TTU option - Flexibility of the shell - Internal Spring

[CharlesEd]

Hello,

I am having a hard time with tees in my model right now, I have many and most of them stand above 100 % of Utilization rate in my stress analysis. A colleague showed me the "consider the flexibility of the shell by an internal spring" option that he uses to lower the Utilization rate when he needs it. Yet, he has no idea how it works.

I checked the ROHR2basic manual and the paragraph related to that is quite technical and abstract. And I don't have access to ASME B31J. So basically, I don't understand what is that option and, most importantly, when it can/should be used.

Could you ELI5 what is that option and when I can use it, if I can at all?

Thank you in advance for your time!

[rohr2support]

Dear ROHR2 User

ASME B31J specifies new stress intensification and flexibility factors for Tees.
When you use ASME B31.3 stress analysis the additional flexibility of the shell to branch junction can reduce the bending moments in the system and thereby reduce the calculated stresses.
At the same time, some of the stress intensification factors are slightly higher than in the older codes (like older version of ASME B31.3)

As the ASME B31J includes the stress intensification factors and the flexibility factors they can be used together without problems.

In ROHR2 you can also apply these flexibility factors for other stress codes, but combination of factors from different stress codes should be avoided or done carefully to make sure you still do a sensible analysis.

Best regards

ROHR2 Support.

[CharlesEd]

Thank you for your explanation!