2009 Vol. 9, No. 4

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Fractal evaluation of surface texture for coarse aggregate and performance test of asphalt mixture
CHEN Guo-ming, ZHOU Chun-xiu, TAN Yi-qiu
Abstract: Seven kinds of surface textures for coarse aggregates were measured directly by using laser profilometer.The fractal traits of surface textures were analyzed by using structure function method.The roughness, shape and gradient of each surface texture were synthetically evaluated by using characteristic roughness.Finally, the influence of characteristic roughness on the performance of asphalt mixture was inspected.Analysis result indicates that the surface texture of coarse aggregate behaves fractal trait in a definite scope.Characteristic roughness has remarkable linear correlation with the ratio of the dynamic stability to the freeze-thaw tensile strength for asphalt mixture.Its high-temperature rutting resistance, resistance to water damage and low-temperature anti-cracking performance could be improved with the increase of characteristic roughness.More>
2009, 9(4): 1-5. doi: 10.19818/j.cnki.1671-1637.2009.04.001
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Road performances of Sasobit asphalt mixture
JI Jie, RAN Jin, XU Shi-fa
Abstract: The volume parameters of AC-13C asphalt mixtures with different Sasobit contents were analyzed by Marshall test method.The control index was that the porosity of Sasobit asphalt mixture was equal to the porosity of ordinary asphalt mixture (4.5%).The secondary index was that the improvement of dynamic stability for Sasobit asphalt mixture was maximum relative to ordinary asphalt mixture.The optimal compaction temperature and Sasobit content were determined according to the two indices, which were 130 ℃ and 3% respectively.The performances of different AC-13C asphalt mixtures with 3% Sasobit and without Sasobit were compared by rutting test, low-temperature bending-beam test, frost thawing and splitting test, immersion Marshall test respectively, and the influence of Sasobit was analyzed.Analysis result shows that compared with ordinary asphalt mixture, the compaction temperature of Sasobit asphalt mixture decreases by 20 ℃, but its high-temperature stability rises, and its dynamic stability increases by 3 times.Its low-temperature anti-crack ability and moisture stability are lower, but the diminutions are unconspicuous.More>
2009, 9(4): 6-9. doi: 10.19818/j.cnki.1671-1637.2009.04.002
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Fatigue performance of cement-stabilized macadam mixture
WANG Yan, NI Fu-jian, LI Zai-xin
Abstract: According to the stress state of cement-stabilized macadam base under vehicle load, the strength and splitting fatigue tests on the macadam materials with various cement dosages and gradations in doors were carried out.The test result of unconfined compressive strength shows that the 7th day's unconfined compressive strengths of the mixtures with middle-rang gradations and 2.5% cement dosage meet with the requirement of relative criterion, therefore, the cement dosage criterion can be debased properly for cement-stabilized macadam base.The result of splitting fatigue test indicates that the cement-stabilized macadam mixture with higher cement dosage has lower load sensitivity.In other words, under the same construction condition, its capability to endure overload or over-axial-load limit force is better.Based on the result of splitting fatigue test, the fatigue formulae with high correlation coefficients are educed by using regression method, the minimal determinant coefficient is 0.848 3, and the regression parameters values are in 7~88.More>
2009, 9(4): 10-14. doi: 10.19818/j.cnki.1671-1637.2009.04.003
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Vibrating characteristics of skew bridge
XIA Gui-yun, YU Mao-hong, LI Chuan-xi, ZHANG Jian-ren
Abstract: To explore the change rules of vibrating frequencies and gain the rational impact factors of skew bridge, the transcendent equation of vibrating frequency and the finite element formulations of static and dynamic force analysis were derived.The influences of obliquity, supporting manner and the ratio of flexural stiffness to torsion stiffness on the first five order frequencies of single span skew bridge were studied.The vibrating frequencies under different obliquities for a 20 m-length void slab were tested and analyzed.The interaction of vehicle-bridge system for single span skew bridge was studied, and the influences of vehicle velocity and obliquity on the dynamic deflection and dynamic moment were investigated.Calculational result indicates that for skew bridge, obliquity and supporting manner have important influences on dynamical characteristics, the impact effect of vehicle has no harmonious changing rule with vehicle velocity, and the impact factors of deflection and moment are different.More>
