西南交通大学学报

Analysis of the Bearing Capacity of PBL Shear Connector

SONG Suidi, HUANG Bo, ZHU Bing, CHEN Kejian

2017, 30(4): 647-654. doi: 10.3969/j.issn.0258-2724.2017.04.001

[Abstract](619)

Abstract:
The PBL shear connector used to connect the corrugated steel ribs and concrete roof of long-span continuous rigid frame bridges has its unique structure, mechanics, and stress environment characteristics. In order to study the load-slip properties and bearing capacities of this kind of PBL shear connectors, failure tests were carried out with static loads using 33 specimens in 13 types of 3-hole models (3 specimens for each model type), in which transverse tensile and compressive prestresses were applied to the specimens with jack and finishing rolling rebar. Through the tests, the concept and value of a design bearing capacity were proposed and fitting formulas of the design bearing capacity and the ultimate bearing capacity were obtained. The results show that when the load is smaller than the design bearing capacity, the PBL connector works in the elastic stage with a slip less than the specified limit. The load-slip curves obtained from tests can be segmented into elastic stage, elastoplastic stage, yielding stage, and partially reinforcing stage. Under a concentrated loading condition, the bearing capacity calculated by average of the load born by the 3 holes is obviously smaller than the actual value. In addition, the transverse tensile prestress reduces the design bearing capacity and ultimate bearing capacity of the PBL shear connectors by about 0.020 and 0.043 kN, respectively, while the transverse compressive prestress benefits the bearing capacity of the shear connectors. The effect of prestress on bearing capacity can be considered separately.

Influence of Crossed Hangers on Aerostatic Stability of Suspension Bridge during Constructing

LI Cuijuan, LI Yongle, YE Huawen, QIANG Shizhong

2017, 30(4): 655-662. doi: 10.3969/j.issn.0258-2724.2017.04.002

[Abstract](558)

Abstract:
In order to evaluate the aerostatic safety of super-large span suspension bridges, the 3D nonlinear finite element method was used to analyze the aerostatic stability of a super-large span suspension bridge with 3 500 m long main span and carbon fibre reinforced plastic (CFRP) cables, and the influence of three kinds of crossed hangers on the aerostatic performance and deformation shape of the suspension bridge during its construction were studied. The results show that as the stiffening girder is constructed step by step, the aerostatic stability becomes worse and worse, and finally reaches its minimum value when all of girder segments are erected but not rigidly connected. Only the horizontal crossed hanger has little effect on the aerostatic stability of suspension bridge during construction phase, but both the vertical crossed hanger and the composite crossed hanger made up of vertical and horizontal crossed hangers can improve the aerostatic stability significantly during construction. While the percentage of erected stiffening girders during construction is between 9.8% and 60.6%, the composite crossed hanger is more effective than other types of hangers in enhancing the aerostatic stability; however, using vertical crossed hangers alone is effective enough in other construction stages.

Non-Stationary Synthesis of Multi-Dimensional and Multi-Point Seismic Waves

JIA Hongyu, CHEN Hang, ZHANG Keyue, KANG Rui, ZHENG Shixiong

2017, 30(4): 663-670. doi: 10.3969/j.issn.0258-2724.2017.04.003

[Abstract](528)

Abstract:
To better understand the realistic spatial behaviour and the multi-dimensionality and non-stationary nature of seismic ground motions, the trigonometric-series method was used to generate and synthesize the multi-dimensional and non-stationary seismic waves in the present work. Firstly, the design response spectrum was converted to an equivalent power spectrum. The power-spectrum density matrix was then extended from one dimension to three dimensions to account for the multi-dimensionality of the seismic ground motions. Subsequently, the envelope function and the trapezoidal window connection were employed to consider the non-stationary nature of the seismic ground motions and a Fourier transform was used to generate the time history of the spatial seismic waves. The response spectrum of a newly generated wave was compared with the target response spectrum at every excitation direction to revise the amplitude of the generated wave in the frequency domain. Finally, the fitted and the designed spectrum were compared to verify the accuracy of the synthetic seismic waves. Some important conclusions have been drawn from the comparison that the error in the fitted spectrum partially exceeds 10.00% (maximum 16.68% ); however, the overall error of fitting is not beyond 8.00% (18.00% without modification).

