2020 Vol. 20, No. 1

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Research progress and engineering application of long lasting high performance weathering steel bridges
WANG Chun-sheng, ZHANG Jing-wen, DUAN Lan, TAN Chen-xin
Abstract: The new research progress and engineering application of weathering steel bridges at home and abroad were systematically generalized and analyzed. The key scientific and technological achievements in the fields of formation mechanism of stable corrosion-resistant patina, material selection standard, corrosion and fatigue damage mechanism, research and development of corrosion-resistant configuration and weathering bolt, and detection and evaluation technology of patina were summarized. The application scope and corrosion allowance design indexes of weathering steel bridges were combed and improved, and the key points of stabilization treatment and construction technology for the patina of weathering steel bridges were proposed. The damage detection and evaluation technology and corrosion damage maintenance and management technology of patina in weathering steel bridges were evaluated and analyzed. Combined with the experience and lessons of weathering steel bridge engineering accidents in the United States and Japan, as well as the construction technological innovation achievements of the first batch of long lasting high performance weathering steel bridges in China, the technological innovation direction in this field was discussed. Research result shows that the composition of corrosion-resistant patina contains the outer layer of γ-FeOOH and α-FeOOH, and the inner layer of amorphous FeOOH compound and Fe3O4. The formation and durability of stable corrosion-resistant patina are mainly affected by the factors such as chloride ion, accumulated water and dust. The material selection zoning map of high performance weathering steel bridges in China is suggested to establish, and the configuration design criterion of stable corrosion-resistant patina should be improved. The modern weathering steel bridge has the technical characteristics of high performance and long lasting. The in-plane stress fatigue, out-of-plane deformation fatigue test, numerical fracture mechanics simulation of configuration details with patina and the research on the long-term damage resistance of weathering high-strength bolts should be promoted to lay the foundation for establishing a perfect design criterion of anti-corrosion and anti-fatigue. The application of artificial intelligence technology will promote the significant progress of intelligent management and maintenance technology of long lasting high performance weathering steel bridges. The investment for research and development should be increased, a specification system should be established for the design, construction and maintenance of long lasting high performance weathering steel bridges with independent intellectual property rights in China, the high-quality engineering and technical talents should be cultivated, thus to promot the development of Chinese strong transportation network.More>
2020, 20(1): 1-26. doi: 10.19818/j.cnki.1671-1637.2020.01.001
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Review of construction and technology development of arch bridges in the world
CHEN Bao-chun, LIU Jun-ping
Abstract: To understand the development of arch bridges in the world in the recent 20 years, the construction and technology development of steel arch bridges, concrete arch bridges and concrete-filled steel tube(CFST) arch bridges were analyzed, and the future development was discussed. Analysis result shows that in the high-speed railway bridges with large live load and prominent power problem, the arch bridges have outstanding application advantage because of great rigidity. In terms of spans, the statistical average spans of steel arch bridges, concrete arch bridges and concrete-filled steel tube arch bridges are 464, 370 and 425 m, respectively, and the maximum spans of three kinds of arch bridges are increasing, especially for CFST arch bridges. In terms of materials, the application trend of high-strength steels in steel arch bridges is not obvious; the concrete strength is increasing with the span development of concrete arch bridges, and ultra-high performance concrete(UHPC) has been applied; the material strength of CFST arch rib is increasing; the proposal of ultra-high performance mortar(UHPM) will help the competitive advantage of masonry arch bridges. In terms of structures, the important technical development directions include the application of new materials, composite cross-sections of the arches and composite structures of the bridges, and the continuous and lightweight structures of the deck system, as well as more attention on their robustness. In terms of erection technologies, the invention of CFST stiff skeleton erection method, swing erection method and rapid erection method promotes the construction technologies of arch bridges. Driven by structural innovation and technological progress, arch bridges are still to be built in large quantities because of their unique advantages in aesthetics, economy, structure, and so on; the UHPC is expected to bring revolutionary change to arch bridges; in the aspect of span, the concrete arch bridges are expected to make more obvious breakthrough in the near future; the continuity, lightness and robustness of the deck system and its work together with main arch rib are also important development directions.More>
2020, 20(1): 27-41. doi: 10.19818/j.cnki.1671-1637.2020.01.002
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Review on temperature action and effect of steel-concrete composite girder bridge
LIU Yong-jian, LIU Jiang
