Slabs crack control

[marko.glavinic89]

I have a problem regarding crack control in RC slabs. I have created a SLS:QPR combination with aqequate load factors, and when i run the reinforcement calculation everything goes well. I get the required reinforcement area, aswell as deflections, but i cannot obtain crack width no matter what I do. 

Can you help me, I attached the model with no results.

[Anonymous]

Isn't there anyone who knows what may cause this problem? I am not able to get crack widths either which is odd since concrete always cracks.

[Rafal.Gaweda]

It cracks, but only in one node so it is hard to display map.

This is 100cm slab with RC deflection of 2mm max

[Anonymous]

I have a ground bearing slab that has no cracks. How do you explain that?

[Rafal.Gaweda]

50 cm slab with RC delfection 3,7mm....

[Anonymous]

Are you suggesting that the deflection is so small that there should be no cracks?

[Rafal.Gaweda]

seems so.

[Anonymous]

I dropped the foundation elasticity quite a bit and got a much greater deflection but there is still no cracks. There is no way this is correct.

[Rafal.Gaweda]

If wrong - please send me your hand calcs to compare

[Rafal.Gaweda]

From "tomorrow" webinar:

[Anonymous]

Thank you for that information. Looks more believable. This method doesn't take into account reinforcement or changes in the stiffness caused by cracking does it?

[Rafal.Gaweda]

????????
If slab is situated on the soil (in Robot on elastic ground), it will not deflect deeper (even considering cracks and reinforcement) than calculated in FEM model because soil prevents this.

[Anonymous]

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@Rafal.Gaweda wrote:
????????
If slab is situated on the soil (in Robot on elastic ground), it will not deflect deeper (even considering cracks and reinforcement) than calculated in FEM model because soil prevents this.

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Bending causes deflection and since concrete can't take tensile strain, we use reinforcement. We can diminish the crack width using more reinforcement. It's not a question of deflection getting deeper. Also this is only true when the deflection is downwards which it always isn't.

[Rafal.Gaweda]

Please attend today webinar.
http://forums.autodesk.com/t5/robot-structural-analysis/robot-structural-analysis-webinars/td-p/5523...