Numerical Study on Wave-induced Oscillatory Soil Liquefaction around a Partially Buried Pipeline

DUAN Lunliang, ZHENG Dongsheng, ZHANG Qibo, ZHU Bing, YANG Bing

2017, 30(4): 671-677. doi: 10.3969/j.issn.0258-2724.2017.04.004

[Abstract](524)

Abstract:
To examine the oscillatory soil response around a partially buried pipeline under wave load, a numerical model for wave-seabed-pipeline interactions was proposed using the finite element method, in which the momentum source function was added to the Reynolds-averaged Navier-Stokes (RANS) equation to generate waves, and the Level Set Method was used to track the water free surface. The wave pressure calculated from the wave model was applied to be the seabed model boundary condition to determine the wave-induced soil response. Based on the proposed model, a set of analyses regarding the effects of backfill thickness and wave characteristics on the oscillatory soil response was carried out. Numerical results indicate that wave characteristics can significantly affect the wave-induced oscillatory soil response, and that the liquefaction depth increases with the increment of wave height and period. The liquefaction depth at the bottom of the pipeline can reach 0.92 m when the wave height is 3 m and the wave period is 10 s. Moreover, the soil at the bottom of the pipeline can be prevented from being liquefied when the backfill thickness is greater than the critical backfill thickness under a certain soil condition. In other words, the soil at the bottom of the pipeline can be protected by increasing the backfill thickness.

Analysis of Ultimate Load-Carrying Capacity of Crescent-Shaped Concrete-Filled Steel Tube Arch Bridge

MA Ming, QIAN Yongjiu, XU Baishun

2017, 30(4): 678-684,714. doi: 10.3969/j.issn.0258-2724.2017.04.005

[Abstract](543)

Abstract:
In order to investigate the influences of structure parameters on the ultimate load-carrying capacity of crescent-shaped concrete-filled steel tube arch bridge, based on the constitutive relation of core concrete under confinement, the extreme-point stability of the arch bridge was analyzed. First, the most unfavorable load combination for ultimate load-carrying capacity was obtained by eigenvalue analysis, and then by considering the effects of the geometry nonlinearity and material nonlinearity in this loading condition, the ultimate load-carrying capacity and safety factor of stability were solved by Riks iterative solution. At last, the Shimian Dadu River Bridge was used as an example to analyze the effects of structure parameters on ultimate load-carrying capacity such as the angle between main and side arch rib, the strengths of steel and core concrete, and steel ratio. The analysis shows that the buckling mode of the crescent-shaped arch bridge is transverse deformation of the whole rib, and the structure stability mainly depends on the sustained load. The bearing capacity decreased 3% when considering geometry nonlinearity, decreased 1% when the initial imperfection increased from 1% to 10%, and decreased 55% when considering both geometry and material nonlinearities. When the steel ratio is increased by 50%, the safety factor of stability increased 19.0%; with the concrete strength increasing from C50 to C60, it increased 12.0%; with the steel strength increasing from Q345 to Q420, it increased 9.6%; with the angle between ribs increasing from 10to 25, it decreased 5.9%.

Mechanical Characteristics of Asphalt Pavement on Bridge Deck under the Braking Force of BRT Buses

AI Changfa, ZHANG Yilin, AL-KAHTANI M S M, YANG Enhui

2017, 30(4): 685-693. doi: 10.3969/j.issn.0258-2724.2017.04.006

[Abstract](604)