2009, 9(4): 15-21. doi: 10.19818/j.cnki.1671-1637.2009.04.004
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Modeling and simulation of frictional coefficient measure vehicle for airport runway
SHI Xu-dong, YANG Peng-fei, WANG Li-wen, LI Jian-li
Abstract: In order to improve the measure accuracy of frictional coefficient for airport runway, the pavement roughness and frictional coefficient measure vehicle of airport runway were modeled and simulated.The power spectral density of pavement and inverse discrete Fourier transformation were introduced to model runway surface roughness as excitation input.Impedance diagram was used to model the hanging system and measuring system of the measure vehicle.The simulation was processed based on the system models.The validity and feasibility are verified by comparing the simulation results with the measured data of the existing measure vehicle.It is indicated that the maximum relative measure error of frictional coefficient reduces from 15.7% to 8.6%, so the measure accuracy is improved by modeling the measure vehicle with impedance diagram.More>
2009, 9(4): 22-27. doi: 10.19818/j.cnki.1671-1637.2009.04.005
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Modeling and simulation of catenary based on negative sag method
ZHOU Ning, LI Rui-ping, ZHANG Wei-hua
Abstract: The model configuration of simple stitched catenary was studied by negative sag method.The initial calculation under the action of tension and gravity was performed to obtain the vertical displacement of the catenary, and the initial model was restructured.Based on the obtained vertical displacement, the negative sag was reserved in advance to ensure the horizon of contact wire under the initial equilibrium state after a series of the calculations of negative sags.Thus, the dropper length, being satisfied with the initial equilibrium equation, was obtained.Furthermore, the model configuration of the catenary was determined, such as the geometry property and stress distribution.Negative sag method was compared with conventional method.It is pointed that the obtained dropper length by negative sag method is slightly longer than that by conventional method, and the maximum relative deviation of the dropper length is 0.75%.For negative sag method, there is small change of the element stress with the various locations of the element.However, for conventional method, the element stress is constant, and the maximum relative deviation of the element stress is 0.55%.The results show excellent agreement with the comparison data.Moreover, it is indicated that with negative sag method, it is easier to implement the subsequent analysis of pantograph-catenary system, and the method is also effective for complicated catenary including multiple spans.More>
2009, 9(4): 28-32. doi: 10.19818/j.cnki.1671-1637.2009.04.006
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Analysis model of vertical vibration for rubber floating slab track
ZOU Jin-hua, JIANG Hai-bo, XIA Xiao-zhou
Abstract: According to the structural vertical vibration characteristics of rubber floating slab track, a composite element dynamic analysis model of track section was established.In the model, Euler beam element with continuous elastic supports was used to simulate steel rail.Floating slab track was taken as elastic thin plate and was discreted by longitudinal and lateral directional finite strip elements.Linear spring and damp were regarded as fastener and rubber support.Based on the principle of total potential energy with stationary value in elastic system dynamics and the "set-in-right-position" rule for formulating system matrices, the total potential energy of vertical vibration of train and track was obtained and the matrix equation of vertical vibration was established to analyze the vibration properties.Analysis result indicates that the maximum reduction rate of wheel load is 0.597, the maximum vibration acceleration of car body is 0.846 m·s-2 and the vibration isolation efficiency of the track system is between 20% and 27%.Obviously, the vertical model accurately describes the dynamic response properties of vehicle and track.More>
2009, 9(4): 33-37. doi: 10.19818/j.cnki.1671-1637.2009.04.007
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Pile-soil interacton properties of pile-plank embankment
ZHAN Yong-xiang, JIANG Guan-lu
Abstract: In order to investigate the mechanical behavior of pile-plank embankment for high-speed ballastless track under moving load, based on Suining-Chongqing High-speed Railway, the pile-soil interaction characteristics of pile-plank embankment were researched by indoor great scale dynamic model test, in which the loading frequency is 5 Hz and the loading times are 2×105.Test result indicates that the amplitude of dynamic displacement, pile shaft force, dynamic stress in soil between piles remain constant after 1×104 times of vibrant loading, and pile-soil interaction tends toward stability.The amplitude curve of dynamic stress is approximately "K" form with the depth in soil between piles, piles share most dynamic stress compared with soil, and dynamic stress is affected by loading position.Pile structure expands the depth of the dynamic response of roadbed and improves the stress state of roadbed soil.More>