Abstract: To understand the temperature action and effect of composite girder bridge in depth, the research status of domestic and overseas, including the temperature action and effect of hydration heat in construction stage, the temperature action patterns and finding values methods in the operation stage, and the calculation methods of temperature effect, was summarized and analyzed. The subsequent research emphases and directions were discussed. Research result shows that the hydration heat temperature effect is an important reason for the early cracking of decks in cast-in-situ composite girder bridges. The accurate selection of applicable hydration heat model and the consideration of the effect of temperature history on the elastic modulus and tensile strength of hardening concrete and the connection stiffness of studs are the keys to accurately calculate the hydration heat temperature effect of composite girder. Three temperature action patterns, including uniform temperature, positive and negative temperature gradients, are generally taken into consideration on the composite girder bridge in the operation environment. The specifications of temperature action patterns and values of composite girder bridges are not coincident due to the differences in climate environments and research histories in different countries. Additionally, the temperature gradients are not obtained based on the statistical analysis and the existing historical meteorological data resources are not fully utilized. The temperature effect calculations of composite girder bridges are mostly based on the finite element numerical simulation. The analytical calculation methods for solving the temperature effect of composite girders are also improved, from taking no account of the interfacial slip and simple steel-concrete uniform temperature difference to considering the interfacial slip and arbitrary temperature distribution of steel and concrete. However, the theoretical model for solving the temperature effect of composite girder with arbitrary boundaries should be strengthened. The future research directions of composite girder bridge temperature problem should focus on the composite girder temperature action pattern based on effect classification, the in-depth understanding the temperature self-generated and secondary effects from the mechanism, and strengthening the long-term temperature measurement to determine the representative values of temperature actions by statistical analysis, as well as fully using the historical meteorological data of the meteorological departments in various regions of China to study the regional differences of the temperature action values.More>
2020, 20(1): 42-59. doi: 10.19818/j.cnki.1671-1637.2020.01.003
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Monitoringand evaluation of fatigue damage for orthotropic steel deck usingacoustic
DUAN Lan, WANG Chun-sheng, ZHAI Mu-sai, WANG Shi-chao, SI Hai-peng
Abstract: Based on the integration of multiple monitoring technologies, the fatigue damage was analyzed and assessed for the orthotropic steel deck(OSD), including the fatigue test of a fullscale OSD segment in lab and the fatigue damage monitoring of a cable-stayed highway steel bridge with the OSD during service stage.For the fatigue test study of the OSD in lab, two kinds of acoustic emission(AE)sensors, including physical acoustics corporation(PAC)commercial AE sensors and smart piezoelectric paint sensors made of lead-zirconate-titanate(PZT), and supplementary strain gages were comprehensively used to detect and monitor the fatigue crack activities before and after the cold reinforcement of bonding steel plate.For the in-service highway steel bridges with detected fatigue cracks in the OSD, the cold reinforcement of bonding angel steel was proposed for the fatigue sensitive details in the OSD.Both AE monitoring and strain monitoring were conducted to study the fatigue crack activity and verify the effectiveness of the cold reinforcement.Learn from the fatigue test and monitoring results in lab, both PAC commercial AE sensors and smart PZT sensors are efficient ways to capture the fatigue propagation signals that have the characteristic of a peak amplitude and then fading gradually.The application of both PAC commercial AE sensors and smart PZT sensors achieve smart monitoring for the fatigue crack activity.The PAC commercial AE sensor group can locate the fatigue crack propagation length and direction in the rib accurately.After adopting bonding steel plate, the stress level keeps at 64.8 MPa stably, and no fatigue crack propagation is observed untill the cyclic loading accumulates to 5.12million times, testifying fine workability of the OSD model after the cold reinforcement.The PAC commercial AE sensor and smart PZT sensor have good agreement in detecting fatigue crack propagation during fatigue loading process, and can capture more fatigue crack activity information in-time than the strain gage.Learn from the monitoring and evaluation results for the in-service steel bridge with the OSD, the peak energy of AE monitoring result before the cold reinforcement is 5times as that after the cold reinforcement, and the accumulated AE signals decreasing from intensive to scatter indicate the stability of fatigue cracks.After the cold reinforcement, the peak stresses nearby the fatigue crack tips decrease by 40%to 50%when the loading vehicles pass, and the maximum stress near the fatigue detail declines from 78MPa before the cold reinforcement to 48MPa after the cold reinforcement during 24hmonitoring.The peak energy and accumulated number of AE signals and the stress level testify the effectiveness of cold reinforcement for the fatigue cracks in the OSD.14figs, 31refs.More>
2020, 20(1): 60-73. doi: 10.19818/j.cnki.1671-1637.2020.01.004
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Frequency domain analysis for maximum displacement response of bridges excited by single moving load
LI Jin-hua, ZHANG Huan-tao, LIU Quan-min
