Using interior load bearing walls as shear walls 1

[Berniedog]

How do you get the diaphragm load to the top of the corridor wall? Top of corridor truss bearing is 10'-0". The ridge of the roof is 23'-5" high. The the heel height of the trusses at the corridor wall is about 13'-5" tall. How does the load in the roof diaphragm get to the top of the shear wall at 10'-0"?

 

[jayrod12]

Vertical bracing on the webs.

 

[KootK]

How does the load in the roof diaphragm get to the top of the shear wall at 10'-0"?

Dubiously in most cases. In jurisdictions where they are very conscious of lateral design, they'll sometimes build shear wall panels to fit between the trusses, essentially turning the end of the truss into shear wall up to the roof deck. As you can imagine, builders love this.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Berniedog]

KootK Bring it.

 

[jdgengineer]

We specify either the much loved shearwall elements as described by Kootk or the truss manufacturer provides diagonal truss blocks between the roof trusses to take the shear.

 

[KootK]

KootK Bring it.

Do you want more info about this? I'm heading out to re-write the PE exam that I already passed a decade ago. I can post again on Sat. Alternately, if jd is feeling extra helpful...

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Berniedog]

jdgengineer. I am not familiar with diagonal truss blocks between the trusses. What do they look like?
KootK. Yes please share some information.

 

[XR250]

Do a top bearing truss and bring the corridor wall all the way up - another thing builders love. Basically builders un-love anything to do with lateral stability (at least in my area)

 

[KootK]

And let's not kid ourselves: the real diaphragm is usually the ceiling drywall anyhow.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

I did not want to go there....

 

[KootK]

And on the seventh day, the Lord said "let there be discontinuous and unreliably fastened gypsum products." And it was good.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

 

[jdgengineer]

Berniedog see attached. This was from truss submittal to us. Our drawings typically show mini plywood shearwalls in between trusses (this is shown in Terry Malone's book), but often times the truss guys like to substitute with this. It essentially becomes mini braced frames between trusses.

 

[Berniedog]

jdgengineer
Thanks for the sketch. Does this frame attach to the end of each truss? How do they attach it? Or does it go in between the vertical legs (webs) of the truss?

 

[KootK]

jd's system is just what I was getting at. Usually they go between the trusses (1-10-8 dim). At 10' tall, it'll get a litte awkward. As a former truss guy, I can't help but look at these things and see new opportunities for product (sketch below). It's basically a permutation of XR250's detail.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Another option is to sheath the truss verts like wall studs. You can have a 2x ledger recess built into the top and bottom of the truss if desired. At mid height, you'd need blocking or to rely on unblocked capacity values.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[hokie66]

If you would stop using those temporary shingles, and stop wasting all that plywood on the roof, you could afford a decent diaphragm at ceiling level, which is where the forces go anyway...thanks, KootK.

 

[KootK]

Yeah, I had my little Hokie homunculus sitting on my shoulder when I wrote that. What does a typical AU sloped residential roof layup look like anyhow? Vegemite, crushed beer cans, and koala fur?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[hokie66]

Timber trusses just like yours. Then battens, spaced for either roof tiles (concrete or clay) or metal roofing. No sheathing. Various schemes of insulation.

 

[KootK]

Thanks for that. So is the batten system assumed to act as a nominal diaphragm so as to be able to brace the truss top chords?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.