• 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. 2

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Fuzzy Comprehensive Evaluation of Bridge Reinforcement Scheme Based on Uncertain AHP
YANG Yongqing, YANG Deng, YU Qu
2019, 54(2): 219-226. doi: 10.3969/j.issn.0258-2724.20170227
[Abstract](547) [FullText HTML] (236) PDF 555KB(6)
Abstract:
To enable the fuzzy evaluation of the bridge reinforcement scheme to be more reliable and solve the problem that the fuzzy process of the evaluation index was too simplistic and the analytic hierarchy process（AHP）had a strong subjectivity when determining the weight of the evaluation index in the existing evaluation methods, a new evaluation index system, evaluation grade, and evaluation index classification standard were established. According to the fuzzy mathematics theory, the membership function of the index and the two-level fuzzy comprehensive evaluation model of the bridge reinforcement scheme were constructed. Based on the group decision making principle, an uncertain AHP method based on expert credibility was established to calculate the weight interval of the evaluation index. The relative weight analysis method was used to convert the weight range of the index into digital weight, and then the evaluation index was weighted. Further, combined with the fuzzy comprehensive evaluation method, a fuzzy comprehensive evaluation model based on the uncertain AHP method was established and applied to the calculation and analysis of engineering examples. The results show that the method is suitable for the fuzzy evaluation of a bridge reinforcement scheme, which is consistent with engineering practice and has high feasibility and rationality.
Time-History Analysis of Temperature Field of Medium-Low Maglev Guideway Girder
DAI Gonglian, YANG Linghao, WEN Wangqing, ZHAO Tao
2019, 54(2): 227-234. doi: 10.3969/j.issn.0258-2724.20170554
[Abstract](556) [FullText HTML] (252) PDF 1558KB(3)
Abstract:
To master the laws of time-varying temperature fields of maglev girders generated by long-term environmental loading, thermal sensors were installed on a concrete guideway girder in the Changsha Maglev Express. By performing up to 1.5 a of site monitoring, the time-history curve of points was obtained. A method based on the time-series addition model is presented. With this method, the original temperature is decomposed into uniform temperature and fluctuating temperature, and the time-history curves of both temperatures are analysed using the Fourier curve fitting method. Then, the time-varying temperature field of the guideway girder is determined. The results show that uniform temperature is relevant to the climate, and each point is basically the same, reflecting the trend of the original temperature. The overall time-history curve of the girder can be expressed as a cosine function with a median value of 20.41 ℃, amplitude of 12.61 ℃, initial phase of 20 d, and cycle of 365 d. The fluctuating temperature is mainly because of solar radiation, and the curves fluctuate near the zero line. Two sine functions can be used to fit the rising and falling time-history curves.
Review of Bridge Foundation Scour
XIANG Qiqi, LI Yadong, WEI Kai, WANG Shunyi, YAO Changrong
2019, 54(2): 235-248. doi: 10.3969/j.issn.0258-2724.20170373
[Abstract](1158) [FullText HTML] (568) PDF 917KB(152)
Abstract:
Scour is one of the key causes of bridge failures. This paper presents a comprehensive review of the current research on scour at bridge foundations from five aspects: mechanism, calculation, modelling, monitoring and countermeasures, load and deformation. Based on the mechanism of scour around bridge foundations, different formulae developed for calculating scour depth are compared and analysed, and the limitations of the existing formulae are summarized. The results of numerical and laboratory models established for the scour studies are presented, along with a summary of the experimental and simulation limits. Moreover, a summary of monitoring methods with their advantages and disadvantages, as well as the countermeasures with their mechanisms and the effects on lateral load and deformation of bridge pillars is given. Finally, the future research trends of bridge foundation scour are presented, which provides some reference for research, design, and construction.
Effects of Oscillation Amplitude on Nonlinear Motion-Induced Force for 5 ∶ 1 Rectangular Cylinder
LIN Siyuan, LIAO Haili, WANG Qi, XIONG Long
2019, 54(2): 249-259. doi: 10.3969/j.issn.0258-2724.20170573
[Abstract](544) [FullText HTML] (248) PDF 1860KB(83)
Abstract:
Investigations on the nonlinear motion-induced force acting on a rectangular cylinder with aspect ratio 5∶1, which is significant in the analysis of nonlinear aeroelastic behaviour for bluff sections, are part of fundamental and cutting-edge research on bluff body aerodynamics. Combined with surface synchronous pressure measurement, forced motion wind tunnel tests were carried out to investigate the influence of oscillation amplitude on the spectral characteristics of motion-induced force and pressure distribution for a 5∶1 rectangular cylinder. After analyzing the pressure distribution mode based on the proper orthogonal decomposition (POD) method, the mechanism for nonlinear motion-induced force was discussed. Experiments and analysis indicate that the higher harmonics in the motion-induced force acting on a 5∶1 rectangular cylinder only shows significant proportion when the section is under pitching motion and the amplitude exceeds 8°, while the linear components grow nonlinearly with the increase of oscillation amplitude. When the rectangular cylinder rotates with amplitude less than 8° or oscillates vertically, the reattaching point is near the trailing edge and remains stable during the period of motion. Vortices on the top surface shed directly into the wake flow and the corresponding pressure mode is symmetric, all of which suggest that the motion-induced force is determined by a main vortex with single frequency. When the rectangular cylinder rotates with amplitude greater than or equal to 8°, the first symmetric pressure mode along with the second and third anti-symmetrical pressure mode appear simultaneously. The corresponding reattaching point is concentrated at the leading edge, so that vortices continue to develop along the model surface. These suggest the existence of several vortices with different frequencies. The secondary vortex with a frequency larger than the motion frequency leads to the occurrence of higher pressure mode, and results in higher harmonics in motion-induced force.
