SCL Placement for Fillet Welds in ASME VIII Div. 2 DBA

[Mecat24]

Hello everyone,
Here is my question about a topic that raises doubts in my mind according to different opinions that have been given:
For a plastic collapse and a local failure analyses using the Elastic Stress Analysis Method, for a component under ASME VIII, Div. 2, Part 5, 2021, with a fillet weld connection:

Is it necessary/required to plot a SCL in the weld throat? Or should it only be done at the weld toe?

I’d really appreciate it if anyone could share their insights or point me toward helpful resources. Thank you in advance for your time and support!

 

[IdanPV]

Follow this thread in Linkedin, I hope it will help you with that issue

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[Mecat24]

Follow this thread in Linkedin, I hope it will help you with that issue

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500 million+ members | Manage your professional identity. Build and engage with your professional network. Access knowledge, insights and opportunities.

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thank you so much! but I can't seem to access the post. Any alternative link or name of the post to identify?

 

[TGS4]

@Mecat24 - you need to join the ASME PVP LinkedIn forum to be able to access the thread.

 

[Mecat24]

Thank you both very much. If I was able to see the correct link and if I didn't miss anything, I see that it refers to a fatigue analysis and it doesn't look like a fillet weld. Am I right? If so, it moves away from my original concern.
Should I plot an SCL at the throat of a fillet weld for plastic collapse and local failure, in viii.2.part5, version 2021? Or would that leave an SCL invalid and only the toe of the weld should be evaluated?

 

[IdanPV]

See Figures 5-A.1 and 5-A.5

 

[Mecat24]

Yes, thank you. I have seen them.
I insist on this topic because ANNEX 5-A is informative, and in those figures, there is a fillet, but you can also see in the mesh that they have full penetration.
What I am proposing is a case like this: Imagine a T-joint with a fillet weld. Only a fillet weld, without full penetration. All the load of the connection is carried through that fillet.
So, in a case like this, should the SCL still pass through the weld toe? In other words, is the "triangle" of the fillet a transition element?
Thank you very much for your support.

 

[TGS4]

When it comes to the topic of SCLs, their placement, etc - the best that I can do for you is to refer you to 5.2.1.2.:

For components with a complex geometry and/or complex loading, the categorization of stresses requires significant knowledge and judgment. This is especially true for three-dimensional stress fields. Application of the limit load or elastic–plastic analysis methods in 5.2.3 and 5.2.4, respectively, is recommended for cases where the categorization process may produce ambiguous results.

 

[Mecat24]

Thank you very much. Yes, I agree.
If I may, I’d like to revisit a point. What I am aiming for is not to solve a particular case but to improve the understanding.
I have resolved more than one case with fillet welds, using continuum elements, both fully 3D models and axisymmetric cases. Following the guidelines of ANNEX 5-A, I did not find an example of an SCL at the weld throat in a fillet weld, like the one mentioned, that provides a valid SCL according to those guidelines.
That said, I think it is not possible to generalize based on examples. There may be cases where validity for the SCL is found. However, that does not seem to be a methodology that is practically applicable to complex cases where this SCL-by-SCL evaluation procedure would need to be repeated.
Considering that ASME BPVC has been extremely precise and explicit when necessary (for example, in ASME BPVC.III.APP, Mandatory Appendix XXVII, XXVII-3520 Shear Stress) but has not been equally explicit regarding shear stress at the throat of partial penetration and fillet welds in ASME BPVC.VIII.2.Part 5, I believe the solution based on stress at the weld toe should be adequate for the case mentioned.
Furthermore, I believe that the design margins possibly adequately cover those positions where it is not specifically required to meet the design condition for plastic collapse, for instance. However, this is part of what I want to understand, whether this is truly the case or not.
What are your thoughts on this approach? Do you think it aligns with the intent of the code, or is there another perspective to consider?

 

[TGS4]

That is a matter for your engineering judgement.

And it is a matter of whether your jurisdiction having authority or your AI (and their AIA) agrees with that judgement.

 

[Mecat24]

Thank you, that’s clear to me