交通运输工程学报

Calculation method of moisture warping stress for cement concrete pavement slab

ZHANG Xiao, ZHAO Hong-duo, ZHAO Dui-jia, SUN Li-jun

Abstract: In order to analyze the impact of moisture gradient on mechanical properties of cement concrete pavement, the calculation formulas of moisture warping stress for nonhomogeneous infinite pavement slabs subjected to free-rein constrain, axial deformation constraint, bending deformation constraint, bending-axial deformation constraint were derived by using the basic analysis method of elasticity mechanics.The formula of equivalent temperature gradient based on the moisture warping stress was derived by using the equivalent principle of moment.Based on continuously reinforced concrete pavement(CRCP), the stresses and crack widths of concrete slab and steel stresses were computed by using the finite element method based on cement stabilized base, stable aggregate base, asphalt concrete base, asphalt stabilized base, limestone soil base and natural soil base.Research result shows that the magnitude of moisture warping stress depends on the relative humidity distribution; the surface stress at slab middle increaseswith the increase of base stiffness, when the stiffness of base increases from 0.08MPa·mm^-1 to6.28 MPa·mm^-1, the surface stress increases from 4.1 MPa to 6.3 MPa; the type of base hardly has influence on the stress of steel; the horizontal displacement of crack end gradually increases from 0.0 mm to 2.9 mm from slab bottom to surface.More>

2016, 16(1): 1-7. doi: 10.19818/j.cnki.1671-1637.2016.01.001

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Noise characteristics of cement concrete pavement in tunnel based on on-board sound intensity method

LI Bo, ZHANG Zheng-wei, KANG Hong-wei, LI Liang-ying, WANG Feng

Abstract: The noises of expressway concrete pavements and asphalt pavements were tested by the on-board sound intensity(OBSI)method.The test samples were conducted by using statistics products and service solution software(SPSS).In tunnel, A-weighted sound levels and 1/3 octave bands of noise characteristics were studied for concrete pavements with different skidding resistance textures i.e.transverse grooves, longitudinal grooves, combined transverse-longitudinal grooves, and exposed aggregate cement concrete pavement(EACCP).The noise characteristics of asphaltconcrete(AC)pavement, stone matrix asphalt(SMA)pavement and ultra-thin friction course(Novachip)were estimated and compared with the noise characteristics of anti-slide pavements.Analysis result shows that A-weighted sound levels of concrete pavements with transverse grooves and combined grooves are 100-104 dB(A), the level of concrete pavement with longitudinal grooves is 99-102 dB(A), and the levels are 97-100 dB(A)for EACCP, AC pavement, SMA pavement and Novachip.The peak frequencies in 1/3 octave bands for all types of pavements are nearly 1 000 Hz.A-weighted sound level of the pavement with transverse grooves is larger 3-5 dB(A)than the levels of others pavements at the peak frequency.The result indicates that noise characteristics of concrete pavements in tunnel are induced by the pavement textures and can be improved by selecting reasonable pavement textures.More>

2016, 16(1): 8-15. doi: 10.19818/j.cnki.1671-1637.2016.01.002

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Shearing performances of corrugated steel webs encased with concrete

ZHANG Feng, LI Shu-cai, LI Hong-jiang, YAO Chen, YANG Sheng

Abstract: In order to study the shearing behavior of corrugated steel webs encased with concrete, the nonlinear-refined-numerical finite element model of corrugated steel webs encased with concrete was established, and its validity was verified by using the deflection and strain of test model.The shearing mechanism of corrugated steel webs encased with concrete was analyzed, the ratio of loads shared by concrete and corrugated steel webs was studied, and the shearing strength design formula of corrugated steel webs encased with concrete was presented and verified.Analysis result shows that the load capacities of numerical model and test model are 4 560 kN and4 744 kN respectively, the simulation error is 3.8%, so the finite element model is feasible.The steel webs'tension strut and the concrete's compression strut form X-type truss, and the shearing strength of corrugated steel webs encased with concrete is their sum.The shearing resistance of corrugated steel webs is basically linear relation with load.The shearing resistance of concrete encasement shows three polylines, it increases fast at the initial and late stage of loading, and scarcely changes at the middle stage of loading.The calculated result of presented formula ofshearing strength agrees with the model test result, the maximum ratio of shearing strength is1.1, so the formula is feasible and can be used to analyze for the shearing properties of corrugated steel webs encased with concrete.More>

