交通运输工程学报

Joint bearing mechanism of structure and foundation for gravity anchor block of suspension bridge

YIN Xiao-tao, YAN Fei, ZHOU Lei, WANG Dong-ying, DENG Qin

Abstract: Based on the gravity anchor block engineering in Xuanwei Bank of Puxuan Highway, three kinds of computing schemes such as no backfilling & no pretension, no backfilling & pretension and backfilling & pretension were designed, and the mechanical mechanisms and fail modes of gravity anchor block and foundation were analyzed on basis of numerical test.Bearing mechanism presents that when the loads are less than 8 times of design load, plastic deformationcan't occur, the working situation is elastic, the maximum of deformation locates on the interface of structure and foundation, the friction effect is dominant, the tensile stress zone under foundation is controllable, and the anti-slipping and anti-overturning stability of anchor block is stable or controllable.When the loads are larger than 12 times of design load, the plastic zone expands step by step, and until to 20 times of design load, the plastic zone is cut-through.The plastic strain under the structure and the structure deformation of anchor block aspect are observable.The rock mass clamped by structure is broken.The clamping effect is dominant.The tensile stress zone under foundation is uncontrollable.The anti-slipping and anti-overturning stability of anchor block is unstable or uncontrollable.The prestress of anchor block acts only before the compatible deformation of structure and foundation, and the action fades away after the compatible deformation.Backfilling can greatly improves foundation's stress state and structure's torsional deflection, anti-slipping and anti-overturning stability, so the enhancement effect can be considered within the scope of allowable deformation.The joint deformation and bearing mechanisms of gravity anchor block and foundation are comprehensively performed by friction effect, clamping effect and backfilling effect.Monitoring result denotes that the interface safety of anchor block and foundation can be controlled by monitoring the tensile and compressive stress of base bottom, and the monitoring data are less than 3 MPa that is allowable bearing capacity of foundation.The anti-slipping stability of the structure is monitored by using the deflection and the deeply horizontal displacement of foundation, and the practical monitoring values are less than 1 mm.The anti-overturning stability of structure is monitored by using the uneven sedimentation of structure corners, and the inclined value is less than 0.006.The inner maximum monitored temperature of mass concrete is less than 60℃, the temperature difference of input and output water is less than 15 ℃, the temperature difference of anchor block's inner and surface is less than 20℃, and the post-peak cooling rate is less than 3 ℃·d^-1.The changing amplitudes of stresses of anchor cables are less than 5% of design stress.More>

2017, 17(2): 1-11.

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Uneven settlement characteristics and influence factors of metro elevated structures in soft soil region

WU Nan, XIAO Jun-hua

Abstract: In order to study the uneven settlement characteristics of elevated structures of a metro line in soft soil region, a long-term settlement observation was carried out during construction period and operation period, and the observed objects included elevated stations, elevated intervals with prestressed concrete simply supported beam bridges and large-span prestressed continuous bridges.The uneven settlement characteristics of piers and track beds of elevated substructures and their influence factors were investigated, and the settlement development rules during operation period and construction period were compared.Analysis result shows that after 2 years of operation, the maximum settlement of piers is 12.4 mm with relative to the beginning settlement of operation, and there is still a trend of continuous development.Six settlementtroughs are observed on the studied metro line because of the activities of construction engineering around the metro line.Totally, the differential settlements of adjacent piers are less than 2 mm.The settlement of elevated station mainly generates during construction period, the maximum accumulative settlement is about 17.5 mm at the moment, and the total maximum accumulative settlement only is 18.8 mm during both construction period and operation period.The differential settlements of bridge piers in elevated intervals are unconspicuous during both construction period and operation period, the maximum accumulative settlement during construction period is 14.2 mm, and the total maximum accumulative settlement is 23.9 mm during both construction period and operation period.Most of ballast bed slabs on simple support beam bridge in elevated intervals have upward deformations, and the maximum deformation is 8.9 mm.While the ballast bed slabs on the main spans of large-span continuous beam bridge have large deflections, and the maximum deformation is 29.2 mm.More>

2017, 17(2): 12-20.

