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Baseplate anchorage into concrete pier

Baseplate anchorage into concrete pier

Baseplate anchorage into concrete pier

(OP)
I have a building supported on concrete piers and spread/strip footings. The column bases at the braced bays experience significant tension load (maximum of 65kips under seismic loads). The footings are 4' below the top of the slab, the slab is 1' thick and the top of the piers are 4" below the underside of the slab. Depending on the footing thickness, the piers can be as short as 16". I have designed the anchor rods to anchor into the footings in order to develop the tension force into the foundation.

The contractor does not like this detail, as it requires him to cast the footing/pier/perimeter foundation walls at the same time.

Is there a workaround to this?

As the rebar is currently fabricated, I am thinking about shortening the anchor rods to fall completely within the pier and adding vertical hooked bars to the piers (hooked at the top of the pier) and to WELD these bars to the pier vertical bars that hook to the footing. This should prevent concrete breakout under tension load. The bars that have been fabricated already are weldable. Thoughts please?

RE: Baseplate anchorage into concrete pier

What you've proposed can certainly be done given that all of the forces can be transferred within the space available. Given what you've told us of the situation, I'm a bit skeptical. If you provide a sketch showing geometry and rebar sizes, I'd be happy to give this a closer look.

I've had contractors embed anchor bolts into footings and leave them sticking out until future wall/pier pours. It's not ideal for tolerances and constructability but it can be done.

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

RE: Baseplate anchorage into concrete pier

What about casting short anchor bolts into the footing and then putting a union nut and extend the anchor bolts when you go to pour the pier?

RE: Baseplate anchorage into concrete pier

I couldn't come up with the proper term earlier. A coupling nut can be used to connect new lengths of threaded rod to the anchor bolts that are cast into the footing. This should also give you the flexibility to improve your tolerances in terms of anchor location at top of pier if the ones at the base weren't placed exactly correct.

RE: Baseplate anchorage into concrete pier

You DWYWIDAG threaded bars and embed the coupler - Similar to Jayrod's suggestion.

Also you could use a DEMO VEMO (maybe that's VEMO DEMO, I always get confused) or a lenton bar splicing product.

The tried and true connection used is a drossbach duct, but they do not seem to be a popular tool in North America and your contractor might give you a hard time about the installation of the grout and witness tubes. Personally the drossbach ducts would be my go-to detail if they can fit into your detail.

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