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15 October 2012, Volume 34 Issue 5
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    Review
    2012, 34(5):  1-5.  doi:10.6052/1000-0879-12-034
    Abstract ( 1747 )   PDF (10279KB) ( 1291 )  

    Some problems concerning the design of natural draught cooling tower structures are reviewed, including theoretical and experimental investigations of statics, dynamics, buckling and wind-induced vibration of natural draught cooling towers.

    Applied Research
    PRESSURE DISTRIBUTION IN FLOODING OF LOW PERMEABILITY RESERVOIRS
    WU Daifeng, LU Xiaobing, LIU Qingjie, GAO Jian
    2012, 34(5):  27-31,51.  doi:10.6052/1000-0879-12-063
    Abstract ( 1214 )   PDF (2492KB) ( 1123 )  

    For low permeability reservoirs, the stress sensitivity cannot be neglected, and it makes the pressure system very complicated. In a low permeability reservoir, an effective system of the displacement pressure is a basis to guarantee the efficient development. Therefore, the research of the characteristics of the pressure distribution in a low permeability reservoir is important to the reservoir development. In this paper, the stress sensitivity of the low permeability core is taken into consideration, and the distribution of the pressure in the process of one-dimensional waterflooding is studied through experiments and numerical calculations, and the factors which affect the pressure distribution are also analyzed. The results show that, due to the effect of stress sensitivity, the pressure distribution sees obvious nonlinear characteristics, and there is an evident demarcation point at the displacing front; the degree of the stress sensitivity and the viscosity ratio have a great influence on the pressure distribution.

    2012, 34(5):  48-51.  doi:10.6052/1000-0879-12-028
    Abstract ( 1044 )   PDF (364KB) ( 905 )  

    Based on a bending stress analysis of a bend pipe of elliptical cross section of variable wall thickness, with Tresca and von Mises yield criteria, the plastic limit pressure formula is derived with consideration of variable elbow wall thickness and variable elliptic degree. The limit load changes with the pipe wall thickness and the ovality of the elbow.

    2012, 34(5):  32-35.  doi:10.6052/1000-0879-12-064
    Abstract ( 1262 )   PDF (849KB) ( 963 )  

    In order to quickly compute the dynamic response of a tracked vehicle stimulated by the road roughness, a simplified dynamic model of the tracked vehicle is created based on the theoretical mechanics principle and by neglecting some secondary factors. Meanwhile, a dynamic model of the tracked vehicle is built through ADAMS. The comparison between the results of the two models verifies the reasonableness of the simplified model. The results provide a foundation for the optimization design of the suspension system of a tracked vehicle and the inverse dynamics analysis based on the simplified dynamic model.

    BEARING CHARACTERISTICS OF THE BORED PILE IN CONSIDERATION OF PILE-SOIL COMBINED ACTIONS
    ZHANG Xiangdong, FAN Shixing, ZHANG Xuelei, LIU Jiashun
    2012, 34(5):  41-47.  doi:10.6052/1000-0879-12-065
    Abstract ( 1315 )   PDF (4860KB) ( 1252 )  

    This study concerns with the C14 building, which is in Beihai, Gaizhou for fisherman's residence. Static load tests on two test piles were carried out and the Q-S curves,the lateral friction resistance vs. depth curve, the soil interface relative displacement vs. depth curve and the axial force vs. depth curve were obtained. According to the field survey data and parameters empirically selected for the finite element a single pile model. The large finite element analysis software ADINA is used to analyze the single pile, and the main bearing characteristic curves are plotted by MATLAB according to the simulation data and the measured data. The rationality of the model and the parameters are first validated, and the relationship between the pile length and the main bearing characteristics of the single pile is studied. Finally the relationship of the pile group's main load-bearing characteristics and the pile length and the pile spacing are analyzed by using the pile group model built based on the model and the parameters of the single pile.

