Table of Content

25 December 2017, Volume 45 Issue 12

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Food Science & Technology

Effect of Microwave Treatment on Helical Structure and Digestibility of Potato Starch

LUO Zhi-gang XU Xiao-juan CHEN Yong-zhi

2017, 45(12):  1-7.  doi:10.3969/j.issn.1000-565X.2017.12.001

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Potato starch was microwave-treated respectively with the power of 2. 06 and 6. 63W/g,and the single and double-helical structures of native and microwave-treated starches and their digestibility were analyzed by means of DSC,XRD,¹³C CP/MAS NMR and in vitro digestion，so as to reveal the effects of the microwave treat- ment on the single and double-helical structures and digestibility of the potato starch as well as the relationship be- tween the single and double-helical structures and the digestibility.The results show that (1) as the microwave power increases,the contents of the single helix，the double helices,the gelatinization enthalpy and the relative crystallinity decrease,while the amorphous components increase; (2) the low-power (2. 06W/g) microwave has a small effect on the digestibility,while the high-power (6. 63W/g) microwave significantly decreases the content of the resistant starch and correspondingly increases the contents of the slowly-digestible starch and the rapidly-di- gestible starch; (3) the microwave treatment destroys the internal single and double-helical structures of the starch and thus decreases their contents，and the extent of the destruction gradually increases with the increase of the mi- crowave power; and (4) the reduction in the contents of the single and double-helical components causes the starch digestibility to change.In addition,the low-power microwave rarely decreases the contents of the single and double-helical components and thus hardly influences the starch digestibility,while the high-power microwave sig- nificantly decreases the contents of the single and double-helical components and thus results in a drastic change in the starch digestibility.

Influence of Decolorization Procedures on Color Value and Molecular Structure of Sugar Beet Pectin

YU Shu-juan LI Tai-hong GUO Xiao-ming WANG Zhi-ming1 AI Chao GUO Xiao-bing

2017, 45(12):  8-13,77.  doi:10.3969/j.issn.1000-565X.2017.12.002

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In order to solve the dark color problem of sugar beet pectin (SBP),the methods of dialysis，alcohol leaching and H₂O₂decolorization were used to decolor the SBP solution,and the influence of the decoloring proce- dures on the decoloration effect as well as on the molecular structure and emulsifying property of the SBP was evalu- ated.It is found that neither the dialysis (MWCO is 3000 ～14000u) nor the alcohol leaching (the ethanol concen- tration is from 60% to 80%) has any influence on the color value of the SBP,while H₂O₂ can significantly reduce the SBP color value.Therefore，the influence of the H₂O₂ concentration and the bleaching time on the decoloriza- tion efficiency was investigated.The results show that，in an alkaline solution with 3% of H₂O₂ and after the bleaching at the room temperature for 0. 5h,the color value of the SBP decreases from 1. 71 to －0. 11,and the o- riginal dark yellow SBP solution turns into clear and bright solution.Furthermore,the H₂O₂ oxidation decolorization also changes the structure of the SBP,specifically，the contents of D-galacturonic acid,neutral sugar and ferulic acid in the SBP as well as the molecular mass of the SBP decrease,and the emulsifying activity of the SBP decrea- ses to 66. 7% ～75. 0% of the original.It is thus concluded that the decolorization effect of H₂O₂ on the SBP is sig- nificant,which can be attributed to the fact that the endogenous chromogenic material in the SBP is oxidized by H₂O₂ .However,the SBP is likely to be degraded when the oxidation of H₂O₂ is too strong.