2016, 16(1): 16-24. doi: 10.19818/j.cnki.1671-1637.2016.01.003

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Construction control of cantilever casting of long span reinforced concrete arch bridge

HU Da-lin, CHEN Ding-shi, ZHAO Xiao-you, GONG Jian-ping, LI Ying

Abstract: The structure characteristics of cable-stayed and anchored cantilever casting construction system for the main arch ring of arch bridge were analyzed.The methods to determine the forces of anchored cables in cantilever casting construction were summarized.The advantages, disadvantages, and applicabilities of the zero displacement method, the fixed length jacking cable method, the influence matrix method, and the zero moment method were analyzed.The design and construction schemes of Matihe Bridge being a reinforced concrete arch bridge with net-span of 180 m was taken as engineering background, and the main construction process of long span arch bridge built by using cable stayed cantilever casting method was analyzed.Thecable forces were calculated by using the zero moment method, the cable forces at the maximum cantilever construction stage were optimized by using the influence matrix method with the objective function of bending strain energy.Analysis result shows that the zero moment method is determined to be the most direct and effective control method for the cable-stayed and anchored cantilever casting construction of arch bridges.The stresses in the arch ring section change gradually from partially tensile state to completely compressive state, and both the alignment and stress of arch ring satisfy the design requirements in whole construction process.The tensile stresses of arch ring at the top and bottom sides do not exceed 1.5MPa, the compressive stresses are no more than 7.0 MPa, and the displacements of arch ring are no more than 10 mm.As the cable forces at the maximum cantilever construction stage are optimized, the alignment of arch ring can be adjusted, and its stress state is improved, thus the stress state of arch foot can be closed to "zero" state.The stability of arch ring at cantilever casting construction stage is closely related to the stayed and anchored cable system, and the internal forces, alignment, and stability during construction process are simultaneously dominated by a reasonable stayed and anchored cable system.The stress of arch ring is deeply influenced by the different removal procedures of stayed and anchored cable system, thus the removal process of stayed and anchored cable system should be optimized during construction process.The research results have been successfully applied to the design of the construction scheme and construction control of cantilever casting of the longest span reinforced concrete arch bridge in China, and can be taken as a reference for the design and construction control of other long span arch bridges, which has a practical significance in promoting the development and application of cantilever casting technology of long span reinforced concrete arch bridges. 2 tabs, 10 figs, 29 refs.More>

2016, 16(1): 25-36. doi: 10.19818/j.cnki.1671-1637.2016.01.004

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New numerical simulation method of shortwave track irregularity

LI Zai-wei, LEI Xiao-yan, GAO Liang

Abstract: Aiming at the shortwave track irregularity problem, a numerical simulation method based on scattered binary wavelet was proposed.The relationship between ISO 3095 standard spectrum and wavelet coefficients was obtained with ISO 3095 standard spectrum as objective function.The algorithm flow and steps of numerical simulation were designed.Numerical simulation result and field measurement result for a subway section in Shanghai were compared.Analysis result shows that suitable wavelet decomposition level is eight and the lowest level covers the wavelength range of 512-1 024 mm.Time domain waveform of numerical simulation for shortwave track irregularity accords with the statistical characteristics of actual shortwave track irregularity and shows instability, its amplitude value distributes in the range of-0.15-0.15 mm.The difference between numerical simulation result and ISO 3095 standard spectrum results from the difference between octave sampling interval and 1/3 octave sampling interval.Using the binary wavelet transform can effectively realize the numerical simulation for shortwave track irregularity.Simulation result and test result are slightly different in amplitude and detailed wavform.It is suggested to do a large number of measurements and statistical analysis forshortwave track irregularity.More>

2016, 16(1): 37-45. doi: 10.19818/j.cnki.1671-1637.2016.01.005

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Fast recognition method of rail region based on hue value mutation feature of image

