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Table of Content

    25 March 2007, Volume 35 Issue 3
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    Mechanical Engineering
    Manufacturing of Inner Micro Grooves of Copper Heat Pipe via High -Speed Oil-Filled Spinning
    Li Yong Tang Yong Xiao Bo-wu Li Xi-bing Zeng Zhi-xin
    2007, 35(3):  1-5. 
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    Inner axial micro grooves of copper heat pipe were manufactured via the high-speed oil-filled spinning with drawing process , and the corresponding mechanism was then investigated. Experimental results show that the manufacturing of micro grooves includes two stages , namely , the extrusion and the forming stages , that the proce-ssing of micro grooves is mainly affected by various factors , such as the geometric parameters and working position of the multi-tooth mandrel , the depth reduction , the drawing speed , the spinning speed and the working tempera-ture, that micro grooves with different shapes , depths and depth/width ratios can be obtained by varγing the extru-sion depth , the feed rate , the mandrel shape and size , and that the high -speed oil-filled spinning is feasible to the manufacturing of micro grooves due to its full material utilization , high efficiency and low cost.

    Microstructure and Corrosion Resistance of Ceramic Coatings Formed on Aluminum Alloy by Micro-Arc Oxidation
    Du Jun Chen Dong-chu Li Wen-fang Zhang Yong-jun Peng Ji-hua
    2007, 35(3):  6-10. 
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    In this paper , a constant-current AC power supply with an asymmetric square-wave output mode was em-ployed to form Al2O3 ceramic coatings on aluminium alloy by micro-arc oxidation. The effects of processing parame-ters, such as the current density and the oxidizing time , on the microstructure and corrosion resistance of the pre-pared coatings were then investigated. The results show that the ceramic coatings are of excellent microstructure and property when the current density and the oxidizing time are respectively about 20 AI dmz and 15~20 min , and that a fairly short oxidizing time leads to uncoated areas on the specimen , while a fairly high current density results in many micro-cracks on the coatings , which all make the corrosion resistance of the coatings decrease. Moreover , it is found that the ceramic coatings are composed of both crystalline and amorphous Al2 O3 , and that there is no striking effect of the processing parameters on the phase composition in the asymmetric constant-current square-wave output mode.

    Warm Deep Drawability of Mg-RE Series ZE10 Magnesium Alloy Sheet
    Wang Jin-hong Xia Wei Zhou Zhao-yao Zhang Pei-wu Yun Jian-guo
    2007, 35(3):  11-15,21. 
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    Based on the deforming status and punching load-displacement curves of ZElO magnesium alloy sheet ,the forming properties of ZE10 sheet were experimentally investigated. The experiments were carried out in different temperatures , punching velocities , blank-holding methods , blank-holding forces and lubricate oil. In the experi-ments, the temperatures of the die and the punch were controlled via the thermocouples connected to heating com-ponents, and the fixed and gradually changed blank-holding forces were exerted by controlling the compression de-gree of spring. The results show that , when the lower die and punch are respectively heated to 250~300℃and (60±5) ℃, the punching velocity is (20±5)mm/min,the blank-holding force increases from 2 to 10 kN,the mixture of 80% gas pump oil and 20% graphite is used as the lubricant , and the floating blank-holding method is adopted , ZE10 magnesium alloy sheet exhibits preferable forming properties with a limit drawing ratio of 2. 8.

    Processing and Properties of AI-Cu-Mn Supporting Frame by Indirect Squeeze Casting
    Zhang Ming Zhao Hai-dong Zhang Wei-wen Luo Zong-qiang Li Yuan-yuan
    2007, 35(3):  16-21. 
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    In order to obtain large and light supporting frames by replacing spheroidal graphite iron with Al alloy , an indirect squeeze casting system of supporting frames was designed. The processing simulation and design were then carried out , and the dies of the frames were fabricated. Moreover , the supporting frame castings of AI-Cu-Mn alloy were trial-produced , and the defects in the trial production were analyzed. Finally , the mechanical properties and microstructures of the specimens from the castings with T5 heat treatment were discussed. The results show that , by shortening the cycle and reducing the moisture of lubricants , high-quality supporting frame castings without pores and inclusion can be fabricated , and that the castings are of good mechanical properties , dense microstructure and fine grains , whose average tensile strength , elongation and crystal size are 388 MPa , 8. 7 % and not more than o. 08 mm. All these above-mentioned results indicate the feasibility of the designed indirect squeeze casting system and the selected processing parameters.