Effect of Wheat Gluten Protein Hydrolysates on Metabolic Performance of Brewer's Yeast During Very High Gravity Brewing

ZHAO Hai-feng LU Min ZHOU Yong-jing YANG Hui-rong MENG He-cheng

2017, 45(12):  14-19.  doi:10.3969/j.issn.1000-565X.2017.12.003

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By a 20°P very high gravity brewing,the effects of the degree of hydrolysis (DH) and the amount of wheat gluten protein hydrolysates on the growth and fermentation performance of brewer's yeast were investigated.The results show that,after a 24h hydrolysis,the hydrolysates have the greatest DH,which is 22. 4%,and they exhibit the best promoting effect on the growth of brewer's yeast,and that,the wort supplemented with 1. 0% wheat gluten protein hydrolysates shows a significant effect on the growth and fermentation of brewer's yeast,specifically,the yeast biomass accumulation,the utilization rate of free amino nitrogen and the ethanol production are improved by 4. 6%,41. 2% and 15. 2%，respectively.The conclusions indicate that the wheat gluten protein hydrolysates can be used as effective nitrogen for the growth and fermentation of brewer's yeast during the 20°P very high gravity brewing.

Protective Effect of Corbicula Fluminea Hydrolyzates on Ethanol-Induced LO2 Cells Injury

REN Jiao-yan SHANG Shuai-ming LIANG Ming ZHANG Ting ZHOU Yong LI Hai-long YUAN Er-dong

2017, 45(12):  20-26.  doi:10.3969/j.issn.1000-565X.2017.12.004

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The antioxidant activity of the Corbicula fluminea hydrolyzates obtained by using different proteases was evaluated by measuring the scavenging activity on free radical DPPH and by oxygen radical absorbance capacity ex- periments.Then，the effect of the ethanol concentrations on LO2 cells as well as the protective effect of the hydroly- zates on the cytotoxicity of LO2 cells induced by ethanol was assessed by using the methyl thiazolyl tetrazolium (MTT) assay and by determining the activities of alanine transaminase and aspartate transaminase.Finally,the a- mino acid composition of the sample,which is the most potent antioxidant,was analyzed.The results show that the hydrolyzates have certain antioxidant ability,and that,the hydrolyzates of the concentration of 300 ～400mg/L have no cytotoxic effect on the proliferation of LO2 cells,and they can increase the cell viability of the ethanol-induced LO2 cells,of which the protective effects of the pancreatin and flavourzyme hydrolyzates are significantly better than the other ones.Meanwhile,the pancreatin and flavourzyme hydrolyzates can significantly inhibit the ethanol-in- duced ALT and AST release in LO2 cells,and the contents of the antioxidant amino acids in the pancreatin and fla- vourzyme hydrolyzates are respectively 75. 69% and 75. 06%.

Electronics, Communication & Automation Technology

Correlation of Pixels-Based Measurement Matrix for Compressed Image/Video Sensing

YANG Chun-ling LI Lin-sun

2017, 45(12):  27-35.  doi:10.3969/j.issn.1000-565X.2017.12.005

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The construction of measurement matrixes is one of the most significant issues in the compressed image/ video sensing (CIS/CVS).In order to overcome the uncertainty of random measurement matrixes and the heavy pressure in transmission and to improve the reconstruction quality in encoder ends,a novel deterministic sparse measurement matrix named adjacent-pixel-based matrix (APM) is constructed for the CIS/CVS，based on the cor- relation of adjacent pixels.During the APM construction,first,an annulus choosing method is proposed to uni- formly select the target points in the measured image block.Then,the Gaussian probability density function is adopted to distribute weights to the elements of the measurement matrix corresponding to the adjacent pixels of the target points,so as to ensure that each measurement only contains the information of one target point and its adja- cent pixels.Applying the measurement from the proposed APM in the image or video reconstruction helps take ad- vantage of the correlation between adjacent pixels and avoid the interference from the other further pixels,and thus a higher reconstruction quality can be achieved.Simulation results show that，in comparison with other classical and novel measurement matrixes in the literature,the proposed APM achieves higher image/video reconstruction quality with lower reconstruction complexity,and that it is of a wider range of application.

