Anchor bolts in face of masonry wall in shear 4

[Roukkia]

For a double row of anchors in a masonry wall I am trying to figure out for which failure modes it makes sense to split up the load into the two bolts to effectively double the capacity of my connection. For masonry shear breakout and masonry crushing I think it makes sense to apply the entire load to the bottom anchor because the top anchor will not have any capacity once the failure modes are reached. For shear pryout and steel shear I think it makes sense to divide the load into the 2 anchors because there is no overlapping area of influence therefore you will get the full capacity of each anchor independently. What are your thoughts on this?

 

[Roukkia]

I found info regarding shear breakout in ACI 318-14 Figure 17.5.2.1b. I think these ideas can also apply to masonry and specifically the masonry crushing failure mode.

 

[dik]

For masonry, I generally use Hilti's Profis software, but don't design it too tight... about 70%. There is other fastener software out there.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[Roukkia]

Thanks Dik. Was doing these calcs by hand. And specifically referencing TMS 402 for my masonry failure modes and equations. I didn’t think Hilti did normal anchor bolts for masonry in their program but I could be mistaken.

 

[dik]

This was one of my recent connection problems...

It can handle problems of this ilk.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[WinelandV]

Roukkia,

Hilti allows you to do anchors in masonry in their online program (profisengineering.hilti.com). You will need to buy a license to use it (only anchors in concrete is available for free). See Dik's comment below.

 

[dik]

Oh, oh... I have only the free copy.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[WinelandV]

I stand corrected then! Thanks, Dik.

 

[Roukkia]

dik/winelandv - I'm only seeing options for Hilti's post installed anchors. What other software have you seen that designs anchor bolts per TMS 402?

 

[dik]

For masonry construction, the anchors are generally post installed... I'm not aware of TMS 402 requirements.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[le99]

The bolts receive the load due to the tendency of downward displacement of the base plate. If the upper bolt, or the plate, is strong enough to resist the load without measurable displacement, the lower bolt might not feel much of the load. However, metal yields, thus the lower bolt eventually will share the load. The ratio of the load sharing will change and is usually assumed 50/50. Note that, on top of shear, the upper anchor bolt is likely to carry tension, which will render it more critical, so you have to ensure this failure mode won't occur.

 

[WinelandV]

Roukkia,

I don't know of any software for anchors in concrete (if anyone does know, feel free to correct me), let alone anchors in masonry. I made myself a spreadsheet for cast-in anchors in concrete - you will have to do the same for cast-in anchors in masonry.

 

[jayrod12]

The simpson anchor designer program will do cast-in anchor bolt design. At least it does for CSA, which to me doesn't happen unless it already does it to ACI.

 

[JStructsteel]

dik, did you go with the HY 270 adhesive?

 

[JLNJ]

Hilti's Profis (full-blown version) has the ability to look at prying in this type of end-plated connection. It's very eye-opening how different the fastener forces can be with prying versus without. (I have written prying but really what Profis does is look at the flexibility of the plate.)

As an aside, Hilti now has values for the HY-200 adhesive in CMU walls. You no longer need to specify HY-270. And, if that's not enough, there is a new HY-200 on the market.

 

[dik]

... always Hit-Hy 270 for masonry... it's great glue.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[masonrygeek]

TMS' Masonry Designers Guide (2016 version) does give some insight into this, but doesn't cover everything discussed here (

https://masonrysociety.org/product/mdg2016-download-version/).

And TMS 402 does cover anchor bolts in Section 6.3 (2016 version).

 

[dik]

JS and JLNJ... it appears that Hilti is in the process of including Hit-Hy 200 for masonry as well as concrete. I've got a call into their local tekkie to see what's up... thanks for the information. 200 is good glue, too...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[Roukkia]

masonrygeek - I was using TMS 402 to design the anchors but I think I came across a condition that TMS does not provide guidance for. I have posed this question to the committee and they admitted that they have not thought about this particular condition. See my attached sketch. The question becomes what do you use for your shear area. ACI thinks (if this was concrete instead of masonry) that it would be acceptable to use the edge distance to the top anchor in determining your shear breakout area, assuming the anchors are welded to the plate (they also provide guidance for when anchors are not welded to plate). I think this would be an acceptable procedure because for shear breakout to occur, both anchors would have to breakout. With a similar anchor layout, do you think it would be acceptable to divide the total load to the connection between the two anchors for the masonry crushing failure mode per TMS?

 

[le99]

I would check both modes depicted below.