• ISSN 0258-2724
  • CN 51-1277/U
  • EI Compendex
  • Scopus
  • Indexed by Core Journals of China, Chinese S&T Journal Citation Reports
  • Chinese S&T Journal Citation Reports
  • Chinese Science Citation Database

2019 Vol. 54, No. 4

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Control Strategy Based on State Machine for Fuel Cell Hybrid Power System
CHENG Weirong, YAN Yu, LI Qi
2019, 54(4): 663-670. doi: 10.3969/j.issn.0258-2724.20170279
[Abstract](625) [FullText HTML] (328) PDF 1069KB(47)
Abstract:
For the hybrid tram power system that consists of two sets of high-power fuel cells, supercapacitors and power batteries, an energy management strategy based on state machine is proposed to meet the requirements of operating conditions. First of all, the state machine is adopted as the basic architecture, and the operating state of the tram is divided into four states: traction, coasting, braking and fault. Then the energy management strategies that correspond to four states are studied. The voltage equalization algorithm based on the adaptive discharge coefficient is used in the traction state; and in the coasting state, the improved maximum efficiency point tracking algorithm is used. Then, according to the four operating states, the actual operation of the tram is carried out. Finally, the power consumption and the fuel cell system efficiency between the state-machine based control strategy and power tracking strategy is compared. The results show that the voltage equalization algorithm enables two sets of supercapacitors to be uniformly discharged in the traction state, which avoids the overuse of a single set of supercapacitors. The improved maximum efficiency point tracking algorithm increase the average efficiency of the fuel cell by 3.91%. In addition, the stack efficiency of the state-machine based control strategy and the power tracking strategy is 61.89% and 57.98%, respectively, and the former saves 3.2% of hydrogen.
Multi-Objective Optimum Design for in-Wheel Motor Based on Improved Artificial Bee Colony Algorithm
ZHANG Heshan, DENG Zhaoxiang, TUO Jiying, ZHANG Yu, TAO Shengchao
2019, 54(4): 671-678. doi: 10.3969/j.issn.0258-2724.20170094
[Abstract](646) [FullText HTML] (315) PDF 1202KB(39)
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In order to improve the power density of the in-wheel motor and reduce its material cost, an improved artificial bee colony (IABC) algorithm was proposed to optimize the performance of the in-wheel motor. Firstly, the expressions for the performances of the permanent-magnet in-wheel motor with outer rotor were established by magnetic circuit method. Secondly, individual extremum, population extremum and a pair of asynchronous scaling factors were introduced to overcome the shortcomings of traditional artificial bee colony (ABC) algorithm, such as slow convergence speed, and imbalance in exploration and development. The effective mass, power loss and material cost of the motor were linearly weighted to form a single objective function with the electromagnetic parameters such as number of pole pairs, air-gap clearance and permanent magnet thickness as design variables, and the constrained non-linear objective function was transformed into a non-constrained one by the barrier function method. Finally, the genetic algorithm (GA), traditional ABC algorithm and IABC algorithm were used to optimize the design of the in-wheel motor respectively. The correctness of the calculation results was verified by finite element method and prototype experiment. The results show that the IABC algorithm makes the objective function converge faster than the traditional ABC algorithm. Compared with the GA and traditional ABC algorithm, the IABC algorithm minimizes the objective function value. Compared with the original design, the effective quality of the in-wheel motor is reduced by 13.4%, material cost is reduced by 34.4%, power loss is reduced by 44.2%, and the efficiency is increased by 12.0%.
Influence of Electrode Gap on Characteristics of Dielectric Barrier Discharge
LI Chunmao, DONG Lei, PENG Kaisheng, WEI Wenfu, GAO Guoqiang, WU Guangning
2019, 54(4): 679-685, 693. doi: 10.3969/j.issn.0258-2724.20170444
[Abstract](551) [FullText HTML] (320) PDF 1332KB(25)
Abstract:
To gain a better understanding of the influence of the electrode gap on the SDBD (surface dielectric barrier discharge) actuator discharge characteristics, plasma extension, and power consumption were analysed using a camera and oscilloscope under different electrode gaps. Meanwhile, the temperature distribution around the exposed electrode was measured and discussed based on images from an infrared thermal imager. The variations in the induced flow velocity and body force were recorded using a Pitot and an electron balance, and the mechanism of variations of four parameters under different gaps is discussed respectively. The results indicate that all four discharge parameters first increase and then decrease with this gap, and an optimum electrode gap of an SDBD actuator discharge exists under a fixed discharge voltage. A reference is also provided for achieving a preferable airflow control using an SDBD actuator.