Abstract: To establish the relationship between the operation speed of train and the maximum displacement response of bridge more effectively, a frequency domain analysis method was proposed for the maximum displacement response of bridge excited by a single moving load. The Fourier transform was used to derive the moving load spectrum and the vibration displacement response spectrum of bridge when a single moving load passing through the beam bridge at a constant speed. The moving load speed causing the extreme free vibration displacement response of bridge was obtained by analyzing the moving load amplitude spectrum, and a calculation formula for the moving load speed was proposed. Taking a simply-supported beam as an example, the correctness of numerical calculation procedure in this paper was verified by comparing with the results of related literatures. Based on this procedure, the correctness of theoretical derivation of frequency domain analysis method and the accuracy of moving load speed formula were verified through the numerical analysis. Research result shows that the moving load amplitude spectrum obtained in the frequency domain is consistent with the amplitude response law of free vibration of bridge obtained in the time domain, so the moving load amplitude spectrum can effectively reflect the free vibration displacement response of bridge. The moving load speed corresponding to the maximum free vibration displacement response of bridge is equal to that corresponding to the maximum amplitude spectrum of moving load, and the moving load speeds corresponding to other extreme points of moving load amplitude spectrum are also consistent with those of the extreme points in the free vibration displacement response of bridge. In the free vibration phase, the speed of single moving load correeponding to the extrem point of displacement response of bridge is only related to the natural frequency and span of bridge. When a single moving load passes through a bridge at the resonant speed, the responses of forced and free vibration displacements are not the maximum response. Therefore, for the train operation speed of high-speed railway bridges, in addition to the resonance speed of train, more attention should be paid to the speed causing the maximum displacement response of bridge.More>
2020, 20(1): 74-81. doi: 10.19818/j.cnki.1671-1637.2020.01.005
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Impacts of initial internal force and geometric nonlinearity of suspension bridge on bridge-rail interaction
XIE Kai-ze, ZHAO Wei-gang, CAI Xiao-pei, LIU Hao, ZHANG Hao
Abstract: Based on the theory of bridge-rail interaction, an approach to reconstruct the displacement-force curve of ballast longitudinal resistance was put forward according to the deformation of suspension bridge under the completed bridge state. A feasibility study on the reconstructing approach was conducted via two aspects of the force and deformation of continuous welded rail(CWR) on a 5×32 m simply supported beam bridge with initial deformation. With the multi-element modelling method and the U.L. formulation method, a rail-girder-hanger-cable-pylon spatial calculation model was established considering the initial internal force and geometric nonlinearity of suspension bridge. Taking a(2×84+1 092+2×84) m long-span suspension bridge as an example, the impacts of initial internal force and geometric nonlinearity of suspension bridge on the bridge-rail interaction under different working conditions were comparatively analyzed. Analysis result shows that the approach put forward to reconstruct the ballast longitudinal resistance can avoid the impact of initial deformation of bridge on the bridge-rail interaction, and make it possible to consider the effect of initial internal force on the bridge-rail interaction. The impact of main cable sag effect on the bridge-rail interaction is less than 1% under each working condition, so the factor can be neglected. The initial internal force of suspension bridge plays an important role under the bending, braking and rail breaking conditions. It can reduce the bending force, braking force and rail broken gap by 22.4%, 12.7% and 9.3%, respectively. The large displacement effect can not only change the distribution law of bending force, but also can significantly reduce the rail broken gap by 22.4%. It is suggested to consider the initial internal force and large displacement effect of suspension bridge under the bending, braking and rail breaking conditions of CWR on suspension bridges. The suspension bridge can be simplified as a continuous beam bridge with a longitudinal constraint at the mid-span and expandable beam ends at both sides under the expansion and contraction condition. The established calculation model can provide accurate simulation results for the design of CWR on suspension bridges.More>
2020, 20(1): 82-91. doi: 10.19818/j.cnki.1671-1637.2020.01.006
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Improved algorithm of cable force for one-time cable tensioning on steel tube arch ribs with segmental hoisting
ZHOU Qian, ZHOU Jian-ting, MA Hu, LI Xiao-gang, ZHANG Lan
Abstract: To improve the defects of low iteration efficiency, long calculation time and neglecting the influence of temperature change of common calculation methods for cable force of long-span steel tube arch ribs during the segmental hoisting, an improved algorithm considering the influence of temperature change and improving the calculation efficiency was established. Based on the knowledge of material mechanics and geometry, the theoretical relationship between the changes of arch rib displacement and temperature during the hoisting was deduced, and the theoretical relationship between the changes of cable force and temperature was deduced considering the changes of cable length and arch rib displacement caused by the temperature change. Based on the one-time cable tensioning method and the zero order optimization method in ANSYS, a calculation program of cable force was developed considering the influence of temperature change and implementing the macro-control on the automatic search in the iteration sub step. The construction control analysis of segmental hoisting for a concrete filled steel tube arch bridge with a main span of 300 m was carried out with the improved algorithm. Analysis result shows that the results of derived theoretical formula