Energy-Efficient Cooperative Transmission for SWIPT in WSNs

KUO Yong-hong ZHOU Bi-rong CHEN Jian

2017, 45(12):  36-42.  doi:10.3969/j.issn.1000-565X.2017.12.006

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In the WSNs based on the cooperation of information and energy,the transmission power is constrained by the finite battery capacity and the lower energy efficiency.In order to solve these problems,a cooperation transmission strategy under dynamic energy acquisition is proposed.First,a cooperative transmission model for the SWIPT in the WSNs is constructed based on the finite battery capacity of nodes.Then,a distributed iteration algo- rithm integrating the fractional programming with the dual decomposition is proposed to solve a convex optimization problem,thus achieving the optimal allocation strategy corresponding to the constructed model.Simulation results and theoretical analysis show that the proposed cooperation transmission strategy achieves the maximum energy effi- ciency with a higher throughput.

Stereo Matching Algorithm Based on Improved Census Transform and Multi-Scale Space

LIU Jian-guo YU Li LIU Si-jian WANG Shuai-shuai

2017, 45(12):  43-49.  doi:10.3969/j.issn.1000-565X.2017.12.007

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In order to improve the matching accuracy of the stereo matching algorithm in a low-texture region and its cost volume consistency across multiple scales,an improved Census transform algorithm is proposed，the judge and self-adaptation of weights are conducted based on the mean information of the pixels in a window,and the matching accuracy of the pixels in a discontinuity region is improved by performing a cost calculation.Further- more,the Gaussian Pyramid is introduced in cost aggregation,the Guided image filter algorithm is integrated with the multiple-scale model，and the regularization constraint is also added to strengthen the cost volume consistency with the low-texture region.In the disparity selecting step,a series of optimization methods,such as the outlier detection，the region voting and the sub-pixel enhancement,are used to improve the correct rate of the matching.Experimental results show that the proposed algorithm achieves an average error rate of 5. 91% in the Middlebury benchmark，with a better disparity map in the low-texture and discontinuity regions,and that it is of a strong ro- bustness.

Sub-Pixel Edge Detection of Cutting Tool Images Based on Arimoto Entropy and Zernike Moment

WU Yi-quan LONG Yun-lin ZHOU Yang

2017, 45(12):  50-56.  doi:10.3969/j.issn.1000-565X.2017.12.008

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In order to meet the high-speed and high-accuracy demands of the machine vision-based measurement system of cutting tool sizes,an image sub-pixel edge detection method based on Arimoto entropy of linear intercept histograms and Zernike moment is proposed.In the method,first,the neighborhood-average grayscale of images is obtained through the Gaussian sliding window to construct a two-dimensional histogram,and the linear intercept method is adopted to reduce the two-dimensional histogram to a one-dimensional histogram.Then,aiming at the a- chieved linear intercept histogram,the thresholding is performed according to the Arimoto entropy,and the ob- tained threshold is mapped back to the two-dimensional histogram to extract a target region and pixel-level edges.Finally,the edge points are re-located by using the Zernike moment-based edge model,thus achieving the sub-pix- el-level edges of cutting tool images.By a large number of experiments on the cutting tool images,the proposed method is compared with the Canny-based,the space moment-based,the gray moment-based and the Zernike mo- ment-based edge extraction methods.The results show that the proposed method is superior in both speed and accu- racy.

Construction and Evaluation of Video Forgery Detection Database

HU Yong-jian SALMAN Al-hamidi WANG Yu-fei LIU Bei-bei LI Meng

2017, 45(12):  57-64.  doi:10.3969/j.issn.1000-565X.2017.12.009

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There has been a lack of standard video database for the research of video forgery detection.In order to solve this problem,a video forgery detection database (VFDD) is created.The database comprises 640 video clips,including the original videos captured by various imaging devices and the tampered videos created with the inter-frame and intra-frame manipulations.The details of the construction of the database are introduced.Four representative algorithms of video forgery detection in the literature are selected to perform a validity test on this da- tabase.The results show that the created database is capable of exhibiting the performance of different algorithms more comprehensively，which means that it is an effective evaluation database for video forgery detection algo- rithms.