Contamination Degree Prediction of Insulators Based on Hyperspectral Imaging Technology
LI Hengchao, TAN Bei, YANG Gang, SHI Chaoqun, ZHANG Xueqin, WU Guangning
2019, 54(4): 686-693. doi: 10.3969/j.issn.0258-2724.20180267
[Abstract](552) [FullText HTML] (244) PDF 1520KB(36)
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Insulator image can be acquired by hyperspectral imaging technology in a non-contact way, and hyperspectral image has some advantages such as the properties of multi-band, and merging image and spectrum. For this reason, the paper proposes a method to predict contamination degree of insulators based on hyperspectral imaging technology. Firstly, the hyperspectral image in a band range of 400–1 000 nm is acquired by hyperspectral imaging system, followed by the black-and-white correction. Then, some reflectivity spectrum curves of region of interest (ROI) are extracted and further pre-processed by the methods such as the Savitzky-Golay smoothness, logarithm, or first derivative transformations. Finally, some labeled data of real samples are utilized to build support vector machines based insulator contamination degree prediction (SVM-ICDP) model and partial least squares regression based insulator contamination degree prediction (PLSR-ICDP) model, respectively. The experimental results show that when the first derivative transformation is selected as the pre-processing method, the performance of the ICDP model is superior to those of the others. More specifically, the accuracy of SVM-ICDP reaches 91.84%, and the root mean square error (RMSE) of PLSR-ICDP is 0.024 1.
Fatigue Performance of Orthotropic Steel Decks with Thickened Edge U-Ribs
ZHENG Kaifeng, HENG Junlin, HE Xiaojun, ZHANG Yu
2019, 54(4): 694-700. doi: 10.3969/j.issn.0258-2724.20170555
[Abstract](596) [FullText HTML] (277) PDF 1154KB(20)
Abstract:
The fatigue performance of rib-to-deck (RD) joints is expected to be enhanced by the application of the orthotropic steel deck (OSD) with thickened edge U-ribs (TEUs). To investigate its actual fatigue performance and the mechanism of enhancement, the RD joints in the OSD with TEUs using the fatigue test and numerical analysis was evaluated.Through the fatigue model test of full-scale specimens, comparative analysis was performed on the OSD with conventional U-ribs (CUs) and the OSD with TEUs,in the test, both the nominal stress and hot spot stress approaches were incorporated. A refined finite element (FE) model was established based on the test, and validated by the test data. Using the model, numerical analysis was carried out to study the mechanism of the enhancement in RD joints by the application of TEUs.The results show that: the use of TEUs improve the fatigue strength of rib-to-deck joints effectively; in the presence of negative welding errors, the specimens with TEUs are relatively insensitive to the variations in unpenetrated thicknessthat leading to the robustness of the fatigue strength of rib-to-deck joints. The fatigue performance of the OSD with TEUs has been further validated through its application in several engineering projects such as New Sanyuan bridge in Beijing and Fenghuangshan Viaduct in Chengdu.
Trigonometric Series Solution of Bending Deformation for Composite Beam with Steel Corrugated Webs
YE Huawen, WANG Liwu, ZHANG Qing, XU Xun, WEI Xing
2019, 54(4): 701-708, 723. doi: 10.3969/j.issn.0258-2724.20170277
[Abstract](506) [FullText HTML] (242) PDF 957KB(18)
Abstract:
In order to study the influence of shear deformation on the bending deformation of composite beams with steel corrugated steel webs, trigonometric series solution was introduced to simulate the deformation of the components (web and flange) of the beam according to the plane-section assumption, and a theoretical model was presented on the basis of the principle of minimum potential energy. Then, analytical solutions and respective simplified forms were derived for simply supported and cantilever corrugated steel web girder cases under uniform distribution and mid-span concentrated load. Furthermore, a limit value of depth-span ratio was suggested to estimate the influence of shear deformation with regard to magnifying coefficient of deflection. Validity and usability of the analytical solution and the model were determined by the finite element method. The results show that the presented method has advantages of ease in boundary condition and deduce, high reliability and universal applicability, and can be referred for deflection design of steel corrugated steel web beam.
Lower Vertical Frequency Limit for Simply Supported Box-Girder on Moscow-Kazan High-Speed Railway Line
SONG Xiaodong, QIU Xiaowei, LI Xiaozhen, LIU Dejun, GUO Jianxun
2019, 54(4): 709-714. doi: 10.3969/j.issn.0258-2724.20170306
[Abstract](441) [FullText HTML] (248) PDF 893KB(20)
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To study the lower vertical basic frequency limit of a simply supported box-girder on the Moscow-Kazan high-speed railway line, firstly, the vertical fundamental frequency of the prestressed concrete (PC) simply supported box-girder was calculated with theoretical formula. Then, according to the principle of the bridge dynamic effect under the action of a moving train should not surpass that of the designed value, the allowable impact factor of the girder was determined by utilizing the finite element method. Secondly, based on the moving load model, the dynamic simulation analysis was conducted to obtain the impact factor of the simply supported box-girder under a moving train. Finally, the lower vertical basic frequency limits of the PC simply supported box-girder for design speeds of 250, 300, 350 km/h, and 400 km/h were recommended. The results show that the peak of the dynamic response amplitude of the girder will appear at the first bend natural frequency. Adjusting the vertical basic frequency of the bridge can effectively reduce the vibration peak, which compensates for the vertical excitation frequency caused by the moving train. The lower vertical basic frequency limits of the 33.1 m span PC simply supported box-girder for design speeds of 250, 300, 350 km/h, and 400 km/h are recommended as 3.02, 3.63, 4.08 Hz, and 4.68 Hz, respectively.
