2019 Vol. 19, No. 1

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Effect of high temperature and heavy load on deformation resistance of DCLR modified asphalt mixture
JI Jie, CHEN Lei, SUO Zhi, XU Ying, HAN Yan-long
Abstract: To evaluate the deformation resistance of coal direct liquefaction residue (DCLR) modified asphalt mixture and compound DCLR modified asphalt mixture under high temperature and heavy load, the tri-axial repeated load test was carried out on two asphalt mixtures with the gradation of AC-20 under multi-temperatures (50 ℃, 60 ℃, 70 ℃) and multi-loads (0.7, 0.8, 0.9, 1.0 MPa) conditions, and the test data were nonlinearly fitted. An index for evaluating the deformation resistances of the two asphalt mixtures under high temperature and heavy load was proposed, and the variance analysis method was used to investigate the significant influences of temperature and load on the deformation resistance of asphalt mixture. Research result shows that the permanent deformations of two asphalt mixtures increase as temperature and load increase. The flow number and nonlinear fitting index have negative and positive correlation with temperature and load, respectively, indicating that both nonlinear fitting index and flow number can reflect the deformation resistance of asphalt mixture. However, the flow number three-dimensional surfaces of the two asphalt mixtures have intersects when temperature varies from 65 ℃ to 70 ℃ and load is 1.0 MPa, demonstrating that flow number cannot effectively distinguish the deformation resistances of DCLR modified asphalt mixture and compound DCLR modified asphalt mixture under high temperature and heavy load. The sensitivity of two asphalt mixtures to temperature is higher than to load at a significant level of 0.05. Therefore, temperature is the main factor that affects the deformation resistances of the two asphalt mixtures, and load is the secondary factor. The nonlinear fitting index and flow number of temperature and load have significant influences on the deformation resistances of two asphalt mixtures when the significant levels are 0.013 and 0.113, respectively, reporting that the nonlinear fitting index is more suitable than the flow number for evaluating the deformation resistances of DCLR modified asphalt mixture and compound DCLR modified asphalt mixture within test temperature and load conditions.More>
2019, 19(1): 1-8. doi: 10.19818/j.cnki.1671-1637.2019.01.001
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Runoff characteristics for straightline segment asphalt pavement based on two-dimensional shallow water equations
GENG Yan-fen, CHEN Xian-hua, CHEN Yue, MA Yao-lu, HUANG Xiao-ming
Abstract: Based on the hydrodynamic method of two-dimensional shallow water equations, a numerical model of straightline segment asphalt pavement runoff was proposed. According to the monitoring result of asphalt pavement runoff variation under the actual rainfall conditions, the model parameters were validated. The influences of geometric parameters such as the pavement width, slope combination, and drainage method on the temporal and spatial variations in the pavement runoff were analyzed. Research result shows that under the designed rainfall conditions, the pavement runoff exhibits strong two-dimensional characteristics in the spatial distribution. The runoff depth variation process includes the increasing period, steady-state runoff and retreat. Under the condition of decentralized drainage, when the pavement width is 11, 15, 20, 25 and 30 m, respectively, the maximum pavement runoff depth is 11.87, 14.39, 17.08, 19.69 and 21.98 mm, respectively, and the retreat time is 1.4, 1.4, 2.4, 2.9 and 3.4 min, correspondingly. The increment of pavement runoff depth decreases as the pavement width increases. The retreat time of pavement runoff increases with the addition of pavement width. Comparing with the carriageway, the retreat time in shoulder area increases by approximately 20%. A larger slope combination (the cross slope is 3% and the longitudinal slope is 2%) is beneficial to the drainage. When adopting the central drainage, the block of curbs leads to the formation of backwater on the roadside. The width of backwater area is 6-8 m, and its proportion decreases with the increase of pavement width. In the no-backwater area, the pavement runoff depth shows a similar change to that when using the decentralized drainage. To ensure the driving safety, a reasonable pavement slope should be set to reduce the confluence time of pavement runoff. The blocking effect of curbs on the pavement runoff is obvious, thus, the height of curbs and outlets interval should be set reasonably in the drainage design to avoid the formation of backwater in the carriageway.More>
2019, 19(1): 9-16. doi: 10.19818/j.cnki.1671-1637.2019.01.002
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Application of bilinear cohesive zone model in damage and cracking analysis of concrete pavement
ZHOU Zheng-feng, PU Zhuo-heng, TANG Ji-hua