Abstract:
To reveal the mechanical response characteristics of deck pavement under dynamic loads, taking for example the asphalt pavement of one viaduct in Chengdu, several asphalt pavement structures under the braking force of BRT buses were compared and analyzed by using the numerical simulation analysis methods and numerical analysis of orthogonal test. The selected pavement structure was taken as the further object, and the effects of moving vehicle speeds on the mechanical response of deck pavement on the braking deceleration section near the BRT bus stop were analyzed and its mechanism was also explained. The analysis shows that the vibration impact and loading period lead to the occurrence of critical speeds in surface vertical deflection and shear stress responses of the pavement. At different initial bus velocities, there is a short but fast-changing interaction of both positive and negative bending and shear stresses at each tire footprint area on pavement. in the surface layer. Under the braking loads, surface shear stresses were rather great, which arrived at a peak at an initial vehicle speed of 60 km/h. Near the bus stations where bus deceleration or acceleration occur frequently, anti-shearing and anti-fatigue performance of pavement structure should be improved and interlaminar bonding should be strengthened.

Research on Macropores Flow in Unsaturated Zone Soil of Slopes under Different Vegetation Community

ZENG Qiang, XU Zemin, ZHANG Youwei, ZHANG Huining, MEI Xuefeng, REN Zhe

2017, 30(4): 694-704. doi: 10.3969/j.issn.0258-2724.2017.04.007

[Abstract](569)

Abstract:
To evaluate Macropores Flow in unsaturated zone Soil of natural Slopes under rainfall conditions, A dyeing tracing test with methylene blue was carried out based on retaining the original state of the slopes and simulating rainfall process. Combined with water breakthrough method and high-precision dyeing profile image, based on image processing, differential and regression analysis, distribution and influence factors of macropore flow in high coverage(90%) slope during the rainfall process were studied. The results show that: comparing with herbaceous vegetation community soil, the distribution range(dyeing coverage is at 46.18%-63.55%) of macropores flow in the profile of woody vegetation community soil is larger, the continuous degree is lower, the differentiation degree(dyeing route number is at 203-8 599) is higher, the staining patterns are more complex. Macropores flow patterns of 2D can reflect that of 3D. In the rainfall distribution process, competing with the interception effect of macropore in soils, slope orientation effect is tend to infiltrate vertically along the slopes(max dyeing coverage are at 63.55% and 59.67%). Roots size is not the only factor to control macropores scale(the mean pore sizes are at 1.23-2.03 mm and 1.34-2.23 mm). Aggregate particles themselves can also have root channels.

Model Test and Numerical Simulation of Penetration Process of Sleeve for Cast-in-Place Piles Driven by Vibratory Hammers

XIAO Yongjie, CHEN Fuquan, DONG Yizhi

2017, 30(4): 705-714. doi: 10.3969/j.issn.0258-2724.2017.04.008

[Abstract](452)

Abstract:
A model test was carried out to investigate the excess pore pressure, the radial extruding stresses, and the degree of soil plug of a vibratory driven sleeve for cast-in-place piles. A finite element model was also introduced by using the commercial code, ABAQUS. The results from the finite element analysis are in a strong agreement with the experimental observations. The results show that the excess pore pressure and radial extruding stresses increase to 1 kPa and 8 kPa, respectively; nevertheless, the extruding effect is mainly limited within a radial distance of about 6 times the sleeve diameter. The soil shear strength and granular cementation force decrease during vibratory sleeve driving, which is induced by cyclic shearing action in the shear interface. As a result, the inside sleeve of the soil plug is in an incompletely plugged mode. During vibratory sleeve driving, the soil plug in the sleeve end forms an annular soil arch, which gives rise to an obvious increase in internal friction resistance. The soil plug of this section withstands 80%of the internal friction resistance. When the penetration depth is the same, the height of the soil plug in a saturated sand foundation is 1.2 times the height of the soil plug in a dry sand foundation. The vibration frequency, sleeve diameter, and saturation have significant effects on the soil plugging effect.