Influence of Section Types on Noise from Elevated Rail Transit Lines
GU Minjie, LI Wuqian, LI Qi
2019, 54(4): 715-723. doi: 10.3969/j.issn.0258-2724.20180262
[Abstract](516) [FullText HTML] (240) PDF 2771KB(12)
Abstract:
Simply-supported pre-stressed concrete bridges are widely adopted in urban elevated rail transit systems. The section types of the bridges not only affect bridge vibration and structural acoustic radiation, but also have an indirect influence on the propagation of wheel-rail noise. Thus, this work aims to provide guidelines on the selection of section types of bridges for low noise produced by elevated rail transit systems. The power flow method was first applied to obtain the spatially averaged vibration velocities of the rail and bridge considering wheel-rail interaction. The coupled finite-infinite element method was then used to analyze the generation and propagation of rail noise and bridge structural noise. The vibrations and noise radiation of the bridges of U-shaped girder, single-box single-cell box girder, and twin-box twin-cell box girder were compared. The results reveal that although the section types have a small effect on the vibration of the rails, they have large influence on rail noise radiation. Furthermore, both the vibration and structural noise of the bridges are significantly affected by the section types. In terms of rail noise, the U-shaped girder leads to 1-3 dB(A) lower rail noise level than the box girder. However, with respect to the bridge structure noise, the single-box single-cell box girder generates noise 2-10 dB(A) lower than the U-shaped girder, and the twin-box twin-cell box girder generates noise 2-6 dB(A) lower than the single-box single-cell box girder.
Vortex-Induced Vibration Performance and Control Measures of Wide Twin-Box Girder
MA Cunming, WANG Junxin, LUO Nan, LI Hongjiu, LIAO Haili
2019, 54(4): 724-730. doi: 10.3969/j.issn.0258-2724.20161029
[Abstract](554) [FullText HTML] (231) PDF 1197KB(29)
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In order to study the vortex-induced vibration (VIV) characteristics and control methods of wide twin-box girder bridges, a long-span suspension bridge with twin-box girder and a total girder width of 64.1 m was modeled in a 1∶70 scale ratio and wind tunnel tests for this model were carried out under smooth flow. Firstly, the VIV characteristics of the girder under five attack angles (0°, ± 3°and ± 5°) were studied; secondly, the effects of single aerodynamic measures, including using a horizontal aerodynamic plate, closed central gap, grids and guide plates on overhaul vehicle rail and the effects of the measure combinations were also studied. Finally, the influence of the above aerodynamic measures on the flutter performance of the main girder is examined. The results show that the vertical DOF vortex-induced resonance occurs at all five wind attack angles. The most unfavorable attack angle is –3°, and the maximum vertical vibration amplitude is 0.69 m, which exceeds the limit of the allowable value in Wind-Resistent Design Specification for Highway Bridges by 70%. The combined use of grid and other aerodynamic measures can reduce the VIV amplitude of the main girder by 50.7%–98.6%. However, these control measures reduce the critical flutter wind speed by 6%–15%, which still meets the design requirements.
Effect of Pule-Like Ground Motion on Seismic Performance of Concrete-Filled Steel Tubular Arch Bridge
LI Xi, HE Lan, LI Qian, PAN Yi
2019, 54(4): 731-740. doi: 10.3969/j.issn.0258-2724.20180855
[Abstract](563) [FullText HTML] (277) PDF 1318KB(17)
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To study the seismic performance of a concrete-filled steel tubular (CFST) arch bridge under pulse-like ground motions, a comprehensive theoretical analysis is made of an actual CFST arch bridge under the action of non-pulse-like and pulse-like ground motions using time history analysis. The actual ground motion records with different pulse periods are first selected for each site condition based on the PEER (pacific earthquake engineering research center) ground motion models using the spectrum match method. Then, a comparative seismic analysis of the CFST arch bridge is conducted with and without consideration of pulse, different pulse periods and the dimensionality of ground motions. Results show that the pulse-like ground motions can significantly affect structural responses; a better bridge site condition results in a larger structural responses, and the amplification factor is between 0.96–19.88. Meanwhile, the difference of pulse periods induces significant variations in structural responses, the change rate is between 10%–133%; the smaller the pulse period is, the more obvious the amplification effect on the structural response is. In addition, the dimensionality of ground motions has smaller effect on structural responses under pulse-like motions than the one under non-pulse-like ground motions, but the effect intensifies as the pulse period decreases. Therefore, it is suggested that not only the pulse effect but also the influence of pulse period, dimensionality of ground motions and site conditions for the location of the bridge should be considered in the seismic design phase of a CFST bridge to avoid erroneous response predictions.