2009, 9(4): 38-42. doi: 10.19818/j.cnki.1671-1637.2009.04.008
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Nonlinear structure design of heavy haul vehicle
YAO Shu-guang, TIAN Hong-qi
Abstract: Based on material nonlinear theory and local plastic deformation being allowed, structure lightweight design were carried out in order to relieve the mass and increase the load-carrying capacity for heavy haul railway vehicle, which was made of high strength low-alloy steel with strengthening characteristic.The optimization measures to weaken the end-wall and strengthen under-frame structure were taken.Furthermore, the nonlinear stability analysis of the lightening structure was put up using geometric nonlinear theory, and was used to develope an optimization new-type 40 t-axle-load heavy haul gondola car whose total mass is 160 t.Under longitudinal compress load case, the maximum stress is 336 MPa, which is less than the yield stress 450 MPa of Q450NQR1 material, and the critical load of local buckling occurrence is 6 252 kN.Under longitudinal impact load case, some stresses are about 530 MPa located on top side cant and end cant, which are below the limited stress 550 MPa, and the stresses on under-frame are more uniformity than that before the optimization.The strength, stiffness and stability of the car meet the demand of AAR criterion, and the deadweight coefficient is only 0.16.The result shows that nonlinear analysis method is a valid instrument of lightweight design of heavy haul vehicle.More>
2009, 9(4): 43-48. doi: 10.19818/j.cnki.1671-1637.2009.04.009
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Temperature-rising laws of drum brake pad for truck on long downgrades
HU Chang-bin, SHEN Jin-rong, CHEN You-jie
Abstract: The Zhongxinkeng and Xiaochiling Sections on Longyan G319 of Fujian Province were chosen as test sections, which are typical accident black spots.The test plan with concrete vehicle was designd on long downgrades.Based on the finite element analysis about test data, the temperature-rising laws of brake pad under different conditions, such as different gross masses of truck, brake modes, cooling methods, were analyzed.The result indicates that when truck runs downhill, the temperature of the pad increases wavelike with the implementation of braking behavior.The gross mass, the functional performance of brake pad and road linetype combination are the key influence factors on the temperature change of brake pad.The temperature is decreased by engine brake at low gear and sprayed brake effectively.The braking behavior is closely related with road conditions and linetype combination.The simulation result of temperature field with finite element method in simple state is quite different from the result of vehicle test.More>
2009, 9(4): 49-55. doi: 10.19818/j.cnki.1671-1637.2009.04.010
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Fractal features of size-distributions of truck transportation hubs in China
YAO Zhi-gang, ZHOU Wei, WANG Yuan-qing
Abstract: In order to quantitatively evaluate the system topology of Chinese truck transportation hubs in recent years, highway freight volume was regarded as a size index of truck transportation hub.A novel formula for exactly calculating the fractal dimension of size-distribution of the truck transportation hub was presented.The fractal dimensions of size-distributions of 200 largest truck transportation hubs during 1997~2007 were calculated by the formula based on the statistical data of highway freight volumes.Computation result shows that the size-distributions of truck transportation hubs during 1997~1999 are bi-fractal, while that are single fractal and the fractal dimensions are between 1.464 6 and 1.570 1 during 2000~2007, and the size-distribution of truck transportation hub system is adapted to city system.The evolvement of the fractal topology from bi-fractal to single fractal indicates a rational evolutionary progress of size-distributions of truck transportation hubs, and large truck transportation hubs should be supported to optimize the structure of truck transportation hub system.More>
2009, 9(4): 56-60. doi: 10.19818/j.cnki.1671-1637.2009.04.011
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Travel mode choice model with multiple attributes based on interval number
XIE Bing-lei, MAO Ke-jun, HU Xiao-ming
