交通运输工程学报

Determination of volumetric parameters and impacting mechanism of water stability for steel slag asphalt mixture

GAO Zhen-xin, SHEN Ai-qin, ZHAI Chao-wei, GUO Yin-chuan, YU Peng

Abstract: The effective relative densities of steel slag aggregates with different sizes were tested by immersion test, and the determining method of volumetric parameters for steel slag asphalt mixture was proposed.The water stabilities of asphalt mixtures with different steel slag contents were comprehensively evaluated by residual stability, freezing-thawing splitting intensity ratio and asphalt film thickness.X ray fluorescence spectrometry, scanning electron microscope, and mercury injection test were used to analyze the influencing mechanism of steel slag on the water stability of asphalt mixture based on the chemical compositions and microstructure of steel slag.Analysis result shows that for large water imbibition aggregates such as steel slag, the effective relative density measured by immersion test is 1.5% higher than the value obtained by the calculation method, and is closer to the actual density, therefore, it is more reasonable to useimmersion test to determine the volumetric parameters of steel slag asphalt mixture.The water stability of steel slag asphalt mixture improves with the increase of steel slag content.The residual stability increases by 12% and the freezing-thawing splitting intensity ratio increases by13% when the steel slag content is 70%.The asphalt film thickness of steel slag asphalt mixture gradually increases with the increase of steel slag content.When the content of steel slag is 70%, the asphalt film thickness increases by 13%.The thicker asphalt film can effectively prevent water intrusion and increase the content of structural asphalt on aggregate surface, so the water stability of steel slag asphalt mixture increases.The calculation value of asphalt film thickness of steel slag asphalt mixture is 6-7μm, and the water stability of steel slag asphalt mixture is positively related to the thickness of asphalt film, so the recommended value of asphalt film thickness is 7μm based on the water stability of steel slag asphalt mixture.The steel slag is super alkaline and porous, meanwhile, the internal structures of pores are complex, therefore, the effective contact area between steel slag aggregate and asphalt increases, the good mechanical occlusal force forms, and the adhesion increases, so that the water stability of asphalt mixture improves significantly.More>

2018, 18(2): 1-10. doi: 10.19818/j.cnki.1671-1637.2018.02.001

FullText HTML (173) PDF (3869KB) (673)

Fatigue performance of floorbeam cutout on orthotropic steel bridge decks

ZHU Zhi-wen, XIANG Ze, LI Jian-peng

Abstract: In order to reveal the mechanism involved in base-metal cracking of floorbeam cutout on orthotropic steel bridge deck, the finite element program ANSYS was employed to establish both the segmental model of steel box girder and the local submodel of bridge deck, and the check of mesh independent was conducted to ensure the calculating precision.Thereby, the stress response characteristics of floorbeam cutout were analyzed under moving wheel loads, the fatigue evaluations were performed based on hot spot stress method and nominal stress method, respectively, and the influences of floorbeam thickness and cutout shape on the stress of structural detail stress were discussed.Research result shows that the length of stress influence line of floorbeam cutout detail in longitudinal direction of bridge is 2 times of floorbeam spacing, thus, loading with merely middle-axle group is appropriate.According to AASHTO LRFD, a fatigue truck with five axles can generate 2 or 3 stress cycles at the structural detail.The worstlongitudinal and transverse loading locations of floorbeam cutout are the wheel loads center locating at the intersection of rib wall and deck plate, and the front wheel of middle-axle group locating at 0.3 mfrom the floorbeam, respectively.The angle between the stress direction of stress concentration point of floorbeam cutout edge and the horizontal plane is 67.2°.Fatigue assessment result is closely relevant to the nominal stress extraction position.The hot spot stress method based on fatigue life curve of FAT125 is feasible for the fatigue assessment of floorbeam cutout.According to the equivalent principle of fatigue damage, the stress at 5 mm from cutout edge can also be extracted for the fatigue assessment base on the nominal stress method.It is suggested that the cutout shape in Eurocode 3 (highway bridge) with a large curve radius is preferable, and the hot spot stress reduces by 12.4% compared with the researched cutout shape.The stress range is below the cut-off limit as the thickness of floorbeam is not less than 12 mm, hence the cutout reaches a infinite fatigue life.Floorbeam cutout cracking is related to poor cutout shape, thin floorbeam, imperfect fabrication technology and high truck traffic volume.More>

