Continuous mesh structures from curves

You could try the ‘fattener’ component from here:

For structures like the one you show this should work fine:
frame_fatten.gh (8.2 KB) (you’ll need to first install the .gha from the link above)

In Rhino 7 there is also the ‘MultiPipe’ command, which can handle more complex geometries, and will at some future point also become a grasshopper component.