Judging by the first drawing, they are some form of prefabricated concrete slabs. What they actually can withstand is information I can't find. The only way to find out is to contact AB Färila Cementvaror, but I suspect that it's difficult. The only thing that can be said with certainty is that they meet the then-current standard requirements for useful load in residential buildings, 50 kg/sqm stationary and 100 kg/sqm moving.