2018, 18(2): 11-22. doi: 10.19818/j.cnki.1671-1637.2018.02.002

FullText HTML (407) PDF (2190KB) (637)

Design method of partially prestressed concrete beam based on crack width

DU Jin-sheng, LIU Ling, FENG Wei, XU Bing

Abstract: In order to simplify the design process of partially prestressed concrete (PPC) beam and reduce the number of trial calculation and the range of prestressed reinforcement amount, a design method of partially prestressed concrete (PPC) beam based on crack width was proposed.Starting from the crack width under normal service condition and based on the regulations of crack width in Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts (JTG D62—2004) (Highway Code for short), the stress of non-prestressed reinforcement in tensile region was derived based on the maximum crack width.A cubic equation was established to calculate the neutral axis height of cracking section.Then based on the requirements of effective strain of prestressed reinforcement and the provisions of the minimum reinforcement ratio in Highway Code, the maximum and minimum amounts of prestressed reinforcement were obtained.Key design procedure and a detailed design example were also presented.Furthermore, a T-shaped test girder was designed to verify the design proposed method.Research result shows that the flexural bearing capacity and the maximum and minimumamount of prestressed reinforcement of designed girder can meet the code requirements.The load and deflection of test girder basically show a tri-line relationship.When the external load is50.0 kN, crack occurs in the midspan of test girder.When the external load is 128.5 kN, the tensile non-prestressed reinforcement yields.When the external load is 157.8 kN, the concrete is broken in the midspan of test girder.The test girder designed by the proposed method exhibits the characteristics of ductile failure and can meet the requirements of bearing performance.The measured maximum crack width of test girder is 0.18 mm before the non-prestressed reinforcement yielding and less than the predicted maximum crack width 0.20 mm, which means that it can meet the requirements of normal use.Obviously, the proposed design method is reasonable and feasible for practical design.It can simplify the design procedure of PPC beam.9 figs, 25 refs.More>

2018, 18(2): 23-30. doi: 10.19818/j.cnki.1671-1637.2018.02.003

FullText HTML (209) PDF (827KB) (512)

Flexural behaviors of full-scale prestressed concrete hollow slab girders with composite strengthening

WANG Shi-chao, WANG Chun-sheng, WANG Qian, TIAN Xiao-feng, DUAN Lan

Abstract: The flexural behavior experiments of three full-scale prestressed concrete hollow slab beams were carried out, including unreinforced girder, steel plate-concrete composite strengthening (SPCCS) girder, and steel plate-prestressed concrete composite strengthening (SPPCCS) girder.The strain, slip, crack distribution, bearing capacity, stiffness, and ductility at the critical position of each full-scale test girder were analyzed.According to the plastic failure characteristics of test girders, the effect of secondary loading was taken into account, and the calculation formulas of ultimate flexural capacities of full-scale test beams were proposed.Testresult shows that the failure modes of strengthened girders are plastic bending failure, and the deformations of mid-span cross-sections satisfy the plane cross-section assumption.The relative slips between the strengthening steel plate and the new concrete, the strengthening part and the original structure are less than 0.05 mm, all parts of test girders after strengthening can cooperatively work.Compared with the unreinforced girder, the ultimate flexural capacity of SPCCS concrete hollow slab girder increases by 1.08 times, and the value of SPPCCS concrete hollow slab girder increases by 1.43 times.Therefore, the composite strengthening can obviously improve the ultimate bearing capacity of test girder.Compared with the unreinforced girder, the ductility coefficients of 2 strengthening test girders increase by 21%, and when test load is 200 kN, the stiffnesses increase by 1.55 times and 3.07 times, respectively.Therefore, the composite strengthening can obviously improve the stiffness and ductility of test girder.Compared with SPCCS technology, SPPCCS technology can significantly improve the bearing capacity and stiffness of test girder in the service stage.For 2 strengthening test girders, the ratios of ultimate flexural capacities computed by using the proposed simplified formulas to the experimental values are 0.94 and 0.96, respectively.Therefore, the formulas can be used to accurately calculate and analyze the flexural behaviors of prestressed concrete hollow slab beams strengthened by SPCCS technology.More>

