I think “the whole thing” makes the rigidity it is not beam and post.
This is how our shed is made.
It does not use “sine wave” corrugation. It’s “square wave” corrugation. Which gives it more rigidity when the panels are joined together and overlapping. This also gives the walls better “snow load” for taking weight on the roof.
It has two metal rafters together ( back to back) in the center. Then another rafter halfway between the centre and the outside edge ( both left and right of centre).
When looking in through the door.
It has a trim that goes all around the top edge and the bottom edge that the sides panels are screwed into. I couldn’t really see … but I think the bottom edge is screwed/bolted into the concrete.
It has metal bracing which is at waist height which runs around the walls like a shelf.
The door frame
The doorway has 2×4 inch wood studs around it that make up the door frame.