Test Study on Seismic Performance of PEC Column Fabricated with Thin-Walled Steel Plates-Steel Beam (Reduced Beam Section) Composite Frame

FANG Youzhen, DAI Yaping, WANG Chenyu, ZHAO Hongkang, YANG Bin

2017, 30(4): 715-724. doi: 10.3969/j.issn.0258-2724.2017.04.009

[Abstract](600)

Abstract:
In order to investigate the seismic performance of a partially encased concrete(PEC)column fabricated with thin-walled steel plates-steel beam (reduced beam section)composite frame, a 1/2 scale test specimen of inter-story substructure was designed and a lateral-cycle repeated loading test was conducted. Based on the test observation and measurements, the failure mode and the hysteretic characteristic loops were derived, and the seismic performances including lateral stiffness, energy dissipation capacity and drift pattern were analyzed. Tests result show that reduced beam section can achieve the target of plastic hinge forming location away from joint to meet the seismic principle of strong joint. The displacement ductility coefficients of the inter-story and whole specimen are larger than 4.05 and 4.81, respectively, the maximum equivalent viscous damping ratios are 0.288 and 0.286. The lateral stiffness is evenly distributed along the height of the specimen, the drift pattern of the specimen shows the ideal inverted triangle pattern of the flexure-shear type. The plastic failure mechanism is induced by forming plastic hinge at all reduced sections, when the load-carrying capacity of the specimen is decreased to 85% of its ultimate strength,the drift angles of the inter-story and whole specimen are 0.043 3 rad and 0.039 4 rad which all surpass the limit(0.035 0 rad) inter-story drift at the maximum considered earthquake level, indicating that the specimen has superior seismic performance.

Transportation Model and Simulation of Chloride in Concrete under Electric Field

LIU Zongmin, ZHAO Kunpu, MAO Jize

2017, 30(4): 725-730. doi: 10.3969/j.issn.0258-2724.2017.04.010

[Abstract](483)

Abstract:
For the study of the durability of concrete structures in the coupling environment of chlorine salt and stray current, transportation law of chloride in concrete under electric field was investigated. According to the Hamilton-type variational principle, a transportation model of chloride in concrete under electric field was established. Based on the view of mesoscopic, quantitative formula of water saturation of pore in concrete was established. Considering the effects of time factor and water saturation of pore on transportation, the diffusion coefficient of chloride under unsaturated state was corrected. The transportation process of chloride in concrete was simulated by comsol, And the transportation rate of chloride under electric field was compared with free diffusion rate under concentration gradient. It is a suitable way to study the durability and service life prediction of underground concrete structures by the chloride transportation model of concrete under electric field. In the influence of 10 V electric field, the transportation efficiency of chloride in concrete is equivalent to 769 times of the efficiency of chloride transportation under free diffusion.

Analysis of Static and Dynamic Flexural Failure Mode of Double-Layer Concrete Composite Beam

SU Chengguang, LIU Dan, CAO Shihao, ZHAO Pingrui, LIU Xueyi

2017, 30(4): 731-737. doi: 10.3969/j.issn.0258-2724.2017.04.011

[Abstract](494)

Abstract:
To deal with the interface damage of non-ballasted tracks, the coordinated working performance of double-layer concrete was studied. From the mesoscopic perspective, actual aggregate distribution was obtained using the image processing technology, and the 2D model of double-layer concrete was established to simulate and validate the four-point flexural test. The influences of the loading strain rate on the flexural failure mode, the flexural-tensile strength and the macroscopic relationship of stress and displacement were explored. Results show that the simulated stress-displacement curve and failure mode are similar with the tested ones, which means that using the mesoscopic model to simulate the progress of crack propagation is feasible. Under the high loading strain rates of 110-2 /s and 110-1 /s, large damage occurs at the interface of double-layer concrete. When the loading strain rates are 110-3/s, 110-2/s,and 110-1 /s, respectively, the maximum bearing stress are 1.50, 6.41,and 14.40 MPa, respectively. The single crack propagates along the weak interface and transfers to the complicated multi cracks. Moreover, the crack width increases greatly and the concrete damage expands to the whole tension area.