2018, 18(2): 31-41. doi: 10.19818/j.cnki.1671-1637.2018.02.004

FullText HTML (151) PDF (2186KB) (517)

Seismic performance of prefabricated assembled pier with grouted sleeve and prestressed reinforcements

GE Ji-ping, YAN Xing-fei, WANG Zhi-qiang

Abstract: According to the mechanical characteristics of prefabricated assembled piers for rail transit, the assembly scheme of grouted sleeve and prestressed reinforcements was put forward.Three different types of piers were designed, including the integral cast-in-place reinforced concrete specimen (RC), the prefabricated and prestressed concrete specimen with strands andgrouted sleeves (PCSS), and the prefabricated and prestressed concrete specimen with screw thread steel bar and grouted sleeve (PCTS).The evaluation results of various pseudo-static evaluation indicators for each type of bridge pier were analyzed by using pseudo-static test method.The seismic performances of various kinds of piers were compared.Test result shows that the indexes of PCSS and PCTS are very similar, and the maximum error is 2.2%.The grouted sleeve shifts the traditional area of plastic hinge up to the top of grouted sleeve, so it shows that the grouted sleeve has local reinforcing effect on the traditional plastic hinge region, and the height of plastic hinge stirrup is advised to add extra one height of grouted sleeve.The concrete axial pressure of specimen increases by 1 time when using prestressed reinforcements, and the corresponding cracking load also increases by approximate 1 time.The mean values of yield load and ultimate load of PCSS are 31% and 34% higher than those of RC, respectively.The average equivalent yield displacement, ultimate displacement and drift ratio are 17%, 13%and 13% higher than those of RC, respectively, but the ductility factors of PCSS decreases by10%.At the same drift ratio of 6%, the mean residual displacement of PCSS is 61% of RC, which shows better re-centering capacity.Compared with RC, the stiffness of PCSS increases by13%.Compared to screw thread steel bar, steel strands can be bent and bundled, and the area is flexible to adjust.So the bridge pier specimens with unbonded prestressed reinforcements and grouted sleeve have better operation and seismic performance, and can be served as the recommended scheme for prefabricated assembled rail pier.More>

2018, 18(2): 42-52. doi: 10.19818/j.cnki.1671-1637.2018.02.005

FullText HTML (386) PDF (2205KB) (518)

Force rule of composite lining considering creep of tunnel surrounding rock

GU Shuan-cheng, HUANG Rong-bin, SU Pei-li

Abstract: Anchor force was regarded as the physical force acting on the surrounding rock, the initial support and the surrounding rock in the anchorage zone were regarded as reinforced surrounding rock, and the mechanical model of surrounding rock was established.Based on the unified strength theory, the stress and deformation laws of surrounding rock of tunnel in the creep process were analyzed, the expressions of stress and deformation of composite lining were derived, and the stress characteristics of supporting structure in the creep process of tunnel surrounding rock and the change laws of secondary lining stresses under different initial support strengths were analyzed.Analysis result shows that compared with the excavation stage, the maximum forces of bolt and shotcrete are 48 kPa and 286 kPa in the creep process of surrounding rock, respectively, and increase by 57.5% and 13.7%, respectively, which exceeds themaximum bearing capacity of supporting structure when the initial support is designed in accordance with the principle of"the initial support should be based on the joint force with the surrounding rock to ensure the safety of construction phase".So it can cause the failure of initial support structure during tunnel operation if only to meet the stability of surrounding rock during tunnel excavation without considering the additional stress caused by the creep during designing the initial support, which is not conducive to tunnel stability.When the thickness of secondary lining increases from 300 mm to 500 mm, its maximum load increases by 40.5%, and the load sharing ratio increases from 25.2% to 36.2%.When the initial support strength increases, the load of secondary lining reduces by 14.5%, and the load sharing ratio reduces from 25.2% to22.3%.So the load of secondary lining decreases with the increase of initial supporting strength, but increases with the increase of itself strength, and it is important to rationally allocate the strengths of initial support and secondary lining support to realize the reasonable distribution of surrounding rock pressure.In order to realize the effect that the primary support and the secondary lining jointly bear the additional stress caused by the creep under the condition of soft rock geology, the primary support not only ensures the stability of surrounding rock during tunnel construction, but also avoids the structural damage in the process of rock creep.More>

