西南交通大学学报

Field Test and Analysis of Noise Reduction Performance of High-Speed Railway Semi-Closed Sound Barriers

LI Xiaozhen, ZHAO Qiuchen, ZHANG Xun, YANG Dewang

2018, 53(4): 661-669, 755. doi: 10.3969/j.issn.0258-2724.2018.04.001

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Abstract:
Semi-closed sound barriers are increasingly used in high-speed railway engineering, however, research on its noise reduction effect in operation is extremely limited. Based on the Shanghai to Kunming passenger line, noise measurement points were respectively arranged on the inner and outer surface of the semi-closed sound barrier, and the opened and closed sides, at different distances. Noise signals during high-speed train passing-by were monitored. Acoustic characteristics in terms of sound pressure level spectrum, sound field distribution, attenuation law, sound insulation and insertion loss were discussed. Results indicate that the reverberation effect caused by multiple reflections increases the noise on the inner surface of the semi-closed sound barrier; at a distance of 7.5 m from the track centerline, the sound pressure level of the higher measuring point is larger than that of the lower measuring point, and the directivity of the noise distribution is not evident for other measuring points at different heights. The sound insulation of the semi-closed sound barrier increases with the increase in frequency and reaches a peak of 26 dB at 1000 Hz; the insertion loss at a distance of 7.5 m and 25 m from the track centerline is 16.5 dB(A) and 15.5 dB(A), respectively.

Optimal Design of Corrugated Steel Deck Plate-UHPC Layer Composite Deck

ZHANG Qinghua, CHENG Zhenyu, LIAO Guixing, BU Yizhi, LI Qiao

2018, 53(4): 670-678. doi: 10.3969/j.issn.0258-2724.2018.04.002

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In order to solve the fatigue problem of orthotropic steel bridge decks, an innovative corrugated steel plate-UHPC (ultra-high performance concrete) layer composite deck structure is proposed based on the cause of the fatigue problems and the basic approaches used to improve the anti-fatigue performance. First, the major design parameters that significantly impact mechanical properties and the corresponding ranges of the parameter values were determined using parametric analysis. A model based on the BP artificial neural network was developed to determine the optimal design of the innovative structure system. Finally, the fatigue performance of the optimal structure was studied. The results show that the number of geometric discontinuity locations and weld joints are decreased, while the local stiffness of the deck plate is increased. According to the results of the parametric analysis, the height of the corrugated steel plate and the width of the top and bottom horizontal parts of the plate play important roles in structure mechanical characteristics. The proposed optimal design model based on the BP(back propagation) artificial neural network is suitable for the optimal design of innovative structure systems, and the maximum error is 4.4%. The innovative bridge deck has good fatigue performance, and its fatigue life is over 200 years, which provides a comprehensive solution to the fatigue problem and has good potential for further development and application.

Coupled Train-Bridge Vibration and Dynamic Characteristics of Long-Span T-Shaped Rigid Frame Railway Bridge

GOU Hongye, SHI Xiaoyu, ZHOU Wen, KANG Rui

2018, 53(4): 679-686. doi: 10.3969/j.issn.0258-2724.2018.04.003

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To study the characteristics of coupled train-bridge vibration and dynamic performance of a long-span T-shaped rigid frame railway bridge, taking the Mashuihe bridge on the Yichang-Wanzhou railway line as an example, a three-dimensional finite element model for coupled train-bridge vibrations was built, and each carriage of a train was modelled by a 31-degrees-of-freedom dynamic system. Field tests were conducted to determine the free vibration characteristics as well as the strain, displacement, and acceleration of the bridge structure under trains moving at different speeds and braking at a specified position from a set speed. Therefore, the dynamic responses of the Mashuihe bridge was studied comprehensively, both numerically and experimentally. The calculated results were in good agreement with the corresponding experimental results. The dynamic responses of the bridge satisfied the requirements of the code, and the bridge exhibited good lateral and vertical stiffness. The dynamic coefficients of the mid-span and the top of the pier was 1.08, which indicates that the impact of train braking has little effect on the bridge structure. The dynamic responses of the carriages increased with increasing speed, but also satisfied the requirements of the code. The carriages exhibited satisfactory safety and stability.

Flutter Mechanism of Flat Box Girder under Different Attack Angles

LI Zhiguo, WANG Qi, WU Bo, LIAO Haili

2018, 53(4): 687-695, 755. doi: 10.3969/j.issn.0258-2724.2018.04.004

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The effect of an additional attack angle induced by aerostatic force on flutter instability of long span bridges is significant, thus the study regarding the flutter mechanisms of a flat box girder under different attack angles is important and necessary. Flutter derivatives have been identified using forced vibration devices and the critical velocities have been calculated based on the bimodal coupled flutter analysis method. Based on this analysis scheme, the roles of aerodynamic damping, phase lag, and modal frequency, which aid to better understand the flutter mechanism of the girder under different attack angles, are intensively analysed. The study results indicate that uncoupled aerodynamic forces provide energy to enhance the stability of the systems that result in a higher critical flutter speed at 0° and 3° compared with the speed at 5° The negative aerodynamic damping induced by the coupled force increases rapidly while the positive damping provided by the non-coupled force decreases significantly at 5° attack angle, which results in the weakened flutter performance. The phase lag of coupled flutter is the primary parameter for increasing the negative damping, and the effect of aerodynamic amplitude is negligible. The mechanism indicates that the weakening flutter performance of a flat box girder at large attack angle is increased primarily owing to coupled motion, not induced by negative damping generated in the torsional flutter.

