交通运输工程学报

Determination method of optimum asphalt content in asphalt mixture under considering homogeneity

GUO Nai-sheng, YOU Zhan-ping, TAN Yi-qiu, ZHAO Ying-hua, WANG Cong

Abstract: In order to determine the optimum asphalt content of asphalt mixture, the inner structure characteristics of components of asphalt mixture were identified by using CT technique.The densities and areas of coarse aggregate, asphalt mastics, and air voids were regarded as characteristic parameters, the homogeneity evaluation index of asphalt mixture was proposed, and the homogeneity evaluation method of asphalt mixture was built.The relationship between the characteristics of inner structure components and the volumetric design parameters in Marshall design method for asphalt mixture was analyzed, the homogeneity of inner structure of asphalt mixture was taken into account, a determination method of optimum asphalt content ofasphalt mixture was established, and three types of asphalt mixtures (AC-13, AC-16, and AC-20) were chosen to verify the method.Analysis result shows that there exists a favorable relationship between the homogeneity evaluation index and the volume of air voids for asphalt mixture, and the volume of air voids with respect to the minimum homogeneity evaluation index is corresponding to the optimal homogeneity of inner structure of asphalt mixture specimen.The difference average value between the volumes of air voids obtained by the homogeneity evaluation method and the values measured by the laboratory density test is 0.28%, the average differences between the voids in mineral aggregate and the voids filled with asphalt computed according to the volumes and the values obtained by Marshall design method are 0.27% and 1.33%respectively, therefore, the volumetric characteristic parameters of components of asphalt mixture considering the homogeneity of inner structure can represent the volumetric design parameters in Marshall design method.The differences of optimum asphalt contents of asphalt mixtures (AC-13, AC-16, and AC-20) determined by Marshall design method and the proposed method are 0.07%, 0.03%, and 0.05% respectively, which means that the proposed method is effective to determinate the optimum asphalt content of asphalt mixture.More>

2017, 17(1): 1-10.

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Compaction characteristic and operability factor of warm bituminous mixture

YAN Xi-li, CHEN Si-lai, AN Shu-wen, LI Ang, ZHANG Qing

Abstract: To study the compaction characteristics and compaction operability of warm bituminous mixture, AC-13 C mixtures were made based on 3types of warm mix bitumens with the same brand (ACMP1, ACMP2 and ACMP3) and 2kinds of hot mix bitumens (70 ^# base bitumen and SBS modified bitumen).The compactness and stability of each Marshall specimen were measured by Marshall compaction test, their change rules were analyzed in different initial compaction temperatures and times, and the exponential regression relationship between compactness and compaction times was proposed.The curvature factor on compaction growing was applied and the operability factor was defined to evaluate the compaction workability.Test result shows that the compactness of bituminous mixture increases exponentially with the increase of compaction times, increases faster in the early stage, slows in the late stage, and stabilizes finally.The compactness increases linearly with the increase of initial compaction temperature within 90 ℃-150 ℃.Marshall stability increases linearly with the increase of compactness in accordance with traditional research results.The operability factor of warm bituminous mixture decreases by13.5%-18.5% compared with hot bituminous mixture, so it is easier to be compacted.More>

2017, 17(1): 11-19.

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Applicability of IRI based evaluation of airport pavement roughness

LING Jian-ming, LIU Shi-fu, YUAN Jie, YANG Wen-chen

Abstract: A comprehensive analysis method of the applicability of international roughness index (IRI) based airport pavement roughness evaluation was proposed, the quarter car model and the aircraft kinetic model were built, the IRI and the vertical acceleration of center of gravity of aircraft (VACGA) were respectively proposed as the evaluation index of airport pavement roughness, and the solving models of IRI and VACGA were built by using MATLAB/Simulink.The microwave fluctuation of airport pavement profile was simulated by using the sinusoidal rough excitation, the distribution characteristics of the IRI and the VACGA under different amplitudes, wavelengths and taxi speeds were detailedly analyzed.Calculation result shows that the IRI and the VACGA are proportional to the amplitude.The sensitive wave band of IRI is shorter, its wavelength is 1-5m, and the IRI reaches the maximum value at 2m wavelength.At the taxi speed of 200km·h^-1, the VACGA has three wave crests with the change of wavelength, and it reaches the maximum crest at the 15 m wavelength.When the taxi speed of aircraft is lessthan 40km·h^-1 in taxiway, the sensitive wave bands of VACGA is 2.3-7.2m, almost distributes in the sensitive wave band of the IRI, which means that IRI can be used to evaluate the taxiway roughness.However, when the taxi speed of aircraft is more than 60km·h^-1 in runway, the sensitive wave band of the VACGA is 6.4-23.6 m, not in the sensitive wave band of the IRI, which indicates that it is unreasonable to evaluate the airport pavement roughness using the IRI when the taxi speed of aircraft is higher in runway.More>