Abstract: In order to reveal the damage and cracking mechanisms and their impact on the bearing capacity of concrete pavement, the elasticity and plasticity of concrete material were considered. By using the bilinear cohesive zone model in non-linear fracture mechanics, the cohesive elements were inserted into the potential path of crack propagation based on ABAQUS finite element software, and the whole process from elastic response to damage failure was modeled for a four-point loading beam. The reliability of bilinear cohesive zone model for the analysis of concrete damage and cracking was verified. By using the bilinear cohesive zone model, the cracking characteristics and the decrease of bearing capacity after the initial damage of a concrete slab on Winkler foundation were analyzed as well. Analysis result indicates that under the entire process of loading, the stresses at the bottom of the beam experience the phases of increasing linearly, decreasing after reaching the concrete flexural strength, the maximum stress point moving upwards, and reducing to 0. The load-displacement relationship on the beam is in accordance to the existing results. For the concrete slab under the entire process of loading, the variations of stress distribution at the section are similar to those of the beam. The bearing capacity of concrete slab increases continuously, but for its supporting condition is different from that of the beam. The failure of concrete slab appears to be brittle, and shows no obvious decay. The ratio of the ultimate bearing capacity to the critical bearing capacity at the elastic phase is 1.32. Once the initial damage of concrete slab occurs, the ultimate bearing capacity will decrease at most to 87% of undamaged slab. The decay rate of ultimate bearing capacity increases with the degree of initial damage.More>
2019, 19(1): 17-23. doi: 10.19818/j.cnki.1671-1637.2019.01.003
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Effect of acid environment on swelling-shrinkage properties of Baise expansive soil and its microscopic interpretation
CHANG Jin, YANG He-ping, XIAO Jie, LIU Xiong, CHEN Guan-yi, MAO Rui
Abstract: The Baise expansive soil in heavy acid rain area of Guangxi was selected as the study subject. To explore the effect of acid rain on the swelling-shrinkage properties of Baise expansive soil, the load-free swelling rate test, swelling force test and linear shrinkage rate test were carried out under different acid conditions (pH values are 3, 5 and 7, respectively). The changes in the microstructure and mineral composition of expansive soil were analyzed through the scanning electron microscopy (SEM) images and X-ray diffraction (XRD) patterns, the microstructures of specimens in SEM images were quantitatively analyzed based on the image processing software Image-Pro Plus (IPP). Research result shows that with the decrease of initial water content, the effect of acid environment on the expansive deformation of specimen increases. When the initial water content decreases from 17% to 9%, the differences of load-free swelling rate between the specimens under different acid environments increase. Comparing with the neutral solution, the increasing ranges of specimen load-free swelling rates soaked in acid solutions with pH values of 3 and 5 grow from 20.6% and 5.6% to 26.9% and 7.0%, respectively. With the decrease of solution pH value, the load-free swelling rates, swelling forces and linear shrinkage rates of specimens increase by stages. Comparing with the neutral solution, the measured load-free swelling rate, swelling force and linear shrinkage rate of specimen soaked in a solution with pH value of 3 increase by 24.3%, 37.5% and 16.9%, respectively. The more acidic the environment, the faster the water evaporation in specimen, and the lower the water content in specimen when it is dehumidified to stable. Both the pore number and size of acid-eroded soil increase with the increase of acidity. The soil porosity increases from 8.7% to 11.9% and 19.4%, respectively, when the solution pH value decreases from 7 to 5 and 3, respectively. The rapid increase of porosity mainly focuses on pore diameter ranging from 3-5 μm. The acid environment decreases the degree of mineral crystallization. Among them, the free colloidal minerals, such as SiO2, Al2O3, K2O, MgO and CaO, show different degrees of erosion and leaching. The erosion of colloidal mineral weakens the structural connection strength between the stacking structures, resulting in the evolution of stacking structure from face-to-face to edge-to-edge. The more acidic the environment, the severer the evolutionary trend, which directly leads to an increase of the swelling-shrinkage deformation of expansive soil.More>
2019, 19(1): 24-32. doi: 10.19818/j.cnki.1671-1637.2019.01.004
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Characteristics of temperature field of airfield runway permafrost subgrade in Qinghai-Tibetan Plateau
QI Chun-xiang, LI Yao, YANG Jian, ZHANG Xian-min, CHENG Guo-yong
