 1.91% and 1.05% in two experiments, respectively, its traffic volume forecasting result is closer to the actual traffic volume and more reliable, which demonstrates that the nonlinear principal component analysis eliminates the correlation of the indexes to further improve the traffic volume forecasting accuracy and reduces the forecasting complexity of traffic volume. So, the NPCA-GA-RBF method has higher traffic volume forecasting accuracy, can provide the reliable decision basis for expressway operations management, and satisfies the objective requirements of the reasonable management for expressway.More>

2018, 18(3): 210-217. doi: 10.19818/j.cnki.1671-1637.2018.03.021

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Online compression algorithm of AIS trajectory data based on improved sliding window

GAO Miao, SHI Guo-you, LI Wei-feng

Abstract: The time series characteristics of ship AIS data and ship maneuvering characteristics were analyzed. An improved sliding window online compression algorithm was proposed. The AIS trajectory data from 277 ships with a total of 1 026 408 coordinate points were calculated, and the appropriate compression thresholds were determined. The sensitivities of distance and angle thresholds to the compression rate of the algorithm were analyzed. According to the step points of the compression rate image, three distance thresholds of high, middle, and low levels, and one angle threshold were recommended. The compression rate and efficiency of the DouglasPeucker algorithm and improved sliding window algorithm were compared. Experimental result shows that with the improvement of the compression rate, the remaining points after compression and the useful information retained by the data become less. The compression rate is positively proportional to the distance threshold and angle threshold. The dimensionless compression distance thresholds of high, middle, and low levels are 43%, 38% and 33% of ship length, respectively. When the distance threshold is 130 mand the angle threshold is more than 9°, the compression rate becomes stable, so the recommend angle threshold is 9°, which is similar to 8°that is the pressure difference angle in Design Code of General Layout for Sea Ports (JTS 165—2013). With an increase in the distance threshold, the compression rates of the Douglas-Peucker and improved sliding window algorithms tend to be similar. When the distance threshold is 120 m, the compression rate of the Douglas-Peucker algorithm is only 1.74% higher than that of the improved sliding window algorithm. In the case of five distance thresholds, the average operating time of the Douglas-Peucker algorithm is 5.39 times that of the improved sliding window algorithm. With the increase of data volume, the compression efficiency difference between the two algorithms is more obvious. The improved sliding window algorithm can reduce the risk of data compression, simultaneously showing a substantial improvement in the efficiency of data compression, and the data can keep compression states under the continuously updated condition. Compared to the ordinary compression mode, the improved sliding window algorithm occupies less system resources, has higher processing efficiency, and can be applied to ship trajectory data processing, ECDIS display, and extraction of key behavioural features of ships.More>

2018, 18(3): 218-227. doi: 10.19818/j.cnki.1671-1637.2018.03.022

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Corner feature extraction of 2D lidar data

KANG Jun-min, ZHAO Xiang-mo, YANG Di

Abstract: In order to enhance the robustness of the corner feature recognition in the driving environment by the unmanned vehicle and improve the recognition speed of the corner feature, based on the relative difference between bivariate normal probability density map values of observation points, a corner feature extraction method was proposed. The observation data set was mapped to the bivariate normal probability density space, and the mapping value of each observation point was obtained. The mapping results were normalized, and the numerical differences caused by the covariances were eliminated. The positions of peaks and troughs were found in the mapped numerical curve. The observation point corresponding to the peak was closest to the mean point, and the observation point corresponding to the trough was closest to the inflection point. Whether the set of observed data meets the edge length requirement of the corner features was determined by using the relative heights of peaks and troughs. Thecoordinates of the original observation data points corresponding to the troughs were used as corner features to construct the environment feature map. Test result shows that the extraction method can process sparse observation data with more than 63 observation points and angular resolution of the observation point greater than 1°. Therefore, in large-scale outdoor environment and indoor environment, the extraction method can stably identify large corner points. When the observation data points are less than 180, the maximum processing time is less than 5 ms, and the average processing time is less than 1.9 ms, so the extraction method has good real-time performance, which is conducive for decreasing the time required for designing the environment feature map. The extraction method extracts the corner features according to the bivariate normal probability density of the observation data, is insensitive to the observation error and the scale and shape of the corner feature, and can effectively improve the robustness of corner feature recognition.14 figs, 25 refs.More>

2018, 18(3): 228-238. doi: 10.19818/j.cnki.1671-1637.2018.03.023

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A dynamic evolution model of disequilibrium network traffic flow with quantity regulation of congestion

WU Li-xuan, HUANG Zhong-xiang, WANG Yu-lan, WEI Tao

Abstract: Supposing that the travel cost on the paths and the congestion degree on the key links were considered by the urban travelers, aprice-congestion mixed dynamic evolution model was established based on analyzing the equilibrium flow model.The model was based on the economics theory of non-Walrasian equilibrium method and by simulating the traveler's route choice behavior following the economical concept of market exploration process, the equivalency of model stability and equalization was verified.The evolution model was simulated by using a simple test network and a medium size network, the evolution process of disequilibrium network traffic flow and the performance of traffic network under the disequilibrium situation were described.Analysis result indicates that the evolution model of time price regulation accords with the classical Wardrop's first principle; the result of quantity regulation of congestion allows the degree of congestion on the key links of each path between OD to be the same; the result of pricecongestion mixed regulation allows the path flow to be adjusted between the paths of lower cost and the ones of less congestion, the undulation of dynamic evolution of which is greater than that of the single regulation.In the test network, because the model only considers the choice behavior of congestion degree upon path, the congestion degree of whole traffic network is more uniform, and compared with the single price regulation model, the overall uniformity coefficient improves by 62%.However, the mean link saturation improves from 0.60 to 0.64, which indicates that the traffic network becomes congested overall.By considering the joint regulation of these two factors, the saturation of most congested link decreases from 0.936 to 0.787.The overall uniformity coefficient improves by 46%.The mean saturation of links, path travel time and congestion decrease.The test result of the medium size network also shows that such mixed equilibrium model can describe the dynamic evolution process of traffic flow on traffic network flexibly and objectively, and achieve steady state flow of traffic network system, which canexplain the traffic travel behavior better.8 tabs, 9 figs, 32 refs.More>

2018, 18(3): 167-179. doi: 10.19818/j.cnki.1671-1637.2018.03.017

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