Journal of South China University of Technology(Natural Science Edition)

Static Index Pruning Based on Document Importance

Li Xiao-ming Shan Dong-dong

2011, 39(4): 1-6. doi:10.3969/j.issn.1000-565X.2011.04.001

Asbtract ( 290 )

PDF (316KB) ( 681 )

Related Articles | Metrics

As the quality and importance of Web pages are both variable,paper proposes a static index pruning method which uses the web page importance to determine the ratio of information kept for each document. The result of experiments on GOV2 dataset show that ( 1) the proposed method greatly reduces the storage size and speeds up the search; ( 2) when the pruned index takes only 13% of the original size,P@ 10 and P@ 20 reach or exceed the baseline using full index; and ( 3) by using the proposed method,P@ 10,P@ 20 and MAP are all better than those of the traditional method at the same pruning level.

Performance Analysis of Distributed File System for Search Engine

Dong Shou-bin Zhao Tie-zhu

2011, 39(4): 7-14. doi:10.3969/j.issn.1000-565X.2011.04.002

Asbtract ( 376 )

PDF (380KB) ( 1540 )

Related Articles | Metrics

As a search engine is a kind of data-intensive application,its performance is greatly affected by the underlying distributed file system. This paper deals with the performance evaluation and optimization of the distributed file system oriented to search engine application. In the investigation,first,the factors affecting the performance of distributed file system and the relevant research progress are summarized. Then,an open architecture based on Hadoop is designed to systematically evaluate the performance of HDFS and Lustre in search engine scenarios. Finally,several improved schemes are proposed to overcome the shortcomings of HDFS in terms of write performance and small file disposition clarified by the results of performance assessment,which provides a reference for the optimization of distributed file system.

Unknown Malware Detection Based on IRP

Zhang Fu-yong Qi De-yu Hu Jing-Lin

2011, 39(4): 15-20. doi:10.3969/j.issn.1000-565X.2011.04.003

Asbtract ( 578 )

PDF (366KB) ( 2436 )

Related Articles | Metrics

As the malware detection method based on API can only detect the malware running in user mode and is noneffective for the malware running in kernel mode and calling kernel APIs,a novel detection method of unknown malware is proposed based on IRP（I/O Request Packet）.Then,the Nave Bayes,the Bayesian networks,the support vector machine,the C4.5 decision tree,the Boosting,the negative selection algorithm and an improved artificial immune system are used to classify IRP sequences for malware detection,and the detection rates of all the above-mentioned methods with different feature selection algorithms are compared.The results demonstrate that（1） the proposed method is effective in malware detection;（2） the Boosting decision tree with Fisher score feature selection algorithm outperforms other detection methods,with the highest detection rate of 98.3%;（3） the improved artificial immune system,which detects malware by selected IRP subsequences only existing in malware＇s IRP sequences,performs well,with a detection rate of 95.0% and a false detection rate of 0.

Prediction of Search Data Volume Based on Time-Series Clustering and ARMA Models

Sun Cheng-jie Liu Feng Lin Lei Liu Bing-quan

2011, 39(4): 21-25. doi:10.3969/j.issn.1000-565X.2011.04.004

Asbtract ( 297 )

PDF (254KB) ( 1626 )

Related Articles | Metrics

In order to guide the adjustment of product development and business strategy by predicting and analyzing the search data volume,the data of search volume are organized into time series that is modeled and predicted using the autoregressive moving average ( ARMA) models. Then,the set of time series is modeled by clustering; the cluster centers are modeled using ARMA models; and the same-class series is fitted with the models approximately to obtain the predicted values. Moreover,after such operations as data preprocessing,similarity analysis,similarity-based clustering and time-series prediction,the search data volume is predicted and is compared with the actual one. Experimental results show that it is feasible and accurate to model similar time series with the same ARMA model. In addition,clustering results indicate that the search data volume of the products with the same brand tends to be clustered together,which provides a reference for the relationship mining of search terms.