are consistent with the change rules of finite element analysis results. The maximum relative error of displacement change of arch rib is 11%, and the maximum relative error of cable force change is 18%, both can meet the engineering accuracy requirements. Comparing with the original algorithm, the iteration number reduces from 26 to 17, the iteration efficiency increases by 35%, and the maximum deviation of cable force between the calculated and measured values reduces from 276 kN to 100 kN. The maximum deviation of arch rib displacement between the theoretical and the measured values is 7 mm after loosening cables and arched, and the arched alignment is normal. The established improved algorithm can realize the one-time cable tensioning and improve the iteration efficiency and calculation accuracy. The arch rib alignment after loosening cables and arched can meet the design requirements when using the improved algorithm to control the hoisting construction of long span steel tube arch rib.More>
2020, 20(1): 92-101. doi: 10.19818/j.cnki.1671-1637.2020.01.007
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Research progress on wheel polygons of rail vehicles
ZHU Hai-yan, HU Hua-tao, YIN Bi-chao, WU Ping-bo, CENG Jing, XIAO Qian
Abstract: Aiming at the problem of wheel polygons common to rail vehicles, the effects of wheel polygons on the dynamics performance of rail vehicles were described from the aspects of rail vehicle stability, curve passing ability, and stability, and the impact of wheel polygons on the vehicle-track system components was evaluated from the perspective of fatigue life.The formation mechanism of wheel polygon was classified based on the research of wheel-axle and track structural characteristics, wheel-rail dynamic effect, wheel materials and processing technology. The existing methods of wheel polygon detection and control were summarized by summarizing the influence of wheel polygons and their causes. The research prospects of wheel polygons were proposed to provide a reference for the subsequent research on wheel polygons. Research result shows that the wheel polygon will threaten the stability of vehicle system, reduce the curve passing performance and vehicle stability, affect the passengers' comfort, and cause resonance fatigue damage to vehicle-track components. The wheel-axle resonance is one of the causes of low-speed vehicle wheel polygons. The response of rails under the external excitation and local modes are also necessarily related to the formation of wheel polygons. The wheel-rail friction vibration is generally applicable to explain the generation of wheel polygons for all rail vehicles. The wheel's own material characteristics and manufacturing repair process are also potential factors to reduce the wheel polygon phenomenon. Dynamic and static detections are one of the methods to deal with the wheel polygon phenomenon. In addition, the wheel polygon phenomenon can be controlled by optimizing the structure of vehicle-track system, strengthening the wheel production process, and timely correcting the roundness of wheel tread. Wheel repair is still the most direct means to deal with the wheel polygon, and the repair process should be improved.More>
2020, 20(1): 102-119. doi: 10.19818/j.cnki.1671-1637.2020.01.008
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Numerical simulation of initial compression wave characteristics of 600 km·h-1 maglev train entering tunnel
MEI Yuan-gui, ZHAO Han-bing, CHEN Da-wei, YANG Yong-gang
Abstract: In order to analyze the characteristics of initial compression wave generated when a high-speed maglev train enters a tunnel, the three-dimensional compressible unsteady flow N-S equation and the SST κ-ω turbulent flow model were used. Based on the overlapping grid method and the finite volume method, taking the head shape of a high-speed maglev train with a speed of 600 km·h-1, which was developing in China as a research object, a calculation model of a high-speed maglev train entering a tunnel was established. By analyzing the pressure and pressure change rate at different measuring points on different cross sections from entrance of tunnel, the spatial distribution characteristics and propagation characteristics of initial compression wave when the train heads enter into the tunnel opening were obtained, and the effect of different speeds on the amplitude of initial compression wave fluctuation were also obtained.Research result shows that the initial compression wave starts to form before the train enters the tunnel. It has three-dimensional characteristics at the initial stage of formation. At the same height of the tunnel cross section, the pressure of initial compression wave on the side closer to the train body is greater than the pressure on the side farther from the train body. On the same side of the tunnel cross section, the lower the height near the train body, the higher the pressure of initial compression wave, but the pressure of initial compression wave on the side far from the train body is independent of the height. When the train enters the tunnel for a certain distance at the position about 36 m in front of the train head, the pressure at the same section in the tunnel is the same, and the initial compression wave changes from a three-dimensional wave to a one-dimensional plane wave. When the streamlined head of train enters the tunnel at about 0.15 m, the pressure change rate of initial compression wave at the 300 m measuring point at the tunnel reaches the maximum value. The higher the train speed, the greater the peak pressure of the initial compression wave. The peak pressure of initial compression wave at the 100 m measuring point at the tunnel is approximately proportional to the 2.5 th power of the train speed, and the peak pressure change rate is approximately proportional to the 3 rd power of the speed.More>
2020, 20(1): 120-131. doi: 10.19818/j.cnki.1671-1637.2020.01.009
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Wind tunnel experiment on aerodynamic characteristics of high-speed train-bridge system under crosswind