Earthquake Risk Assessment of Bridge Based on Failure Probability Method

HAN Xing, CUI Sheng'ai, CUI Enqi, SU Jiao, ZHU Bing

2018, 53(4): 696-703. doi: 10.3969/j.issn.0258-2724.2018.04.005

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To study the possibility of destruction of a high-speed railway continuous girder bridge under the influence of seismic damage, a seismic risk assessment of the bridge was conducted. The failure probability method was used, in which seismic risk is defined as the product of seismic hazard and fragility (i.e., seismic risk=seismic hazard×fragility). The bridge seismic demand model was established using the strip coating method. The bridge seismic fragility curve was obtained based on the reliability function, and the probability density function of the bridge fragility was fitted. According to seismic risk data of the bridge site, the probability density function of seismic acceleration of the bridge site was derived. The probability density function of seismic acceleration was numerically integrated with that of the bridge structural vulnerability to accomplish the probability evaluation of the bridge earthquake risk. Taking a (32+48+32) m high-speed railway continuous girder bridge as an example, the system conducted the bridge risk assessment using the failure probability method. The results show that when earthquake risk data are lacking or insufficient, it is possible to deduce and improve seismic risk analysis data using the conversion relation between the earthquake intensity distribution function and the seismic peak acceleration. For the high-speed railway (32+48+32) m continuous girder bridge, within 100 years of use, the occurrence probability of slight damage is 5.16% and that of secondary damage is 4.46%. The probabilities of slight damage and secondary damage risk of the bridge are similar, whereas the probabilities of serious damage and complete destruction are very small, indicating that serious damage and complete destruction are almost impossible.

3D Current-induced Local Scour around Dumbbell-Shaped Steel Suspending Cofferdams

DUAN Lunliang, WANG Shaohua, ZHANG Qibo, ZHENG Dongsheng

2018, 53(4): 704-711. doi: 10.3969/j.issn.0258-2724.2018.04.006

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To investigate the local scour around a cofferdam, a three-dimensional numerical model for current-induced sediment scour around a dumbbell-shaped steel suspending cofferdam was established. After its validation using previous experimental data, the proposed model was applied to explore the local scour around dumbbell-shaped steel suspending cofferdams under various conditions. The numerical results indicate that the flow field distribution around the cofferdam is very complex owing to the mutual influence of the cofferdam and the steel casings. In addition, the maximum scour depth occurs around the casing adjacent to the centreline of the cofferdam, which increases with increasing current velocity and draught; the scour plain patterns are similar to the shape of the cofferdam. The results of this study can provide new evidence for studies of soil stability, and can also provide a reference for predicting the scour pattern around coastal structures.

Vortex-Induced Vibration Performance of Wide Streamlined Box Girder and Aerodynamic Countermeasure Research

LI Ming, SUN Yanguo, LI Mingshui, WU Bo

2018, 53(4): 712-719. doi: 10.3969/j.issn.0258-2724.2018.04.007

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To suppress the vortex-induced vibration (VIV) of the wide streamlined box girder, the Qingshan Yangtze River Bridge (a long-span cable-stayed bridge with a wide streamlined box girder) was taken as an example. The study of the VIV performance was carried out through a 1:50 scale section model wind tunnel test. The VIV performance of the girder was studied in a low-damping condition, as well as the effects of various countermeasures on such performance, including wind fairing, inspection vehicle rail, guide vane, vibration mitigation plate, and maintenance way railing. The test results show that a sharp wind fairing is favourable to the VIV performance of the girder. The position of the inspection vehicle rail, the height of rail supporter, and the guide vane slightly suppress the VIV response. The vibration mitigation plate, which was installed behind the anti-collision railing such that five seals off one, can reduce the vertical VIV displacement by 45%. The circular maintenance way railing and the high ventilation rate can improve the VIV of the wide streamlined box girder significantly. In particular, the displacement was reduced by 63%. The recommended railing style does not affect the aesthetic of the bridge and is convenient to apply. A 1:27 scale section model test was conducted to verify the countermeasure. The test results show that the recommended maintenance way railing can suppress the VIV of the wide streamlined box girder effectively.

