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for waht a slip joint: between top of wall and ring beam ?

for waht a slip joint: between top of wall and ring beam ?

for waht a slip joint: between top of wall and ring beam ?

(OP)
Hi

some engineers are specifying a slip joint (2xplastic sheets) between the ring beam and the top of the brick wall.
For what is it good?

Is the idea of the ring beam not to tie together the entire building? and now we basically allow the ring beam to move on top of the walls?
will the wind not move the beam on top of the walls?

Shall we not rather remove this plastic?

lolobau

RE: for waht a slip joint: between top of wall and ring beam ?

ACI just did a webinar on this kind of stuff yesterday.

I may be wrong, but I would think it is to prevent the brick (block?) wall from resisting the shrinkage stresses from the ring beam and floor slab. You allow the shrinkage to happen but it doesn't put stresses on the walls.

RE: for waht a slip joint: between top of wall and ring beam ?

(OP)
Hi Jayrod

this could be a reason, I agree but are you not loosing much more here then winning?
ok the shrinkage cracks will be eliminated but now your entire wall is actually "not fixed" on the top

Lolobau

RE: for waht a slip joint: between top of wall and ring beam ?

The way the details appeared to work was there are still dowels into the ring beam but they were provided with a compressible wrap that allowed the lateral movement expected by shrinkage. It keeps the wall pinned from failure but allows the temperature and shrinkage to happen without developing restraint stresses.

I wasn't totally sold on the idea, but their argument had some merit. I just need to ponder it further.

RE: for waht a slip joint: between top of wall and ring beam ?

Check out the new ACI 224.4R.

RE: for waht a slip joint: between top of wall and ring beam ?

(OP)
Sorry I don't have the ACI 224.4R available what does it say?

Dowels? hhmm.. ok then it would make bit bit more sense but if my entire ringbeam is as a solid beam with no joints no dowels?

Lolobau

RE: for waht a slip joint: between top of wall and ring beam ?

I mean dowels from the block wall into the ring beam.

I don't have it either but I watched a webinar they gave on it.

I don't believe I'm allowed to post the slides from the webinar here.

RE: for waht a slip joint: between top of wall and ring beam ?

@Jayrod: What did you think of the webinar and, by way of extrapolation, the document? I was registered but failed to attend.

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.

RE: for waht a slip joint: between top of wall and ring beam ?

Without spending too much time going into detail,

Some of the points they brought up were interesting. As far as the slab-on-grade detailing they were proposing it was no different than the industry norm as far as I know.

The details they were showing to address shrinkage in structural slabs was different.

In broad strokes the webinar basically said "Concrete will shrink, if you restrain it then you could have cracking in the slabs, supports or both. Try to allow the slabs to shrink (either via temporary or permanent releases) but still provide your structural integrity you require."

So in my mind it's just another document telling you to think the whole process out or accept the consequences.

Maybe I'll look at putting together a more thorough review when I'm not on the clock.

RE: for waht a slip joint: between top of wall and ring beam ?

That's more than I was expecting Jayrod. Excellent/crappy would have sufficed. No need for revision.

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.

RE: for waht a slip joint: between top of wall and ring beam ?

(OP)
so what now? plastic or not? hhmm...

RE: for waht a slip joint: between top of wall and ring beam ?

Depends on your end goal I guess and the owner's desires.

IF some cracking in the slab and possibly the walls is deemed acceptable that by all means omit the release details. If the cracking is "forbidden" then you'll need to provide some sort of shrinkage release mechanism to reduce the chances of unsightly cracking.

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