Click Model Based on Browsing Time of User

He Jing Yuan Wen-qing Yan Hong-fei

2011, 39(4): 26-31,37. doi:10.3969/j.issn.1000-565X.2011.04.005

Asbtract ( 451 )

PDF (308KB) ( 904 )

Related Articles | Metrics

As the clicks of users are affected by many factors such as the browsing behaviors of users and the features of adjacent documents,they cannot be directly interpreted as document relevance during the analysis of users' click log. In order to obtain correct document relevance features,a click model based on browsing time is proposed. In this model,the document relevance is assumed to affect the browsing time for the document,which means a user may spend more browsing time if the document is more likely to be relevant. Therefore,the document relevance can be estimated according to the browsing time. Then,an exponential distribution is determined to describe users' browsing time,and some experiments are carried out to verify the effectiveness of the proposed model. The results indicate that the model is superior to the existing click models because it can estimate document relevance and future clicks more accurately.

Content Extraction Algorithm of HTML Pages Based on Optimized Weight

Wu Qi Chen Xing-shu Tan Jun

2011, 39(4): 32-37. doi:10.3969/j.issn.1000-565X.2011.04.006

Asbtract ( 302 )

PDF (269KB) ( 1896 )

Related Articles | Metrics

With the increase in advertisement amount in HTML pages,it becomes more and more difficult to extract content accurately. In order to solve this problem,an algorithm of content extraction from HTML pages is proposed based on optimized weight. In this algorithm,first,the features of the content are analyzed to obtain the statistical features of the attributes by analyzing the characteristics of the content block in web pages. Then,in view of different importance of the features,the weight and threshold of the features are optimized by using the particle swarm optimization algorithm,which further improves the performance of the algorithm. Finally,some experiments are performed to verify the effectiveness of the algorithm. The results show that,as compared with the algorithm with un-optimized weight,the proposed algorithm improves the recall rate of content extraction to 95.8% without reducing the precision.

Wireless Mesh Gateway Selecting and AP Clustering Algorithm Based on Clustering

Huang Shu-qiang Zhou Ji-peng

2011, 39(4): 38-43. doi:10.3969/j.issn.1000-565X.2011.04.007

Asbtract ( 542 )

PDF (523KB) ( 1887 )

Related Articles | Metrics

Aiming at the gateway deployment and AP clustering of wireless Mesh networks,a heuristic algorithm based on clustering is proposed.In this algorithm,first,a weight index of the minimum hops is designed to reflect the relationship between the gateway number and the minimum hops,with which a suitable initial solution is obtained by a heuristic algorithm.Then,the initial solution is adjusted and optimized via the k-means clustering to obtain a symmetrically network distribution.Finally,some simulations are carried out to verify the effectiveness of the proposed algorithm.The results show that,with the help of the algorithm,the three optimization objectives,namely,the minimum number of gateways,the minimum average number of hops from AP to gateway and the minimum load-balancing index,reach a good balance after the adjustment with finite times.

Dynamic Analysis and Bionic Design of Multi-Body System of Large-Scale Horizontal-Axis Wind Turbine

Liu Wang-yu Zhang Yong Chen Long

2011, 39(4): 44-49. doi:10.3969/j.issn.1000-565X.2011.04.008

Asbtract ( 530 )

PDF (353KB) ( 1177 )

Related Articles | Metrics

In this paper,a dynamic model of the multi-body system of a 1.5MW direct-drive wind turbine is established with the finite element software ANSYS.Then,the natural frequency of the wind turbine is calculated,and the resonance and the stability of the system are analyzed.Moreover,the transient response of each component of the system under extreme operation gusts is discussed.The results indicate that,the tower is flexible;the system is stable and safe at normal working rotational velocity;and that,due to the difference in stiffness of the components,the variation of the tip of the wind turbine blade,which is induced by the coupling of the elastic deformations of three blades and the tower under wind loading,is more complex than that of other components.The flexible structure of the plant trunk is applied to the design of the wind turbine tower,and the feasibility of this bionic design is finally proved.

Design of a Modular Robot Platform

Zhou Xue-feng Jiang Li Zhu Hai-fei Cai Chuan-wu Guan Yi-sheng Zhang Xian-min

2011, 39(4): 50-55,61. doi:10.3969/j.issn.1000-565X.2011.04.009

Asbtract ( 529 )

PDF (824KB) ( 3758 )

Related Articles | Metrics

In order to overcome such shortcoming as low flexibility,poor fault tolerance,poor self-repairing ability as shown in bask-based design of traditional robots,and to reduce the use cost of robots,a modular robot platform is designed.In the investigation,first,the overall design of the modular platform is presented.Then,the design principles and implementations of the hardware and the software of the platform are introduced.Finally,five robots,namely a manipulator,a wheeled mobile robot,a biped walking robot,a wall-climbing robot and a tree-climbing robot,are built for the proposed platform,for which some simulations and experiments are performed.Experimental results show that the proposed modular design method is feasible with high performance.

