2014 Vol. 14, No. 4

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Road and railway engineering
Prediction model of remaining life for airport pavement based on cumulative damage
CAI Liang-cai, WANG Hai-fu, ZHANG Luo-li, WANG Peng-fei
Abstract: Through the statistical analysis on the transverse distribution rules of wheel trace and pavement load stress, the calculation method of pavement pass-to-coverage for landing gear was obtained. Based on the regression formula of load stress on the middle part of pavement slab, the lateral stress distribution function of pavement slab was established. NCHRP1-26 function was chosen as fatigue function, the takeoff data of the 2 types of aircrafts in the next 7 years were calculated based on the historical takeoff data of airport A in the past 13 years, the calculation method of cumulative damage for airport pavement was set up according to the coverage curve function and the stress distribution function, and example verification was carried out.Analysis result shows that, the maximum cumulative damage of pavement tends to be 1 after 2 years, which means the remaining life of airport pavement is 2 years without any maintenance measure.It is consistent with the actual operating condition of airport A, so the established model is effective.More>
2014, 14(4): 1-6.
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Influence of chlorine salt snow-melting agent on road performance of asphalt binder
WEI Jian-guo, FU Guang-wen, FU Qi-lin
Abstract: The asphalt specimens were made by using base asphalt, SBS modified asphalt, NaCl and CaCl2 snow-melting agents.The high temperature property, low temperature property, temperature sensitivity, anti-aging property and infrared spectrum of asphalt soaked by chlorine salt snow-melting agent were studied based on the test methods of softening point, penetration, ductility, viscosity and infrared spectrum.The influence of chlorine salt snow-melting agent on asphalt binder road performance and the erosion mechanism were revealed.Analysis result shows that chlorine salt snow-melting agent improves the high temperature property of base asphalt and reduces the high temperature property of SBS modified asphalt; it lowers the temperature sensitivity of base asphalt and enhances the temperature sensitivity of SBS modified asphalt; it reduces the low temperature property of asphalt, but improves the anti-aging property.CaCl2 snow-melting agent has more significant impact on the road performance of base asphalt, and NaCl snow-melting agent has more significant impact on the road performance of SBS modified asphalt.The snow-melting agent does not react with asphalt, and the molecular structure or functional group of asphalt soaked by snow-melting agent is not changed.More>
2014, 14(4): 7-13.
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Numerical method of multi-layer elastic system by using stiffness matrix method
YANG En-hui, AI Zhang-fa, QIU Yan-jun
Abstract: By using the theory of elastic mechanics and stiffness matrix method, a numerical method of static mechanics for calculating 3D multi-layer elastic system under rectangular coordinate system was developed.2D Fourier transform and Gauss integral method were used, a calculation program was given based on MATLAB mathematical software platform, and the numerical solution of 3D multi-layer elastic system was got.The static mechanics analysis of ballast track foundation structure was carried out by using the numerical method and program, and the calculation results were compared with the results obtained by using general finite element program ABAQUS.Analysis result shows that the maximum vertical displacements of ballast track foundation are 1.50, 1.95 mm respectively by using the numerical method and general finite element calculation method, and the maximum vertical stresses of the foundation are 0.34, 0.21 MPa respectively by using the two methods.The calculation results are close to each other, and the conversion rules of state components are basically the same according to the calculation, so the proposed numerical method and program can be applied to the static mechanics calculation of multi-layer elastic system.More>
2014, 14(4): 14-24.
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Fracture influence of longitudinal-continuous base layer on force characteristics of CRTSⅡ slab ballastless track on bridge
CHEN Xiao-ping, WANG Fang-fang, ZHAO Cai-you
Abstract: The mechanics model of longitudinal interaction between CRTSⅡ slab ballastless track and bridge was established considering the fracture of longitudinal-continuous base layer(LCBL), and was solved by finite element method.Key calculation parameters of ballastless track were determined.A bridge with long-span continuous beam was taken as an example, the longitudinal forces and displacements of rail, slab, mortar and bridge support were analyzed when LCBLs with the temperature reductions of 10, 20, 30, 40, 50 ℃ were fractured at 7 typical positions on long-span continuous beam.Analysis result indicates that when the temperature reduction of LCBL is 30 ℃, and LCBL is fractured on long-span continuous beam, the maximal additional longitudinal forces of rail and slab are 155.75 kN and 233.21 kN respectively.The influence of LCBL fracture on the additional longitudinal forces of rail and slab are significant.When the temperature reduction of LCBL does not exceed 10 ℃, no matter LCBL is fractured at any position on long-span continuous beam, the longitudinal relative displacement between slab and LCBL is less than 0.5 mm, and mortar can't crack.When the temperature reduction of LCBL is 50 ℃, the maximal additional longitudinal force of fixed support caused by LCBL fracture at any position on long-span continuous beam is 196.12 kN, bridge fixed support can't be destroyed directly by LCBL fracture.When the maintenance operation of LCBL is carried out, it is recommended that the temperature difference between sawing and laid LCBL can't exceed 10 ℃, and rail strength must be checked out to meet the requirements.More>
2014, 14(4): 25-35.
