交通运输工程学报

Mechanical responses of Boeing 747 running on runways

WANG Xing-tao, CHEN Jian-feng, YE Guan-bao, YANG Dong, XUE Jian-feng

Abstract: Based on the large amounts of measured strains and deflections of runway pavement at Denver International Airport, the main characteristics of deflections and strains at different positions of pavement were analyzed when Boeing 747 was running on runway, and the load transfer capacities of different joints, the residual deformations and strain rates of pavement at the typical positions were researched. Analysis result shows that the edge and middle of slab have 2 strain peaks respectively, which corresponds with the number of aircraft's main gear axles. The transverse strain (perpendicular to the running direction of aircraft) only has one type, while the longitudinal strain (parallel to the running direction of aircraft) shows 2 times'transformation between tension and compression. The peak-strain recovery between gear axles at the bottom of longitudinal joint edge is significant, its peak strain and peak-strain recovery are 1.2 times and 2.5 times as much as the values at the top of longitudinal joint edge respectively, which means more prone to cracking and fatigue damage. When the aircraft is running, the maximum strainrates occur at the joint, and the maximum tensile and compressive strain rates are 9.1×10^-4 s^-1 and 7.6×10-4 s^-1 respectively, and belong to quasi-static strain rate, so their impact on the deformation of concrete slab are ignored. The deflection curves at the slab's middle have 1 peak, but there are 2 peaks at the slab's corner and transverse joint edge. The relative residual deformation at corner of slab is largest, the deformation at the middle of slab is least, the relative residual deformation rate at the corner of slab is 2.60-4.59 times as large as the value at the middle of slab, and compared with other locations, the corner more easily occurs void with base. The load-transferred coefficient of hinged joint is about 1, the load-transferred coefficient of dummy joint is lower compared with hinged joint, the load-transferred characteristic of dummy joint has directionality, but the load-transferred characteristic of hinged joint is non-directional.More>

2016, 16(2): 1-9. doi: 10.19818/j.cnki.1671-1637.2016.02.001

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Mechanical property of early-strength water-containing unsaturated polyurethane concrete

JIANG Kai, SU Qian, FENG Xu

Abstract: To solve the problem of poor workability, fast curing and molding difficulty of common polyurethane concrete, a new water-containing unsaturated polyurethane concrete was proposed according to the requirement of high standards for aggregate in common polymer concrete.The mechanical properties of water-containing unsaturated polyurethane concrete were investigated by ratio test, strength test, water-mixed test, immersion test and field sampling test, and the effects of material properties, material ratio, temperature and moisture content on the mechanical properties were analyzed.Analysis result shows when the added amount of water is 15%-20% of unsaturated polyurethane at 10 ℃-20 ℃, the added amount of water is 20%-30% of unsaturated polyurethane above 20 ℃, the compressive strength of 1d for the water-containing unsaturated polyurethane concrete is 22.70 MPa in field engineering application and immersion test, and the phenomena of softening and disintegration are not found after long-term immersion.Obviously, the water-containing unsaturated polyurethane concrete has good stability, workability and formability that meet the engineering needs in the construction.At 15 ℃, the recommended massratio of cement, sand, stone, ZK3, water, unsaturated polyurethane, initiator, and accelerant is1.000∶5.700∶7.300∶1.300∶0.080∶2.000∶0.050∶0.025.More>

2016, 16(2): 10-17. doi: 10.19818/j.cnki.1671-1637.2016.02.002

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Finite element simulation of inside-outside temperature gradient and thermal stress for abutment mass concrete

SUN Zeng-zhi, TIAN Jun-zhuang, SHI Qiang, LIU Wei, CHEN Hua-xin, XU Qin-wu, ZHANG Ben