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Temperature variation properties of pavements and subgrades for high-grade roads on Qinghai-Tibet Plateau

QUAN Lei, TIAN Bo, NIU Kai-min, XIE Jin-de, HE Zhe, ZHANG Ying-hui

Abstract: The temperatures of different deeps of roads and natural ground were continuously measured in permafrost regions on Qinghai-Tibet Plateau, and the variation tendencies of daily mean temperature (DMT) with time and depth, and the frequency distributions of real-time temperature and the freeze-thaw properties of different structural layers were analyzed.Analysis result shows that the annual change rules of DMTs of air, surface layer, base layer, subgrade and natural ground demonstrate high-temperature periods and low-temperature periods, and the corresponding shifting times are April and September.The DMT of surface layer of asphalt concrete pavement varies from-17 ℃ to 40 ℃ in yearly observation period, and the DMT of surface layer of cement concrete pavement varies from-18℃to 17℃.At 0.8 m-depth from the top surface of subgrade under asphalt concrete pavement and 0.7 m-depth from the top surface ofsubgrade under cement concrete pavement, the DMTs vary from-2.8 ℃to 6.3 ℃ and from-3.4 ℃to 5.4 ℃, respectively.The frequency distributions of temperatures and temperature gradients of air, surface layer of asphalt concrete pavement and surface layer of cement concrete pavement display obvious single-peak shapes, and there are deviations between the temperatures or temperature gradients corresponding to the peak values and the annual mean values.The frequency distributions of temperatures of base layer, sub-base layer and subgrade present multipeak shapes, and the peak values correspond to low-temperature period, high-temperature period and their transition period, respectively.The freeze-thaw cycles of surface layers of asphalt concrete pavement and cement concrete pavement are 182 and 178 in yearly observation period, respectively.The frequency distributions of freeze-thaw lasting times of asphalt concrete pavement and cement concrete pavement have one main peak and several sub-peaks, respectively, and the main peak usually appear in the interval of 0-2 hor 18-20 h.Obviously, it is given priority to choose cement concrete pavement in order to protect the permafrost in permafrost regions, and the freeze-thaw durability performance shall be verified in the mix proportion design of asphalt concrete and cement concrete.More>

2017, 17(2): 21-30.

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Influence of subgrade modulus on fatigue cracking damage of cement concrete pavement under traffic load

WU Yu, JIANG Xin, WU Chao-yang, LIU Zhu-jun, QIU Yan-jun

Abstract: Based on finite element software KENSLABS, the damage calculation model of cement concrete pavement under traffic load was established.Based on the foundation seasonal adjustment factor and the zero-maintenance fatigue criterion, the influence of overall decrease of subgrade modulus on the fatigue cracking index of pavement was analyzed, the dependence of equivalent axle load factor and number of repetitions for one passage of multiple axles on subgrade modulus was discussed, and the relationships between the cracking index of pavement and the core parameters of pavement design including slab thickness, modulus of rupture of cement concrete, uniaxial load weight, repeated times of uniaxial load in one day were studied.Analysis result indicates that when the seasonal adjustment factor of foundation decreases from 1.0 to 0.8 and from 0.4 to 0.2, the growth rates of cracking index of pavement are 2.8, 2.9, 1.5 and 49.8, 269.0, 1351.4 under the uniaxial load, biaxial load, triaxial load, respectively, so the fatigue cracking index of cement concrete pavement increases with the decrease of seasonal adjustment factor of foundation, and the smaller the seasonal adjustment factor of foundation is, the faster the increase of the fatigue cracking index is.When the subgrade modulus is 60 MPa and the thickness of slab are 15 cm or 35 cm, the uniaxial load is more destructive than the biaxial load, and the biaxial load is more destructive than the triaxial load.The same is true for 15 cm slab with a subgrade modulus of 20 MPa.But for 15 cm slab with a subgrade modulus value of 60 MPa, the order is reverse.So the equivalent axle load factor and the number of repetitions for one passage of multiple axles are affected by slab thickness and subgrade modulus.When the subgrade modui are 20 MPa and 60 MPa and the thickness of slab increases from 21 cm to 25 cm, the fatigue cracking indexes decrease by 1.18×10 and 1.18×10^-2, respectively.When the modulus of rupture of cement concrete increases from 4.0 MPa to 4.4 MPa, the fatigue cracking indexes decrease by 1.28 and 2.20×10^-3, respectively.When the uniaxial weight increases from 80 kN to 160 kN, the fatigue cracking indexes increases by 5.48 and 7.36×10^-3, respectively.When the repeated times of uniaxial load in one day increases from 50 to 90, the fatigue cracking indexes increase by 2.05×10 -1 and 5.07×10^-4, respectively.So when the fatigue cracking index of cement concrete pavement varies with slab thickness, modulus of rupture of cement concrete, uniaxial weight, repeated times of uniaxial load in one day, there is a direct relationship between its ranges and subgrade modulus.When 15 cm cement stabilized base is added, the fatigue cracking design life of pavement increases by 3.42 years under designing working condition.At the same time improving subgrade modulus, some measures including appropriately adding slab thickness, strictly forbidding overloading, setting cement stabilized base should be taken into account preferentially to control the fatigue cracking damage of cement concrete pavement under traffic load.More>