MIN Yong-zhi, YIN Chao, DANG Jian-wu, CHENG Tian-dong

Abstract: The rail boundary points in track inspection image were extracted by detecting the hue value mutation features of different regions in the HSL color space of color images.The rail's edges were determined by the linear fitting of multiple rail boundary points of different bisectors, and then the target rail region was recognized.The distribution features of sleeper, ballast, fastener and rail and the hue value mutation features of different characteristic regions were analyzed in the captured sequence images of track inspection system using machine vision.The correspondences between the hue value mutation point and the rail boundary points of different bisectors under different numbers of equal parts were researched.The influences of different numbers of equal parts on recognition time and recognition failure rate were discussed.The recognition method was compared with the traditional method under different light conditions.Analysis result indicates that when the number of equal parts is 8, the optimal recognition effect is obtained, and the recognition failure rate is 5.0%, the recognition time is 4.65 ms.In thethree intervals of characteristic light intensity, such as 500-1 000, 1 000-10 000, and 10 000-100 000 lx, the average maximum recognition times of recognition method in the rail regions of tracks with wood sleepers and concrete sleepers are 4.57 ms and 4.48 ms respectively, and are 44.4% and 47.1% less than the values of traditional method respectively.The standard deviations of recognition times are 0.15 ms and 0.12 ms respectively, and are 91.8% and 93.6% lower than the values of traditional method respectively.The average biggest recognition failure rates of proposed method are 3.5% and 3.3% respectively, and are 66.0% and 76.9% less than the values of traditional method respectively.The standard deviations of recognition failure rate are 1.6%, and are 68.9% and 71.1% lower than the values of traditional method respectively.So the proposed method is an effective recognition method of target rail region in the track inspection system using machine vision.More>

2016, 16(1): 46-54. doi: 10.19818/j.cnki.1671-1637.2016.01.006

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Calculation of reasonable-longitudinal-continuous length for bed plate of CRTSⅢ slab ballastless track

CAI Xiao-pei, ZHAO Lei, GAO Liang, ZHONG Yang-long, LAU Albert

Abstract: According to the design scheme of CRTSⅢ slab ballastless track on subgrade, the nonlinear interaction between multilayer structures was considered, and the spatial coupled models of track structure with different longitudinal-continuous lengths of bed plate were established based on finite element method.The lateral stability of track structure and the stresses and deformations of slab, self-compacting concrete layer and bed plate under the temperature load were computed, and the reasonable-longitudinal-continuous length of bed plate was analyzed.Analysis result shows that the lateral stability of slab track is satisfied when the continuous length of bed plate is greater than or equal to the connected length of 2 track slabs.Under the condition of temperature increasing 45 ℃, when the length of bed plate increases, the changes of stress and moment in track slab are not obvious, while the longitudinal displacement linearly increases, and the maximum increasing value is about 58%.For the self-compacting concrete layer, the changes of stress and deformation are more obvious than the values of track slab, and the maximum value of tensile stress is 0.949 MPa.Under the condition of temperaturedecreasing 40 ℃, the influence of continuous length on the bed plate stress is obvious.When the continuous length of bed plate reaches the connected length of 5 track slabs, the longitudinal tensile stress of bed plate increases to 2.67 MPa, which is close to the allowable limit of concrete tensile strength.In summary, based on taking into the factors of lateral stability and structural strength, the reasonable-longitudinal-continuous length of bed plate should be the connected length of 2-5 track slabs.More>

2016, 16(1): 55-62. doi: 10.19818/j.cnki.1671-1637.2016.01.007

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Dynamic characteristics and parameter sensitivities of new cutting subgrade for high-speed railway in expansive soil area

