Why are the calculated SIF results between 2 Tees that have the exact same size branch and material different in AutoPIPE's model input listing sub-report?
SIF for in-plane: A01 = 1.996, C01 = 2.114,
Why are these values different?
The following discussion are general steps used to review the model and calculated results. This process can be adapted for other similar situations.
1. First, look at the Code and Code year the model is being analyzed too? answer = B31.3 - 2006
2. Next Review the code for SIF calculations per type of Tee (ex. welded).
Please see the following AutoPIPE help section:
Help > Contents> Contents Tab> Reference Information> Code Compliance Calculations>ASME B31.3 (2006)> Flexibility and SIF> find type of tee (welded)
Note the code calculation for SIF In-plane is based on SIF out-of-plane, which is solely based on the geometry of the Tee, tee run piping wall thickness (Tbar) and tee run pipe rad. distance (r2)
3. Next review the model listing to be sure that no override option has been enabled.
This report clearly shows that the calculated value of the Tee SIF for node point A01 was 2.00u and for node point C01 was 2.11.
Question: what does the "U" mean in 2.00u?
Answer: At the bottom of this sub-report u is defined, "u = User SIF specified for header or branch, check User SIF data listing."
Therefore, if "u" appears after any SIF value in the Tee or Bend data listing, always review the "User SIF" (also known as: Joint Type / User - SIF Data Listing) sub-report to confirm SIF used in code compliance calculations.
See Code Compliance sub-report:
Noticed for node point A01 that the program used the calculated SIF for the run of the Tee and used the override values for the branch of the tee.
4. To answer the question on why AutoPIPE has 2 different SIF values for similar tees, go back to SIF code calculation mage in step #2 above and notice the nomenclature for flexibility variables are Tbar and r2, These values are found based on the Tees pipe properties and printed in the Tee Data listing above. Clearly these numbers are different and thus the resulting SIF values are different.
Model Input listing - "TEE" sub-report in AutoPIPE
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