Study On the Crack Plastic Zone of Bridge Structure Steel and Its Application

QU Yu, GU Anbang, ZENG Yong, DU Baisong

2018, 53(4): 720-726. doi: 10.3969/j.issn.0258-2724.2018.04.008

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In order to study the influence of crack plasticity on crack growth, the shape and size of crack tip plastic zone of bridge steel were calculated by using engineering simplification algorithm, the stress function method and extended finite element method respectively. As a result of the cyclic plasticity of wake field under plane stress and plane strain being different, cyclic plasticity and plastic accumulation of crack tip and wakes were simulated and analyzed by using the discontinuous extended finite element method. The formation of crack tip plastic zone, cyclic plastic zone and the mechanism of compressive stress of wake field were studied. The results showed that the appearances and sizes of plastic zone at the crack tip were proportional to the square of the stress level (the ratio of nominal stress to the yield limit). When the stress level was greater than 0.4, the size of the crack tip plastic zone had to be taken into account the effect of the stress level. The butterfly-shaped crack tip plastic zone symmetrically extended forward, shielding the tensile force of the crack tip high stress field on the wake field, which was beneficial to crack closure. There exists reverse flow of material in plastic zone of crack tip. The compressive stress effect induced by the plastic accumulation on the crack surface was beneficial to the crack closure in advance. Crack closure produced by plasticity had an important influence on the retardation of crack extension in the case of variation load and overload.

Experimental Study on Lateral Resistance of Optimized Ⅲc Sleeper with Different Frame Types

JING Guoqing, FU Hao, JIA Wenli, YAO Li, LIN Hongsong

2018, 53(4): 727-732. doi: 10.3969/j.issn.0258-2724.2018.04.009

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To optimize the geometry of the Ⅲc mono-block sleeper and reveal the variation characteristics of the ballast bed lateral resistance before and after optimization, three different frame sleepers were designed and fabricated by adding concrete blocks to specific parts of the Ⅲc mono-block sleeper. Based on the ballast bed lateral resistance test, The frame sleepers and Ⅲc mono-block sleeper were compared for different ballast bed cross-sections (shoulder width 300 mm, shoulder height 0 mm; shoulder width 500 mm, shoulder height 0 mm; shoulder width 500 mm, and shoulder height 150 mm). The study shows that each frame sleeper can effectively increase lateral resistance with different ballast bed cross-sections. Furthermore, compared with the Ⅲc mono-block sleeper, there is 37.8%-50.0% increase in lateral resistance for frame sleeper type A(end-winged sleeper), 25.5%-41.0% increase for frame sleeper type B(middle-winged sleeper), and 13.3%-23.0% increase for frame sleeper type C(bumped sleeper).

Analysis of Track Irregularity Time-Frequency Characteristics Based on Empirical Mode Decomposition

YANG Youtao, LIU Guoxiang

2018, 53(4): 733-740. doi: 10.3969/j.issn.0258-2724.2018.04.010

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The measurement of high-speed railway track irregularities is a complex stochastic process, in which many single-component signals of different frequencies and amplitudes are present. In order to analyse the distribution characteristics of track irregularities in the spatial and frequency domains, the Hilbert-Huang transform was used to extract the energy distribution of track irregularity in the time-frequency domain. Track irregularity data was first decomposed into amplitude-frequency modulated multivariate intrinsic mode functions (IMF) at different scales, based on the data-driven filtering characteristics of multivariate empirical mode decomposition (MEMD). The instantaneous frequency of multivariate IMFs at each scale was then calculated by means of a Hilbert transform, from which the frequency and energy distribution characteristics were analysed. The analysis of the track inspection car indicates that the frequency distribution of track irregularities exhibits a characteristic of quasi-dyadic filter banks and that the frequency bandwidth is narrow at each scale. The energy distribution of the track irregularity and corresponding wavelengths can be determined from MEMD-based scalograms at different scales. In the sample track irregularity data, the energy of the gauge and cross level is mainly distributed in the medium and long wavelength frequencies. The energy of the alignment and profile is concentrated in the wavelengths between 4 and 36 m, and the energy of the twist is distributed in two wavelengths of 4.9 m and 7.6 m.

Static Contact Analysis of Worn-Wheel Profiles and 60N Rail of High-Speed Railway

MA Xiaochuan, WANG Ping, WANG Jian, XU Jingmang

2018, 53(4): 741-747. doi: 10.3969/j.issn.0258-2724.2018.04.011

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Over time, the running of vehicles results in different degrees of wear on the wheel treads. To study the static matching characteristics between the worn wheel and the rail, the wheel-rail contact geometry relationship and non-Hertz rolling contact theory were used to analyse the effects of worn-wheel profiles on the wheel-rail contact geometry parameters and contact behaviour. The results were compared with those of CHN60 rail and analysed. The results indicate that when the lateral displacement of the wheel set is less than 4 mm, the degree of wear on the wheel is greater, and the lateral distribution width of wheel-rail contact points on the wheel is larger. The lateral distribution width of the wheel-rail contact points of 60N rail is significantly less than that of the CHN60 rail, thereby improving the vehicle's running stability. The wheel-rail wear index increases with the degree of wheel wear. The wheel-rail wear index of 60N rail is smaller, which improves the ability to maintain the wheel-rail profile. A greater degree of wheel wear corresponds to a greater surface rolling contact fatigue area. Compared with CHN60 rail, the number of cases located in the area of surface rolling contact fatigue of 60N rail is less, which can reduce the rolling contact fatigue damage under the same conditions.

