FINITE ELEMENT ANALYSIS OF AIR-MEMBRANE INTERACTION IN INFLATED MEMBRANE TUBES

Inflated membrane tubes are supported by inflating air from which their stiffness and bearing capacities originate. The deformation of an inflated membrane tube under external loads induces a change in the inner pressure and can therefore affect the stiffness of the tube. This phenomenon features the interaction between the inner air and enveloping membrane. The authors, using the finite element method, numerically analyze the air-membrane interaction in inflated membrane tubes and its variation with the influencing factors. The air-membrane interaction is considered by regarding the inner air as a kind of linear potential flow and the numerical solutions are compared with the corresponding experimental results to verify the validity and accuracy of the finite element model developed herein. Then the inflated membrane tubes are numerically analyzed with the verified model to study the air-membrane interaction and its variation with the initial inner pressure, slenderness ratio, end constraint type and axial compression by comparing the results with those of the tubes in which the inner air is treated as the static boundary conditions of the enveloping membrane. The results indicate that the air-membrane interaction has an important effect on the critical wrinkling load and ultimate bearing capacity and the influence varies non-monotonically, reaching maxima or (and) minima within the ranges of the studied parameters. The present research reveals the air-membrane interaction and is helpful to the understanding of the mechanical behavior of inflated membrane tubes for the reliable design of spatial inflated membrane structures.