Experimental Methods of Equiaxial Tension of Hyperelastic Membrane and Corresponding Simulations

Luo Hua-an Wang Hua-ming You You-peng

2011, 39(4): 56-61. doi:10.3969/j.issn.1000-565X.2011.04.010

Asbtract ( 1702 )

PDF (635KB) ( 4912 )

Related Articles | Metrics

In this paper,first,an equi-biaxial tensile test apparatus for hyperelastic membrane was developed,and the principle and method of the equiaxial tension test were illustrated.Then,the test conditions and the data processing are both investigated.Finally,three kinds of equiaxial tension methods,i.e.,the ideal tension test,the free-corner tension test and the fixed-corner tension test,were simulated with FEA software ABAQUS.It is found that the error of the fixed-corner tension test in a large tension range is small enough to satisfy the requirements of experiments.

Vibration Control of Flexible Translating Manipulator with Pneumatic Driving

Xie Zhuo-wei Shi Ming-li Wang Bin Qiu Zhi-cheng

2011, 39(4): 62-65,104. doi:10.3969/j.issn.1000-565X.2011.04.011

Asbtract ( 537 )

PDF (403KB) ( 1537 )

Related Articles | Metrics

In order to effectively suppress the vibration of flexible translating manipulators,a rod cylinder-based pneumatic driving scheme is proposed,which suppress the vibration by controlling the motion of piston rod via the pulse code modulation（PCM） method.Then,the pneumatic circuit is constructed,and the system model of the flexible manipulator with pneumatic driving is established.Moreover,based on the closed-loop equation analysis of the control algorithm,the feasibility of simultaneous slide positioning and vibration suppression is analyzed.Finally,an experimental setup of the flexible translating manipulator with pneumatic driving is proposed and is used to perform an active vibration control experiment.The results demonstrate that the proposed scheme effectively suppresses the low-frequency mode vibration of flexible manipulators and implements the pneumatic positioning simultaneously.

A Denoising Method of Monitoring Information Under Strong Noise

Jiang Xian-hai Xie Cun-xi Zou Yan-biao

2011, 39(4): 66-69. doi:10.3969/j.issn.1000-565X.2011.04.012

Asbtract ( 529 )

PDF (605KB) ( 1565 )

Related Articles | Metrics

In order to improve the accuracy of information prediction for monitoring systems,a denoising method of monitoring information under strong noise is proposed.In this method,the characteristics of wavelet coefficients of both the monitoring information and the noise are analyzed based on the wavelet transform,and the Hampel filtering is adopted to process the wavelet transform coefficients.Then,an inverse wavelet transform is performed to denoise the processed signals.An experiment is finally carried out on PhysioNet database,which verifies the effectiveness of the proposed denoising method.

General Inverse Dynamic Analysis of Gough-Stewart Platform

Liu Guo-jun Zheng Shu-tao Han Jun-wei

2011, 39(4): 70-75. doi:10.3969/j.issn.1000-565X.2011.04.013

Asbtract ( 477 )

PDF (298KB) ( 1383 )

Related Articles | Metrics

In practical applications,users sometimes require the control point to be changeable,and the mass centers of piston parts and cylinder parts of the limbs are often non-collinear to the attachment points of universal joints.In order to solve these problems,a general inverse kinematic model,which is applied to the control point at any desired point and to the mass centers at random positions,is established.Then,a general inverse dynamic equation is built based on the principle of virtual work,and a compact solution to the equation is obtained.More-over,the proposed model is simplified according to practical situations,and the application scope of the model is clearly stated.Finally,some simulations are performed to verify the correctness of the established equation,with the results being completely consistent with the reported ones.Thus,it is concluded that the established inverse dynamic equation is correct and is applicable to the design and model-based control of the Gough-Stewart platform.

Fast Search Algorithm of Pen-Cutting Regions Based on Arc Approximation

Li Wan-jun Zhao Dong-biao Lu Yong-hua Liu Kai

2011, 39(4): 76-81. doi:10.3969/j.issn.1000-565X.2011.04.014

Asbtract ( 407 )

PDF (2539KB) ( 1042 )

Related Articles | Metrics

In order to reduce the calculation complexity and improve the processing efficiency of pen-cutting process,an arc approximating method is proposed to detect the pen-cutting regions in the NC machining of freeform surfaces.In this algorithm,an improved quadtree algorithm is presented to subdivide and approximate the freefrom surface.Then,arc approximation is performed to approximately calculate the curvature radius for the purpose of quickly judging the local interference,reducing the calculation complexity and improving the search efficiency.Finally,a binary-tree method is used to exactly detect the boundary points and to determine the boundary of pen-cutting regions.Case results indicate that the proposed algorithm is effective because it can fast and accurately search the local interference regions,with a time cost reducing from the traditional 85.047s of the point-by-point searching to 33.734s.

Relative Position and Friction Power Loss Between Slipper Retainer and Ball Guide in Axial Piston Pump

Sun Yi Jiang Ji-hai Liu Jun-long

2011, 39(4): 82-87. doi:10.3969/j.issn.1000-565X.2011.04.015

Asbtract ( 523 )

PDF (395KB) ( 2470 )

Related Articles | Metrics

In this paper,the relative position between the slipper retainer and the ball guide in axial piston pumps is analyzed,and the force loading on them is clarified by analyzing the return force of spring.Moreover,a mathematical expression of the friction power loss casued by the moving of the slipper retainer around the ball guide is derived.The results show that the spring force,the radius of ball guide,the rotational speed of the pump,the swashplate angle and the friction coefficient between the slipper retainer and the ball guide are all important parameters that affect the friction power loss.In addition,based on the friction experiments on different matched pair materials applied to the slipper retainer and the ball guide,the wearing condition between the slipper retainer and the ball guide is comprehensively analyzed and compared,which provides a reference for the material selection in actual working conditions.

Preparation and Properties of Resistant Starch from Mung Bean Starch

Gao Qun-yu Li Su-ling

2011, 39(4): 88-93. doi:10.3969/j.issn.1000-565X.2011.04.016

Asbtract ( 607 )

PDF (511KB) ( 4330 )

Related Articles | Metrics

Resistant starches（RS） with high RS content were prepared from mung bean starch respectively via the autoclaving treatments with and without the addition of pullulanase.Then,the effects of the starch slurry content,the enzyme dosage,the debranching time,the retrogradation temperature and the retrogradation time on the formation of RS were analyzed,and the granule morphology,crystalline structure and thermal characteristics of the starch were investigated by means of SEM,XRD and DSC,respectively.The results show that（1） after an autoclaving treatment at 121℃ for 20min,debranching with 50ASPU/g pullulanase at 55℃ for 24h and a storage at 20℃ for 24h,the RS content of the sample was 56.9%;（2） after the debranching and recrystallization,the recrystallized starch granules display irregular shaped fragments,the XRD pattern changes from Type A to Type B,and the degree of crystallization greatly increases from 17.9% to 45.7% in the presence of enzymatic treatment;and（3） the melting temperature,the enthalpy and the thermal stability of RS all increase after debranching and recrystallization.

Effect of Acid Pretreatment on Physicochemical Properties of Micronized Starch Prepared by Ball Milling

Huang Qiang Liu Sha Fu Xiong

2011, 39(4): 94-98. doi:10.3969/j.issn.1000-565X.2011.04.017

Asbtract ( 515 )

PDF (791KB) ( 2097 )

Related Articles | Metrics

As time cost and energy consumption of ball milling smash of native starch are both high and the product is easy to gelatinize,acid pretreatment before the milling was introduced in the preparation of micronized starch.The corresponding physicochemical properties of the product,including the particle size,the granule morphology and the crystalline structure,were then investigated.The results show that（1） ball milling greatly affects the granule morphology and the crystalline structure but it produces no effect on the particle size of native starch;（2） acid pretreatment makes the milling easy and results in a decrease in particle size of the micronized starch;（3） the content of small particles（in a size of less than 10μm） in the micronized starch with acid pretreatment（the hydrolysis rate being 8.80%） is 72.58%,which is greatly higher than the value 16.76% of the native starch;（4） with the implementing of ball milling,some micronized starches aggregate;and（5） after the acid pretreatment,the crystalline structure of the micronized starch is partially destroyed,part of the Maltese cross disappears,the birefringence intensity weakens,and the degree of crystallization decreases significantly.