Abstract: Aimed at the earlier temperature cracks of mass concrete during construction, a 3D finite element model of mass concrete was built based on the abutment of Laoshangou Highway Bridge in Inner Mongolia, and the effects of content of fly ash, pouring temperature, environmental temperature, and maintenance measure on central temperature, temperature difference between inside and outside, and surface tensile stress of abutment were analyzed.Simulation result shows that the surface tensile stress of concrete increases with the content decrease of fly ash, the decline increases when the content exceeds 30%, and the central temperature, the temperature difference between inside and outside, and the surface tensile stress decrease with the increasse of adding dosage of fly ash, so effective adding fly ash can reduce thehydration heat of concrete and prevent the occurrence of cracks due to the surface temperature difference.When the pouring temperature increases from 5 ℃ to 30 ℃, the highest central temperature of concrete increases from 40.3 ℃ to 58.1 ℃, the maximum temperature difference between inside and outside increases from 8.6 ℃ to 19.0 ℃, and the maximum tensile stress increases from 0.93 MPa to 1.66 MPa.The highest central temperature of concrete and the maximum temperature difference between inside and outside appear in advance, and the surface tensile stress increases linearly along with the increase of pouring temperature.The temperature difference between inside and outside and the surface tensile stress decrease with the increase of environmental temperature, and the relationship between the surface tensile stress and the environmental temperature is linear basically.The better curing condition is, the smaller the temperature difference between inside and outside is, the slower the increase speed of surface tensile stress is, the later the occurred time of maximum surface tensile stress is, which are beneficial to control the cracks.More>

2016, 16(2): 18-26. doi: 10.19818/j.cnki.1671-1637.2016.02.003

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Translation control model and optimization method of immersed tube under action of water flow

LI Jun-jun, YANG Xiao-jun, LI Yun, XIAO Ying-jie

Abstract: Aiming at the translation control of immersed tube under the action of water flow, the resultant force and resultant moment of tugboats were analyzed based on the mathematical description, the calculation equations of tug moment in four quadrants were unified, the translation control model of immersed tube was built, and the number of working tugboats, the surplus capacity of towing force and the floating speed were considered.A weighted logarithmic ideal point particle swarm optimization (WLIPPSO) method was designed.Cramer's rule was utilized to handle constraints for towing forces and angles of towing forces.The simulation was carried out through tube floating control example of immersed tube tunnel in island tunnel project of Hong Kong-Zhuhai-Macao Bridge.Simulation result shows that when the total number of tugboats is six, in rising tide the floating speed is 4.770 kn, the fitness is 0.720, the number of working tugboats is three, and the surplus capacity product of towing force is 2.693×10²⁰ kN⁶.In falling tide the floating speed is 1.750 kn, the fitness is 3.042, the number of working tugboats is five, and the surplus capacity product of towing force is 3.352×10¹⁹ kN⁶.So the model and method proposed have strong applicability, the fitness is better, the number of working tugboats is smaller, surplus capacity of towing force and floating speed are higher.More>

2016, 16(2): 27-36. doi: 10.19818/j.cnki.1671-1637.2016.02.004

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Improved fuzzy method of removing abnormal spike data from track's geometric irregularity of high-speed railway

LIU Jin-chao, LI Guo-qing, SUN Shan-chao, ZHAO Gang, GUO Jian-feng

Abstract: According to the mutation property of abnormal spike data for track's geometric irregularity of high-speed railway, an improved fuzzy method of removing abnormal spike data was designed.The point with unexpectedly increasing or decreasing forward difference was defined as the starting point of abnormal spike data, the following point being close to the starting point and with reversely changing forward difference was extracted as the end point of abnormal spike data, and the abnormal spike data were removed and replaced by the linear interpolation between the two endpoints of the minimum interval including the abnormal spike data.The membership functions were constructed by using the unit decomposition principle, and apre-judgment was proposed to avoid calculating the forward differences, the functions of firing degree of rules and the fuzzy basis functions when the track geometry data were normal.Calculation result shows that the improved method has the same accuracy as the previously used fuzzy filter method, but its computation time is less than 0.33% of the original one when the computation distance is longer than 500 km, so it is more easily achieved online.The errors between the analog signals and the measured track geometry irregularities are less than 10-3 when the improved method is used for detecting and removing the abnormal spike data.The improved method is able to not only accurately identify the locations of abnormal spike data andautomatically restore the signals, but also retain useful information such as the large alignments and gauges around the switches.More>

2016, 16(2): 37-45. doi: 10.19818/j.cnki.1671-1637.2016.02.005

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Effects of spallation on rail thermo-elasto-plasticity in wheel-rail sliding contact

