Cracking width in slabs with Eurocode

[LuisCRodrigues]

I'm trying to understand how RSA calculates the cracking width in slabs according to Eurocode and I have a few doubts.

1 - Is it important that the SLS combinations are "SLS:QPR" type or any combination can be used?

2 - Does RSA ignores the tension resistance of the concrete, ie, for low tension in concrete is it possible to get a crack width of zero?

3 - How difference is the RSA analysis when using the "analytical method" or the "Wood+Armer method"?

4 - One of the info needed for calculation is the diameter of the bars. RSA considers the diameter defined in the "Reinforcement" tab of the "Reinforcements Parameters"of each panel?

Thanks in advance

[Artur.Kosakowski · Accepted solution]

Hi Luis,

1 - Is it important that the SLS combinations are "SLS:QPR" type or any combination can be used?

Yes, it is

2 - Does RSA ignores the tension resistance of the concrete, ie, for low tension in concrete is it possible to get a crack width of zero?

RSA considers tension resitance of concrete till tghe moment cracks appear. If you are below this stress level the cracks can be displayed as 0s.

3 - How difference is the RSA analysis when using the "analytical method" or the "Wood+Armer method"?

The descriptions of both methods are available in Help. I'd say that the prior is more for walls or when you have large Nxy forces. 

4 - One of the info needed for calculation is the diameter of the bars. RSA considers the diameter defined in the "Reinforcement" tab of the "Reinforcements Parameters"of each panel?

Correct.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[LuisCRodrigues]

Thanks, Artur.

Your help is always priceless.

I'm going to implement this in a structure that I'm analysing.

If I have new doubts, I'll get back to this.

[LuisCRodrigues]

Hi Artur

I have some additional points to clarify.

I'm assuming that RSA is calculating the cracking width according to clause 7.3.4 of Eurocode EN 1992-1-1:2004.

1 - Above is expression 7.9 and 7.11 from clause 7.3.4. Is it possible to know the values of the coefficients that RSA considers in calculation? I thinking in the values of fct,eff, alfae, kt, k1, etc.

2 - RSA must calculate the stress in the tension reinforcement assuming a cracked section. Is it possible to see those calculated values in each point of a panel? Something like a map of stress in the tension reinforcement?

3 - In a model where the panels have some reduction factors applied to their stiffness, when calculating the reinforcements RSA shows a warning like "Slab is orthotropic. Calculation is performed for equivalent uniform slab thickness". How can I know the thickness that is been considered?

Thanks in advance

[Artur.Kosakowski]

Hi Luis,

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@LuisCRodrigues wrote:

Hi Artur

I have some additional points to clarify.

I'm assuming that RSA is calculating the cracking width according to clause 7.3.4 of Eurocode EN 1992-1-1:2004.

1 - Above is expression 7.9 and 7.11 from clause 7.3.4. Is it possible to know the values of the coefficients that RSA considers in calculation? I thinking in the values of fct,eff, alfae, kt, k1, etc.

No, as there is no calculation note for the theoretical reinforcement for panels they are not displayed. 

2 - RSA must calculate the stress in the tension reinforcement assuming a cracked section. Is it possible to see those calculated values in each point of a panel? Something like a map of stress in the tension reinforcement?

No, such kind of maps is not available.

3 - In a model where the panels have some reduction factors applied to their stiffness, when calculating the reinforcements RSA shows a warning like "Slab is orthotropic. Calculation is performed for equivalent uniform slab thickness". How can I know the thickness that is been considered?

The one from the Th field.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[LuisCRodrigues]

Hi Artur

Regarding point 1, there are a lot of factors involved in the expressions 7.11 and 7.9.

I may have the need to justify to others (peer reviewer) what RSA is doing and what decisions RSA takes for each factor.

Is there any document that completely explains this? (in RSA help there is only some partial information)

[Artur.Kosakowski · Accepted solution]

Hi @LuisCRodrigues

Indeed it would be helpful but there is no such document.