YANG Guo-lin, QIU Ming-ming, YANG Xiao, FANG Yi-he

Abstract: The field vibration test of comprehensive experimental section for new cutting subgrade of Yun-Gui High-Speed Railway in expansive soil area was carried out, the 3Dtrack-subgradebase dynamics model was established by adopting the finite difference software FLAC3 D, and the dynamic responses of new cutting subgrade and the factors sensitivity of water-proof structure layer were studied. Analysis result shows that the water-proof layer can accelerate the attenuation of dynamic stress in subgrade, and reduce the dynamic displacement of subgrade surface.Increasing the thickness and elastic modulus of water-proof layer can reduce the dynamic displacement and the dynamic stress of subgrade beneath the water-proof layer, but will increase the dynamic stress of water-proof layer surface.When the position of water-proof layer lowers, the dynamic stress of subgrade surface increases, but the dynamic displacement of subgrade surface hardly changes.It is recommended that the thickness of water-proof layer is not less than 15 cm for the requirements of Code for Design of High Speed Railway(TB 10621—2009).The sensitive factors to the dynamic stress and displacement of subgrade surface and the dynamic stress of base surface are the laying position, elastic modulus and thickness of water-proof layerin the influence order from big to small.Considering the factors'effects on the dynamic responses of subgrade, it is the optimal solution that the laying thickness of water-proof layer is 20 cm, the elastic modulus is 1.0 GPa, and the laying position is the bottom of subgrade surface.More>

2016, 16(1): 63-72. doi: 10.19818/j.cnki.1671-1637.2016.01.008

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Weighted PID control of battery temperature for electric vehicle

QIN Da-tong, HUANG Jing-ying, LIU Yong-gang, HU Ming-hui

Abstract: A two degrees of freedom lumped parameter thermal model of lithium-ion battery for electric vehicle was developed.In order to obtain the real-time thermal responses of battery, the thermal model was combined with vehicle driving dynamics model.The parameters of thermal model were obtained by hybrid pulse power characterization test.The thermal responses of battery under different driving cycles were analyzed.A regenerative braking control strategy based on the weighted proportion integration differentiation(PID)method was proposed, the active control of charging current for battery was realized by adjusting the distribution coefficient of braking force for electromotor on the premise of meeting braking safety, so that the generating heat source of battery was controlled.The thermal responses of regenerative braking control strategy and traditional braking control strategy were analyzed under the typical driving cycles.Analysis result indicates that regenerative braking has definite impact to the temperature rise of battery, the greater the proportion of regenerative braking under the driving cycles is, the faster the temperature rise of battery is.The regenerative braking control strategy can effectively adjust the charging current amplitude of battery, the highest temperature of battery reduces by 2 ℃ than the traditional braking control strategy under the long downhill condition in American radical high-speed driving cycles, and the charging capacity of battery increases by 10%.Therefore, the regenerative braking control strategy can ensure the energy recovery and actively control the temperature rise of battery at the same time.More>

2016, 16(1): 73-79. doi: 10.19818/j.cnki.1671-1637.2016.01.009

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Performance comparison of backup brake system

ZHU Lu, WANG Xiao-dong, WU Meng-ling, TIAN Chun

Abstract: In order to compare the differences among three kinds of backup brake systems, the braking distance and coupler force were taken as evaluation indexes, and the simulation model of train brake system and the analysis model of performance parameters were built through the cosimulation of AMESim and Simulink.When the failure of direct electro-pneumatic brake system occurred, the characteristics of different backup brake systems were analyzed.Taking a full laden train with the speed of 120 km·h^-1 as an example, when the failure of direct electro-pneumatic brake system of a vehicle occurred, the changing trends of braking distance and coupler force were comparatively analyzed in four conditions including fault, single vehicle switching with hot standby backup brake, whole vehicles switching with hot standby backup brake, switching with cold standby backup brake, and the influences of fault vehicle's location on braking distance and coupler force were studied.Analysis result indicates that compared with the fault condition without backup brake system, the braking distance in the condition of single vehicle switchingwith hot standby backup brake decreases by 10.14% at most, the maximum tensile coupler force and the maximum pressed coupler force decrease by 84.59% and 76.87% at most respectively.In the condition of whole vehicles switching woth hot standby backup brake, the braking distance decreases by 6.41% at most, the maximum tensile coupler force and the maximum pressed coupler force decrease by 46.24% and 10.24% at most respectively.In the condition of switching with cold standby backup brake, the braking distance increases by 3.13% at least, the maximum tensile coupler force and the maximum pressed coupler force decrease by 48.73% and 25.58% at most respectively.With the retroposition of fault vehicle, the maximum tensile coupler force increases gradually, while the maximum pressed coupler force decreases gradually, and in the condition of single vehicle switching with hot standby backup brake, the maximum tensile coupler force and the maximum pressed coupler force both increase gradually.More>

