Framing perpendicular to joists at wall connection
Framing perpendicular to joists at wall connection
(OP)
re: steel joists, steel deck diaphragm, concrete walls, moderate to high seismic area
Is there a need for framing perpendicular to steel joists, parallel to the deck, for the first few bays between joists at wall connections? Does the deck try to take a compressive force from the wall? I've seen details with and without this, and am having trouble deciding which is right, or if both are right under different conditions.
Is there a need for framing perpendicular to steel joists, parallel to the deck, for the first few bays between joists at wall connections? Does the deck try to take a compressive force from the wall? I've seen details with and without this, and am having trouble deciding which is right, or if both are right under different conditions.






RE: Framing perpendicular to joists at wall connection
RE: Framing perpendicular to joists at wall connection
We found it generally could, but we still didn't feel comfortable having gage metal laterally bracing heavy walls. Just didn't feel right though.
We have recently used a detail where we lay a C6 over the joists and into the wall (to a clip angle or some other competent connection). The C6 flutes are up. The metal deck then lays over the flutes and you can then weld/screw the deck to the C6 as well as the joists.
Usually we develop the C6 a distance back into the building enough to ensure that the deck-to-C6 connection can take the lateral force. There are a number of variations of C6 spacing along the wall vs. distance into the building but usually the C6's are spaced between 10 to 15 feet and extend into the building 2 to 3 joist spaces.
RE: Framing perpendicular to joists at wall connection
I know you are not allowed to use the deck as the continuous tie when loaded perpendicular to the deck span. For parallel to deck loading, I have never found that you are not allowed to use the deck as the continuous tie (or support reactions from the top of wall) if it can take it. I would create a subdiaphragm using angles connected to the wall then back to the adjacent joists if I was not comfortable with the deck alone taking the load.
FEMA 547 has a little discussion on metal deck bracing walls, I quickly saw something on page 22-16.
http://www.fema.gov/library/viewRecord.do?id=2393
RE: Framing perpendicular to joists at wall connection
JAE, I tend to agree that it seems the deck should be fine, and I've checked it before a while back. I guess it's striking me as I just don't like it even if the numbers work. The perimeter welds will develop the deck strength also, so I'm not too worried about having the extra framign in order to get load into the diaphragm.
RE: Framing perpendicular to joists at wall connection
RE: Framing perpendicular to joists at wall connection
RE: Framing perpendicular to joists at wall connection
RE: Framing perpendicular to joists at wall connection
Using a half joist space adjacent to the wall is also a good idea.
RE: Framing perpendicular to joists at wall connection
RE: Framing perpendicular to joists at wall connection
RE: Framing perpendicular to joists at wall connection
For shorter, thin walls, the deck is likely adequate. When you get into 30ft tall warehouse walls, the outcome may be iffy.
RE: Framing perpendicular to joists at wall connection
RE: Framing perpendicular to joists at wall connection
Also, when the joists frame into the wall, the deck is obviously parallel to the wall. However, no angle or structural piece is provided between the wall and deck, therefore, I believe there is no chord element for the diaphragm. Is this correct? I don't quite buy into the deck being the chord element at the boundary. I can buy the force transfer being from the deck, to the chord element, to joist bearing seat (if less than 1600# or so) and into the wall. If the deck did act as the chord, wouldn't you be relying on the last few connections (arbitrary quantity of fasteners) to deliver the boundary force into the joist?
RE: Framing perpendicular to joists at wall connection
Don't forget that the bond beam, if continuous, can function as a chord or if it is a larger building, the first interior beam or joist could function as the chord. The only trick is how the load gets transfered down to that point and as you said how many fasteners you can count on to make this transfer.
RE: Framing perpendicular to joists at wall connection