Preparation and Properties of SPI-Dextran Conjugate in Liquid System

Qi Jun-ru Zhuo Xiu-ying Yang Xiao-quan

2011, 39(4): 99-104. doi:10.3969/j.issn.1000-565X.2011.04.018

Asbtract ( 545 )

PDF (330KB) ( 1304 )

Related Articles | Metrics

Soy protein isolate-dextran conjugate（SDC） was prepared via the Maillard reaction in a liquid system.Then,the covalent binding between dextran and the protein was confirmed using the SDS-polyacrylamide gel electrophoresis technology,and the molecular conformation and functional properties of the product with covalent binding were analyzed by means of circular dichroism spectrography,GPC and DSC.The results show that the product obtained after a 24h reaction in 95% ethanol system at 60℃ possesses better emulsifying activity than that dry-heated for 5d;and that significant structural changes occur in the secondary and the tertiary structures of the conjugate,with the tertiary structure being more compact.Moreover,an improvement of thermal stability of the product is revealed via thermal analysis.

Multi-Stage Automatic Ultrafiltration System Enhanced with Complex Physical Fields

Fu Xiao-qin Li Lin Li Bing Chen Ling

2011, 39(4): 105-109. doi:10.3969/j.issn.1000-565X.2011.04.019

Asbtract ( 476 )

PDF (539KB) ( 1190 )

Related Articles | Metrics

Proposed in this paper is an automatic ultrafiltration system enhanced with ultrasonic and pulse electric field,which is used to overcome the concentration polarization and membrane fouling during the ultrafiltration and improve the automation level of ultrafiltration process.The system consists of a crude filtration loop,two ultrafiltration loops,a cleaning loop and a heat-exchange loop,and possesses excellent operation flexibility because it can simultaneously perform multi-stage or separately perform single-stage ultrafiltration.It also possesses a multi-layer distributed automatic control subsystem based on Kunlun MGCS configuration,which adopts an industrial personal computer and a Simens S7-200 PLC as the system hardware.The application of the proposed system to the concentration of pumpkin polysaccharides shows that,in the adopted experimental conditions,the average permeation flux increases by 1.15~2.53 times and the rejection by 15 points of percentage,which means that the system greatly improves the ultrafiltration efficiency and effect.

Feasibility of Using Soy 11S Globulin as Neotype Immunogen Carrier

Chen Lei Li Lin He Xiao-wei Su Jian-yu Liu Xiao-yun

2011, 39(4): 110-114. doi:10.3969/j.issn.1000-565X.2011.04.020

Asbtract ( 280 )

PDF (253KB) ( 800 )

Related Articles | Metrics

This paper deals with the feasibility of substituting soy 11S globulin ( 11S) for bovine serum albumin ( BSA) as a neotype immunogen carrier in the enzyme-linked immunosorbent assay ( ELISA) . In this investigation,first,sulfadimethoxine ( SDM) respectively conjugated to soy 11S globulin,soy 7S globulin and BSA was used as immunogen,and the corresponding polyclonal antibodies against SDM-soy 11S globulin,SDM-soy 7S globulin and
SDM-BSA were obtained. Then,a competitive ELISA and an indirect competitive ELISA were conducted to detect the titers of the three antiserums and the specificity of the purified antibodies. Finally,representative standard curves of SDM inhibiting the three antibodies were presented. The results indicate that,as compared with SDMBSA,SDM-11S conjugate is of better immunogenicity and specificity,and that the cross reactivities of SDM-11S
antibody against other sulfonamides are all excellent,with a value being less than 0. 01%. All these results verify the feasibility of substituting soy 11S globulin for BSA as a neotype immunogen carrier in ELISA.