    Process Analysis of Rapid Prototyping with Selective Laser MeIting
    Wu Wei-hui Yang Yong-qiang Lai Ke-xian
    2007, 35(3):  22-27. 
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    The process and mechanism of a rapid prototyping method , namely , selective laser melting , were ana-lyzed.The characteristics of this method were then summed up and a mathematical expression was deduced to describe the relationship between the temperature rise and the processing parameters. Moreover , the proposed ex-pression was used to optimize the rapid prototyping process. Experiments were finally conducted to verify the proto-typing process with Cu-P alloy as the material , by which the influences of the scanning speed and the laser power on the molding quality , the reasons for metal balling and the methods to avoid balling were discussed. The results indicate that , by reasonably adjusting the processing parameters , such as the scanning speed , the scanning space and the laser power , metal parts with high density can be directly fabricated.

    Ionic Bombardment of Austenitic Stainless Steel by Nitrogen and Chromium Ion Immersion
    Xiong Ling Hu Yong-jun Xu Jian Meng Ji-long
    2007, 35(3):  28-32. 
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    In this paper , chromium ion was introduced in the conventional ion-nitriding stove to ca盯y out the ionic bombardment of stainless steel by nitrogen and chromium ion immersion. An optical microscopy , an abrasion test device and an electrochemistry workstation were then adopted to investigate the microstructure , wear resistance and corrosion resistance of the samples in different processing conditions. The results show that the wear resistance of the stainless steel with ionic bombardment processing is 2 - 5 times that of the untreated sample , and that the bom-barded stainless steel is of a liule reduction in corrosion resistance , as compared with the original stainless steel.However , as compared with the traditional ion-nitriding stainless steel , the corrosion resistance is greatly improved.

    Cathode Design in Electrochemical Machining of Blade Based on Actual Electric Field Distribution in Machining Gap
    Li Zhi-yong
    2007, 35(3):  33-37. 
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    According to the basic principle of electrochemical machining , discussed in this paper are two kinds of cathode design methods , which were respectively based on the mathematical model of a simplified electric field and the mathematical model of actual electric field distribution in the machining gap. The effects of these two cathode design methöds on the distribution of electric field density in the gap were then compared and analyzed. Moreover ,a group of experiments was carried out to verify the design accuracy. The results demonstrate that the cathode de-sign method based on the actual electric field distribution in the gap accords better with the electrochemical machi-ning process and the corresponding cathode is more precise and reasonable.

    Modeling and Optimization of Special Multi -Medium Combinational Capacitance for Magnetic Fluid Sensor
    Cao Dong Liu Gui-xiong Qiu Dong-yong Cheng Tao-bo
    2007, 35(3):  38-41. 
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    This paper first analyzes the structural characteristics of magnetic fluid (MF) sensor and the common-ness of MF capacitance sensor in technology. Next , a formula of capacitance is deduced by dividing the combina-tional capacitance into several simple capacitances with series-parallel connection. Then , a sensor model describing the multi-medium semi-cylinder combinational capacitance is set up. Moreover , the capacitance sensitivity and the capacitance are considered as the multi-objective functions to perform a multi-objective optimization , in which the capacitance function is transferred into a linear function according to its characteristics , thus simplifying the multi-objective optimization so as to form a simple objective optimization. Finally , multiple parameters of the model are optimized via the coordinate altemation method with remarkable effect.

    Relationship Between Medial Axis Pattern of Plant Leaf and Mechanics Self-Adaptability (I) :Experimental Investigation and Numerical Simulation
    Liu Wang-yu Hou Wen-feng Ou Yuan-xian
    2007, 35(3):  42-46,52. 
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    The medial axis pattem is not only the original geometric characteristic of plant leaf but also the major structural element that enables the plant leaf to stand the self-weight and the environmental stress. In order to reveal the theory of mechanics reinforcement of the plant leaf by the topological form , some copper veins were fabricated according to the data from the coordinates of dicotyledon. The deformations of the vein loaded with different forces
    at different points were then experimentally investigated and numerically simulated. The results indicate that the de-formations of the vein follow the superposition principle , and that the simulated deformation and deformation ten-dency accord with the experimental ones , thus verifying the correctness of the test method adopted in this paper.

