Liu J.,Ryerson University |
Liu M.,Henan Electrical Power Survey And Design Institute |
Zhu Z.,Hohai University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2012
This paper presents an experimental investigation on soil deformation around uplift plate anchors in sand by using digital image correlation (DIC). The experimental setup consists of a camera, loading frame, plexiglass mold, and computer, which is developed to capture soil deformation during anchor uplifting. A series of model tests are performed to investigate the influence of particle size, soil density, and anchor embedment depth on soil deformation. A set of images captured during anchor uplifting are used to calculate soil displacement fields by DIC. The failure surface is studied by tracking the points with maximum shear strain values. On the basis of this study, it is found that soil deformation and the pullout resistance of plate anchors are substantially influenced by soil density and anchor embedment depth, whereas particle size within the studied range has limited influence. In dense sand, the shape of the failure surface changes from a truncated cone above a shallow anchor to a combined shape of a curved cone and a truncated cone for a deep anchor. In contrast, in loose sand a cone-shaped failure surface is formed within the soil mass above a shallow anchor; however, no failure surface is observed for a deep anchor, where the compressibility of soil is the dominating factor that influences the behavior of deep plate anchors in loose sand. © 2012 American Society of Civil Engineers.
Chen L.,Henan Electrical Power Survey And Design Institute
Applied Mechanics and Materials | Year: 2013
The failure of elastic perfect cylinders under uniform external pressure is caused by circumferential buckling. The effects of the cylinder length, of the restraining conditions at boundaries and of the length of the pressurized zone all have great influences on the critical buckling load. In the European Standard for Shells EN 1993-1-6 (2007), the critical circumferential buckling stress is obtained by introducing an external buckling factor which takes the influence of different boundary conditions into account. However, the restraint of the meridional rotation at boundaries was not considered separately for the factor. For short cylinders, any restraint of the boundaries affects the buckling mode and buckling strength greatly. In this paper, the effect of meridional end rotations on the buckling strength of short cylinders was studied. The pre-buckling membrane stress state given by membrane theory was assumed for all the analyses. © (2013) Trans Tech Publications, Switzerland.
Bai H.-K.,Henan Electric Power Company |
Li G.-S.,Henan Electrical Power Survey And Design Institute
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2011
The 220 kV electrical network short-circuit current level enhances quickly along with unceasing enhancement of electrical network structure, open-loop operation mode must be carried out gradually to lower the 220 kV electrical network short-circuit current level. But in the process of electrical network open-loop it often contradicts with some planned electrical network projects. This paper describes the fundamental principles as well as the main method of open-loop. Taking Zhengzhou 500 kV/220 kV electromagnetic ring for example, in accordance with its present situation and long-term network planning, open-loop operation is progressively implemented and the rationality of Zhengzhou long-term network plan has been simultaneously verified. This paper puts forward the idea of using the open-loop planning studies to verify the rationality of electrical network planning, which not only unifies the network planning and open-loop planning rationally to guide the development of electrical network, but also avoids unnecessary construction to save investment.
Qi Z.,North China Electrical Power University |
Dong D.,Henan Electrical Power Survey And Design Institute |
Yang Y.,North China Electrical Power University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010
Zero-sequence voltage will keep increasing when potential transformer ferroresonance occurs in an isolated neutral point system. Similar phenomenon happens during a single-phase-to-earth fault. An traditional line selection device starts when zero-sequence voltage and current exceed setting values, which is not effective for identification of ferroresonance and is apt to cause mis-operations. In the study, characteristics of fundamental frequency ferroresonance is emphatically analyzed and three-phase voltages and zero-sequence voltage in case of both ferroresonance and single-phase-to-earth fault are compared in detail. On this basis, ferroresonance identification technique is proposed based on comprehensive comparison of zero-sequence voltage and three-phase voltage. Verification by field data reveals that the technique can effectively increase the reliability of line selection devices and therefore satisfy the requirements for practical implementation. ©2010 State Grid Electric Power Research Institute Press.
Chen L.,Henan Electrical Power Survey And Design Institute
Applied Mechanics and Materials | Year: 2014
The cylindrical shells under global bending with different geometric parameters display different failure behavior. The size of typical buckles under axial compressive stress regimes is rather small and extends over a very small zone, with the axial compressive stress reaching the critical value. The first estimate of the elastic buckling strength in bending is the condition in which the most compressed fiber reaches the buckling stress for uniform axial compression. For short cylinders, local bifurcation buckling occurs at the middle of the most compressed side of the shell, and geometric nonlinearity has a little effect on the buckling strength, while for medium-length and long cylinders, the geometric nonlinearity and the ovalization of the cross-section should be considered. This paper explores the failure behavior in elastic cylinders in pure bending. © (2014) Trans Tech Publications, Switzerland.