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Nottingham UK car park COLLAPSES

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Lucky it happened in the early hours when the place was deserted. The title is a little misleading, a catilevered section of a car park collapsed.

Hypothesis: the structure has been weakened by numerous small impacts from vehicles nudging the wall cast upon the cantilevered section. It doesn't look like it is really designed to take that kind of impact, although it should be a reasonably forseeable event to accommodate within the design.

Of course I could be completely wrong.
 
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I was thinking maybe with all the parking sensors more people were parking closer to the back edge. Maybe design was based on the wheels not going past the main beam structure? The slab looks pretty thin for a cantilever of that size.

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Looks like quite a clean break where the cantilever fell off. No dangling reinforcement. Maybe the bars are all corroded away. A closeup photo would be interesting.
 
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Good point, LittleInch.

I'm not sure when that car park dates from (the 1970's?) but I could pretty much guarantee that vehicles of today are heavier than those which were commonplace at the time of construction.

Yes, the cantilevered slab looks very thin to these non-structural eyes.
 
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It is an old garage, it would not surprise me if over the years they did away with the original wheel stops. You don't always see them in newer garages today but back when this was built, they were popular. At least here in the US.
Good video Link
Large Photos Link
 
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It makes you wonder how it was held up. The upper floors look like they ate made from narrow precast beams and the cantilever was poured on site, but clearly as an addition to the main structure.

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No, it was all cast in place, and I think all at the same time. Those are concrete joists, made by using prefabricated pans as forms. The joists are tapered at the ends in the high shear area.

Past the spandrel girder in the cantilevered section, only a relatively thin slab was used, and as I pointed out above, not much reinforcement can be seen.
 
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hokie66 is right - those sure look like cast-in-place pan joists.
And no sign of any significant top slab steel to serve the cantilevered slab - unless the few bars sticking out on the right of this photo represent what was provided.
Either they were terribly detailed, installed or corroded directly off at the cantilever launch point:
Garage_photo_y8xteq.jpg


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faq731-376
 
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I read one comment on one of the UK news sites that another garage had been demolished just 15 years after it was built due to rebar corrosion. The poster suggested a bad batch of rebar was the cause. The slab looks like it has a remedial (rebar depth) topping in some areas..., delamination. Could they have been using a Calcium Chloride accelerator to speed construction back then?
URL]

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Calcium chloride could certainly have contributed. There was a lot of use of corrosion causing calcium chloride in cold climates when that garage was built.

Bad batch of rebar? I don't think so. Whatever it is, probably just not enough of it, and now none left.
 
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In a similar failure of a sidewalk that was cast at the edge of an existing bridge that used re-bar to peg the cast section, there was ample staining indicating the re-bar had been corroding for a long time. Salt and water had essentially sliced the re-bar at the gap between the walk and the bridge. Fortunately it let go at night and only one car was affected - a new driver who slowed enough when the full width of the highway was suddenly blocked.

I think the remainder was re-anchored with more re-bar, maybe fiberglass, epoxied in place to avoid corrosion.

The highway dept just assumed that since the rust stains had been there for a long time that everything was stable.


The photo is of the temp solution - counterbalancing the remaining sidewalk and closing off the opening.
 
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2DD:
We had a problem like that south of Winnipeg with repair using FRP reinforcing... and the crack developed at the end of the FRP material. Termination was all at the same location... no staggering of reinf. Was headed to court, but, don't know what happened.

Dik
 
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Dan, have a look at photo 19 in the link posted by epoxybot. I would guess 30' from that picture. But anyway, you have to expect exaggeration from reporters.
 
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IRS... 29' 6-3/4", for sure... <G> It's been a slow day...

Dik
 
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LOL, you guys make me laugh. :-D

I agree it's about 9m to the bottom of the fractured slab, so 30' or so.
 
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The point, I think, is that someone, even a reporter, can do essentially the same thing, i.e., measure the height of the Ford Tournedo in the image, and use that height to figure out the height above ground. Not much more than about 4th grade math to do the calculation.

That said, however, a more complex version of that managed to stump a more than few students in freshman physics at my school.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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Even if the reporter did the calculation correctly, it would still be reported wrongly. In all the cases where I have been personally involved, the reports have been wrong.
 
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