Fatigue Evaluation and Crack Propagation Characteristics of Rib-to-Deck Welded Joints in Steel Bridge Decks
HUANG Yun, ZHANG Qinghua, YU Jia, GUO Yawen, BU Yizhi
2019, 54(2): 260-268. doi: 10.3969/j.issn.0258-2724.20180129
[Abstract](1809) [FullText HTML] (494) PDF 1461KB(35)
Abstract:
To investigate the fatigue crack growth characteristics and establish a fatigue life evaluation method for rib-to-deck (RTD) welded joints in orthotropic steel decks (OSDs), the influence of different simulation methods of fatigue crack propagation and material properties were considered. The OSD under heavy traffic in a highway bridge crossing the Yangtze River was taken as the research object, and fatigue tests and numerical simulation based on fracture mechanics were carried out. The fatigue life of RTD welded joints corresponding to cracks that originated from weld roots was reasonably predicted, and associated fatigue crack growth characteristics were revealed. The research results show that the relative errors between the predicted fatigue life under constant amplitude fatigue loading and measured values are less than 10%, and the assessment results tend to be safe. Fatigue crack growth paths and shape changes are basically consistent with those observed from fatigue testing. Simulation methods for fatigue crack growth, calculation criteria for kink angle, material parameter values, and initial crack depth are key factors that influence fatigue life prediction. Fatigue cracks initiated from weld roots are mixed-mode cracks dominated by mode I. The influence of mode II and mode III should be taken into account in fatigue life prediction. The crack shape shows the typical characteristic of a spatial curved surface with an aspect ratio between 0.20 and 0.63, and the maximum kink angle is 12.7°. The predicted fatigue life is fairly sensitive to the initial crack depth, which should be derived with reasonable consideration of engineering practice.
Multi-View Image Precise Texture Mapping Method Based on Frame Buffer
ZHU Qing, WENG Qiqiang, HU Han, WANG Feng, WANG Weixi, YANG Weijun, ZHANG Pengcheng
2019, 54(2): 269-278. doi: 10.3969/j.issn.0258-2724.20170878
[Abstract](539) [FullText HTML] (266) PDF 1742KB(7)
Abstract:
Detailed texture mapping methods for building 3D models normally select the best matching image for each single face. However, face associated single images often have partial occlusion problems that impact the quality of mapped textures. An accurate multi-view image texture mapping method based on frame buffer rendering is presented here. First, the coordinates of the single independent building model and the triangle mesh model produced using oblique photogrammetric data were registered. Following this, rendering primitives based on spatial characteristics of the single independent building model were extracted. Subsequently, rendering cameras for the triangle mesh model were established depending on the rendering primitives. Using the Render to Texture (RTT) method, textures corresponding to rendering primitives from a frame buffer object (FBO) are obtained while rendering the triangle mesh model using the rendering cameras. Finally, the textures of the surface of a detailed building model were remapped using rendering primitives, and automatic texture mapping was achieved from the triangle mesh model to form a detailed single independent building model. The usage of oblique photogrammetry data demonstrates that the occupation of the defective textures is reduced by over 14% using our proposed method compared to the traditional method, and the size of the textures were compressed to 14.21% with more accurate texture mapping quality, thereby satisfying the texture reconstruction requirements for a detailed building model.
Structural Features and Evolutionary History of Qiaojia Pull-Apart Basin
PEI Xiangjun, LI Tiantao, HUANG Runqiu, WANG Shuang
2019, 54(2): 278-286. doi: 10.3969/j.issn.0258-2724.20170206
[Abstract](599) [FullText HTML] (360) PDF 1335KB(5)
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In order to explore the features, formation and evolution process of the Qiaojia Basin, detailed field investigation was carried out. Firstly, based on the investigation, the basic geological background conditions of the study area and the sedimentary characteristics of the basin surface were mastered. Further, the borehole survey was carried out on the central area of the basin, and the internal structural characteristics of the basin were obtained. Combing with the regional geological background and the structural characteristics, the formation and evolution process of the basin was analyzed. The results show that the Qiaojia Basin is a typical pull-apart basin, which is mainly controlled by the Xiaojiang Fault. The internal structure of the basin mainly includes five stratigraphic sequences: the alluvial layer of the ancient river, the hydrostatic sedimentary layers, the debris flow alluvium, and the river terraces. It is first discovered that a large-scale damming event occurred 3 km from the downstream boundary of the basin about 30 000 years ago. It is presumed that the basin formed during the late Tertiary period, and later experienced the effects of pull-apart process, damming process, debris flow events, and alluvial events. Through rigorous analysis and research, the evolution process of the basin was divided into 6 stages: regional dislocation, local pull-apart rifting, rift lake deposition, barrier lake deposition, barrier lake breaking, and uneven lifting.