Experimental Investigation and Mathematical Modeling of Solar Drying Equipment

Li Bian-sheng Shen Xiao-xi Liu Wei-tao

2011, 39(4): 115-120. doi:10.3969/j.issn.1000-565X.2011.04.021

Asbtract ( 390 )

PDF (359KB) ( 1175 )

Related Articles | Metrics

The natural convective drying of Ganshimei（intermediate moisture salted plum） was performed using the self-designed small-size solar drying equipment,and the corresponding experimental parameters were detected.Then,the material and energy consumption of the drying system were calculated.Finally,a mathematical model describing the natural convective drying was put forward by changing the effective solar radiant energy per unit.The results show that the natural convective drying using the designed equipment,whose drying efficiency is 61.60%,is of a time cost of 14h,which is only 28.0% of that of the traditional sun drying;and that the proposed model accords well with the experimental results,with a relative deviation being less than 1%.This paper provides the theoretical basis for the application of solar drying equipment and for the quality prediction and drying condition control of Cantonese-style preserved fruits.

Comparison of Turbulence Models for Numerical Simulation of Outdoor Wind Environment Around Building

Li Qiong Akashi Mochida Meng Qing-lin Zhao Li-hua

2011, 39(4): 121-127. doi:10.3969/j.issn.1000-565X.2011.04.022

Asbtract ( 546 )

PDF (403KB) ( 1605 )

Related Articles | Metrics

Aiming at the wind-tunnel experimental models with and without gas dispersion provided by the Architectural Institute of Japan（AIJ）,15 turbulence models are employed to simulate the outdoor wind environment.Then,by the comparison between the simulated results and the wind-tunnel experimental ones,the optimal turbulence model for the numerical simulation of outdoor wind environment around a building is determined.The results show that Suga's cubic high-Re k-ε model is the best due to its high accuracy of simulating both the air flow and the pollutant diffusion,but the CPU time of it is longer than that of the standard k-ε model.Thus,during the CFD numerical simulation of the outdoor wind environment of a building,Suga's cubic high-Re k-ε model can be used when the time is enough,and the standard k-ε model can be used when high accuracy is not required and when the calculation time is limited.

Distribution Characteristics of Mean Wind Pressure on Tall Buildings

Xie Zhuang-ning Zhu Jian-bo

2011, 39(4): 128-134. doi:10.3969/j.issn.1000-565X.2011.04.023

Asbtract ( 585 )

PDF (522KB) ( 1976 )

Related Articles | Metrics

The variation of wind pressure on a super-tall building under the interference of nearby buildings was measured by a series of wind tunnel tests by means of the synchronous pressure measurement technique,and the interference effects of two tall buildings with different breadth ratio Br and height ratio Hr on the wind pressure were analyzed.The results show that (1) the interfering building usually causes obvious shielding effect on the principal building when it is placed in the windward area with an across-wind-direction spacing less than twice the breadth of the principal building,and,generally,wider and higher interfering building may cause more significant shielding effects;（2） due to the three-dimension flow effects,lower upstream interfering buildings（Hr1） in tandem arrangement may increase the local mean wind pressure on the windward and the lateral face by 25% and 56%,respectively;（3） the channeling effect in side-by-side arrangement is the main reason for the wind pressure increase;（4） the maximum interference factor of the wind pressure on the lateral face is found to be 2.6 in side-by-side arrangement and decreases with the increase of building spacing;and（5） the channeling effect tends to disappear only when the building spacing exceeds eight times the breadth of the principal building.In addition,a credible regression equation with the accuracy of 99% for two side-by-side arranged buildings is proposed to predict the maximum interference factor of the mean wind pressure on the lateral face.

Attenuation Ability Influenced by Amount and Attenuation Coefficient of Perfectly-Matched Layers in Acoustic FDTD Method

Huang Kun-peng Zhao Yue-zhe

2011, 39(4): 135-139,162. doi:10.3969/j.issn.1000-565X.2011.04.024

Asbtract ( 522 )

PDF (404KB) ( 2267 )

Related Articles | Metrics

This paper deals with the acoustic absorbing ability affected by the amount and attenuation coefficient of perfectly-matched layers（PML） in acoustic finite-difference time-domain（FDTD） method,and establishes a PML boundary model for the absorbing ability analysis.The results indicate that（1） the layer amount and the attenuation coefficient relate to each other;（2） more PML layers may result in high absorbing ability but heavy computation burden;（3） when the layer amount is unchanged,appropriate attenuation coefficient should be set for each attenuation layer for the purpose of decreasing the numerical reflection due to the difference in attenuation coefficient;and（4） in practical applications,suitable layer amount and attenuation coefficient should be determined by comprehensively considering the calculation complexity and accuracy.

