Very Large Variance in reinforcing based on Eurocode Environmental factor

[conor_coburn]

I am running an analysis and find that the concrete reinforcing looks reasonable if I use a Eurocode XC1 environmental class, while if I use an XC3 Environmental class, it double in parts of the slab and  becomes really high in parts of the slab that are seeing little stress. See attached, just run the analysis with XC1 and XC3 and compare results of steel area using the reinforcement maps. Is this a problem with teh software, am I missing something in the EUROCODE? 

[Artur.Kosakowski]

Hi @conor_coburn

If I remember correctly EC2 sets limits on stresses in reinforcement steel depending on the environmental class which in turn dictate bar spacing reinforcement area). 

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[conor_coburn]

EC2 gives recommendations on crack widths based on exposure classes (Table 7.1N) and also suggests compressive stress limitations on concrete for XD, XF and XS exposure classes (Section 7.2(3)) . But I cant find a requirement for limits on stress in reinforcing based on reinf. stress. So still don't under stand the big difference in reinf. going from going from XC1 to XC3 while manually keeping the crack width limit at 0.3. Is the exposure class overriding the manually selected crack width? 

[Artur.Kosakowski]

Hi @conor_coburn

Check https://forums.autodesk.com/t5/robot-structural-analysis-forum/ec2-minimum-reinforcement-in-slabs-no...

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[conor_coburn]

The answer in the post you directed me to is somewhat unclear.

1) Looking at Note 1 in table 7.1N, you imply that based on the note for XC0 & XC1 Environmental classes there is not a requirement to meet section 7.3.2 Minimum reinforcing areas. Then you say "Anyway for these two classes when you set reinforcement adjustment for crack limit then the required area of reinforcement will be increased to the point the cracks are below the defined limit."  So for example if I set the crack limit for 0.3 mm & the Environmental class to XC1. What does ROBOT use to calculate the Reinf? The Rigorous method given in 7.3.2(2)?

2) You imply that for Environmental class XC2 and above Robot checks to 7.3.2 Minimum reinforcement areas, Why not use the Rigorous method given in 7.3.2(2) that you may have used for XC0 & XC1?

3) My reinf. is shooting up at small overhangs that have very little stress, so this does not make sense to me. 

[Artur.Kosakowski · Accepted solution]

HI @conor_coburn

Could you attach the model and indicate the panel to look at?

I will need to check this with my colleagues from the development team but I will not be able to meet them earlier than in two weeks time 

[conor_coburn]

The Zip of the model was attached to the first post of this issue.  I am attaching to this post screen shots of the model with the calculated reinf. shown for the model with XC1 as the environmental class and XC3 as the environmental class. No other change. Big difference in Reinf. 

[conor_coburn]

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