×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

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

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

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

(OP)
No pin-pin problem. I checked everything I could.
I am looking for someone who can review my model and help resolve the problem.

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

You have to post / attach your model file first.....

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

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

Mike McCann, PE, SE (WA, HI)


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

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.

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

(OP)
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

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

No file attached...

Mike McCann, PE, SE (WA, HI)


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

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.

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

(OP)
Josh, Thanks a lot. You save my day and much more then this.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close