2017, 17(2): 31-40.

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Influence of ground fissure activity on subway tunnel in third-kind surveying site

MENG Zhen-jiang, PENG Jian-bing, HUANG Qiang-bing, DENG Ya-hong, ZHAO Lin-hao, XING Yan

Abstract: The ground fissures of Xi'an third-class surveying site that metro tunnels pass through were taken as research prototype, their development characteristics were analyzed.The variation characteristics of stress fields, failure zones and displacement fields caused by the different dislocation amounts of ground fissures in third-class surveying site were studied by using numerical simulation method, and the influence areas of fissure activity were calculated.The failure characteristics of metro tunnel structure caused by fissure activity were analyzed, and thecorresponding engineering measures were proposed.Research result shows that the vertical stresses on both sides of ground layers present approximate anti-symmetric forms caused by ground fissure activity, and the mutative increments of stresses increase with the increase of hanging wall settlement.Based on comprehensively analyzing the variation characteristics of vertical stresses at the positions of vault and arch bottom of subway tunnel, the main influence ranges of hanging wall and footwall of ground fissure are 0-20 mand 0-15 m, respectively, which is consistent with the result of physical model test by contrasting verification.The footwall occurs shear failure near the ground fissure, the rupture spreads up gradually, a shear failure envelope line with 18°angle relative to the ground fissure forms, and the middle section is concentrated area of shear failure.The fissure activity leads to the displacement mutation of soils on its both sides, two deformation areas similar to active wedge forms, and expand gradually.The differential settlement amounts of metro tunnel on the hanging wall and footwall increase with the displacement increase of ground fissures.When the displacement of ground fissure is 20 cm, the deformation of integral metro tunnel is S-shape.In order to meet the large deformation caused by the activity of ground fissures in third-class surveying site, the special deformation gap-flexible joint treatment measure is proposed to fortify the structure of metro tunnel.More>

2017, 17(2): 41-51.

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Parametric vibration stabilityof locomotivegear transmission system with tooth surface friction