Numerical Study on Wave-Induced Oscillatory Liquefaction in Anisotropic Seabed
DUAN Lunliang, ZHENG Dongsheng, WANG Shaohua, ZHANG Qibo
2019, 54(4): 741-747. doi: 10.3969/j.issn.0258-2724.20170810
[Abstract](559) [FullText HTML] (249) PDF 1243KB(18)
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In order to investigate the wave-induced oscillatory liquefaction in an anisotropic seabed, a two-dimensional numerical model for wave-seabed interactions is proposed. The reynolds-averaged navier-stokes (RANS) equation with the standard k-ε turbulence model was used to describe wave motions, and Biot’s poro-elastic equation was taken as the governing equation for the seabed model. After validation with previous experimental data and analytical solution, the proposed model was further applied to investigate the effects of wave and soil characteristics on anisotropic soil liquefaction. Numerical results show that the maximum liquefaction depth increased with an increase in wave height and wave period, and decreased with the degree of soil saturation. When the value of the soil permeability coefficient along the vertical direction is within a certain range, the effects of soil permeability along the vertical direction on the wave-induced soil response are obvious. Beyond the range, however, the effects of soil permeability along the vertical direction are almost negligible. Besides, the wave-induced oscillatory liquefaction depth in an anisotropic seabed is not sensitive to the variations in soil permeability along the horizontal direction.
Large Eddy Simulation of Aerodynamic Noise Field Around Super High-Rise Buildings
ZHU Zhiwen, DENG Yanhua
2019, 54(4): 748-756. doi: 10.3969/j.issn.0258-2724.20180066
[Abstract](538) [FullText HTML] (230) PDF 1312KB(22)
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In order to reveal the mechanism and spatial distribution characteristics of aerodynamic noise around super high-rise buildings, the flow field around super high-rise buildings in the atmospheric boundary layer is solved by using large eddy simulation (LES), and the sound pressure field is numerically calculated by the acoustic analogy method (Ffowcs Williams-Hawkings, FW-H). The result shows that each surface of super high-rise buildings can be regarded as a source of dipolar noise. The aerodynamic noise is generated by a dipole source on building surfaces and is dominated by the wind pressure on those surfaces. The radiation intensity of the sound fields in the along-wind and cross-wind directions is controlled by the corresponding fluctuating pressures. Aerodynamic noise first increases and then decreases with the height, with the maximum value arriving at the approximately 70% of the building height. For spatial points with the same height and distance to building surfaces, the highest total sound pressure will occur at the points facing the building's windward surfaces, followed by that at the points facing the building's leeward surfaces. The lowest total sound pressure will appear at the spatial points facing the building's side surfaces. With the increase of the distance between spatial point and building, the total sound pressure level decreases rapidly. The total sound pressure level decreases more rapidly in the cross-wind direction than in the along-wind direction. This work suggests that the LES method combined with the acoustic analogy method is a feasible way to predict aerodynamic noise produced by super high-rise buildings. The most effective way to reduce the noise level is to reduce the wind pressure on building surfaces by optimizing its aerodynamic shape.
Instability Properties and Deformation Control Methods of Rocks Surrounding Xigeda Strata
WANG Zhijie, ZHOU Ping, YANG Jianmin, CAO Xiaochuan, ZHAO Qichao, XU Haiyan, XU Ruining
2019, 54(4): 757-768. doi: 10.3969/j.issn.0258-2724.20170257
[Abstract](497) [FullText HTML] (243) PDF 1575KB(32)
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Xigeda strata are a type of fluvio-lacustrine deposit with half-diagenesis in southwest China, characterized by bad water stability; the deposits become mud and collapse when they come into contact with water; therefore, disasters are possible during the process of tunnel excavation. Large deformations of the surrounding rocks and collapse are the ill effects during constructions of traffic tunnels. Thus, relying on the Tong Zilin, Ya Kou, and Yan Bian tunnel engineering in the Xigeda formation in the Pan-xi region, and based on the field sampling and indoor laboratory tests of the mechanical properties of the surrounding rocks, finite element models of the shallow and deep Xigeda strata tunnels under different water content were established simultaneously to study the instability properties of the surrounding rocks of Xigeda strata for different water content and to explore the deformation control methods accordingly. The results show that Xigeda formation is sensitive to water, and the light-gray shale embedded with sandstone is most affected by water in its physical and mechanical properties. The deformation of the surrounding rocks increases when the water content ranges from 0% to 25%, but the deformation degree is small. When the water content ranges from 20% to 25%, the degree of deformation increases significantly, and there is increased possibility of instability. Under the conditions of large buried depth and high water content, accumulated deformation of the tunnel invert uplifting and tunnel face extruding increase sharply, followed by accumulated deformation of the vault. The tunnel face extruding deformation mainly occurs in the junction between the upper step and middle step. According to the instability properties of the surrounding rocks of Xigeda strata, construction methods of the surrounding rock with the rock either being shale embedded with sandstone or sandstone embedded with shale are examined for conditions where water is either present or absent.