2018, 18(2): 53-60. doi: 10.19818/j.cnki.1671-1637.2018.02.006

FullText HTML (181) PDF (520KB) (423)

Analytical method of nonlinear oil film force of hydrodynamic crankshaft journal bearing

ZHANG Yong-fang, WANG Xia, HUANG Yue, LI Sha, LIU Cheng, LU: Yan-jun

Abstract: An analytical method was proposed for calculating the nonlinear oil film force of hydrodynamic crankshaft journal bearing based on variables separation method, Sturm-Liouville theory, and Reynolds boundary conditions.The oil film pressure distribution of Reynoldsequation for incompressible fluid hydrodynamic lubrication of the bearing was expressed as an additive form of a particular solution and a homogeneous solution.By using variables separation method, the pressure distributions of particular solution and homogeneous solution were respectively split in an additive and multiplicative forms of circumferential separation function and axial separation function.For convenience, the circumferential separation function of particular solution was solved by using the Sommerfeld transformation, and the termination position angle of oil film was determined by using the continuity condition.Because there was no direct solution for the circumferential separation function of homogeneous solution, the circumferential separation function was transformed as Sturm-Liouville equation by using the approximation function of oil film thickness, and the eigenvalues and eigenfunctions were obtained by using the boundary conditions.The circumferential separation function of homogeneous solution was expanded by using the infinite series of trigonometric functions.The axial separation function of homogeneous solution was obtained by the hyperbolic tangent function with the eigenvalues.In the complete oil film field, the analytical expression of oil film pressure distribution was integrated to obtain the nonlinear oil film force of crankshaft bearing.Analysis result shows that the nonlinear oil film force calculated by the analytical method is good agreement with the value calculated by the finite difference method, and the difference is about 5% when the eccentricity ratio is small. When the eccentricity ratio rises from 0.2 to 0.6, the maximum value of termination position angle of oil film reduces by 13.5%. When the dimensionless speed disturbance rises from 0 to 0.03, a relative variation of 3.3% is obtained for the termination position angle of oil film.When the number of eigenvalues is greater than 20, the variations of homogeneous solutions of dimensionless oil film force in the radial and tangential directions are really small, and their values are about-2.8 and 4.6, respectively.Therefore, the analytical method can calculate the nonlinear oil film force of hydrodynamic crankshaft journal bearing accurately.The eccentricity ratio has a great influence on the rupture of oil film, and the rupture easily takes place when the eccentricity ratio is bigger.Compared with the eccentricity ratio, the speed disturbance has less influence on the rupture of oil film.A high calculation precision can be obtained for the homogeneous solution of dimensionless oil film force when the number of eigenvalues is not less than 20, which meets the requirement of engineering.18 figs, 25 refs.More>

2018, 18(2): 61-71. doi: 10.19818/j.cnki.1671-1637.2018.02.007

FullText HTML (110) PDF (1123KB) (451)

Handling stability and parameter optimization of centre axle trailer train

ZHANG Jing-ming, REN Ze-kai, ZHANG Hao, ZHANG Hong-wei

Abstract: To improve the handling stability of centre axle trailer train, the relationships among yaw motion, roll motion, longitudinal and lateral motion were analyzed.The 4-degree of freedom (DOF) dynamics simulation model was established by using MATLAB/Simulink based on the theory of vehicle dynamics.The multi-DOF complex nonlinearity simulation model of the train was established by using TruckSim.The handling stability testing system of the train was constructed through VBOX data acquisition system and RT gyroscope.According to the related standard, single lane change tests were carried out in real vehicle test condition and simulation test condition, and the comparative analysis between test result and simulation result was carriedout.Comprehensive evaluation score model of the train was proposed based on the rearward amplification (RA) of yaw rate, articulation rate, rearward amplification of lateral acceleration, load transfer ratio (LTR).Through virtual prototyping technology, the related parameters that have significant impacts on the handling stability of the train were optimized based on the theory of uniform test and multiple linear regression analysis.Optimization result shows that the related parameters of tractor and centre axle trailer improve in varying degrees after the optimization.The maximum yaw rates of tractor and centre axle trailer decrease from 0.107 2 and 0.140 8 rad·s^-1 to 0.092 5 and 0.103 7 rad·s^-1, respectively, and the rearward amplification of yaw rate of centre axle trailer train reduces by 15.15%.The maximum lateral accelerations of tractor and centre axle trailer decrease from 0.21 g and 0.27 g to 0.19 g and 0.20 g, respectively, and the rearward amplification of lateral acceleration of centre axle trailer train reduces by 12.10%.The maximum articulation rate and maximum load transfer ratio of centre axle trailer train reduce by23.01% and 29.41%, respectively.The comprehensive evaluation score of centre axle trailer train increases from 86.66 to 109.02, so the comprehensive performance improves.More>

