I was thinking. The position of the young architect is to speculate, WHAT IF?... Not to solve all the detailed how to's, Just enough to provoke further interest.
image via Atelier Subterranean - Roger von Oech



Using span to depth ratios we did last semester I was able check column widths. By my calculations a 130 square closed grade c350 steel column could take 6 stories at 9m spacing.
The main thing for me here was that 500 square would be enough for structure and services, it looks ok