Balcony rigid diaphragm design 1

[Adamian]

I am designing a rectangular balcony structure( see attached pdf plan), that is attached to the existing house on one side and is supported with two 6x6 wood columns on the far side. Can the rigid horizontal diaphragm be designed so knee braces are not required for the far end latteral support?
Thanks.

 

[Adamian]

here is a plan view

 

[msquared48]

The diagonal strapping and blocking is commonly done for decks to eliminate knee braces.

The only extra thing needed is to tie the two corners of the deck that are next to the house back to the floor structure/diaphragm of the house with metal straps.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Adamian]

thank you!
I think on the East side an MST36 will be easy to install.
On the right side I may use a different tie with a bolt.

 

[msquared48]

That tie with just a bolt will be a problem. You really need to open up a small portion of the interior ceiling of the residence at that location and install a strap that ties the edge member of the deck through the wall to the floor joists beyond. You can install the strap on either the side or bottom of the members, whatever is convenient. I assume the floor joist you attach to issufficiently nailed to the floor sheathing to transfer the load to the diaphragm.

Not knowing the exact framing, there may be other alternatives, but just a bolt into a ledger situation is not goint to accomplish what you need to do. Your tension/compression forces could be a kip or so.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Adamian]

Balcony structure W=4155LBS
Cs=0.274
V=0.274*4155=1139LBS
Mov=V*L/2=1139*12/2=6834ft-lb
T/C=6834/18=398LBS

Simpson's LLT19 LA RR25818
allowable load is 825*0.75=618.75LBS

If this is correct, do you think I can use LLT19 with 1/2" bolt through existing 4x12 or 2-2x12 2nd floor framing?
Thank you very much!

 

[msquared48]

By code, you cannot put any member in cross grain bending to resist tension forces , which, if the 4X12 or 2-2X12's are the existing rim joists, is exactly what you would be doing. You have to get to the joists in the interior of the residence.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask