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| Applies To | | |
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| Product(s): | AutoPIPE, | |
| Version(s): | 2004, XM, & V8i | |
| Environment: | N/A | |
| Area: | Error | |
| Subarea: | | |
| Original Author: | Bentley Technical Support Group | |
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Problem:
AutoPIPE: E801-1: Unstable System
When running an anlysis the following occurs:
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Error
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E801-1: FATAL ERROR : Unstable system. Need support at node XXX Dir XX
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OK
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Why and how to fix it?
TR Number: None
Product: AutoPIPE
Version: n/a
Area: General, analysis
Problem ID#: 75241
Answer:
There are many issues that can cause an unstable system. Insufficient supports, not enough guides for wind or earthquake loading, insufficient soil stiffness in the vertical direction for soil problems. Evaluate your support arrangement for your particular loading conditions to see where the instability lies.
Please see the following AutoPIPE help section:
Help > Contents> Contents Tab> Bentley AutoPIPE> Frequently Asked Questions> FAQ document> FAQ #19.
In addition, Please see the following AutoPIPE help section:
Help > Contents> Search Tab> enter "E801" (include the quotes), press List Topics button, double click on the selected topic from the list provided to see more information.
Again, there could be numerous reasons for the "Error "E801-1: FATAL ERROR: Unstable System" message to appear while running a stress analysis, see the following for possible cause and fixes:
Scenario #1
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After importing in the frame model through Pipelink. Error "E801-1: FATAL ERROR: Unstable System. Need support at node XX" is encountered. The AutoPIPE model (without the frame model) runs with no issues. I'm unsure why AutoPIPE would think the frame model is unsupported when the frame model runs with no problems in STAAD.
FIX:
While reviewing the AutoPIPE model, multiple imported beams were found to have their ends released in all direction, (i.e. on a beam dialog screen is the following option "End Releases: End-I/J Axial (translation), Y-Y and Z-Z".
Therefore the beams were able to freely rotate. AutoPIPE requires that all components are restrained to some small degree in at least one direction.
Checked one box for Axial (translation), Y-Y or Z-Z for all beams.
Note: The STAAD model failed when loads were applied, it was also fixed.
Scenario #2
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Using copy / paste command to create a 10' x 10' grid of beams over 100' x100' area. when running analysis the message appeared.
Fix:
When using copy / paste command, only the initial pasted to point is actually connected. All other connections need to be manually connected. Every intersection across the 100 x 100 ' area needed t be correctly connected.
Scenario #3
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Similar to scenario #1, after importing in the frame model through Pipelink. Error "E801-1: FATAL ERROR: Unstable System. Need support at node XX" is encountered. The AutoPIPE model (without the frame model) runs with no issues. The model appears to be all correct and all the beam are were found to be all connected.
Fix:
1. Go to Modify – Properties of Beam Section.
2. Select Section ID 2 (UA90x90x8)
3. Toggle from Standard to Non Standard Section type
4. Do not alter any properties, just click Apply and OK.
Now the model is OK.
The development team is looking into this issue and hope to have it resolve in AutoPIPE 9.6 and higher.
Scenario #4
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Back to back expansion joints where Torsional stiffness = 0.00.
Fix:
All AutoPIPE components must be connected to an object (i.e. anchor) to resist being rotated freely in any one of the 6 axis. In this case the expansion joint may be connected to an anchor through some piping but due to the "Torsional stiffness" = 0.00 the piping between the expansion joints would freely spin. To stop the warning from appearing, set Torsional stiffness = +ve value >0 (ex. 0.01).
See Also
Bentley AutoPIPE
External Links
Bentley Technical Support KnowledgeBase
Bentley LEARN Server
Comments or Corrections?
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