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

[abusementpark]

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?

 

[JedClampett]

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.

 

[ToadJones]

3.2.4?

 

[ToadJones]

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.

 

[asixth]

Dowel action of the bar that crosses the joint.

 

[abusementpark]

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.

 

[abusementpark]

Sorry above the typos above.

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.

 

[ToadJones]

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

 

[abusementpark]

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?

 

[abusementpark]

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.

 

[ToadJones]

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

 

[abusementpark]

No problem.

 

[BAretired]

BA