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

機譯：氣動鉸鏈方法中的剪力效應分析。

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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.
機譯：本文研究了橫向剪切載荷對氣浮圓柱膜起皺和塌陷載荷的影響。橫向剪切載荷會在膜片中產(chǎn)生剪切應力，并且可能是膜片結(jié)構(gòu)屈曲過程中的重要因素。；目前，充氣圓柱膜由于其重量輕且安裝簡單而經(jīng)常用于大型臨時避難所的建設中。 。這些結(jié)構(gòu)是通過組裝細長的圓柱型氣動柱并以這種方式創(chuàng)建一個封閉空間而構(gòu)建的。 Lukasiewicz和Balas在1980年代使用“氣動鉸鏈”（后來稱為PHM方法）的思想，開發(fā)了一種簡化的方法來分析圓柱型空氣支撐膜片的起皺和塌陷載荷，該載荷受到軸向載荷和彎矩。在這種方法中，利用梁模型分析了長圓柱狀的充氣膜，其中彎矩，法向力和剪切力是決定梁的強度和屈曲安全性的因素。已經(jīng)發(fā)現(xiàn)，在氣動梁的橫截面中的法向力和彎矩是決定第一次起皺，氣動鉸鏈的產(chǎn)生（局部較大變形區(qū)域）和膜塌陷的最重要載荷。在第一種方法中忽略了剪應力的影響。; PHM為工業(yè)設計提供了一種簡單方便的工具，用于設計由空氣支撐的膜構(gòu)建的結(jié)構(gòu)。使用上述思想開發(fā)了有限元軟件，以檢查這種工業(yè)結(jié)構(gòu)的屈曲安全性。但是，由于這種簡化，仍然有必要確定PHM的精度及其應用范圍。目前，通過將PHM的結(jié)果與包含起皺可能性的先進膜理論的結(jié)果進行比較，可以輕松完成此操作。 Stanuszek（2003）開發(fā)了一種基于有限元技術(shù)的數(shù)值方法來模擬起皺膜的行為。在這種方法中，引入了電纜類比法來定義三角形膜元件中的起皺標準。用Stanuszek公司開發(fā)的軟件從有限元改進方法獲得的結(jié)果與實驗和PHM方法的結(jié)果進行比較。本文研究了幾種不同載荷和邊界條件的膜來驗證PHM。主要目的是研究橫向剪切載荷作用下的圓柱形充氣膜的情況。已經(jīng)在橫向剪切載荷和分布線載荷下對膜進行了實驗測試，以模擬風或自重的影響。將實驗結(jié)果與使用有限元分析和PHM進行的計算結(jié)果進行了比較。比較表明，PHM預測的是主要由軸向力和彎矩加載的膜，其引起首次起皺和塌陷載荷的載荷的精度更高。在橫向剪切載荷的情況下，PHM預測的臨界載荷值要比更精確的有限元計算更高。而且，已經(jīng)觀察到邊界條件的影響可以減小引起膜結(jié)構(gòu)的第一起皺的載荷的值。主要結(jié)論是，PHM可以用作設計工具，利用2的安全系數(shù)來預測膜的起皺和屈曲。應該理解，PHM為理想的膜提供了引起首次??起皺的上限載荷。在預測倒塌荷載的同時，它給出了更精確的結(jié)果。這是由于以下事實：第一個眨眼現(xiàn)象受到幾何缺陷，邊界條件和局部變形的強烈影響。塌陷載荷對應于鉸鏈區(qū)域中發(fā)生的大變形。;通過在預測第一次起皺的公式中添加剪切力的影響，可以輕松地改善PHM。當剪切力引起局部變形并且最先影響起皺臨界力時，也建議引入安全系數(shù)。

著錄項

  • 作者

    Wang, Dajun.;

  • 作者單位

    University of Calgary (Canada).;

  • 授予單位 University of Calgary (Canada).;
  • 學科 Engineering Mechanical.
  • 學位 M.Sc.
  • 年度 2009
  • 頁碼 110 p.
  • 總頁數(shù) 110
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類 機械、儀表工業(yè);
  • 關(guān)鍵詞

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