Abstract: The temperature fields of airfield runway subgrade and road subgrade in the permafrost region of Qinghai-Tibetan Plateau were compared. The subgrade temperature distributions, the temperature variations along depth, as well as the maximum melting depths of subgrades were analyzed. The subgrade temperature field characteristics of wide airfield runway of asphalt concrete pavement were studied. The subgrade temperature distributions, the subgrade temperature variations along depth at different times and the maximum melting depths of middle and shoulder of runway under different pavement width conditions were compared. The expression of subgrade melting depth of airfield runway of asphalt concrete pavement was obtained based on the pavement width and time. Analysis result indicates that there are obvious differences between the temperature fields of airfield runway subgrade and road subgrade in the permafrost region. The subgrade melt nuclear of airfield runway is lower in position, and it is all below the natural ground, as well as the subgrade melt nuclear of road is higher in position. The melt nuclears are all located in the embankment by raising the embankment, which facilitates the construction of temperature control measures like ventilation duct. It shows that because airfield runway has the characteristics like no embankment and wider pavement, the existing research results of road and railway construction in the permafrost region can not be fully applied to airfield runway construction. For the airfield runway permafrost subgrade of asphalt concrete pavement, as the width of pavement increases, the subgrade stability decreases. When the pavement width increases by 1%, the subgrade isotherm of 0 ℃ decreases by 0.17%, the highest temperature of subgrade melt nuclear increases by about 0.46%, and the subgrade melting depth of middle of runway increases by about 0.19%. But when the width of pavement exceeds 35 m, the subgrade melting depth of middle of runway tends to be stable. Compared with the temperature field of middle of runway subgrade, the shoulder is less affected by pavement width, when the width of pavement exceeds 25 m, its subgrade melting depth tends to be stable. The correlation coefficient of expression of subgrade melting depth of middle of runway is 0.988 6, and the relative error is less than 1%.More>
2019, 19(1): 33-47. doi: 10.19818/j.cnki.1671-1637.2019.01.005
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Bending performance of circle tubular up-flange steel and concrete composite girder with concrete flange
DUAN Lan, WANG Chun-sheng, ZHU Jing-wei, ZHAI Xiao-liang
Abstract: The different loading methods and widths of bottom flange were considered, the bending behavior experiments were conducted for 3 circle tubular up-flange steel and concrete composite girders with concrete flange, and their bending performances and failure modes were analyzed. Based on the bending characteristics of test girders, the simplified formulas of yielding moment and ultimate moment of composite girder were derived. Research result shows that all test girders fail in typically plastic bending mode and have satisfied stability. When attaining the ultimate capacity, the measured slips between the upper flange steel tube and concrete flange are no more than 0.43 mm at the beam ends, which shows the excellent overall working ability for the test beams. The stiffness and bending capacity of test girder increase with increasing the width of bottom flange. The width of bottom flange is 150, 260, and 300 mm, respectively, the corresponding ratio of yield moments is 1∶ 1.44∶ 1.55, and the ratio of ultimate bending capacities is 1∶ 1.31∶ 1.40. With the bending moment of test girder increasing, when the plastic neutral axis rises to the concrete flange, the concrete filled steel tubular flange is in tension, and the confinement effect between the steel tube and inner filled concrete may be neglected. When the plastic neutral axis locates in the up-flange concrete filled steel tube, the confinement effect between the steel tube and inner filled concrete may be neglected in the calculation of ultimate bending capacity, but it may enhance the ductility of test girder. The displacement ductility coefficients of test girders are all greater than 3.35, therefore, the test girders have good ductility. The ratios of theoretical to experimental values of yield bending moment and ultimate bending moment are between 1.02 and 1.04, and between 0.96 and 1.03, respectively, which shows good agreement between the theoretical calculation results and test results. Thus, the simplified theoretical formulas are simple and reliable.More>
2019, 19(1): 48-59. doi: 10.19818/j.cnki.1671-1637.2019.01.006
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String debonding effect of curved RC member reinforced by bonding FRP in intrados
REN Wei, GUO Lin, YANG Yang, ZHANG De-qiang
Abstract: The bonding tests of FRP (fiber reinforced polymer/plastic)-concrete interfaces of 26 curved surface specimens were executed, and the influences of concrete strength, FRP bonding layer numbers, FRP bonding length, and component curvatures on the adhesive strength, interface strain and failure mechanism were investigated. Research result shows that there are three kinds of failure modes in curved concrete members, including the string peeling, FRP fracture at the crack, FRP peeling on the crack side. The greater the curvature of the component, the more likely the string peeling will occur. FRP tensile failure often occurs in small curvature members. With the increase of external load, the peak value of FRP strain has a backward transfer process. It is shown that the FRP along the fiber length is not all involved in the work, and there is an effective working (bonding) length. The analysis result of the test data by the virtual zero point method shows that the effective length of FRP pasted on curved concrete members is about 14 cm. The curvature has a significant effect on the adhesive