Minimum shear reinforcement for masonry

[HardyParty]

Hey guys!

Is there a minimum shear reinforcement requirement for a masonry wall?

I am building a masonry building for a WWTP and for flexure, I have designed it to have no7 @ 34" oc. Now I am looking at the shear walls for the structure. If the CMU has enough strength to resist the shear forces, do I still have to use some minimum steel provision? I was looking at MSJC 2.3.5.3 but am a little uncertain. Thanks.

Jess

 

[msquared48]

#7 @34" OC?

Seems like an awful large bar, and if the masonry is CMU, it does not fall on an 8" grid for the cells.

What kind of masonry are you dealing with?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[HardyParty]

I'm sorry I meant to say 32". It is 12" CMU.

The bar is large because it is controlled by the 0.6D + W(-) load combo. This gives the wall a very small point load (-1.4k) with a 1247ftlb moment.

 

[HardyParty]

I'm sorry 10" block. I am getting projects confused.

 

[pittguy12]

Minimum shear reinforcement is going to depend on the type of wall you are building...ordinary, intermediate, or special shear wall. Have you narrowed down your Seismic Design Category yet? This will dictate what wall type you are allowed.

Beyond this, if the unreinforced masonry section can take all of the shear force no reinforcment is necessary. However, the problem you run into is that unreinforced masonry is not allowed beyond SDC A I believe and you therefore must put in some reinforcement. And if you put it in, you have to design it to take all of the shear force and that is where you get into making sure you provide enough according to 2.3.5.3. Make sure you compare this though to the required amount in Chapter 1 for wall types.

 

[HardyParty]

It is a SDC A, so we're good. Thank you for the clarification!

 

[dswag]

If you are going to fill the cells anyway than it's no big deal to through some reinforcement in there. #4 - 24" O.C. horizontal and vertical. Call a masonry Contractor and see what spacing gets expensive. In California #4 - 16" O.C. is common