2016, 16(1): 80-87. doi: 10.19818/j.cnki.1671-1637.2016.01.010

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Time integration algorithm in nonlinear railway vehicle system

YANG Chao, XIAO Shou-ne, ZHU Tao

Abstract: The nonlinear elements existing in railway vehicle system were studied, a corrected explicit method with double time steps was introduced, and the corresponding mathematical expressions were provided.Based on the simplified dynamics models of nonlinear railway vehicle system, five typical nonlinear examples of railway vehicle system were used to contrastively analyze the corrected explicit method with double time steps, Newmark method, Wilson-θmethod, Runge-Kutta method, Zhai method and the precise integration method, and the application scopes of the methods in nonlinear railway vehicle system were pointed out.Research result shows that Newmark method and Wilson-θmethod are not applicable for nonlinear railway vehicle system.Newmark method, Wilson-θ method and Runge-Kutta method can lead to spurious vibration in vehicle system including nonlinear vertical wheel-rail forces. When simulation time is 2 s and time steps are 0.4, 0.1, 0.01 ms respectively, the consumed times of corrected explicit method with double time steps are respectively 0.198, 0.829, 7.772 sthat are the shortest or the shorter in six algorithms.When the degree of freedom for nonlinear railway vehicle system is larger, the corrected explicit method with double time steps and Zhai method are recommended to use.More>

2016, 16(1): 88-94. doi: 10.19818/j.cnki.1671-1637.2016.01.011

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Influence of mechanical sealing surface shape of marine stern shaft on sealing performance

ZHOU Xu-hui, LIU Zheng-lin, MENG Xiang-kun, LIU Jiao

Abstract: In allusion to the unstable performance of marine stern shaft mechanical seal caused by the factors such as marine shaft axis bending, shaft misalignment, the wear of stern bearing, the force of propeller, etc., the influence laws of both spherical and planar sealing surface shapes on sealing performance were researched by using both empirical formula and ANSYS finite element method.When water depths are 200, 400, 600 m, the thermal-structural coupling models of both spherical and planar sealing surface were established respectively.The contact areas, the leakage rates, the seal criterias, and the friction powers of unit area were compared, and the influence laws of both spherical and planar sealing surface shapes on the key parameters such as deformation, contact pressure, and temperature, etc., were discussed.Analysis result shows that under the same water depth, the clearance region and the maximum clearance of spherical seal are less than the values of planar seal.Compared to planar seal, the contact pressure of spherical seal changes more smoothly, and the maximum contact pressure of spherical seal is only 40%-50% of the pressure of planar seal. With the increasing of water depth, the contactpressure, temperature, and deformation of the two kinds of sealing surfaces increase, the contact region of sealing surface decrease, the clearance region extends gradually.When water depth increases from 200 m to 600 m, the contact node number of spherical seal decreases from 10 to 6, and the number of planar seal decreases from 7 to 4.When water depth is 200 m, the maximum temperature of spherical sealing surface is 5.499℃ lower than the value of planar sealing surface.The contact area, leakage rate, seal criteria, and the friction power of unit area of spherical seal are all better than the parameters of planar seal, so the spherical seal can improve the mechanical sealing performance of marine stern shaft.More>

2016, 16(1): 95-102. doi: 10.19818/j.cnki.1671-1637.2016.01.012

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Optimzation of mixed air cargo transportation network

