Berkeley Disaster

[Diable Rouge]

Six Irish J1 students dead after a balcony collapsed while they were celebrating a 21st

[ursus arctos]

Berkeley Disaster

What a horrible story.

Condolences to all of the families and the Irish community in the Bay Area, which is quite tightly knit.

The building in question is relatively new construction in a part of Downtown Berkeley (right by the BART station) that has been gentrifying.

No one knows yet how many were on the balcony when it collapsed, but it doesn't look like it would take that many



Article from the Daily Cal

[Incandenza]

Berkeley Disaster

Sadly, these balcony collapses at apartment buildings near college campuses are a common occurrence. I remember about 10 years ago there were numerous ones near UCLA (perhaps not with death tolls this high).

[linus]

Berkeley Disaster

It's a bit ironic given the consistent drought conditions in CA, but initial reports indicate that the structural failure is a result of poor waterproofing having rotted the balcony's joists. I wonder if those poor kids were just taking a breather on the balcony, or if that big group had been jumping in unison.

[WOM]

Berkeley Disaster

Balcony is rated for 60 lbs per square foot. It would be generous to say that balcony is 15 square feet. From the deaths and injuries, it suggests 12 people were on it.

So that would be, on the low side, about 100 to 110 pounds per square foot, jumping or wood rot aside.

[Borracho]

Berkeley Disaster

The New York Times has published an absolutely appalling article today which attempts to somehow connect this tragedy to stories of other Irish J1 students engaging in pissed-up hijinks in California. I'm not linking to it.

[Borracho]

Berkeley Disaster

By the way, Dublin is full of apartment blocks containing jerry-built balconies that were slapped together by opportunistic shitbag developers during the boom.

[WOM]

Berkeley Disaster

Two or three noted balcony collapses come to mind around things like this, and they always happened during house parties. They're simply not engineered to hold 16 or 18 or 24 people. More like 8 and some patio furniture.

Holmes on Homes did an episode where a (Canadian) east coast woman was left crippled when hers collapsed. It was held up by four lag bolts; two of which missed the studs they were meant to connect to.

[Flynnie]

Berkeley Disaster

J1s have an increasingly bad reputation in the US and it's deserved. But ignoring that NOBODY DESERVES THIS, it doesn't seem like the balcony they were on was up to snuff.

Balcony is rated for 60 lbs per square foot. It would be generous to say that balcony is 15 square feet. From the deaths and injuries, it suggests 12 people were on it.

So that would be, on the low side, about 100 to 110 pounds per square foot, jumping or wood rot aside

The BBC is claiming it's a five x ten balcony, so that would be fifty square feet. Previous Berkeley code was 60 lbs per sq ft, but apparently recent California code is 100 lbs per square ft.

At 60 lbs per square feet, 12 people would each have to weigh 250 lbs (113 kg, 17 st 12) to get to 3,000. Jumping and dancing would add to the load.

So they were giving the balcony a hard time, but there's a long way from that to it collapsing without there being dry rot or shoddy construction.

[anton pulisov]

Berkeley Disaster

60 lbs/ft2 is equivalent to 2.87 kN/m2.
100 lbs/ft2 is equivalent to 4.79 kN/m2.

I looked up the EU building code (EN1991) and the figure for balconies is 2.5 to 4.0 kN/m2, depending on the situation. And I think the figure used is always multiplied by a safety margin of 1.5 (but it is over 10 years ago since my short foray into Civil Engineering).

So it seems that the American building code is up to scratch.

2.5 kN/m2 is basically 250 kg/m2, with safety margin of 1.5 it's 375 kg/m2. Average person weights 75 kg, and BBC says the balcony is 50 ft2 (4.6 m2). So you'd need a total of 375*4.6/75 = 23 people on the balcony to make it collapse*.

Jumping up and down doesn't have as much of an effect as you'd think it does, unless they were all doing it exactly in unison.

When the authorities conduct investigations into these kinds of disasters, the engineer is usually found to be beyond reproach, and the fault is found to lie with the execution of the construction.

* Actually, now that I remember, when the load exceeds the building code it doesn't mean it will collapse, the structure just bends slightly more than is allowable by the building code. It really takes a lot to make something actually full on collapse.

[WOM]

Berkeley Disaster

The exact dimensions of the balcony that failed were not released. Estimates varied, with Mayor Tom Bates saying city officials thought it was about 9½ feet by 5 feet, while Grace Kang, a structural engineer and spokeswoman for Pacific Earthquake Engineering Research Center at Berkeley, said it looked to her to be 4 by 6 feet, or 24 square feet.

The larger estimate would mean the balcony should hold 2,850 pounds, while Kang's estimate would be half that. Kang said it appeared small for 13 people.

"They were packed like sardines, and then they were moving," Kang said. When people are moving it "may further exacerbate" the strain.

[Flynnie]

Berkeley Disaster

FWIW, I would take as more credible the estimate from the mayor, who presumably has people providing an estimation based on being on site or plans filed with their office, versus someone who, while also in Berkeley, seems to be making this call off of a photograph.

[anton pulisov]

Berkeley Disaster

The larger estimate would mean the balcony should hold 2,850 pounds, while Kang's estimate would be half that. Kang said it appeared small for 13 people.

They have done 9.5 ft x 5 ft x 60 lb/ft2 there, and come up with 2,850.

But that 2,850 is multiplied by a factor of 1.5 when designing the balcony. Also, the weight of the balcony itself is also multiplied by a factor of 1.2 when designing the balcony. In Europe anyway, but the US is the same, I am sure. Especially California, for obvious reasons.