Control Mode of Waterway Traffic under Dangerous Mountain Landslide Conditions

CHENG Zhiyou, WANG Pingyi, YANG Chengyu, WANG Shixian, ZHENG Jie, LI Yaling

2018, 53(4): 748-755. doi: 10.3969/j.issn.0258-2724.2018.04.012

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The control mode of waterway traffic under dangerous mountain landslide conditions was studied to safeguard ship navigation and enhance the transportation efficiency of water channels. Large-scale surge generated by paroxysmal mountain landslides was considered based on a considerable amount of case data, conclusions from physical model experiments, conclusions from consulting the literature, and data from practical investigation. The occurrence probability of mountain landslides was estimated according to the stage of landslides deformation and effects of external environmental forces. The maritime risk caused by mountain landslides was assessed according to the stage of landslides deformation, the scale of the surge generated by mountain landslides, and effects of external environmental forces and restricted environmental conditions on ships. The control mode of waterway traffic, which included forms of traffic control and prohibited levels of ship traffic, was designed based on evolving traits of maritime risk. The form of traffic control should depend on the estimated occurrence probability of mountain landslide, and the prohibited level of ship traffic should depend on maritime risk caused by the mountain landslide. A case study shows that, when the occurrence probability of a mountain landslide is 0.6 and the maritime risk of a mountain landslide is 1.80, the alert mode of traffic control must be adopted. When the occurrence probability is 0.6 and the maritime risk is 2.25, the mode of traffic control with a definite ship flow form must be adopted. When the occurrence probability is 0.72 and the maritime risk is 2.16, the mode of traffic control with definite ship objects and definite time must be adopted; when the occurrence probability is 0.72 and the maritime risk is 2.70, the prohibited mode of traffic control is necessary.

Stability Analysis of Slope with Complex Spacial Shape

WU Xiaofei, YANG Tao, WU Kunlu, LI Hui, AI Yang, SHEN Shaohua, WANG Ying

2018, 53(4): 756-761. doi: 10.3969/j.issn.0258-2724.2018.04.013

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Based on the three-dimensional point safety factor, a three-step point safety factor approach is proposed using three-dimensional numerical analysis to evaluate the stability of slope with complex spacial shape. First, the displacement field of slope in critical state is calculated with the reduced shear strength parameters of slope mass to obtain the critical state or large deformation state of slope using the strength reduction method. Second, the stress field of slope in current state is calculated by setting actual physical and mechanical parameters of slope mass. Finally, point safety factors of slope are obtained according to results of the displacement field in critical state and the stress field in current state. The proposed method is applied in the high slope project along the transportation road at Zhenfeng Coal-Fired Power Plant, Guizhou Province. It is shown that, the global safety factor of the unreinforced high slope is greater than the design value of 1.35, but the local safety factor at the toe is less than the design safety factor. Also, the local stability of the slope is markedly improved and its point safety factors are greater than 1.35 after the lower two levels of the high slope are reinforced by 8 m long and 25 mm in diameter anchors with a space of 2.0 m according to the distribution characteristics of point safety factors.

Experimental Study on Couse of Progressive Formation of Retrogressive Landslide

SUN Lijuan, YANG Tao, CHENG Qihang, WU Dingding

2018, 53(4): 762-771. doi: 10.3969/j.issn.0258-2724.2018.04.014

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To study the progressive failure mechanism of retrogressive landslides, a test device was developed to simulate the sectional unstable sliding of landslide mass. The main body of the device was composed of several permeable boxes, and could simulate sectional sliding surfaces with different geometric shapes. The sliding zone could be softened in multiple stages by the injection of water into different permeable boxes. This caused a reduction in the shear strength of the soil in the sliding zone, which led to graded instability sliding of the landslide mass. In this manner, the progressive failure process of the retrogressive landslide could be simulated. Twelve types of test schemes were designed, and sliding surfaces and slope lines of different shapes, as well as various slope materials, were used in the simulations. The sliding zone was softened gradually from the front to the rear, forming unstable sliding sections, and then the deformation characteristics of the landslide and the shapes of the trailing-edge fractures were observed. The results show that the unstable slip section at every level corresponds to one main fracture. The properties of the sliding mass and the shapes of the slope have a significant influence on the progressive failure mechanism of the landslide. The slops in a two-section slope shape the most obvious slope deformation. The inclinations of the trailing edge are generally steep dip angles, and 77.42%of the dip angles are in the rang of 58°-88°. The inclination of the trailing edge increases as the length of the first unstable sliding zone decreases or the slope shape and sliding surface are steeper.

