×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• 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.

#### Jobs

(OP)
Hello,

I am using the 13the Edition of AISC Manual and my question is about combined loading. For round and rectangular HSS, the combination equation is given in AISC Specification Section H3.2.

[Pr/Pc + Mr/Mc]+[Vr/Vc + Tr/Tc]^2 <= 1.0

For bolts, the combination equation is given in AISC Specification Section J3.7. This equation is an approximation of the elliptical curve as per the following equation.

[Pr/Pc]^2 + [Vr/Vc]^2 <= 1.0

What is the reason for squaring the axial forces in the bolt combination equation and not squaring for the round/rectangular HSS combination equation?
Also, which combination equation should be used for combined loading on plates, solid bars and welds?

Regards,
Su

### RE: Combined loading on HSS, bolts, plates, solid bars and welds

(OP)
Hi again, can anyone shed some light on this topic?

### RE: Combined loading on HSS, bolts, plates, solid bars and welds

Take a look at the commentary for J3.7. The test data very much supports this elliptical failure curve. The research papers that derive this should be referenced (I would hope) in the commentary.

For members subject to combined stress, the interaction is likely a lot more complex. Axial stresses interact with flexural stresses which warrant a little extra conservatism in this equation. There is some discussion in the commentary as well. But, it is not as robust as I would like. I used to have a copy of the SSRC guide to stability. I imagine they discuss this in a bit more detail. But, I don't have access to it anymore to verify what it says.

### RE: Combined loading on HSS, bolts, plates, solid bars and welds

(OP)
Thank you for sharing this information!

#### 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.

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:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!