ZOU Si-min, HE Xu-hui, WANG Han-feng, TANG Lin-bo, PENG Tian-wei
Abstract: To study the aerodynamic characteristics of a high-speed train in operation and analyze the mechanism of aerodynamic characteristics change, two wind tunnel experimental schemes for aerodynamic characteristics of the high-speed train-bridge system were designed. A high-speed train-bridge test method and system appropriate for wind tunnel were developed and established. The system consisted of two parts including the motion system and the data acquisition system. The motion system was based on the inertial drive mechanism, the high-speed servo motor served as the power, through the high strength rotary conveyor belt, and the moving vehicle model with a scale ratio of 1∶8-1∶30 with a maximum speed of around 50 m·s-1could run in the wind tunnel to simulate the real operating environment.Taking the motion system as the carrier, a set of data acquisition systems was developed for measuring the aerodynamic characteristic of trains with or without the crosswind in the wind tunnel. Analysis result shows that the experimental method and system can be applied to the test scenarios with a short acceleration-deceleration distance and the high instantaneous acceleration. The system is not only free from the shape of vehicle and infrastructure but also reduces the design cost and improves the safety and stability of test.The standard error-mean value ratios are less than 10%, which shows that the aerodynamic characteristics of the train tested by the data acquisition system have good stability and repeatability, the aerodynamic characteristics of train in different tests can be obtained accurately. By comparing the test of train with or without the crosswind, the impact of speed of moving train on the aerodynamic is extremely important.While the train running at high speed, the aerodynamic effects due to the speed of train are much larger than the crosswind, and the mean wind pressure coefficient is up to-10, which reflects that the static model test method can not meet the requirements of the simulation of the aerodynamic characteristics of the train in high-speed operation.More>
2020, 20(1): 132-139. doi: 10.19818/j.cnki.1671-1637.2020.01.010
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Continuous velocity and location detection method of maglev vehicle based on cross inductive loop
REN Yu, CHEN Jian-zheng
Abstract: The spatial magnetic field distribution in the cross loop region was analyzed, and the vehicle displacement and velocity were characterized by the phase angle and angular velocity of the induced voltage envelope signal based on the longitudinal distribution and periodicity of magnetic flux density. The state-space equations of vehicle speed and location detection using simple cross loop were established, and the location and speed of the vehicle were taken as state variables outputted continuously during the test. Considering the complicated electromagnetic environment under the actual operating condition, the noise adaptive algorithm was introduced, and the real-time continuous speed and location detection calculation method of maglev vehicle based on the innovation adaption was proposed. The cross induction loop calibration system was established under laboratory condition, and the basic principle of the method was verified. In order to verify the effectiveness and accuracy of the method, numerical simulation analysis was carried out considering the normal and abrupt noise conditions, and the calculation results in the processes with and without adaptive noise were compared. Experimental result shows that at different interval distances, the induced voltage envelopes are close to the sinusoid. The first harmonic is the main component of the envelope signal, and the harmonic amplitude of the same order is approximately linear with the interval distance, which is consistent with the theoretical analysis result. In the normal noise section, the speed error is no more than 0.03 m·s-1, and the location error is about 3 mm. While in the abrupt noise section, the mean value and maximum value of velocity errors are 0.027 and 0.130 m·s-1, respectively, and the mean value and maximum value of location errors are 4.82 and 23.39 mm, respectively. It means that the speed and location detection method can meet the actual application requirement. The low signal-to-noise ratio(SNR) signal in the abrupt noise section in the numerical simulation is an extreme case in the practical application. Comparing the calculation results of normal and abrupt noise sections, improving the SNR of the input signal can obviously improve the measurement accuracy.More>
2020, 20(1): 140-149. doi: 10.19818/j.cnki.1671-1637.2020.01.011
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Theoretical model and calculation of static leakage for train air tightness
LI Tian, DAI Zhi-yuan, ZHANG Ji-ye, ZHANG Wei-hua
Abstract: Based on the one-dimensional isentropic flow theory, the state equations of static leakage for the train air tightness were derived. The calculation formulas for the leakage time of pressure drop and the total leakage time were obtained considering the flow coefficient of leakage hole. The dynamic process of static leakage for the train air tightness was numerically simulated. The effects of slenderness ratio of leakage hole and the initial air pressure inside the car body on the train air tightness were studied when the slenderness ratios are 1∶1, 1∶4, 1∶8, and 1∶16, and the initial air pressures inside the car body are 6, 5, 4, and 3 kPa, respectively. Analysis result shows that the pressure drop times calculated by the numerical simulation and the theoretical formula are 20.25, 20.23 s, respectively, when the air pressure inside the car body drops from 3.0 kPa to 0.8 kPa, and the relative errors between them and the experimental results are 1.41% and 1.51%, respectively. When the slenderness ratios of leakage hole are 1∶8 and 1∶16, the time history curves of air pressure