    3D Graphic Simulation Modeling of Shop Floor in Assembly -Type Manufacturing
    Jiang Li-jun Li Zhe-lin
    2007, 35(3):  47-52. 
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    The traditional technology of simulation modeling does not satisfy the requirements of simulation for com-plicated manufacturing' process due to the long product line and the complicated control process. In order to solve this problem , a 3D graphic simulation modeling mechanism oriented to manufacturing process is presented after the investigation into the structural characteristics and running mode of assembly-type manufacturing , followed by the corresponding implementation method. In the investigation , the object-oriented design method and the virtual simu-lation technology are fully adopted. As a result , a visual 3D graphic simulation platform is developed from the view-point of application level. The proposed system can realize the computer simulation of the shop layout in manufac-turing process and can help the designer to choose the best design scheme of the shop floor.

    Numerical Analysis of Cold-Welding Characteristics of Friction Pairs in Space Mechanism
    Zhang Yong Chen Hui-ping
    2007, 35(3):  53-55,60. 
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    In this paper , the newly developed variation and nonlinear optimization methods are employed to solve the energy functions , the cold welding history under the asperities contacting was analyzed , with the aim of inv f'sti-gating the cold-welding characteristics of 仕iction pairs in space mechanism. The calculated results are fully dis-cussed.It is indicated that the cold welding characteristics of friction pairs greatly affect the working state of space
    mechanism , and that the maximum stress of the mechanism base increases obviously with the relative resting time of friction pairs.

    Vibration Analysis of Explosive Disposal Robot on Uneven Terrain
    Mo Hai-jun Xie Cun-xi Hu Qing-chun
    2007, 35(3):  56-60. 
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    In this paper , a tracked explosive disposal robot developed by South China University of Technology was used as the object to investigate the impact and vibration of the explosive caused by the moving of the robot on un-even terrain. A dynamic model of the robot manipulator was then established. The dynamic characteristics and the stability of the explosive under the excitation of uneven terrain were finally analyzed by Matlab simulation. The re-sults indicate that the moving speed of the robot greatly affects the stability of the grasped explosive and should be kept at O. 8m/s to ensure the safety when the robot moves on uneven terrain.

    Power & Electrical Engineering
    Method to Analyze Effect of Circuit Tolerance on Reliability of Protective Relays
    Wang Gang Shao Qi-zhuan Li Xiao-hua
    2007, 35(3):  61-65,76. 
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    In order to analyze the effect of circuit tolerance on the reliability of protective relays , the correct re-sponse rate is presented as the reliability index , and the corresponding confidence interval is estimated. Moreover ,a reliability criterion is proposed , that is , the system fails when the practical magnitude of system output signal ex-ceeds the tolerance range of the nominal magnitude. By combining the circuit simulation function of OrCAD/PSpice
    software and Monte Carlo simulation method , the reliability index and its confidence interval can be obtained via point and interval estimations. As an example , the sensitivity of the component parameters in the data acquisition system of digital protector is analyzed , the results verifying the proposed method.

    CFD-Based Investigation into Jet Interference in Multi-Nozzle Pelton Turbines
    Xio Ye-xiang Zheng Ai-ling Han Feng-qin Ding Er-xi Kubota Takashi
    2007, 35(3):  66-70. 
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    In order to increase the specific speed and force of Pelton turhines , the multi-nozzle confìguration is commonly adopted. However , the addition of nozzles leads to the jet interference , which reduces the efficiency of Pelton turhines. In this paper , the reasons for jet interference are analyzed. By calculating the numhers of four kinds of threshold frames , that is , the frame when the hucket meets the next jet , the frame for the last capture of
    outermost streamline of jet hy a hucket , the frame for the occurrence of ineffective jet hy non-capture and the frame at the cross point of two jets , two criteria are presented to predict the occurrence of interference for two adjacent hare jets. The criteria are then used to predict the hare-jet interference in the Pelton turhines with different nozzles and huckets , whose effectiveness is finally verified hy the predicted results.

    Lump-Sum Analysis of Internal Flow in Francis Turbine and Resulted Cavitation Prediction
    Fan Chun-xue Han Feng-qin Kubota Takashi
    2007, 35(3):  71-76. 
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    The methöd of Computational Fluid Dynamics (CFD) is adopted to carry out a lump-sum analysis of Francis turbine. Irr the analysis , the turbine is divided into several regions including the spiral casing , the stay vane , the guide vane , the runner and the draft tube. According to the variation of the residual error for each re-gion, the sufficient convergence of the residual error for the runner is used as the criterion for the iterative computa-tion.
    Then , with the Francis turbine in a hydropower plant as the object , the dimensionless pressure of the turbine is obtained , which is then employed to predict the time and position of cavitation on the suction surface of the run-ner vane. The predicted results accord well with the practical ones , thus verifying the effectiveness of the proposed method.