strength. With the increase of the curvature, the changing gradient of the fiber strain increases, the effective adhesive length becomes shorter, and the adhesive strength decreases. When the curvature is the same, the more the number of fiber layers, the more uniform the strain distribution along the fiber direction and the higher the adhesive strength. But this increase is not linear with the number of FRP layers, and the adhesive strength with two layers of fiber is about 1.5 times of that with one layer. When the number of fiber layers increases, the normal stress of the adhesive layer increases rapidly, and the specimens are more prone to string-debonding failure. This failure is caused by the coupling effect between the normal bonding stress and in-plane shear stress. The stress function of the pasting layer can be expressed by the cosine function of the center angle of internal arc curvature. When the vector height is 30, 60, and 90 mm, the average error of the component is 7.7%, 2.4%, and 8.8%, therefore, the function has higher accuracy.More>
2019, 19(1): 60-70. doi: 10.19818/j.cnki.1671-1637.2019.01.007
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Effect of sand liquefaction on mechanical properties of pile foundation under strong earthquake
FENG Zhong-ju, WANG Xi-qing, LI Xiao-xiong, HU Ming-hua, YUAN Feng-bin, YIN Hong-hua, DONG Yun-xiu
Abstract: In order to improve the seismic resistance behavior of bridge pile foundation located at the liquefied layer, the shaking table model test with three directions and six degrees of freedom was carried out, the dynamic responses of pile tops' horizontal displacements and piles' accelerations and bending moments were analyzed under the seismic waves, and the damages of pile foundations under the actions of seismic waves were studied. Experiment result shows that, under the actions of seismic waves, the lateral expansion effect gradually decreases with the increase of the depth of liquified layer. Therefore, the peak horizontal displacement of pile top gradually decreases. However, the peak horizontal displacement of pile top will no longer be affected by the liquefied layer depth when the seismic acceleration exceeds 0.6g. The pile accelerations increase significantly in the fine sand layer because of the liquefaction of fine sand layer under the seismic loads. The stress caused by the overburden soil can enhance the shear strength of lower layer, therefore, the amplification factor of pile top increases as the depth of liquefied layer increases. Moreover, the amplification factor is the largest under the action of Kobe wave, and the smallest under the action of 5002 wave. The sand liquefaction also causes the strength of soil layer to decrease, leading to the acceleration magnification in the soil layer. All the maximum bending moments of piles appear at the boundary between the liquefied layer and non-liquefied layer, and under the same seismic intensity, the maximum bending moment of pile increases with the increase of liquefaction layer depth. When the seismic acceleration increases from 0.30g to 0.35g, the bending moment of pile shows a maximum increase of 33.3%. The pile foundations experience no difference in the damages caused by different types of seismic waves. Under the acceleration of 0.35g, the fundamental frequency of pile foundation has no change. But when the seismic wave strength exceeds 0.40g, the fundamental frequency of pile foundation suddenly drops from 1.65 Hz to 0.45 Hz. The pile foundations in the sand layer laterally displace due to the liquefaction, and the piles deform due to the shear stress, eventually leading to the damages of pile foundations. In conclusion, when the liquefied layer is relatively shallow, the excessive horizontal displacements of pile tops under the actions of seismic waves should be fully considered. In the seismic design of pile foundation, the bending resistance of pile foundation at the boundary between the liquefied and non-liquefied layer, and the liquefied layer depth must be considered.More>
2019, 19(1): 71-84. doi: 10.19818/j.cnki.1671-1637.2019.01.008
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Influence rule of dynamic stress of high-speed train gearbox housing
WANG Wen-jing, LI Guang-quan, HAN Jun-chen, LI Qiu-ze
Abstract: The influence rules of running speed, line condition and wheel profiling on the dynamic stress of gearbox housing were studied based on the line test, and the change rule of dynamic stress of gearbox housing was analyzed combined with the vibration acceleration of axle box. Analysis result shows that the amplitude spectrums of dynamic stress of gearbox housing and the vertical acceleration of axle box are the same, and the main frequency is 570 Hz, which reflects that the dynamic stress level of the housing is closely related to the high frequency excitation caused by wheel-rail interaction. When the train running speed increases from 200 km·h-1 to 300 km·h-1, the stress amplitude of gearbox housing shows an increasing trend, especially in the tooth surface inspection hole of cracking housing. The equivalent stress increases from 5.56 MPa to 16.67 MPa, which is about 2 times larger. The irregularity caused by the rail wear has a great influence on the vibration of axle box and gearbox housing. When the train is running from worn line to grinding line, the vibration amplitude level of axle box in high frequency stage obviously reduces, and the equivalent stress of key point of the housing reduces from 16.26 MPa to 10.16 MPa, which decreases by 38%. The high frequency (550-650 Hz) excitation caused by the high-order polygon of the wheel at high speed (300 km·h-1) causes the high frequency vibration, the dynamic stress and equivalent stress of the housing increase substantially, and the equivalent stress of key point of the housing decreases from 17.45 MPa to 8.56 MPa before and after wheel profiling, which decreases by 51%. So rail grinding and wheel profiling can improve the stress state of gearbox housing. Therefore, reasonable rail grinding and wheel profiling cycle can effectively prolong the fatigue life of gearbox housing.More>