2017, 17(1): 20-27.

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Crack propagation rule of semi-rigid base of airport pavement based on BOTDA

GAO Jun-qi, GENG Ren-shan, SHENG Yu-xiang, AN Ping, JIN Pei-pei

Abstract: By the laboratory and field cement-stabilized macadam base crack monitoring tests, the relationship between sensing fiber strain and crack width, crack propagation rule in early stage of semi-rigid base, and crack growth rate were researched based on the distributed BOTDA fiber monitoring technology.Research result shows that when the crack widths are 3, 6and 9mm, the strains measured by the sensing fiber encapsulated with polyurethane are 5.9×10^-3, 7.7×10^-3, and 10.3×10^-3, respectively, the strains measured by the sensing fiber encapsulated with metal matrix are 1.5×10^-3, 1.6×10^-3, and 2.1×10^-3, respectively, and the fiber strain rises with the increase of crack width.When the crack width is 9mm, the strains measured by the sensingfibers encapsulated with polyurethane and metal matrix are 33.2and 6.8times as big as the average value measured by the interval fixed fiber armored with aluminum alloy respectively, so the sensing fibers encapsulated with polyurethane and metal matrix performs better for crack monitoring.In field experiment, in 13 dafter construction, 3 micro cracks were found at 80 m long road section, and the largest temperature difference is 2.1 #C during this period, which indicates that the cracks in the base generate and develope mainly in the first month and the dry shrinkage cracks are dominant.The dry shrinkage stress is the main influence factor of crack generation and crack spacing.In 20, 77 and 139dafter construction, the temperatures at the bottom surface of base layer are 10.3℃, 2.5℃and 9.4℃, respectively, and the corresponding strains measured at the bottom surface of base layer at crack location of K24+656are 4.2×10^-4, 9.5×10^-4 and 4.3×10^-4, respectively.No new cracks emerge in base layer in 139 d, which indicates that the influence of thermal shrinkage stress on early crack spacing is very less, and the thermal shrinkage stress mainly affects the crack width.The thermal shrinkage cracks basically appear at the position where the dry shrinkage stress displays peaks in the dry shrinkage phase.When the upper and lower base layers were constructed continuously, the positons of cracks of top surface and bottom are consistent. Hence, the transverse cracks in cement-stabilized macadam base are always penetrating cracks.Furthermore, the crack growth rate on the top surface is 3.8and 2.8times the values at the middle and bottom positons, respectively, so the crack growth rate on the top surface is biggest.More>

2017, 17(1): 28-35.

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Local buckling characteristics of stiffened rectangular plate on elastic foundation subjected to non-uniform loads

ZHANG Ning, LIU Yong-jian, LI Hui, Siegfried F STIEMER

Abstract: Based on the local stability of plate on elastic foundation, the energy method was adopted to deduce the nonlinear characteristic equation of local buckling for stiffened rectangular plate subjected to non-uniform loads.The effects of elastic foundation contact and longitudinal stiffening ribs were considered for plate's buckling analysis by using Galerkin method.The incremental iterative format of nonlinear characteristic equations of local buckling was given.The additional iterative equation of buckling characteristic value was proposed.Analysis result shows that the computational error of buckling coefficient is less than 2%compared with FEM, and the computational efficiency is higher because of avoiding the contact analysis process based on finite element simulation.When the load gradient is 1, the local stability of decentered component withstiffening ribs is greater because its buckling coefficient increases to 51.1that is 2.5times as large as the coefficient of the plate without stiffening ribs.The aspect ratio of buckling wave of stiffening plate is about 0.6, which shows relatively intensive arrangement.While the aspect ratio of buckling wave of non-stiffening plate is about 1.0.On the premise of unconverted sizes of stiffening rib, the optimal location of setting longitudinal stiffening rib is two fifths of plate's width distancing from the edge of plate's pressured side, and the critical buckling coefficient of stiffening plate increases to 78.9that is 4times as large as the value of non-stiffening plate.Because of the application of stiffening rib, the critical breadth-to-thickness ratio of rectangular concrete-filled steel tube increases to 172 that is 2times higher than the standard value.Obviously, when the longitudinal stiffening ribs are set on the wall of rectangular concrete-filled steel tube, the local stability of the wall effectively increases under the action of eccentric load, and the section sizes of rectangular concrete-filled steel tube are improved.More>