Combined Support of Segmental Lining and Compressible Layer of Coal Mine Shafts

QI Chun, HE Chuan, FENG Kun, XIAO Mingqing

2018, 53(4): 772-781. doi: 10.3969/j.issn.0258-2724.2018.04.015

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In order to study the influence of the compressible layer parameters on the mechanical properties of the segmental lining in the combined support system of the inclined shaft constructed by shield, a numerical model considering the contact effect between the segmental lining and the compressible layer and the stiffness reduction of the segment ring was established based on the Main Inclined Shaft Project of Shenhua Xinjie Taigemiao Coal Mine Area, and the distribution characteristics and variation laws of the internal force and deformation of the segmental lining are analyzed under different factors such as the presence or absence, the stiffness and the thickness of compressible layer. Similar model tests were carried out to further investigate the above problems. The ultimate bearing capacity and the form of destruction are also discussed. The results show that the greater the compressible layer stiffness, the greater the and the more uneven distribution of the surrounding rock pressure on the segment, at the same time, the bending moment of the segment decreases and the axial force increases. It is more obvious when the ratio of compressible layer modulus to surrounding rock modulus varies from 0.1 to 0.5. With the increase of the compressible layer thickness, the surrounding rock pressure on the segment varies according to the trend of uneven to uniform and then again to uneven. When the ratio of the compressible layer thickness to the segment thickness is 1.7, the pressure of the surrounding rock is the smallest. The axial force decreases with the increase of compressible layer thickness. The existence of compressible layer has little effect on the deformation of segmental lining. The model test results further show that the compressible layer can absorb the surrounding rock pressure and cause stress redistribution through its own compaction, so as to reduce and homogenize the load transferred to the segment, so that the internal force of the segment grows more smoothly with the external load smaller and more evenly distributed; and increased the ultimate bearing capacity of the segments by 40%. In the presence or absence of the compressible layer, the failure of the segment has experienced the processes of elliptic, elliptical exacerbation, the occurrence and expansion of the crack and instability.Moreover, the damage of the segment is more serious when the compressible layer is present. The research results of this paper can provide some reference for the design and construction of similar projects.

Analysis of Entire Load-Deformation Process of Shear Span Ratio Not More Than 2.0: Reinforcement of Concrete Squat Walls by Strut-Tie Model

CHEN Xiaolei, FU Jianping, GAN Jinfeng, XUE Feng

2018, 53(4): 782-790, 805. doi: 10.3969/j.issn.0258-2724.2018.04.016

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An improved strut-and-tie model that considers the deformation compatibility for determining the load-deformation relationship for squat walls (shear span ratio smaller than 2.0) is proposed. The model originates from the strut-and-tie model, and it includes a diagonal concrete strut, secondary concrete struts, subsidiary concrete struts, horizontal tie, vertical tie, and shear reinforcement ties. A definite equation between the deformation of two types of concrete struts (a diagonal concrete strut and four secondary concrete struts) and the displacement of the squat walls is given. The relationship among compatibility, equilibrium, and constitutive laws in each of the strut and ties was established. In addition, parameter analyses were conducted using the improved strut-and-tie model to study the effect of axial load, aspect ratio, and distribution reinforcement ratio on the skeleton curves of shear walls. The results show that, compared with the test results for six shear walls, the forces and deformations of the predicted members' are in reasonable agreement with test results. During parameter analysis, when the axial load ratio increases from 0.1 to 0.5, the maximum growth of load-carrying capacity is 27%. As the aspect ratio of shear walls increases from 1.0 to 2.0, the load-carrying capacity decreases 30%. As the distribution reinforcement ratio increases from 0.25% to 0.55%, the load-carrying capacity increases only 6%. The effect of the distribution reinforcement ratio on load-carrying capacity is not significant compared with the other two parameters.

Modelling Drivers' Lane-Changing Decision Behaviour Based on Social Force

YANG Da, SU Gang, WU Danhong, XIONG Mingqiang, PU Yun

2018, 53(4): 791-797. doi: 10.3969/j.issn.0258-2724.2018.04.017

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In order to establish a simpler lane-changing decision-making model and consider the interaction between the lane-changing vehicle and the vehicles of the target lane, on the basis of the traditional methods of lane-changing utility and selection of safety gap, an initiative lane-changing decision-making model for drivers based on the social model by combining the social force following model with the lane-changing model was proposed. First, taking the following force in the social force model as the utility function of each driveway, a lane-changing decision-making utility model for the target lane selection was established. Second, considering the vehicle's longitudinal safety in the lane-changing process, the following force was used to build utility model of interaction between the lane-changing vehicle and the vehicles of the target lane to constrain the selection of safety gap. Finally, the proposed model was calibrated and validated by using next generation simulation (NGSIM) data and genetic algorithm function in MATLAB genetic algorithms toolbox for drivers' lane-changing decision-making behaviours (keeping following, changing to right lane, changing to left lane). The study results show that the lane-changing decision-making model based on social force could identify accurately the drivers'initiative lane-changing decision-making behaviour. The recognition rates of the optimal parameters in calibration data for drivers' lane-changing decision-making behaviours (keeping following, changing to right lane, changing to left lane) reached 93.44%, 93.14%, and 90.77%, respectively, and the recognition rates of the lane-changing decision-making behaviours in calibration data reached 86.16%, 80.00%, and 80.27%. Each recognition rate in calibration data and validation data was above 80.00%, and the overall recognition rates reached 92.66% and 83.28%, respectively.

