Reinforcement design

I am trying to use Design ULS (Area elements) to design the reinforcement requirement for a flat slab, but I find the upper reinforcement is way lower than the lower reinforcement, which seems strange. I think the upper reinforcement refers to top reinforcement for hogging and the lower reinforcement refers to bottem reinforcement for sagging. The top reinforcement should be higher than the bottom reinforcement, so I don’t know where I did wrong. I have attached the two results below, which I hope will show up fine. Could you please give me some insight to this? Thank you!

This is the lower reinforcement:

If the picture legends are correct:

  • 1st picture: Upper reinforcement ULS-design (DC 1)
  • 2st picture: Upper reinforcement SLS-design (crack width) (DC 2)

You are comparing apples with oranges.

Hi sfr, thank you for your reply. My bad that the second one was SLS, but it was lower reinforcement, not the upper one. I have attached the lower reinforcement ULS-design below. It is still way higher than the upper reinforecement.

Just a guess: the top and bottom are true names if the local z is pointing down. Is this your case?

Hi Kirill, thank you for your reply. No I have checked the model and I believe my local z is point up:

So the top and bottom are reversed for you. This is what I was trying to say.

The top and bottom are not global directions, they are directions in relation to the slab. Top is “up” if local z is facing the real “down”

I see. That makes perfect sense. Thank you very much!