Problem with Staad Design to Eurocode

Hello,

I have a problem in a staad design to Eurocode 3.

I modeled a support and I asked to check the profiles to Eurocode.

When We check the applied stress in the U profile, We obtain 233 N/mm², the same beam checked to the closes of Eurocode 3 give a maximum ratio of 0.426.

My colleague done the same analysis under Autodesk Robot Structural Analysis Professional 2020 and He obtain a maximum ratio of 1.00. I attached the .STD file and the ROBOT result obtained by my colleague.

If  You can help to understand what's wrong.

Thank's in advance.

Mohamed ARHAB

Bras déport.std

  • First of all, the analysis results seems to be different (N,Ed, Mz, Ed, etc.). If the forces on the member are different, then the design results will be different too.

    Secondly, I can see that STAAD classifies this this member as a class 4 section. However, I noticed in the output file that effective area of this members is higher than gross area, which does not seem logical. I will ask the development team to check this and confirm if this is a bug.




  • Thank You Modestas for Your reply.

    Yes the profile is a Class 4. the effective area must be less or equal to gross area.

    Second strange point, is that the profile is S235 grade steel, with Yield stress of 235 N/mm². Cause the profile is Class 4, It's seems that the failure must happen for a stress less than the Yield one. Or when we check the total compression stress on the beam 3 We have 233 N/mm². So logicaly It's impossible to obtain ratio of 0.426.

    I'm waiting for Your reply to this problem.

    Thank's in advance.


  • Thank You Modestas for Your reply.

    Yes the profile is a Class 4. the effective area must be less or equal to gross area.

    Second strange point, is that the profile is S235 grade steel, with Yield stress of 235 N/mm². Cause the profile is Class 4, It's seems that the failure must happen for a stress less than the Yield one. Or when we check the total compression stress on the beam 3 We have 233 N/mm². So logicaly It's impossible to obtain ratio of 0.426.

    I'm waiting for Your reply to this problem.

    Thank's in advance.

  • The development team confirmed this issue as a Bug #914240 and it should be fixed in the upcoming STAAD.Pro versions. We sincerely apologize for the inconveniences and thank you for bringing this issue into out attention.



  • After the deeper investigation it appears that unexpected effective areas are due to input error in the UPT section. You have used the D value as 30 mm while B as 60 mm for the custom section. However, if you are using a GST parameter with a value of 1, you are asking the program to design this section as a channel section. If the program uses your input, then the height of this custom channel is consider as 30 mm and width (flange length) as 60 mm, which is not correct based on your drawing. So basically you need to switch D and B values so that D becomes as 60 mm and B as 30 mm.

    After these modifications, the section will be classified as Class 1 based on EN 1993-1-1 table 5.2 which seems to be correct. If you think that the section class is incorrect, please send us your hand calculations for further investigation. Thank you.