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i get instabilities in my very simple RISA 3D model. Need help. URGENT 1

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Johnny pap

Structural
Nov 18, 2019
5
CA
No pin-pin problem. I checked everything I could.
I am looking for someone who can review my model and help resolve the problem.

 
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Remember that every joint needs one degree of freedom fixed or the joint will rotate/translate in space.

Mike McCann, PE, SE (WA, HI)


 
When you run your model and get the instability warning click "Yes" on the popup for "Unstable Model" then look at your joint reactions, wherever the word "Locked" is listed is where you need to modify the connections/supports.
 
I attached my RISA file.
I am not new in Rise, I checked all basic stuff, pin-pin, joint coordinates - everything seems great.
There are twu parallel beams with everything the same, and errors on only one of them
 
Two things you should do to correct some minor modeling issues in your file:
1) Go to the Global Model Settings - Solution. Click the Advanced button and change the merge tolerance from 0.005 inches to 0.12 in.
2) Run a "Full Model Merge"

You've got a number of joints that are within 0.12" of members, but not within 0.005". Too difficult to see, of course.

Note: if you're afraid of this happening in the future, you can view your structure color code based on "Phys Segment". This will show a color change for a member anytime it picks up a node along it's length.
 
Josh, Thanks a lot. You save my day and much more then this.
 
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