| Applies To | |||
| Product(s): | AutoPIPE | ||
| Version(s): | 2004, XM, V8i | ||
| Area: | calculations | ||
| Original Author: | Bentley Technical Support Group | ||
| Date Logged & Current Version | May 2015 09.06.02.06 |
Problem:
Comparing the calculation of fa (allowable expansion stress range) for austenictic steel 1.4301 X5CrNi18-10 between hand calculations and AutoPIPE. For room temperature it looks like fc=MAX(Rm/3;f), where as it should be MIN. For higher temperatures we cannot determine the cause.
please comment.
Solution:
Please see the following AutoPIPE help section for calculations used by the program:
Help > Contents> Contents Tab> Reference Information> Code Compliance Calculations> Euro EN 13480> Allowable Stresses
For En13480, from AutoPIPE help, know that AutoPIPE assumes Rmt = Rm during the calculation of the cold design stress, and that the application evaluates f accordingly. Furthermore detailed information such as this is available in AutoPIPE help, such as:
1. AutoPIPE evaluates the hot allowable based on displacement categories.
2. AutoPIPE evaluates the allowable stress at minimum temperature, fc. Again, the program assume that Rmt = Rm, so the design stress below is used:
f' = max (R_p1,0t/1.5,min, (R_mt/3.0, R_p1,0t/1.2) )
f_c = min(R_m/3.0,f' )
3. Note, fc is at a constant ambient temperature, independent of the thermal load case.
4. Confirm hand calculations have the correct Eh and Ec from the results report,. Different values will produce different results between hand calculations and AutoPIPE results.
5. Note, that some differences between hand calculations and AutoPIPE result values will most likely be floating-point or unit conversion errors, but still within 1% accuracy.