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Shear lag effect analysis of flat steel box girder
QIAO Peng, ZHOU Xu-hong, DI Jin
Abstract: The shear lag effects of flat steel box girder under concentrated and uniform loads were studied by using finite element method.Considering the reasonable ranges of design parameters of flat steel box girder, the influences of some parameters including the width and height of cross section, the thicknesses of top and bottom slabs, the thicknesses and spacings of longitudinal and transverse diaphragms on shear lag effects were analyzed.Based on the result of theoretical analysis, the practical formula was proposed to calculate the shear lag coefficient of flat steel box girder by using mathematical regression analysis, and the calculation result of practical formula was compared with the result of finite element method.Analysis result indicates that span-width ratio has the most significant influence on shear lag effects, when the span-width ratio increases from 1.786 to 8.926, the shear lag coefficients of top and bottom slabs decrease from 1.40 and1.32 to 1.07 and 1.06, and decrease by about 20%.When the thickness of longitudinal diaphragm increases from 10 mm to 30 mm, the shear lag coefficient of side web decrease by 7%, while the coefficients at other positions change by less than 1%.When the ratio of longitudinal diaphragm spacing to girder width increases from 0.430 to 0.582, the shear lag coefficient increases by 9%.Other parameters have negligible effect on shear lag coefficient.The relative error between the results of proposed practical formula and finite element method is less than1%, which conforms the formula has higher calculation precision, and meets the need of engineering calculation.More>
2014, 14(4): 36-44.
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Transportation vehicle engineering
Flexibility characteristics of suspension system for railway vehicle
SHI Huai-long, WU Ping-bo, CENG Jing, ZHANG Da-fu
Abstract: A mathematical model of a railway vehicle equipped with air springs was built, the theoretical formulas of flexibility coefficient for suspension system were deduced, and the effects of suspension parameters on the coefficient were studied.Gravity method, angle measuring method and acceleration measuring method were designed to measure the coefficient.Gravity method was applied to measure the coefficients of motor car and trailer under different superelevation and loading conditions respectively.Theoretical analysis result shows that the greater the stiffness and lateral distance of suspension system are, and the lower the centers of gravity for carbody and frame are, the smaller the flexibility coefficients are, which can improve the antioverturning performance of vehicle.Test result illustrates that the coefficient of trailer is greater than that of motor car with a difference of 0.021 under unloading condition, but little divergence under loading condition.The coefficient under loading condition is greater than the coefficient under unloading condition with a maximum divergence of 0.109, and the severe situation occurs under loading condition for trailer with the maximum value of 0.245.The coefficient increases with the increase of super-elevation of outer rail, and the greater the super-elevation is, the more rapid the coefficient increases, which means that the flexibility should be controlled seriously for large super-elevation track.The credibility of theoretical analysis is verified and validated by test result, and the obtained formulas are reasonable and include comprehensive suspension parameters.More>
2014, 14(4): 45-52.
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Calculation method of grounding ship during righting process
PAN De-wei, LIN Cheng-xin, SUN De-ping, ZHOU Chao-yu
Abstract: In order to study the salvage of grounding ship, the changes of grounding force and trim angle during righting process were computed.The function of free surface in cabins during righting process was analyzed.The force module of grounding ship was established based on the stress characteristics of grounding ship.Considering the shortcomings of traditional calculation method of grounding force, taking an grounding ship as an example, the grounding force of every grounding point, total grounding force, heel angle and trim angle were calculated during righting process simulated by GHS software.The righting processes of ship with different grounding states were compared through simulation, and the effects of the positions of grounding point, draft, shiplines and weight distribution on the force and attitude of grounding ship were analyzed.Analysis result indicates that for grounding ship with dispersion of grounding point or deep draft, the variation of trim angle is relatively smaller, and is 0.1%-2.0%of that of other situation.The variations of total grounding forces for grounding points which are dissymmetrical about midship are smaller than the variations that the points are symmetric about midship, and the variations of the formers are 35%-65%of the laters.The influence of free surface add more difficulties to wreck salvage, and so it should be emphatically considered in making salvage scheme.The overturn speed of wreck in the project should be controlled in order to avoid blocking of righting progress or further damage to ships.More>
2014, 14(4): 53-63.