drop inside the car body are basically the same, and the air flow rate of leakage hole remains unchanged. During the leakage process, the air flow velocity of leakage hole shows the distribution characteristics of large in the middle and small around. This is caused by the viscous effect of leakage hole wall surface. According to the central velocity and mass flow rate at the outlet section, the flow coefficient of leakage hole is 0.71. The effect of initial air pressure inside the car body on the same specified pressure drop time is less than 1%. If the pressure drop range is the same, the pressure drop time decreases with the increase of initial air pressure, the time for the pressure to drop from 4 kPa to 1 kPa is 24.18 s, and the time for the pressure to drop from 5 kPa to 2 kPa is 19.80 s. The maximum relative error between the results of numerical simulation and the theoretical calculation is 1.22%, indicating that the theoretical model and numerical simulation calculation method can be applied to calculate the leakage area or the air tightness of train.More>
2020, 20(1): 150-158. doi: 10.19818/j.cnki.1671-1637.2020.01.012
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Bending-torsional coupling vibration characteristics of EMU traction motor rotor system under combined loads
ZHOU Sheng-tong, ZHU Jing-wei, ZHOU Xin-jian, QI Qiang
Abstract: To investigate the bending-torsional vibration mechanism of EMU traction motor rotor and identify their typical fault features under the action of combined loads, the rotor structure was lumped into a rigid-disk-massless-shaft system according to the actual structure configuration of EMU traction motor, and a bending-torsional mechanical model of motor rotor system with ten degrees of freedom was established. The differential equation of bending-torsional coupling motion of traction motor rotor system was built by using Lagrange's equation method under the action of multiple radial and torsional loads, such as the unbalanced magnetic pull caused by the static and dynamic air-gap eccentricity, the mechanical unbalanced force caused by the mass eccentricity, the rotor gravity, the driving torque and the load torque of motor. The bending-torsional vibration characteristics of rotor system under different combined load cases were calculated and analyzed based on the Runge-Kutta method. Analysis result shows that the coupling relationship of bending and torsional degrees of freedom caused by the mass eccentricity of rotor makes the bending and torsional vibration characteristics of traction motor rotor system affected mutually by the radial and torsional loads of rotor, and the influence results conform to the law induced by the mass eccentricity coupling of rotor.Under the action of all radial and torsional loads, the radial vibration of traction motor rotor includes the frequency components such as the zero frequency, the rotation frequency, the double rotation frequency, the bending natural frequency, the double power frequency and its combinations with rotation frequency, the combination of pulsating torque frequency and rotation frequency, and so on, and among them the bending vibration amplitude corresponding to the rotation frequency component is the largest, while the vibration amplitude of the combination of pulsating torque frequency and rotation frequency is very small, which means that the contribution of pulsating torque to the radial vibration of traction motor rotor is not obvious. The torsional vibration of traction motor rotor under the action of all loads consists of the frequency components such as the rotation frequency, the double rotation frequency, the combination of bending natural frequency and rotation frequency, the combination of double power frequency and rotation frequency, and the pulsating torque frequency, and so on, and among them the torsional vibration amplitude corresponding to the pulsating torque frequency is the largest, and the torsional vibration amplitude corresponding to the rotation frequency caused by the gravity and unbalanced magnetic pull is also larger, and both them basically have the same order of magnitude, which means that their contributions to the torsional vibration cannot be ignored.More>
2020, 20(1): 159-170. doi: 10.19818/j.cnki.1671-1637.2020.01.013
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Effect of service temperature on static failure of BFRP/aluminum alloy adhesive joints
TAN Wei, NEI Jing-xin, MU Wen-long, QIN Guo-feng, SHEN Hao
Abstract: In order to predict the static failure behavior of BFRP/aluminum alloy adhesive joint under service temperature in the process of vehicle lightweight design, the adhesive joints under three different stress states were manufactured, including tensile stress state, shear stress state and combined tension-shear stress state, five temperature measuring points of-40 ℃, -10 ℃, 20 ℃, 50 ℃ and 80 ℃ were selected according to the characteristics of vehicle service temperature, the change rules of adhesive joint failure strength with service temperature under different stress states were obtained based on the quasi-static tensile test, and the failure forms and failure criteria of adhesive joints were analyzed. Based on the tensile and shear stresses of adhesive joints at different service temperatures, the quadratic stress failure criterion equations of the joints were established to predict the failure strengths of the joints at different service temperatures. Analysis result shows that the failure strength of the adhesive joint is obviously affected by the service temperature, and the failure strength decreases with the increase of the service temperature. The different proportions of shear stress and tensile stress in the adhesive joint will also have a certain impact on the failure strength of the joint, and the failure strength of the joint will decrease more obviously with the increase of the service temperature at greater shear stress proportion. Compared with the service temperature-40 ℃, the failure strengths of tensile and shear