Three-Dimensional Analysis Model of Surrounding Rock Deformation and Support Stiffness for Tunnel Construction

YU Fucai, ZHANG Dingli, FANG Qian, SUN Zhenyu, TAI Qimin, ZHAO Jiangtao

2017, 30(4): 738-745,763. doi: 10.3969/j.issn.0258-2724.2017.04.012

[Abstract](517)

Abstract:
In the field of analyzing 3D tunnel construction mechanics, the current mechanical models have many difficulties, including low computing accuracy, high computing resource requirements, and low computing efficiency, which can't meet the practical requirements; thus, a new analysis model of a deep-buried circular tunnel was proposed with considering the equivalent force acting on the wall and the face to simulate the excavation effect. To evaluate two cases of a tunnel face near the entrance and far from it, the integral formulae of the deformation field of the surrounding rock were derived based on the Mindlin and Kelvin solutions, respectively. The paper treated the excavation medium as support mass and developed the formulae of surrounding rock deformation through introducing the support force into the analysis model. According to the above formulae, the deformation field of surrounding rock and the quantitative values of its demand for the support structures might be calculated. The results show that: under the two cases, the deformation distribution of the surrounding rock is basically consistent; while the face is near to the entrance, the maximum calculation and numerical results of the axial displacement of the lengthwise section are 6.1 mm and 5.5 mm, and the radial displacements at the face are 2.4 mm and 2.6 mm, and the errors are 9.8% and 8.3%, respectively. When the face is far from the entrance, the maximum calculation and numerical results of the axial displacement of the lengthwise section are 6.0 mm and 5.7 mm, respectively and the error is 5.0%; for an arbitrary set of calculation parameters of surrounding rock and supporting structures, the results of advanced displacement at the face are 3.6 mm and 3.0 mm and the results of final displacement are 9.1 mm and 8.5 mm, and the errors are 16.7% and 6.6%, respectively, showing that the calculation results of longitudinal deformation are not consistent with the numerical results; and for the penstock 2# deformation of Dagangshan Hydropower Station, its calculation and mortoring results of advanced displacement are 0.4 mm and 0.4 mm and their results of final displacement are 1.0 mm and 1.1 mm, and their errors are 0 and 10%, respectively. Therefore, the stiffness requirement of the surrounding rock could be determined quantitatively by combining the deformation control standard and the proposed model; the finding can guide the design parameters of the supporting structures.

Tunnel Entrance Field Characteristics Induced by High Speed Train with Crosswind at Entrance

LUO Jianjun

2017, 30(4): 746-754. doi: 10.3969/j.issn.0258-2724.2017.04.013

[Abstract](580)

Abstract:
In order to ensure the safety of high speed trains under the existing geographical landscape, a numerical simulation was performed to study the aerodynamic effects of crosswinds at the tunnel entrances. The results of the model show that a crosswind at the tunnel entrance creates a negative pressure peak at the measuring point in the tunnel, and that the pressure increases to a positive peak when there is no crosswind. As the crosswind decreases, the simulated compression wave propagates forward and gradually form two peaks. As the wind speeds progressively decrease, the first compression wave peak gradually disappears and the second peak strengthens to the values above the positive pressure peak when no crosswind is present. Further evaluation of the simulated results showed the piston wind is smaller on the upwind side of the annular space than the leeward side when a crosswind is present at the tunnel entrance. It creates a significant eddy current on the leeward side of the entrance to the tunnel. When the crosswind velocity reaches 40 m/s, the piston wind can reach the velocities of 21.8 m/s. When the crosswind velocity is high, the compression wave at the measured point displays a smaller maximum value and the maximum negative pressure value increases. The maximum negative pressure value and crosswind velocity are proportional to the overall pressure, but the increases in amplitude of the maximum negative peak are greater than the maximum positive pressure increase. When the crosswind velocity reaches 40 m/s, the compression wave in the tunnel can reach a maximum negative pressure value of -6 547 Pa.

