Post Installed Anchors Due to Anchor Misplacement

[HDStructural]

Hello all,

I am working on a small project where we are replacing a few anchors due to anchor misplacement. We will be using an adhesive anchor system. The problem that I am having is that the anchors are only off by 3/4" or so, and are in the way of where the new anchors would be.

Is it possible to do a large core drill of the concrete area (maybe 2" or 3" diameter) that would contain the existing anchor rod. Then epoxy in a new anchor? The issue I see is that the whole would be way too large.

Could I have them roughen the surface around the hole then fill it with concrete/grout and just place the anchor bolt in? Due to the left/right eccentricity of the anchors, we cannot just slot the base plate holes.

What have been your best solutions for these situations?

 

[jayrod12]

Why not just refabricate the baseplate to accommodate the as-installed locations? That's likely what I'd be doing.

 

[HDStructural]

I agree, that would be an easy solution. Our client wants the solution to not touch the steel though, only the concrete.

 

[ANE91]

Look to the epoxy manufacturer. For example, Hilti has addressed this condition in white papers and such. Oversized holes are usually permitted (to a degree) with a commensurate reduction in capacity, though 3” is more than I’ve ever seen. You’re right to think that a cored hole would typically need roughening.

https://www.hilti.com/medias/sys_master/documents/hc2/h5b/9677369933854/Technical-information-ASSET-DOC-LOC-7502228.pdf

I’ve also had success proof-loading anchors that were installed beyond the scope of the ESR.

 

[Tomfh]

Core out the old. Fill hole with epoxy grout (eg fluid epoxy plus sharp sand in a pourable consistency, or a proprietary pourable epoxy grout).. Drill new hole

Or core big enough to cover both both locations, and cast in the new anchor into the epoxy grout.

 

[HDStructural]

Tomfh, that's what I was thinking. How would I calculate the breakout capacity of the concrete and epoxy grout? Or ensuring adequate bond strength of the concrete to grout?

 

[Tomfh]

Tomfh, that's what I was thinking. How would I calculate the breakout capacity of the concrete and epoxy grout? Or ensuring adequate bond strength of the concrete to grout?

Product literature or tech support will usually confirm a producs strength. They are typically stronger than surrounding concrete.

If you roughen up the hole and use a suitable product the epoxy grout plug won’t be coming out.

 

[driftLimiter]

3" diameter core is too big for any epoxied bolt or rebar but, You can use threaded inserts in core drilled holes. HILTI HIS for example. If the geometry works out the old hole could fall within the new core drilled region and you get a clean ESR installation.

When outside of ESR limits I have also had success with proof testing but really its not a fun road to go down.

 

[dvd]

Grouting seems like the way to go - some literature from file attached