A Feed-Forward Combined Adaptive Filter for Suppressing Motion Artifact in Ambulatory Electrocardiogram

ZHANG Huan-qian ZHANG Shu-lin DU Xiao-wei JIN Qing-hui LI Qing YANG Jian ZHAO Jian-long

2017, 45(12):  65-70.  doi:10.3969/j.issn.1000-565X.2017.12.010

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The least mean square adaptive filter (LMS-AF) and the variable step size LMS-AF (VSS-LMS-AF) have been widely used to suppress the motion artifact (MA) from ambulatory electrocardiograms (AECG).How- ever,due to the fact that the non-stationary property of the MA and the AECG increases the mis-adjustment of fil- ters,although the combined AF (C-AF) has advantages in tracking non-stationary signals，it still suffers from a signal distortion.In order to further decrease the signal distortion and improve the MA suppression ability,a new feed-forward combined AF (FFC-AF) is proposed,in which the stationary degree of the MA is estimated by using a reference signal and two parallel AF outputs are combined.Then,a simulation experiment with the AECG re- cording on ten healthy volunteers is conducted to assess the performance of the FFC-AF.The results show that,as compared with the C-AF,the FFC-AF is of less signal distortion and larger signal artifact ratio.Therefore,it can be used to suppress the MA in the AECG.

Mechanical Engineering

Influence of Decolorization Procedures on Color Value and Molecular Structure of Sugar Beet Pectin#br#

XU Xiao SHUAI Gao-peng CHENG Xiu-quan XIA Qin-xiang

2017, 45(12):  71-77.  doi:10.3969/j.issn.1000-565X.2017.12.011

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In order to research the influence of the surface shapes of the damaged aircraft parts after polishing on the distribution of residual stress,the surface shapes located in the polished area of the damaged aircraft parts are classified.The mathematical functions are adopted to describe the classified surface shapes,and the software ABAQUS is used to simulate the laser shot peening with different surface shapes and curvatures.Simulation results indicate that,after the laser shot peening,the biconcave surface bears the greatest maximum residual compressive stress,followed by the concave surface,the saddle surface,the plane,the convex surface and the biconvex sur- face,which means that the surface shape has a small effect on the depth of residual compressive stress lager.In ad- dition,with the curvature increases,the maximum residual compressive stresses of the biconcave surface，the con- cave surface and the saddle surface increase gradually,while those of the convex surface and the biconvex surface decrease,which means that the curvature has a small effect on the maximum residual compressive stress influence depth.

High Temperature Friction and Wear Characteristics of 23-8N Valve Steel

QU Sheng-guan YIN Lian-min LAI Fu-qiang XIAO Chuan-wei LI Xiao-qiang

2017, 45(12):  78-84,2.  doi:10.3969/j.issn.1000-565X.2017.12.012

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In this paper,the high temperature friction and wear characteristics of 23-8N valve steel after full aging and solid solution aging are investigated,and the microstructure and phase composition of the valve steel are also analyzed.The results show that (1) the friction coefficients and wear loss of two different heat treatment specimens both tend to decrease first and then increase with the rising of temperature; (2) at the room temperature,the full aging specimen has better anti-wear performance,and the surfaces of the two different heat treatment specimens are distributed with grooves and adhesive traces,indicating that the prevailed wear mechanism is abrasive wear and ad- hesive wear; (3) at a high temperature,the solution and aging specimen has better wear resistance due to its thic- ker oxide film; (4) at 400℃,the two specimens are covered with dense oxide films,so the wear loss of the speci- mens is the lowest and the main wear mechanism is mild oxidation wear; and (5) as the temperature rises from 500℃ to 650℃,the wear loss gradually increases,and the predominant wear mechanism transforms from mild oxi- dation wear into severe abrasive wear,adhesive wear and the fatigue delamination of oxide films.