Active Current Control Method Based on Grid-Connected Proton Exchange Membrane Fuel Cell

LI Qi, YU Shuang, HAN Ying, CHEN Weirong

2017, 30(4): 755-763. doi: 10.3969/j.issn.0258-2724.2017.04.014

[Abstract](513)

Abstract:
The conventional PQ control method fails to effectively respond to load demands because it does not adequately consider the actual operating characteristics of the proton exchange membrane fuel cell (PEMFC) system when the power load changes. In order to ensure that the PEMFC operation system responds accurately and quickly, a model of a PEMFC grid system consisting of a 150 kW PEMFC stack, DC/DC converter, inverter, and filter is developed according to the operation characteristics and PQ control principle of the PEMFC. Then, a PQ control-based active current control method is proposed based on this model. The results of a MATLAB simulation indicate that the proposed active current control method can fulfill the demands of grid connection under both rated and non-rated output power conditions, enabling the grid-connected system to effectively respond to load changes. This actualizes large closed-loop control from the power supply to the interconnection and ensures stability and reliability in the grid system operation with bus current harmonics of 1.76% and 2.89%, whereas the traditional PQ control method can only operate stably when the PEMFC outputs at the rated power (150 kW).

Research on Optimised Synchronous Space Vector Pulse Width Modulation Algorithm to Minimise Harmonic Current

ZHANG Zhaoyang, ZHANG Xiaohua, GE Xinglai, FENG Xiaoyun, XU Junfeng

2017, 30(4): 764-773,788. doi: 10.3969/j.issn.0258-2724.2017.04.015

[Abstract](575)

Abstract:
One of the major concerns with regard to high-power traction inverters is the current harmonics that arise when working under the condition of low pulse ratios. To solve this problem, an optimized synchronous space vector pulse width modulation (SVPWM) was proposed to minimize root-mean-square (RMS) value of harmonic currents. On the basis of symmetry constraints of the output voltage waveforms in the traditional synchronous SVPWM, a generalized method was proposed to construct switching vector sequences. Using the constructed switching sequences set, the switching angle of a single vector sequence was optimized, and an overall optimization solution and system-level optimization selection were executed. Compared with the phase-voltage-oriented optimization pulse width modulation (PWM), the proposed optimized synchronous SVPWM algorithm can reduce 2/3 range of the solution set, and achieve convergence to the global optimal solution at any given initial value of the iteration, regardless of the initial value.

Magnetically Integrated Structure for Transformer-Type Controllable Reactors: Magnetic Circuit and Circuit Analysis

TIAN Mingxing, FU Pengyu, LI Ninghao

2017, 30(4): 774-781. doi: 10.3969/j.issn.0258-2724.2017.04.016

[Abstract](612)

Abstract:
In order to meet the high impedance and weak coupling design requirements of controllable reactors of transformer type (CRT), a practical CRT body structure is proposed, based on magnetic integration technology. First, the paper presents the new structure. By using a leakage magnet core between the work and control windings, the proposed structure integrates the transformer and the current-limiting inductance together, thus forming a basic, independent, high-impedance unit. Several of these basic independent units are then combined in parallel to form the CRT body, which meets the weak coupling design requirement. Second, the distributions of both the main and leakage magnetic fluxes are analyzed in detail under different working conditions, by establishing the equivalent magnetic circuit and equivalent circuit models. The current calculation formula is deduced, and the relationship between the current and flux distribution is revealed.Based on this analysis, a single phase CRT whose control windings' rated currents are 10A, 15A, and 20A respectively is simulated and calculated. The obtained simulation results show that, when the control windings are short-circuited in sequence, the work winding currents are 9.997 A, 24.540 A, and 43.900 A, which are fundamentally the rated current values. the short-circuit currents of the operating control windings do not affect the other control windings operating. The proposed CRT structure can meet the high impedance and weak coupling design requirements.