LIU Yang, JIANG Shuo, WU Ya-ping, DUAN Zhi-dong, WANG Liang-bi

Abstract: A finite element model with rail spallations in wheel-rail sliding contact was established by using the finite element software ANSYS, the material nonlinearity was considered, the impact behaviors of wheel-rail contact were calculated when the wheels passed through the rail spallations, and the influences of length and depth of rail spalling area, friction coefficient and sliding speed on the thermo-elasto-plasticity of rail spalling area were analyzed by transient analysis.Analysis result shows when the length of spalling area is 2 cm and the depth is 4 mm, the equivalent plastic strain of rail reaches to the maximum, and the value in the rear of spalling area is 3-4 times as large as the value in the front.When the length of spalling area is 2 cm and the depth is 6 mm, the plastic deformation reaches to the maximum, and the value in the rear is about twice as large as the value in the front.The contact stress reduces with the increase of friction coefficient, while the frictional rising temperature, equivalent plastic strain, plastic deformation, equivalent stress and longitudinal shear stress of rail increase.When the friction coefficient is bigger than 0.3, the growth of equivalent stress and longitudinal shear stress becomes slower as the increase of fraction coefficient.When the sliding speed is equal to 3 m·s^-1, or is not less than 6 m·s^-1, the stress, deformation and temperature of rail are in most unfavorable conditions.More>

2016, 16(2): 46-55. doi: 10.19818/j.cnki.1671-1637.2016.02.006

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Friction and wear behavior of carbon strip/contact wire

HU Yan, DONG Bing-jie, HUANG Hai, CHEN Guang-xiong, WU Guang-ning, GAO Guo-qiang

Abstract: The friction and wear tests of pure carbon strip/Cu-Ag alloy contact wire were conducted on a ring-block type tester.When the electric current was 250 A and the relative sliding speed was 160-350 km·h^-1, the running condition of carbon strip/contact wire of pantograph-catenary systems for high-speed train was simulated by changing the speed of rotary table, and the influences of relative sliding speed on the friction coefficient, the current-carrying efficiency, the stability coefficient of contact pressure, the arc discharge energy, the wear rate of carbon strip, and the temperature rise of carbon strip were studied.The correlations between the six parameters and the sliding speed were studied.The wear morphologies of carbon strip were analyzed under different conditions.Analysis result shows that the friction coefficient, the current-carrying efficiency, and the stability coefficient of contact pressure decrease with the increase of relative sliding speed, while the wear rate of carbon strip, the arc discharge energy, and the temperature rise of carbon strip increase with the increase of relative sliding speed.There are strong correlations between the sliding speed and the six parameters.The positive correlations are found between the sliding speed and the stability coefficient of contact pressure, the arc discharge energy, the wear rate of carbon strip and the temperature rise of carbon strip, and the Pearson coefficients are 0.991, 0.996, 0.952, and 0.991, respectively.Meanwhile, the negative correlations are found between the sliding speed and the current-carrying efficiency and the friction coefficient, and the Pearson coefficients are -0.990 and -0.986, respectively.The wear of carbon strip increases with the increase of relative sliding speed, and there are lots of cracks on the surface of carbon strip when the relative sliding speed is faster than 250 km·h^-1, and the erosion area and the depth of crack are larger, obviously.The energy-dispersive spectrometry(EDS)analysis of worn surfaces of carbon strip shows that the transfer direction of material between the carbon strip and the contact wire is bidirectional.More>

2016, 16(2): 56-63. doi: 10.19818/j.cnki.1671-1637.2016.02.007

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Solving method of fatigue parameters of vehicle structures based on projection in spherical direction cosine group

