Broken Anchor Bolts

[Steve Frazier]

I have a situation at work that I'm looking for repair options on. One of the parking lot lights was knocked over and when I went to remove the nuts from the light base they broke off, the 5/8 bolts had rusted to about 1/4 inch. They were cast into a concrete pedestal about 2 feet high, there are 4 of them per light, one light per pedestal. I've spoken with our town engineer and we've come up with the idea of epoxying new bolts into the concrete but the question is how to drill out the existing bolts? I figured you guys here would be a good source of ideas! Thanks

 

[lantraxco]

Core drill would be the only way to do it, and Gawd knows how much rebar you'll run into.

 

[Delmer]

Without seeing it, I'd rotate the base 45 degrees and drill four new holes. Or grind down to solid steel and weld new bolts in place if they can't be rotated. If there's enough room on the base, you might get away with shifting all the holes 2" in one direction.

The one thing I'm pretty sure won't work, weld a nut onto it and try to unscrew em. I tried that handy trick once REPEATEDLY, only to finally realize that the bolts in question were stud welded and were not going to unscrew. However, if you chip off 3" or so of the top of the whole base, I bet you could come up with a nut coupler that would thread onto the good section of bolts if they're threaded that deep, then get some grout mix and pour the top of the base back together.

 

[lantraxco]

I would suspect they're "J" bolts embedded in the concrete, at least that's standard practice around here....

 

[Tones]

How about using Dyna Bolts? I've seen them hold some pretty big structures

 

[old-iron-habit]

If the concrete base size allows, weld a plate on the bottom of the existing one and drill new anchor bolts. You can probably rotate the bolt holes that way while keeping the pole orientation correct. I would use a hardened all-thread style anchor with epoxy and a foot or so of embedment to insure you are in good concrete.

 

[Steve Frazier]

I'll get a picture of the concrete footing tomorrow and post. There really isn't a lot of extra room on the top of it, I like the idea of an oversized plate if I can drill without compromising the concrete. Thanks everyone for the input! There are 20 of these lights on the property, I'd imagine they're all in similar condition.

 

[old-iron-habit]

You may be allowed to drill at a slight angle toward the center of the pier to get more strength on the anchor for use with an oversize plate. Install a full nut thickness and "tap" them enough to bend vertical. Standard is normally 3" minimum from the concrete edge for drilled anchor.