Experiment Study on Non-limit Passive Earth Pressure of Clay under Different Displacement Modes
XIA Junwu, DOU Guotao, SU Qiong, BAI Weigang, YUAN Fang
2019, 54(4): 769-777. doi: 10.3969/j.issn.0258-2724.20170343
[Abstract](528) [FullText HTML] (282) PDF 1398KB(25)
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In order to reveal the depth distribution law of the non-limit passive earth pressure of clay on a rigid retaining wall under different displacement modes, translation and rotation experiments were carried out using the self-made model box. The influence of the three modes and corresponding displacement on the lateral earth pressure were studied. Firstly, laboratory experiments were carried out, and the basic physical parameters of clay were obtained. Secondly, the model box and test instruments were installed. Finally, earth pressure experiments under three modes of the retaining wall: translation (T-mode), rotation around the top of the retaining wall (RT-mode), and rotation around the bottom of the retaining wall (RB-mode) were carried out. The following conclusions are reached: In the T-mode, the lateral earth pressure generally increased with increasing soil depth except in some local parts, presenting an approximately linear distribution. When the soil reaches the limit state, step-like staggered floors are formed in the vicinity of the wall; In the RT-mode, the lateral earth pressure grow more slowly in the upper wall but more quickly in the lower wall as depth increased, presenting a concave curve. When the soil reaches the limit state, cracks are formed in the vicinity of the wall, and the soil summones up in the middle of the box; In the RB-mode, the lateral earth pressure grow more quickly in the upper wall but more slowly in the lower wall as depth increased, presenting a convex curve. When the soil reaches the limit state, step-like staggered floors are formed in the vicinity of the wall, with the scope smaller than that in the T-mode. The resultant forces of these three lateral earth pressures increase with increasing compressive displacement, reaching the maximum increasing magnitude in the T-mode. When the compression displacement is the same, the ratio of the earth pressure resultant force in the RT-mode and T-mode is between 0.53 and 0.97; the ratio of the earth pressure resultant force in the RB-mode and T-mode is between 0.65 and 0.83.
Effect of Coarse Grain Content on Shear Strength of Mixed Soil in Western Sichuan
CUI Kai, SU Lei
2019, 54(4): 778-785. doi: 10.3969/j.issn.0258-2724.20180826
[Abstract](513) [FullText HTML] (279) PDF 745KB(12)
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Mixed soil is widely distributed in the west of Sichuan, and the stability of the highway subgrade made up of mixed soil in mountainous areas is an issue needing urgent attention and research in engineering practices. Considering that mixed soil shear strength is affected greatly by the content of coarse particles, the natural mixed soil used for subgrade in mountain areas of Western Sichuan was chosen and used in small and large direct shear tests to systematically study the influence of the coarse grain content on the shear stress-displacement curve and internal friction angle of the mixed soil. Experimental results show that the shear strength of mixed soils changes significantly with the coarse grain content, and presents different variation tendencies in different coarse grain content ranges. When the coarse grain content increases from 0 to 30%, the internal friction angle grows slowly. With the coarse grain content increasing from 30% to 60%, the growth rate of the internal friction angle becomes faster; and then it slows down again beyond the content of 60%. Therefore, there are two threshold values formed, which can be explained from skeleton theory. Differences in the main influencing factors of shear strength in different ranges are finally analyzed from macro and micro aspects, which can provide the reference value and theoretical basis for mixed soil structure stability evaluation.
Effect of Wetting-Drying Cycles on Mass and Deformation of Cement and Emulsified Asphalt Mortar
ZHOU Xiling, XIE Youjun, ZHENG Keren, ZENG Xiaohui
2019, 54(4): 786-792. doi: 10.3969/j.issn.0258-2724.20180261
[Abstract](402) [FullText HTML] (234) PDF 808KB(19)
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The varying humidity of service environment due to the change of weather and climate has a significant influence on the mass and volume of CA (cement and emulsified asphalt) mortar, which further influences the geometrical size of track structure. To understand the effect of the variation of ambient humidity on the mass and size of CA mortar in service, 6 kinds of wetting-drying cycles were designed in which the mass and length changes of CA mortar were measured. To investigate the mechanism of length change, pore structure and phase composition were examined by low field nuclear magnetic resonance (NMR) and thermogravimetric analysis-differential scanning calorimetry (TGA-DSC). The results show that with the increase of cycle numbers, the wet mass of CA mortar firstly increases rapidly and reaches the maximum value, then starts to decline, and stabilizes at about 140 days, and the dry mass of CA mortar changes a little; however, the length change exhibits an initial decrease and then increase trend. In wetting-drying cycles, the mass and length changes of CA mortar are less than that under continuous air-drying or water immersion condition. During the wetting-drying cycles with short periods, an evident quadratic function relationship between mass change and deformation of CA mortar can be found before around 140 days, after which the correlation converts into a linear relationship; however, the correlation is not significant during the wetting-drying cycles with long periods. The results obtained from NMR and TG-DSC indicate that the migration of capillary water, hydration of cement, carbonization, and the change of pore structure are the joint reasons accounting for the mass and length changes of CA mortar.
