×
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

Risa 3D - Equipment Anchor Design

Risa 3D - Equipment Anchor Design

Risa 3D - Equipment Anchor Design

(OP)
I am designing an equipment foundation and anchors for a piece of equipment. In Risa 3D, I have located the anchors and drawn a vertical rigid link from center of foundation to top of concrete distance, using a fixed end condition at the node which would be at the center of the foundation. There is a total of 6 anchors. From the top of the vertical rigid links representing the anchor bolts, i have drawn rigid links all to the center of gravity of the equipment where i would add a single nodal load for DL, LL, Wind Load, etc.
My question is, will all the rigid links have fixed ends, creating a completely rigid frame? I plan on using the reactions at the anchor nodes. I have tried pin connections for the rigid links to the center of gravity, but get much larger shear reactions at the anchors, so i believe a completely rigid frame would make more sense. I will transfer the model into Risa Foundation to do the concrete design.

RE: Risa 3D - Equipment Anchor Design

I'd delete the "anchor" rigid links and just apply a pinned boundary condition to the "to-center-of-mass" rigid links. I've actually done this before for this exact situation and it matches hand calcs fairly close. If your BC's are all pinned then that end of the rigid link will have to be fixed-end. Or vice-versa. Fixed BC's and release ends of members. Might want to just experiment and see if there's any difference. Probably will be. Or just do it by hand hah.

RE: Risa 3D - Equipment Anchor Design

I've done it this way before also. One thing to watch out for is overconstraining the model with too many rigid links and fixed conditions. You can end up with some unexpected results due to the high degree of indeterminacy. Like dold suggested, experiment with different boundary conditions until the reactions match what you would expect by hand-calc analysis.

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