It looks to me like the upper floors are steel construction with steel columns, beams and Robinson or Verco deck (corrugated steel) with concrete poured on top. The lower floors appear to be cast concrete with post tension decks.
Agreed. (See my post #42), And if this had been a ‘Stocking Materials Saturday’ the fact that the man lift car was empty of stockers, (I think/I hope), and only up on about at 3 or 4 when the collapse happened might have saved many 18 to 21 year old kids/cubby lives. Good God I hate to see this. I saw enough back in the day long ago. Prayers up for the injured and now dead.