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Composite braking control strategy of pure electric bus based on brake driving intention recognition
ZHAO Xuan, MA Jian, WANG Gui-ping
Abstract: To research braking force distribution ratio of composite braking system for pure electric bus, a composite braking control strategy based on brake driving intention recognition was presented.A double-layer brake driving intention recognition model based on hidden Markov theory was set up and identified by using road experiment data.Based on recognized driving intention and vehicle speed, the distribution ratios of braking forces for front and rear wheels, ECE regulation, motor characteristics, slip ratios, battery characteristics, super capacitor characteristics and transmission system characteristics were taken as constraint conditions, the braking force distribution strategy of composite braking system was proposed, and the control strategy of composite braking system was simulated by Simulink software under 9 operating conditions.Simulation result shows that friction braking system and motor regenerative braking system can work coordinately and steadily under various operating conditions when the braking control strategy is applied, and braking energy can be recovered as much as possible under the premise of ensuring braking safety.Energy recovery efficiency is highest under slight brake when vehicle speed was low, and the efficiency can reach to 43.84%.Energy recovery efficiency is lowest under emergency brake when vehicle speed is high, and the efficiency is only 0.89%.More>
2014, 14(4): 64-75.
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Transportation planning and management
Spatial and temporal distribution characteristics of traffic accident for highway vehicle queue tail
LI Zhi-bin, WANG Wei, LI Xiao-wei, WANG Hao
Abstract: Based on the traffic flow data of recurrent congestion section on highway, the cumulative occupancy method was used to draw the fluctuating curve of traffic flow occupancy, which was used to judge the trajectory of vehicle queue tail at congestion section.The relations among occupancy, mileage position and time interval were analyzed.The inflection point of cumulative occupancy curve was determined.For the queue propagating and dissipating processes, the relations between traffic accident frequencies and temporal and sptial distances were analyzed, and the distribution features were statistically studied.Analysis result shows that when vehicle temporally and spatially approaches the queue tail, the occurrence frequency of traffic accident obviously increases, and the temporal distance and spatial distance follow the normal distribution centered on the queue tail.Normal distribution curves in different driving directions have no significant differences, but have significant differences between congestion propagation and dissipation processes.The developed joint normal distribution model of traffic accident occurring probability can be used to predict the traffic accident risks in the vicinity of queue tail, and to provide the theoretical foundation for applying dynamic traffic control for improving highway safety.More>
2014, 14(4): 76-81.
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Comparison of toll road regulation effects under different goal conditions
FAN Jian-qiang, XU Hai-cheng
Abstract: In order to compare the influences of regulation measures on the economic variables of toll roads under different goals, the regulation models of toll roads under different goals were built by using the basic theories of welfare economics and regulation economics, and the differences of major economic variables in five different regulation models were compared by simulation calculation.Analysis result shows that it is easy to lead to business losses under the objective of social welfare maximization with no regulation.The toll price will increase under the objective of social welfare maximization with a breakeven on the finance of toll road.The road capacity and social welfare will decrease under the objective of profit maximization with no regulation.It is helpful to increase not only social welfare but also corporate profit under the objective of profit maximization with traffic volume regulation and travel cost regulation.The objectives of social welfare maximization and profit maximization are difficult to be achieved at the same time, but it is helpful to reconcile the differences between the two goals under toll road concession with government regulation.More>
2014, 14(4): 82-88.
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Calculation method of whole life-cycle energy consumption for urban rail transit
CHEN Jin-jie, GAO Gui-feng, WANG Xing-ju, WANG Xiang-qin
Abstract: Based on the whole life-cycle theory and the characteristics of urban rail transit, the concept of whole life-cycle energy consumption was proposed, and the whole life-cycle of urban rail transit was divided into five stages, including plan and design stage, equipment and material production stage, construction stage, operation and maintenance stage, demolition and disposition stage.The mathematical models of energy consumption for 5 stages were set up, the energy consumption of No.5 rail transit line in a northern big city of China was quantitatively analyzed by using the mathematical models, and the total energy consumption of whole life-cycle and the energy consumption in every stage were calculated.Calculation result shows that the energy consumption proportions at the five stages are 0.004%, 24.391%, 3.884%, 68.613%and 3.108%successively during whole life-cycle.The energy consumption of operation and maintenance stage is biggest, so the operation and maintenance stage is the key point of energy consumption control.The energy consumption of equipment and material production stage is the second biggest, the use of green energy saving materials can play an important role in reducing energy consumption.More>
2014, 14(4): 89-97.
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Evaluation method of driving proficiency based on fixation transition mode
GUO Ying-shi, YUAN Wei, FU Rui, XUE Chuan-liang
Abstract: In order to quantitatively and objectively evaluate the driving proficiency of driver, the collected data from eye movement tracking device was analyzed in real vehicle test environment.By using fixation area division method, 8 characterization parameters of fixation transition mode were chosen as evaluation indexes.Principal component analysis(PCA) method was using to analyze the eye movement experiment data of 15 drivers, and the calculation method of driving proficiency evaluation based on fixation transition mode was built.Test result shows that the evaluation score of driving proficiency has close relationship with the driving experience mileage.When the threshold ralue of driving experience mileage is 50 000 km, the driving proficiencies of two groups of drivers can be distinguished by using the proposed method, but in each group, the evaluation scores of driving proficiencies have unobvious regularity.More>
2014, 14(4): 98-104.