2018, 18(2): 72-81. doi: 10.19818/j.cnki.1671-1637.2018.02.008

FullText HTML (268) PDF (1519KB) (674)

Hunting motion stability of wheelset based on energy method

SUN Jian-feng, CHI Mao-ru, WU Xing-wen, LIANG Shu-lin, LI Wei

Abstract: In order to analyze the formation mechanism and energy transfer mechanism of wheelset hunting motion, the energy expression in the process of hunting motion was established based on the theory of vehicle system dynamics.According to the phase relationship of wheelset movement parameters and energy expression, the work of each part and energy transfer route during the hunting motion were determined.Input energy values under different parameters were calculated through numerical simulation, thus the influences of tread equivalent conicity, mass of wheelset, primary suspension stiffness and gravity stiffness on the stability of wheelset were compared.Research result shows that the synergy of creep force and cone tread is the fundamental cause of hunting motion.The stiffness force contained in creep force inputs energy into the wheelset lateral movement through the regulating action of wheel/rail longitudinal and lateral creep rate, and the damping term in creep force consumes the energy of wheelset system.When the inputenergy is larger than the dissipated energy in a cycle, the hunting motion diverges.When the input energy is less than the dissipated energy in a cycle, the hunting motion converges.When the input energy is equal to the dissipated energy in a cycle, the wheelset performs periodic motion with a constant amplitude.The enlargement of inertia term and conicity is harmful to the stability of wheelset, while the enlargement of primary stiffness is in favor of the stability of wheelset.Tread equivalent conicity has the biggest influence on the stability of hunting motion of wheelset.When conicity increases from 0.15 to 0.20, the input energy increases nearly by 9.5 times.Primary suspension stiffness comes the second.When the stiffness increases from 75 kN·m^-1 to 100 kN·m^-1, the input energy decreases nearly by 60%.The mass of wheelset is the smallest one.When the mass of wheelset increases from 1 000 kg to 2 100 kg, the input energy increases nearly by 1.1 times.Under the condition of conical tread, the effect of gravity stiffness has little influence on the stability, which can be ignored.More>

2018, 18(2): 82-89. doi: 10.19818/j.cnki.1671-1637.2018.02.009

FullText HTML (252) PDF (522KB) (649)

Control of energy-reclaiming semi-active suspension with linear motor based on varying charge voltage method

CHEN Shi-an, SUN Wen-qiang, WANG Jian, CAI Yu-meng, WANG Jun-cheng

Abstract: To solve the difficult problems in the control of energy-reclaiming semi-active suspension (ERSAS) with linear motor as the actuator, such as complex control method and unsatisfactory control effect, a calculating method of charge voltage based on a single phase equivalent model was proposed by combining with the principle and method of varying charge voltage (VCV).The control system of ERSAS was designed to regulate the energy-reclaiming actuator with linear motor.The half vehicle dynamics model with 4 degrees of freedom and the VCV linear motor model were set up, and the LQG control strategy was used to obtain the ideal energy-reclaiming damping forces.The theoretical model with bridge rectifier was equivalent toasingle phase motor model, and the back electromotive force, electromagnetic thrust coefficient, resistance and inductance of single phase motor model were calculated.The controller was solved by using the actual charge voltage, the relative speeds of front and rear suspensions and the ideal energy-reclaiming damping forces were taken as the inputs to calculate the actual charge voltage, and the energy-reclaiming control was realized by using the actuator. The suspension performances and energy-reclaiming effects were analyzed by comparing the ERSAS with the passive suspension and the ideal semi-active suspension.Analysis result shows that, compared with the passive suspension, the comprehensive performance indexes of ERSAS and ideal semiactive suspension reduce by 38.97% and 45.42%, respectively, the correlation coefficients between the actual and ideal energy-reclaiming damping forces of front and rear suspensions reach to 0.967 4 and 0.976 8, respectively, and 56.7% and 62.1% of vibration energies in the front and rear suspensions are reclaimed and stored in the battery, respectively.In summary, adopting ERSAS based on the VCV method and the single-phase equivalent model can recover most of vibration energy and improve vehicle ride performance.More>

