Finite-element analysis of tubular fabric beams including pressure effects and local fabric wrinkling

Pressurized beams made from synthetic fibers that are woven or braided into a circular cross-section are used as main load-carrying members in a variety of terrestrial and space structures. This paper focuses on the development of a Timoshenko beam finite element for the nonlinear load–deflection analysis of pressurized fabric beams, and the numerical examination of the effect of pressure on beam load–deflection behavior. The basis of the element formulation is an incremental virtual work expression that explicitly includes the work done by pressure under deformation-induced volume changes. The inability of the fabric to carry significant compressive stress is accommodated with a nonlinear moment–curvature relationship. Details of the element development and solution methodology are provided. Parametric studies that demonstrate the importance of including work done by pressure and wrinkling-induced moment–curvature nonlinearity in the formulation are described. These studies indicate that not only does beam stiffness increase with inflation pressure, but work done by pressure increases the beam bending capacity well beyond the theoretical limiting value. Further, accurate prediction of the nonlinear load–displacement response requires the inclusion of work done by pressure due to both shear and bending deformations.