Validation and Limits of Finite Inflatable Beam Elements

Abstract

Although nowadays inflatable tubular beams are often used in the field of civil engineering, by now there are only few publications dealing with finite deformation inflatable beam elements, see e.g. [1], [2] and [3]. All formulations of inflatable beams have several assumptions in common, as constant cross sections throughout the deformation, a constant internal gas pressure and the negligence of circumferential stresses. These assumptions have to be validated either by experiments or numerical analysis. In the current contribution beam–like structures are investigated using a finite element shell or membrane formulation and featuring a volume dependent gas loading, see e.g. [5] and [4]. In general the formulation substitutes the internal gas pressure by an energetically equivalent volume dependent loading and thus enables to check for potential gas pressure changes during the deformation process of the inflated beam as a consequence of volume changes. Further local deformations as occurring in the vicinity of supports or almost single loads can be considered. In this paper the focus will be only on the initial assumption of the beam theory that the biaxial stress state is neglected. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Some remarks on load modeling in nonlinear structural analysis–Statics with large deformations–Consistent treatment of follower load effects and load control

“…Wrinkling can be detected, but local effects such as localized Dirichlet boundary conditions leading to cross‐section deformations cannot be taken into account limiting the applications to rather small deformations. In order to investigate problems with larger overall bending deformations a complete membrane tube discretized by finite elements and filled with gas has been studied–including all the terms derived for gas deformation dependence–showing strong local deformations of the cross‐section at the support, see References 24,57. Such deformations indicate a general weakness of air‐filled beam structures in practical applications.…”