Slab to wall connection using inserts or pull-out bars 1

[asixth]

Hi guys

What is everyone's opinion about moment transfer thru a slab-wall connection using either threaded reinforcement inserts (pull-out test certified to exceed 100% of the bar capacity) or proprietary cast-in pull-out reinforcement systems.

I am happy when using cast-in U-bars or L-Bars with the cogs facing inwards to the joint but I just want to get some clarification on this detail.

I have test certificates to show the anchorage of the slab reinforcement into the wall is sufficient and can prove the moment is transferred to the wall thru the joint by strut-tie. Ideally I would like the cast-in pull-out bar system to extend to the inside face of the wall reinforcement but the systems are not fabricated that way.

Opinions will be appreciated and any references for research will be appreciated.

 

[Teguci]

Specifically it's not the moment that is transferred but the tension. As for hooked bars into a wall, you have to check Ldh for development. Many detailers don't have full development for these hooks (do you really need full development?) As for the inserts, there is a professional requirement that we do due dilligence for new types of connectors that we incorporate. You will want to read the ICC-ES report confirming its testing evaluation meets your requirements.

 

[rowingengineer]

Asixth,
I don't see how the cast in detail does any more than take the tension into the wall. There is no detail to get the force from the anchors into the wall reo to tranfer moment, thus the only force I can see transferred is shear and tension no moment.

I have marked up what I think and attached.

Teguci,
We are in Australia what is the ICC-ES report?

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[rowingengineer]

I also attach the reid bar design manual, take a look at the detailing for the RW wall with regard to the insert (page 9) for some food for thought.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[hokie66]

The details look fine for bearing a slab on a wall, but I don't try to design this connection for moment. Moment joints in thin orthogonal elements of concrete structures are not very efficient in practice, so are best considered as pinned.

 

[rowingengineer]

Can't disagree with that wisdom, But I do like a small recess for bearing.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[hokie66]

Oh, I certainly agree and insist on the recess as shown on apsix's details.

 

[asixth]

Thanks for everyones input, the use of the prefabricated systems seems to be more trouble then their worth.

The pullout bar systems are premanufactured sizes which are not fully compatible with the wall design. The inside vertical reinforcement is 200mm clear of the rebate but the U-bar's are detailed 150mm long so it doesn't quite reach to vertical reinforcement.

The threaded inserts are only 118mm long so they are even further from the wall reinforcement.

From the strut-tie models I developed it is clear that the U-bar is the method to detailing the slab-wall joint, but the strut-tie model for the pull-out bar and threaded insert still works but allows more rotation at the joint for the greater stresses in the compression zone.

I am going to detail L-bars cogged inwards with reinforcement couplers at the rebate and be done with it. It is the only way I see this design working.

The only other methods I can think of are blockout's during the wall pour so in-situ connection can be made with the presence of a cold joint?

Thanks

 

[hokie66]

Why are you trying to develop the top bar? I prefer to design these connections as pinned, and use centrally located bars. Danley can make reboxes in a number of ways to your specification, including with couplers.

 

[rowingengineer]

The rebox is a easy method for vertical formwork, The u bars would be difficult in this setting but not impossible.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[DST148]

@asixth: Late on this thread. We adopt the first option you have suggested in your last post for super structures only. We adopt the second option you have mentioned in your last post for work below grade.
Many times we encounter a similar situation when there are two levels below grade, subcellar and cellar. The contractor doing the foundation work is generally not highly specialized. His scope of work typically includes the foundation proper and the foundation walls.(the shell)
We keep the subcellar walls at least 3" to 4" thicker than the cellar walls. The foundation walls are poured to the underside of the cellar slab with projecting ell-shaped slab dowels. The contractor then installs the forms for the inside face of the wall starting at a level of the top of the cellar slab and supporting it by lumber, with block-outs at slab dowels.
This way there is a continuous ledge for the cellar slab and the slab moment can be transferred to the walls. Since the foundation walls are thicker than the slab, transferring slab moment is not that difficult.