×
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

Steel connection - help me understand
3

Steel connection - help me understand

Steel connection - help me understand

(OP)
I was inspired for this from looking at other thread.

Im really confused as far as steel connection goes and how is it considered for design/in the model.



MODEL 1: I understand this is a moment connection between a column and a beam. Since there is a moment, we have tension force in bolts.

MODEL 2: this is supposed to be a pinned connection? Is there any tension in bolts there since there are no moment? I mean there will still be a rotation around columns flange that wants to tear a bolt apart, isnt it?

Any ebook, article about things like this, from where Id be able to learn?

regards

RE: Steel connection - help me understand

I would consider both connections to be pinned.

RE: Steel connection - help me understand

(OP)
But how do you design bolts then? Based on what forces?

RE: Steel connection - help me understand

I agree with homie, it's pinned.

You ask what are the bolt forces. You need to show how it will be loaded.

RE: Steel connection - help me understand

That type connection normally just resists uplift. So all the bolts are assumed to be in tension. Used in post and beam construction, or braced frame construction, not in rigid frames.

RE: Steel connection - help me understand

(OP)
LOAD:



I wasnt expecting that... interesting...

I suspect you design bolts on shear forces (if there is a axial load in beam), but im really wondering is there any tension in bolts since the end of a beam is trying to rotate upwards (around colums flange)? If yes, then how do you get this forces if there is no moment (pinned connection not moment)?

RE: Steel connection - help me understand

A couple things:

Most would consider them both to be pinned connections. Model 2 for obvious reasons. Model 1 - because the bolts are inside of the flanges and the members would need to rotate A LOT in order for such tension to develop. Most likely the building would be braced some other way and that much rotation would not occur. If the member end plates were longer and the bolts were positioned outboard of the flanges this would be considered a moment connection.

The loading case that wold result in tension is likely to occur when this joint is at the leeward wind side. Buildings like this will often have a lightweight roof.

RE: Steel connection - help me understand

Quote (mats12)

but im really wondering is there any tension in bolts since the end of a beam is trying to rotate upwards (around colums flange)? If yes, then how do you get this forces if there is no moment (pinned connection not moment)?

I think that your instincts here are spot on. Both connections will transfer some moment whether the designer intended it or not. As such, the bolts will see some tension very much as you proposed in your sketches. Two things that you'll have working in your favor if you considered this a pin connection include:

1) Transverse bending flexibility in the beam flange.

2) The beam will generally tend to be stiffer, and rotate less at the support, if it is designed assuming a pin connection.

Really, the bolts being close to the compression flange of the column serve to increase the tension on the bolts. Same rotation tendency but a smaller lever arm to the bolt.

So why do we ignore these bolt tensions in practice?

- Structural engineering's a rough science.
- Bad things don't seem to happen.
- Reasons #1 and #2 above.
- You could probably yield the bolts in tension and retain uplift capacity.
- Shear demand on the bolts will generally be very small.

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.

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