2018, 18(2): 90-100. doi: 10.19818/j.cnki.1671-1637.2018.02.010

FullText HTML (151) PDF (2418KB) (441)

Connectivity characteristics of urban road network elements based on improved degree

WANG Shi-guang, YU De-xin, WANG Shu-xing, XING Ru-ru, LI Zhi-lin

Abstract: Combined with the lane properties (number, width, direction, etc.) of urban road network, the definition of degree in complex network was extended. The connectivity characteristics of road network elements including roads and intersections were analyzed by using primal and dual approaches respectively.Considering the features of real road network and resident trip cognition, intersections were regarded as nodes, and roads were determined by named street approach and stroke-like analysis from the perspective of resident cognition.Thelane number of motor vehicle was emphasized to improve the concept of degree.Under the new definition of network elements, the connectivity characteristics of intersections and roads were analyzed by using the method of average nearest neighbors'degree based on the improved measures.Considering the deficiency of existing method, the concept of link coefficient was proposed so that a more clear connectivity characteristic was found.The main urban zone of Xiamen City was regarded as an example, the connectivity characteristics of road network were analyzed to validate the analysis method.Analysis result shows that the city's intersection and road element networks are both scale-free networks, and the power exponents are 1.69 and 2.70, respectively.The clear segmentation features are exhibited with the boundaries of particular points.Among them, the threshold values of link coefficients based on improved degree are 3.40 and 8.33, separately.The threshold value of hierarchical measure of roads is 5, and the threshold value of link coefficient based on the hierarchical measure is 3.From the point of view, it is shown that the urban road network is not simple assortative or disassortative network.The proposed analysis method of connectivity characteristics of urban network elements is of great significance for recognizing the topologic properties of urban road network and building network evolution model.11 figs, 29 refs.More>

2018, 18(2): 101-110. doi: 10.19818/j.cnki.1671-1637.2018.02.011

FullText HTML (182) PDF (2480KB) (709)

Evaluation methods comparison of quantitative transportation network efficiency

QIN Jin, HE Yu-xin

Abstract: The existing evaluation methods of quantitative traffic network efficiency were compared.Network structure, traffic demand, travel choice, travel cost and other factors were considered, and the evaluation result rationalities of three methods were studied from the following three aspects, namely the analytic calculation, influence rule of traffic demand on network efficiency under fixed network structure, and influence rule of network structure on network efficiency under fixed traffic demand.The pros, cons and applications of different methods were summarized.Comparative result shows that the calcuation method of weighted network operation efficiency (method 1) does not consider the congestion effect of transportation network, and the calculated network efficiency is a monotone function of traffic demand, so it cannot be used in traffic congested network.The calcuation method of transportation congestednetwork efficiency (method 2) is suitable for the efficiency evaluation of congested network, but for the premise of constant demand, the efficiency is a monotonous increasing function of connected path numbers between OD, and cannot reflect the influence rule of network structure on traffic network efficiency. The calcuation method of transportation network efficiency (method 3) can give a true reflection of comprehensive influence effect of network structure, traffic demand, travel cost and travel choice on network efficiency.In addition, the network efficiency calculated by method 3 and the Braess paradox can explain with each other, which indicates that method 3 have a relatively better rationality on the real operation performance.In the fixed structure of traffic network, there always exists a traffic demand to ensure the maximal network efficiency calculated by method 3.In the fixed demand of traffic network, there always exists a network structure to ensure the maximal network efficiency calculated by method 3.More>

2018, 18(2): 111-119. doi: 10.19818/j.cnki.1671-1637.2018.02.012

FullText HTML (127) PDF (553KB) (968)