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Traffic information engineering and control
Concept, architecture and challenging technologies of ubiquitous traffic information service system
ZHAO Xiang-mo, HUI Fei, SHI Xin, MA Jun-yan, YANG Lan
Abstract: The limited awareness abilities, simple service modes and long delays of updating dynamic informatioh of most existing traffic information service systems were analyzed.A novel framework of ubiquitous traffic information service system(U-TISS) was proposed based on the current TISSs, and the research and development tendencies of traffic engineering and information science.U-TISS integrated advanced cooperative sensing, ubiquitous network, cloud computation and big data to realize the deep fusion between TISSs and traffic cyber physical systems.The architecture of U-TISS mainly consisted of four layers, including sensing, network, computation and service.In sensing layer, a comprehensive sensing on pedestrians, vehicles, roads and environments were carried out by sensors, RFIDs, readers, cameras, GPS, vehicle intelligent terminals, etc.In network layer, peripheral communication and carrying network communication were implemented, such as ZigBee, bluetooth, DSRC, 3G/4G, and wired link, and an accurate capture and release system was built to timely collect and transmit traffic information by short-range communication between roads and cars, self-organizing network, and carrying network between roadsides and monitor centers.In computation layer, cloud computation extracted traffic information effectively to enhance the service quality of traffic information.In service layer, a service platform was constructed based on ubiquitous network and cloud computation.Its information was released timely by mobile intelligent terminals, vehicular terminals, information broadcasts and variable signal boards, and the auxiliary decision support was provided to realize the intelligentization and individuation of information service.The key technologies of U-TISS implementation were analyzed, including pervasive sensing and interaction of smart devices, accurate measurement of vehicle position and orientation, cooperative sensing of traffic information with road side units, communication and networking of vehicle-to-vehicle/vehicle-to-infrastructure, on-board mobile internet, traffic information management in the cloud, analysis and excavation of traffic big data, and information security and privacy protection.Analysis result shows that the characteristics of U-TISS are ubiquitous sensing, open interconnection, real-time transmission, deep mining and high quality service, and can improve the service level of TISS in safety, high efficiency, convenience and environmental protection.In term of safety, wireless communication and networking technology provide drivers with multi-scale tempo-spatial traffic information beyond the line of sight and the sensing capability of vehicles.In term of high efficiency, ubiquitous sensing of massive traffic information and big data analysis based on cloud computing techniques can achieve the efficient operation of transportation systems with refinement of management.In term of convenience, the public can get personalized and customized travel information through smart devices.In term of environmental protection, vehicle control systems can be optimized by the information of driving environment, and the awareness of ecodriving behaviors can be raised by big data and social network, so that green travel is realized.With the breakthrough of key technologies and the issuing of related standards and norms, the innovation and change of business mode will occur in the field of traffic information service, which will lead to collaborative intellieent transDortation.More>
2014, 14(4): 105-115.
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Cooperative vehicle positioning method based on GNSS/DSRC fusion
LIU Jiang, CAI Bo-gen, WANG Yun-peng
Abstract: Aiming at the integration and information fusion of global navigation satellite system(GNSS)positioning and the cooperative positioning based on dedicated short-range communication(DSRC), an advanced selection strategy for neighborhood vehicle nodes for DSRC-based cooperative positioning was proposed based on the minimum principle of horizontal dilution of precision.For GNSS/DSRC integrated vehicle positioning, a loose-coupling positioning method was designed according to decentralized estimation scheme.In the positioning method, the parallel GNSS and DSRC filters were combined for global estimation, and the adaptive capability against different operation conditions was enhanced based on feedback strategy.The cooperative vehicle positioning method was verified by using a cooperative vehicle infrastructure simulation platform.Verification result indicates that the precision of DSRC-based positioning method was significantly improved by the selection strategy of neighborhood vehicle nodes.When the DSRCbased positioning method was used in the GNSS/DSRC integrated positioning, under normal operation condition, the precision of decentralized fusion estimation with feedback is better than that with single sensor mode and the decentralized estimation without feedback.Compared to the GNSS-alone mode under the given GNSS multipath interference condition, the root mean square errors of vehicle positioning method reduce by 42.6% and 37.0% in east and north direction respectively, and they reduce by 24.8% and 20.3% compared to the centralized fusion estimation.The performance of proposed positioning method is better than conventional positioning solutions, and has an enhanced tolerant ability to GNSS multipath interference conditions, which suggest the better precision, availability and practical application value of proposed method.More>
2014, 14(4): 116-126.
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