Evaluation of High-Speed Railway Maintenance Plan Factors Based on Triangular Fuzzy Number

ZHANG Qiangfeng, LÜ Hongxia, YANG Yuxiang

2018, 53(4): 798-805. doi: 10.3969/j.issn.0258-2724.2018.04.018

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In order to improve the maintenance abilities of high speed railway and reduce train delays, an evaluation system is proposed based on actual maintenance plan data. Evaluation of the railway maintenance plan is supposed to identify any weak links and contribute to the safety of the operational environment. In this system, four key maintenance plan factors are identified:power supply, control system equipment, station infrastructure, and signal and communication equipment. The triangular fuzzy number and a fuzzy evaluation method are introduced to build an importance scale matrix for estimating the importance of these four factors in maintenance plans. Delays caused by equipment and infrastructure failures are extracted and combined based on real delayed train data. These factors are also proved to be independent. Factors causing delays and the number of delayed trains are used to quantitatively measure the effects of maintenance plan factors. Finally, maintenance plan data and delayed train data from the China Railway Company are used to verify the feasibility of the method. Results show that implementing a daily HSR maintenance plan has a positive effect on decreasing train delays. The amount of attention focused on the maintenance factors is inversely proportional to the delay situation. Maintenance of control equipment and power supply equipment is weak, which is the primary cause of train delays.

Complex Point Cloud Registration and Optimized Data Processing for High-Speed Railway Turnout

WANG Peijun, LÜ Dongxu, CHEN Peng

2018, 53(4): 806-812, 849. doi: 10.3969/j.issn.0258-2724.2018.04.019

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To enhance the inspection efficiency of high-speed switch rail wear, a complex registration based on a distance encoder is proposed, considering the inspection standards and the geometric characteristics of high-speed switch rail. The distance information was combined with the point cloud registration to improve automatic inspection. Additionally, the OpenCL (open computing language) heterogeneous acceleration model was introduced to achieve parallel data processing with higher speed during computation of the point feature histograms (PFH). In the on-site inspection of high-speed switch rail wear, the system function was verified on the structured light inspection platform, and the total inspection performance was increased by up to 70% by the optimized point cloud registration and data processing methods.

Study on Process Design of EMU Depot Combining Overhaul and Depot Repair

TANG Youfu

2018, 53(4): 813-819. doi: 10.3969/j.issn.0258-2724.2018.04.020

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Conventional locomotives and vehicles need to be transported to locomotive and vehicle manufacturing factories for large repair or overhaul from railway bureaus after they have attained a certain traveling mileage or run a certain number of years. Transporting locomotives and vehicles between railway bureaus and manufacturing factories for repair wastes the carrying capacity of railway lines, interferes with railway operation, and extends maintenance time. Besides, the maintenance time of EMUs needs to be minimised because of the high cost of EMUs. In summary, an EMU maintenance base (EMU depot) that combines overhaul and depot repair needs to be investigated. The process design of an EMU depot needs to be compatible with the maintenance of different types of EMUs, and the efficiency of the EMU depot needs to be improved. In order to solve the abovementioned problems, the general layout scheme and choice of land block of the EMU depot are studied. In addition, a scheme of underfloor vehicle-lifting machines for CRH2 and CRH3 EMU level 3 maintenance (depot repair) is studied. Finally, the efficient completion of a successive maintenance scheme for level 4 and 5 maintenance of a vehicle is presented. According to the design scheme presented herein, the combination of the overhaul and depot repair is first realised. In addition, the length of the vehicle-lifting elements of the machine can be adjusted within a range of 17. 375-17. 500 m, which achieves compatibility with the level 3 maintenance of CRH2 and CRH3 EMU. Further, the designed maintenance line is applicable to not only two eight-car EMUs but also a 16-car EMU. Moreover, level 4 and 5 maintenance of a vehicle can be completed within 80 min. With the proposed scheme, the specialisation of every maintenance station and process can be realised. The cross operation among different maintenance groups is avoided. A clean assembly station of car body parts is guaranteed, and maintenance efficiency and quality are improved.

