Non Linear Behaviour of an Inflatable Beam and Limit States

In this work, we consider inflatable beams and define their limit states, in terms of displacements, wrinkling, and collapse of the beam. The definition and properties of the collapse load are highlighted. Concerning the displacements, the strength of material dedicated to inflatable tubes has been studied by different authors, and is considered as well-known now in the linear part of the behavior (before the wrinkle appears). The need concerns now the behavior of the beam in the non-linear part of its behavior. An analytical formulation that allows to get the displacement in this non-linear part, i.e. between the winkling load and the collapse load has recently been written. This approach is here extended to the use of a beam finite element with which the displacements can be obtained from light loads to the collapse load of more complex structures. The case of an inflatable arch is presented as an example.