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

 

[jerseyshore]

Do you need to move the anchors strength-wise? Would an offset baseplate work in this case?

I prefer not to put anchors so close, even if the original ones aren't taking any loads.

If you can make the offset baseplate work on paper I would just drill new holes in baseplate and use the original anchors.

 

[Lomarandil]

I don't believe abandoned anchors would count against spacing limitations in your calcs (although edge distance is possibly still an issue)

 

[P1ENG]

@jerseyshore

An I-beam bottom flange is the "base plate" and if we don't move the anchors, the original location would interfere with the web of the beam.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[P1ENG]

@Lomarandil,
That was my thought. I would expect anchor forces <2" away would cause spalling at the abandoned anchors.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[PEFLWI]

I don't think the existing anchors will interfere with the performance of the new anchors. I would use the Hilti program to check the post installed anchors.

Have you considered modifying the base plates?

 

[bones206]

I would add a ~10" long bearing plate to the bottom of the beam flange. Cut off the purple bolts at the pier CL and keep the purple bolts at the top. Mirror those with new post-installed anchors on the bottom half of the pier. Then the holes in the new base plate are made to match those anchor locations.

I just dealt with this yesterday haha. Deal with it pretty much on every project.

 

[GC_Hopi]

How much of the web do you need? Cut the web out at the anchors. Weld in a stiffener if you need more bearing capacity at the beam.

Here is a snip from AISC Field Fixes to Common Problems.

 

[jerseyshore]

GC, that picture makes me uneasy just looking at it.

 

[jjl317]

FWIW - I believe both Simpson and Hilti have some information on placing new anchors near abandoned holes - from memory, it doesn't necessarily cover every condition, but it does have relevant information.

 

[canwesteng]

If you needed that much flange at the base of the column, there's no way those anchors would work in the first place, so the photo seems fine to me,

 

[bones206]

I think OP has a beam directly bearing on this pier - not a column.

 

[Eng16080]

For a different type of solution, assuming you have a beam resting on the pier, what about running a steel plate down the face of the pier, welding it to the beam bottom flange and using post-installed anchors to attach it to the pier?

On top of the pier, the existing anchors would be cut-off flush.

 

[P1ENG]

Sorry for being MIA during these conversations, but I have about (4) fires that were started this morning. When it rains it pours. I'll be back with more information and to answer some questions when I get some time.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[ALK2415]

@ GC_Hopi
this is disastrous solution, are you sure its from AISC Field Manual !

 

[GC_Hopi]

@adn26
Dont shoot the messenger. You can make your own engineering judgement call.

Here is the language from Steelwise.

 

[RWW0002]

I remember that image from an old AISC presentation. I think it was a presentation by Dr. Fisher on "Field Fixes and Solutions"

If I am remembering right the image was presented as a case that the contractor made their own "fix" and one that looked pretty bad. However after evaluating the condition and the loading requirements, it was found acceptable.

So not exactly a field manual - but an acceptable fix for some cases/conditions.

The presentation is probably still available online through AISC's website

 

[GC_Hopi]

Good memory RWW0002 and it is not a field manual. I stated the source in my original post.

 

[P1ENG]

Ok,
So here is what it would like under the proposed change.

Furthermore, I searched for Hilti information on abandoned holes and all of the hits I was getting referenced this document. I'm digesting now.

Juston Fluckey, SE, PE, AWS CWI
Engineering Consultant

 

[canwesteng]

Personally, I'd be much more comfortable with a hole in the web and an extension of the web to make the anchors as cast work. You probably have a stiffener near the end of the beam anyway.