Rafter Splice?

[ADAMK2310]

How would you design a splice for a cold formed/light guage steel c-stud? This is for a rafter, but this would apply to any beam splice. I have some reservations about it and I wanted to get some other opinions. (Flanges will not be connected.)
Approx. loads: Mmax=18k-in, Vmax=500 lbs
Rafter is 8" CSJ.
How many screws? Screw pattern?

 

[ishvaaag]

Maybe a rigid plate in the web with enough bolts can take the forces; the same can be attempting with welds. However passing the moment force may require some kind of rigidizers or a more detailed analysis to see how the things are going for the web, that may stay more critical than what we can add.

 

[MiketheEngineer]

Typically splice plates are used on the flanges (top and bottom) to hold the moment and web slpices are used to carry any shear. A very basic simple BUT conservative design.

 

[AHaddad1]

Lap the C channels about two feet or whatever makes you feel more comfortable and screw them together, you can screw the flanges together to develope the required moment, you can also screw the channel webs together to develope a rigid continuous member.

 

[diarmud]

NYS residential building code states "Rafters and other structural members, except ceiling joists, shall not be spliced."

It only allows splices in ceiling joists at interior bearing points . . .

Never knew that . . . I think it can be done but I won't ignore the code.

Given that, they show a joist on a load bearing stud with a C section splice minimum 6" long, screwed with a total of 4 screws on each side of the splice.

I'm really unfamilar with this and have not seen it done.

Good luck,
Dermott

 

[AHaddad1]

diarmud,

Proposed Changes dated February 2008

http://www.iccsafe.org/cs/codes/2007-08cycle/ProposedChanges/V2_RB174-213.pdf

See page 52 for Deletion without substitution

Also Figure 804.3.7 (2) was deleted without subsitution.

Thank you for bringing this up, I like to hear and learn more details about this issue concerning NYC Building Code.

Link to the International Code Council

http://www.iccsafe.org/

 

[hokie66]

You cannot moment splice a cold formed section without connecting the flanges. Shear yes, moment no.