STUDY OF BEHAVIOR UNDER PARTIAL DISTRIBUTED SNOW LOAD AND PROGRESSIVE PONDING CONSIDERING MATERIAL NON-LINEARITY: Study on basic mechanical properties of sealed ETFE air cushion

In recent years, the adoption of the rectangular ETFE cushion as a roof cladding element has become widespread. It is anticipated that this trend will continue and that the size and shape of the panels made of ETFE will become more diverse. But characteristics of ETFE give rise to concern that the local deformation as a result of ponding can increase progressively over time, as additional loading accumulating snow/water causes further deformation of the cushion. In addition, the behavior of the cushion structure exceeding the 1st yield point hasn't been studied and investigated yet. In this paper, the behavior of ETFE sealed air cushion under partially distributed loading was examined and the phenomenon of progressive ponding was studied under water/snow loading. As a result of comparative studies using experiments and numerical analyses taking into account membrane contact, it was confirmed that there was a trend that both upper and lower membranes deformed almost equally keeping the initial cushion depth until inversion occurs under full positive. Membrane displacement under partially distributed loading was greater than loading over 100% of the area and as the aspect ratio of the cushion panel becomes larger, the increment of internal air pressure reduced. The minimum inversion load under partially distributed loading reduced for panels with larger aspect ratios. The loading area which created maximum displacement was different depending on the aspect ratio. It was confirmed that collapse due to progressive ponding phenomenon did not occur under the parameters within the scope of this study.