AISC 2016. HSS-HSS Moment Connections. In-Plane Moment Capacity

The 2010 version of the AISC spec gives joint strengths for HSS-HSS moments connections in Table K3.2. It presents capacities for both in-plane and out-of-plane bending. This is all in line with CIDECT and the Eurocodes.

The 2016 version gives the joint strengths in Table K4.2. In this table in-plane moment capacities have been removed, leaving only out-of-plane capacities.

Presumably this is to imply that HSS-HSS joints no longer have an in-plane moment capacity? In which case how do you design a vierendeel using HSS members?

I put my question to ‘Ask AISC’ but I didn’t receive a response.

I expect I am overlooking something, or it has been moved to a different place in the document and I have missed it. So what is the current situation with in-plane bending capacity of HSS-HSS joints?

Ussuri…as long as the unity equations K4-8 or K4-9 are satisfied with ANY combination of loadings, it is acceptable. Look at the note in the middle box of Table K4.2

Morning Ron. thanks for that.

In equations K4-8 and K4-9, there are terms for both the in-plane and out-of-plane strength.

Mn-op is given by equation K4-7

Where is the expression for Mn-ip? I cannot seem to find it.

Ussuri…I interpret this as the limit state is the same for either condition.

K4.2 states the limit state here is chord distortional failure (equation K4-7), The commentary to K4 also states the chord distortional failure mode is only applicable to T joints with out-of-plane moments.

Do you think that because in-plane moment capacity is usually higher than out of plane moment capacity the AISC intent is to use the lower for both? If so this would be very conservative.

although I am unconvinced it would be. I sort of looks like part of the table has been missed out.

I agree. They have created a question that shouldn’t have to be. They could have covered it in the commentary or in an errata. I wish AISC would respond to your inquiry

I checked the errata’s, not there. I guess people will default back to the 2010 version.

I just read an article in Modern Steel Construction where they describe the reasons for reducing the tables in the latest spec.

It’s called “Connection Consistency” by Carlo Lini. You can find the article here: Connection Consistency


Aha, now that is something more useful. Thanks JAE.

I figured JAE would come to our rescue at some point! :grinning:


The Steel Tube Institute has also put together some tables that show the relationship between the 14th ed and the 15th ed (that is to say, which parts of chapter J are applicable to the limit states that had been found in chapter K previously). These can be found here:


Thanks for the info.


@dauwerda…helpful info! Thanks for posting and welcome!!

I nominate dauwerda for the next round! Raise ‘em high mates!

I’ll drink to that… don’t tell dauwerda that if held down on the floor, by a sufficient number, I drink to almost anything…



Thank you very much.

Cheers :beers:, I’ll take a Crown and Ginger.
And thanks for the welcome, as well as all of the valuable info I have gleaned from you guys over the years over at ET.