×
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!
  • Students Click Here

*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

Jobs

Staad Pro's curve member function

Staad Pro's curve member function

Staad Pro's curve member function

(OP)
I need to model a curved truss.
I tried by using a single simple beam, a simple 2D frame. But I failed to get reasonable results. It is a 2D frame, but it gives me 3D results, and some totally unreasonable results.

I wonder it is something wrong with my model or the curve member function is just not stable yet. I am using Staad Pro v8i.

I appreciate any response!

RE: Staad Pro's curve member function

STAAD is a tricky thing.  It's hard to say without seeing the model itself.  However, if you are modeling a curved truss, I think you need to be in space, not plane for your model.  The truss is going to deflect in all 3 directions due to the curvature.  I haven't used the curve member function, so I'm no help there.

RE: Staad Pro's curve member function

If you can, model the truss as straight segments....as long as it reasonably approximates the curved truss.  

RE: Staad Pro's curve member function

(OP)
Thanks replies above!
BridgeEI, I thank you are right. It is tricky for curved members. When you say Staad is tricky, it is in general or just for curved member? I am curious.

ToadJones,
My current model is using straight lines to approximate the curved sections. Over 45" span, the center offset from the curve is 1". Is that close enough? I was asked to add more nodes to make them closer to the curved. I want to add one more node, instead of 3 more nodes which I was asked to do.

Thanks!

RE: Staad Pro's curve member function

In general and for curved members.  If you do use the curved member specification, only self weight & uniformly distributed loads can be specified for the member.  See the manual on this.  Run a statics check to make sure you aren't losing any load.  My first impression is that you may be using pinned supports, essentially allowing the truss to rotate until it reaches equilibrium.  Another thought, would be applying loads that the specification doesn't accept (concentrated loads on the curved member) or if you specified the member as "truss" and how the loads are applied to it.  Again, its hard to see w/o the input.

RE: Staad Pro's curve member function

(OP)
BridgeEI,
Thanks very much. I used pinned supports, maybe that is the reason it resulted in unreasonable results.
I think I have to give up the try. I need to model curved members using small straight segements.

Thanks very much!

Lenew

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