Preliminary Investigation into Inversion of 2015 Mw7.8 Nepal Earthquake Based on GPS Data
XU Rui, ZHANG Rui, LIAO Hua, GU Tie, CHEN Cong
2019, 54(2): 287-295. doi: 10.3969/j.issn.0258-2724.20160860
[Abstract](493) [FullText HTML] (236) PDF 2090KB(1)
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To explore the potential effect and advantage of near-field high rate GPS data on the real-time inversion of seismic characteristics of large earthquakes, 16 high rate GPS sites, affected by the 2015 Mw 7.8 Nepal earthquake, were utilized independently. The kinematic GPS data processing method, real-time moment tensor inversion algorithm, and trailing variance technique were used to replay the earthquake triggering, real-time centroid and moment tensor inversion, and ending judgement of the event. The problems found during the inversion and in the final results were discussed, and then compared to the GCMT, W-phase, and some already published results. The potential advantage of a GPS real-time displacement field in determining these parameters was explored. The GPS time series shows that, if rupture propagation is in one direction and is from west to southeast, the average speed is about 3.1 km/s and the duration of the event is at least 75 s. All these results are consistent with previously published findings. GPS derived centroid and moment magnitude values are consistent with GCMT and W-phase results and have high stability and reliability.
Analysis of Vibration Reduction and Vibration Measurement for Long-Span Railway Station Floor Slab
YU Zhixiang, HU Guanghua, LI Tongmei, FENG Dubei
2019, 54(2): 296-303, 342. doi: 10.3969/j.issn.0258-2724.20170746
[Abstract](486) [FullText HTML] (232) PDF 2792KB(1)
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To reduce the vibration of a cross-line station induced by long heavy trains and improve its comfort and safety, the vibration responses of a long-span elevated railway station waiting room floor slab were studied with measured data and finite element methods. The vibration level was evaluated by 1/3 octave method, and a method of suppressing the vibration of the floor slab via tuned mass damper (TMD) energy dissipation was proposed. The results show that the predominant frequency of floor vibration is in the vicinity of 6.3 Hz, and the average vibration response level due to vehicle acceleration exceeds the permissible value of 11.0–12.6 dB when a heavy long train passes through the cross-line beneath the waiting hall floor. After adding a mass damper with a mass ratio of 0.1 to each floor slab, the insertion loss of the vibration response level reached 13.0–17.0 dB, and the vibration level of the dampers were within the standard limit.
Seismic Performance of Owner-Built RC Frame Structures in Nepal
PAN Yi, WANG Zhongkai, QU Zhe, ZHAO Chongjin
2019, 54(2): 304-312. doi: 10.3969/j.issn.0258-2724.20170755
[Abstract](534) [FullText HTML] (240) PDF 1509KB(8)
Abstract:
The 2015 Ms8.1 Gorkha earthquake in Nepal caused severe damage to local dwellings in Northern Nepal. Compared with brick-wood buildings, stone masonry, or adobe structures, owner-built reinforced concrete （RC） frame structures with masonry infills, which are commonly seen in both urban and rural areas in Nepal, sustained less severe damage. The seismic capacity of typical RC frame structures with masonry infills, which are representative of the local practice in Nepal, was compared with that of confined masonry structures conforming to the Chinese seismic design practice. The comparison was made in terms of lateral strength, ductility, and a previously proposed seismic capacity index through nonlinear static analysis. The analysis results on buildings with different numbers of stories show that the owner-built RC frames with masonry infills in Nepal exhibit higher ductility when the structural layout and amount of reinforcement are similar. However, their seismic capacity decreases significantly as the number of stories increases. For three and four-story buildings, owner-built RC frames exhibit higher seismic capacity compared with confined masonry structures in Intensity 8 regions in China, but exhibit much lower seismic capacity than the latter when the building is five stories or more.
