Placing wedge anchors next to abandoned anchors.

[clee61]

Hello,

I am looking at a case where we have an post-installed anchor that was installed incorrectly and now we are proposing to install a new post-installed wedge anchor next to the defective anchor (about an inch away).

Right now, I'm looking at the concrete pull out strength to see if there is a reduction in this strength and by how much. We are waiting to hear back from the anchor company, but I was wondering if there is any part of the code that allows this. I would think that this occurs many times where a bolt wasn't installed correctly and a new bolt needs to be place within the 6*bolt diameter spacing required by the ACI code.

Also, would leaving the defective bolt maintain some strength in the concrete rather than leaving an empty hole?

Thank you,

 

[CELinOttawa]

Remove the incorrect anchor and epoxy the hold. A good epoxy will make the concrete "blind" to the new anchor; Leaving the anchor in you're going to be restricted to the (too conservative) group reduction factors unless someone has specific research to support your case.

Epoxy, properly selected and designed, will give you the win here.

 

[wannabeSE]

Have you heard from the anchor manufacture? Leaving the bad bolt cut-off at the surface or filling the hole with dry pack is better than an empty hole. I don't know of any code reference. The 1982 ASCE Journal of the Structural Division article Effect of Abandoned Hole on Wedge Type Expansion Anchors (

http://cedb.asce.org/cgi/

http://WWWdisplay.cgi?34048)

provides some guidance with spacing recommendations between abandoned and new anchors.