YANG Bing, LIAO Zhen, MA Bai-quan, XIAO Shou-ne, YANG Guang-wu, ZHU Tao

Abstract: In the traditional projection method, the maximum principal stress was assumed to be the maximum tensile stress in advance, and the tension/compression properties of principal stress were not taken into account in the projection process.To improve the above inadequacies, a solving method of fatigue parameters based on the projection in spherical direction cosine group was proposed.A series of direction cosines around the points in structure were built, and the direction of the maximum tensile stress under multiple loading conditions was searched.In the process of calculating the maximum stress and the minimum stress, the directions of principal stress were retained, hence, the original tension/compression properties of stresses were preserved.The fatigue strength assessments of welded frame of three-axle bogie and the axle box body of vehicle were analyzed by using both the traditional projection method and the proposed solving method respectively.Analysis result indicates that for the welded frame, the maximumstress of node 254570 obtained by the proposed method is 19.4% higher than the value of the traditional projection method.The large differences of the minimum stresses deduced from two methods exist at 27.8%of nodes, the opposite results even exist in signs of the minimum stresses at several nodes.The revised equivalent stress amplitudes obtained by the traditional projection method are at least 1 MPa lower than the values obtained by the proposed method at 12% of nodes, and the values were even 34.73% lower at individual node.Therefore, the subsequent fatigue strength assessment based on such fatigue parameters is unsafe.For the axle box body, the symmetrical cyclic stress amplitudes obtained by the traditional projection method deviate from the actual situation.The values of some nodes are even 45.32% lower or 51.23% higher than the values calculated by the proposed method, which will lead to dangerous or overconservative results in fatigue analysis. The direction of the maximum tensile stress is determined, and the tension/compression properties of principal stresses are considered in the present method, therefore, the proposed method is more rational and credible in fatigue analysis compared with the traditional projection method.More>

2016, 16(2): 64-71. doi: 10.19818/j.cnki.1671-1637.2016.02.008

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Electrostatic monitoring of gearbox's lubricating oil system

LI Xin, ZUO Hong-fu, CAI Jing

Abstract: The lubricating oil electrostatic monitoring system that was built by a new type 3 499.5 kW gearbox test rig for the wear condition monitoring of gearbox in ground test, was used to complete the full flow abrasive particle electrostatic monitoring test for the lubricating oil systems of gearboxes.The original electrostatic signals were obtained from continuous loading test and accelerated life test.The root-mean-square values of time-domain signals were extracted as the characteristic parameters to represent the particle charging situation in the lubricating oil.The variation tendency of electrostatic signals were analyzed at two test stages respectively and compared with MetalSCAN online monitoring data and the offline result of oil sample spectrum analysis for validation.Analysis result shows that at the continuous loading test stage, the lubricating oil electrostatic signal fluctuates slightly with the change of rotational speed.At accelerated life test stage, the electrostatic signals of gearboxes synchronously change with the torque in a single cycle test.The abnormal wear of gearbox 2 is detected at the ultimate load test stage of the eighth cycle in accelerated life test, while gearbox 1operates normally, which is in accord with the results of MetalSCAN monitoring and the spectrum analysis.The fatigue crack of coupling diaphragm and the gear tooth root pitting of high-speed output shaft in gearbox 2arefound in disassemble gearbox fault detection.This proves electrostatic monitoring method is feasible and effective in wear condition monitoring of the gearbox and establishes the foundation for further implement of gearbox life prediction and installed online monitoring of the actual wind field.More>

2016, 16(2): 72-81. doi: 10.19818/j.cnki.1671-1637.2016.02.009

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Simulation of crane ship's ballast system based on well cluster theory

DONG Zhi-hui, HAN Duan-feng, LIN Xiao-jie, YUAN Li-hao, ZAN Ying-fei

Abstract: The virtual well cluster system and pipe network structure model of crane ship's ballast system were established, the calculation methods of node's water head and flow rate were analyzed, the calculation equation of pressure drop loss of pipe was researched, and the open degrees of valves and the special nodes such as pumps were considered.The flow rate-water head matrix equation of pipe network was built, and the water heads of nodes were calculated by using matrix partitioning and iteration methods.The pre-transferring routine of actual flow path was calculated in order to improve the calculation efficiency of matrix equation.The simulation system was built based on a crane ship's ballast system, and the man-computer interactive operation of pipe network was implemented, and the working status of system was monitored real-timely.In simulation experiment, the open degrees of valves were set as 1.0or 0.5in different cases respectively, the output flow rate of ballast pump was 3 500 m³·h^-1, and the flow was transferred into 6ballast tanks including 8P, 8S, 6P, 6S, 4P, 4S.Simulation result indicatesthat when the open degrees of all valves are set as 1.0, the flow rates of 6ballast tanks are603.73, 603.73, 605.88, 605.88, 540.39 and 540.39 m³·h^-1 respectively, and the flow rate is inversely proportional to the length of pipe network.When the open degrees of valves of 8Pand8 Sare both adjusted to 0.5, the flow rate of 6ballast tanks are 484.87, 484.87, 670.19, 670.19, 594.94 and 594.94 m³·h^-1 respectively.Obviously, the flow rate is sensitive to the open degrees of valves, and the open degrees has more impact on the flow rates of adjacent nodes, which has a high agreement degree to the actual system.The convergence rate of algorithm is high, and the calculation values of flow rate closely approach steady solution after circulation of 5times.More>