Flexural Fatigue Performance of Concrete Prepared with Low-Heat Portland Cement
WU Xiaomei, GAO Qiang, DING Hao, FAN Yueming
2019, 54(2): 313-318. doi: 10.3969/j.issn.0258-2724.20160817
[Abstract](536) [FullText HTML] (213) PDF 811KB(5)
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To investigate the influence of cementing materials on the fatigue performance of concretes, the flexural fatigue performance of concretes prepared with low-heat Portland cement and ordinary Portland cement at different stresses was studied by a four-point bending fatigue test method. Additionally, the relationship between microstructure and fatigue performance was studied by using DTA-TG, SEM, and MIP methods. It was observed that in comparison to the ordinary Portland cement, the low-heat Portland cement is favourable for the improvement of the fatigue life of the concrete under the same stress lever (0.75–0.90). As the curing age was extended from 28 days to 180 days, the flexural fatigue life of both the kinds of concrete with a loading of 3.49 MPa was increased by 230 452 times in low-heat Portland cement concrete and 8 168 times in case of ordinary Portland cement concrete. The fatigue life of low-heat Portland cement concrete on the 90th day and 180th day was 4.76 and 19.88 times higher than that of ordinary Portland cement concrete, respectively. The longer the curing age the better the anti-fatigue performance of low-heat cement concretes. The microstructure study indicated that low-heat Portland cement concrete consisted more C-S-H gel and less Ca（OH）2. Furthermore, low-heat Portland cement concrete had lower increase (less than 10%) on the most probable pore size; and the proportion of large pores after fatigue loading reduced the crack propagation and enhanced the anti-fatigue performance.
Simplified Analysis of Wind-Induced Response of Transmission Tower-Line System Considering SSI Effect
WANG Zhisong, LIU Xinglong, WU yanjun, JIANG Peng, LI Zhengliang
2019, 54(2): 319-327. doi: 10.3969/j.issn.0258-2724.20170715
[Abstract](505) [FullText HTML] (310) PDF 3265KB(7)
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Analysis and design of transmission tower is normally performed considering fixed base, however, in most cases, the foundations are not rigid. In this study, a simplified calculation model of transmission tower-line system was developed with consideration of the soil-structure interaction （SSI）, and the dynamic equation of wind vibration response was derived. Based on the proposed simplified calculation model and MATLAB program, a transmission tower-line system from an actual project was selected to conduct the analysis of the dynamic characteristics and the time domain analysis of wind vibration of transmission tower. The model was tested and analysed with three different types of soil. The results show that the RMS displacement of transmission tower increases by about 20%, the RMS acceleration is reduced by about 14% and the maximum base shear and the base bending moment decrease by about 7% and 12%, respectively, when considering the SSI effect. The displacement response of transmission tower increases, but the acceleration changes are small if the tower line coupling effect and SSI effect are considered. As the soil hardness decreases, the SSI effect is more obvious; hence, the SSI effect should not be ignored when the transmission tower is built on soft soil.
Influence of Porous Seabed Characteristics on Wave Forces Acting on Monopile
CHEN Linya, LIAO Chencong, DUAN Lunliang, ZHENG Dongsheng
2019, 54(2): 328-335. doi: 10.3969/j.issn.0258-2724.20170800
[Abstract](472) [FullText HTML] (249) PDF 1282KB(3)
Abstract:
This study investigated the wave attenuation and wave forces acting on the monopile due to porosity characteristics of the seabed. A three-dimensional numerical analysis model of wave-porous seabed-monopile-interactions is established, in which the modified Reynolds-averaged Navier-Stokes (RANS) equation and Forchheimer saturation drag model are used to control porous flow, while the fluid volume method (VOF) is used to track free surface. Based on the proposed model, wave attenuation induced by porous seabed is first studied, taking into consideration the interaction between waves and porous seabed. Second, the numerical variation of the wave forces acting on the monopile under the same wave action with porous seabed or rigid seabed is analysed, highlighting the necessity of considering the porous characteristics of the seabed. Finally, the influence of the seabed porous characteristics on the numerical variation of the wave forces is further studied using the single variable control method. The numerical results show that the porous characteristics of the seabed have obvious attenuation effect on wave propagation. Additionally, under the given wave parameters and the characteristics of the porous seabed, the maximum wave forces acting on the monopile is about 35% higher than that of the rigid seabed. This suggests that ignoring the porous characteristics of seabed will result in an underestimation of the wave forces and could cause security risks. In addition, the wave forces acting on the structure are closely related to the porous characteristics of the seabed. The results show that the maximum wave forces decrease as the particle size increases, while increasing first and then decreasing with an increase of porosity. One thing to note is that porosity affects the variation trend of wave forces acting on monopile changing with seabed thickness.
Load Mechanisms and Design Method for Karst Subgrade Reinforced by Horizontal Geosynthetic Reinforcement
ZHANG Dongqing, XUE Yuan, LUO Qiang, LIU Wanru, ZHENG Yongfei
2019, 54(2): 336-342. doi: 10.3969/j.issn.0258-2724.20170784
[Abstract](545) [FullText HTML] (228) PDF 869KB(0)
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In order to solve the problem that the existing design methods do not consider the frictional effect of the horizontal reinforcement, and the deformation of the railway surface was underestimated, the load mechanism for railway karst subgrade reinforced by horizontal geosynthetic reinforcement was studied and a new design was proposed. Firstly, the mechanism of load transfer and mechanical model were indicated. And then, from the perspective of strictly controlling the deformation of railway subgrade surface, on the basis of the existing design methods, taking into account the frictional effect, assuming that the strain in anchorage zone changes linearly, the correction formula of reinforcement deflection was established by introducing the relaxation length. Furthermore, the design method considering the frictional effect for railway karst subgrade reinforced by horizontal reinforcement was put forward; in addition, the verification content and design process were also proposed. Finally, the method proposed was applied to a model test, and the result was compared with the results of model test and numerical analysis. The research results show that: considering the frictional effect can effectively modifier the calculated deformation of subgrade surface, which can increase from 0.18 m to 0.25 m, and was close to the model test value of 0.23 m and the numerical analysis value of 0.21 m; the method proposed is reasonable and can provide reference for actual design.
