As a general matter, no: a structure is something affixed to the ground, not something portable which can be moved at will. A playground set, for example, if the support posts are sunk into the ground, would be a structure; a trampoline, resting on the ground, would not be. That said, if you are running afoul of HOA rules or local zoning regulations, you have to check those rules or regulations to see if they define "structure" in a way that would take in the hoop; if they do, such an atypical definition, since it is in the rules or regulations, is enforceable.