2016, 16(2): 82-89. doi: 10.19818/j.cnki.1671-1637.2016.02.010

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Bayesian network model for intelligent recognition of typical compartment fire

XIE Tian-hua, LIN Yan, YANG Zu-yao, JIN Liang-an

Abstract: Based on advanced fire sensors, the Bayesian network model of recognizing fire size and category intelligently was established, six fire characteristic parameters including upper temperature, lower temperature, CO concentration, CO₂ concentration, O₂concentration and light obscuration were considered as the input variables of the model, fire size and category were considered as the output variables of the model, and the relationship between input and output variables was deduced.Four kinds of fire sources including mattress fire, cable fire, pool fire and spill fire were simulated in living room, combat center, engine room and hangar respectively, 2 880 groups of simulated sample data were generated by using CFAST software, the parameters of the model were trained, and the trained recognition model was validated by using full-scale fireexperimental data.Validation result indicates that when the data of fire sensors are intact, the average recognition accuracy rates are 88.0%, 95.0% and 85.7% for small, medium and large fires respectively, and the average recognition accuracy rates are 90.2% and 81.5% for solid and oil fires respectively.When one sensor can't work because of serious damage or the hit of antiship weapon, the average recognition accuracy rates are 82.4% and 82.7% for fire's size and category, only 8.1% and 2.8% less than the rates with integrated fire sensors data respectively.So, the proposed model has good recognition ability and robustness, and can be integrated into ship damage control supervisory system(DCSS)to assist commanders in timely selecting the most effective firefighting methods and tactics.More>

2016, 16(2): 90-99. doi: 10.19818/j.cnki.1671-1637.2016.02.011

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Impact of adjusting airspace structure on arrival traffic flow in terminal area

ZHANG Hong-hai, LIAO Zhi-hua, ZHANG Qi-qian, ZHANG Xiang-yu

Abstract: The airspace network model in terminal area was built according to the airspace operation rules in terminal area by the network theory.Air traffic flow following model and holding model were built based on aircraft microcosmic behaviors.Simulation test was carried out based on NetLogo simulation platform.The impact of airspace structures with different in-degree distributions on traffic flow was analyzed.Simulation result shows that when the density is less than or equal to 0.075 flight per km and the velocity is more than or equal to 0.04 km·s^-1, the traffic flow is in free phase.When the density is 0.075-0.200 flight per km and the velocity is more than or equal to 0.04 km·s^-1, the traffic flow is in unblocked phase.When the density is more than 0.200 flight per km and less than the maximal density, the traffic flow is in congestion phase.With the decrease of flight wave function, the traffic flow enters inverse unblocked phase, then inverse free phase.Under the condition that the arrival traffic flow distribution is fixed, when the in-degree value is 2, 3, 1 successively, the velocity of traffic flow is small, the density is big, and the congestion dissipates slowest.When the in-degree value is 3, 2, 1 successively, the velocity of traffic flow is big, the density is small, and the congestion dissipates quickest.Itis known that increasing key node in-degree of up-stream in airspace network can make arrival traffic flow converge ahead of time, make traffic flow operate faster and increase traffic flow rate.Decreasing key node in-degree of down-stream in airspace network is benefit to congestion dissipating quickly after traffic flow entering congestion phase.More>

2016, 16(2): 100-108. doi: 10.19818/j.cnki.1671-1637.2016.02.012

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Optimization model of arrival and departure resource allocation in terminal area