    THE EXPERIMENTAL SIMULATION OF MECHANICAL BEHAVIOR OF COILED TUBING IN WELLS
    GUAN Feng, DUAN Menglan, MA Weiguo, ZHOU Zhihong
    2012, 34(5):  21-26,56.  doi:10.6052/1000-0879-12-161
    Abstract ( 1251 )   PDF (2503KB) ( 1016 )  

    The coiled tubing systems are under complex underground loading. In this paper, the actual depth at which the coiled tubing goes into well is obtained and also the solution about the buckling, the lock-up and the un-lock-up of the coiled tubing. According to the relevant theoretical calculation results, the appropriate geometric parameters of the experimental system are determined. The test bench is designed, the simulation experiments about different specifications and different bending segment length of coiled tubing are carried on. The experimental phenomena about buckling, helical lock-up and top end yielding are analyzed, and the conditions of the helical lock-up are determined. The experimental results are in a good agreement with the theoretical results and may serve as a basis for the analysis of mechanical behavior of coiled tubing in wells.

    2012, 34(5):  36-40.  doi:10.6052/1000-0879-11-331
    Abstract ( 1056 )   PDF (2627KB) ( 1117 )  

    Laying the entire long distance transmission pipeline into the ditch is one of the difficult issue of construction. Through the simulation of curves of large deformation deflection beams, a mechanics calculation model is built, to analyze the stress and the deformation at different stages and states in the laying process, to find out the most unfavorable stress state, and to determine the key control parameters such as the distance of the lifting point and the height of the hoisting. The results can be used to guide the construction practice and be applied to the pulp pipe, and oil and gas pipeline projects.

    2012, 34(5):  52-56.  doi:10.6052/1000-0879-12-229
    Abstract ( 1242 )   PDF (3345KB) ( 1087 )  

    The bond-slip constitutive relationship is studied based on the push-out tests of nine steel reinforced lightweight concrete specimens. The section steel is instrumented with strain gauges in a machined axial cavity at the flanges and webs, and gauges are also stuck on the concrete surface corresponding to the gauge positions of the section steel. According to the test results, the negative exponent distribution function of the bond stress along the anchorage length is analyzed and the local relative slip curves are obtained. The constitutive relationship between the local bond stress and the slip at the loading end is investigated. The maximum local bond stress mainly depends on the strength of the concrete, the stirrup ratio and and concrete cover depth. The steel reinforced lightweight aggregate concrete beams are analyzed through introducing the local bond-slip constitutive relationship. The test values agree very well with those obtained with finite element analysis.

    Review
    2012, 34(5):  6-15.  doi:10.6052/1000-0879-12-095
    Abstract ( 1609 )   PDF (4008KB) ( 1204 )  

    The high-level pipeline steel is characterized by high toughness, with a wide range of plastic yielding zone around the crack tip, the existing test methods are difficult to meet the requirements for determination of its fracture toughness by using low constraint specimens. This paper reviews two kinds of fracture parameters based on CTOD and CTOA, which can characterize the deformation state of the crack tip. The present research status and the development trend of these test methods are summarized. A variety of factors influencing the testing accuracy of the fracture toughness for the pipeline steels are analyzed, and suggestions are made to improve the experimental design for measuring the fracture toughness of pipeline steels.

    Applied Research
    2012, 34(5):  16-20.  doi:10.6052/1000-0879-12-166
    Abstract ( 932 )   PDF (1621KB) ( 1107 )  

    Seepage through fractures in a geologic body is a very complex issue. Usually, its macro-seepage characteristics can be described by the equivalent permeability tensor. Based on the superposition algorithm for calculating the equivalent permeability tensor for multiple sets of infinity parallel fractures, this paper proposes a kind of more general superposition algorithm by introducing the concept of the through coefficient of fracture. Combining with the computer-generated technology of the random fracture network, the method can be used to approximately estimate the equivalent permeability tensor of two-dimensional random fractures.

    2012, 34(5):  57-60.  doi:10.6052/1000-0879-12-122
    Abstract ( 983 )   PDF (1139KB) ( 700 )  

    A method based on the mechanical transformation model is proposed to analyze the punching shear capacity of slab-column connections, which can transform the problem of elasticity into one of the structural analysis. The method can be realized by the computing platform OpenSees, and the key parameters of the model can be determined and validated through a comparison between the numerical simulation and experimental results. The results show that the proposed numerical method can simulate well the punching shear capacity of slab-column connections in terms of load-deformation curve, stiffness variation and distribution of deflection. A new approach can be used to study the mechanism, the mechanical characteristics and the distribution of internal forces, and provide a theoretical basis for design and practice.