Cast-In Anchors Misplaced, Need Help with Correction

[P1ENG]

I was informed that the concrete pier was installed 2" off the mark. The steel structure is pre-fabricated and there is no way to move the steel. I was asked if they could cut the cast-in place anchors and drill new holes shifted 2" for post-installed anchors. I'm concerned because the new anchors would be 2" away from the cut, cast-in anchors and therefore wouldn't those create a spacing or edge distance issue? See below. It is a square footing with a circular pedestal. The black dots are the cast-in anchors and the purple dots are where the wedge/adhesive anchors will be. There was only 4" between the original anchors (front-to-back) and by shifting it 2" a new anchor will be directly between the (2) existing anchors.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[bones206]

Juston - Here's a sketch of what I was proposing. Does the statement that you can't move the steel still hold true? Your last sketch suggests that you are planning to move the beam centerline over 2"...

 

[Tomfh]

Regarding that photo, it’s pretty rare that you need the full section in bearing, so whilst ugly, I don’t see why it can’t work. I mean, we cut off the entire top and bottom flange in a lot of steel connections.

 

[P1ENG]

@bones206,

Yes, the steel cannot move. It is actually the pier that moved 2". Unfortunately, the anchors were near capacity to begin with. Also, there is rolling (torsion) load in the I-beam due to a horizontal component of force at the top of the I-beam, so there is actually quite a bit of tension in the anchors. I'm using worst-case loads of any/all load combinations, so maybe looking at the individual load combinations, I might get lesser loads.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[bones206]

My bad, I misinterpreted and thought it was just the anchor group 2" off center. I've updated the sketch below:

I have seen the web cut out method before at a plant. IN that case they added a local web doubler around the cutout. Managed to dig out the photo below:

 

[phamENG]

Be sure to consider the required core size to put the epoxy anchors in. It's often larger than expected and can cause real issues with rebar in small pedestals like this. If they hit your cage and cut through any rebar, any shear reinforcement you were expecting goes away, and tension reinforcement may be compromised.

How deep are the anchors? What about chipping off the top of the pier, locating the anchors relative to other base plates, and then recast the top of the pier. More work for the contractor, but a bit more reliable, too.

 

[P1ENG]

@bones206,
I'll propose this idea. I drew up your solution but I left it so the new epoxy anchor can still go through the I-beam. I don't want to move the new epoxy anchor any more to the right than I have to because I'll start to get edge distance issues and maybe run into the rebar. Yes, the beam flange will need to have local coping to clear the anchor nut.

@phamENG,
I think we will be good avoiding rebar. The original anchors had 12" effective embedment. The new anchor depth is unknown at this time. I'm not sure how much room they have to work with to drill new holes. Ideally, the steel would be moved so that they have all the room they need to drill down. I don't think chipping will be an easy sell to the client.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[dik]

I always stipulate that anchor rods be weldable whether A307 of F1554 Grade 55 S1. If they are weldable can you just locate anchor rod holes to match the installed and either weld or bolt the column in place?

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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik