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Crack width calculation for reinforced concrete

26 REPLIES 26
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Message 1 of 27
gn
Explorer
6410 Views, 26 Replies

Crack width calculation for reinforced concrete

Guy's

 

I am trying to get detailed calculations for crack widths in RSA, although I input limiting crack widths in the reinforcement calculations, I wondered if there was a detailed output given by robot without going into the spreadsheet calculator extension.

 

Further I have veiwed the 2 youtube tutorials on the spreadsheet calculator, and was wondering if there are any further tutorials or learning material for it.

 

Thanks again.

 

Gavin

 

 

26 REPLIES 26
Message 21 of 27

Rafal,

 

I've contacted authors of the book example and they both agree there's an error in their example (regarding cracks width calculation).

They are thankful for good remarks.  🙂

 

They think that this "c" variable in EC2 (7.11) shouldn't be called "c" because according to EC2 4.4.1.1. (1) - "c" stands for  "The concrete cover is the distance between the surface of the reinforcement closest to the nearest concrete surface (including links and stirrups and surface reinforcement where relevant) and the nearest concrete surface.", but that's completly another thing to discuss.

 

After all, I am glad that error is in their example, not Robot.  😄

 

Still waiting for the second part of the answer (regarding calculation of deflections).

If this solved your issue, please Accept it as Solution help other forum users with similar issues to find answers easily.
  
Mirko Jurcevic


My blog: www.engipedia.com
Try my Revit add-ins: Autodesk App Store
Message 22 of 27

Still waiting for the second part of the answer (regarding calculation of deflections).

 

Almost ready.

Translating now.



Rafal Gaweda
Message 23 of 27
Rafal.Gaweda
in reply to: Rafal.Gaweda

The RSA does not take into account the effect of shrinkage.

In the attached case, the effect of shrinkage is: 9.43 * 10 ^ -6/4.183 ^ 5 = 0,225 -> 22%

If from book result 27.9 we subtract (22%* 27.9 😃  6.28 we get 21.6mm

 

Minor differences: when we detect that the concrete is "typical" (ie, as in the EC2 table) , the Young modulus is taken from the table and not calculated.

 

The differences in the position of the rebar  can change the moment of inertia.

 

However, this would explain the differences of a few rather than 10%

 

When you set “Display diagrams  for all combinations”, we get instead of 21.6mm 20.9mm -> 0.7mm.

(Difference near 3% already may be due to other differences I mentioned earlier)

 

displaydiag.jpg

 

The mistake is located in taking the final calculation of the elastic deflection as of the envelope of all combinations and not as an envelope of  QPR combinations. Need to be corrected in software.



Rafal Gaweda
Message 24 of 27

I've finally manage to carefully read your post.

Thank you very much Rafal for your effort.

I am glad we resolved this. Hope it will be corrected soon.

If this solved your issue, please Accept it as Solution help other forum users with similar issues to find answers easily.
  
Mirko Jurcevic


My blog: www.engipedia.com
Try my Revit add-ins: Autodesk App Store
Message 25 of 27
Jummybear
in reply to: Rafal.Gaweda

in you pic you have bar position in m with 5 marks after coma, i have only 2 marks. How to fix it? Didnt find anything about that in job pref-s..

Message 26 of 27
Rafal.Gaweda
in reply to: Jummybear

rcuni.jpg



Rafal Gaweda
Message 27 of 27
pmackevicius
in reply to: gn

Hello, gentleman,

 

Sorry for butting in, but I have a question regarding crack calculation.

 

I have to design a septic tank, and I would like to calculate / check width of crack with DISREGARD of effect of concrete in tensile zone (I want to know the additional amount of reinforcement, when I calculate a panel as if it already is cracked – I hope I am explaining it understandably).

 

To disregard the effect of concrete in tensile zone, I have to delete (or set value as 0 MPa) a tensile strength of concrete, but in “Custom material properties” tab there is no such value to change.

 

So, maybe there is a different way to define tensile strength of concrete?

 

Thank you in advance,

 

Best regards,

Paul.

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