2019, 19(1): 85-95. doi: 10.19818/j.cnki.1671-1637.2019.01.009
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Dynamic interaction between metro vehicle and steel spring floating slab track under emergency braking condition
LU Chen-xu, SHI Jin, DUAN Qi-yan, WEN Jun-yi
Abstract: To optimize the design of steel spring floating slab track on the grade, based on the consideration of longitudinal wheel-rail relationship and structure characteristics of steel spring floating slab track, the dynamic interaction model of metro vehicle and steel spring floating slab track under the emergency braking condition was established through the multi-body dynamics theory and finite element method. The validity of the model was verified through the multi-body dynamics software UM. The dynamic responses of vehicle and track under the emergency braking condition were analyzed. Research result shows that the average relative errors of longitudinal acceleration of car body and longitudinal wheel-rail force calculated by the UM and the model in this paper are 1.3% and 2.8%, respectively. During the emergency braking process, the car body is always in the state of forward pitching and longitudinal vibration, resulting in the increased load in the front wheel and the decreased load in the rear wheel. Owing to the discontinuities between the slabs, a longitudinal relative dislocation occurs between the track and floating slab. The special attentions should be paid to the longitudinal uncoordinated deformation between the rail and floating slab. For the scheme of arranging a pair of isolators at the intervals of two sets of fasteners (scheme 1), the vertical displacement of rail at the end of slab is 0.2 mm larger than that at the middle of slab. For the scheme of arranging a pair of isolators at the intervals of two sets of fasteners, then arranging a pair of isolators at the intervals of three sets of fasteners (scheme 2), the vertical displacement of rail at the end of slab is 0.5 mm smaller than that at the middle of slab. Under the two layout schemes, the difference of longitudinal deformation of track is no more than 5%, and the difference of longitudinal force acting on fastener and steel spring is no more than 15%. The short wave track irregularity significantly increases the vertical vibrations of rail and floating slab, and the maximum vertical acceleration of rail can reach up to approximately 15g in the presence of track irregularity. Steel spring floating slab can reduce the vertical vibration transmitted to the bottom of the foundation, and the acceleration decreases by approximately 0.2 m·s-2. However, the low-frequency vertical vibrations of rail and floating slab amplify significantly, and the vibration increases by approximately 15 dB.More>
2019, 19(1): 96-107. doi: 10.19818/j.cnki.1671-1637.2019.01.010
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Influence of air supply form on contaminat diffusion of bleed air in aircraft cabin
YANG Jian-zhong, MA Bo-wen, CHEN Xi-yuan, WANG Zhen-bin
Abstract: The co-simulation method was adopted to realize the adjustment of aircraft environmental control system to cabin environment. The closed-loop simulation model of aircraft environmental control system to cabin environment was established. The effects of different air supply forms on the propagation of airborne contaminant in the passenger breathing area were studied under considering recirculating air. Taking B737-200 cabin model as the research object, the distributions of contaminant in the breathing area under the ceiling, sidewall and mixed air supply modes were analyzed under the same air supply quantity and different proportions of recycled air when air contamination event occurs. Research result shows that in the state that the contaminant enter the cabin, the concentrations of contaminant in different air supply forms and the proportions of recycled air are different at different positions, and the concentration of contaminant in ceiling air supply form is higher. When the proportion of recycled air increases by 20%, the concentrations of contaminant in the forms of mixed air supply, sidewall air supply and ceiling air supply decrease by about 18.9%, 20.6% and 15.6%, respectively, and the contaminant concentration decreases most under the form of sidewall air supply. In the contaminant removal stage, compared with the mixed air supply and ceiling air supply, the contaminant removal efficiency of sidewall air supply increases by about 42.6% and 38.7%, respectively. When using the mixed air supply or ceiling air supply, the contaminant removal efficiency increases significantly with the increase of the proportion of recycled air. When the proportion of recycled air increases by 20%, the contaminant removal efficiencies of mixed air supply and ceiling air supply increase by about 10.7% and 7.7%, respectively. With the increase of the proportion of recycled air in the form of sidewall air supply, the contaminant removal efficiency is not significantly improved. At a higher proportion of recycled air, the best contaminant remove efficiency can still be maintained, which can realize the dual optimization of pollutant removal and energy saving. Therefore, the use of sidewall air supply and high recycled air ratio can minimize the harm of contaminant without changing the air supply volume.More>
