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Question about bracing garage wall

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jimtheengineer10

jimtheengineer10

Civil/Environmental
Apr 28, 2012
159
US
A client wants to have a 20' garage door and an 11' garage door on a 32' wall. This leaves 1'-8" on each side of the garage and 1'-8" in the middle. I have used the simpson strong tie wood strong wall portals before but the max opening is 16'-4". Anyone recommend any other options for providing the proper bracing for this scenario? Thank you.
 
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How do you figure 1'-8 each side and 1'-8 in the middle? 32' less (20' + 11') leaves a total of 1'-0" left over. Please clarify.

BA
 
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I don't see the reference to max opening with the Shearwall panels? Are you using the panels as a "portal frame" or just as a shear panel or wall?

Is this residential design and is this a prescriptive panel or are you engineering the thing out? Also what is your seismic zone?

Also: What BAretired says is true... you are missing a lotta wall here. Don't forget that the true rough opening of a typical door is less than the specified size. when you are running so tight with fabricated components then you have to pay attention to this or you are on the phone with the contractor and concrete is already cast with major anchor bolt issues.

______________
MAP
 
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There's a figure (detail drawing) in the IBC but I recall it requires at least 24" shearwall length - it is a good alternative to a Simpson Strong-wall, but you should calculate the shear and overturn to design the sheathing, nailing, anchor bolts, and hold downs.
When the length is less than 24" you usually have Simpson HDU-type hold downs or similar, and with all the multiple studs required, the hold downs become ridiculously close to each other.

Also it frequently becomes impossible to fit in all the required anchor bolts - but I use the hold down bolts for some of the shear. I know this isn't recommended but I have seen real-life construction of all this and it appears to me those bolts can transfer a lot of shear. I have to keep my designs constructible because I do a lot of design for semi-custom and custom homes.

 
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Sounds like you need some cantilevered reinforced concrete, reinforced masonry, or steel columns. Or a steel portal frame.
 
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Can you create a three sided diaphragm with the roof sheathing? It will probably behave that way anyway.

DaveAtkins
 
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I agree with DaveAtkins. If you can get it to work as a 3 sided building, it is much easier. Just make sure you have your roof diaphragm and blocking detailed well.
 
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Sorry about that. The wall is 36' long not 32'. The seismic zone is D.

How would I get it to work as a three sided diaphragm?

Thanks.
 
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How much wall would need to be provided to just construct a regular 2x6 wood stud wall without the bracing? Right now there is 1'-8" of wall on the ends and in the middle. What would the 1'-8" dimension need to be increased to? Thanks.
 
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If I were to look at doing a three sided diaphragm here. I would calculate the deflection at the open face and use shear panels at the open face that will allow this much deflection. Even if it meant using larger shear panels, to strengthen the diaphragm.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
 
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How much wall would need to be provided to just construct a regular 2x6 wood stud wall without the bracing? Right now there is 1'-8" of wall on the ends and in the middle. What would the 1'-8" dimension need to be increased to? Thanks.
 
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You could always extend the concrete stem wall up enough to limit the aspect ratio of a wood stud shear wall to 3.5:1. That's a trick I have used in the past to overcome the Simpson option.

Mike McCann
MMC Engineering

 
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How much wall would need to be provided to just construct a regular 2x6 wood stud wall without the bracing? Right now there is 1'-8" of wall on the ends and in the middle. What would the 1'-8" dimension need to be increased to? Thanks.

Are you saying you don't know how to design shearwalls? If you can't design and provide a 3- sided diaphragm, then you have to design the 3 short walls as a portal frame and use the appropriate detail from the IBC (it is similar to a Simpson Strong-wall but generic).

In other words, you cannot provide a prescriptive, IRC - type shearwall solution (with no calculation) with such short walls. I was suggesting 24" minimum because that what I found was practical.



 
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Not sure if this is relevant, but current construction practice in SoCal is an ~1ft wide galvanized steel pillar on either side of a garage door opening.

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Need help writing a question or understanding a reply? forum1529
 
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aellc, I don't think the owner is going to want to have to worry about shear walls so I am asking how much wall spaced he needs to have between the doors to just build regular stud walls @ 16" o.c.

msquared, the wall are going to be 10'. My width of stud wall is 20" so the length it can be to stay within the 2.5:1 ratio is 50" so my stem wall would have to come up 70". Stem wall (70") + wood stud wall (50") = 120" or 10'. Is this correct?
 
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The ratio is 3.5:1, not 2.5:1.

That means that the maximum height of stud wall is 5'-10". And the height of the concrete stem wall needed would be 4'-2" for a 10 foot wall.

Oh, by the way, you will probably have to nail the *&^%& our of the stud wall.

Mike McCann
MMC Engineering

 
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msquared, how much space is required between doors to just use regular wood stud construction? By nailing the *&^%& out of the stud wall do you mean nailing the sheathing to the studs?
 
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msquared, actually I think I figured it out. The wall would have to be 120" / 3.5 = 34.2" wide minimum. So if I have a 3' wall between the doors it exceeds the 3.5:1 ratio and then it could just be regular wood stud construction.

Is this above correct? Thank you.
 
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I am not a framer, but the rough opening could be 1.5 to 3" wider, depending on the trim and door used, so the stem wall would have to be appropriately higher to accommodate this.

As for the &*()^... yes.

Mike McCann
MMC Engineering

 
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msquared, is the above correct in that if there is 3' between walls regular wood stud construction can be used without having the stem extend up.
 
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