Modeling of Virtual Topography of Abrasive Belt

HE Zhe LI Jian-yong LIU Yue-ming NIE Meng FAN Wen-gang

2017, 45(12):  85-91,105.  doi:10.3969/j.issn.1000-565X.2017.12.013

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In order to establish a virtual topography of the abrasive belt,a systematic random-polyhedron model of abrasive belt grains is constructed.Then,the average spacing of neighbor grains is measured by identifying the po- sition of the grains on the abrasive surface.Finally,by using the multi-superposition random-displacement method to realize the random configuration of the grains on the abrasive surface,a virtual topography of the abrasive belt is obtained.Furthermore,the grains with greater protrusion height are replaced by using fracture grains,thus accom- plishing the forecasting of the topography of the blunt abrasive belt.Experimental results show that,when the num- ber of random polyhedron sections is about 24 ～30 and the multi-superposition frequency is about 600,an ideal vir- tual topography of the abrasive belt can be acquired,and that,the distribution of the real abrasive belt protrusion height has a partial peak feature,and as compared with the original abrasive belt,the blunt abrasive belt achieves a lower mean protrusion height with a better protrusion height consistency.The virtual abrasive belt topography ob- tained through the proposed method in this paper can accurately characterize the new abrasive belt surface,and it can be used to forecast the topography of the blunt abrasive belt.

Analysis of Influencing Factors of PIV Experimental Measurement for Vortex Flow Field in Hydrodynamic Coupling

CHAI Bo-sen XIANG Yue MA Wen-xing WANG Zhi-hao WEI Ya-xiao LI Zhen-nan

2017, 45(12):  92-98.  doi:10.3969/j.issn.1000-565X.2017.12.014

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In order to achieve a high-precision experimental measurement of the vortex flow field in a hydrodynamic coupling,main error sources of the internal flow experimental measurement by particle image velocimetry (PIV) technology are investigated,and the influence of the tracer particle selection,the image acquisition strategy and the flow velocity extraction algorithm on the measurement precision of the internal flow field is analyzed.Then,some methods are proposed to reduce and eliminate the errors.The results show that (1) when 1. 0 g PSP tracer particles of an equivalent diameter of 1. 5 μm are put into a 2710 mL water-medium hydrodynamic coupling,the collected flow images are better and the particle concentration can meet the requirements of the PIV speed measure- ment; (2) designing the outer surface of the hydrodynamic coupling as a large plane collection area can effectively avoid the reflective phenomenon and reduce the off-axis angle error and the optical refractive error; and (3) by a- dopting the recursive cross-correlation algorithm and the adaptive interrogation window analysis method to carry out three iterations,the characteristics of both the large-scale vortex flow in a mainstream region and the small-scale vortex structure on local corners can be extracted more effectively.The conclusions will provide a vital reference for the accurate measurement of the vortex flow field in the hydrodynamic coupling．

Liquid Crystal Glass Substrate Cutting Based on Double Scribe-Wheels and Its Crack Initiation and Propagation Laws

WAN Zhen-ping ZHANG Kun FENG Jun-yuan QING Jian-bo FU Yong-qing

2017, 45(12):  99-105.  doi:10.3969/j.issn.1000-565X.2017.12.015

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The liquid crystal display (LCD) glass substrate cutting is one of the key processes in manufacturing LCD screens.In order to achieve highly-efficient and high-quality precision cutting of LCD glass substrates,a new LCD glass substrate cutting method based on double scribe-wheels is proposed,in which the first scribe-wheel is used to scribe a plastic groove on the cutting surface and then the scribed LCD glass substrate is cut by the second scribe-wheel along the plastic groove.Then,the critical load of medial crack initiation is determined by the inden- tation experiments using a symmetric wedge,and the crack initiation and propagation laws during the second inden- tation of the symmetrical wedges along the plastic groove that is generated in the first indentation are investigated.Experimental results show that (1) no lateral cracks occur during the second indentation; (2) the length of the vertical cracks increases slightly with the increase of the load imposed in the first indentation,and it increases line- arly with the increase of the load imposed in the second indentation; (3) when no lateral cracks occur,it is possi- ble to obtain the perfect fractographs without edge chippings or microcracks ［1］; and (4) the length increase of the vertical cracks makes the splitting of the substrate on the flip side unnecessary during the second cutting based on the double scribe-wheels.

