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Proceedings ArticleDOI

Analysis of General Shells Under Deformation Dependent Pressure loads Using a Flat Triangular Shell Element

20 Apr 1998-
TL;DR: In this paper, a flat triangular shell element is obtained by combining the Discrete Kirchhoff Theory (DKT) plate bending element and a membrane element similar to the Allman element, but derived from the Linear Strain Triangular (LST) element.
Abstract: 1. Abstract Finite element large deformation analysis of general shells under deformation dependent pressure loads using a three-noded flat triangular shell element is presented. The flat shell element is obtained by combining the Discrete Kirchhoff Theory (DKT) plate bending element and a membrane element similar to the Allman element, but derived from the Linear Strain Triangular (LST) element. The follower effects of the pressure load are included in the finite element formulation. The pressure stiffness matrix and the deformation dependent pressure load vector in a Cartesian coordinate system are systematically derived from the principle of virtual work. Results are presented for a cantilever beam under uniform external pressure and a thin circular ring under non-uniform external pressure. The element will be used in the near future for the analysis of a large inflatable structure which is highly flexible and is expected to undergo large deformations and rotations. In order to estimate the accuracy of the present formulation in predicting the nonlinear response of large structures, analysis of a thin circular arch under internal and external pressure loads is performed. The arch presented is a building block of a large inflatable structure. The present results are in good agreement with the results available in the existing literature and those obtained using the commercial finite element software ABAQUS, where ever applicable, demonstrating the accuracy of the present formulation.
Citations
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Journal ArticleDOI
TL;DR: In this article, a flexible material, such as a woven or braided fabric, may be tailored to form an arch when inflated, and an analytical solution for these initial stresses is given for an arbitrary arch centerline shape.

33 citations

Journal ArticleDOI
TL;DR: In this article, a triangular flat shell element for large deformation analysis of linear viscoelastic laminated composites is presented, and the nonlinear deformation process is computed using an incremental/iterative approach with the Newton-Raphson Method used to find the incremental displacements in each step.
Abstract: A triangular flat shell element for large deformation analysis of linear viscoelastic laminated composites is presented. Hygrothermorheologically simple materials are considered for which a change in the hygrothermal environment results in a horizontal shifting of the relaxation moduli curves on a log time scale, in addition to the usual hygrothermal loads. Recurrence relations are developed and implemented for the evaluation of the viscoelastic memory loads. The nonlinear deformation process is computed using an incremental/iterative approach with the Newton-Raphson Method used to find the incremental displacements in each step. The presented numerical examples consider the large deformation and stability of linear viscoelastic structures under deformation-independent mechanical loads, deformation-dependent pressure loads, and thermal loads. Unlike elastic structures that have a single critical load value associated with a given snapping of buckling instability phenomenon, viscoelastic structures will usually exhibit a particular instability for a range of applied loads over a range of critical times. Both creep buckling and snap-through examples are presented here. In some cases, viscoelastic results are also obtained using the quasielastic method in which load-history effects are ignored, and time-varying viscoelastic properties are simply used in a series of elastic problems. The presented numerical examples demonstrate the capability and accuracy of the formulation.

16 citations

Dissertation
12 Nov 2004
TL;DR: In this paper, a flexible tent with an interior collective protection system, which is subjected to an explosion, is analyzed, and the results showed that the effect of fluid-structure interaction should be considered in the pressure load calculation on the structure where the structural deflection rate can influence the solution of the flow field surrounding the structure.
Abstract: Recently, numerous flexible structures have been employed in various fields of industry. Loading conditions sustained by these flexible structures are often not described well enough for engineering analyses even though these conditions are important. Here, a flexible tent with an interior Collective Protection System, which is subjected to an explosion, is analyzed. The tent protects personnel from biological and chemical agents with a pressurized liner inside the tent as an environmental barrier. Field tests showed unexpected damage to the liner, and most of the damage occurred on tent’s leeward side. To solve this problem, various tests and analyses have been performed, involving material characteristics of the liner, canvas, and zip seals, modeling of the blast loading over the tent and inside the tent, and structural response of the tent to the blast loading as collaborative research works with others. It was found that the blast loading and the structural response can not be analyzed separately due to the interaction between the flexible structure and the dynamic pressure loading. In this dissertation, the dynamic loadings imposed on both the interior and the exterior sides of the tent structure due to the airblasts and the resulting dynamic responses were studied. First, the blast loadings were obtained by a newly proposed theoretical method of analytical/empirical models which was developed into a FORTRAN program. Then, a numerical method of an iterative Fluid-Structure Interaction using Computational Fluid Dynamics and Computational Structural Dynamics was employed to simulate the blast wave propagation inside and outside the flexible structure and to calculate the dynamic loads on it. All the results were compared with the field test data conducted by the Air Force Research Laboratory. The experimental pressure data were gathered from pressure gauges attached to the tent surfaces at different locations. The comparison showed that the proposed methods can be a good design tool to analyze the loading conditions for rigid or flexible structures under explosive loads. In particular, the causes of the failure of the liner on the leeward were explained. Also, the results showed that the effect of fluid-structure interaction should be considered in the pressure load calculation on the structure where the structural deflection rate can influence the solution of the flow field surrounding the structure.

12 citations

References
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Book
01 Jan 1969
TL;DR: In this article, the authors propose a linearized theory of elasticity for tensors, which they call Linearized Theory of Elasticity (LTHE), which is based on tensors and elasticity.
Abstract: 1. Vectors and Tensors. 2. Strain and Deformation. 3. General Principles. 4. Constitutive Equations. 5. Fluid Mechanics. 6. Linearized Theory of Elasticity. Appendix I: Tensors. Appendix II: Orthogonal Curvilinear.

3,658 citations

Journal ArticleDOI
TL;DR: In this article, a modified version of the Newton-Raphson method is proposed to overcome limit points in the finite element method with a fixed load level and a constraint equation.

1,581 citations

Journal ArticleDOI
TL;DR: In this article, an assessment of flat triangular plate bending elements with displacement degrees-of-freedom at the three comer nodes only is presented, with the purpose of identifying the most effective for thin plate analysis.
Abstract: SUMMARY An assessment of flat triangular plate bending elements with displacement degrees-of-freedom at the three comer nodes only is presented, with the purpose of identifying the most effective for thin plate analysis. Based on a review of currently available elements, specific attention is given to the theoretical and numerical evaluation of three triangular 9 degrees-of-freedom elements; namely, a discrete Kirchhoff theory (DKT) element, a hybrid stress model (HSM) element and a selective reduced integration (SRI) element. New and efficient formulations of these elements are discussed in detail and the results of several example analyses are given. It is concluded that the most efficient and reliable three-node plate bending elements are the DKT and HSM elements.

800 citations

Journal ArticleDOI
TL;DR: In this article, a simple triangular finite element for plane elasticity analysis is derived from compatible quadratic displacements with vertex connectors which include rotations, and the results show that quite acceptable accuracy is available for practical applications.

476 citations