WANG Yan, LIU Jian-xin, LI Yi-fan, YU Da-lian, XIE Ming

Abstract: Aiming at solving the problem of parametric vibration of locomotive gear transmission system, the dynamic model of gear transmission system was established considering tooth surface friction.In the model, the time-varying mesh stiffness was obtained based on the potential energy method, fitted by using the technique of Fourier series, and solved by using the method of multiple scales to gain the boundary condition of parametric stable vibration.Finally, a case study was carried out for studying the influence of tooth surface friction on the parametric vibration stability.Analysis result indicates that when the resonance speed is about 119.02/j km·h^-1 (j is harmonic term), the prametric vibration will happen under the condition that friction coefficint is 0.The greater the friction coefficient is, the bigger the resonance speed at corresponding harmonic term is.Meanwhile, there exist an unstable vibration region in the vicinity of resonance speed.Under the condition that the damping coefficient and the friction coefficient are 0, when the harmonic terms are 1, 2, 3, 4, respectively, the corresponding fluctuation ranges relative to resonance speeds are about 9.16, 1.46, 0.53, 0.55km·h^-1, respectively, so the system is unstable.Under the condition that the damping coefficient is 0, when the friction coefficients are 0.1and 0.2, respectively, compared to the result that the friction coefficient is 0, the fluctuation ranges relative to resonance speeds increase by about4.88%, 9.54%, respectively, with the corresponding harmonic term in unstable vibration regions.But when the damping coefficient is 0.01and the system is unstable, with the increase of friction coefficient, the fluctuation range relative to resonance speeds does not necessarily increase.Furthermore, the larger the friction coefficient is, the smaller the damping coefficient required by the stability of system is.5tabs, 13figs, 30refs.More>

2017, 17(2): 52-63.

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Drag reduction technology of high-speed train based on boundary layer control

ZHU Hai-yan, ZHANG Yi, ZHAO Huai-rui, WU Ping-bo, SHAO Xiao-feng

Abstract: A drag-reduction technique based on boundary layer control was proposed to reduce the aerodynamic drag during the operation of high-speed train.Taking CRH3 as an example, the turbulence characteristics of boundary layer was controlled by mounting ball sockets non-smooth surface on the surface of vehicle body to achieve train's drag reduction.The models of high-speed train, parametric ball socket and computational domain were established by means of PRO/Engineer software, and the body model of high-speed train was simplified without any impact to the research effect in order to reduce numerical simulation computing cycle.The non-structure grid partition of computed field was carried out by ICEM CFD software to enable the grids to better fit in with streamlined body and ball sockets non-smooth surface.In consideration of the effect of train's surface roughness on the aerodynamic drag, the k-ε turbulence model incommercial fluid software FLUENT was applied to conduct numerical simulation analysis of outside flow field in open air at the running speed of 300 km·h^-1.Simulation result shows that only placing the ball sockets non-smooth surface on the tail of train is more conducive to reduce the aerodynamic drag.Train's aerodynamic drag first decreases and then increases with the increase of the radius, depth and array distance of ball sockets.When the ball socket non-smooth surface is placed on the tail of train, and the array distance, radius and depth of ball sockets are 350, 80 and 10 mm, respectively, the drag reduction effect is best.The aerodynamic drag for the ball socket non-smooth surface is 2 220.4Ncompared to 2 967.9N without placing ball sockets, so the drag reduction rate is up to 25.19%.Obviously, using ball sockets non-smooth surface to change the turbulence characteristics of boundary layer is an effective way to reduce train's aerodynamic drag.More>

2017, 17(2): 64-72.

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Calculation method of still water shear force and bending moment based on STL model

LIU Chun-lei, YIN Yong, SUN Xiao-feng, ZHANG Xiu-feng, SHEN He-long

Abstract: To improve the calculation accuracy of ship strength, a method based on STL model was proposed to calculate still-water shear force and bending moment of ship.In calculating the total longitudinal strengths, the initial values of ship floating condition were calculated by the conventional method, and then the draught, heeling angle and trim of ship were calculated by the iteration method.The transverse section of each rib was obtained by cutting the hull according to the rib position, the area of underwater part of each section was calculated by using the Green formula, and the buoyancy curve was obtained by the longitudinal integration.The mass distribution table of each cabin was established offline by cutting the STL model of ship cabin, and the actual mass distribution of cabin was used instead of the trapezoid mass distribution to calculate the mass distribution curve.Finally, based on the distribution curves of buoyancy and mass, the bulk carriers "Taihang 128"and "SPRING COSMOS"were taken as examples tocalculate the shear forces and bending moments under 5 typical loading conditions.Calculation result shows that the average relative errors of shear forces and bending moments calculated by the proposed method and the design software NAPA of ship are about 1%, the maximum error is 2.6%, the errors are smaller, so the accuracy of proposed method is higher.The iterative algorithm of ship floating condition only needs to calculate the drainage volume and buoyancy center coordinates of ship in free floating condition, so the program is simple, stable and reliable.The proposed method is applied to any floating condition of ship, the buoyancy distribution curve of ship can be calculated by directly cutting the hull, so the proposed method makes up for the deficiency of the conventional method that can calculate only ship's longitudinal strength.By establishing the mass distribution table of ship cabins and using the actual distribution of mass instead of the traditional trapezoid distribution of mass, the calculation precision of ship strength rises, and the calculated amount reduces.More>

