With the advent of ETFE in the world of lightweight construction, cushion creation has become a common strategy. A cushion is a set of two membranes: one upper and one lower. Therefore, the best way to approach this creation in WinTess3 is to create the two separate membranes and then put them together.

Suppose that we want to build a cushion of 4 x 10 m with a height of 1 m in the upper membrane and 1 m on the lower membrane. We start creating a rectangular mesh of 4 x 10 m. As the ETFE is an isotropic material, we can use a triangular mesh. After we fix all the nodes of the perimeter.

Then through the menu Calculate | Surface loads, we define the structure as pneumatic and introduce an internal pressure of 30 and start calculating Calculate | Iterative process. We will see that we achieve the balance with a deformation less than 1 m. We increase the value of the internal pressure as many times as necessary to achieve a deformation of 1 m.

We save this through the menu File | Save As … with the name of top.tes

Then we are going to turn it over. For this purpose use the Global menu | Translation, rotation and scaling. We introduce the – 1 value in the scaling Z box, and get the lower membrane.

Now we’re going to regain the upper membrane. Through the File menu | Insert & Merge, open the previously saved file, top.tes.

If everything is correct, we see the upper layer in its correct position, and we already have the cushion generated, as shown in the image below.