There's probably no technical reason such structures couldn't be built, just economic ones. I can't think of any application where the use would justify the construction and maintenance costs. There may be applications of this sort for things like floating oil rigs, space ports, hazardous material handling facilities, etc. For smaller installations, like floating research stations, ships are the way to go. You can always drive (or tow) them home for yard work.

What I'd like to see are peacetime applications for decommissioned nuclear submarines. All ships wear out, but those pressure hulls, with minimum maintenance, should be practically eternal. A missile boat, with all weapons removed and perhaps with it's engines replaced by conventional diesels, would make a dandy mobile marine laboratory, or even a static sea bottom base. And if we could find a way to lift one into orbit, it might make a great deep space probe!