Abstract: The uncertainty of travel information was described by using interval numbers, and a travel mode choice model with multiple attributes was put forward.The least-square method based on complementary judgment matrix was used to obtain the weights of different travel modes, the weight of each attribute variable was computed based on a dispersion maximization model, and the composite weight of each travel mode was obtained.The efficiency of the choice model was validated according to car and public transit travel samples.Analysis result shows that car is usually chosen when its travel weight exceeds 0.65, and public transit is usually chosen when its travel weight exceeds 0.68, so the model can simulate the travel mode choices of travelers effectively.More>
2009, 9(4): 61-64. doi: 10.19818/j.cnki.1671-1637.2009.04.012
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Evaluation model of satisfaction degree for urban public transit service
WU Rong-zhen, ZHAI Dong-dong, XI En-chong, LI Li
Abstract: In order to improve the service level of urban public transit system, the specificity of public transit service and the subjective psychological characteristic of passenger satisfaction degree evaluation were analyzed, and the evaluation index system was established.The gradations and comprehensive characteristics of the evaluation indexes were studied by using analytic hierarchy process (AHP) and scale method, and a satisfaction degree evaluation model was proposed based on fuzzy comprehensive evaluation method.The public transit satisfaction degree in Xianyang was evaluated comprehensively.Evaluation result indicates that the satisfaction degree obtained by the evaluation model is 6.16, and is approximate with 7.55 got by field survey, which is at the level between more and most satisfaction.Computation result reflects the subjective attitudes of passengers accurately and visually, so the evaluation model is rational and effective.More>
2009, 9(4): 65-70. doi: 10.19818/j.cnki.1671-1637.2009.04.013
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Ant colony algorithm of vehicle scheduling problem with time windows
YANG Ren-fa, GONG Yan-cheng
Abstract: In order to solve vehicle scheduling problem with time windows for distribution centers, time window constraint was transformed into penalty function based on ant colony algorithm, and penalty function was added to objective function.A vehicle routing model based on minimum transportation cost was built up to meet the customer requirements of delivery times, its solving program was designed, and a simulation example was studied.Analysis result indicates that the model can be transformed into traveling salesman problem (TSP) model and vehicle scheduling problem (VSP) model with hard-time window or soft-time window through different parameter calibrations.The optimal driving distance is 794 km, and the longest vehicle diving time is 8.2 h in the simulation example, so the ant colony algorithm can effectively solve the scheduling problems of distribution centers.More>
2009, 9(4): 71-74. doi: 10.19818/j.cnki.1671-1637.2009.04.014
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Analysis of traffic accident characteristic on continuous long downgrade section
CHEN Bin, YUAN Wei, FU Rui, GUO Ying-shi
Abstract: Based on the investigation of traffic accident data and road design parameters of continuous long downgrade sections, the traffic safety situations of the sections were analyzed, and the traffic accident characteristics and reasons of sharp curve-steep downgrade section, continuous steep downgrade section and continuous gentle downgrade section were discussed.According to the relative data of typical sections, the relationship between traffic accidents and road vertical section parameters was studied based on statistics and regression methods.Analysis result indicates that the traffic accident rate is highest when the grade value of continuous long downgrade section is in the range of 3% to 4%.It has clear exponential relationship between the accident rate and average gradient of the section in front of more than 2 km at accident spot, and the determinant coefficient of regression model is more than 0.84.More>
2009, 9(4): 75-78. doi: 10.19818/j.cnki.1671-1637.2009.04.015
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Synthesized evaluation model of dynamic traffic safety for road section
LIAO Jun, AN Yi-sheng, ZHANG Shao-yang, ZHAO Xiang-mo, MA Tian-shan
Abstract: Aiming at the various, heterogeneous, dynamic characteristics of the synthesized evaluation data for road traffic safety in the integration project of traffic information, an evaluation model of dynamic traffic safety for road section was proposed based on information fusion.The influence factors, such as people, vehicle, highway and environment, on traffic safety were analyzed.The sizes and frequencies of the data sets used in the evaluation model were determined.Factor data correlated with traffic safety were automatically fetched from business database.The evaluation matrix of each factor was generated based on the classifying rules.The safety evaluation was made based on the maximum subordination value calculated by fuzzy comprehensive evaluation formula.The safety evaluation result of Yangling Road Section on Xi'an-Baoji Highway shows that the calculated maximum subordination value is 0.265, which indicates the safety state of the section is safer.Moreover, the factors, such as overspeed, overload, tyre burst and rainy weather, have lower evaluation values.The results are consistent with the statistical data of traffic accidents in the road section.More>
