×
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

Determining Moment at the Top of a Steel Column

Determining Moment at the Top of a Steel Column

Determining Moment at the Top of a Steel Column

(OP)
Hi All,

Newbie here! I am working on a structural steel beam system to support a cooling tower. Right now I'm on the column loads, more specifically the flexure design using the AISC equation H1-1b.

I know this was probably covered before (tried searching and did not find what I needed), I need to determine the moment at the top of the column (Mrx & Mry) without using software, where the beam connects. This feels so basic, but cannot find what I need. I used a simple statics (Horizontal Wind Load P x Length) but the moment is too high so I need a more specific method. Can the Euler's formula be reworked to determine moment or deflection? Or rework the Moment diagrams on a beam (Table 3-23 AISC)?

The wind load was already calculated and I used the resultant divided by the tributary area of the worst case support.

Any help here is much appreciated. Thank you!

RE: Determining Moment at the Top of a Steel Column

Simple statics usually don't lie. Force times the arm will be your moment. Obviously you need to take the appropriate force (depending on the tributary and number of columns participating in resisting the wind) and multiply it by the appropriate arm (wind resultant to the top of column(s)), but that's the right approach.
If you're willing to provide a sketch, we will have better picture of your problem and likely better answers.

RE: Determining Moment at the Top of a Steel Column

(OP)
Thank you. My traditional statics is very conservative, where since this is a framed member (see diagram below) the top is more rigid than the calc. I was very close, only off by about 10% of the value I needed. I ended up bumping up the HSS tube steel.



Thanks!

RE: Determining Moment at the Top of a Steel Column

If you have a braced frame as shown above, you should not have a moment at the top of the column

RE: Determining Moment at the Top of a Steel Column

In the usual case where the member joints are assumed pinned, I agree with MotorCity. Are you considering your member joints to be fixed? If so, that's a pretty determinate thing and not easily estimated by hand other than say that the braces ought to be the stiffer load path by far.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Determining Moment at the Top of a Steel Column

Agreed with the above comments. Unless you provide a stiff enough connection between col and beam you will not get a fixed condition. And even if, your brace will be stiffer and will take more of the lateral load which will reduce the moment in your joint.
I would model it as pinned at corners and let all the lateral be taken by the bracing. Otherwise you may be under sizing the brace and its connections assuming the joint takes more load than it actually does.

RE: Determining Moment at the Top of a Steel Column

(OP)
Thank you all for the suggestions. Yes I took it as pinned.

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


Resources

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