2019, 19(1): 108-118. doi: 10.19818/j.cnki.1671-1637.2019.01.011
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Shock response of vehicle powertrain based on nonlinear drive-shaft model
HAN Qing-zhen, HE Ren
Abstract: The nonlinear drive-shaft model of the vehicle powertrain that consists of linear and nonlinear terms was established. Based on the Lagrange equation with dissipative terms, the quantized two-mass model was obtained from the nonlinear drive-shaft model. The shock response equation was obtained by the equivalent torsion angle from two ends of the powertrain to one end. The stability of the shock response equation, as well as the stable region of the parameters, were obtained by using the Routh-Hurwitz criterion. Simulation result shows that when the values of the nonlinear damping are set as 0, 1/10, and-1/10 of the linear damping, the absolute values of the first peak of shock response are 0.153 9, 0.101 4, and 0.371 6, respectively. When the value of the nonlinear damping is 1/10 of the linear damping, the absolute value of the first peak is the smallest, which indicates that the positive nonlinear damping is beneficial to the shock response. When the values of nonlinear stiffness are set as 0, 1/10, and-1/10 of the linear stiffness, the absolute values of the first peak of the shock response are 0.153 9, 0.178 8, and 0.115 9, respectively. When the value of nonlinear stiffness is-1/10 of the linear stiffness, the absolute value of the first peak is the smallest, which indicates that the negative cubic nonlinear stiffness is beneficial to shock response. When the value of nonlinear stiffness is fixed at-1/10 of linear stiffness and the coefficients that represent the nonlinear damping are set as 0.1, 0, and-0.1, respectively, the absolute values of the first peak are obtained as 0.078 4, 0.114 2, and 0.231 6, respectively. When the coefficient representing the nonlinear damping is set as 0.1, the absolute value of the first peak of the shock response is the smallest, which indicates that, on the basis of the linear stiffness and damping of the powertrain system, the shock resistance of the powertrain can be improved by introducing negative nonlinear cubic stiffness and positive nonlinear damping to the linear powertrain.More>
2019, 19(1): 119-126. doi: 10.19818/j.cnki.1671-1637.2019.01.012
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Spatio-temporal cooperative optimization model of surface aircraft taxiing
JIANG Yu, WANG Huan, FAN Wei-guo, CHEN Li-li, CAI Meng-ting
Abstract: The taxiing schedule problem of surface aircraft at the airport was studied by introducing a bi-level programming method. The impacts of taxiing cost and conflict on the operation efficiency and safety of surface aircraft were considered. The spatio-temporal cooperative optimization model of surface aircraft taxiing was constructed by taking the pushout delay time and aircraft taxiing path as decision variables, and the minimum total taxiing distance of surface aircraft without conflict in the taxiway system as objective functions. According to the characteristics of aircraft taxiway schedule problem, a bi-level programming algorithm suitable for the aircraft taxiing spatio-temporal collaborative optimization model was designed to reduce the taxiing distance and waiting time of aircraft. In order to verify the validity of the model and algorithm, the result of the first-come-first-served scheduling plan was compared, and the impacts of waiting time and taxiing distance on the efficiency of surface aircraft were analyzed. Analysis result shows that compared with the first-come-first-serve scheme, the spatio-temporal cooperative optimization model can ensure zero-collision during the aircraft taxiing, and the total taxiing distance of 16 aircrafts reduces from 40 690 m to 37 700 m with a reduction of 8%. The average running time of aircraft is 254 s, which shows that the overall operating efficiency of taxiway system increases. Under the condition that the replication groups number is 100 and the mutation probability is 0.4, the optimal solution of spatio-temporal cooperative optimization model can be obtained within 412 s, and the model has significant efficiency and convergence. It can be seen that on the premise of guaranteeing the safety of aircraft taxiing, the spatio-temporal collaborative optimization model of surface aircraft can effectively improve the efficiency of aircraft taxiing scheduling, reduce the aircraft operation cost, and provide the decision support for the busy airport taxiway scheduling.More>
