Anchor rod Placement - Bending to correct location?

[rharting]

I'm the EOR for a small one story building where the contractor has installed the anchor rods slightly off from where they should be. AISC code of standard practice indicates that anchor rods should be placed within 1/8" in any bolt group and within 1/4" between columns. For a project of 48 columns, 1 of the column connections actually meets this criteria. The reaming 47 range from 5/16 to 3/4". The columns are currently on site (with the base plates connected) and are ready to be erected. We had a survey completed and we have a detail for each column base (as designed vs installed) and determined that by increasing the diameter of the hole in the plate to 1 5/8" (and installing a plate washer on top), we can accommodate another 16 column bases.

We had a meeting with the owner and various contractors (fabricator, concrete contractor, etc) and they pushed for core drilling through the top 3" of the pier at the anchor rod locations and bending the anchor rods back into place. Including the grout, this would require the anchor rods to be bent somewhere around 5/8" over a 4" distance.

All of these columns are gravity only columns by design (the 4 locations where we have bracing the base plates is being removed and a new one installed.

I'm not overly comfortable with this solution. Although after reading this thread thread507-361541 I'm second guessing myself. IMO I believe it would be better to increase the size of the holes for those 16 and then for the remaining, add new holes and epoxy anchors at a 45 degree angle (cutting the anchor rods at the corners and add 4 new A.R. off of the flange/web).

 

[KootK]

For gravity only columns, I'd let the contractor do whatever they like so long as you end up with something that meets OSHA and provides a nominal shear capacity. I'm surprised that core drilling is their preferred option. I would have thought your proposals cheaper. They would certainly involve less risk of damage to the concrete.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[ztengguy]

If WF columns, can you put holes inside the flanges and drill and epoxy?

 

[RPMG]

My recommendations,

1. For columns where uplift is not an issue (unless extreme wind event), use epoxy adhesive anchors like ztengguy suggests.

2. Cut the base plates off and weld new ones. Provide additional grout as required.

3. Over-drill the holes and encase column base in concrete, so shear transfers at the column base and does not slide on the hole.

4. Re-check the anchor failure modes per ACI Appendix D prior to giving the OK for core drilling. If that's near the head of the anchor, it could be a problem.