Control Factors and Assessment Technique of Relative Density Using Pluviation Method for Saturated Model
WANG Hai, WANG Yongzhi, YUAN Xiaoming, FANG Hao, DUAN Xuefeng, TANG Zhaoguang
2019, 54(2): 343-350, 372. doi: 10.3969/j.issn.0258-2724.20170477
[Abstract](527) [FullText HTML] (386) PDF 1562KB(32)
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Accurate control of relative density (Dr) in saturated pluviation method is the fundamental requirement for low relative density sample preparation of dynamic centrifuge liquefaction tests. To achieve an evaluation method on pluviation stability, a set of duckbill pluviator which fits saturated modeling was developed. Three groups of dry and saturated sand model contrast tests were carried out to identify the impacts of nozzle size, drop distance and movement velocity, aiming to assess the capability of the developed sampling device. A mini dynamic penetrometer facility was applied to measure the spatial distribution of the saturated model’s Dr, giving a homogeneity evaluation of the models. A particle-flow-velocity model for pluviation was derived to give a normalize criteria for density stable control. The results show that the optimal size of nozzle is 3mm which satisfies the requirements of low compactness modeling. The change rate of Dr with thickness of water is 3.5 times of that with air drop height, indicating that thickness of water layer is the dominant factor on Dr of saturated model. The nozzle movement velocity is up to 31% of particle velocity which is non-trivial on the low density sample preparation. The travelling speed and drop height play a decisive role in particle flow velocity and Dr.
Change Rule of Crack Widths of CRTSⅡTrack Slab
ZHU Yongjian, ZHAO Guotang
2019, 54(2): 351-358. doi: 10.3969/j.issn.0258-2724.20170201
[Abstract](514) [FullText HTML] (206) PDF 1346KB(1)
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To study the influence of longitudinal connection forming process of track structure on track slab cracks, a 1/4 unit track slab separate model was established, and the crack problems were analysed. By studying the track structure longitudinal connection forming process, Ⅱslab was found to have unique longitudinal connection and structure characteristics. Based on these, the influencing factors and the change rule of crack widths both in the middle and at the end of track slab were analysed, respectively, when its temperature decreased 30 ℃ and 40 ℃. The results show that with the bonding state weakening between the track slab and mortar layer, the crack width at the end of track slab ${\omega _{\rm{k}}}$ increases slightly, while the crack width in the middle of track slab ${\omega _{\rm{z}}}$ decreases slightly; ${\omega _{\rm{k}}}$ can be increased by 0.032 1 mm at most if track slab has no cracks. Moreover, ${\omega _{\rm{k}}}$ can be increased by 0.026 9 mm at most and ${\omega _{\rm{z}}}$ can be decreased by 0.026 9 mm at most if the track slab has a crack in the middle. The most influential factors on ${\omega _{\rm{k}}}$ are the initial stress at the end of tensioned rebars, and the initial compressive stresses of narrow joints when wide joints harden; there is also the question of whether track slab has a crack in the middle or not. The initial stress at the end of tensioned rebars, when wide joints harden, is the most influential factor on ${\omega _{\rm{z}}}$, and the more it decreases, the smaller ${\omega _{\rm{z}}}$ is. Both ${\omega _{\rm{k}}}$ and ${\omega _{\rm{z}}}$ are distributed unevenly as a result of the longitudinal connection characteristic of track slab, and the numerical value of ${\omega _{\rm{k}}}$ is large because of the weak connection between track slabs. When track slab temperature decreases 30 ℃ and 40 ℃, respectively, numeric ranges of ${\omega _{\rm{k}}}$ are 0.182–1.906 mm and 0.389–2.546 mm respectively, and ${\omega _{\rm{k}}}$ is larger than ${\omega _{\rm{z}}}$usually, which are consistent with the crack characteristics of Ⅱ slab track at present.