WAN Li-li, HU Ming-hua, TIAN Yong, ZHANG Si

Abstract: In order to improve the operation efficiency of terminal area and reduce the flight delay, some factors such as airspace capacity and safety interval were considered, the minimum total flight fuel consumption, balance arrival fix holding time and minimum total flight delay were taken as optimization objectives, the optimization model of arrival and departure resource allocation in terminal area was established, the elitist non-dominated sorting genetic algorithm was designed, and example verification was carried out by using the real operation data of Shanghai terminal area.Calculation result shows that when the capacity of arrival fix SASAN decreases, compared with the first come first service(FCFS)strategy, the total fuel consumption decreases by 26.9% from 462 282.7 kg to 337 752.9 kg by using arrival fix allocation(AFA)strategy, HC, CO and NO_x emissions decrease from 492.6, 3 815.7 and 16 570.6 kg to 429.2, 3 352.1 and 14 129.1 kg respectively, total arrival fix holding time decreases by 93.5%, the average delay time of all flights decreases to 104 s, and the delays of 94.6% of flights are lessthan 600 s.Obviously, the optimization model can effectively solve the delay in terminal area because of traffic demand unbalance and fix capacity decrease, and improve the operation efficiency of terminal area.More>

2016, 16(2): 109-117. doi: 10.19818/j.cnki.1671-1637.2016.02.013

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Optimization model of energy-efficient driving for train in urban rail transit based on particle swarm algorithm

HUANG You-neng, GONG Shao-feng, CAO Yuan, CHEN Lei

Abstract: In order to reduce the interstation operation energy consumption of train in urban rail transit, the interstation energy-efficient driving strategy of train was studied.On the basis of considering speed limit and gradient, a energy-efficient optimization model with the constraint of trip time was established, the optimal energy-efficient driving strategy was proposed by using particle swarm optimization(PSO)to optimize the target speed sequence.The optimization method of energy-efficient driving was realized through two phases.In the first phase, under the condition of constant interstation trip time, the interstation energy-efficient driving strategy of train was optimized with PSO, and the relationship between trip time and energy consumption was obtained.In the second phase, under the condition of the constant total trip time of whole interstations, the trip time was redistributed, and the energy-efficient driving strategy of train for the whole line was obtained.Based on the real track data and vehicle parameters of Yizhuang Lineof Beijing Subway, the optimization method was simulated and verified.Simulation result shows that after optimization, the interstation operation energy consumption of train reduces by 6.15%in the first phase in Wanyuan Street-Rongjingdong Street, and the total operation energy consumption of whole interstations reduces by 14.77% in the second phase.So the model can effectively reduce the operation energy consumption of train, and provides a basis for the generation of train timetable.More>

2016, 16(2): 118-124. doi: 10.19818/j.cnki.1671-1637.2016.02.014

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Dynamics model of airdrop process for air transportation cargo

SUN Xiu-xia, XU Guang-zhi, LIU Ri, DONG Wen-han, QI Peng-chun

Abstract: In view of the status that the modeling condition of transport aircraft dynamic model in airdrop process for air transportation cargo was too much simplified, which was far away from the real airdrop project, the current airdrop process dynamic models and their applicabilities were systematic researched, and a separated-body modeling method was established.The forces of airdrop cargoes and aircraft were respectively analyzed without attention on the centroid of cargoes and aircraft, which simplified the modeling process and benefited the qualitative analysis of mechanism of the cargoes to the aircraft.In simulation experiment, the reasonability of dynamic model was verified by using the data of a certain-type transport aircraft.In order to verify the irrationality of small disturbance linearization of aerodynamic parameters, the aerodynamic parameters were processed through 3 modes, the corresponding curves of AOA were comparative analyzed.Under the conditions of different support forces, the application points of traction force, guide models, traction force angle models, and the loading positions of cargo, the built dynamic model of airdrop process was quantitative analyzed and compared with existed models.Simulation result shows that with the assumed conditions including the small disturbance linearization of aerodynamic parameters, assuming the cargoes with known motion law as particles, and ignoring the cabin angle, large model errors are introduced.In the missions of bigtraction ratio and heavy weight airdrop, the influence of the value and direction of traction force on the airdrop dynamic response should be considered.Furthermore, it is significant to install the cargoes near the cabin door of aircraft, which can shorten the moving time of cargoes and reduce the amplitude of interference torque.More>

2016, 16(2): 125-131. doi: 10.19818/j.cnki.1671-1637.2016.02.015

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Combined optimization model of bus-only lane location and transit route network