2017, 17(1): 36-44.

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Stress redistribution of RC beams strengthened with prestressed hybrid carbon/glass(C/G)fiber cloth

ZHANG Jian, YE Jian-shu, WANG Jing-quan, AI Jun, GAO Qi

Abstract: Based on solid degraded shell element, the layered shell element model was adopted for reinforced concrete (RC) beam and hybrid carbon/glass (C/G) fiber cloth, the combined shell element model was used for longitudinal reinforcement, and the prestress effect of hybrid C/G fiber cloth was simulated.A kind of nonlinear layered shell combined element for RC beam strengthened with prestressed hybrid C/G fiber cloth was established.The nonlinear effects of cracking, yielding and crushing of RC beam were described by cracking mode, Ottosen yielding criterion and Hinton crushing criterion.The changing rule of deflection, the reduction rule of stiffness and the ultimate bearing capacity of strengthened beam were analyzed, and the stress redistribution of hybrid C/G fiber cloth was studied.Calculation result shows that the nonlinearlayer shell combined element analysis method is reliable, the relative error between the calculated value of characteristic load of strengthened beam and its experimental value is not more than10%, and the nonlinear layered shell combined element has good convergence and numerical stability.Before the strengthened beam reaches cracking load, the stress redistribution coefficient of hybrid C/G fiber cloth changes little and is equal to 1.3at cracking load.Then it increases gradually, is equal to 4.1at yielding load and is equal to 14.8at ultimate loads.When the beam is strengthened with common hybrid C/G fiber cloth, the high-strength property of fiber cloth cannot be fully used, and the utility degree is about 83%.When the beam is strengthened with prestressed hybrid C/G fiber cloth, the structural system of beam be improved, the high-strength property of fiber cloth can be well used, and the utility degree exceeds to 90%.More>

2017, 17(1): 45-52.

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Analysis of vehicle design load standard of arch bridge

HU Da-lin, HUI Xiao-ji, XIA Chun-mei, LI Ying, ZHANG Hang

Abstract: The influence of current overload vehicles on bridge and the applicability of vehicle design load standard in General Specifications for Design of Highway Bridges and Culverts (JTG D60—2015) to the operating vehicle load on highway were analyzed.The weigh-in-motion (WIM) measured data of vehicle loads on Guangshen Expressway were studied.The Monte Carlo method was used to simulate the random load and random spacing of vehicle, the loading effect of random fleet was programmed, and the bending moment effects of clamped arch bridge sections at the midspan and arch foot were calculated.Based on the maximum value distribution principle, the characteristic values of loading effect in the design reference period were obtained, the standard model of recommended vehicle load based on the WIM measured data was presented, and the recommended load standard was compared with the design load standard in the current code (JTG D60—2015).Calculation result shows that the effect of recommended vehicle loadstandard is well applicative and inclusive to the measured values, the errors of bending moment at the midspan are less than 7%, the errors at the arch foot are 5%-11% when bridge spans are 25-65, 110 and 120 m, and the others are less than 5%.The ratios of generated bending moment effects resulting from the putative load standard based on the measured values of Guangshen Expressway and the highway I-grade lane load of current code on the clamped arch bridge are1.24-2.18, and the average ratio is 1.80, which indicates that the traffic of Guangshen Expressway is heavy, vehicle overloading is serious, and the load standard in the current code has great deviation with the deductive load standard according to the measured vehicle load of Guangshen Expressway, so the bridge design load standard of Guangshen Expressway should properly increase based on the existing standard.More>

2017, 17(1): 53-61.

