Minimum reinforcement: 7.3.3 applied even with indirect crack calculation disabled

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1

I have encountered a confusing issue in RFEM6 when checking the minimum reinforcement according to EN 1992-1-1.

When the program evaluates Eq. (7.1), it does not use the yield strength of reinforcement for σs (as allowed in the note to Eq. (7.1)). Instead, RFEM takes the σs value from Tables 7.2 and 7.3, which are explicitly intended for clause 7.3.3 (indirect crack control).

However, in my calculation settings, indirect crack calculation is completely disabled. I am using only the direct crack calculation according to 7.3.4, so the limits from Tables 7.2/7.3 should not be applied. Despite this, these table values are still used indirectly in defining σs,min, which significantly increases the required minimum reinforcement. In my case, As,min nearly doubles because the software uses approximately 250 MPa instead of the expected 500 MPa (fyk).

So I would like clarification on the following:

  • Is this behaviour intended when only direct crack calculation is selected?
  • If not, could this be a bug?
  • Or is there an additional setting or parameter that I may have overlooked?

Thank you in advance for any clarification.

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4

Hello Pavel,

Yes, this behavior is intended. As indicated in the description of σs, a lower value may be required depending on the situation. The program does not perform the design check according to 7.3.3, it just determines the steel stress based on Table 7.2N.

However, providing an option that allows the user to apply the yield strength as the steel stress for determining the minimum reinforcement according to 7.3.2 could be beneficial. I will discuss this internally.

1 Like
6

Thanks for the clarification. However, the program still implicitly applies the limitations from 7.3.3, even though I haven’t found any clear guidance in Eurocode indicating that this is the way to do. If this interpretation of the clause is discussed or justified somewhere in the literature, I would appreciate a reference.

Thanks.