Analysis of Compressive Capacity of Brick Masonry Compressively Strengthened with Sprayed GFRP

Gu Qian Peng Bo Weng Rui

2011, 39(4): 140-148. doi:10.3969/j.issn.1000-565X.2011.04.025

Asbtract ( 543 )

PDF (623KB) ( 1724 )

Related Articles | Metrics

In this paper,firstly,standard compressive specimens of brick masonry were strengthened with sprayed chopped glass fibre-reinforced polymer（GFRP）.Then,the specimens were tested under both the concentrically and the eccentrically axial compressions,and the failure mode,the ultimate bearing capacity and the ultimate deformability of the strengthened specimens were explored.Finally,the strengthening effects affected by the spraying thickness,the chopped fibre length and the combination with glass fibre gridding sheet were investigated.The results indicate that（1） spraying GFRP significantly increases the ultimate bearing capacity and the deformability of brick masonry in compression,effectively postpones the emergence and propagation of initial cracks,and fairly improves the brittle behaviour of unreinforced masonry;（2） the ultimate compressive capacity and the ultimate compressive strain of the strengthened specimens under concentric compression averagely increase by 79.9% and 60.3%,respectively,while those of the specimens under eccentric compression averagely increase by 136.7% and 90.8%,respectively;and（3） the optimal spraying thickness and chooped fibre length for compressively-streng-thened brick masonry are 7mm and 25mm,respectively.In addition,the calculated values of ultimate bearing capacity obtained by the proposed simplified formula accord well with the test ones.

Effect of Shield Tunneling on Adjacent Single-Pile Foundation

Xu Ming Xie Yong-ning

2011, 39(4): 149-155. doi:10.3969/j.issn.1000-565X.2011.04.026

Asbtract ( 683 )

PDF (432KB) ( 2096 )

Related Articles | Metrics

It is important to consider the effect of shield tunneling on adjacent pile foundation during the construction of urban tunnels.This paper discusses the methods of three-dimension numerical simulation of shield tunneling,and then analyzes the effect of tunneling on the adjacent single-pile foundation and the corresponding affecting rules in terms of different relative position between the tunnel and the adjacent pile.The analytical results are finally compared with those from field monitoring and laboratory model testing.It is indicated that（1） both the end bearing force and the side friction of the pile highly relate to the tunnel position;（2） when the tunneling is just below the pile toe,the end bearing force continuously decreases and even disappears at a small ground loss,while the side friction gradually increases;（3） when the tunneling is at the side of the pile（about half tunnel diameter away from the pile）,the end bearing fore continuously increases,while the side friction decreases even to a negative value;（3） when the tunnel is at the mid-depth position of the pile side,large bending moment of the pile may occur;and（4） the impact of tunneling significantly decreases with the increase in horizontal distance between the tunnel and the pile.

Analysis of Key Parameters of Non-Tension Prestressing Technology for Continuous Steel-Concrete Composite Beams

Wu Li-li Nie Jian-guo

2011, 39(4): 156-162. doi:10.3969/j.issn.1000-565X.2011.04.027

Asbtract ( 457 )

PDF (318KB) ( 1483 )

Related Articles | Metrics

By analyzing the loading stages of the continuous steel-concrete composite beams with 2-5 spans,some key parameters of the non-tension prestressing technology of the composite beams,such as the counterweights and their arrangement,as well as the post-cast length of concrete in the negative-moment region,are investigated.Then,the calculation methods of crack width in the negative-moment region and mid-span deformation of the composite beams are discussed after the removal of the counterweights.It is suggested that the reverse deflection induced by the non-tension prestressing can be obtained through two steps,namely,converting the reverse loads resulting from weight removing to the full-span uniform ＂equivalent＂ ones,and then calculating the deflections under the ＂equivalent＂ loads.With this two-step method,the requirements of practical engineering are satisfied well,and the maximum relative error of deflection keeps within 15%.

Table of Content