| Applies To | |
| Product(s): | AutoPIPE |
| Version(s): | ALL; |
| Area: | Modeling |
| Date Logged & Current Version | July 2020 12.03.00.17 |
Problem:
How to model node point shared by more than 1 model?
Another words, how to transfer Forces and Moments at 1 node point that is shared between models?
Example: Node point C03 is shared between Model #1 and Model #2
What needs to be done at the shared node point (ex. C03) in each model so analyze results of individual models matches that of a total combined model 1&2.
Solution:
Instead of modeling to a run Node point (ex. C03) shared by both models, suggest to model pipping to an anchor location shared in both models, and provide both model results to the structural people to correctly design the anchor.
Recommend to not use a typical piping run point, flange junction, branch connection, valve, etc.. as shared point between 2 models. One cannot just take the forces and moments results from a model, insert them into the next model, and assume that analysis results would be correct.
The most important aspect many engineers forget about is the stiffness of the adjoining piping systems. In some rare cases it maybe simple to consider adjoining model stiffness, but for most, correctly representing piping stiffnesses from another model file is very complicated. Furthermore, remember from your AutoPIPE advance training, modal analysis results must exist before performing a dynamic analysis. A modal analysis calculates the natural frequencies and mode shapes. These calculation considers the total mass and Mass Degrees of Freedom for every node point in the connected piping arrangement. As of July 2020, Modal analysis cannot be analyzed across multiple model files.
Test it
Perform the following test to confirm results across multiple models that share one or more node points.
1. Create a single model with complete piping arrangement.
2. Analyze both Static and Dynamic loads, record complete model input listing and output report.
3. Separate complete model into multiple individual models. For each node point shared between models add user defined Forces & Moments, flexible anchor, etc. to correctly represent the loads and stiffness from the adjoining models.
4. Analyze both Static and Dynamic loads, record complete model input listing and output report.for all individual models
5. Compare results in step 4 to results in step 2, they should match 100%.
If not, go back to step 3 and consider modifications to loads and stiffness values that were added. Repeat step 4 and 5.
Note, in the author's experience, these results have never been 100% exactly the same as the original combined model.