Stability of Impulsive Disturbance Complex-Valued Cohen-Grossberg Neural Networks in a Complex Number Domain

XU Xiaohui, XU Quan, SHI Jizhong, ZHANG Jiye, CHEN Zilong

2018, 53(4): 820-828. doi: 10.3969/j.issn.0258-2724.2018.04.021

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Abstract:
To analyse the effect of impulsive disturbances on neural networks, the dynamical behaviour of these disturbances was examined at the module of the equilibrium point of a class of complex-valued Cohen-Grossberg neural networks with time-varying delays. It was assumed that amplification, self-feedback, and activation functions were defined in a complex number domain. First, the existence and uniqueness of the equilibrium point of the system were analysed by utilising the corresponding property of the M matrix and the theorem of homeomorphism mapping. Second, the globally exponential stability of the module of the equilibrium point of the system was studied by applying the vector Lyapunov function and mathematical induction methods. The corresponding stability criteria were then established. Finally, two numerical examples from simulations were given to illustrate the practicability and correctness of the obtained results. The simulation results revealed that the states of the addressed system can reach equilibrium within 0.5 s. Other results showed that the greater the delay and impulsive strength and the smaller the amplification, the slower was the state convergence rate.

Investigation of Lubricant Transfer under Slider Lubricant Contact Condition

PAN Deng, TANG Zhengqiang, HAO Xiuhong

2018, 53(4): 829-834. doi: 10.3969/j.issn.0258-2724.2018.04.022

[Abstract](353)

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Abstract:
To enhance slider flying stability and extend the life span of hard-disk drives, a molecular dynamics model for investigating lubricant transfer in the presence of slider lubricant contact was built. The effects of the following parameters on lubricant transfer and lubricant distribution on the disk surface during the operation of the hard-disk drive were analysed:relative velocity between the slider and disk and the range of the air-bearing pressure difference between the high-and low-pressure areas before contact. In addition, lubricant fragments with different lengths were obtained by adjusting the number of beads within a full lubricant molecule. The effect of lubricant fragments on lubricant transfer was also investigated. The simulation results indicate that the amount of lubricant transfer increases with increasing slider-to-disk relative velocity and air-bearing pressure difference; the growth rates of the amount of lubricant transfer are 38.8% and 6.7% for unit air-bearing pressure and unit velocity, respectively. Lubricant fragments have little effect on lubricant transfer; the height of lubricant accumulation decreases with increasing relative velocity. The lubricant accumulation height on the disk surface is not affected by the air-bearing pressure difference.

Fast Time-Varying Sparse Channel Estimation Based on Kalman Filter

YUAN Weina, WANG Jiaxuan

2018, 53(4): 835-841. doi: 10.3969/j.issn.0258-2724.2018.04.023

[Abstract](474)

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Abstract:
A fast time-varying sparse channel estimation method based on the Kalman filter is proposed for channel estimation of an orthogonal frequency division multiplexing communication system operating in high-speed railways and mountain areas. Based on the basic expansion model (BEM), compressed sensing (CS) was employed for the estimation of sparse delays, and a Kalman filter (KF) estimator was utilised for estimating the BEM coefficients. The channel gains were then computed easily. The simulation results show that under the same signal-to-ratio (SNR) condition, with the increase in frequency-normalised Doppler shift (FND), the MSE of the new method is superior to that of traditional methods, such as SNR is 20 dB and FND is 0.1, and a 4 dB performance improvement is achieved. Under the same Doppler shift condition, the same result is obtained as that with the increase in SNR, such as FND is 0.2 and MSE is 0.06, and a 6 dB SNR gain is achieved. These results show that the new method is more robust to variation in channel time and stronger against noise compared with traditional methods.

SVDD-Based Research on Railway-Turnout Fault Detection and Health Assessment

ZHONG Zhiwang, CHEN Jianyi, TANG Tao, XU Tianhua, WANG Feng

2018, 53(4): 842-849. doi: 10.3969/j.issn.0258-2724.2018.04.024

[Abstract](502)

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Abstract:
In order to improve the quality of railway-turnout maintenance procedures and reduce equipment failure, a method for turnout-fault-detection and health-index evaluation based on the support vector domain description (SVDD) technique, is proposed. Through analysis of the switch-equipment mechanism, the turnout power curve was divided into 3 parts, each representing the unlocking, conversion, and locking processes respectively. To this end, characteristic parameters of the switch power curve were extracted. Subsequently, in the feature space, an SVDD-based turnout-fault-detection algorithm and health assessment were proposed. Lastly, the efficiency of the proposed algorithm was verified by comparing simulation results against experimental data. Experimental results demonstrate that the proposed health index possesses an accuracy of 95%, which could prove to be significant in on-site maintenance and guidance applications.