LU Xiao-lin, YU Jie, ZOU Nan

Abstract: The combined optimization design idea of simultaneously adjusting bus-only lane location and transit route network based on transit corridor was proposed, and two-level optimization model was designed to find the optimal combined design approach of bus-only lane location and transit route network.The combined optimization approach of bus-only lane and transit route network was solves by using the upper-level model with the minimum travel cost, operating cost of bus and maximum operating efficiency of road network, and the passenger flows of car and bus were distributed by using the lower-level model with the minimum generalized travel cost. The genetic algorithm was used to solve the model, the effectiveness and practicability of the model were verified through a case, and the sensitivities of key parameters of the model were analyzed.Analysis result shows that after optimization the routes cover 100% of bus sites and 63 road sections, the coverage proportion of road sections is 76%.The totaltravelling cost in route network is 525 147 yuan, and decreases by 20% compared with present cost 655 282 yuan.The efficiency target value of transit route network is 234 person-times per hour, and increases by 31% from 179 person-times per hour available now.Obviously, the combined optimization approach of bus-only lane location and transit route network based on transit corridor is obviously preferable to the approaches of simply optimizing bus-only lane location and simply adjusting transit route network, and gives play to the network benefits of transit corridor better.More>

2016, 16(2): 132-142. doi: 10.19818/j.cnki.1671-1637.2016.02.016

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Prediction method of OD travel time based on driver's route choice preference

SUN Jian, ZHANG Ying, ZHANG Chun

Abstract: Based on about three million data of more than 3 000 floating cars in Shenzhen City of Guangzhou Province, geographic information system (GIS) technology was used as main tool, the representative Futian and Luohu Districts were used as study areas, and the expansion radii of different OD pairs were determined.Map matching was processed by using the unique number of floating car, the OD path and travel time of floating car were obtained according to the determined study area and expansion radius.The driver's temporal and spatial preferences during route choice were determined, and the OD travel time prediction method based on the route choice preference was established.Using the mean absolute percentage error (MAPE), the root mean square relative error (RMSRE), and the maximum relative error (MRE) as indicators, the travel time prediction methods based on the shortest route, the fastest route and the preference route were compared.Comparison result indicates that compared to the prediction method based on the shortest route, the values of MAPE, RMSRE, and MRE of proposed method decrease by 66.51%, 61.24%, and 61.47% respectively, compared to the prediction method based on the fastest route, the values of MAPE, RMSRE, and MRE of proposed method decrease by 63.64%, 59.70%, and 58.99% respectively, so the prediction precision of OD travel time is significantly improved by using the prediction method of OD travel time based on driver's route choice preference.More>

2016, 16(2): 143-149. doi: 10.19818/j.cnki.1671-1637.2016.02.017

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Coordinated control method of ramps based on automatic tracking dynamic critical occupancy

XU Kun, CHAI Gan, LI Qing-quan, GUO Jian-hua, LI Xiao-da

Abstract: In order to solve the problems of traffic congestion in mainline confluence area and the on-ramp queue overspill for freeway, a coordinated control method of ramps was proposed. Based on the traffic statuses in mainline confluence area and the on-ramp queue lengths, the real-time number of coordinated control ramps was determined to improve the capacity of ramp groups and increase the vehicles merging into the bottleneck area of mainline. To improve the capacity of mainline confluence area, the dynamic critical occupancy of mainline was designed by using the real-time detection data of traffic volume and occupancy of mainline, and its variation was tracked by using the on-ramp metering rate. The heuristic rules were designed according to the relative on-ramp queue lengths to enhance the on-ramp coordinated control ability and prevent the on- ramp queue overspill. Based on Shanghai-Nanjing Freeway G42, the freeway network performance, the traffic condition of downstream mainline confluence area and the queue lengths of ramp were computed by using VISSIM simulation software to evaluate the control ability of the proposed approach. Computation result shows that compared with uncontrolled case, when the proposed method is used, the total travel time reduces by about 8.44%, and the average delay of road network reduces by about 62.97%; when the ALINEA approach is used, the total travel time reduces by about 2.85%, and the average delay of road network reduces by about 21.20%; when the linked-control approach is used, the total travel time reduces by about 6.00%, and the average delay of road network reduces by about 56.17%; when the proposed method is used, the traffic flow in mainline confluence area during congestion increases by about 540 veh·h^-1, and the queue length of each ramp is more balanced. Obviously, the proposed method has good control result. 3 tabs, 12 figs, 25 refs.More>

2016, 16(2): 150-158. doi: 10.19818/j.cnki.1671-1637.2016.02.018

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