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Shear strength mechanism in CMU walls for out-of-plane loading?

Shear strength mechanism in CMU walls for out-of-plane loading?

Shear strength mechanism in CMU walls for out-of-plane loading?

(OP)
For out-of-plane shear strength in reinforced CMU walls per ACI 530, does it matter if the shear is checked at a pour joint or not? It doesn't say anything. It seems like this would affect the shear strength.

For example, at the base of a cantilevered CMU wall, can I use the ACI 530 shear strength equations, even though you are only relying on friction and/or grout bond for shear strength?

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

Since most CMU has horizontal mortar joints every 8 inches, I'd say it would be an unbelievable oversight to not consider the shear through a joint in developing the allowables.

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

3.2.4?

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

Sorry...
Read the commentary for 2.2.5 for Shear.

It recommends using section 2.2.5.2 for limiting out of plane shear.

There is also nice flow chart for shear design in the commentary.

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

Dowel action of the bar that crosses the joint.

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

(OP)

Quote:

Sorry...
Read the commentary for 2.2.5 for Shear.

It recommends using section 2.2.5.2 for limiting out of plane shear.

There is also nice flow chart for shear design in the commentary.

That is for unreinforced masonry. They have separate shear provision for reinforced masonry. For walls, I'm not sure why there should be a difference, unless shear reinforcement in provided.

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

(OP)
Sorry above the typos above.

Quote:

Since most CMU has horizontal mortar joints every 8 inches, I'd say it would be an unbelievable oversight to not consider the shear through a joint in developing the allowables.

Right, but the pour joints in reinforced CMU walls are less frequent, maybe 5'-0 on center. I can't imagine that the shear strength at a pour joint would be the same as away from the joint.

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

I think it is all covered in the flow chart for shear in the commentary...Figure 2.3-2.
It's been a few years since I have designed masonry....just trying to help.
Sorry

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

(OP)

Quote:

Dowel action of the bar that crosses the joint.

The vertical bars in a reinforced CMU wall are generally sized based on out-of-plane bending. If you wanted to rely on the dowel action or shear-friction mechanism, wouldn't you need to up the size of the bars accordingly?

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

(OP)

Quote:

I think it is all covered in the flow chart for shear in the commentary...Figure 2.3-2.
It's been a few years since I have designed masonry....just trying to help.
Sorry

The flow chart doesn't address the presence of a pour joint or not in reinforced masonry. Thanks.

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

I realize that now.
I am sorry to waste your time.

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

(OP)
No problem.

[thumbsup2]

RE: Shear strength mechanism in CMU walls for out-of-plane loading?

thumbsup2

BA

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