Stress Characteristic of Working Attachment of Hydraulic Excavator and Selection of Dangerous Working Conditions

PANG Xiao-ping NIE Dong CHEN Jin ZOU Zhi-hong

2017, 45(12):  106-113.  doi:10.3969/j.issn.1000-565X.2017.12.016

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When the structure of the working attachment of hydraulic excavators is analyzed by means of the tradi- tional classification method,one tip position of buckets only corresponds to one attitude.Therefore,the analysis is incomplete.In order to solve this problem,by taking the working attachment as a whole,a method (MBRS-3D) of 3D atlas of the maximum stress and corresponding stress atlas based on a regional planning is proposed to explore the structural characteristics of the hydraulic excavator attachment,and the maximum stress is taken as an example to conduct an analysis.Then，the excavation resistance coefficient and the resistance moment coefficient are ac- quired by testing and statistics,and a calculation model of the theoretical digging force is constructed.Based on the regional planning of the working attachment with variable parameters,an integrated finite element analysis of the working attachment is implemented,thus obtaining the maximum stress values and the corresponding key area num- bers of the boom,the stick,the bucket and the whole excavator attachment.Afterwards,the 3D atlas of the maxi- mum stress and the corresponding region are drawn to visually describe the maximum stress value and the value dis- tribution.Finally,the dangerous working condition is selected through the proposed method,and it is compared with the classic condition.The results show that the selected dangerous working condition is more dangerous than the classic one.

Architecture & Civil Engineering

Prediction of Sound Transmission Through Diagonal Rooms Within a Residence Building

HUANG Xian-feng YANG Zong-xiao

2017, 45(12):  114-120,134.  doi:10.3969/j.issn.1000-565X.2017.12.017

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In the investigation,the diagonal rooms within a residence building are disassembled into a variety of subsystems,and the sound energy equations of the diagonal room system are set up.By solving these equations,the overall sound pressure level difference and the sound pressure level differences along each sound transmission path are predicted.Then,through the dominant sound transmission path,the parts of weak sound insulation performance within the diagonal rooms are determined,and a sound insulation prediction model is constructed.The theoretical prediction indicates that,in the whole frequency range,the dominant sound transmission path of the diagonal rooms is the flanking sound transmission path that passes through the floor wholly,and that,in the frequency range of 200 ～ 500Hz,the separating wall of lightweight material is prone to ameliorate the sound insulation between the diagonal rooms.In addition,as the developed sound insulation prediction model involves the first-and second-order flanking sound transmissions,the prediction values of the sound pressure level difference are reduced by 3 ～5dB,thus the prediction precision of the sound transmission in the diagonal rooms is improved.Therefore,the prediction model can be adopted to seek effective approaches to improving the sound insulation of a residence building.

Compressive Behavior of Rectangular Recycled Aggregate Concrete-Filled Steel-Tubular Stub Columns