    Architecture & Civil Engineering
    Seismic Behavior of Steel Reinforced Concrete J oints with Plastic Hinge Shifting Away from Beam End
    Li Zhong-xian Zhang Xue-song Ding Yang
    2007, 35(3):  77-82. 
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    The seismic hehaviors of steel reinforced concrete joints with plastic hinge shifting away from the heam end were investigated hased on the experimental results of 2 full-scale joint specimens under cyclic loading. In the investigation , the joints designed as strong connections were treated with dog-hone style weakening on the upper and helow flanges of the H-type steel at the heam end near the joint core , and the longitudinal reinforcement ratio ,which distrihutes from the root of heam end to the maximum weakened flange of the H -type steel , was properly in-creased.Experimental results show that the ductility factors of the 2 joint specimens are all more than 5. 27 , which meets the requirements of the ductile frame in seismic design , and that the equivalent viscous damping coefficients on the maximum load are all more than O. 30 , which reveals quite high energy dissipation of the joints. Moreover , it is indicated from analyses that the constitution of plastic hinges for steel reinforced concrete joints can not only de-crease the shear in the joint core and the stress of seam in the beam-column connection hut also improve the rotation and shear capacities of plastic hinges in the heams , thus increasing the ductility and energy dissipation of the joints.

    Simulated Earthquake Investigation of Complex High-Rise Building by Shaking-Table Test
    Ji Jing Zhao Shu-ning Han Xiao-lei Zheng Yi
    2007, 35(3):  83-98. 
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    The partial frame-supported shear wall with transfer storey is applied to a 49-storey apartment building.As the difference in angle between the main axis of the upper storeys and that of the podium is 45°, a girder trans-fer structure is adopted , which results in the exceeding of several structural indexes from the limitation of current design codes. In order to investigate the aseismic performance of this complex high-risebuilding , a model with a
    scale of 1: 20 is fabricated and tested on the large-scale shaking-table with 3 dimensions and 6 degrees of freedom in the Chinese Academy of Building Research. Based on the test , the self-shaking properties , damping ratios , seismic responses , damage features and mechanism of the model prototype are researched , and the seismic response of the prototype structure is analyzed , indicating that the structure exhibits satisfactory aseismic performance under the ac-tion of the 7 - and 8-occurred earthquakes. Moreover , the feeble parts in the structure are presented. Several suggestions are finally offered to improve the aseismic performance of the building.

    Models for Evaluating Seismic Liquefaction Probability of Soils
    Pan Jian Liu Li-yan
    2007, 35(3):  90-93,99. 
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    The binaIγregression method was used to derive two logarithmic models based on 278 cases of liquefac-tion or nonliquefaction occurrences. In the two proposed models , the liquefaction probability was regarded as a function of earthquake load and soil resistance parameters , and the liquefaction resistance was measured through the tested values of the corrected standard penetration. Comparisons between these two logarithmic models and deter-ministic criteria were then performed. Moreover , the two models were applied to the analysis of typical sites. It is found that the two logarithmic models can objectively evaluate the information contained in the data and can be ap-plied to the direct quantification of conditional liquefaction probability based on the data.

    Electronics, Communication & Automation Technology
    Approximate Calculation of Seismic Displacement Response for RC Frame Structure
    Zhou Jing Cai Jian Fang Xiao-dan
    2007, 35(3):  94-99. 
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    The distribution mode of lateral displacement of reinforced concrete (RC) frame structure is first deduced by taking the structure as the combination of an ideal shear-type structure and an ideal flexural-type struc-ture and by adopting a general equivalent static load distribution mode. Next , the effects of shear to flexural ratio and loading distribution mode on the displacement response are discussed. Then , by predicting the first mode shape , a method to calculate the seismic elastic displacement response of the structure is proposed according to the displacement response spectrum. Moreover, the variations of displacement response and inter-storey drift ratio with the height are analyzed , and the maximal seismic inelastic displacement is also evaluated by the inelastic inter-storey displacement amplification factor. A numerical example is finally presented to verify the effectiveness of the proposed simplified method.