Influence of Initial Deflection Imperfections on Critical Flutter Aerodynamic Pressures of Shallow Cylindrical Shells

FAN Chenguang, YANG Yiren

2018, 53(4): 850-856, 864. doi: 10.3969/j.issn.0258-2724.2018.04.025

[Abstract](367)

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Abstract:
To study the effect of initial deflection imperfection on the flutter critical dynamic pressure of a cylindrical shallow shell aeroelastic system, an initial deflection was introduced into the aeroelastic equation of cylindrical shallow shells. The differential quadrature method was used to discretize the system, and the flutter critical dynamic pressure of a linear system in supersonic axial flow was analysed using the eigenvalue method. The results showed that the initial deflection imperfection can significantly affect the flutter critical dynamic pressure. Herein, when the circumferential half wave number of the initial deflection equals 1, the critical dynamic pressure parameter of flutter is proportional to the initial deflection imperfection factor. When the circumferential half wave number is less than 4, with the increase in the initial deflection imperfection factor, the critical dynamic pressure of the system tends to decrease. For the small curvature condition, when the circumferential half wave number is greater than 4, the flutter critical dynamic pressure change caused by the increase in the initial deflection imperfection factor is not significant. For the large curvature condition, when the circumferential half wave number is greater than 4, the flutter critical dynamic pressure decreases significantly with the increase in the initial deflection imperfection factor. It was also found that the geometric form of the initial deflection affected the circumferential half wave number of the flutter coupling modes.

I/O Scheduling Algorithm for Data Servers in Cloud Storage Environments

LI Yu

2018, 53(4): 857-864. doi: 10.3969/j.issn.0258-2724.2018.04.026

[Abstract](433)

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Abstract:
Distributed file systems (DFSs) are generally employed for storing user data while designing a cloud storage system. The primary aspects of DFSs include efficient storage and management of metadata, data distribution strategies, and reliability of user data. In the case of data servers of a DFS, the FIFO (first in first out) strategy is adopted for scheduling I/O requests which are received by a data server daemon. The FIFO algorithm prioritises all such requests equally; requests that require better quality of services may therefore be blocked for long durations. To address this issue, a new priority based periodic scheduling algorithm (PPSA) has been proposed. Initially, PPSA classifies requests into different priority queues. Then, it periodically schedules requests according to their respective priorities and dedicated time slices. The obtained DFS simulation results show that PPSA can increase the response performance of heavy-load real-time requests by 20%, and can also ascertain the lowest response time performance for other requests.

Man-Machine Functional Dimension Design of Riding Equipment in Subway Passenger Compartments

WEI Feng, XU Bochu, ZHI Jinyi, DONG Shiyu

2018, 53(4): 865-872. doi: 10.3969/j.issn.0258-2724.2018.04.027

[Abstract](492)

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Abstract:
A human-centred experiment and ergonomic correlation-analysis approach was adopted to investigate the impact of passenger body size on the functional dimension design of riding equipment in subway passenger compartments. Subsequently, the relationship between the functional dimension configuration among passengers, subway seats, and handrails was tested and analysed based on human physiological structure, psychological endurance, and functional properties of riding equipment. This was achieved by combining a pressure distribution experiment with virtual simulation technology and subsequent subjective evaluation and analysis. Results demonstrate that when the curvature radius of the backrest outer convex arc measures 186 mm while that of the cushion inner concave arc measures 785 mm, seat surface closely matches the physiological curvature of the body-sitting posture, thereby meeting the requirements of riding comfort. Also, when the height of handrail rings and that of cross rods are set as 1 710 mm and 1 860 mm, respectively, handrail height meets usage requirements of passengers having different bodies sizes as well as that of balance between applicability, safety, and accessibility.

Performance Degradation Diagnosis of Das Turbine Based on Improved FUKF

ZENG Li, LONG Wei, LI Yanyan

2018, 53(4): 873-878. doi: 10.3969/j.issn.0258-2724.2018.04.028

[Abstract](493)

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Abstract:
Owing to the difficulty in assessing the performance of a gas turbine during usage, because of sudden changes in its operation state, the use of an fading unscented Kalman filter with residual similarity (FUKF-RS) algorithm for the health parameter estimation of a gas turbine is proposed in this study. At first, under the common fading unscented Kalman filter (FUKF) framework, the health parameter estimation algorithm of the gas turbine was built. The weights before and after estimation were adjusted by multiplying the fading factor with the variance of measured value during the updating process of estimation; the fading factor was estimated by keeping the residual vectors to be orthogonal. Then, the similarity of the residual matrix was represented by the cosine value of the residual vector before and after the estimation, and the proportion of residual matrixes was determined according to the magnitude of the similarity. Finally, the fading factor of the algorithm was substituted by such proportion to calculate the residual matrix and obtain the quantitative parameter required for the calculation. The results show that the FUKF-RS algorithm can trace the sudden change of state of the gas turbine, and its accuracy in parameter estimation is higher by approximately 3% as compared to that of the FUKF algorithm. Additionally, as the component performance changes slowly, the parameter estimation curve will be smoother than that of the common FUKF, and the estimation accuracy will be increased by approximately 2%.

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2018 Vol. 31, No. 4