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

Tension Rod Bracing

Tension Rod Bracing

Tension Rod Bracing

Does anybody know how to model Tension Only Rod Bracing in RAM?
Please advise.  Thanks

RE: Tension Rod Bracing

Forgive me if this is too obvious, but this has worked for me:
You can just put your tension brace in your model, and make sure when checking the output that the member is indeed in tension.  This approach works with any FEA package.

You need a feel for which way your structure is going to work before running the analysis.


RE: Tension Rod Bracing

Thank you GA.
But my concern is if you model the X-bracing, the rod that is in compression will be assumed to take the load, hence, it reduces the forces in the rest of the bracings.  Those which are in compression should be assumed "inactive" for lateral force redistribution, so that those which are in tension will carry all the lateral loads.
Do you think this make sense?  Please advise.
Thank you for your time.

RE: Tension Rod Bracing

Sorry, lutein, but I wasn't clear.

You should exclude any braces that you "know" might be in compression from your model.  So an x braced bay will only contain one brace, a situation which corresponds to "reality", where your compression brace has already buckled.


RE: Tension Rod Bracing

Trainguy's method is how I have always done this, but you sometimes have to do several trial runs before you end up with the right braces in your model.

Alternatively, you might try this:

Put all of the X-braces into your model, with different nodes at their midpoints and no connection between the braces.  Give both braces a small displacement so that they are no longer straight.  Then do a non-linear analysis.

If all goes well, you might find that the tension brace will straighten out and take the load, while the compression brace will deform further, and take a negligible load.

Note, I have only just thought of this device, have never tried it for myself, and would not be greatly surprised if it bombs out with some message about matrix singularity.  I would be very interested to hear if it works.  If it does, we will call it the Lutein-Austim method  

RE: Tension Rod Bracing

I understood everything up to the words: "You might try this", Austim.

I can't believe someone actually CHOOSES to do a non-linear analysis.

You don't need to respond, I'm just amusing myself...

RE: Tension Rod Bracing

The handout for the 1999 series of RAM seminars titled "Using the Ram Structural System Effectively and Productively" contains RAM Structural System Tip #2, "Tension-Only Members in RAM Frame".  This tip suggests three ways to model your structure.

I believe the tip is also available on the RAM Intl web site which contains a wealth of info re using the Ram software.

I have also found that the RAM technical help staff are very prompt, competent and helpful-either via telephone or email.

Frank Hartzell

Frank Hartzell
Jacobs Engineering
Conshohocken, PA

RE: Tension Rod Bracing

Concerning with tension elements,
I don't know what is RAM but when I use other pro. to analyse structures, I put them to margin of instability as applying the P-delta effect on them. Then they can not sustain any further compression stress.

RE: Tension Rod Bracing

my question might sound silly, but i am new in steel design. Is RAM a steel structure engineering analysis program? Will it account for earthquake load? What other steel structural analysis programs are popular? Mainly dealing with low rise buildings (up to 7-10 story buildings, mainly 2-3 story)..
Your reply will be greatly appreciated...



RE: Tension Rod Bracing


Programs for structural analysis and design include:

Visual Analysis

Many offices in my local area use RAMSteel for gravity design and seismic design of regular low rise simple buildings.  For complex buildings, use RAMSteel for gravity and ETABS or SAP for lateral (dynamic or static).  RISA and Visual Analysis are typically used for small frames/trusses or parts of structures.  This is in California.

RE: Tension Rod Bracing

Thank you all for your kind help and replies.
I have finished the design of the building.
I talked to a gentleman from technical support, and this is what he suggested and I concur:

Model the X bracing in RAM.  Since it's a rod, I need to go to the master steel table, i.e. aisc.tab to add some rod properties in - "ROD0.5XROD      R     0.500  0.250   0.196   0.003068  0.012272  0.020833"  This is a 0.5" dia. rod.  In RAMFrame, I will assign a very small K to the X bracing, like 0.1, so that compression force will not govern and the rod will only be checked against the tensile force.  This is one of the option.  

The other option is to model only 1 side of the X bracing in with small K value, and design them.  And run another design with the other side.  The largest size shall be the design.

Although this may sound troublesome, but I think it's the right way to do it.  Hopefully, the new RAM will accomodate this problem.

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


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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