PEMB Anchor Bolt Repair

[ron9876]

I have a condition where 2 of 4 anchor bolts for a PEMB rigid frame base plate are not in the correct location. The concrete capacity of the anchor group was determined based on a headed stud capacity type of calculation. The anchors are threaded rods with nuts tack welded at the embed depth. The embedment depth is 21".

So the question is how to repair this. I can't find an undercut anchor that is 21" long. If I use epoxy anchors they are bonded full length so the load isn't delivered at the base of the area of concrete used to determine the capacity of the embedded bolts. So I am at a loss. Has anyone had to deal with this condition before?

 

[msquared48]

I would look at the capacity of the (2) bolts that are good and compare that to what is actually needed, then consider installing oversized epoxied bolts where the epoxy is only in the lower half of the embed depth rather than full depth (with associated reduced capacity), and see if that can make up the difference.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Ron]

Another option is to abandon the existing bolts and use all epoxy bolts for the anchoring. Oversize them.

 

[ToadJones]

I'd prefer to modify the base plate if the frame has not been installed yet.

 

[haynewp]

Have you considered welding a plate to the column web at each side and extending it out to new base plates with post installed anchors away from the existing anchor pattern? Or is the column supported by a smaller pier down to a ftg?

 

[ron9876]

There isn't room to extend the base plate. I went with msquared48's approach. Not sure how to analyze the condition but I extended the new anchors below the existing bolt anchorage.