Measuring Impulse Grounding Resistance by Multi-Frequency Combination Method

MA Yutang, GAO Zhuqing, CAO Xiaobin, ZHOU Fangrong, DU Junle, TIAN Mingming

2017, 30(4): 782-788. doi: 10.3969/j.issn.0258-2724.2017.04.017

[Abstract](481)

Abstract:
To measure the impulse grounding resistance of transmission line towers accurately, a multi-frequency combination measurement method based on Fourier transformation is proposed. Firstly, a standard lightning impulse waveform was extended as a periodic function. This function was then expanded as a trigonometric series via Fourier transformation. Frequencies of the fundamental wave and harmonics were thus obtained, and amplitude and phase of relationships between the measured source and corresponding Fourier series terms were described. Through scaling and phase shifting, the measuring results were converted to a response function of Fourier Series terms using different frequency components. The impulse response waveform was obtained via the inverse Fourier transformation, yielding the impulse grounding resistance. The effect of the number of Fourier Series terms on the impulse grounding resistance was analysed. It is found that if the number increases from 50 to 120, the deviation between measurement and simulationresult drops from 21% to 9%. Finally, physical experiments have verified that this adopted method is consistent with the direct impact power measurement results. Experimental results show that under the same measuring connection mode, the difference between the measuring result presented here and that of the percussion device is less than 10%.

Optimization of Public Traffic Network Based on Comfort Improvement

WANG Dianhai, XIONG Manchu, ZHANG Lihui, XU Fei

2017, 30(4): 789-795. doi: 10.3969/j.issn.0258-2724.2017.04.018

[Abstract](566)

Abstract:
In order to mitigate the crowding in buses and make passengers more comfortable, an optimization method is proposed based on the OD information of bus stations. An optimization model was developed with the goal of maximizing the average passenger comfort. The maximum route length and number of transfers were also taken into account. The comfort was calculated using a membership function, and the relationship between the comfort and number of passengers was plotted to illustrate the rationality of the optimization method. Routes with poor comfort were optimized one by one from low to high comforting levels by exchanging routes and sharing passengers between adjacent lines. The goal was to balance the passenger flows to equalize the utilization of different buses by adjusting routes. An example was used to confirm the feasibility and effectiveness of this optimization method. The comfort standard deviation between stations on a crowded line decreased from 0.24 to 0.09 after the optimization. The passenger flow imbalance between stations was obviously improved. The average passenger comfort increased from 0.84 to 0.91 (8.3%).

Structural Brittleness Analysis of Information Transfer Process of High-speed Railway Train Control

PENG Qiyuan, FENG Liping, WEN Chao, ZHANG Xinzhu

2017, 30(4): 796-801,809. doi: 10.3969/j.issn.0258-2724.2017.04.019

[Abstract](563)

Abstract:
The majority of previous studies on train control process safety focused on individual subsystems; this approach lacks wholeness and ignores the risk-sharing problem introduced by information transfer between different subsystems. Here, a three-level system, namely a computer-based interlocking system, train control system, and centralized train control system, was modelled from the perspective of information passing between subsystems, and the structural brittleness of the train control process was analysed. First, the structural brittleness of the high-speed railway train control process was stated according to brittleness sources, the brittleness propagation path, and the system crash standard. Then, a simulation platform was set up for system brittleness analysis based on the I/O file stream in CPN Tools and C# programming language, and a simulation example was designed. The results show that the average correlation between sub-transitions in the movement authority request submodel is 56.72%, and that in the CTCS-3 submodel is 9.56%; these results provide a reference for the differentiated typical safety management strategy.

Optimization Methods for Bidirectional Green Wave Control Based on Speed Volatility Interval

XIA Jingxin, TAO Yumeng, JIAO Tiantian

2017, 30(4): 802-809. doi: 10.3969/j.issn.0258-2724.2017.04.020

[Abstract](579)

Abstract:
In order to overcome the drawbacks of traditional arterial signal coordination methods that apply parallel and equal green wave bandwidth and ignore the speed volatility of segments between intersections, a non-parallel and unequal green wave band representation is introduced here based on the segment speed volatility intervals. Additionally, a bidirectional green wave optimization control method was proposed. The optimization objective of the proposed method is to maximize the bandwidth of green waves between adjacent intersections so as to satisfy the traffic demands of the non-coordinated signal phases. Moreover, the relative offset between two adjacent intersections can be adjusted by constructing a maximum bandwidth model. An overlap test was used as a constraint condition to prevent the fracture of green waves, which realize the bidirectional green wave control for the arterial traffic signals. Taking Changjiang Road in Kunshan City as an example, Indexes in terms of efficiency were selected to evaluate the performance of the proposed bidirectional green wave optimization control method. Evaluation results show that the proposed method can effectively increase the green wave bandwidth by 11.8% and reduce traffic delays and vehicle queue lengths of the green wave phases by 15.34% and 10.86%, respectively, compared to the traditional green wave control method.

