Hello,

I got differents Bending/Torsion stresses results (50%) at the branch if I fill the "type" of the Tee or fill the SIFi/SIFo computed by Caesar 5.30.03 (Build 120131).

I check this with Welding/Weldolet and codes B31.3 and CODETI. So it seems independant of the Type of connection and Codes.

If I calculate Sb manualy, the good result seems to be when the SIFi/SIFo are filled.

Any explanation?

Without looking at your model, my only thought is that the "in-plane" versus "out-of-plane" directions have been mixed up. Did you put your manual values in the correct fields?

Hi,

I have also noticed the same weirdness : very different bending/torsion stress results in branch connections (and sometimes in headers too), if the type of the branch is filled, or if I only manually implement exactly the same values of SIFi/SIFo.

Considering that roughly Sb = iM/Z, and that with or without the type of intersection filled, the SIFs ii/io and the bending moments Mi/Mo are the same, the fact that the results are sometimes very different lead me to question the section modulus used in branches.
After a some tests and manual calculations, I came up with the hypothesis that, surprisingly, CAESAR may not use the same branch section modulus for stress calculation, depending on whether or not the user specifies the type of intersection…???

I couldn’t confirm nor invalid this theory because is it impossible to know what section modulus the stress calculations are based on. I don’t think its displayed anywhere in the software… ?

Please note that if you fill in the SIFi/SIFo you have to do this for all three elements that enter/exit the intersection.

If you don't, only the element you enter the SIF will have SIFi/SIFo that you specified, the others will consider SIF 1.

Is this explaining your results?

Hello Dan,

Thanx for your advice, but the SIFi/SIFo are, of course, entered on each of the 3 branches of the intersections. I carefully pay attention to that. so it cannot be the explanation...

In this case, can you post here a sample file? I can not confirm on my computer your findings.

Regards,

The guessing game continues...
B31.3 has an effective section modulus for reduced outlet branches. Check that calculation if that's the code you are using.

Hi Dave,

Thanx for the tip, the code was codeti, but it has an effective section modulus for branches too.
I manually checked the stress calculations with this modulus, it seems to match Caesar’s results when the type of intersection is filled. So, I guess the “good results” (aka. : in compliance with the code) occur when the type of fitting is filled.
still, it doesn’t explain why the results are different (sometimes significantly higher) when the same SIFs are manually entered…
shouldn’t it be exactly the same ???

best regards.