Engineers take a freakish overestimation of the total weight that could conceivably ever be on the balcony (just to be sure), and multiply that all by another factor (to be sure to be sure) when designing a balcony. And they use all this to make sure that the balcony doesn't sag more than a gradient of 0.4% when this unrealistically massive load is on the balcony. For an engineer, the balcony has failed, not if it has collapsed, but if it sags by a gradient of more than 0.4%, which is barely discernible to the human eye.

Basically, there's no way in hell the students should have been able to overload the balcony design to the point of collapsing. It has to be shoddy construction that has caused the problem.

[WOM]

Berkeley Disaster

I don't mean this aggressively/fighty, but is engineering something you know a whole lot about? Because I don't, but I've never heard the idea that engineers freakishly overestimate everything.

In fact, I've always heard that engineering is knows as 'the science of just good enough'. ie, the point of engineering isn't to build a kitchen chair that could hold a 5,000 pound man, you know...just in case one showed up. It simply doesn't make sense to build a small balcony that could hold an entire football team, bouncing up and down during a once-in-100-years earthquake.

But I'm happy to be corrected.

[anton pulisov]

Berkeley Disaster

I designed a steel aircraft hangar for my Bachelor's thesis. It was never built, of course (thank goodness, because I was a crap engineer and found the whole thing quite boring).

You are a right, of course, that engineers pride themselves in being able to build something to do exactly what it should do, using just the right amount of material... which is why engineers are always arguing with architects who want holes halfway up skyscrapers and protruding floors and what not.

But the engineer is required to conform to the building code. The building code (in Europe anyway) roughly says that a balcony should be able to be loaded by 1.2 times its own weight, plus 1.5 times 250 kg/m2. And with all that weight on it, it shouldn't sag by more than 1/250 of the length it protrudes. So a balcony that sticks out 1 m from a building can't sag by more than 4 mm when it is fully loaded and then some. The engineer's job is to use as little material as possible to conform to that standard.

It might not make sense to have such a strong building code, but then, people don't make sense and can't be predicted. Somebody might decide to put two grand pianos in their bedroom, for example.

Or somebody might decide to re-plaster their kitchen walls, and store all the bags of plaster on their balcony. And then invite their friends over for a barbecue on the balcony.

Worst case scenario, and them some. That's generally how the building code works.

[Flynnie]

Berkeley Disaster

My exceptionally layman's view of California building codes is they are precisely that strict when it comes to making sure stuff doesn't fall down due to earthquakes. I am happy to be corrected.

[ursus arctos]

Berkeley Disaster

Having married into a family of engineers, I'm with Bryan on the way they work.

And I would expect that Berkeley has one of the most stringent building codes in the country, given the combination of a very activist city government, a strong university commitment and the fact that the Hayward Fault runs right through campus.



linus may actually have some first hand knowledge of the code, given his background

[WOM]

Berkeley Disaster

Thanks for the clarification, Bryan.

[anton pulisov]

Berkeley Disaster

Green Calx wrote: The New York Times has published an absolutely appalling article today which attempts to somehow connect this tragedy to stories of other Irish J1 students engaging in pissed-up hijinks in California. I'm not linking to it.

I just read it.

I'm not linking to it either.

[ursus arctos]

Berkeley Disaster

Jeez, the lead author on that hateful piece of crap used to be their national political correspondent (now Los Angeles bureau chief).

The quality of the paper is in free fall.

The Daily Cal has updated its story.

[Janik]

Berkeley Disaster

I'll skip reading it.

To summarise the engineer discussion, an engineer takes a set target and then finds the most efficient and elegant way to achieve it. She doesn't particularly care what the target is, just hits it in the best way possible.

Which is an oversimplification, as engineers often set the target. But from working with them I feel it captures the mindset. Setting the targets doesn't excite particularly, hitting them does.

[WOM]

Berkeley Disaster

Google street view offers a particularly clear and frightening perspective on things. First, it's really fucking high. It's floor four, but not counting ground level. So they fell from five stories up.

Second, those two balconies are the only two on that whole side of the building. It's not one of those buildings rife with balconies, so perhaps engineering them to the highest degree might not have been the first order of business.

[Incandenza]

Berkeley Disaster

The NY Times's public editor (their version of an ombudsman) is Margaret Sullivan, she has written about the article on her blog:

My take: The thrust of the story was insensitive, and the reaction to it understandable. An examination of the building’s structure, rather than the behavior of young people in the J-1 program, would have been a more appropriate focus for a second-day story.

I know that editors and reporters at The Times have heard, and understand, the valid complaints that have been raised. It is not The Times’s policy to take a published story off its website, but they clearly would write and edit the story differently now.

A lot of mealy-mouthed apologies from reporters and editors who approved it, though.

[ursus arctos]

Berkeley Disaster

Unsurprisingly, the NYT has been inundated with complaints about the story

From the Public Editor (who is increasingly the person at the paper I most admire)

My take: The thrust of the story was insensitive, and the reaction to it understandable. An examination of the building’s structure, rather than the behavior of young people in the J-1 program, would have been a more appropriate focus for a second-day story.

I know that editors and reporters at The Times have heard, and understand, the valid complaints that have been raised. It is not The Times’s policy to take a published story off its website, but they clearly would write and edit the story differently now.

[Incandenza]

Berkeley Disaster

Great minds!