    Architecture & Civil Engineering
    Load-Carrying Capacity and Stiffness of Beam-Column Joint Strengthened with Stiffening Ring on Irregularly -Arranged Beam
    He Jun Cai Jian Wu Jian-ying Chen Qing-jun
    2007, 35(3):  100-105. 
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    For a steel structure , it is difficult to design reasonable joint on the irregularly-arranged beam. In order to solve this problem , a typical kind of full-scale beam-column joint strengthened with stiffening ring on the irregu-larly-arranged beam is modeled and tested , and the structural behavior and collapse mechanism of the joint are also investigated. Based on the experimental results , a finite-element analyzing model is established according to the elastic-perfectly plastic model , the Von Mises yield criterion and the geometric nonlinearity. The proposed nonli-near finite element model is then employed to carry out numerical parametric analyses for the joint. By summarizing the experimental and numerical results , two formulae are finally presented to calculate the load-carrying capacity and stiffness of the joint strengthened with stiffening ring on the irregularly-arranged beam.

    Flexural Resistance of Semi -Rigid Connection of Steel Beam-to-Column Minor Axis with Top-and-Seat Angles
    Li Wen-ling Hao li-ping Wang Lian-kun Chen Hong-ying Zhang lun-feng Shi ling
    2007, 35(3):  106-110. 
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    In order to investigate the f1exural resistance of semi -rigid connections , a formula was deduced based on the simplified slope-displacement equation to calculate the initial stiffness of the semi-rigid connection with top-and-seat angles. The ultimate moment of the connection was then obtained according to the plastic characteristics of the angle. Moreover , the f1exural behaviors of two types of semi-rigid connections of column minor axis with top-and-seat angles were experimentally discussed. The moment-rotation characteristics of the above-mentioned connections were finally simulated by using the three-parameter power model. The results show that the simulated results accord well with the experimental ones , and that the new connection fo口丑designed in this research possesses good moment capaclty.

    Approximate Calculation of Impedance of Pile Group-Slab System
    Lei Wen-jun Wei De-min
    2007, 35(3):  111-116,131. 
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    In this paper , numerical procedures are first adopted to analyze the impedance of pile group-slab sys-tem.Based on the calculated impedance of two pile group-slab systems with different configurations , it is found that the dynamic interaction in the pile group-soil-slab system has low frequency dependence during the low-frequency vibration that is most concemed in the aseismatic design , so that , in the calculation of impedance of the pile group-soil-slab system , the dynamic interaction can be replaced by the static interaction. Based on the above-mentioned results , the static interaction in the pile group-slab system is then obtained via illustrations , and some simplified forrnulae for calculating the lateral , rocking and cross-lateral-rocking impedances of the system are presented.

    Vibration-Based Damage Detection of Bridges Considering Inf1uence of Changing Environment
    Hu Li-ping Han Da-pan
    2007, 35(3):  117-121. 
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    In the vibration-based damage detection of bridges , it is difficult to avoid the uncertainty of the dynamic behaviour caused by changing environmental conditions. In order to overcome this difficulty , a novel damage detec-tion methodology for bridges is proposed based on the nonlinear principal component analysis. In this methodology ,first , an auto-associative neural network is constructed to caπY out a nonlinear principal component analysis for the element stiffness samples identified from healthy structure in various environmental conditions , and a nonlinear transformation mode that reveals the environmental influences is created. Then , the element stiffness samples ob-tained from an unknown state in various environmental conditions are inputted into the constructed network. Thus ,damages can be detected and located via the statistical analysis of the residual errors between the network outputs and the targets. The proposed methodology is finally verified by the numerical simulation of a simply-supported bridge.

    Analysis of Parameter Sensitivity and Reliability for the Xijiang Bridge Under Construction
    Fan Xue-ming Su Cheng Wang Tao
    2007, 35(3):  122-126. 
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    A stochastic singular-points-outside-domain (SPOD) method for analyzing beam structures is presented based on the fundamental solutions of certainty problems , the conventional SPOD technique and the multi-domain coupling technique. The proposed method is then applied to the stochastic static analysis of the Xijiang bridge under construction , and the sensitivity of the influences of different material and loading parameters on the deflection of the girder is investigated. Considering the variations of relevant parameters , a reliability analysis is further conduc-ted for the elevation control of the girder of the Xijiang bridge , with the failure probabilities for different construc-tion stages and tolerant errors being also discussed. The results of an application to the Xijiang Bridge show that the proposed stochastic SPOD method is effective and practical in the construction control of continuous rigid-connected bridges.

