Are you new to the game? Nothing wrong with that, just asking incase you are as there are some learning curves when building. I'll assume you are for the sake of this post, maybe it'll help either way.
But that's definitely an issue regarding structural integrity. As stated before me, make sure where your support columns are, and it isn't over an empty block underneath. Only a solid line from bedrock to surface counts as 100% integrity for a column. I found the easiest test is if you nerd pole up on wood frames, at like 10 or so they'll collapse if there's any open space underneath, provided you are on the surface lol.
As you mentioned your ceiling collapsing, don't forget blocks have a limit on what they can support horizontally in the air. For example, rebar frames can support somewhere around 7 or so, before they'd start to fall, I usually have only a 5 block or less opening in between columns, especially if the wall is only 1 block thick. Also, remember any block attached to another block is counted on its over all structural limits. So say a block can go 10 straight without falling, if you go 8 blocks straight and 3 up,down and/or to the side, it'll collapse without a support column, so always be sure to place columns 1st before connecting.
Though, that's just the frames. If it's reinforced concrete, it's strength is increased. By how much, I can't say from memory. But it's always a good idea to have columns in place before starting on a ceiling/upper floor.
Oh, and don't forget, every block/frame acts like a solid block. So a concrete plate despite missing 90% of the block, structurally is no different from a solid concrete block. This actually allows you to be creative in many ways, like having something seem as if it's hovering off the ground. Just remember things can still pass through if the gap is big enough...
