Expansion joint spalling

[rowingengineer]

These are photos of an underside of a concrete slabs and beam system. The building is for a warehouse and is single storey.

The expansion joists are located roughly 1/3 span from the columns and all have spalling of the concrete at the joint.

Anyone crossed paths with something similar and know the cause of such spalling?

Please note I just happened to park below said slab, I have no drawing of the structure or abilities to do more tests etc.

 

[KootK]

What's the nature of the slab between beams? CIP? Precast Plank? Composite steel deck? I'm struggling to get a visual read on it.

What's your guess as to the nature of the joint? Double dap?

 

[JedClampett]

It looks like the joint is pretty small, maybe zero space between members. If the shallow cantilever beams deflected, as shallow cantilever beams are prone to do, the the tops of the beams could of pressed against each other and spalled.
Don't park under any of them that haven't spalled yet. Someone's eight thousand lb. Bentley could push another one over.

 

[dik]

I could see if it weren't a real joint that the compression at the top from the deflection of the cantilever... is there any sort of joint material? If there is, I cannot suggest a cause.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[KootK]

If there's a ledge on the sides of those beams, then I wonder if water isn't condensing/collecting there and initiating deterioration with the expansion joint just being and especially good water trap relative to the rest of the ledge in general.

 

[r13]

Is the black stuff joint material, or...? The parking is heated or not?

 

[Retrograde]

If this is an expansion joint, I think the issue is that the joint in the (metal deck?) slab does not align with the joint in the beams.

 

[Ingenuity]

The ubiquitous Bunning Hardware parking structure...as common as an Aussie BBQ!

If you notice it is also happening at non-CJ locations too:

A somewhat related thread was discussed recently: thread507-477153

 

[hokie66]

I doubt that this was intended to be a movement joint. Rather, I suspect it is a construction joint, done poorly. Can you tell if the bands are post-tensioned? You might have to be able to see the ends of the bands to determine.

Another thought is that the joint could have been made with a dowel system (Ancon or similar) which is supposed to allow movement, but sometimes doesn't.

As for the black spots which Ingenuity highlighted, I have no idea.

I would report this to the local building authority as an interested member of the public. The building is not very old, so details of the design engineer and builder should be readily available.

 

[hokie66]

For those who don't know, rowingengineer is in Queensland. No freezing, no heating, except it gets very hot here in the summer.

The deck is cast in place on metal deck. Maybe composite decking, maybe not. Maybe a ledge for the deck bearing, maybe not. It doesn't look from the photos that it is possible to be a corbelled/dapped joint...not enough depth.

 

[r13]

hokie,

Hot, in hand with humid and expansion/contraction could be the poison

 

[Retrograde]

The beams may have been constructed using precast beam shells. I have seen a Bunnings where they used those with hollowcore planks. The joints you can see may be the joints between the individual shells.

 

[hokie66]

Interesting, Retrograde. But we will have to hear from rowingengineer as to how far apart these joints are to know if that is possible.

 

[Agent666]

In NZ we also see similar support ledge damage highlighted by Ingenuity if there is sliding between the base of the deck and support ledge due to 'frame' action perpendicular to the band beam span under lateral loading. Though never seen it with metal decks before to be honest (but we don't have a lot of metal decks supported on concrete, and even less PT used in building construction. It's more of an issue observed with deeper hollowcore type floors where no bearing strips have been used. Given it's Australia there may be no real lateral system orthogonal to the beams.

Could be something similar in nature, with some lateral movement of the sturcture orthogonal to the beams, which in turn cause some relative movements at the interface between deck and support that leads to spalling of the support edge.