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Analysis of the shear force effect in the method of pneumatic hinge.

机译：气动铰链方法中的剪力效应分析。

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摘要

The effect of transverse shear loading on the wrinkling and collapse loads of an air-supported cylindrical membrane is studied in this thesis. A transverse shear load causes shear stresses in the membrane and can be an important factor in the buckling process of a membrane structure.;At present the inflated cylindrical membranes are often used in the construction of large temporary shelters due to its light weight and simple erection. These structures are built by assembling elongated cylindrical pneumatic columns and creating in this way a closed space. A simplified approach to the analysis of wrinkling and collapse loads of a cylindrical air-supported membranes, subjected to axial loads and bending moments, was developed by Lukasiewicz and Balas in 1980s using the idea of "pneumatic hinges" (later called PHM method). In this approach the long cylindrical, inflated membrane is analysed utilising a beam model where the bending moment, normal force and the shear force are the factors deciding about the strength and buckling safety of the beam. It was found that the normal force and the bending moment in the cross-section of a pneumatic beam are the most important loadings deciding on the first wrinkling, creation of the pneumatic hinge (local large deformed area) and collapse of the membrane. The effect of shear stresses was neglected in that first approach.;PHM provides a simple and convenient tool for the industry for the design of structures built of air-supported membranes. A finite element software was developed using above mentioned ideas to check the buckling safety of this kind of industrial structures.;However, it is still necessary to determine the accuracy of PHM and the limits of its application due to that simplification. At present it can be done easily by comparing the results from PHM with the results of the advanced theory of membranes incorporating the possibility of wrinkling. Stanuszek (2003) developed a numerical method based on finite element technique to model the behaviour of wrinkled membranes. In that approach the cable analogy was introduced to define the wrinkling criteria in a triangular membrane element. The software developed by Stanuszek has been used to obtain the results from the finite element advanced method for comparison with the ones from experiment and PHM.;Several cases of membranes, with different loadings and boundary conditions are investigated in this thesis to verify the PHM. The main purpose focuses on studying the cases of cylindrical air inflated membranes loaded by transverse shear loadings. An experimental test has been performed with the membrane under the transverse shear load and distributed line load simulating the effect of the wind or the own weight. The experimental results were compared with the results of the calculations using the finite element analysis and PHM.;The comparisons indicate that PHM predicts the loads causing the first wrinkling and collapse loads with higher accuracy for the membranes loaded mainly by axial forces and bending moments. In the case of transverse shear loading, PHM predicts higher values of critical loads than the more precise finite element calculations. Also, it has been observed that the effect of the boundary conditions can reduce the value of the loads causing first wrinkling of the membrane structure. The main conclusion is that PHM can be used as a design tool for predicting the wrinkling and buckling of the membrane utilising a safety factor in the range of 2. It should be understand that PHM provides the upper limit loads for the ideal membrane causing first wrinkling. It gives more precise results while predicting the collapse loads. This is due to the fact that the first winkling phenomenon is strongly affected by the geometrical imperfections, boundary conditions and local deformations. Collapse loads correspond to the large deformations developed in the hinge area.;The PHM can be easily improved by adding the effect of the shear force in the formula for predicting the first wrinkling. The introduction of a safety factor is also recommended when the shear force causes local deformation and the first wrinkling critical forces are most affected.
机译：本文研究了横向剪切载荷对气浮圆柱膜起皱和塌陷载荷的影响。横向剪切载荷会在膜片中产生剪切应力，并且可能是膜片结构屈曲过程中的重要因素。；目前，充气圆柱膜由于其重量轻且安装简单而经常用于大型临时避难所的建设中。 。这些结构是通过组装细长的圆柱型气动柱并以这种方式创建一个封闭空间而构建的。 Lukasiewicz和Balas在1980年代使用“气动铰链”（后来称为PHM方法）的思想，开发了一种简化的方法来分析圆柱型空气支撑膜片的起皱和塌陷载荷，该载荷受到轴向载荷和弯矩。在这种方法中，利用梁模型分析了长圆柱状的充气膜，其中弯矩，法向力和剪切力是决定梁的强度和屈曲安全性的因素。已经发现，在气动梁的横截面中的法向力和弯矩是决定第一次起皱，气动铰链的产生（局部较大变形区域）和膜塌陷的最重要载荷。在第一种方法中忽略了剪应力的影响。; PHM为工业设计提供了一种简单方便的工具，用于设计由空气支撑的膜构建的结构。使用上述思想开发了有限元软件，以检查这种工业结构的屈曲安全性。但是，由于这种简化，仍然有必要确定PHM的精度及其应用范围。目前，通过将PHM的结果与包含起皱可能性的先进膜理论的结果进行比较，可以轻松完成此操作。 Stanuszek（2003）开发了一种基于有限元技术的数值方法来模拟起皱膜的行为。在这种方法中，引入了电缆类比法来定义三角形膜元件中的起皱标准。用Stanuszek公司开发的软件从有限元改进方法获得的结果与实验和PHM方法的结果进行比较。本文研究了几种不同载荷和边界条件的膜来验证PHM。主要目的是研究横向剪切载荷作用下的圆柱形充气膜的情况。已经在横向剪切载荷和分布线载荷下对膜进行了实验测试，以模拟风或自重的影响。将实验结果与使用有限元分析和PHM进行的计算结果进行了比较。比较表明，PHM预测的是主要由轴向力和弯矩加载的膜，其引起首次起皱和塌陷载荷的载荷的精度更高。在横向剪切载荷的情况下，PHM预测的临界载荷值要比更精确的有限元计算更高。而且，已经观察到边界条件的影响可以减小引起膜结构的第一起皱的载荷的值。主要结论是，PHM可以用作设计工具，利用2的安全系数来预测膜的起皱和屈曲。应该理解，PHM为理想的膜提供了引起首次​​起皱的上限载荷。在预测倒塌荷载的同时，它给出了更精确的结果。这是由于以下事实：第一个眨眼现象受到几何缺陷，边界条件和局部变形的强烈影响。塌陷载荷对应于铰链区域中发生的大变形。;通过在预测第一次起皱的公式中添加剪切力的影响，可以轻松地改善PHM。当剪切力引起局部变形并且最先影响起皱临界力时，也建议引入安全系数。

著录项

  • 作者

    Wang, Dajun.;

  • 作者单位

    University of Calgary (Canada).;

  • 授予单位 University of Calgary (Canada).;
  • 学科 Engineering Mechanical.
  • 学位 M.Sc.
  • 年度 2009
  • 页码 110 p.
  • 总页数 110
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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