Optimization Evaluation of Quality Classification of Concrete with Recycled Coarse Aggregate
LI Fuhai, JIN Hesong, YU Yongjiang, HU Zhiming, WANG Yibin
2019, 54(4): 793-800, 815. doi: 10.3969/j.issn.0258-2724.20170786
[Abstract](513) [FullText HTML] (224) PDF 682KB(16)
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In order to overcome the errors caused by the subjective and discretionary factors of the recycled aggregate, select their quality scientifically and reasonably, a quality evaluation model for concrete with recycled coarse aggregate was established based on the combined weight-extension theory. According to the standard of concrete with recycled aggregate, the evaluation index system and limits of classification level were determined, the subjective and objective weights of each indexes were determined by the analytic hierarchy process (AHP) and entropy weight theory. The sample correlation degrees of each indexes under different levels were solved based on the extension theory, and then the correlation function values of the sample under different levels were calculated combined with the combination weight method. The quality grades were evaluated according to the principle that the bigger the number, the better the quality, finally, the scientificity of the evaluation method was tested by examples. The results show that: comprehensive evaluation method based on combined weight-extension theory not only follow the evaluation steps of the single factor method, but also can sort and compare the results under different levels of indicators; the quality grades of the five samples groups are calculated as II, I, I, II, and I, respectively, which are consistent with the evaluation results used by previous fuzzy theory; three weighting methods can not only calculate the specific weight values of seven performance indexes of the recycled coarse aggregate, but also can reflect the relative importance of each indexes. The study on the quality optimization of recycled coarse aggregate can provide a theoretical reference for the engineering application of recycled concrete.
Evaluation Method of Maximum Shear Modulus of Cohesionless Soil Based on State Parameters from Piezocone Penteration Test
DUAN Wei, CAI Guojun, LIU Songyu
2019, 54(4): 801-807. doi: 10.3969/j.issn.0258-2724.20170432
[Abstract](418) [FullText HTML] (227) PDF 865KB(20)
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The maximum shear modulus of soil is an important parameter for dynamic design of foundations and response analysis of seismic sites. At present, this parameter is mainly determined through laboratory tests, but such tests cannot represent the real situation in the field. Thus, in situ testing technologies have attracted much attention. The Suqian-Xinji Expressway was regarded as the engineering background and seismic piezocone test (SCPTU) was conducted at the site. Based on the summary of research results for existing methods used to determine the maximum shear modulus, the relationship between the piezocone penetration test (CPTU) parameters and the maximum shear modulus was studied in terms of the reference value of the maximum shear modulus calculated using the measured shear wave velocity. The relationship between the joint CPTU parameters, state parameters, and maximum shear modulus was also analysed. The results show a good correlation between the maximum shear modulus and CPTU parameters. The maximum shear modulus value can be approximated by cone tip resistance and pore pressure parameters. The state parameter can serve as an effective alternative parameter for void ratio or pore pressure parameter ratio, and the dual factors of confining pressure and void ratio can be considered simultaneously. The estimated maximum shear modulus is the same as the reference value. Therefore, the in situ state parameters of CPTU can be used as a new method to evaluate the maximum shear modulus of cohesionless soil.
Ring-Net Subdivision Equivalent Model of Flexible Protection System
ZHAO Yana, YU Zhixiang, ZHAO Shichun
2019, 54(4): 808-815. doi: 10.3969/j.issn.0258-2724.20170949
[Abstract](456) [FullText HTML] (196) PDF 1917KB(22)
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The ring-net is an important interception component in passive flexible protection systems, and it has obvious nonlinear dynamic characteristics. Constructing a mechanical model of the ring network is the key problem in the theoretical study of the flexible protection structure. To propose an equivalent mechanical model of the ring net, an full-scale impact test was conducted with an actual structure, and the regional deformation characteristics of the ring-net and typical deformation state of the ring-net were obtained. Then, the load-displacement relationships of the net ring under typical deformation states were obtained using a tension test and numerical simulation calculation; on these bases, a subdivision equivalent calculation model was established.. Finally, the accuracy of the model was verified by comparison with the breaking and dynamic impact tests. Results show that the deformation of the ring net has obvious regional characteristics, and the ring-net (basic unit of the net) displays three typical deformation states (each with two-stage characteristics). Based on this, an ‘X’ type 4-truss element, connected to the centre of the circle with the initial length of the ring radius, is used to simulate a single ring. The load-displacement relationship of the ring in a typical deformation state is treated as equivalent to the stress-strain relationship of the truss element, and the corresponding nodes are connected to form the element model of the entire ring-net. A comparison with the static and dynamic tests indicates that the model calculation error is less than 10%.
Effect of Computational Grid on Uncertainty in Train Aerodynamics
LI Tian, QIN Deng, AN Chao, ZHANG Jiye
2019, 54(4): 816-822. doi: 10.3969/j.issn.0258-2724.20180503
[Abstract](463) [FullText HTML] (189) PDF 1309KB(20)
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To evaluate the effect of computational grid on the numerical simulation results of train aerodynamics in open air, the uncertainty of the computational grid on train aerodynamic characteristics is studied based on computational fluid dynamics. First, according to the grids of three sizes and the corresponding calculation results, the calculation method for the uncertainty of the train aerodynamic forces and surface pressure is proposed. Second, the ICE2 (inter-city express) train is taken as an object, three different grids are generated, and the pressure on typical cross-sections and aerodynamic forces are obtained by numerical simulation. Finally, the uncertainty of the aerodynamic forces and pressure on typical cross-sections of this train is studied. The results show that the error in aerodynamic side force coefficient between the numerical simulation and experiment is only 0.31%; the uncertainty of the surface pressure on the windward side of vehicle body is close to 0. The position with a higher uncertainty of the surface pressure is mainly located at the bottom of car body, and its maximum uncertainty is 1.42. As for the head car, the uncertainty of the side force coefficient is 0.002 6, and the uncertainty of the lift force coefficient is 0.509 3.