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Dynamic stress calculation and fatigue whole life prediction of bogie frame for high-speed train

LU Yao-hui, XIANG Peng-lin, CENG Jing, CHEN Tian-li

Abstract: The rigid-flexible dynamics model of vehicle structure was established, the vibration responses of rigid and flexible bogie frames were compared, and the load spectrums of bogie frames were calculated.The transformation method of stress spectrum was analyzed, and the dynamic stress spectrums were computed by using the finite element method and the polynomial fitting method.On the basis of computed dynamic stress spectrums and related standard, the full fatigue life of bogie frame was calculated by using the linearly cumulative damage theory and the fatigue crack growth life's Paris equation.Computation result shows that when the natural frequency of bogie frame is 36.94-95.53 Hz, the amplitude of vibration acceleration response for bogie frame is greater with the vehicle system dynamics model considering flexible bogie frame than the multi-rigid-body vehicle system dynamics model, so the vibration modes of bogie frame have significant contribution on the vibration responses.When the load spectrums are convertedto the stress spectrums by using the polynomial fitting method and the transient analysis method, the maximum error of stress is 1.16 MPa, and the relative maximum error of stress is less than3% that meets the engineering analysis's calculation accuracy requirement of 5%.When the degree of reliability is 95%, the fatigue life of bogie frame is 1.82×10⁶ km based on the fatigue damage cumulative theory.When the crack at the dangerous concern of bogie frame grows from 1mm to 2mm, the propagation life is 1.76×10⁶ km that meets the fifth level maintenance period requirement of 1.2×10⁶ km in China high-speed train maintenance standard.Obviously, the calculation method of dynamic stress spectrum based on the dynamic modes of bogie frame and the prediction method of fatigue full life for bogie frame are reliable, which is meaningful for the dynamic design and the maintenance cycle making of bogie frame.More>

2017, 17(1): 62-70.

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Online identification method of time-varying parameters for longitudinal dynamics model of high-speed train

XIE Guo, ZHANG Dan, HEI Xin-hong, QIAN Fu-cai, CAO Yuan, CAI Bo-gen, GAO Qiao-sheng, WANG Yue-kuan

Abstract: In view of the longitudinal dynamics characteristic of high-speed train, the relationships between traction, braking force, resistance and velocity and acceleration were analyzed.The random disturbance caused by weather and route in high-speed train running condition was studied, the random effect on the structural parameters of train model caused by mechanical wearand running environment was analyzed, and a nonlinear parametric state space model was established to describe the longitudinal dynamics characteristic of high-speed train under the disturbances of noises.The conditional mathematical expectations of the model parameters were calculated by the expectation maximization (EM) algorithm, and the state of the train with particles parameters was estimated by combining the particle filter theory.The online identification method of time-varying parameters for the nonlinear dynamics model of high-speed train was set up based on the Bayesian posterior probability theory, and the real-time state of train was estimated.The parameters of Gaussian and Exponential distribution under Gaussian or Gamma noise were identified by Monte Carlo simulation.The simulation result shows that the relative errors of estimated and real speeds and displacements of high-speed train are less than 5%, and the relative errors of estimated parameters and real parameters of train model are less than 10%, which meets the actual requirement of train system.So, when the probability distributions of time-varying parameters are given, the states and model parameters of train can be identified and estimated under Gaussian or Gamma noise by the method.More>

2017, 17(1): 71-81.

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Pole shoe abrasion calculation method of electromagnetic track brake under emergency braking condition

