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

Rotational stiffness

Rotational stiffness

Rotational stiffness

Hi all,

I'm exploring the steel construction manual 13th edition. But I'm unable to find how I should calculate the rotational stiffness of a connection. Please enlighten me.


RE: Rotational stiffness

Are you referring to a "partially restrained" moment connection?  

I'm not aware of any standard guides that have this. I've always told people to look up the test results data (moment rotation curve) and use that as the basis of their connection stiffness approximation.  

For fully restrained moment connections you can assume that the beams are rigidly connected to the columns.

RE: Rotational stiffness

Well in Eurocode (EN1993-1-8 chapter 6.3) there is a formula to calculate the rotational stiffness of a connection. They also give an upper value for a connection to be nominally pinned and a lower value for a connection to be rigid.

Now I have found those boundaries in AISC specification for struct steel buildings (Ks >= 20EI/L fully restrained, Ks <= 2EI/L simple). But I can't seem to find a way to calculate Ks, which is the secant stiffness of a connection.

I need to calculate the rotational stiffness for moment connections in order to use them in my global analysis. In fact, what I'm trying to do is theorically predict the moment rotation curve you would get from tests, without actually having to perform these tests.

RE: Rotational stiffness

If you are looking for information on non-linear moment rotation curves, you might try the following:
FEMA 356 Prestandard and Commentary for Seismic Rehabilitation of Existing Buildings
UFC 4 23 03 Design of Buildings to Resist Progressive Collapse
ASCE 41-06 Seismic Rehabilitation of Existing Buildings

RE: Rotational stiffness

I agree with wannabeEIT (what kind of a name is that?!).  Those Push-Over and Progressive collapse documents have a good amount of information about moment rotation curves or such for connections.  So, they're probably a good place to start. Unless someone else replies back with a better reference.   

RE: Rotational stiffness

One reference that even gives old DOS software to the purpose is

Stability Design of Semi-Rigid Frames
Chen, Goto, Liew
Wiley Interscience

RE: Rotational stiffness

This isn't referenced in AISC anywhere but I have always treated a connection which able to transfer the minimum of the design action and/or 30% of the member flexural capacity as being a rigid connection for the 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


White Paper - What is Generative Design and Why Do You Need It?
Engineers are being asked to produce more sophisticated designs under a perfect storm of complexity, cost, and change management pressures. Generative design empowers automotive design teams to navigate this storm by employing automation, data re-use and synchronization, and framing design in the context of a full vehicle platform. Download Now
eBook - Simulation-Driven Design with SOLIDWORKS
Simulation-driven design can reduce the time and cost of product development. In this engineering.com eBook, we’ll explore how SOLIDWORKS users can access simulation-driven design through the SOLIDWORKS Simulation suite of analysis tools. Download Now
eBook - Integrating the Engineering Ecosystem
Aras Innovator provides multiple options for integrating data between systems, depending on the scenario. Utilizing the right approach to meet specific business requirements is vital. These needs range from authoring tools, federating data from various and dissimilar databases, and triggering processes and workflows. 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