Post Installed Rebar as Anchorage 1

[ScratchyFilm]

I was doing a bit of research this morning and see that deformed rebar can be post installed using the same design criteria as anchor bolts.
My understanding of anchor bolts is that you are always designing them using tension and shear forces for the failure methods. In the attached image, there is a case where there would be moment on the corner of the vertical column... Would design of post installed rebar using anchoring principles work for a case like this, or does a moment force change the requirements for the development of the rebar?

Additionally, when you guys design post installed rebar like this, do you just take the recommendations of the supplier of the adhesive for necessary embedment depth?

Thanks in advance!

 

[JoshPlumSE]

That should only be designed as a "pinned" joint.

The post installed bar would be designed for shear and shear cones and such. If there is any tension in the connection, then the bar would be designed to resist that as well. But, the bar should NOT be designed to resist moment.

 

[ScratchyFilm]

Thanks for the reply Josh,

I understand what you mean by treating as a pinned connection and designing for shear -- maybe you can help me understand by elaborating a bit more.
I should have been more clear in the sketch... The vertical column is actually just a free standing wall. So this would be treated as a cantilever beam for the lateral loads. In this case, whatever moment exists could be translated into (Tension Force X Moment Arm) for loads acting on the rebar, correct? Would you not essentially be designing for the moment, too?

My initial reaction thinks of a tall tower that would be pinned to a base plate with anchor bolts. There would be lateral wind loads (moment) that are translated into tension loads that are resisted by the anchor bolts into the foundation below.

Thanks!

 

[STrctPono]

There is a big difference between the philosophy between a post-installed adhesive anchor and a post-installed adhesive deformed dowel bar. The former follows ACI 318 Chapter 17, has many behaviors that need to be checked, and is complicated. The latter, strictly speaking, only needs to follow rebar development length requirements. In other words, you should not be using ACI 318 Chapter 17 to design post-installed adhesive deformed dowel bars. You should use the manufacturer's provided values to ensure that you have enough embedment to develop the capacity of the rebar in tension.

 

[struceng.id]

@ScratchyFilm,

You may design the rebar anchor in accordance with ACI318-19 Chapter 25- Reinforcing Details (or whatever chapter it is in your ACI318 version). You basically just have to provide the required rebar development length on both side of the failure plane. ACI318-19 Section 17.5.2.1 states:

"The design strength of anchor reinforcement shall
be permitted to be used instead of the concrete breakout

(a) For tension, if anchor reinforcement is developed in
accordance with Chapter 25 on both sides of the concrete
breakout surface
(b) For shear, if anchor reinforcement is developed in
accordance with Chapter 25 on both sides of the concrete
breakout surface, or encloses and contacts the anchor and
is developed beyond the breakout surface."

Does this help with your question?

 

[JoshPlumSE]

I don't like relying on a cold joint like that for moment resistance. While I've had a situation like that in the past (for something akin to a basement wall), I believe I always designed the wall as a two-way plate. Meaning the bottom joint was pure shear. But, the wall also spanned horizontally to the end walls.

Technically, you can probably get away with moment resistance at that connection. But, I don't like to do it.

 

[chris3eb]

@Josh
What would make you not want to count on this for moment? It seems like a simple T/C to me with the bar in tension and a concrete compression block? If there would be a problem with any action, I would think it would be shear if the joint wasn't prepped well enough and there wasn't enough vertical load to give you enough frictional resistance. If it was at a hinge subject to cyclical loads, I could see it being more of an issue, but that wouldn't be the case for out-of-plane loading on a wall.

 

[JoshPlumSE]

Chris3eb -

That's a good point about the shear. When I've done this type of joint in the past it's typically looked a little more like the attached image where the interface is roughened and prepped to be a better shear joint.

Regardless, I don't like using a single bar at the center of a wall as moment connection joint. If we had two bars at each face, I'd say fine. I'm sure the tilt up folks must do this for their more narrow walls. But, that doesn't mean that I have to do it. Especially for a cantilever wall with no redundancy.

 

[JoshPlumSE]

The note in the image was my attempt to label that joint with a note to roughen the surface prior to the 2nd pour. However, I realized my software wasn't up to the task and I was too lazy to use a different software.