Decision Making Model and Method Based on Distance Measure Between Interval Numbers in Railway Location
LIANG Dong, LI Yuanfu, FAN Min
2019, 54(4): 823-830. doi: 10.3969/j.issn.0258-2724.20180847
[Abstract](480) [FullText HTML] (257) PDF 556KB(18)
Abstract:
In order to solve the problem that quantitative and qualitative indexes are difficult to be unified into comprehensive fuzzy assessment of railway location selection, the theory of interval numbers is introduced to build a fuzzy optimal selection model based on distance measure between interval numbers. First, the quantitative and qualitative indexes in railway location schemes are transformed into interval numbers to obtain an interval number decision matrix, which is then normalized into a normalized interval number decision matrix. Second, weights of evaluation indexes are calculated by the distance measure between interval numbers and a weighted normalization decision matrix is obtained. On the basis of the weighted normalization decision matrix, the railway location schemes are ranked by the distance measure between interval numbers and the optimal scheme is selected. Finally, an engineering example of railway location selection was used to illustrate the operation procedure. The results prove that compared with the traditional analytic hierarchy process (AHP) method, this model can reduce the influence of subjective reasons on decision results in quantifying qualitative indexes with uncertainty; especially, the calculation results of index weights are more reliable. In addition, the proposed method is more convenient than the traditional projection method for priority ranking of alternative solutions.
Optimization of Train Timetable for Intercity Railway Based on Coordinated Operation of Multi-periodic Trains
ZHOU Wenliang, LI Peng, TIAN Junli, DENG Lianbo
2019, 54(4): 831-839. doi: 10.3969/j.issn.0258-2724.20170153
[Abstract](473) [FullText HTML] (216) PDF 685KB(16)
Abstract:
To ensure regularity of train arrival and departure times at stations operating with strict train periodicity and timing schedules, a novel methodology for coordinated operation of multi-periodic trains is proposed. The proposed method aims to ensure a better fit for the time distribution of passenger demands in the intercity railway system and is further compared with the existing aperiodic and single periodic train operation patterns to analyze their characteristic differences. On this basis, an optimisation model aimed at minimising the total travel times of all periodical operating trains is built to solve the train scheduling problem; this involves the coordinated operation of multi-periodic trains with identical time interval constraints for each period type of trains and all safety intervals. An algorithm based on Lagrangian relaxation framework is designed and combined with the gradient method by relaxing the complex constraints via Lagrangian multiples. The proposed model is implemented numerically for Beijing-Tianjin intercity railway using its operating timetable for four periodical operating trains with intervals of 17 min, 34 min, 34 min, and 35 min. The analysis shows that their objective values differ from the optimised lower boundary by 2.55%.
Periodic and Collaborative Allocation of Berth-Yard-Gate Resources at Container Terminals
HAN Xiaole, JU Liuhong, LUAN Chen, LU Zhiqiang
2019, 54(4): 840-847. doi: 10.3969/j.issn.0258-2724.20170924
[Abstract](450) [FullText HTML] (213) PDF 804KB(12)
Abstract:
In order to improve the efficiency of import/export container terminals in periodic environment, the periodical and collaborative allocation problem of key resources at container terminals, including berth, yard and gate is investigated. A mixed-integer linear programming model is first established for the integrated scheduling of three types of resources. This model takes into account the capacity restrictions, inter-relationships and periodicity requirements, and sets the objective of minimizing total dwelling time of all vessels. Furthermore, an adaptive genetic algorithm is proposed to find a solution. As for the algorithm, the upper level performs evolutionary search within the space consisting the encoded vessel priority lists, while the lower level decodes each vessel priority to generate a complete resource allocation plan by heuristics, and returns its evaluation for upper level iteration. Numeral experiments shows that with the collaborative allocation of berth-yard-gate resources, the dwelling time of vessels in the execution of periodic plan is shortened by 20% comparing to traditional two-stage method.
Flow Field Analysis and Optimization for Internal Channel of Hydraulic Manifold Block in Lower Extremity Exoskeleton Robot
WANG Haibo, FAN Shuyuan, ZHANG Long
2019, 54(4): 848-854. doi: 10.3969/j.issn.0258-2724.20170879
[Abstract](410) [FullText HTML] (213) PDF 1158KB(10)
Abstract:
In order to deal with the excessive temperature rise and noise of the hydraulic power unit in the lower extremity exoskeleton robot, ANSYS Fluent software was used for the simulation tests of Z-channel and cross-channel, which are the main components of internal flow channel of the hydraulic manifold block. Furthermore, 5 groups of simulation test with different sizes are designed to analyze how the stability of flow velocity and pressure loss change with channel dimension. The simulation test shows that when the channel diameter is 5 mm, the pressure loss of the cross-channel increases with eccentricity between the inlet and outlet; and the stability of flow velocity is the best when eccentricity is 1.25 mm. The pressure loss of Z-channel reaches the minimum when the distance between inlet and outlet is 17 mm, and the stability of fluid velocity increases with the distance. The optimized prototype test shows that the maximum temperature of the hydraulic manifold block was decreased by 3.3 ℃ and the maximum noise was decreased by 7.6 dB.