YANG Zhong-zhen, YU Shu-nan, CHEN Gang

Abstract: In order to optimize the air cargo transportation network with the mixed characteristics of point-to-point and hub-and-spoke, a bi-level optimization model was built based on the OD flow of air cargo transportation companies.The objective of upper model was designed to minimize the total transportation cost, and the air cargo transportation network structure and the configuration capacity were optimized.The equilibrium cargo flow on each link was calculated in the lower model.The bi-level optimization model was verified by using the related data of fourteen cities served by Shunfeng Airlines, under the premise of setting 4 hub airports, the cases with 4-6 cargo aircrafts were analyzed respectively.Analysis result indicates that in the three cases, four airports of Beijing, Shanghai, Nanjing and Shenzhen are all set as hub airports.When 4 cargoaircrafts are used, the cargo aircrafts are arranged on the flight segments of Beijing-Nanjing, Beijing-Shenzhen, Shanghai-Shenzhen and Nanjing-Shenzhen respectively.The transshipping ratios of 4 hub airports are 24.3%, 24.2%, 47.8% and 14.9% respectively, and the transshipping ratio of Nanjing Airport is the largest, while the ratio of Shenzhen Airport is the smallest.When 5 cargo aircrafts are used, the fifth cargo aircraft is arranged on the flight segment of Beijing-Shanghai, the flight segments of the other 4 cargo aircrafts remain unchanged.The transshipping ratios of 4 hub airports are 38.6%, 50.9%, 44.3% and 11.9% respectively, and the transshipping ratio of Shanghai Airport is the largest, while the ratio of Shenzhen Airport is the smallest.When 6 cargo aircrafts are used, all flight segments between hub airports are arranged with cargo aircrafts.The transshipping ratios of 4 hub airports are 38.5%, 74.0%, 79.5% and 10.2% respectively, and the transshipping ratio of Nanjing Airport is the largest, while the ratio of Shenzhen Airport is the smallest.Therefore Nanjing is a typical transshipping hub city, and Shenzhen is a typical hinterland hub city.The airports in the cities with large transport demand are determined to be hubs easily.Both hub airports and non-hub airports may transship cargos.Two nearby airports may be determined as hub airports simultaneously.More>

2016, 16(1): 103-114. doi: 10.19818/j.cnki.1671-1637.2016.01.013

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Optimization model of terminal container truck appointment based on coordinated service of inner and outer container trucks

CENG Qing-cheng, ZHANG Xiao-ju, ZHANG Qian

Abstract: Aiming at the congestion problem induced by terminal container trucks arriving together, an optimization model of terminal container truck appointment based on the coordinated service of inner and outer container trucks was proposed, the vacation queuing system was built, the solving method based on genetic algorithm was designed, and the numerical experiments were provided to illustrate the validity of the model and the method.Analysis result indicates that the calculated average waiting time of inner container trucks at yard is 14.31 min and the actual average waiting time of inner container trucks at yard is 15.11 min.The calculated average waiting time of outer container trucks at yard is 20.65 min and the actual average waiting time of outer container trucks at yard is 21.55 min.The difference between the calculated values and the actual values is small.After the appointment optimization, the average waiting time of outer container trucks at yard decreases from 20.65 min to 16.85 min and the average waiting cost of terminal container trucks decreases from 29.3 yuan to 24.1 yuan.The vacation queuing model can effectively describe the service process of inner and outer terminal container trucks.Obviously, the appointment optimization model of container trucks can decrease the waiting cost and time of terminal container truck.Managing container truck should give priority to decreasing the waiting time of inner container truck.More>

2016, 16(1): 115-122. doi: 10.19818/j.cnki.1671-1637.2016.01.014

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IHSDM freeway accident prediction models

MENG Xiang-hai, HOU Qin-zhong, SHI Yong-yi, JING Lin-peng, ZHENG Lai

Abstract: IHSDM(interactive highway safety design model)was used to predict accidents of 11 types of freeways, and the predicted accident numbers were compared with the actual accident numbers.The basic accident prediction models and the modification coefficients of alignment indexes were obtained, a set of IHSDM accident prediction improved models were built to carry out the sensitivity analysis of alignment indexes, the effects of alignment indexes on the predicted accident rates were explained, and the safe value ranges of alignment indexes for freeways were obtained.Analysis result shows that the accident numbers predicted by IHSDM are lower than the actual accident number, the least error is 13%, and the maximum error is 52%.The relative error between total accident number predicted by the improved model and the actual value is less than 10%.At specific road sections, Pearson's correlation coefficients are 0.60 at least, the root mean square errors are less than 0.30, and the mean relative errors are less than 30%.The sensitivities of accident rates to alignment indexes from high to low are straight line length, longitudinal slope, horizontal curve angle, horizontal curve radius and vertical curve radius.Obviously, compared with IHSDM, the improved model has higher accuracy and better applicability.More>