Game Model for Balanced Use of Parking Lots

DUAN Manzhen, CHEN Guang, CAO Huiyun, ZHOU Huxing

2017, 30(4): 810-816. doi: 10.3969/j.issn.0258-2724.2017.04.021

[Abstract](570)

Abstract:
To alleviate the local parking congestion problem caused by herding effect, a parking lots allocation model for individuation guidance was proposed using the Stackelberg game theory to describe the relationship between drivers and parking resources manager. In the model, the allocation plan strives for the minimum walking distance after parking and maximum perceived utility of drivers. By controlling the value of the mean parking unoccupied index difference (MPUID), the model realizes the balanced use of parking resources to avoid local congestions. To verify the validity of the proposed method, a case study was conducted to simulate the integrated traffic in Tangshan city. The results show that under the control of the model, the maximum peak parking spillover index (PPSI) decreases from 0.168 to 0.127, and the value of MPUID presents an overall downward trend. In addition, the congestion time in peak parking hours is shortened by 70 min, and the utilization of parking spaces tends to be balanced.

Dependable Clustering Method of Flight Trajectory in Terminal Area Based on Resampling

ZHAO Yuandi, WANG Chao, LI Shanmei, ZHANG Zhaoyue

2017, 30(4): 817-825,834. doi: 10.3969/j.issn.0258-2724.2017.04.022

[Abstract](571)

Abstract:
To master the complex and changeable spatial distribution characteristics of air traffic flow in a terminal area accurately, and to evaluate and optimize arrival and departure procedures effectively, the cluster problem of 3D real flight trajectories in a terminal area was addressed using a resampling technique. A clustering method that has high computation speed, good expandability, and strong dependability was also proposed. First, based on resampling and principal component analysis method, projection of high-dimensional trajectory data to low dimension was implemented based on the premise of maintaining flight characteristics. Then, flight trajectory cluster analysis and outlier trajectory detection models were presented based on the MeanShift method. Finally, the proposed method was verified using real flight trajectory data of terminal areas in order to analyse the effect of every parameter on cluster results. Experimental results show that principal components having a 96.16% accumulative contribution rate can be obtained in 0.004 s. Flight trajectory data can be well approximated by the principal components. Compared with the hierarchical clustering method, the proposed method can obtain more dependable flight trajectory clustering results which correspond to the standard arrival routes. Low similarity trajectories were detected as outliers.

Numerical Simulation of Fire-induced Smoke in Train Compartment Based on Fire Dynamics Simulation

YU Minggao, CHEN Jing, SU Guanfeng

2017, 30(4): 826-834. doi: 10.3969/j.issn.0258-2724.2017.04.023

[Abstract](572)

Abstract:
In order to examine the flow law of the fire-induced smoke in a train compartment, the study took the internal space of one compartment of the high-speed train CRH2A as a research object. Nine sets of working conditions were examined according to the states of the carriage doors, fire source power, and discharge velocity of the air curtain. The smoke flow law was numerically simulated under these different conditions using the fire dynamics simulation software. The smoke diffusion process, visibility within each area, and temperature distribution and tendency were calculated and analyzed for the internal fire. The results showed that when the doors were closed, the smoke temperature was relatively higher, the smoke layer descended more rapidly, and the visibility was lower than when the doors were open. In addition, a higher value for the fire power resulted in a higher value for the actual total heat releasing rate. Under the conditions that the fire source power was 0.2 MW and the doors were open, the best value for the outlet velocity of the air curtain was 5 m/s in consideration of the effectiveness of the preventive smoke and economic factors. These research results have specific theoretical and practical significances in relation to the guidelines for the efficient prevention and control of a train fire.

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2017 Vol. 30, No. 4