Cracking of an Existing Concrete Wall by drilling Anchors in it 1

[Berniedog]

I need some help. We are analyzing an existing tank wall from 1973. It is 16" wide and 21' tall. It is part of a wastewater tank. We are designing a shoring system to add a wall on the other side of the wall. We have to drill 1 3/4" diameter holes, 10" deep in it for 1 1/4" anchors. The reviewing engineer believes this will cause the wall to crack. There is enough shrinkage and temperature steel in the wall.

Has anyone ever heard of a wall cracking because someone drilled some holes in it and added anchors to it?

 

[PEinc]

Yes. Talk to Hilti Tech Support. Check edge and spacing distances. Mechanical expansion anchors can break out concrete if too close to an edge.

http://www.PeirceEngineering.com

 

[MacGruber22]

I don't think there is not enough info to give reasonable answer. Though PEinc's answer is true, I suspect there is something else going on here.

It sounds like the engineer may be categorically disapproving the use of the anchors for some reason.

One in the hand is worth two in the bush.

 

[Whoopdedo_LSU]

1)
"Talk to Hilti Tech Support."
Call them.

I deal with Hilti all the time and they normally give good answers. All depends if you want to use their anchors (say you do).

2)
"Has anyone ever heard of a wall cracking because someone drilled some holes in it and added anchors to it?"
I've had this happen.

Need to get in contact with the EOR. If you cant, you need to assume worst case scenario I'd assume.

 

[racookpe1978]

I'd question 1-3/4 dia holes for a 1-1/4 inch anchor.
Seems much too large a gap for epoxy-bonding (which WON'T put an additional tension stress into the wall), and too loose for a regular expansion-bolt anchor.

 

[slickdeals]

Is there a reason you are using 1-1/4" anchor? The wall thickness doesn't appear to be adequate to get anywhere close to the capacity of the 1-1/4" anchor.

 

[Berniedog]

The contractor wants to use a rock anchor. No epoxy.

 

[dik]

Careful... expanding rock anchors can produce large anchorage compression forces.

Dik

 

[PEinc]

What does the contractor mean by "rock anchor" when being used in a concrete wall? Cement grout will not work easily for a horizontally drilled bolt. Spin-lock bolts are mechanical expansion anchors that are grouted after expanding. The concrete can crack or spall from a bolt's design loads even if you do not use mechanical expansion anchors. 1.25" diameter bolts are fairly large and will need a lot of edge distance and bolt spacing to achieve their maximum capacity. Hilti tech support is very helpful. Their bolts are expensive, but you get what you pay for!

http://www.PeirceEngineering.com

 

[KootK]

Within reason, do we care if the wall cracks? I thought the name of the game was tight crack control, not crack prevention. Otherwise, why bother with rebar? Certainly, I'd expect the use of more, smaller anchors to improve your odds of not cracking the wall.

Maybe pitch through bolting for sport.

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.

 

[msquared48]

Totally agree with PE here...

Mike McCann, PE, SE (WA)

 

[hokie66]

Unless you are close to a joint or an edge, I can't imagine cracking caused by a deep expansion anchor.