INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

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.

Jobs

Roof Diaphragm not analysing

Roof Diaphragm not analysing

(OP)
Hi all,

I've created a really simple model, as per the attached picture below. It has gravity and lateral frames and standard loadings. Nothing groundbreaking! I need the roof diaphragm to model as pseudo rigid however in order to get RAM to analyze the frame at all with this type of roof diaphragm I have to fix every single connection. (XXX - XXX everywhere!) This is incorrect as I need only the major axis to be fixed and torsional fixity. (XOX - XOX.) When I set this type of fixity though I get error messages about local instability at all the joints.

Another oddity which I have noticed, if I set the diaphragm to non rigid it doesn't like the lateral load cases (wind, seismic and notional)...

Does anyone know what is going on and how I can get the model to analyze as I want?!

RE: Roof Diaphragm not analysing

Are you getting significant weak axis bending that you don't want? I don't see an issue with the fully fixed assumption unless you are getting forces that don't make sense.

When you choose a pseudo-flexible case, you need to have frame numbers assigned so you can assign the proper percentage of the lateral load. If you can, try modeling the diaphragm as semi-rigid. this Link and this Link may help you with that. The semi-rigid actually meshes a diaphragm which should help with stability of the model.

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!


Resources


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