joints decrease by 47.77% and 61.49% at 80 ℃, respectively. With the increase of the service temperature, the failure stress and Young's modulus of the adhesive decrease gradually, while the failure strain increases gradually, which shows that the service temperature affects the mechanical properties of the adhesive greatly. The failure mode of the adhesive joint is the mixture failure of cohesion and fiber tearing. Under the action of tensile stress, the joint is more prone to fiber tearing. With the increase of the service temperature, the fiber tearing area decreases. In order to prevent fiber tearing, it is necessary to avoid the effect of tensile stress on the adhesive joint. The fitting accuracies of the quadratic stress failure criterion curves of the adhesive joints at different service temperatures are more than 0.957, therefore, the drawn response surface of failure criterion can reflect the change rule of failure strength of the adhesive joint at the service temperature of vehicle.More>
2020, 20(1): 171-180. doi: 10.19818/j.cnki.1671-1637.2020.01.014
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Physiology, psychology and comprehensive loading perception models of cyclists
LI Cong-ying, SHAO Zhuang-zhuang, FENG Shao-shuai, WANG Xiao-kun, JIA Jin-xiu, TAN Qian
Abstract: In order to explore the influence mechanisms of cyclists' physiological and psychological states on the individual attributes, cycling intensity and environment during the cycling process, the cycling experiment was designed and implemented. The relative metabolism rate, mood state, self-induced fatigue and task load index were selected to analyze the features and mechanisms of the cyclists' physiological, psychological and comprehensive loading perception. Based on the cycling experiment data, the physiological, psychological and comprehensive loading perception models were established by partial least-squares regression method, and the forecasting abilities of the models were also tested. Analysis result shows that cyclists' individual attributes, cycling intensity and environment all have impacts on cyclists' loading perception. Body mass index and basal metabolic rate play significant roles in individual attribute factors of cyclists, the average influence factors in the loading perception model are 0.121 and 0.112, respectively. Cycling time has the largest influence on loading perception among the cycling intensity factors, with an average influence factor of 0.139. Among the cycling environmental factors, the number of intersections has the most significant influence on cycling loading perception, with an average influence factor of 0.137. Each variable has the same influence tendency on psychological load and comprehensive load perception, but has different influence tendency on physiological load and comprehensive load. Therefore, paying more attention to some factors and the psychological load of cyclists has certain effects on improving the service level of cycles, and the research results can be applied to improve the environment of cycling facilities.More>
2020, 20(1): 181-191. doi: 10.19818/j.cnki.1671-1637.2020.01.015
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Optimization of differentiated service level for multi-level customers
HAN Xun, ZHANG Jin
Abstract: Based on the premise that satisfaction degrees of customers were affected by the current supply factors and the past service experience, a customer utility function was set up considering the effects of multiple factors such as distance, service level and price under the reference effect. Comparing the utility of customers in different companies, a probability model was introduced to characterize customers' selection behaviors. The correlation function between service level and unit service cost was proposed, and the service level optimization model of maximizing profit was constructed and solved. Taking the pickup service level in a specific business circle as an example, the impacts of sensitivity coefficient for service level and the competing company strategy on the optimization results were compared and analyzed. Research result shows that when the sensitivity coefficient changes from 0.2 to 1.0, a high service level provided by the target company leads to a 7.2% increase in demand coverage and a 10.4% increase in total profit. When the competing company adopts a service level strategy of 0.2 and a price strategy of 1.2, the target company provides a service level of 0.39 higher than the competing company to attract customers, and increases unit revenue through high prices. When the competitor company adopts a service level strategy of 0.8 and a price strategy of 1.8, the target company rises the service level from 0.59 to 0.63 to cope with competition, and maintains low price to retain some price-sensitive customers. When the competitor company adopts a service level strategy of 0.2 and a price strategy of 1.8, the target company improves market coverage by providing a service level of 0.47 higher than that of the competitor, and guarantees profit margin by a quite similar price. When the competitor company adopts a service level strategy of 0.8 and a price strategy of 1.2, the target company provides relatively low service level and price to control cost and maintain market share.More>
2020, 20(1): 192-203. doi: 10.19818/j.cnki.1671-1637.2020.01.016
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Optimization of arterial green-wave considering turning tram lines
WANG Hao, LI Chang-ze