Experimental Investigation of Basic Mechanical Properties of Self-Compacting Recycled Aggregate Concrete
XIANG Xingyun, ZHAO Renda, LI Fuhai, LIAO Ping
2019, 54(2): 359-365. doi: 10.3969/j.issn.0258-2724.20160811
[Abstract](444) [FullText HTML] (315) PDF 714KB(10)
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In order to study the basic mechanical properties of the self-compacting recycled aggregate concrete（SCRAC）, the cubic compressive strength test, the axial compressive strength test, the splitting tensile strength test, and the elastic modulus test were carried out. The failure process and the failure mode of the SCRAC under compression and tension were observed. The effects of the recycled coarse aggregate（RCA）replacement ratio on the basic mechanical properties of the SCRAC were analyzed. The applicability of the conversion relationship between each mechanical property index of the ordinary concrete and the recycled aggregate concrete to the SCRAC was discussed. The test results show that the failure mode of the SCRAC under compression and tension is similar to that of the ordinary concrete. The test results also show that the cubic compressive strength, the axial compressive strength, the splitting tensile strength, and the elastic modulus of the SCRAC decrease by 15.5%, 12.7%, 25.6%, and 11.5%, respectively, and the peak strain of the SCRAC increases by 19.8%, when the RCA replacement ratio increases from 0 to 100%. The test results also demonstrate that RCA replacement ratio has no significant effect on the Poisson ratio of the SCRAC. The research findings indicate that the conversion relationship between each mechanical property index of the ordinary concrete and the recycled concrete is not applicable to the SCRAC, and the proposed conversion relationship between the cubic compressive strength and the other mechanical property indices of the SCRAC has high precision.
Influence of Multiple Factors on Compressive Strength of Magnesium Oxychloride Cement Concrete
GONG Wei, QIAO Hongxia, YU Hongfa, MA Haiyan, CHEN Guangfeng
2019, 54(2): 366-372. doi: 10.3969/j.issn.0258-2724.20180042
[Abstract](497) [FullText HTML] (251) PDF 542KB(14)
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The compressive strength of magnesium oxychloride cement concrete in western regions of China was studied. The adaptability of the Taguchi method in mix proportion design of concrete was also studied. The effects on the compressive strength of magnesium oxychloride cement concrete were studied utilizing the following variables: molar ratio of active MgO to MgCl2, fly ash, water resistance modifier, and the percent of water reducer. Through quantifiable characterization, the impact of these variables on the compressive strength of magnesium oxychloride cement concrete was determined. A multivariate nonlinear regression model was proposed to determine the signal-to-noise ratio of magnesium oxychloride cement concrete. When designing for the 28 day compressive strength, it was concluded that the optimum magnesium oxychloride cement concrete composition is as follows: molar ratio is 5.4, no fly ash, 1% phosphoric acid as a water resistance modifier, and 1% water reducing agent. The impact of the variables from largest to smallest is as follows: water reducer, fly ash, molar ratio, and percent of water resistance modifier. However, when designing for the long-term compressive strength, the optimal composition of magnesium oxychloride cement concrete is as follows: molar ratio is 5.4, no fly ash, 2% phosphate fertilizer as the water resistance modifier, and 1% water reducing agent. The impact of these variables also changes, and the effects in order from largest to smallest are: molar ratio, fly ash, water-resistant modifier, and water-reducing agent percentage.
Study on Partial-Wear-Factor Model Monorail Vehicle Running Wheel
DU Zixue, WEN Xiaoxia, YANG Zhen, ZHENG Shengbao, ZHOU Juchao, WANG Guolin
2019, 54(2): 373-380. doi: 10.3969/j.issn.0258-2724.20170349
[Abstract](460) [FullText HTML] (230) PDF 917KB(5)
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Frequent tire changes caused by running tire abrasion play an important role in affecting the cost of monorails. For rapid assessing the partial wear state of monorail vehicle running wheels on the different vehicle design, the factor analysis method was adopted to study the 10 evaluation indices that influence partial wear, the partial-wear factor model was established and a method was proposed for evaluating the merits and demerits of vehicle design schemes by the score of running wheels’ partial wear factor. The findings indicate the principal factors influencing partial wear in order of importance are the horizontal and vertical parameters, wheel base orientation, vertical stiffness of the running wheel, and vertical distance of the guiding wheel. The partial-wear-factor model and the partial-wear-factor score formula can quickly and reliably be used to evaluate the partial-wear state of the running wheel in different monorail vehicle structure designs. It provides an effective optimization design method for the development of bogies for monorail vehicles.
Influence of Ca Content on Ultra-High Cycle Fatigue Fracture Behavior of AMCa Magnesium Alloy
ZHANG Yanbin, SUN Dongyang, ZHANG Jiwang
2019, 54(2): 381-387. doi: 10.3969/j.issn.0258-2724.20170831
[Abstract](374) [FullText HTML] (201) PDF 1706KB(2)
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In order to investigate the effect of Ca content on the fatigue properties of magnesium alloys, the ultra-high cycle fatigue tests were carried out for two AMCa magnesium alloys using a rotating bending fatigue machine. The fracture morphologies of the fatigue specimens were observed by using scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Based on the experimental results, the fatigue S-N (fatigue strength-fatigue life) curves features and the fatigue fracture behavior were analyzed. Then, the influence of the Ca content on the fatigue life and fatigue crack initiation mechanism was discussed. The results indicate that the S-N curve of the AM1.77 Ca magnesium alloy shows a trend of continuous decline without a traditional fatigue limit, and the AM1.85 Ca magnesium alloy shows double S-N curve characteristics with a turning point around 130 MPa. The fatigue crack initiation mode is the surface initiation mode for the AM1.77 Ca magnesium alloy. However, the AM1.85 Ca magnesium alloy has two types of fatigue crack initiation modes, namely, the surface initiation mode and sub-surface initiation mode, which is due to the increase in the Ca content. The change that AM1.85 Ca magnesium alloy has two types of fatigue crack initiation modes is not conducive to improve the anti-fatigue performance.
