Yet another balcony collapse 1

[LittleInch]

See the link below as the original one was updated.

If you click on picture and zoom you can see that it just looks like the frame of the balcony was just bolted into the skin of the building.

Reports that 18 people were on the balcony when it collapsed. Any French speakers might be able to get more info?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[VEBill]

Updated link:

https://www.theguardian.com/world/2016/oct/16/balcony-collapses-housewarming-party-angers-france

 

[ScottyUK]

The concrete appears to have only light gauge mesh reinforcement in a single layer, and to have been cast separately given the clean break. Lots of black mould / damp on the wall where the top balcony let go.

 

[hokie66]

Scotty,

Where did you see an indication of reinforcement in the concrete? I can't even tell from the picture whether the balcony was concrete or not.

It looks like whatever the construction of the balcony slab, it was essentially a "cantilever" with a pinned connection at the building. The rods, anchors, whatever...just pulled cleanly out, or corroded away at the face of the wall...hard to tell from the picture.

 

[BigInch]

All of them broke so cleanly it looks like a completely cold jointed cantilever.
With 18 people on that little thing you wouldn't need any corrosion. I don't see how you could fit 18 people on that.

 

[JStephen]

It looks like the balcony that fell was longer than the remaining balconies at the right- those are just by the door, the one that fell included a door and window adjacent to it.

 

[itsmoked]

Just this afternoon my better half and I looked at the boob-tube just as a gal walked out onto one of those lame little balconies and I told her, "These days balconies like that give me the creeps". She agreed with my sediment.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Hokie,

There are short stubs of something which I assumed was reinforcement wire protruding from the wall where the upper balcony was attached. There are no such little wires on the lower balconies. I'm still not 100% convinced whether this wall is brick or concrete, but the fractured parts look like concrete. There's a reason why I'm not structural! Any thoughts how this was attached to the wall?

 

[hokie66]

Scotty,

You may be correct about those wires. But they seem to be just from the bottom, which wouldn't be helping much anyway. The top is in tension.

My guess is that the wall is concrete, and the balcony was concrete. The balconies were built last, not with the internal floor. How they were attached is...poorly. Maybe drilled in anchors, which were assumed to do a lot more than they did. And no keying into the wall for shear.

 

[LittleInch]

Following one of the links I fond this video

http://www.francetvinfo.fr/faits-di...matique-effondrement-d-un-balcon_1875369.html

Live through the advert and then about 1:30 into the video they have close up of the failed sections.

There appears to be a very thin single mesh holding it all together. Looks like the standard water in behind the slab joint rusting the mesh.

Reminds me yet again that I have never like balconies where I can't see the connection braces.

Also don't go out there with lots of people on it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ScottyUK]

Ha - I am vindicated.

Thanks LittleInch.

 

[hokie66]

I should not have doubted that a sparky would know wires when he sees them.

 

[ScottyUK]

 

[msquared48]

And judging by the position of the drain in the photo, any water was encouraged to drain toward the supporting wall rather than to a gutter at the outboard edge - obviously for Architectural reasons. Water had seeped at the construction joint for some time here, deteriorating the little reinforcing steel present. Additionally water staining or mold growth above on the wall and in the construction joint can also be seen.

This was just a failure waiting to happen that was driven by Architecture... again.

Mike McCann, PE, SE (WA)

 

[drawoh]

What was all that black stuff on the top right hand side of where the balcony was?

--
JHG

 

[msquared48]

That's what I am talking about - looks like black mold and dirt from being wet. Same thing we get in the Pacific Northwest.

Mike McCann, PE, SE (WA)

 

[Spartan5]

Mike,
RE: "driven by architecture"... I'm not a structural guy, nor do I really care about defending architects. But just from the "little I know of concrete and steel" standpoint, that structure seemed woefully inadequate; regardless of complications from moisture. No?

 

[BigInch]

Not enough bars for sure and the depth of the slab looks very thin. It's the cold joint that I really don't like. No supporting beams at all. Just a thin, projecting slab, which would have been bad enough, even if poured integrally. The main floor should have been extended to make up the balcony floor too, not try to join it after the floor cured. Not even any roughing up of the wall surface before they added the balcony slab.

 

[jayrod12]

Spartan, you are correct that the structure was inadequate. However, regardless of the amount of reinforcing you threw into that joint, or the thickness of the slab (to a degree), actively inviting water towards that joint is a horrible idea and an accident waiting to happen. Even if poured integrally, a crack would've opened up on the top of that joint, water would've entered, and sooner or later it would've failed.

Always slope balconies away from the building.

 

[BigInch]

The other balconies look like they are draining away from the building, but only because of deflection.