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Nottingham UK car park COLLAPSES

Nottingham UK car park COLLAPSES

RE: Nottingham UK car park COLLAPSES

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.

RE: Nottingham UK car park COLLAPSES

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.

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

RE: Nottingham UK car park COLLAPSES

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.

RE: Nottingham UK car park COLLAPSES

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.

RE: Nottingham UK car park COLLAPSES

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

RE: Nottingham UK car park COLLAPSES

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.

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

RE: Nottingham UK car park COLLAPSES

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.

RE: Nottingham UK car park COLLAPSES

(OP)
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:

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RE: Nottingham UK car park COLLAPSES

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?

RE: Nottingham UK car park COLLAPSES

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.

RE: Nottingham UK car park COLLAPSES

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.

http://photos.mycapture.com/STLT/237605/14274939E....

The photo is of the temp solution - counterbalancing the remaining sidewalk and closing off the opening.

RE: Nottingham UK car park COLLAPSES

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

RE: Nottingham UK car park COLLAPSES

Article says "a 50 foot drop below"... the pics could certainly obscure it, but I'm seeing closer to 20', not 50.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Nottingham UK car park COLLAPSES

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.

RE: Nottingham UK car park COLLAPSES

IRS... 29' 6-3/4", for sure... <G> It's been a slow day...

Dik

RE: Nottingham UK car park COLLAPSES

LOL, you guys make me laugh. big smile

I agree it's about 9m to the bottom of the fractured slab, so 30' or so.

RE: Nottingham UK car park COLLAPSES

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)
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RE: Nottingham UK car park COLLAPSES

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.

RE: Nottingham UK car park COLLAPSES

Okay, didn't see the second link, so I missed the extra "floor" below the pics shown in the first link. I'd estimate around 30', too.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Nottingham UK car park COLLAPSES

If you look really closely there's evidence there that the joint between the car park and the cantilver has been repaired. The screed under the laguna ( the black car) looks quite new compared to the section around the column.

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

RE: Nottingham UK car park COLLAPSES

LittleInch (Petroleum)
I thought the same. Plus the way it cleaved away smoothly, suggesting a topping mix with small pea gravel aggregate, compared to the coarse break of full sized aggregate used during the original concreting around the columns & elsewhere. Efflorescence suggests there may have been a full depth cracks for some time. Make me wonder if the cantilevered section was a historic low spot and bird baths pooled along the wall when it rained.

RE: Nottingham UK car park COLLAPSES

With the cantilever "removed" - the frame looks like the first level. In order to keep the formwork and shoring of the main parking deck the same, maybe there was a cold joint at the cantilever.

RE: Nottingham UK car park COLLAPSES

Makes one wonder what kind of repair work was going on. Hopefully not urethane injection. The scaffolding may be what's holding up the rest of the cantilevered section. I was surprised how little damage it sustained when the section of concrete came to rest against it but it is jacked in place against the cantilevered concrete. Link

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