Abstract: In order to make up for the lack of ability to optimize the arterial green-wave including trams, an arterial green-wave optimization model based on the multipath green-wave model was proposed, and the efficiency and independent operation of the arterial turning trams and the through social vehicles were ensured. The coordination relationship between the signal phases of tram line and the arterial social vehicle was determined, and the basic constraints of arterial green-wave model were constructed. Considering the acceleration and deceleration characteristics of tram stopping process, as well as the clearance time requirements when passing through the intersection, a supplementary constraint condition for the tram was established. The phase sequence control variables were set, the solution space was enlarged, and the modeling ability of arterial green-wave optimization model was improved. The travel time variables were set to ensure that social vehicles travel within the safe speed specified on the road section, ensure the unity of the total travel time of outbound and inbound trams, and ensure the efficient and reasonable schedule operation. Under the condition of meeting the basic requirements of green-wave bandwidth of trams, an objective function for maximizing the green-wave bandwidth of social vehicles was constructed. The arterial green-wave optimization model was used to optimize the coordination of traffic signals at 4 intersections along the arterial section of Nanjing Qilin Town tram. Research result shows that the arterial green-wave optimization method can optimize the phase sequence of signals at intersections, and provide for trams a green-wave with a turning phase. The optimized arterial signal cycle is 142.4 s, the phase differences between intersections are 0, 116.8, 52.0, 5.7 s, the green-wave bandwidth of unidirectional social vehicles is 26.6 s. The green signal ratio of outbound and inbound social vehicles reaches 37.4%, and the green-wave bandwidth of tram is 10 s, which meets the traffic requirements of artery system.More>
2020, 20(1): 204-214. doi: 10.19818/j.cnki.1671-1637.2020.01.017
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Effectiveness experiment of sight induction facilities of curve sections in highway tunnel
DU Zhi-gang, NI Yu-dan, YANG Li-bo, WEN Jing-zhou, YU Xin-yu
Abstract: The influence of reflective ring number at highway tunnel curve sections with different radii on the driver's curvature perception was analyzed. Aiming at two typical sight induction schemes based on chevron alignment signs and reflective rings, the laboratory simulation experiment was conducted by driving simulator. The driver's curvature perception was measured by testing curve illusion degree and reaction time, and the test data were analyzed by the software of Origin. Analysis result shows that, before the improvement, drivers overestimate the radii by more than 35%, and the reaction times are not less than 5.46 s. When using 3 chevron alignment signs, the curve illusion degrees and reaction times at different radii slightly decrease. The curvature induction effect is good at a radius of 400 m, and the curve illusion degree is 6.12%, which means that the chevron alignment signs can improve the driver's curvature perception, but the improvement effect is not significant. When using 3 reflective rings, the curve illusion degrees at different radii are less than 5%, and the reaction times are more than 37% lower than before, which means that 3 reflective rings can effectively improve the driver's curvature perception and control the reaction time within a reasonable range. Based on the logistic function fitting analysis, the inflection points of the fitting curves between the curve illusion degrees and the number of reflective rings at different radii are close to 3 where the curve illusion degree is the lowest. Meanwhile, the drivers' reaction times at different radii are inversely related to the number of reflective rings. When the reflective rings are more than 4, the reaction times show a convergence trend, indicating that increasing the number of reflective rings has a limited effect on reducing the reaction time. Therefore, it is recommended to use 3 reflective rings to induce the driver's sight at highway tunnel curve sections.More>
2020, 20(1): 215-225. doi: 10.19818/j.cnki.1671-1637.2020.01.018
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Empirical evaluation of travel survey based on mobile phone sensor data
YANG Fei, GUO Yu-dong, JIN J P, WU Hai-tao
Abstract: The mobile phone sensor and questionnaire were used to collect the real travel trajectories of college students on campus for 2 weeks. The characteristics of mobile phone sensor data in real travel environment were considered, and the Gaussian filter was applied to pre-process the data. According to the spatio-temporal clustering characteristics of trajectory points, the travel endpoints and travel times were identified by spatio-temporal clustering algorithm. Based on the characteristics of velocity and acceleration of trajectory points, the travel modes were identified by using support vector machine. Comparing the data of mobile phone sensor with the data of questionnaire and screen line, the accuracies of travel feature recognition of mobile phone sensor data were analyzed, and the extraction effect of travel feature was verified. Analysis result shows that the matching degree of travel chain between the mobile phone sensor and questionnaire is 81.66%, which indicates that mobile phone sensor data can effectively record the travel trajectory. When the spatial radius of the core point is 26.92 m, the minimum sample points are 129, and the time constraint is 129 s in the parameters of the spatio-temporal clustering algorithm, the travel endpoint and travel time identification accuracy are 93.02% and 90.84%, respectively, which indicates that the mobile phone sensor can identify the travel endpoint and travel time effectively. The accuracy of travel mode identification is 89.86% when the support vector machine type is classical, the kernel function is radial basis function, the penalty coefficient is 0.797, and the kernel parameter is 2.260, which indicates that mobile phone sensor can effectively identify the travel modes. Therefore, the recognition result of mobile phone sensor data is reasonable, which can support the application of mobile phone sensor data in actual travel survey.More>
2020, 20(1): 226-238. doi: 10.19818/j.cnki.1671-1637.2020.01.019
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