Simulation of Passenger Traffic Network Reliability Restoration in Urban Agglomeration
LI Chengbing, LI Fengxiao, WANG Luyao
2019, 54(2): 388-394, 401. doi: 10.3969/j.issn.0258-2724.20170813
[Abstract](410) [FullText HTML] (170) PDF 1298KB(0)
Abstract:
To effectively repair an urban agglomeration passenger traffic network under attack and restore network function in time, an optimization method of network reliability restoration was studied. Firstly, the characteristics of an urban agglomeration passenger traffic network were explored, and the site mapping method was adopted to construct a network model thereof. Secondly, three attack strategies of random attack, deliberate attack, and the incomplete attack were analized. A cascade repair mechanism of an urban agglomeration passenger traffic network was explored, and a reliability repair mechanism model of this network was constructed. Then, a reliability measurement index was put forward. Finally, considering Hu-Bao-E urban agglomeration as the research object, a simulation analysis was carried out under the condition of information fuzziness of 1.0, 0.8, 0.2, and 0, respectively. The optimal repair methods under various attack strategies were obtained through a comparison of index changes. According to the results, under a random attack strategy, preference repair is the optimized strategy; nodes repair and edge repair can be maintained at 0.65 and 0.87, respectively. Under the deliberate attack strategy, the key repair effect is remarkable, and the repair degree can be maintained at about 0.70. Under the incomplete information attack strategy, the optimization strategy of reliability restoration of urban agglomeration passenger traffic network depends on the size of information fuzziness. Moreover, the harm of the node attack is greater than that of the edge attack. Hence, relevant departments should pay more attention to the construction and regular maintenance of urban agglomeration passenger traffic network sites.
Action Mechanism of Coaching Technology in Life System from Perspective of System Theory
OUYANG Yankun
2019, 54(2): 395-401. doi: 10.3969/j.issn.0258-2724.20170708
[Abstract](388) [FullText HTML] (175) PDF 586KB(4)
Abstract:
To further explore and promote the role and value of coaching technology in supporting the coordinated development of individual life system, and to further support the development of life system, this study applies the scientific concept of system theory and the overall perspective to analyze and research the coaching technique based on the input and output of individual life system, considering the influence of the core elements of life system. The study focuses on deconstructing the four core elements of the life system and the interaction and relationship between them. It also analyses the input function of these four core elements from five aspects and the effective output performance on the overall coordinated development of life system. After a thorough research, it is found that coaching technology can effectively promote the awareness of thinking mode and support emotional awareness and perception, as well as management. It can also effectively promote the power of action, while increasing energy state and improving mental models. Therefore, coaching technology can effectively support the whole coordinated development of the personal life system and help achieve growth and success from the inside out.
Optimal Sensor Placement of EMU Frame Based on Frequency Response Function
PENG Zhenrui, ZHANG Nan, YIN Hong, DONG Kangli
2019, 54(2): 402-407, 414. doi: 10.3969/j.issn.0258-2724.20170780
[Abstract](413) [FullText HTML] (191) PDF 1167KB(3)
Abstract:
To realize both location and quantity optimization, a method of optimal sensor placement based on a frequency response function is proposed. First, the structure modal analysis was conducted and mode shapes were extracted, and the frequency response function of the structure was calculated. Then, based on independent component analysis and the K-means clustering method, the sensors’ positions were optimized. Finally, the Fisher information matrices and their entropies corresponding to the placement results with different numbers of sensors were calculated. The number of sensors corresponding to minimum information entropy is the optimal number. The simulation results of the CRH3 frame show that all sensors are placed near the maximum stress positions, meeting the UIC615-4 standard, and also show that the result of sensor placement can maximize the information with limited sensors.
Semi-Supervised Method for Chinese Word Sense Disambiguation
ZHANG Chunxiang, XU Zhifeng, GAO Xueyao
2019, 54(2): 408-414. doi: 10.3969/j.issn.0258-2724.20170178
[Abstract](473) [FullText HTML] (264) PDF 560KB(7)
Abstract:
To solve the problem of a word having multiple meanings in the natural language processing (NLP) field, a semi-supervised disambiguation method, that uses a range of word sense disambiguation (WSD) models and linguistic knowledge has been proposed in this paper. First, words, parts of speech and translations were used as discriminative features, which were extracted from word units adjacent to the left and right of an ambiguous word. A word sense classifier was constructed using a Bayes model, following which a word sense classifier based on a maximum entropy (ME) model was constructed. Second, a Co-Training algorithm, based on a multitude of unannotated corpora, was adopted to optimize the WSD model. Third, optimization experiments were conducted in which training corpus in SemEval-2007: Task#5 and a large number of unannotated corpora from Harbin Institute of Technology were applied to optimize the Bayesian classifier and the maximum entropy classifier. Finally, the optimized WSD model was tested. Test results demonstrate an increase in the disambiguation accuracy of the proposed method by 0.9% compared to WSD models based on support vector machines, thereby exhibiting an improvement in WSD performance.
