×
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

Connection Eccentricity
4

Connection Eccentricity

Connection Eccentricity

(OP)
When designing connections like the attached. Do you consider the eccentricity of the load to the bolts? If slip critical, I can see ignoring the eccentricity. If not slip critical do you consider the eccentricity to be bL-e2, or something other than that? to generate a moment to combine with the shear?



-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Connection Eccentricity

Yes. Connection eccentricity is to be considered for double angle connection welded to the support. For all bolted double angle connections, it can be ignored unless the value of bl (also referred to as "a" in AISC 15th edition) exceed 3" or if you're using more than one row of bolts. Refer to Page 10-9 of the 15th edition manual for some discussions.

RE: Connection Eccentricity

(OP)
Thanks slick... does it make any difference if your fasteners are slip critical?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Connection Eccentricity

I check it. For a connection of that scale it doesn’t make much difference in my experience. Two close bolts and it can make a real difference.

RE: Connection Eccentricity

I mostly use welded cleats, but the same logic applies. I don't normally explicitly check it, For shear cleats unless something is out of the ordinary then I just pull the cleat chart and go. Around here a common rule of thumb is to simply use the first significant figure of the beam depth as the number of bolts. So a ~300mm beam gets 3 bolt. M20 is standard.


On an upcoming project with high point loads I'm retrofitting addition joists. I'm using long angle cleats to minimise site welding or member coping. I've had to choose a significantly 33% deeper section to make the connection work with the eccentricities involved.

Like Tomfh said two close bolts can make a big difference which is what I have if I use a small joist.

RE: Connection Eccentricity

That would depend on the length of your web-framing leg. According to AISC for simple shear connections that are not a shear tab, bolt eccentricity can be ignored if the distance of your bolt line to the face of the supporting member is less than 3 inches.

RE: Connection Eccentricity

AISC 10-33

RE: Connection Eccentricity

Quote (dik)

does it make any difference if your fasteners are slip critical?

I don't believe so. That, based on two observations:

1) As far I know, bolt slip is not one of the mechanisms of connection flexibility that we're banking on when we ignore the eccentricity.

2) The eccentricity tends to tax the shear resistance mechanism of the bolts (vector sum jazz). In the case of bearing bolts, that punishes bolt shear etc. In the case of slip critical bolts, that punishes the friction relied upon at the faying surface. Either way, it punishes something.

RE: Connection Eccentricity

(OP)
Thanks, Gentlemen... I'll include the eccentricity into the SMath program... I check a lot of of light framing framing structures and I can often get by with two 5/8" dia A325s.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

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