CFS Web Stiffeners at end bearing required when using clips to hang joist from its web? 2

[ProLuke]

Hello!
I am designing a carport using cold-formed steel as the roof joists (1000S350-68 at 40" o.c., spanning 20 feet) that are hanging flush from back-to-back stud sections (1000S250-68 back-to-back spanning 10 feet between posts).

I have used various software (Simpson CFS & AISIWin) that both come up with my roof joists need web stiffeners.

I was planning to hang my roof joists from the back-to-back beam using Clark Dietrich E689 clips (a 1.5" x 4" x 9" clip) that screws into the web of the back-to-back beam and the web of my roof joists.

Do the E689 clips count as web stiffeners, or should I tell them to also add a separate web stiffener with the E series clips? My instinct is that the web stiffeners are to prevent buckling of the web, which I think the E clip will do, but can anyone confirm or refute this and point me to a code reference?

The image above is almost exactly what I want to do, just I'm using back-to-back as the supporting member.

I end up with a total ASD reaction of 1426 lbs on the clip, which the CD E689 has a capacity of 1862 lbs.

--Luke
Texas PE
Structural and Civil Engineering

http://www.framestudio.com

 

[KootK]

I would say that you only need bearing stiffeners if you're actually bearing on something. That, because the idea is to convert a localized bearing stress that would cripple your web near the point of bearing into a smooth delivery of shear through the depth of the web. I would say that your clips already create that smooth delivery of shear through the depth of the web and, therefore, the bearing stiffeners are not needed.

 

[XR250]

Looks like you are going to either cope the webs of your rafters or count on the clips resolving the eccentricity of the connection (which would significantly lower its capacity)
It can be easier to use a boxed section - such as a stud capped with a track for these types of connections.

 

[ProLuke]

Thank you for the replies - KootK your logic makes sense.
XR250 - I would imagine that Clark Dietrich has accounted for this eccentricity to deliver the force as an almost pure shear to the web of the supporting member (that the 9 screws between the clip and joist act as a moment & shear connection to effectively extent the joist 3 inches. Do you know of a reduction in F1 capacity I should be using?
For reference, this is the allowable load pages from Clark Dietrich:

https://www.clarkdietrich.com/sites...s/Catalogs/ClipExpress/ESeries_2021_03_15.pdf

--Luke
Texas PE
Structural and Civil Engineering

http://www.framestudio.com

 

[XR250]

Ahh, did not realize you were using their picture in the post. Maybe it is fine as is. I have seen a lot of sketchy testing and design values for LGS connections so I am always leery.

 

[ProLuke]

Thank you for your replies - if someone reads this later on, I wanted to follow up with what I ended up drawing:
- I found the Clark Dietrich standard detail for E clips says to use a 7" clip for a 10" purlin, and the 7" clip does not have enough capacity.
- I specified a Simpson SJC8.25 that has more capacity and works for my supporting member and loads.
- I am relying on the Simpson SJC that connects to the web to count as a Web Stiffener as required by the joist software, with the idea that the clip is attached directly to the web so the web should not buckle.

Enjoy the numbers out there!

--Luke
Texas PE
Structural and Civil Engineering

http://www.framestudio.com