2009, 9(4): 79-84. doi: 10.19818/j.cnki.1671-1637.2009.04.016
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Safety evaluation of road alignment based on energy conservation law
ZHANG Wei, WEI Lang, PENG Shao-yong
Abstract: In order to estimate the influences of horizontal and vertical alignments on the safety of high classified highway in mountain area, based on energy conservation law, the influences of longitudinal gradient, gradient length and horizontal curve radius on the temperature rise of brake system were analyzed when vehicle ran downhill.Taking example for a downhill section in mountain area, the relationship between highway alignments and accident rates was validated.Analysis result indicates that when vehicle runs stably the critical gradient increases with the increases of transmission ratio and vehicle speed.Highway safety decreases with the increase of the product between average gradient and gradient length.Because the lesser curve radius can enhance the ability of engine brake, highway safety is improved.The larger mean square error of curve radius may increase the use frequency of vehicle brake, therefore, highway safety will be reduced.More>
2009, 9(4): 85-91. doi: 10.19818/j.cnki.1671-1637.2009.04.017
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Institutional evolution mechanism of shipping organization based on transaction cost
CHEN Ji-hong, ZHEN Hong, ZONG Bei-hua
Abstract: In order to analyze the institutional evolution process of international shipping organization, four kinds of typical forms, such as liner conference, discussion agreement, consortium, strategic alliance, and the evolution mechanism of international shipping organization were studied.Two institutional patterns of induced change and mandatory change for shipping organizations were compared based on transaction cost theory.Analysis result indicates that transaction costs exist in the processes of formulation and change of shipping organization.Cost margin, friction cost as well as opportunity cost are the specific forms of transaction cost in its evolution process.Because of transaction costs, shipping organization institution is non-equilibrium, and its development involves a changing and non-equilibrium process.More>
2009, 9(4): 92-97. doi: 10.19818/j.cnki.1671-1637.2009.04.018
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Modeling and property analysis of operation scheduling problem at container terminal
LU Zhi-qiang, LIANG Liang
Abstract: In order to improve the operation efficiency at container terminal, the operation characters of handling system were studied.A disjunctive graph model for the integrated scheduling problem of container handling system was built by extending traditional disjunctive graph.Based on the disjunctive model, blocking and dead lock existing in container terminal operation were analyzed.Two kinds of dead locks were defined, and their judging methods were put forward.Analysis result shows that two kinds of dead locks can be distinguished effectively by reverting the disjunctive graph, and based on the properties of blocking and parallel machine sets, the feasible solution of the scheduling problem can also be obtained on the disjunctive graph.More>
2009, 9(4): 98-102. doi: 10.19818/j.cnki.1671-1637.2009.04.019
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Optimal model and algorithm for container loading of airfreight forwarder
GUI Yun-miao, GONG Ben-gang, ZHU Jin-fu
Abstract: In order to improve the profit and container loading ability of airfreight forwarder, air cargo loading problem was divided into cargo choosing problem and choice cargo loading problem through analyzing air cargo pricing system.A profit-maximized air cargo choosing model was developed, and an evaluated rank-based choice cargo loading algorithm was presented by means of whole-fill, space division and mergence under the constraint that the same waybill cargos were at adjacent loading position.Computation result shows that the optimal model can choose loading cargos rationally, and the average utilization ratio of container volume achieves 83% by using the proposed optimal algorithm, so the profit of airfreight forwarder and the practical requirement of container loading can be satisfied effectively.More>
2009, 9(4): 103-107. doi: 10.19818/j.cnki.1671-1637.2009.04.020
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Transportation economic accounting based on transportation satellite account
