Beam finite element for nonlinear analysis of pressurized fabric beam–columns

In this paper, a Timoshenko beam element is developed for the nonlinear analysis of pressurized fabric beam–columns. The analysis is based on an incremental virtual work expression that explicitly includes the work done by pressure under deformation-induced volume changes. Localized compressive buckling of the fabric (commonly termed wrinkling) and geometric nonlinearity arising from P – Δ effects are included in the formulation. Details of the numerical approach used to develop the pressure-dependent, nonlinear moment–curvature relationship for the beam cross-section which accounts for fabric wrinkling are presented. The finite element model is shown to accurately predict experimentally observed load–deflection response of pressurized, coated fabric beams loaded in four-point bending. Simulations indicate that inclusion of the work done by the confined, pressurized air is essential for the accurate calculation of beam stiffness and capacity. In addition, the flexural buckling of pressurized fabric columns is investigated using the finite element model. Fabric wrinkling is shown to significantly reduce buckling loads.