2017, 17(2): 73-82.

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Optimization model of ballast water allocation for crane ship

LIU Zhi-jie, LIU Xiao-yu, XIONG Wei, LIN Cheng-xin

Abstract: Based on the hydrostatics and optimal theories of ship, the optimal model of ballast water allocation for crane ship was built.The optimal variables were the variations of water levels for all ballast tanks.The optimal objective was minimizing the ballast water's total allocation volume of ballast tanks.The constraint condition was hull balance in the lifting-allocating process.The ballast water allocation process of a crane ship with 8 ballast tanks was optimized by using MATLAB to reduce the energy consumption of crane ship.Calculation result shows that only 3 ballast tanks are used in the allocation process for the allocation scheme designed by engineering experience, and the requirement of hull balance is satisfied when the water in tank 1 is allocated into tanks 2, 8.When the proposed model is used, the water in tanks 1, 3, 4, 5, 6 is allocated into tanks 2, 8.Although 7 tanks are used in the allocation process, the total allocation volume reduces by 21% compared with the empirical scheme.For both the empirical scheme and optimal scheme, when the rotating angle of crane is 0, the ballast water allocation volumes are largest, and reach 487.5t and 256.0t, respectively.In order to avoid hull tilt caused by rapidly loading, the crane ship is loaded and allocated gradually at the moment.In the allocation process, when the water level of a ballast tank decreases to 0, the ballast water allocation volume will suddenly change at the next moment.At the moment, the crane should run slowly so that the ballast system can allocate enough ballast water to guarantee hull balance and avoid serious consequence.More>

2017, 17(2): 83-89.

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Dynamic coordinated control method of driving mode switch of parallel hybrid electric vehicle

WANG Wei-hua, WANG Wen-kai, FENG Bo, FAN Yong-kai

Abstract: In the driving mode switch of parallel hybrid electric vehicle (HEV), a control method of motor torque compensation was put forward based on the PID control of the difference of wheel angular velocity, and the control objective was that the demand torque of vehicle power did not fluctuate and vehicle speed steadily followed its expectation. The frequency-domain characteristics of HEV driveline in the mode switch were analyzed.Based on the difference between actual and expected angular velocity of wheel, the compensation torque was computed by the PID closed-loop control and provided by the permanent magnet synchronous motor (PMSM) to solve the dynamic coordinated control problem of two kinds of power sources in mode switch.A HEV dynamic coordinated control model was built by using two simulation platforms of AVL Cruise and MATLAB, and the control method was simulated and verified by using the control model.Simulation result shows that compared with the mode switch without dynamic coordinated control, when the dynamic coordinated control method is used, the response time of total output torque reduces from 0.90 s to 0.08 s, the control precision of total output torqueincreases by 11.1%, the precision of following expected speed increases by 8.0%, and vehicle's power performance increases by 4.4%.Obviously, the dynamic coordinated control method reduces the fluctuation of total output torque during HEV mode switch, improves the following precision of speed, and effectively guarantees the power performance and driving comfort of vehicle.More>

2017, 17(2): 90-97.

