Residential bracing methods 1

[AETX]

Hi everyone i have a question regarding a single family home two stories bracing. Is it acceptable to mix bracing methods (let in bracing and structural sheathing) in the same braced wall ? I.e at the corner you have sheathing and after down the wall line you have several let in bracing ? Alt wind speed is 150 mph 140 MPH (edited typo) Thank you.

 

[phamENG]

At 150mph you can't use braced wall design at all.

The wind provisions of this code shall not apply to the design of buildings where wind design is required in accordance with Figure R301.2.1.1, or where the ultimate design wind speed, V[sub]ult[/sub], in Figure R301.2(2) equals or exceeds 140 miles per hour (225 kph) in a special wind region.

It needs to be designed using engineering principles - shear walls, diaphragms, etc.

 

[AETX]

Sorry edited typo. 140 MPH.

 

[phamENG]

Doesn't change the fact that, unless this house is in Nantucket, it has to be engineered. 140mph still "equals or exceeds 140 miles per hour."

 

[XR250]

I don't see how let-in bracing actually does much at all. You get maybe (3)10d at each end of a steeply angle brace?

 

[Aesur]

I don't see how let-in bracing actually does much at all.

I too have always questioned that in the IRC. This is why I just provide engineered designs instead of IRC for most residential projects, granted most we do require IBC anyways.
I suspect that what really happens is the gyp finishes does more work than the let-in bracing.

 

[XR250]

I suspect that what really happens is the gyp finishes does more work than the let-in bracing.

I have similar suspicions

 

[lexpatrie]

That says "in special wind regions" so if they aren't in a special wind region it's possible. Y'all got to read the whole sentence.

 

[phamENG]

And you need to read that section of the code that provides a picture showing every place in the country with wind speeds of 140mph or greater that isn't Nantucket (so, Texas to North Carolina along the coast) as a special wind region requiring wind design. Which is why I added the caveat for Nantucket.

(For total clarity, I'm just using Nantucket as a placeholder the southern shore of Massachusetts.)

 

[ChorasDen]

pham, this begs the question I think, what's so special about Nantucket that it doesn't require design when the surrounding territory does? (caveat, I'm completely unfamiliar with east coast wind regions).

 

[Greenalleycat]

Testing on oldschool cut-in braces in walls here basically confirms that they're so flexible that they do f all
Given that this is a very windy site I would say there is a genuine risk of damage to the house so I would be relying on proper structural systems
I would only be using sheathing or other specifically engineered systems or else you're going to end up with a call back

 

[phamENG]

ChorasDen - I imagine it has something to do with the hurricane models that undergird those maps.

 

[lexpatrie]

Nice.

Except nowhere in the OP does it mention being in a special wind region?

 

[ChorasDen]

I'm with Pham on this one. 140 mph, not sure of location (OP is from Texas, so project could easily be Corpus Cristi or similar). That's not a typical or light-weight wind load, why so much resistance to recommending an engineered solution, or are you complaining that it doesn't fit the code language verbatim?

Lex, is your argument that we should be using let-in bracing for this structure, that's the route that best serves the structure?

We have limited info from the OP (as typically is the case), so we caution best we can based on our understanding of the situation and concerns that we can identify. I think Pham did a good thing with his initial post, it's up to the OP to confirm or identify what requirements are applicable.

 

[AETX]

All. Thanks for your responses.

The question is that i have seen it being built and was just questioning if it is acceptable to mix and match of sheathing and let in bracing in the same wall line and thought to ask you so educate myself of what i see. Not sure if what they have installed is an engineered solution or not just thats what i saw

 

[phamENG]

Except nowhere in the OP does it mention being in a special wind region?

Nor do they need to. The IRC figure is pretty clear that wind design will be required, unless they're in Massachusetts. Though even that might need it, too...the resolution on the image isn't great, and those islands are mighty small...

 

[phamENG]

The question is that i have seen it being built and was just questioning if it is acceptable to mix and match of sheathing and let in bracing in the same wall line

When using the braced wall provisions of the IRC (correctly), it depends. Check out R602.10.4.1 Mixing methods for the rules on mixing types of bracing. But, again, there's nowhere in Texas that you could use IRC braced wall methods with a wind speed of 140mph or greater. And, actually, that map makes it look like they include 130mph along the Gulf and south Atlantic coasts.

 

[lexpatrie]

Whil I get the idea of looking at the "base" IRC for a general question, first, the figure doesn't match the text, unless they've added a BUNCH of special wind regions recently. SWRs tend to be out West or in the mountainous bits of the Appalachians, not the coast.

Second, the specific state code probably torches that language.

It's like looking at the base IBC for special inspections in Wisconsin and Florida, they delete those sections last time I checked. You can happily add them back in for "your" structure, but they aren't strictly required if you don't add them back.

For a residential structure, well, somehow I don't think this "wind design required" hits the way you think it does. Usually its jurisdictiin provided calculation sheets to fill out that arent P.E. stamped, McAllen has "wind design required" and I've not seen a lot of structural engineer sheets for those buildings when they are residential.

To answer the O.P.'s actual question (wow), I don't think there's a prohibition on mixing the various braced wall types. It may not produce equivalent wall deflection between the braced wall panels, but I don't think that's required.