Computational method for in-situ finite element modeling of inflatable membrane structures based on geometrical shape measurement using photogrammetry

Abstract

Inflatable membrane structures with the advantages of light weight, large span, long duration and aesthetical appearance have gained considerable attentions from buildings, super-pressure balloons, airships and deployable antennas. This paper presents a novel computational method for in-situ finite element modeling of inflatable membrane structures based on geometrical shape measurement using photogrammetry for further structural analysis. Firstly, kinematic equations of membrane link structure simplified from the measured inflatable membrane structure are established on force equilibrium between membrane internal and external forces to calculate the tensile forces. Then, computational method for solving zero-stress state is proposed through unloading internal pressure based on equilibrium matrix theory. Finally, true finite element model is established through numerical simulation of reloading internal pressure with considering the zero-stress state as initial model. For verifying purpose, inflated forming and normal working tests of an ethylene-tetrafluoroethylene (ETFE) air-inflated cushion structure were carried out. By comparing geometrical shapes and stress distributions of ETFE cushion between numerical and experimental results, good agreements with 0.72% and 4.76% maximum errors are acquired. These findings strongly confirm the need of in-situ finite element modeling of inflatable membrane structures undergoing long-term service and provide an effective computational method for further structural analysis.