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Boarding duration distribution of aircraft turnaround

FENG Xia, ZHANG Xin, CHEN Feng

Abstract: In order to accurately predict aircraft turnaround boarding duration, the randomness and catchable regularity of boarding duration were studied.Combining the operation situation of Beijing Capital International Airport, the aircraft turnaround data were grouped according to aircraft type, gate position and arrive time on the basis of analyzing the main factors influencing on the boarding duration.The frequency of aircraft boarding duration was counted, and the distribution of boarding duration was fitted by using normal distribution, Weibull distribution and Poisson distribution.Chi-square fitting goodness was used to test each distribution, the unknown parameters of the distributions were estimated by the maximum likelihood estimationmethod, the complete distributions of boarding duration in different combined conditions were got, and the distribution models of boarding duration were constructed.Analysis result shows that the distribution of boarding duration can be fitted by the three distributions, and the fitting goodnesses are larger.Weibull distribution adapts to every group of data.However, normal distribution and Poisson distribution have better fitting goodnesses in groups Ⅲ (medium-sized aircraft, contact stands, 22:00-23:59), Ⅴ (medium-sized aircraft, remote stands, 09:00-21:59), Ⅶ (large-sized aircraft, contact stands, 00:00-08:59), Ⅷ (large-sized aircraft, contact stands, 09:00-21:59), and Ⅸ (large-sized aircraft, contact stands, 22:00-23:59).The distribution models can be used to forecast the boarding duration well, and the average error of the actual values and the calculated values is less than 2 min.When the confidence level is 90%, the distribution interval width is 10-12 min, and the average prediction accuracy is 83.63%.When the confidence level is 75%, the distribution interval width is 7-9min, and the average prediction accuracy is 66.94%.It can be seen that the accuracy of the distribution interval almost reachs the confidence level.Obviously, the distribution models can be used to predict the aircraft boarding duration accurately.More>

2017, 17(2): 98-105.

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Structural complexity and spatial differentiation characteristics of taxi trip trajectory network

FU Xin, YANG Yu, SUN Hao

Abstract: Based on the GPS trajectory data of taxis, a kind of urban trip complex network was constructed.The structural complexity and differentiation characteristics of taxi trip trajectory network were researched by using the directed-weighted complex network measuring method.Based on the taxi trip data of Xi'an, the network indexes were calculated.Analysis result shows that the average shortest path length of taxi trip trajectory network is 2.07 (edge number), the clustering coefficient is 0.653, and the network density is 0.554.So the network is a kind of typical complex network, with typical "small-world"and "collective"characteristic, and the actual average trip distance obeys log-normal distribution.The average value of node strengthsfor the network is 411, the largest K-nuclear value is 59, and the proportions of nodes with the strengths being less than 600 and 300 are 77.97% and 50.24%, respectively, which shows the typical spatial distribution that is described as"less nodes with greater strengths but more nodes with less strengths".The network has significant spatial differentiation characteristic, the traveling radiation scopes of important traffic analysis zones (TAZs) have overall characteristic, the whole spatial layout of trip intensities is consistent with public transport arterial lines, and presents a cross type distribution.The high-level centricity TAZs in whole network present agglomeration distribution, and the node strengths of important transport hubs (stations) and CBD areas are more than 2 200.The distributions of pick-up and drop-off areas of taxis are nonequilibrium, and the pick-up level is higher than the drop-off level in the important functional zones of city.Obviously, this research result indicates the interaction relationship between the topology structure and spatial differentiation of taxi trip trajectory network, and reveals urban resident activities' spatial characteristics, movement rules and the mutual influence of urban functions' spatial layout and resident activities.More>

2017, 17(2): 106-116.