    Section Deformation of Flat Hollow Steel Box Girder of Cable-Stayed Bridge During Cantilever Erection
    Xu Jin-yong Yan Quan-sheng wang Wei-feng Han Da-jian
    2007, 35(3):  127-131. 
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    The Zhanjiang Bay bridge with a main span of 480 m is a two-pylon cable-stayed .bridge with spatial double-cable planes and hybrid girders. The steel girder of the bridge is flat hollow streamline steel box girder with truss-form diaphragms and intemal webs. As the loads on the segment being lifted differ from those on the segment supporting the crane , the two segment splices are of various section deformations during the cantilever erection. In order to reveal the relative deformation of box girder sections during the cantilever erection , the 3D finite element models of the segment being lifted and supporting the crane are established via the mixed element method. The in-fluences of several parameters including the truss stiffness on the deformation are then analyzed. The results indicate that the flat hollow steel box girder with truss-form diaphragms and intemal webs is feasible to long-span cable-stayed bridges , and that the relative deformation of the box girder is govemed by the transverse location of crane-acting
    point and the global stiffness of the steel box girder.

    Analysis of Pressure Drop of Fluid in Prefabricated Vertical Drains in Vacuum Preloading Ground
    Qiu Qing-chang Mo Hai-hong Dong Zhi-liang
    2007, 35(3):  132-136. 
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    The pressure drop of fluid in the prefabricated vertical drains (PVD) in vacuum preloading ground was analyzed based on the pressure-drop theories of ascending one-phase flow and two-phase flow. An experimental in-vestigation into the vacuum pressure of fluid in the PVD was then conducted. The results show that the fluid pres-sure in vacuum preloading ground gradually decreases along the flow direction , that only the fluid above the null groundwater pressure surface during the vacuum preloading is of a vacuum pressure because it is the only pore pres-sure reduction instead of the vacuum pressure of fluid under the null surface , that the vacuum pressure of fluid and the pore pressure reduction are two different conceptions , that the total pressure drop of the fluid in the vertical drains in vacuum preloading ground mainly includes two parts , namely the pressure drop due to the friction resis-tance and that due to the gravity , the latter being the inherent pressure drop of fluid in vertical direction , and that the falling depth of the null groundwater pressure surface directly embodies the intensity of vacuum preloading.

    Uncertainty Analyses of Watershed Hydrological Model Based on GLUE Method
    Huang Guo-ru Xie He-hai
    2007, 35(3):  137-142,149. 
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    The GLUE method is applied to the uncertainty analyses of TOPMODEL hydrological model , with the Xingfeng catchment , a tributary of Dongjiang watershed , as the research object. The results show that the parame-ters m , T0 and RV are sensitive , any a slight change of them will inf1uence the simulated results , while SR0 is not sensitive. Moreover , the observed flow hydrographs of two selected floods cannot be completely comprised in the
    upper and lower limits of the simulated hydrographs. Some flow values lie out of the 90% confidence interval , indica-ting that TOPMODEL model cannot simulate the whole flow process at the Xingfeng catchment due to the uncertainty of TOPMODEL model.

    Numerical Analysis of Singular Heat Flux Field (Ⅱ)Computation of Heat Flux Intensity Factors
    2007, 35(3):  143-149. 
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    In this paper , singular heat flux elements are developed from a hybrid finite-element variational function for static heat conduction problems. With the developed element , the heat flux intensity factor can be effectively and correctly predicted. The assumed heat flux field in the formulation of singular heat flux elements are based on the eigenpairs computed via the one-dimension finite-element procedure presented before. A series of numerical ex-amples indicates that the proposed singular heat flux elements help to find solutions with a high accuracy through coarse meshes , and that the proposed method is effective and reliable.

    Singular Point-Substructure Method for Analyzing Urban Seepage Field
    Luo Guan-yong Cao Hong Fang Ying-guang
    2007, 35(3):  150-154. 
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    In order to overcome the difficulty in the finite-element analysis of urban seepage field , a newly-devised singular point-substructure method is put forward to simplify the modeling of underground structures in the urban seepage field. In this method , first , the seepage field is meshed with sparse elements. Next , the elements sharing a singular point of an underground structure are extracted out as substructures. The extracted substructures are then refined layer by layer with similar elements. The equivalent stiffness matrixes and nodal vectors of the substructures are finally calculated via the static concentration from the inside to the outside layer by layer. Analytical results show that the proposed method can avoid the meshing of small-size structures in a large-scale region , and that it is of the same efficiency and accuracy as the infinite similar element method. Moreover , the proposed method is more convenient for the treatment of infiltration , phreatic water , multiple permeable layers and suspended underground structure.

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