Bracing example...
Bracing example...
(OP)
I have been reading/researching about wall bracing as I have not dealt with it much. I think I am starting to understand the concept and solutions when it comes to a garage wall but how would you brace the upper portion of the attached image? The whole wall is basically windows and I don't think there is enough space to install shear panels. What would some other options be? This is not an actual project just something I saw and was wondering how it would be done. Thanks.






RE: Bracing example...
BA
RE: Bracing example...
Under the IRC, there is a concept of "braced wall lines" that are required. You should review the applicable code and educate yourself on the requirements there.
Typically many of the perimeter walls and the interior walls can all be utilized as braced wall lines to achieve the empirical lateral stiffness that you need.
This is also found in section 2308 of the IBC.
RE: Bracing example...
RE: Bracing example...
BA
RE: Bracing example...
RE: Bracing example...
One thing you might want to look into is an APA document on portal frames or you might want to take a look at some of the Simpson options shear walls, strong walls etc... I believe they even make a pre-manufactured steel moment frame. I don't know if any of these will work in your instance.... but they are worth the look.
RE: Bracing example...
Although the prescriptive bracing requirements have been in the code for over a decade, just now am I starting to see the majority of code officials question the bracing amounts.
RE: Bracing example...
RE: Bracing example...
While we are on topic (allow me to hijack!).
One thing I don't understand and have a problem with all the time: # of braced wall lines adjustment factor in the wind tables (Table R602.10.1.2(1) http://publicecodes.cyberregs.com/icod/irc/2009/ic...). If anyone can give a rational explanation of this one I would love to hear it (it has been in each of the 2006-2012 codes and I don't have a commentary to reference). I play the devils advocate with myself in this game all the time just to see how bad it can get sometimes. I have found that if I put in more walls (up to 5) then I actually have more bracing in each wall then if I took out all of them and only used 2 making it possible to have 2-3x as much bracing required just because I added more wall lines as each wall adds up. I understand that stiffness attracts a load and sometimes a flexible diaphragm is not always a true conclusion in wood structures but the 1.6 multiplier is a stiff penalty to pay. What gives!
______________
MAP
RE: Bracing example...
RE: Bracing example...
RE: Bracing example...
RE: Bracing example...
In the plan you provided, there is 11'9" between the north wall and the interior wall - you need 2.2625' (interpolated) wall bracing in the the North wall. (assuming no modification factors and a 90 mph wind speed). There are three wall however and you need to multiply by 1.30 for a total of 2.94' bracing (see my previous post rant). To achieve this I would propose 6:1 portal frame at the two outside windows. You need 1'-6" for each these so the windows need to be modified. Alternate is to use a stacked shear brace like i-level or strong tie where you can get a 12" wide manufactured panel and can count for up to 4' for each unit. both scenarios require modifying the window arrangement. The manufactured panels will cost real $$ which has not been figured by anyone into the budget.
If you choose to ignore the interior wall then the wall spacing is 24'-11 and the wall bracing amount goes up to 7.75' for each of the north and south wall. Thus you must use the manufactured panel or eliminate windows or some sort of other device.
Alternately you can use an engineered diaphragm and shear wall system to try to ignore the North wall altogether. You may be able to find some lateral stability in the lower roof as well.
______________
MAP
RE: Bracing example...
If there wasn't 11'-8" to the interior wall...say 6'-0" or less, you could easily cantilever the diaphragm and transfer the load to the interior wall.
Without removing windows, or reducing window sizes, in this situation, without using full height timbers or steel. One could justify a full height 6x or glulam that is braced at the first story diaphragm. You would then need to design the 6x or glulam as a cantilever braced at the first story. You would have to transfer that force through the plates at that point. The other option is steel frames, and people in residential don't like that unless you are talking very expensive homes.