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Multiple-factor perceived features of traffic quality influencing trip decision

HU Pan, YANG Xiao-guang

Abstract: The traffic quality factors influencing trip decision and their importance were analyzed, ten primary factors were selected, and a basic system of traffic quality factors was constructed according to the need hierarchy model.A model analyzing the structural system of traffic quality factors was established by using the exploratory factor analysis method.The influencing relationships among personal features, cost constrains, trip decision and traffic quality factors were simulated and quantified according to the structural equation model.Using the travel intention survey data in an experimental analysis, a second-order hierarchical structure of traffic quality factors and a path coefficient diagram of structural equation model were established.The comprehensive route coefficient was analyzed to show the impact degrees of traffic quality factors on trip decision, and the numerical features of the importances of traffic quality factors indifferent urban levels were studied.Analysis result shows that the first two factors in the structural system of traffic quality factors explain 84.9% of the total variance, and the factor load coefficients of the two factors all exceed 0.6, which indicates that the structure system of traffic quality factors is rational.The Cronbach'sαand the validity check coefficient of test data are 0.86 and 0.84, respectively, which shows that the test data have good reliability and validity.The total average value of composite validities in structural equation model is 86.9%, and the composite validities of path coefficients all exceed 80%, which shows that the model can adapt to random sample well.According to the importance degrees, the first four factors of traffic quality are successively reliability, velocity, economy and comfort, and the comprehensive path coefficients are 0.78, 0.73, 0.67, 0.60, respectively.Furthermore, the importance degrees of traffic quality factors are different in different urban levels.The most important factor in superlarge city is reliability with a path coefficient 1.44, while the most important factor in small city is comfort with a path coefficient 1.72.Therefore, it will achieve higher efficiency and effectiveness for improving traffic quality when making improving policies according to urban citizens' perceived features of traffic quality factors.More>

2017, 17(2): 117-125.

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Parking pricing method of public parking lots based on multi-aspect comprehensive benefit maximization

WANG Jian-jun, JIN Shu-xin, LI Wei-jia, CHEN Fa-an

Abstract: In order to guarantee the successful investment and operation of public parking lots in later stage, aparking pricing method based on multi-aspect comprehensive benefit maximization was proposed.Considering the interests and needs of parkers, investment managers and public society, parking tolerance price rate, average parking price rate and maximum social benefit parking price rate were worked out by using the data analysis of parking characteristics survey, the cost-profit parking pricing model, and the point elasticity coefficient model, respectively.Parking pricing modes were analyzed.Reasonable compositions and adjustment methods ofparking pricing scheme were made.The impacts of investment and operation benefit by the existing pricing method and proposed method were compared.By studying the single-factor and three-factor sensitivities of later period parking price rate, a relationship model between three factors and parking price rate was proposed, and the influences of combination values of three factors within the different scopes on parking pricing scheme were analyzed.Analysis result shows that the parking price rate of later period is the key factor in parking pricing scheme.When the investment recovery period, commercial space proportion and plot ratio of parking lot change in[-30%, 30%], the fluctuation range of later period parking price rate will be [-50%, 50%].When the fluctuation ranges of commercial space proportion and plot ratio of parking lot are both controlled in [-10%, 10%], the investment recovery period should not be taken too long.When the fluctuation ranges of investment recovery period and plot ratio of parking lot are both controlled in[-10%, 10%], the commercial space proportion should not be taken too small, and the most suitable proportion is 30%.When the fluctuation ranges of investment recovery period and commercial space proportion are both controlled in [-10%, 10%], the plot ratio of parking lot has small influence on the parking price rate of later period.More>

2017, 17(2): 126-135.

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Multi-mode competitiveness game model in regional comprehensive passenger transportation corridor

