Concrete Floor with Rebar on Midplane

[TimXHL4R]

I am designing an equipment platform that will be built on an existing concrete floor. The floor is 8in thick and has #5 rebar spaced at 9in running in each direction on the midplane of the floor. I am trying to confirm that the floor will support my platform. 

I have created a new thickness defining the 8in slab. 

Created a slab reinforcement profile that would put the bottom reinforcement at the center of the slab while leaving the top at the default 3/4in

I then go to slab reinforcement and create a reinforcement pattern with the rebar size and spacing and I leave the Top Reinforcement Spacing unchecked to try not to generate it.

When I run the concrete calculations I get the following errors.

I assume this means that the #5 rebar isn't sufficient.

However when I look at the rebar that was generated, it shows a top rebar with a 3/4in cover and a bottom rebar with a 3/4in cover.  When I look at the Calculation Options it shows the parameters for the default "RC Floor" reinforcement parameters. 

Is there anyway to get the calculation options to update to the reinforcement parameters that I assigned to the slab?

Is there anyway to prevent the reinforcement designer from generating a top reinforcement?

Are there any suggestions on how to do this a more efficient way?

[Simau]

Hi @TimXHL4R 

Your question is a bit confusing.
Is there 2 slabs: one existing and another you'll create over the existing ?
Did you apply to your slab the new reinforcement profil (show us its name in the "general tab")
If the bottom reinforcement is at the slab middle, then c1 must be 3.94in

[TimXHL4R]

This structure is going to be built on top of an existing slab, so there won't be a second slab.  

Yes, I applied the Reinforcement Profile to the Slab

Wouldn't putting C1 at 3.94 actually make the centerline of the reinforcement 4.565" (3.94 + Rebar Diameter)?  I would think that in order to get it on the actual midplane you would have to put it at 3.375".  I originally had it there, but kept getting an error that my top and bottom reinforcement were interfering. 

Here are the parameters of foundation elasticity.

[Simau · Accepted solution]

Sorry, I'm not used to Imperial units.

If #5 is a 16mm diameter, then c=(3.94'' - half diameter) = 3.62"

You can't prevent top reinforcement calculation because depending on the loading as in your message 1 there will be negative moments in the slab and therefore top reinforcement. There will also be lifting of the slab so you must check  “uplift box”  in Fondation elasticity parameter.

[TimXHL4R]

Thank you for your help!  I was hoping there was a way have ROBOT check a midplane reinforcement as both a top and a bottom reinforcement.