Adhesive Concrete Anchors into Construction Joint

[ToadJones]

Is there any issues to consider should an adhesive anchor wind up being located in a construction joint between a wall and a floor?

 

[hokie66]

I don't think so, if the anchor is in shear.

 

[Ron]

Screws up your edge distance considerations. If in tension, not a good idea.

 

[MiketheEngineer]

Yes - Probably OK in shear - tension quite doubtful - CALL THE MFG and ASK!!!!!

 

[TXStructural]

It you end up relying on the adhesive for tension / withdrawal resistance, expect 1/2 or less of the capacity expected. As the two sides of the crack move apart, research shows that the adhesive will probably stick to one side and separate from the other. The result is a reduction on the order of 50%. For tension, consider undercut anchors and always use values for cracked concrete.

 

[Ron]

TJ...Assuming you are the engineer on this and a contractor has installed them thusly...

one other consideration...liability.

If you specify the anchor outside the manufacturer's tested parameters, YOU take on the responsibility for the performance. If the contractor installs it outside your specification and the manufacturer's recommendations HE takes on the responsibility for performance.

Better HE than YOU! Write a letter and reject the application...then let the contractor sort out a revision with the manufacturer. You still get the opportunity to decide yes or no, but it somewhat removes you from the liability stream...at the least it puts you in a boat on the stream, not swimming against the current!

 

[msquared48]

Seems to me that the construction joint will want to expand and conrtract by nature.

The expansion will be locally prevented by the bolt causing spalling, and when the slab contracts, the pullout will be negated and any shear capacity greatly reduced.

Relocate the anchor.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

Some of you obviously have a different mind picture of the construction joint than I did. I didn't think the joint was subject to moving.

 

[MiketheEngineer]

OH YES - construction joints move!!!

 

[hokie66]

A construction joint is a straight crack. Other than the possiblity of shrinkage cracking in the other direction due to movement parallel to the joint, there should be little difference between installing an anchor in a joint or in any surface subject to cracking. Assuming the bolt bears on one side of the joint, I don't think there is a problem in shear. In tension, I don't use adhesive anchors.

 

[ToadJones]

My concern was hitting a possible cold joint in a concrete wall or column, but I am not even certain that there could even be a cold joint in a column or wall?
Column is roughly 35' tall with a second floor at 20'. It looked like there was possibly a cold joint in the column just above the second floor but I would have thought the column was poured full height before the second floor was poured?

Excuse the extreme ignorance here...I do not work in concrete much other than foundations.

 

[Ron]

TJ...yes, there can certainly be a cold joint even if the placement was "continuous". Continuous to a contractor is "on the same day"!

 

[hokie66]

Toad,
In the normal course of casting concrete structures, there would be a construction joint in the column both above and below the floor. In other words, the part of the column within the floor depth would be cast with the floor.

 

[ToadJones]

Well if this is the case, what are your thoughts if the anchors is in a cold joint? Same as in a construction joint?

MiketheEngineer...I absolutely promise you I will call Hilti tomorrow. I swear.

 

[hokie66]

A construction joint at the column to floor junction is just part of the concrete, same as if cast monolithically. You don't cast the columns and floor monolithically, because you have to allow the first pour to settle and harden. If it is only in shear, the anchors should be fine.

A cold joint, not intended? In a column, it should be treated the same as a construction joint, i.e. the surface clean and rough before casting above, but the problem with that in construction is that the forms have to be removed. Cold joints in columns should be avoided. Why do you think you have a cold joint?

 

[ToadJones]

It visually appears that there might be a cold joint, but it could just be a mark left from form work.

Hokie you say "In the normal course of casting concrete structures, there would be a construction joint in the column both above and below the floor"

How far above and below should I expect to see the "construction joint"?
Would this joint be a clean joint or just a cold joint?

 

[hokie66]

The column should be cast to the slab/beam soffit, then the floor placed, then the column above. So the construction joint is at the bottom and top of the floor construction. It is just stacked, not connected to the side like in steel construction.

Clean or cold? The construction joint should be both.

Yes, what you thought was a cold joint in the column may well be where the formwork butted.

 

[ToadJones]

I feel like an idiot even talking about this.

I need to hit the books for concrete building construction.
I have never had an opportunity to work with concrete buildings in the firms I have worked for/with or in my own work.

 

[TXStructural]

Toad, visit the CRSI.org website. We have some online info, and through the webstore, you can download (FREE) our Tech Notes highlighting things like adhesive anchors, economical concrete designs, and construction practices. You will have to supply a name and email for the webstore, but the notes are free to download as PDF once you are inside.

 

[ToadJones]

thanks....will do.
You work for CRSI?