CHEN Shi-an, YANG Xin, YAO Ming, WANG Sheng, Young-bae KIM

Abstract: To predict the service lives of pole shoes and ensure brake reliability, the pole shoe abrasion losses of electromagnetic track brakes (ETBs) during emergency brake of high-speed train were calculated through modeling and simulation of abrasion process, braking process and temperature field of brakes and rail.The Archard abrasion model considering speed and temperature and the dynamics model for emergency braking process of CRH2 train were built.Time-varying parameters including air braking force, electromagnetic braking force, brakingdeceleration, energy distribution coefficient of emergency braking, instantaneous speed and braking distance were calculated during the process of test ETBs'whole-process works.The heat transfer among ETBs, rail and atmosphere during emergency brake was analyzed, a 3D temperature field model of brakes and rail was established by using Fluent software.The heat flux of temperature field and the heat dissipation loading condition were obtained according to the time-varying parameters during braking process.The pole shoe abrasion losses of brakes were calculated during emergency braking process of CRH2 train with the running speed of 250km·h^-1.Calculation result shows that the temperature of rail top displays fluctuation changes according to the contact conditions between brakes and rail.The maximum temperature reaches 570.76 ℃in the spot with 1 620 mfrom brake start when the contact between rail and No.8ETB ends.When the active braking time is 24.5s, the maximum temperatures of pole shoes bottoms of those same-side eight ETBs in CRH2 train are 1 022.6℃, 1 037.7℃, 1 045.3, 1 052.8℃, 1 085.7℃, 1 100.9 ℃, 1 109.2 ℃, 1 124.4 ℃in order from front to rear, and the abrasion losses of ETBs pole shoes are 207.4, 208.7, 210.0, 210.7, 212.1, 213.4, 214.4, 215.5g.So, the heat accumulation of rail generates during working process of brakes, which will lead to the higher temperature and larger abrasion losses of latter ETBs'pole shoes in train running direction.More>

2017, 17(1): 82-92.

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Cruise speed optimization of tugboat based on real fuel consumption and emission

LOU Di-ming, BAO Song-jie, HU Zhi-yuan, TAN Pi-qiang

Abstract: The test of fuel consumption and emission of offshore tugboat in Shanghai Waigaoqiao Port was conducted by using portable emission measurement system, the relationship between fuel consumption, emission and cruise speed was fitted, an optimization model of cruise speed was established, and the optimal fuel consumption and emission of tugboat and corresponding speed were analyzed.Test result shows that CO₂ emission factor is related to fuel quality and working condition of ship, and the accurate emission result can be obtained by estimating based on empirical emission factor comparing with real-ship emission test.When power function is used to fit the relationship between the emissions of CO, CO₂, THC, NO_x, PM and PN, fuel consumption and cruise speed, the determination coefficient of each fitting curve is larger than0.9.Under the condition that fuel consumptionis optimized, when cruise speed is 7.21 kn, the total fuel consumption of tugboat in single cruise condition reaches the minimum and decreases by33.40% compared to the maximum cruise speed of 12.00 kn.The optimal cruise speed reachesthe maximum while both fuel consumption and NO_xemission are optimized.The optimal cruise speed reaches the minimum while both fuel consumption and all emissions are optimized.When cruise speed is 6.96 kn, the total fuel consumption and emission of NO_x, PM and PN reach the optimal values, compared to the maximum cruise speed, the total fuel consumption decreases by33.29%, and the emission reduction rates of CO, CO₂, THC, NO_x, PM, PN are 59.56%, 76.37%, 82.34%, 92.36%, 53.10%, 62.25% respectively. Obviously, the total fuel consumption and emissions of tugboat decrease significantly at optimal cruise speed.More>

2017, 17(1): 93-100.

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Analysis of road section state correlation and road distance in urban road network

WANG Dong-wei, LI Hui, LI Yan, YAN Ya-dan

Abstract: In order to optimize the urban road network layout, based on the traffic trip data of several cities from AMAP real-time traffic road condition, the correlations of road section states with different road grades, including major road, minor road and branch road, were studied.The distances between roads considering the correlations were set.Urban road network density and grade proportion were calculated.Analysis result shows that parallel distances of related units between major roads, between major road and minor road and between major road and branch road, all obey log-normal distribution.The 85 percentile values of parallel distances are 2.4, 1.0 and 0.9 km, respectively.The distance between major roads is set as 2.4-2.5 km.2 minor roads are set between major roads.The distance between minor road and major road is 0.8-1.2 km, and the distance between branch roads is 0.2 km or 0.3 km.The corresponding 85 percentile values of parallel distances for minor road and branch road are relatively close, which shows that the functional distinction of minor road and branch road in actual road network is not clear.The proposed road network structure layout meets the requirements of correlation, road network density and grade proportion.It can provide reference for road network planning.More>

2017, 17(1): 101-108.

