Strange concrete beam "splices"

[jerseyshore]

Came across a very strange condition on the lower level of a parking garage. Plank floor on what appears to be CIP beams.

An entire row of concrete beams down multiple bays appear to be spliced, or maybe not-so-spliced. There are clear cuts with no visible reinforcing spanning the gaps.

The locations of these cuts is equally weird. And it doesn't seem super intentional since you can see the stirrup exposed right at one of these locations.

Any thoughts at all here? Has anyone seen anything like this before? What the hell is holding these things up?

 

[Just Some Nerd]

I have no idea what's happening here but my gut tells me something is either horribly, horribly wrong, or it's perfectly fine and these beams are meant to be discontinuous at a joint in the slab

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Why yes, I do in fact have no idea what I'm talking about

 

[driftLimiter]

Seems like trying to do a kind of propped cantilever support for the adjacent span to be pin connected. The crack in the last picture looks like a flexural crack maybe due to lack of compression reinforcement and maybe unforeseen negative flexure??

Some kind of a dapped beam connection perhaps. Hoping someone here has some idea about this its very curious.

 

[hokie66]

Maybe something like these embedded shear connectors. Not something I would do, but some 'hero' engineers might.

https://www.ancon.co.uk/products/shear-load-connectors

 

[bugbus]

The beam in the last photo does not seem to like what's going on.

When you have cracks wide enough to stick a finger in, it's normally a sign something isn't working properly (I'm thinking of FIU pedestrian bridge).

The joints look suspiciously as thick as a piece of form ply. I wonder if there was some reason that the whole length of the beams could not be cast at one time, so the beam mould was formed up halfway along with some shear connectors, the intention being to cast the rest at some later point? Then for some other reason, they went ahead and did the whole lot and forgot to take the internal forms out? Just speculating. Would explain why one of the stirrups is so close to the gap.

 

[Tomfh]

Looks dodgy. You can see straight through some of those gaps!

We’ve come across this scenario before, and the long beam eventually started sagging badly. There was simply no support!

 

[HTURKAK]

My opinion is , embedded shear connector with shear box or shear dowels ...The use of scarf joint ( in this case embedded ) is chosen to create a negative bending moment at the column and reduce the depth of the beam.

I do not think this is a recommended practice..

Pls have a look to the following doc , Heavy-duty shear dowels From Page 13 to see the concept . In this case , probably the shear connection designed with reinforcement only..

https://www.halfen.com/PDF-Dateien/...e Produktinformationen/HSD-EC_Leviat_10-E.pdf

Not to know is bad;
not to wish to know is worse.

NIGERIAN PROVERB

 

[jerseyshore]

What's weird is that this only happens in one bay of beams all the way down the building. It's not like we have a steel roof drop-in cantilever beam setup where there is a consistent pattern along a girder line. It's just in the first bay.

 

[Just Some Nerd]

What's going on where the slab means the beam - is the floor constructed with panels?

Also, where are the shear connectors in these beams? Can't spot any, are they just located relatively high?

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Why yes, I do in fact have no idea what I'm talking about

 

[hokie66]

Yes, those are precast slabs, probably hollow core. Obviously, whatever shear connection there is is out of sight. Perhaps something like these, as I suggested before.

https://www.ancon.co.uk/products/shear-load-connectors

 

[Just Some Nerd]

Obviously, whatever shear connection there is is out of sight. Perhaps something like these, as I suggested before.

Familiar enough with ancon connectors (the brand name is basically used as the generic term, bit annoying at times), just figure that they would be far easier to spot than whatever is going on in this thread lmao

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Why yes, I do in fact have no idea what I'm talking about

 

[jerseyshore]

I looked it up and it was built in 1983 if that helps anyone.

Since I don't do a ton of concrete design, what are those embedded shear connectors used for generally?

We didn't have a ladder so couldn't get the best photos, but I do want to go back there with a good flashlight to actually see what is tying the two beam pieces together.

 

[hokie66]

The company says they are intended for shear connections of concrete beams, like the ones in your photos. And their web page gives a link to a design program, which I haven't used, and don't intend to do so.

 

[Tomfh]

The shear connectors are glorified dowels. You use them to carry a shear load across a movement joint. They provide the same function as a corbel; one side of a joint supports the other side.

 

[hokie66]

That crack near the top of your last picture looks like a prying failure. That distress would concern me more than the other photos.

 

[jerseyshore]

Our office didn't even go out here to look at this either. We were doing an overall assessment to see if it was feasible to demo the 4 story office building on top of this and build a new 4 story apartment building. I gotta get back out here and get a better look at these joints though, strange stuff.

 

[Brad805]

Given the era I would guess you might find a Cazaly hanger buried in the middle of the beam. None of the modern connectors like Tom shows existed then, so they would build them in their own shop.

 

[Tomfh]

Cazaly hanger makes sense, as there doesn’t appear to be any shear connection in the beam web.

 

[jerseyshore]

Just googled that, interesting connection. It's not used anymore right?

Would be strange to only use that in one bay and not the whole garage but who knows.

 

[Just Some Nerd]

Well that can certainly explain why it's hidden...that beam in the last pic is hanging by a thread

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Why yes, I do in fact have no idea what I'm talking about