YANG You-fu HUANG Xiang-yu

2017, 45(12):  121-127.  doi:10.3969/j.issn.1000-565X.2017.12.018

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By performing the tests of six specimens under axial compressive loads,the effects of the replacement ra- tio of recycled coarse aggregate and the depth-to-breadth ratio of sections on the failure pattern,the load versus de- formation relationship and the bearing capacity of the rectangular recycled aggregate concrete-filled steel-tubular (ＲACFST) stub columns were investigated.The results show that,as the recycled coarse aggregate replacement ra- tio increases,the bearing capacity,the composite elastic modulus and the relative bearing capacity index of the rec- tangular RACFST specimens decrease，while the later bearing capacity index of the specimens increases,and that,the depth-to-breadth ratio has a small effect on the relative bearing capacity index of the specimens,and the later bearing capacity index of the specimens decreases with the increase of the depth-to-breadth ratio.Finally,by selec- ting a rational constitutive model of two kinds of materials,a finite element analysis model was constructed to simu- late the compressive behavior of the rectangular RACFST stub columns.It is found that the simulated results accord well with the measured ones.

Experimental Investigation into Mechanical Performance of Steel-Concrete Composite Beams with Fatigue Damage

YANG Tao LIN Guang-tai ZHAO Yan-lin PENG Xiu-ning

2017, 45(12):  128-134.  doi:10.3969/j.issn.1000-565X.2017.12.019

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Steel-concrete composite beams are widely used in bridge structures and fatigue damage caused by vehicle loads will accumulate gradually, which is adverse to the structure safety. To study the influence of fatigue damage on the mechanical performance of steel-concrete composite beams, monotonic static tests were conducted on seven composite beams, including five composite beams previously suffered 1,000,000 cycles of constant amplitude fatigue loading. Experimental results indicated that fatigue damage due to 1,000,000 cycles of fatigue loading caused the reduction of ultimate deformability of the composite beams. However, the ductility coefficients were still greater than 4.6 and the final failure patterns belonged to flexible failures. Fatigue loading led to the strengthening effect of steel material and the yielding loads of the composite beams improved correspondingly. The ultimate bearing capacities of the composite beams with partial shear connection generally reduced and the maximum drop reached 7.3% of the initial ultimate bearing capacity. Using studs with 13mm or 16mm in diameter has no significant effect on the bearing capacity of the composite beams when they possess the same shear connection degree.

Influence of Connection Behavior on Anti-Collapse Performance of Composite Frames

GAO Shan GUO Lan-hui ZHANG Su-mei

2017, 45(12):  135-142.  doi:10.3969/j.issn.1000-565X.2017.12.020

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The beam-column connection plays a key role in the redistribution of internal force,and its behavior has a significant influence on the performance of structures in resisting progressive collapse.In this paper,a finite ele- ment model is constructed for a three-storey steel-concrete composite frame,and the influence of the connection stiffness and strength on the anti-collapse behavior of the composite frame is analyzed by means of the dynamic-col- umn-removal method.The results show that (1) the influence of the connection stiffness and strength on the com- posite effect between the floors in a side span is greater than that on the catenary action in inner spans; (2) the development of the axial force in the beams depends on the connection stiffness,rather than the connection strength; (3) the change of the connection behavior has no influence on the load-carrying independence of each floor; and (4) the improvement in the connection behavior can reduce the demand for the boundary restraint con- dition during the redistribution of internal force.

Durability of High Strength Concrete Strengthened with Prestressed CFRP Under Wet-Dry Cycles

HONG Lei JIANG Hai-xin

2017, 45(12):  143-148.  doi:10.3969/j.issn.1000-565X.2017.12.021

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The effects of the wet-dry cycles on the interface durability of the high strength concrete strengthened with prestressed CFRP (Carbon Fiber-Reinforced Polymer) were investigated by a four-point bending test.Three prestress levels,namely,0%,15% and 30% of the standard value tensile strength of the CFRP sheet,were im- posed in the test.Then,the interface degradation law was demonstrated by analyzing the influence of the wet-dry cycles and the prestress levels on the carrying capacity and the debonding failure model of specimens.The results reveal that the carrying capacity of the specimens decreases after 120 cycles,and higher prestress level causes the carrying capacity load to decrease faster,and that，with the increase of the wet-dry cycles,the failure model of the specimens transforms from the peeling of the protective layer of the concrete to the debonding of the resin layer.