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toha_mh
Posts: 15
Registered: ‎06-30-2012

Slab deflection and crack

314 Views, 1 Replies
10-17-2012 02:52 AM

Hi,

I am facing some problems regarding slab.

 

1. At first, from Results > Maps the deflections values comes acceptable. But when I go to Required Reinforcement calculation, message comes that the deflection value has exceeded the limit. However, after I click on verification with FEM, it again reduces deflection value.

 

So what is the difference between these deflections? Which one is the nearest to reality? What does the "verification" actually do? When should I click the verification and when I should'n?

 

The whole thing is not clear to me. Can you please explain in your own words?  Because I tried to read the help files and also some previous posts. But didn't understand it clearly.

 

2. Sometimes the cracks also exceeds the limit. Why does this happen and how to reduce it?

 

Please don't mind if my questions are so simple. I am still a student. So there are a lot of things I still don't know. Maybe that's the reason I don't understand these simple things.

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Artur.Kosakowski
Posts: 4,777
Registered: ‎12-17-2010

Re: Slab deflection and crack

10-17-2012 03:01 AM in reply to: toha_mh

1. During linear static analysis value of deflection is calculated for elastic (uncracked) material (concrete). During the RC Slab req. reinf. calculations Robot estimates the average 'cracked' stiffness of  the slab and based on this value increases the deflection. This is estimated method. The stiffness update one calculates real 'cracked' stiffness of each of the element of the mesh and runs static calculations for such modified model. This is more accurate approach.

2. Your SLS load is too large for the slab with the properties (e.g. thickness) as defined. You can increase reinforcement or/and increase thickness of the slab as well as change its grade.



Artur Kosakowski
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