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Complexity metric of waterborne traffic flow based on Lempel-Ziv algorithm and TOPSIS

ZHANG Ming-yang, ZHANG Di, GUO Huan, FU Shan-shan, HUANG Ya-min

Abstract: In order to quantitatively analyze and classify waterborne traffic flow complexity, a method of waterborne traffic flow complexity metric was proposed based on Lempel-Ziv algorithm and TOPSIS (technique for order preference by similarity to an ideal solution).Firstly, LempelZiv algorithm was used to obtain the complexity eigenvalues of measured time sequences ofwaterborne traffic flow and other compared sequences (periodic sequence, logistic sequence, Henon sequence and random sequence).Secondly, the close degree of each sequence was calculated by using TOPSIS.The class of complexity was divided by those close degrees of compared sequences.At last, the complexity degree of each sequence was represented by close degrees of time sequences of waterborne traffic flow and the complexity class.This complexity metric was carried out on the waterborne traffic flow of south channel of the Yangtze River.Calculation result shows that the correlation coefficient of complexity close degree of waterborne ship traffic flow is 0.698 1 with the number of ship traffic accidents, and 0.769 2 with the downside traffic flow of standard ships, respectively.The change trend is basically consistent, so the complexity close degree can reflect the complexity of waterborne ship traffic flow.The close degrees of periodic sequence and random sequence are 0.000 1 and 0.999 9, respectively.Meanwhile, the close degrees of logistic sequence and Henon sequence are 0.449 2 and 0.537 7, respectively.The close degrees of logistic sequence and Henon sequence are greater than periodic sequence and and less than random sequence.The close degrees of waterborne traffic flow from July to November in 2013 are 0.828 0, 0.852 7, 0.856 5, 0.823 7 and 0.810 7, respectively, the complexity of waterborne traffic flow is basically consistent.The values of waterborne traffic flow are far greater than those of periodic sequence, locate between the values of Henon sequence and random sequence, and are closer to the value of random sequence, which shows that the waterborne traffic system is neither periodic nor completely stochastic.The complexity class of time sequence of waterborne traffic flow is Level 1, showing high complexity.More>

2017, 17(1): 109-118.

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Optimization of end line network with door to door operation mode of highway passenger transport

YANG Zhong-zhen, WANG Wen-di, Theo NOTTEBOOM

Abstract: In order to solve the problem of operation dilemma for highway passenger transport in high-speed railway era, the door to door operation mode of highway passenger transport was proposed, and a bi-level programming model was built.The maximum total daily operating profit of highway passenger transport provider was taken as the object to optimize the end line network of highway passenger transport with the door to door mode in the upper model.The lower model calculated the passenger flow of transport network at equilibrium state.Case analysis was carried out based on real data from Dalian to Shenyang transport section.Calculation result shows that the total daily operating profit of highway passenger transport increases firstly and then decreases with the increase of end line number.Operating 4 lines and dispatching 25 coaches daily are best.The total daily operating profit of highway passenger transport provider with original operation mode after the opening of high-speed railway is 7 270 yuan with 99 yuan for ticket price and 130 person-time for average daily passenger flow.The total daily operating profit of highway passenger transport provider with door to door operation mode is 37 755 yuan with [88, 105]yuan for ticket price region and 778 person-time for average daily passenger flow.The door to door operation mode of highway passenger transport can effectively improve the market share and operating profit of highway passenger transport.With the profit of highway passenger transport provider guaranteed, this mode can significantly improve overall service level of passenger transport.More>

2017, 17(1): 119-128.

