I would use the phrase
Nested Shortcodes
to describe it.
You can find many questions using that phrase here on WPSE.
The Codex also uses it, for example here:
http://codex.wordpress.org/Shortcode_API#Nested_Shortcodes
Since the shortcodes in your example are related to the layout, we could perhaps call it:
Nested Layout Shortcodes
to be more specific.
If you have another phrase in mind, or a better suggestion, please share it with us.