YUAN Zhang-wei, WANG Jian-wei, LU: Ying-ping
Abstract: In order to take a comprehensive and detailed transportation economic accounting, Chinese current economic accounting system was analysed.Referring foreign transportation economic accounting models and based on input-output law, a transportation satellite account was set up by expanding the existing national accounts.The satellite account includes use-table, direct demand coefficient table and total demand coefficient table, and each table includes 49 kinds of goods sectors.Its accounting indexes includes producing accounting index and input-output accounting index.Finally, the sources of self-transportation data were analyzed, and the transportation economic accounting of Province J was done by using transportation satellite account.The result shows that the transportation added value rises from 306 million yuan to 424 million yuan, the proportion of transportation economy to GDP increases from 3.6% to 5.1%.Obviously, when transportation satellite account is used to account transportation economy, transportation outputs and the organic relationship between national economy and transportation can be evaluated accurately, transportation production can be allocated into national economy departments effectively.More>
2009, 9(4): 108-113. doi: 10.19818/j.cnki.1671-1637.2009.04.021
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Attention assignment characteristic of driver and its influences on driving safety
MA Yan-li, WANG Yao-wu
Abstract: The method of experimental psychology and the way of comparative analysis were used.The attention assignment characteristics of drivers were measured by attention assignment instrument, and the threshold value of attention assignment indicator was determined.The variations of driver attention assignment characteristics were studied in different periods of driving times.The relational model between continuous driving time and attention assignment indicator was established.The influence of attention assignment characteristics on driving safety was analyzed.Analysis result shows that there is a corresponding relation between the attention assignment data of drivers and accident numbers.Attention assignment characteristics have no significant difference between men and women.With the increase of age, the value of attention assignment characteristic decreases significantly.There is a negative correlation between the value of attention assignment and continuous driving time.Then the indicator of attention assignment can be used to appraise diving ability and determine safe driving time.More>
2009, 9(4): 114-117. doi: 10.19818/j.cnki.1671-1637.2009.04.022
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Locating algorithm of driver lip feature points based on machine vision
SHENG Jing
Abstract: In order to monitor driver fatigue state effectively, its dynamic threshold was determined by using edge-detection method and red color element point extraction method, lip was segmented and extracted in colorful face images.Each feature point of lip was located based on approximation algorithm.The movement of lip was monitored, and the state of driver fatigue was determined based on machine vision.Test result indicates that the locating algorithm can dislodge the interferences around lip effectively, pick up lip shape from original image completely, and locate the feature points of lip exactly.The algorithm has good robustness for the situations of different skin colors, different lights and different rotational angles of head.More>
2009, 9(4): 118-121. doi: 10.19818/j.cnki.1671-1637.2009.04.023
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Optimization technology of configuration for reflecting film in guide sign
HUANG Kai, HE Yong, TANG Jian-juan, HAN Wen-yuan
Abstract: The relationship between eyesight and the brightness ratio of word and background was analyzed, and the influences of colors' hue, saturation and brightness on colors' visibility were studied based on psychological theories.The influences of retro-reflective coefficient grades on visibility were researched based on field experiments, and the relation model between retro-reflective coefficient and visibility distance was established.Analysis result shows that there is a certain brightness ratio which can make the visibility best, and the visibility of white word on blue background is better than that of white word on green background.The best configuration of word and background for reflecting film is that the retro-reflective coefficient of word is 600 cd·lx-1·m-2, that of background is 92.5 cd·lx-1·m-2, and the corresponding visibility distance is 141.9 m.Analysis result indicates that the current grade of guide sign is higher and should be lowered.More>
2009, 9(4): 122-126. doi: 10.19818/j.cnki.1671-1637.2009.04.024
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