Mis-placed anchor rods 1

[SperlingPE]

If anchor rods are mis-placed by inches, can post installed anchors be installed adjacent to the cut off anchors?
My thought is that the cut off anchors would be like a piece of rebar in the footing.
I should say that there is tension on the new post installed anchors.
The cut off anchors would be within the potential failure cone of the new anchors.

 

[KootK]

I'll buy that. KootK approved.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[DETstru]

The only possible difference I can think of is if you're literally tangent to the other anchor you'd have a bit of epoxy trying to bond to the old anchor. I can't imagine that has any meaningful impact to the tension capacity (for better or worse).

And if the breakout cone cuts through the old anchor it's like added shear reinforcement!

 

[WARose]

If anchor rods are mis-placed by inches, can post installed anchors be installed adjacent to the cut off anchors?
My thought is that the cut off anchors would be like a piece of rebar in the footing.

Yes but they wouldn't have the same effect as re-bar would. (If you are thinking about the cut off anchors as providing some sort of reinforcement for the anchor zone.) Depending on the diameter of the bolts, having cut off anchors a few inches away shouldn't have much of an impact on the post-installed anchors. Too close and you could impact the bond......but (say) 1/2" diameter post-installed anchor 2-3 inches away from a cut off 1/2" diameter bolt? It's like the cut off isn't even there.

 

[SperlingPE]

1" rods cut off
new 1" post installed anchors 2" away
center to center distances

 

[sandman21]

The main article does not deal with your issue, but someone asked about it in the comments. Simpson responded take a look. Simpson SE Blog

 

[WARose]

1" rods cut off
new 1" post installed anchors 2" away
center to center distances

Given that, I'd take a bit of a reduction. How much would be a judgement call about the amount of failure zone/bond interrupted by the adjacent bolt. sandman21's article provides some good info.

 

[jayrod12]

Hilti put out some literature regarding holes, drilled in the wrong location or started but unable to reach proper depths and therefore abandoned, and their effect on anchors installed adjacent to the abandoned holes. I'll try and find the stuff but I would likely consider it something akin to that.

 

[bones206]

A local Hilti rep stopped by our office today and had us answer some survey questions. One of the questions was regarding how often we used post-installed anchors to replace mislocated cast-in-place anchor bolts. Seems it's an issue they've been looking at. I would give them a call because they are always helpful and have great technical as well as anecdotal knowledge.

 

[jayrod12]

As it turns out, it was actually a Simpson Strong-tie engineering letter regarding abandoned holes. It is just a formal presentation of the info in the link sandman21 provided.

 

[SperlingPE]

I have been in touch with Hilti rep.

 

[Once20036]

Care to share what they told you?

 

[SperlingPE]

Hilti rep referenced some testing done in the 80's [no link provided] with abandoned holes and wedge anchors.
The response did not address my specific situation with an abandoned cast in anchor.
I am waiting on additional information.

 

[WARose]

@ the OP: I sketched out a variety of failure/bond zones for your situation and I came out with about 8-15% reduction in capacity. (Just thought I'd share.) That's not that far off from some of the numbers in that Simpson's blog.