2016, 16(1): 123-132. doi: 10.19818/j.cnki.1671-1637.2016.01.015

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Regional traffic state evaluation method based on data visualization

HE Zhao-cheng, ZHOU Ya-qiang, YU Zhi

Abstract: The spatio-temporal accumulation index of traffic congestion was introduced to identify and quantitatively analyze regional traffic operation state.The functional relationship between congestion source and congestion evaluation point was built to construct visual model.The histogram of oriented gradient and the main component analysis method were used to carry out the characteristics extraction of traffic operation state data.Gaussian mixture clustering method was used to cluster characteristic data and devide the spatial distribution model of regional traffic congestion. 23 478 taxis in Guangzhou were chosen and 509 376 data samples were obtained.The congestion patterns of traffic road network were recognized and partitioned, and the distribution characteristics of urban traffic congestion were analyzed and evaluated.Test result shows that the average congestion intensities for three traffic samples are 0.558, 0.559 and 0.559 respectively, the traffic congestion aggregation indexes are 3.518, 3.121 and 2.800 respectively, so total road network congestion intensities for three samples are same, but there are big differences on spatial congestion distributions.When the congestion level is 6 in Guangzhou, the numbers of main aggregation regions for three congestion models are 2, 4 and 3 respectively, which accords with the practical survey result.The method proposed in this paper can depict the degree and distribution of regional traffic congestion, and describe the urban regional traffic operationalpatterns in spatial dimension more scientifically and directly.More>

2016, 16(1): 133-140. doi: 10.19818/j.cnki.1671-1637.2016.01.016

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Investigation of information quantity threshold on combined traffic signs

LIU Xiao-ming, WANG Yu, JIANG Ming, WEI Zhong-hua

Abstract: Aiming at lacking quantitative basis for information quantity threshold of combined traffic signs, combined signs containing guide sign and lane directional sign were designed.The subjects'visual cognition accuracy and reaction time of combined signs were measured.The information quantity threshold of combined signs was obtained and tests were carried out to verify simulation results.Analysis result shows that when lane numbers are 3-7, the subjects'visual cognition accuracies of combined signs are 94.17%, 93.13%, 93.50%, 87.50%, 86.07% respectively, and reaction times are 2 437.54, 2 514.01, 2 634.18, 3 600.75, 3 836.21 ms respectively.The visual cognition reaction time of information for one road name in guide sign is equal to that of five arrows in combined signs, both are 0.5 s.The information quantity threshold of combined signs is equal to information quantity for six road names when guide picture is simple, and the information quantity threshold of combined signs is equal to information quantity for five road names when guide picture is complex.If guide sign and lane directional sign are combined, the information of road name should be decreased correspondingly.More>

2016, 16(1): 141-148. doi: 10.19818/j.cnki.1671-1637.2016.01.017

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Comparison of relative navigation methods for large vessel formation

ZHOU Hong-jin, ZHONG Yun-hai, LI Wei

Abstract: A relative navigation model based on the pseudo-range double-difference of navigation satellite was built.Pseudo-range single difference based least square algorithm, pseudo-range double-difference based least square algorithm, pseudo-range single difference based EKF algorithm and pseudo-range double-difference based EKF algorithm were designed and were compared by tests.Analysis result shows that pseudo-range double-difference based relative navigation model can eliminate ionosphere, troposphere, multi-path, satellite clock error and receive clock error.EKF algorithm can significantly improve the resolution accuracy of relative navigation information compared with least square algorithm. Under EKF algorithm, the resolution accuracy of pseudo-range double-difference is 10% better than pseudo-range single difference.Under the minimum GDOP value principle, when the number of satellites increases, the distance resolution accuracy becomes better. When baseline length is 2 m, the distance resolution accuracy of pseudo-range double-difference based EKF algorithm can reach within 0.10 m, azimuth resolution accuracy can reach 4.0°, so the test accuracy and frequency in this paper can satisfy the relative navigation demand of keeping quasi dynamic for large vessel formation. 3 tabs, 27 figs, 20 refs.More>

2016, 16(1): 149-158. doi: 10.19818/j.cnki.1671-1637.2016.01.018

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