Lane Line Detection and Recognition by Polarisation Imaging
WANG Huifeng, ZHANG Jiajia, ZHAO Xiangmo, WEI Feiting, WANG Guiping
2019, 54(2): 415-420. doi: 10.3969/j.issn.0258-2724.20160412
[Abstract](388) [FullText HTML] (203) PDF 1008KB(3)
Abstract:
The detection of lane lines in an adverse environments is a complex and popular topic in both assisted safe driving and intelligent vehicle research. An optical polarization theory was introduced into traditional lane detection technology, aimed at external adverse road environments. In addition, a lane-line detection method was proposed based on imaging polarization by analysing the basic features of the lane line image. Firstly, a three-angle special environment road polarization-image was collected to obtain a polarization degree image. Secondly, the polarization degree images were converted by binarization, divided first into regions of interest, and then according to the straight-line feature of the lane edge before the edge detection of road images were conducted; hence, the actual lane line edge could be obtained. Finally, the improved Hough algorithm proposed through the Hough transform principle could detect the lane marking; and the vehicle driving deflection angle was calculated. The simulation and experimental results demonstrate this method can accurately detect and identify the lane line in an adverse environment with an error of less than 0.3° between the detected and actual declination angle of the lane line.
Quantum Colour Image Encryption Algorithm Based on Chaotic Systems
ZHANG Jian, HUO Da
2019, 54(2): 421-427. doi: 10.3969/j.issn.0258-2724.20170443
[Abstract](452) [FullText HTML] (229) PDF 961KB(10)
Abstract:
To enhance the security of image data, the incorporation of a chaotic system with quantum image encryption was proposed. Bitwise XOR operation was performed on a test image by applying the Chen chaotic system, and the obtained colour image was expressed as a quantum superposition state. The unitary matrix generated by the logistic chaotic sequence was then employed for scrambling the quantum image. In addition, to achieve the objective of quantum image encryption, another chaotic sequence was generated for randomly interchanging the red, green, and blue colour components of each pixel in the quantum image. Results obtained from simulation experiments conducted on a classical computer demonstrate that the grey histogram of the encrypted image is smooth, and the pixel intensity range is distributed uniformly between the values of 0 to 255. The correlation between adjacent pixels is found to be low, with the correlation coefficient values being 0.001 6, 0.001 7, and 0.003 8 for the red, green, and blue channels, respectively. Furthermore, the high key sensitivity of the proposed algorithm can effectively resist high intensity, exhaustive, and statistical attacks. Hence, the proposed algorithm can feasibly provide the required security for image data.
Parallel Genetic Algorithm for SAT Problems Based on OpenMP
WU Guanfeng, XU Yang, CHANG Wenjing, CHEN Shuwei, XU Peng
2019, 54(2): 428-435. doi: 10.3969/j.issn.0258-2724.20170700
[Abstract](501) [FullText HTML] (312) PDF 784KB(15)
Abstract:
To improve solving efficiency for SAT (boolean satisfiability) problems, a combination of genetic algorithm (GA) with local search algorithm (LSA) on the OpenMP (open multi-processing) framework was proposed. This combination improved the selection algorithm in the hybrid genetic algorithm (HGA) and reduced the time complexity of the original selection operation to O(N). The compiler guide statement #pragma omp parallel in OpenMP was applied to coarse-grained parallelization driven HGA, and the #pragma omp single statement block was used to implement the synchronization migration operation of the individuals in different sub-groups. Compared with the similar algorithm, HCGA (hybrid cloud genetic algorithm), both the improved algorithm (HGA) and the coarse-grained parallel hybrid genetic algorithm (CGPHGA) significantly improved solution success rate and problem solving efficiency. Solution success rate for some problems was increased by 5 times.
Overview of Type-Reduction Algorithms for Type-2 Fuzzy Logic Systems
ZHAO Taoyan, LI Ping, CAO Jiangtao
2019, 54(2): 436-444. doi: 10.3969/j.issn.0258-2724.20170060
[Abstract](350) [FullText HTML] (360) PDF 539KB(22)
Abstract:
The computation precision, computation time, and the loss of system information of the type-reduction process have a great influence on the performance of type-2 fuzzy logic systems. In this paper, the basic concept of type-2 fuzzy sets and the computation process of type-2 fuzzy logic systems are briefly introduced. Then, a detailed review of the research on type-reduction algorithms is given for both interval type-2 fuzzy logic systems and generalized type-2 fuzzy logic systems. The computational complexity of different type-reduction algorithms is analyzed and compared. Finally, the problems faced with each type-reduction algorithm are summarized, and potential future research directions are presented. The computation cost of type-reduction algorithms remains as the bottleneck in type-2 fuzzy logic system improvement. The key direction of future research should be the improvement of the theory behind type-reduction algorithms, the solving of the computational complexity through mathematical methods, and applying this to real-time systems.

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