Masonry Anchorage

[dik]

Does anyone have literature on anchorage into masonry that is not fully grouted?

I'm planning on adding masonry anchors to an existing CMU wall and am only planning to grout the cores at the anchor location. The entire wall is not grouted.

In the absense of literature I will use the mortar shear on the CMU faces and any moment forces from the anchor being eccentric to the block face to give me a maximum 'block' pull-out force (friction neglected). Any comments on this approach?

Dik

 

[dhengr]

Dik:
That sounds about right to me. That’s basically been my thought process on these types of masonry anchors. I’ve grouted adjacent cores and several courses deep (high), in running bond lay-up, to key more CMU’s together and bring them into play. I’ve considered the shear and bond in the mortar joints, but that won’t really bring the next block into play in a bending or tension condition, and just barely in shear, so be careful. They really have to be keyed together through grouting to make 3 or 4 CMU’s act together as a unit. I’ve often wondered about the 7" A.B’s., at the sill plate, in wood frame construction. They grout one core, one course deep, maybe; sometimes the small middle core in some blocks, saves grout, and expect to provide shear and uplift strength. Half the time, if you had a little more finger strength you could lift that top block right out of the wall.

 

[dik]

By grouting a couple of courses... one above and one below, you are developing the grout through the mortar joint shear (or breaking out the face shell <G>) and this should be a couple of hundred psi... concrete shear (as opposed to diagonal tension) is several times the diagonal tension amount...

Still 'scratchin' my head on this...

Dik

 

[SLTA]

Have you talked with the Hilti folks? They've run lots of tests on this type of setup, and have good load data.

 

[frv]

agree w/ slta.. look at HY20 epoxy.

 

[sbouvia]

I believe what I last heard from the Hilti Rep is that they are phasing out Hilti HY-20 adhesive and it is being replaced with HY-70. Just an FYI.

 

[frv]

Thanks sbouvia.. Hilti keeps doing that... I'd been specifying X-DNI PAF's for a while and I came to find out they have been discontinued for some time.. Finally ordered an updated catalog.

 

[dik]

I've been in contact with Hilti and they recomment the HY-70 adhesive... Their anchorage values are based on either a grouted wall or a non-grouted wall... they don't have info for a grouted core in a single block... or for that matter a couple of blocks.

Dik

 

[SteveGregory]

Check to see if the ICC approval for HY-70 has been granted for grouted and ungrouted masonry for your current building code. You may want to stick with the HY-20 for a season.

 

[Ron]

dik...agree with your approach. In ungrouted masonry, the best you can do is increase the size of the "chunk" you might pull out, which you are doing with the partial fill. Moment has typically been the larger problem to solve on these.

SteveGregory...doesn't do any good to specify an unavailable product, approved or not. If HY70 hasn't gone through the process of approval (which is not likely since it is on the market), then request a letter from Hilti stating that HY70 is equivalent to HY20 in all pertinent respects. Spread the joy...er, liability!

 

[dik]

Due to an oversight (not mine) I'm looking at reinforcing an existing wall with about a 35' cantilever and a 10' backspan... and it's a matter of securing the vertical steel beams to the wall...

I like Hilti's composite 'screen sleeve' for hollow block, but the pull-out loads are too small... going to 'glue' threaded rod into filled voids or use some other mechanical anchor...

I'm not so much an ICC type of guy... I often encounter issues that have no prescribed solution... my favourite type of engineering.

Dik

 

[dik]

Should have added that the beams are secured to concrete floor plates... and that I'm still looking at HY-150 adhesive...

Dik