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Optimization of departure frequency for bus rapid transit with multi-type vehicles under time-dependent demand

DAI Cun-jie, LI Yin-zhen, MA Chang-xi, CHAI Huo

Abstract: Taking the single bus rapid transit line in public transport network as the research object, the departure interval characteristics of bus rapid transit vehicles and time-dependent characteristics of passenger travel demand along the line were analyzed.With consideration of various types of buses working collaboratively, the minimum cumulative waiting time of all passengers and the maximum average load rate of vehicles were taken as the objectives, the minimum, maximum departure time intervals and the ratio of supply to demand for vehicle transport capacity were taken as the constraints, and an optimization model of departure frequency under the collaboratively working mode of bus rapid transit with multi-type vehicles was constructed.An improved non-dominated sorting genetic algorithm was used to solve the model.The bus rapid transit data in Lanzhou City was used to carry out case analysis.Analysis result shows that when the cumulative waiting times of passengers reach to the maximum, intermediate and minimum values, the optimized departure times reduce by 22.9%, 16.7% and 8.4%, respectively, compared to the actual departure times, and the corresponding average load rates of vehicles increase by 27.4%, 15.1% and 3.9%, respectively.Compared to the single type of bus rapid transit vehicle working independently, the average departure time of two types of bus rapid transit vehicles working collaboratively increases by 7.9%, and the average cumulative waiting time of passengers reduces by 23.8%.According to the time-dependent characteristics of passenger travel demand, the optimization of departure frequency with the reasonable arrangement for various types of bus rapid transit vehicles working collaboratively can reduce the waiting time of passengers effectively and increase the utilization efficiency of buses.More>

2017, 17(1): 129-139.

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Emission factor measurement of vehicles based on MOVES

HUANG Wen-wei, QIANG Ming-ming, SUN Long-lin, ZHANG Xin

Abstract: The microscopic level of motor vehicle emissions simulator (MOVES) was used to numerically simulate the emission factors of typical vehicles.The portable emission measurement system (PEMS) was used to measure the end gas emission of test vehicles on actual roads.The simulated emission factor values from MOVES were verified by the measurement results.Analysis result shows that the ratios of the simulated emission factors of CO₂, CO, NO_x, HC and PM to the actual ones are 1.40, 0.72, 1.01, 1.05 and 1.05 for the large truck on the urban expressway, respectively.The ratios of the simulated emission factors of CO, NO_xand HC to the actual ones are 0.70, 1.07 and 1.07 for the large truck on the urban arterial road, respectively, and the ratios of the simulated emission factors of CO₂ and PM to the actual ones are 1.63 and 2.12, respectively.The ratio of the simulated emission factor of HC to the actual one is only 0.34 for the small passenger car on the urban expressway.The ratios of the simulated emission factors of CO₂, CO and NO_xto the actual ones are 1.22, 1.05 and 0.86, respectively, which are close to the measured values.The ratios of the simulated emission factors of CO₂ and NO_xto the actual ones are 1.20 and 1.10 for the small passenger car on the urban arterial road, respectively, which are close to the measured values.The ratios of the simulated emission factors of CO and HC to the actual ones are 2.25 and 0.53 for the small passenger car on the urban arterial road, respectively.The experiment result reflects the accuracy of MOVES in predicting vehicle emission factor to a certain extent, and indicates that the simulated vehicle emission factor using MOVES needs the corresponding parameter amendment in order to truly reflect the vehicle emission level.More>

2017, 17(1): 140-148.

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3D reconstruction of train accident scene based on monocular image

NIE Yin-yu, TANG Zhao, CHANG Jian, LIU Feng-jia, ZHANG Jian-jun

Abstract: To help with making an emergency rescue plan for train accidents, a rapid 3D reconstruction method of train accident scene based on a monocular image was proposed.Taking two camera projection models for different application scenarios into consideration, the SIFT algorithm was introduced to extract and match image feature with the CAD model of an accident train.Geometric constraints between vehicles were provided to transform the 3D reconstruction to solving a nonlinear least square problem with constraints, by which the position and pose of accident subjects were reduced at last.To quantitatively and qualitatively verify the calculation performance of the method, the mimicked train accident scene and the real train accident scene were respectively used to carry out 3D reconstruction.The precise finite camera projection model was applied in the mimicked train accident scene to carry out offline calibration, and the stable pin-hole model was adopted in the real train accident scene to carry out auto calibration.Analysisresult shows that through quantitative analysis of mimicked scene, the maximal and average relative error of 8 nodes for measurement in reconstructing two vehicles are 4.54% and 1.85% respectively.Through qualitative analysis of real scene, the 3D reduction of position and pose for vehicles can also be realized by combining the topographic information correction.The whole accident environmental panorama reduces visually with the help of 3D visualization engine.More>

2017, 17(1): 149-158.

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