(Version >= 3.91)
If we want to generate a membrane structure like the one shown in the picture below

Complex model

we can do so through the union (mixture) of different simple elements.

This is generated, through File menu | New | 2 arches, as a module with 8 meters wide (opening of the arch) and 5 meters in length (distance between arches). We set the height of the central point in 1 meter. The border deflection = 0 m. Keep this mesh in a file, central.tes.

Center module

Then again using File menu | New | 2 arches generate a module of 5 meters long (distance between the base of the arches) and 8 meters wide (opening of the arch), but this time arch on the left is inclined 30 degrees outward. We set the height of the central point in 1 meter. We keep this mesh in a file medio.tes.

Half module

Finally, again via the menu File | New | 2 arches we generate a module of 8 meters wide (opening of the bow) and 3 meters in length (distance between the base of the arch and the extreme left), but this time the arc on the right are inclined 30 degrees inward. And enter height of the Arch as 0 m, with which we obtain a straight edge on the ground. The height of the central point is at 0.8 meters. We keep this mesh in a file lateral.tes.

Side module

Letā€™s move to the phase of joining the parts. First we are going to turn on the visual of the coordinate axes to know the point of insertion of the modules at all times. Click on the top of the chart with three colored axis in lower left corner.

XYZ axis which show where is the center of coordinates

Using the File menu | Insert & merge, we open the file medio.tes that we had saved earlier and get

Side and center modules

Now we change the center of coordinates and we must move it to the corner right-bottom of the whole structure (before merging).

New center of coordinates

We are about to repeat the same operation as before, but now we open the file central.tes.

Half of the set

We have half of the set. We return to modify the Center coordinates and return it to put in the corner right-bottom node. However now we will not open any file but apply a symmetry in the axis X by the button on the left toolbar.

Symmetry in the X axis

It seems that we have already generated the set, but not so. We only have half but what you see is duplication by symmetry. In fact, if we click number the nodes (nN) button, we will see that only half of them are numbered (see previous figure). To ensure that this duplicate image is the actual image we must go to Global menu | Current symmetry > > new structure.

Once this is done, we get the structure in the first figure of this text.