Anchor Bolt to Base Plate Weld

[Stenbrook]

I have a situation where the contractor has set the anchor bolts for a base plate in a 9" by 9" grid vs the 13" that it was supposed to be. I have checked the anchor bolts and have determined that it can still work as long as we expand the base plate some to increase the moment arm (these base plates are resisting moment).

The issue is attaching the base plate to the anchor bolts. With the column being an HSS 10x10, the bolts will be directly underneath the column. Our idea is to cut the bolts so that they are beneath the top of the base plate and weld the anchors to the plate thus creating a flush top of plate. The question I have is, is this even possible to weld, and if so, what kind of capacity can I realistically expect to achieve? The other solution we have involves post installed anchors with a larger base plate. Our client has asked for us to look into less expensive methods of fixing this issue.

 

[jdgengineer]

Modern Steel Construction magazine had a good article about this not too long ago with a bunch of potential fixes. While not directly applicable to your case, I think some of the conversation is similar. In order to weld, the anchor rod needs to be a weldable grade. Post-installing anchors in a different pattern that works with the larger baseplate may be a better solution.

https://www.aisc.org/globalassets/modern-steel/archives/2016/09/steelwise_1.pdf

 

[Stenbrook]

Thanks for the reference! I am familiar with most if not all of those fixes, which I would love to do, except for the fact that I can't put any nuts or washers above the plate and still fit the column on the plate.

 

[structSU10]

I take it the column and baseplate are not already fabricated? If they are, your cheapest is probably cutting off the anchors and post installing.

another option may be to set a standard base plate for the rods at 9", then have a spacer/jumper plate that attaches to a main base plate for the tube steel. the spacer/jumper is thick enough to allow for the nut, then the other plate is field welded to that assembly.

 

[JAE]

If you are taking moment at the base of the column then using some weird weld around the anchors to take this force doesn't appeal to me. Field welding in the dirt, on a footing, on your knees is varied enough to worry me on Quality Assurance here. I would use a post-installed anchor as per jdgengineer or structSU10 to clear the anchors from the column.

Or have the contractor re-do the footing with the correct anchor layout.

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[JoshPlumSE]

I get what you're trying to do (kind of like an embed plate with nelson studs), but I don't see how you can create that after the fact.

If the anchor rods already in place, I don't see how the welder would be able to make that weld to the underside of the base plate. What sort of clearance would he have to get in there?

Why not just use post installed anchors at the correct location (13" grid) instead?

 

[CBSE]

Or, are you asking if it is possible to bevel a home in your base plate and do a fillet weld from the top?

 

[Stenbrook]

JoshPlum, post-installed anchors do not have the same capacity as the cast-in place so placing post-installed anchors at 13" does not work. I also don't have a lot of room to expand the grid of the bolts since I am sitting on a grade beam and am at the end of it.

CBSE, that was one option I had considered, but I'm not sure you could fabricate a plate with a beveled hole. Our thought was to have the bolt extend halfway into the plate, square weld the anchor bolt on the side to the plate all around and then fill in above the anchor to the top of the plate with a puddle weld.

I agree that this is not the most ideal situation, and I could just tell them they have to use post-installed anchors and deal with the cost of it, however I feel like it is our responsibility as engineers to look at all the possible solutions and come up with an efficient and creative fix for the problems we encounter.

 

[XR250]

What about notching the tube steel around the anchors and welding?

 

[Lomarandil]

I think a spacer/jumper pedestal like SU10 suggests may be the most reliable way to resolve things, although relatively expensive. Also ugly, but that's where most of my solutions start.

I'm envisioning something like a short section of HP sandwiched between two plates -- one to match the AB pattern, one to match the base plate pattern.

I also have concerns about the quality of any weld in the dirt, especially if you're talking about halfway down some sort of square hole.

----
The name is a long story -- just call me Lo.

 

[EZBuilding]

I would tend to agree with the other posters when have stated that they do not like this condition, but I thought of something that could be a possible solution.

Could you introduce a secondary plate which accepts the anchor rods at the 9" grids and also provides attachment points for a separate set of bolts at the 13" grid. Note that your moment due to eccentricity with this connection would be increased.