Numerical Algorithm and Software Development for Metal Forming
ZHOU Yangjing, FENG Zhiqiang, NING Po, WANG Changyong
2019, 54(4): 855-862. doi: 10.3969/j.issn.0258-2724.20170442
[Abstract](416) [FullText HTML] (204) PDF 1283KB(10)
Abstract:
To develop a customized computer-aided engineering (CAE) software with specialized features for metal forming, based on the self-developed OmtDesk platform, a numerical algorithm for mental forming calculation is proposed. On the basis of the bipotential theory, the Uzawa algorithm was applied to addressing the frictional contact. The return-mapping algorithm was then applied in the framework of the updated Lagrangian to analyze the non-linearity of metal materials. Furthermore, two numerical tests in terms of compression springback and extrusion forming were conducted for verifying the accuracy and feasibility of the developed CAE software with the aid of FEM and Form simulation software. The results are compared with those by ANSYS. In the case of the compression springback test, the penetration value calculated by ANSYS software has a magnitude of 10–3 mm, whereas those by FEM and Form software show a penetration magnitude of 10–7 mm. This demonstrates that the proposed bipotential contact module can effectively control the penetration value in the simulation of metal forming, thereby improving the precision of the metal forming process.
Combined Neural Networks Based on Deep Learning for Signal Detection in Aeronautical Communications
HOU Jin, LÜ Zhiliang, XU Mao, WU Peijun, LIU Yuling, ZHANG Xiaoyu, CHENG Zeng
2019, 54(4): 863-869, 878. doi: 10.3969/j.issn.0258-2724.20180164
[Abstract](424) [FullText HTML] (195) PDF 1203KB(25)
Abstract:
In order to increase the generality and accuracy of radio modulation recognition in complex radio propagation environment, a multiple feature combined convolutional network system based on deep learning is proposed. Carrier features were detected with front convolutional network in the first stage. Then, the signal filtered by the front CNN was converted into spectrograms with the proposed pre-process method. Finally, the lightweight backend convolutional network was designed to extract the time-frequency features of spectrograms. The networks, which run on TensorFlow, achieved 99.23% accuracy with real airport communication signals. The experiment indicates that the proposed networks could be applied in real-time airport radio detection.
Localization Algorithm for Mine Wireless Sensor Network Based on Rigid Cluster and Chicken Swarm Optimization
YU Xiuwu, ZHOU Lixing, YU Qihao, HU Mufang, ZHANG Feng
2019, 54(4): 870-878. doi: 10.3969/j.issn.0258-2724.20180069
[Abstract](415) [FullText HTML] (243) PDF 1068KB(20)
Abstract:
In order to adapt to the restrain resulting in environment factor of mine to localization of wireless sensor network, a novel localization algorithm based on rigid cluster and chicken swarm optimization (RCCSO) is proposed. First, the clusters are set up centring on the uniformly distributed anchor nodes, expand the clusters based on rigid theory and get several clusters which are all globally rigid. Second of it, optimize the best relative position of the nodes in the same cluster by chicken swarm optimization, and get the solution sets of relative position. Then, centring on the anchor nodes, all the solution ratate for some different angle, and optimal the best solution set of ratation angles by chicken swarm optimization, and get the globally position of all the unknown nodes. Finally, Simulation comparison demonstrated that the accuracy of the new localization algorithm RCCSO is more precise than the MDS-MAP algorithm and DALSA algorithm.
Improving the Performance of Sodium Silicate for Track Slab by Promoting Polymerization and Biomineralization
LI Maohong, PAN Zhang, LING Chenbo, YAO Ning, LI Shuxian, WANG Ping
2019, 54(4): 879-884. doi: 10.3969/j.issn.0258-2724.20180599
[Abstract](391) [FullText HTML] (197) PDF 898KB(19)
Abstract:
To improve the mechanical strength and water resistance of sodium silicate used for track slab coating in high-speed railways, Ca(H2PO4)2 was added into sodium silicate to promote biomineralization and polymerization of silica gel. First, Sodium silicate modified by Ca(H2PO4)2 was prepared, using sodium silicate without adding Ca(H2PO4)2 as a control. The property of the sample was tested by universal material testing machine and water resistance testing; and the composition and microstructure of the sample were characterized by X-ray diffractometer(XRD), Fourier-transform infrared spectrometer(FTIR), and 29Si nuclear magnetic resonance instrument(29Si NMR). Results show that the addition of Ca(H2PO4)2 increased mechanical strength by 160% and improved water resistance from 2 h to more than 7 d for sodium silicate; adding Ca(H2PO4)2 into sodium silicate led to biomineralization by forming Ca8H2(PO4)6•?H2O-NaHCO3-H2O, which is the main inorganic component of Human bone with high mechanical strength and good water resistance; and Ca(H2PO4)2 promoted the polymerization of silica gel to form silica oxygen polymer with higher mechanical strength and better water resistance in sodium silicate. It is concluded that the addition of Ca(2PO4)2 greatly improved the mechanical strength and water resistance of sodium silicate after setting and hardening, which may have promising applications in track slab coating.

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