Characteristics and energies in different frequency bands of environmental noise in urban elevated rail

LI Li, YIN Tie-feng, ZHU Qian, LUO Yan-yun

Abstract: The environmental noises of bridge side of the first stage elevated line of Metro Line 1 in a city were compared and tested, where the common monolithic track beds without sound barrier and the slab mat track bed with closed sound barrier were used separately.The Aweighted total sound pressure level and 1/3 octave linear sound pressure level of each measuring point on the bridge side were analyzed.The linear sound pressure level cloud diagrams were plotted.Noise energy ratio in each frequency band was studied.Analysis result shows that the slab mat track bed with closed sound barrier can effectively reduce the noise at the noise source strength point and the environmental noise on the bridge side.The noise reduction effect and energy distribution are related to the locations of frequency band and measuring point.At measuring points of similar bridge height, the noise reduction effect decreases with the increase ofthe distance from the centerline of line, while the noise reduction effect at the near-ground point increases with the increase of the distance from the centerline of line.The noise reduction effect of slab track mattress with closed sound barrier is significantly higher in mid-high frequency range than in low frequency range.When the center frequency of the 1/3 octave is 20.0-31.5 Hz, 55.0 m away from the centerline of line, the linear sound pressure level of slab mat track bed with closed sound barrier is 0.82-6.96 dB higher than that of common monolithic track bed without sound barrier.In the section of common monolithic track bed without sound barrier, the noise energy is mainly below 200 Hz above the ground of 1.2 and 9.8 m, in 250-400 Hz above the ground of 11.3 m, in 400-1 000 Hz above the ground of 12.8 m.Above the ground of 11.3 m, below 200 Hz, the noise energies are nearly equal between the common monolithic track bed without sound barrier and the slab mat track bed with closed sound barrier.In the slab mat track bed area with closed sound barrier, the noise energy below 200 Hz at the bridge side is higher.Therefore, it is recommended to take targeted measures for vibration reduction and noise reduction according to the locations of sensitive points beside the elevated bridge, and to focus on the problems that low frequency noise appears prominently after it has lost the shielding of medium and high-frequency noise.More>

2018, 18(2): 120-128. doi: 10.19818/j.cnki.1671-1637.2018.02.013

FullText HTML (221) PDF (1295KB) (465)

Measurement method of reference points of railway fixed pile based on monocular vision

FU Qin-yi, HU Jie-hua

Abstract: To improve the efficiency of absolute coordinates measurement of railway line fixed pile reference points, a new measurement method was proposed.The single-point measurement model of non-cooperative target was established.The laser target images were captured by monocular camera, the centroid method of saturation point was applied to exact laser spot center.The imaging rules of lines in plane were studied.A homography matrix solving method was constructed based on the orthogonal straight lines, and the image was corrected by perspective distortion.Then the horizontal and vertical offsets of laser spot and target were calculated based on the geometric similarity relationship between corrected image and target.In the indoor environment, orthogonal experiments of target image shooting were carried out. The horizontal and vertical offsets were calculated and compared.Experimental result shows that under the condition that laser spot and target are fixed, the distance from camera to target is constant, and the camera's angle is only variable, after the images are shot and corrected by perspective transformation, the errors between the horizontal and vertical offsets and the expected values are 0.082 and 0.254 mm, respectively.Under keeping the camera's angle and changing the distance from camera to target, the errors of corrected images are 0.126 and 0.014 mm, respectively.When the camera's angle and the distance from camera to target both change, the errors of corrected images are 0.329 and 0.064 mm, respectively.The errors between the horizontal and vertical offsets and the expected values of 3 tests are less than 0.5 mm.The range of horizontal and height measure errors of the system are ±1.52 and ±0.67 mm, respectively.According to the index of railway inspection tester's performance, the horizontal measure errors of railway are within ±3.0 mm and the height measure errors are within ±2.5 mm.Obviously, the precision of the measurement method can meet the railway measurement requirements.The horizontal distance measure error is totally depended on the laser range finder and tilt sensor, while the height measure error is depended on the laser range finder, tilt sensor and the offsets of laser spot to the target.8 figs, 26 refs.More>

