Transferring shear across demising cmu wall.

[radiocontrolhead]

This might be a stretch, and I haven't exactly worked it out fully in my head or on paper but can CMU block be treated as it would be a wood block to transfer shear across it?

There is a common cmu wall between wood diaphragm that is supported by a ledger on either side. presumably this action is already taking place.

openings are proposed in the CMU if I wanted to avoid running a calc on using it for primary lateral support (bypassing the cmu wall) and I had other new walls beyond the cmu wall on both sides, could this work, assuming the diaphragm had the strength to span the distance

 

[KootK]

...but can CMU block be treated as it would be a wood block to transfer shear across it?

Sure, easily with appropriate detailing.

..could this work, assuming the diaphragm had the strength to span the distance

It could. Obviously, you'll need chords that run that distance as well. Those might pose more of a detailing challenge if the CMU would interrupt the chords as well as the shear panel sheathing.

openings are proposed in the CMU if I wanted to avoid running a calc on using it for primary lateral support (bypassing the cmu wall) and I had other new walls beyond the cmu wall on both sides...

This sounds like a displacement compatibility discrepancy. Just because you want the wall to cease it's lateral participation, that doesn't mean that it will. Structures tend to be pretty piss poor listeners. I'd take a look at your estimated diaphragm deflection at the disregarded wall and give some thought to what needs to happen to that wall for those displacements to be accommodated.

 

[radiocontrolhead]

Koot,

I agree with your last point. It is the one that stares me straight in the face the most.

Alternatively, I'm trying to justify evaluating a cmu shear wall that has a significant opening cut into it. We are in high seismic and the client wants to avoid adding any additional structure to make up for it. Say by means on shotcrete, CMU, or building a wood wall proud of the CMU.

The biggest challenge I see is hooking the horizontals around end vertical bars, something I can only see being done by introducing new boundaries. What is your take on it?

 

[KootK]

What is your take on it?

I'm afraid that I don't have enough experience with this to be able to offer any definitive suggestions. Hopefully someone else can pick up the slack.

In the most general of terms, a reasonable strategy might be to take the longest, opening free chunk of wall and do whatever you gotta do to upgrade that by the book as a solid shear wall. Then find a way to justify that the remaining wall segments could ride along with the solid shear wall drift without compromising their gravity load resisting function. I admit that's all pretty loosey goosey in terms of the actual details of your analysis. Big talk when it's your fee sensitive project and not mine...

 

[radiocontrolhead]

Koot,

This was exactly what I had in mind. Taking a good candidate for a shear wall and retrofit (mainly the boundaries) accordingly to comply with code and the remaining bits go for a ride with it (detailed appropriately of course).