LIU Shuai, TANG Bo-ming, CHEN Jian

Abstract: In order to study the effect of multi-mode price competition on the market share rates and profits in comprehensive passenger transportation corridor, based on the non-aggregated NL model and the game theory, a bi-matrix game model was build to describe the relationship between market share rate and transportation price of each transportation mode. Taking Chengdu-Chongqing Transportation Channel as an example, the variation characteristics of market competition equilibrium prices and market share rates of two typical modes of high-speed railway and highway bus were studied.Analysis result shows that under the condition of equilibrium price calculated by the bi-matrix game model, the average market share rates of highspeed railway and highway bus increase by 56.15% and 80.58%, respectively, which is beneficial to improve their scale efficiencies.Under the same travel mode structure, the change of timevalue influences operating profit and market share rate. With the increase of time value coefficient, the average operating profit and market share rate of high-speed railway increase by 34.60% and 9.98%, respectively.At the same time, the average operating profit and market share rate of highway bus decrease by 29.70% and 3.49%, respectively.When the highway bus has a disadvantage time value, an appropriate reduction of fare is conducive to increase the operating profit.Therefore, the result computed by the game model is consistent with the actual changing law of passenger transport market in regional comprehensive passenger transportation corridor.It's impossible to pursue the maximum profits through unrestricted price cuts for highspeed railway and highway bus.The operating profits increase first and then decrease, finally reach the maximum operating profits at a certain price.The game model has a price equilibrium solution, and when the external situation changes, the high-speed railway and highway bus would achieve the best profit state through the game model.More>

2017, 17(2): 136-142.

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Path analysis method of driving factors of carbon emissions for Chinese transportation industry

DU Qiang, SUN Qiang, YANG Qi, FENG Xin-yu, YANG Jian

Abstract: The driving factors of carbon emissions for Chinese transportation industry were analyzed, and the path analysis method of carbon emissions' driving factors was proposed based on multi-element regression analysis method.Based on the last two decades' panel data of carbon emissions for Chinese transportation industry, the direct and indirect path coefficients of the factors were computed, and the direct influence degrees of main driving factors and the indirect influence degrees of their interactions were studied.Analysis result shows that economic level, transportation intensity and energy intensity are main influence factors of transportation carbon emissions.The larger the direct path coefficient is, the greaterthe promotion to transportation carbon emissions is.The larger the indirect path coefficient is, the greater the dependence on other factors is.Economic level's direct path coefficient is 1.338, which indicates that economic growth directly stimulates the increase of carbon emissions.The sum of economic level's indirect path coefficients is-0.350, so economic level has little dependence on other two factors but has strong promotion effect.Transportation intensity's direct path coefficient is 0.422, which indicates that transportation intensity increases transportation carbon emissions. The sum of transportation intensity's indirect path coefficients is 1.171, so transportation intensity has strong dependence on economic level, the logistic quantity and logistic cost of unit GDP consumption are higher, and the added value of industry is lower.Energy intensity's direct path coefficient is 0.216, which indicates that energy intensity is an important factor to increase transportation carbon emissions.The sum of energy intensity's indirect coefficients is 0.119, so economic development increases energy consumption, which results in a large amount of carbon dioxide emission, and the high economic and environmental costs results from the higher energy consumption of unit turnover and the lower intensive using degree of energy.More>

2017, 17(2): 143-150.

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Multipath interference suppression algorithm based on spatial signal separation

JIA Qiong-qiong, WU Ren-biao, WANG Wen-yi, LU Dan, WANG Lu

Abstract: Aiming at the multipath interference suppression problem in global navigation satellite system (GNSS), an efficient multipath interference suppression algorithm with low complexity was proposed.Under the unknown directions of arrival (DOAs) of direct signal and multipath interference, the RELAX algorithm was used to estimate the DOAs and amplitudes of direct signal and multipath interference one by one through repeated iteration idea, and then to distinguish multipath interference.The beam forming technology without distortion based on linearly constrained minimum variance (LCMV) was used to form gain at direct signal direction and null at multipath interference direction, and then to suppress multipath interference.The simulation test was carried out.Analysis result shows that when multipath interferences are partially coherent, the root mean square error of DOA estimated by RELAX algorithm is about 12 dB lower than the value estimated by MUSIC algorithm. When multipath interferences are completely coherent, the root mean square error of DOA estimated by RELAX algorithm is about 25 dB lower than the value estimated by MUSIC algorithm.The proposed algorithm can accurately estimate the DOAs of direct signal and multipath interference, which can ensure nulling the multipath interference in airspace through beam forming to make the signal enteringthe tracking loop very clean.The processed tracking error of code phase is close to 0.More>

2017, 17(2): 151-158.

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