2018, 18(2): 129-138. doi: 10.19818/j.cnki.1671-1637.2018.02.014

FullText HTML (118) PDF (1387KB) (416)

Prediction of marine meteorological effect on ship speed based on ASAE deep learning

WANG Sheng-zheng, SHEN Xin-quan, ZHAO Jian-sen, JI Bao-xian, YANG Ping-an

Abstract: In order to effectively predict the marine meteorological effect on ship speed, the alternating sparse auto-encoders (ASAE) network model based on the sparse auto-encoders (SAE) network model was proposed.A framework for predicting the marine meteorological effect on ship speed was constructed, and the association rules method was proposed to feature the navigation data, so as to excavate the factors and implicit relations affecting ship speed.Through the integration of ship navigation data provided by China COSCO Shipping Group and the meteorological data provided by the National Oceanic and Atmospheric Administration, ASAE network model was trained with training samples and verified with test samples, and theprediction result was compared to the results gained by support vector regression (SVR) model, back propagation neural network (BPNN) model, deep belief network (DBN) model and SAE network model.Research result shows that the training time and the mean squared error of marine meteorological effect on ship speed gained by ASAE network model are 8.2 sand 0.287 3 kn, respectively.Compared to SVR model, BPNN model, DBN model, and SAE network model, ASAE network model can shorten the training time by 1 683.1, 66.9, 2.0 and 1.5 s, respectively, and can increases the prediction accuracy by 0.045 5, 0.296 9, 0.153 4 and 0.178 6 kn.The forecast result of ASAE network model is more in line with actual sea condition, and can dynamically master the marine meteorological effect on ship speed.Estimating the actual speed through the predicted values can optimize the ship transportation process in meteorological navigation.It plays an auxiliary role to accurately consider the complex impacts of marine meteorological on navigation optimization strategies such as route planning and speed recommendation.Thereby, it improves the energy efficiency indicator of ship operation and achieves the purpose of energy saving, low-carbon and green navigation.More>

2018, 18(2): 139-147. doi: 10.19818/j.cnki.1671-1637.2018.02.015

FullText HTML (321) PDF (600KB) (1010)

Assistant driving decision method of vehicle lane change based on dynamic probability grid and Bayesian decision network

HUI Fei, MU Ke-nan, ZHAO Xiang-mo

Abstract: An assistant decision method of vehicle lane change was proposed to provide lane changing behavior decision for drivers.A driving environment information perception device consisting of on-board GPS, camera sensors, and radars was constructed.A non-uniform B-spline (NUBS) curve model was applied to modeling lane line.The lane line was detected, tracked and classified by coordinate calculation and searching strategy of control points.The effective driving region was determined based on lane line information.A driving environment geometric model of dynamic probability grid was established and considered as a compact representation of effective driving region.The influence of vehicle on the reliability of driving environment representation result was considered.Vehicle coordination information was mapped into the dynamic probabilitygrid based on Gaussian distribution, and the occupancy probability of each cell unit was calculated.Lane line information and occupied probability of cell unit were used as initial node state parameters and input into Bayesian decision network to estimate the occupancy state of probability grid unit, output the quantified representation result of current driving environment, and compute the expect utility values of three lane changing decisions including "no lane changing", "left lane changing"and "right lane changing".The optimal lane changing decision was determined by computing the ratio of each decision-making expect utility value.Experimental result shows that, in situation 1, the maximum expect utility value is 0.70 of "left lane changing", which is the optimal decision.In the corresponding dynamic probability grid, the"solid"state parameter of right lane line is 100.00%, so the expect utility of "right lane changing"is the lowest.The output optimal decision of decision-making system is "no lane changing", which is consistent with Chinese traffic laws and verifies the necessity of lane line classification.In situation 2, the decision expect utility values of"no lane changing"and "right lane changing"are 0.43 and 0.44, respectively, the ratio is close to 1, so it is unable to judge the optimal decision, and drivers can make the decision whether or not to change lane based on experience.More>

2018, 18(2): 148-158. doi: 10.19818/j.cnki.1671-1637.2018.02.016

FullText HTML (171) PDF (2516KB) (943)

User Center

Journal Info

Collection of Source JournalsMore>

2018 Vol. 18, No. 2

Search Type

Search Journal

LinksMore>