2019, 19(1): 127-135. doi: 10.19818/j.cnki.1671-1637.2019.01.013
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Review on integrated scheduling of container terminals
CHANG Yi-mei, ZHU Xiao-ning, WANG Li
Abstract: According to different research areas, the domestic and foreign literatures on the integrated scheduling in the quayside area, container yard and between quayside area and container yard were summarized. The future research direction was proposed. Analysis result shows that the most literatures study the integrated scheduling problem at the traditional container terminals, and make rich achievements. Only a few literatures focus on the integrated scheduling problem at the automatic container terminals. With the development of technology and the increase at the automatic container terminals, the integrated scheduling problem at the automatic container terminals should be studied by combining the characteristics of automatic container terminals in the future. Most literatures concentrate on the integrated scheduling problems of container terminals under the static or certain conditions. Only a few literatures focus on the integrated scheduling problem of container terminals under the dynamic or uncertain conditions, Therefore, with the research deepen progressively, the integrated scheduling problem under the dynamic or uncertain factors will be the focus of future research. The objective functions are developed based on the time, cost or the combination of time and cost in most literatures. Although these can enhance the efficiency of container terminals, but still have some limitations. As the energy problems get increasingly serious, a multi-objective model for establishing the balanced energy consumption and other optimization objectives should be put forward. Most literatures propose the heuristic algorithms to solve the problem and get better optimal solutions. To increase the diversification of solution methods, a solution strategy combining algorithm computation with simulation checking should be proposed. With the rapid development of intermodal transportation, the influence of railway operation area on the container terminal should be considered, and the integrated scheduling between the container terminal and railway operation area should be studied.More>
2019, 19(1): 136-146. doi: 10.19818/j.cnki.1671-1637.2019.01.014
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Elastic adjustment strategy of dynamic interval optimization for high-speed train
CAI Bai-gen, SUN Jing, SHANGGUAN Wei
Abstract: To ensure the train operation safety and improve the carrying efficiency of railway line, the interval elastic adjustment strategy of high-speed train tracking operation and dynamic optimization of manipulating trajectory were researched under the moving block system. The optimal objectives including the operation safety, efficiency, energy consumption of high-speed train and comfort of passengers were taken into account to obtain the train operation control strategy curve, and the train tracking operation process was researched. The multi-objective optimization of high-speed train model of train operation process was solved through the differential evolution algorithm, and the offline optimal operation control strategy curve was obtained. The train elastic tracking interval model was proposed, and the real-time change of tracking interval during the train operation process was analyzed. On the basis of the elastic interval model, a dynamic train tracking operation control strategy adjustment mechanism was designed. The train actual operation data were collected, and the actual tracking interval between adjacent trains was monitored in real-time. The interval was evaluated whether it meets the safety and time-efficiency constraints, and the assessment result was analyzed. The following train's operation state and condition were adjusted online according to the conversion principle of operation phases, and the train tracking interval was optimized in real-time. The numerical simulation using the real operation data of Wuhan-Guangzhou High-speed Railway Line from Chibi North Station to Changsha South Station was conducted. Simulation result indicates that compared with the real section operation data, the energy consumption reduces by 6.86% by adopting the offline optimal operation control strategy curve. Compared with the fixed tracking time interval model, the transport efficiency of the overall railway line is efficiently promoted by adopting the control strategy dynamic adjustment mechanism based on the elastic model, which reduces the critical safety departure interval from 234 s to 161 s. The overall railway line operation efficiency is shortened from 6 434 s to 6 376 s, and the energy consumption of tracking train reduces by 7.194% compared with the actual operation data.More>
2019, 19(1): 147-160. doi: 10.19818/j.cnki.1671-1637.2019.01.015
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Interoperation programme design and performance test on LTE-M integrated bearing system
ZHAO Hong-li, CAO Yuan, ZHU Ye
