Deflation behavior and related safety assessment of an air-supported membrane structure

As a large span structure that might serve many occupants, the deflation behavior of an air-supported membrane structure under emergency deflation is of critical importance for safety assessment on occupants' evacuation but has received few studies. This paper presents experimental field tests and numerical simulations on deflation behaviors of a real-life air-supported membrane structure. A numerical model is employed in deflation simulation which considers tension-only membrane based on the vector form intrinsic finite element method for membrane motion analysis and pressure change due to air loss in deflation according to the classic thermodynamics. The correctness and the applicability of the model are verified by good correlation of prediction in response of pressure, displacement, and wrinkling formation and development of the structure with those measured and observed in deflation tests. The study shows that the structure in emergency deflation will lose its high pressure quickly first, and then sustain deflating under low residual pressure for a long time. The model is further used in parametrical analysis on factors that affect deflation progress and a complete deflation simulation to predict the whole collapse process, which is accordingly characterized by two typical phases, the tender deflation stage and the severe deflation stage. In tender stage the structure holds a relatively plump form, while in the severe stage the structure bears low decreasing residual pressure, membrane losses most tension stress so that many elements wrinkle and the structure experiences instability. Due to wrinkling, the residual pressure is found to approximately balance with its vertical loads. As a result, the feasible method proposed based on the residual pressure in deflation is very simple and reliable to predict the deflation duration and evaluate maximum escape area for deflation assessment of the studied structure.