| Applies To | |||
| Product(s): | AutoPIPE, | ||
| Version(s): | All | ||
| Area: | Hanger Selection | ||
| Original Author: | Bentley Technical Support Group |
Problem:
Why is that there is a big discrepancy between the AutoPIPE Hanger Analysis reported (5.652 mm) value and the Static Analysis results (5.97mm) ?
Solution:
Suggest reviewing how spring hangers are selected from AutoPIPE's online help shown at the of the previous WIKI page .
Note that the Spring Hanger Analysis module selected the first spring with the longest range and highest spring that satisfies the conditions of the analysis for thermal load case(s) movement only.
After running a hanger selection, AutoPIPE automatically updates the undesign spring supports with the selected hanger (Variable Spring, Constant Spring, or Rigid Support) values from the report. The AutoPIPE model is now ready for Static and Dynamic analysis where all the configured load cases in the model are applied (i.e. Gravity, Temp, Press, Wind, Earth, etc..).
To answer the question, can the values of thermal displacement on the hanger selection report differ from that of the actual analysis results? answer = YES, the thermal movement for the Spring Hanger report (i.e. 5.62 mm) may differ from that of the Static / Dynamic Analysis results (i.e. GT3P3E1(4)). This is expected behavior for any undesign spring hanger (i.e Variable or Constant).
Consider manually checking the Spring Hanger selection and results by actually performing each step of the procedure outlined in AutoPIPE help section:
Help > Contents> Contents Tab> Reference Information> Code Compliance Calculations> Hanger Selection Procedure> Hot / Cold Load Design Hanger Selection Procedure
Note: Additional tips for models where all anchor releases are used:
1. Uncheck hanger releases in all directions except for Y direction for all anchors in the model
2. Perform the Hanger Selection and review the report
3. For manual gravity load (Hot load) calculations, set all anchors to Flexible and only change the stiffness in the Y direction to a very small value or 0.0 (this is what Hanger selection would do for Gravity loads analysis). Set all hangers to bi-directional v-stops, analyze the model and compare the v-stop reactions with Hot load in Hanger report
4. For Thermal movements, set all anchors to Rigid (including the Y direction flexibility changed to 0.0 in step 3 above for gravity. Set gaps for all v-stops to high values in both directions. Perform analysis, and compare thermal case support displacements (actually pipe displacement values) with the Thermal Movement reported under Hanger Selection report