Abstract: For the problem that when the commercial public network of long term evolution (LTE) was used to bear the urban rail transit, the reliability and real-time performance of interoperation crossing core network could not meet the service demands, the service demands of long term evolution for the metro (LTE-M) integrated bearing system were analyzed. The demands of interoperability and the data service connectivity of LTE-M integrated bearing system were put forward. The connectivity operating mechanism of LTE-M integrated bearing system was studied. The method of reliability assurance was designed, including the route reestablishment and failure switch between core networks, and the single plate switch of core network. The interoperation system architecture of LTE-M integrated bearing system was presented. The interoperation test environment for LTE-M integrated bearing system was established in laboratory. The signaling and data were analyzed to verify whether the system meet the application requirements. The hand-off test and route test between core networks, failure switch test of core network, reliability test and interoperability performance test on LTE-M integrated bearing system were conducted. Research result shows that to meet the demands of urban rail trains operating cross-line, it should realize the interoperations among the reference points between LTE-M terminal and base station, between the serving gateway of core network and packet data network gateway, between mobility management entities, and between home subscriber server and mobility management entity. The hand-off time between core networks of LTE-M integrated bearing system is less than 1 s, the route reestablishment time between core networks is less than 1 s, the failure switch time of single plate of core network is less than 2 s, and the failure switch time between core networks is less than 31 s. The transmission delay for LTE-M integrated bearing system interoperability service is less than 0.15 s, and the packet loss rate is less than 1%. When the LTE-M integrated bearing system works at a 10 MHz bandwidth, it can simultaneously transmit one path 100 kb·s-1 communication based train control service, two path 2 Mb·s-1 closing circuit TV service and one path 4 Mb·s-1 passenger information system service. Thus, the interoperation performance of LTE-M integrated bearing system can meet the service demands for the cross-line operation of urban rail transit.More>
2019, 19(1): 161-171. doi: 10.19818/j.cnki.1671-1637.2019.01.016
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Research progress on automatic image processing technology for pavement distress
XU Zhi-gang, CHE Yan-li, LI Jin-long, ZHAO Xiang-mo, PAN Yong, WANG Zhong-ren, WEI Na, SONG Hong-xun
Abstract: The important research achievements on the automatic image processing technology for pavement distress were summarized. The research progress of key technologies in this field was analyzed, including the pavement distress detection system, image processing algorithm and evaluation of recognition algorithm. The detection accuracy and applicability were compared for the different pavement distress detection systems and target automatic recognition algorithms. The possible future research directions of automatic pavement distress image processing technology were presented. Research result shows that in the aspect of pavement distress detection system, from early image acquisition based on the photography technology to the current 3D laser scanning technology, the pavement image acquisition technology becomes more and more convenient and effective. However, there still exist some challenges in the automatic analysis on distress images and automatic recognition algorithm on targets. In the aspect of pavement distress image processing algorithm, the traditional algorithms of segmenting pavement distress targets evolve from the methods using single feature (such as grayscale and edge shape) to multi-feature fusion-based methods and graph optimization-based detection methods. Furthermore, there emerges some dedicated algorithms for recovering or connecting cracks, greatly improving the detection accuracy of crack recognition. Nonetheless, as the complexity of these algorithms grows up, the required computational resources and the size of prior knowledge base both sharply increase. In the aspect of evaluation and comparison of crack processing algorithms, manual segmentation is mainly used to evaluate automatic recognition results. At present, it is urgent to establish a large-scale pavement distress image database opening to the world, so as to objectively and effectively evaluate various existing image processing algorithms for pavement distress. Automatic image processing algorithms for pavement distress based on 2D image features analysis is difficult to achieve the best results with detection accuracy, algorithm versatility and real-time performance simultaneously. In recent years, a large number of scholars begin to use the deep learning neural network to automatically recognize pavement distress, but the technology is still in an active evolution process. In the aspect of improving the accuracy and efficiency of automatic recognition for pavement distress, the 3D laser scanning technology and the deep learning technology based on artificial intelligence will greatly promote the final breakthrough on automatic image recognition technology for pavement distress in the future.More>
2019, 19(1): 172-190. doi: 10.19818/j.cnki.1671-1637.2019.01.017
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