06g. Using load case displacement as a new starting point for analysis in AutoPIPE?

Applies To
Area: Modeling
Date Logged
& Current Version
March 2020


Piping is modeled per layout drawings, after applying a number of operating conditions, user is requesting procedure to use an particular operating load case's deformed state as the starting point of an analysis.

How to model this scenario?


Let us consider the fundamentals of a Non-Linear Analysis. AutoPIPE applies operating conditions as directed by the "Base load cases for nonlinear analysis" setting mentioned in Analysis Summary sub-report . Each load is applied one at a time to the model in its current initial displaced configuration, the program calculates the displacement, forces, moments, stresses, etc.. based on degrees of freedom to move to a new initial displaced position. Then the next load case in the sequence is then applied to the new initial displaced position again performing said calculations. Once the analysis has been completed, results are calculated based on combination settings. 

Summary: Calculate the delta displacement due to desire operating condition and make it the starting point for analysis for new operating conditions and model settings to be applied..

1. Model the original piping per layout drawings (operating condition #1).

2. Insert supports / soil properties as needed.

3. Analyze system. 

4. Open Point tab on the input grids, copy the entire grid to Excel. Call this the initial installed location (see global X,Y, & Z coordinates).

5. Open Results Grids, display operating condition only, and copy grid information to Excel

Remove all Excel  lines that do not correspond with input grids (ex. intermediate soil points. A00 +1, A00+2, A02N+1, ect...)

Note: AutoPIPE does not report displacement of an Elbow TIP point, therefore decide if elbow displacement is based on Near or Far point. Then remove all non-corresponding lines. In this example, Near point was used as elbow TIP displacement. 

6. Using Excel, calculate new global coordinate based on original location and applied operating condition (add displacements to original global coordinate). 

7. Save original model. Then use File> Save As> AutoPIPE model (*.DAT), save to a new name.

8. Highlight new calculated global coordinates in Excel, and copy back into AutoPIPE's point tab grid

9. Update General Model settings, operating conditions, and other items as needed

10, Insert supports / soil data as needed.

11. Run analysis.

Note: Recall that AutoPIPE considers that the piping layout at the start of the analysis has been installed as if no stresses are in the pipe before load cases are applied (gravity, pressure, temperature, etc..). 

See Also

Modeling approches

Bentley AutoPIPE