This FAQ describes how you can create an opening in a curved 2D-element.
In the example below we use two round tubes:
Use the command intersection (via Input panel > workstation Structure > category 2D Members or by searching in the SCIA Spotlight) or connect members/nodes (via Main menu > Edit > Modify or via the SCIA Spotlight) to generate the intersection between both tubes:
Now the command cutout is available (in the Input panel or via the SCIA Spotlight). Use this command and select both tubes (confirm with the Escape button). Then the parts that can be cutout are indicated. Select the parts that you want to cutout (and confirm with the Escape button):
The result looks like:
Note: you can follow the same steps to create other shapes of openings. For example, you can create an oval opening with shell elements,...