Anchoring Precast column

[JStructsteel]

Working on a small precast monument, and trying to figure out how to anchor the columns into the foundation. They are architectural, so they dont want weld plates, etc exposed.

I started with a grout sleeve, have rebar out of the footing into the column that has the grout sleeve

Also thought about a base plate with voids, recessed down into the foundation, grouted over later

Contractor is wanting to leave a void in footing, and have bars out the bottom of column into foundation. Say a 14" dia void, and drop column and bars down into it, and grout.

Not sure I like that, would just be relying on bond strength to anchor it. How do you leave a void, but keep it rough for interlock?

Any other suggestions?

Not a major amount of uplift, but also will be a cantilevered column for stability.

 

[KootK]

Contractor is wanting to leave a void in footing, and have bars out the bottom of column into foundation. Say a 14" dia void, and drop column and bars down into it, and grout.

This. Potentially even without the dowels. I'm pretty sure I've seen it in a European precast doc. Will search over the weekend...

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TehMightyEngineer]

Projected rebar set into carefully located drilled holes in the foudation for epoxy anchors. I've used this in every situation like yours and haven't had any issues yet. A sketch of your project might help to make sure this is what you're talking about.

A more positive connection is weld plates which are in a recess in the foundation and then get grouted over to hide them, but it sounds like drilled and epoxied rebar should be sufficient for your project.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[mjs611]

I believe the contractor is requesting the use of a pocket foundation(slide 19) which is a 'typical' foundation for precast however I have never used it. I am confused how the bottom of column would be exposed. Is the top of foundation at grade level? I have used the attached detail in the past but I work in a 4' frost depth zone. I am not a precast designer but the suppliers shop drawing reflected something similar.

http://files.engineering.com/getfil...1-a152-0168d45c608f&file=Precast_Col_Base.pdf

 

[JStructsteel]

KootK, the column would be recessed maybe 2"-3". The bars would be full length for development. What do they form the hole with? Sonotube? Cut the tube out afterwards?

Teh, its 12' square structure, 4-14" round columns at corners. 12' tall with statue on top. Using a cantilevered system for stability, and then a slab on top.

I like the idea of epoxy, they can field core them, less depth, and get them in the right spots.

 

[JStructsteel]

Thanks, plenty of ideas here.

I am just the precast engineer. the foundation is by others, we just need to agree on the pocket, anchoring of the column.

Perhaps a extension of the column below the final grade, and socket it in to the hole, and then pour final slab to grade.

 

[KootK]

KootK, the column would be recessed maybe 2"-3".

My approach would be precluded. I was envisioning a much deeper recess.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[JStructsteel]

KootK, I like mjs611 idea. A void with keyways, and then grout in the column. I could get them to extend the column into the void if required. If only rebar into void, do I not get the same final fixity?

 

[Brad805]

If your void is deep enough these Piekko connections work in some cases.

https://www.youtube.com/watch?v=C4Mm3mvN1P0

Grouted dowel base connections are pretty routine, but you will have a hole that will need to be patched to fill the duct.

 

[dik]

Can you have a pocket 4" to 6" deep and a couple of inches larger than the column with a baseplate secured to the column that projects 1/2" beyond the face of the column all around and drop the column into the pocket and fill with Sika 123 or something of that ilk? The contractor would have to provide all the bracing until the necessary parts have been secured.

One that I did with anchor rods, the anchor rods were recessed and the recesses were grouted in after the columns were installed. They were grouted in before the T's were added.

Dik

 

[KootK]

Details are always fun. I doubt you'll go with the bucket but, if you do, I actually have canned capacity tables.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[KootK]

Just watched the Peikko vid. That looks slick. Groovy music too.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[JStructsteel]

Decided to use grout tubes. Basically a corrugated 3" tube in the foundation that the bar is inserted in and grouted. Should work out fine