Anchorage to face of CMU wall

[PostFrameSE]

Is it possible to connect to the face of the top course of a CMU wall (designed as a bond beam or lintel with horizontal reinforcing and vertical reinforcing punching through the cores to tie down to foundation) in lieu of depending on precise placement of anchor bolts by blocklayers such that I don't have to be quite so concerned about precise anchor bolt placement? I work with wood trusses spaced approximately 8' o.c. and the uplift loads can be on the order of 2-3kips, and therefore, anchor bolt placement is critical. Will anchoring to the face create a "block shear" or tension failure in the block itself, or can a "scoop-block" be counted on to carry the shear loads (vertical uplift) adequately? Any direction would be appreciated. Thanks.

 

[MiketheEngineer]

Couldn't you place rebar in cavities and grout solid. Then place anchor bolts in these grouted cavities. I think this should be OK??

 

[ataman]

I don't see why not.

You just need to check the failure cone for the bond beam due to the applied shear.

Once the load gets into the bond beam / block masonry, the load path to the foundation is the same as if you had achor bolts in tension.

 

[PostFrameSE]

I have specified rebar in the cavities and grouted solid, only to have masons, who don't or can't read simple drawings, place anchor bolts incorrectly. I am tired of the headaches, and therefore am looking for a way in which anchor bolt placement isn't critical.

Ataman....pardon my ignorance, but how do I check the failure cone for the bond beam? Do I assume that I really only have 1/2 of a cone since the uplift condition will be pulling up on one side of the block? Since my fasteners are fairly well distributed in the face of the block, do I just take the "perimeter" of my fastener group and run my cone into the block from that perimeter? What angle of a cone can/should I use for CMU / grout?? Can I assume that the grout, joints, and CMU really act as one? Is 45 degrees acceptable for a cone?

I hope that makes sense. Thanks to each of you for your reply!!

 

[concretemasonry]

For grouted masonry, you can assume that the grout and masonry units act together.

Dour detail requirement of attaching to the wall face makes it difficult and will add some moment to the wall.

 

[UcfSE]

If you are in the US, you would use the ACI 530 code. It contains provisions for the design of anchors in masonry for tension and shear, and edge distance effects.

If you are using a manufactured post-installed product, you would turn to the manufacturer's test data and edge distance and spacing requirements.